Electrophysiological properties and chemosensitivity of acutely dissociated trigeminal somata innervating the cornea.
Veiga Moreira T H,Gover T D,Weinreich D
Adult rat sensory trigeminal ganglion neurons innervating the cornea (cTGNs) were isolated and identified following retrograde dye labeling with FM1-43. Using standard whole-cell patch clamp recording techniques, cTGNs could be subdivided by their action potential (AP) duration. Fast cTGNs had AP durations <1 ms (40%) while slow cTGNs had AP durations >1 ms and an inflection on the repolarization phase of the AP. With the exception of membrane input resistance, the passive membrane properties of fast cTGNs were different from those of slow cTGNs (capacitance: 61+/-4.5 pF vs. 42+/-2.6 pF, resting membrane potential: -59+/-0.7 mV vs. -53+/-0.9 mV, for fast and slow cTGNs respectively). Active membrane properties also differed between fast and slow cTGNs. Slow cTGNs had a higher AP threshold (-25+/-1.6 mV vs. -38+/-0.8 mV), a larger rheobase (14+/-1.9 pA/pF vs. 6.8+/-1.0 pA/pF), and a smaller AP undershoot (-56+/-1.7 mV vs. -67+/-2.5 mV). The AP overshoot, however was similar between the two types of neurons (46+/-3.1 mV vs. 48+/-4 mV). Slow cTGNs were depolarized by capsaicin (1 microM, 80%) and 60% of their APs were blocked by tetrodotoxin (TTX) (100 nM). Fast cTGNs were unaffected by capsaicin and 100% of their APs were blocked by TTX. Similarly, cTGNs were also heterogeneous with respect to their responses to exogenous ATP and 5-HT. The current work shows that cTGNs have distinctive electrophysiological properties and chemosensitivity profiles. These characteristics may mirror the distinct properties of corneal sensory nerve terminals. The availability of isolated identified cTGNs constitutes a tractable model system to investigate the biophysical and pharmacological properties of corneal sensory nerve terminals.
Experimental use of tetrodotoxin for corneal pain after excimer laser keratectomy.
Schwartz D M,Duncan K G,Duncan J L
PURPOSE:To determine the duration of anesthesia, effect on corneal reepithelialization, and systemic toxicity of topical tetrodotoxin (TTX) administered after excimer laser keratectomy. METHODS:Two groups of six rabbits each underwent excimer laser keratectomy in the right eye to create a 5-mm-diameter wound, 75 mm in depth. One group then received a 40-microl aliquot of topical 1 mM TTX into the injured eye, whereas the other group received 40 microl of the sodium citrate vehicle as a control. The rabbits were treated with TTX or vehicle again at 6, 12, 18, and 24 h. Corneal sensation was tested at 3, 6, 9, 12, 15, 18, 21, 24, 30, 32, and 40 h. To determine whether TTX inhibited corneal reepithelialization, compared with vehicle-treated control eyes, the healing rate of the epithelial defect was measured. RESULTS:Administration of TTX every 6 h for 24 h produced nearly complete anesthesia for > or = 30 h. At 32 h, 8 h after the final application of TTX, there was still significant anesthesia of the TTX-treated corneas (p = 0.0325, Wilcoxon test). Normal corneal sensation in all TTX-treated animals returned at 40 h, or 16 h after the final dose. In contrast, vehicle-treated eyes all had normal sensation for nearly the entire duration of the experiment. At 40 h, the TTX-treated eyes had slightly larger defects than vehicle-treated eyes, 7.85+/-1.74 versus 4.54+/-1.31 mm2 (p < 0.025, t test). However, at 49 h and thereafter, both groups were equally healed (p > 0.05, t test). No systemic toxicity was observed in any of the rabbits. CONCLUSION:Topical TTX is a long-acting and nontoxic local anesthetic in a rabbit model of excimer laser keratectomy.
The Role of Microglia in Retinal Neurodegeneration: Alzheimer's Disease, Parkinson, and Glaucoma.
Ramirez Ana I,de Hoz Rosa,Salobrar-Garcia Elena,Salazar Juan J,Rojas Blanca,Ajoy Daniel,López-Cuenca Inés,Rojas Pilar,Triviño Alberto,Ramírez José M
Frontiers in aging neuroscience
Microglia, the immunocompetent cells of the central nervous system (CNS), act as neuropathology sensors and are neuroprotective under physiological conditions. Microglia react to injury and degeneration with immune-phenotypic and morphological changes, proliferation, migration, and inflammatory cytokine production. An uncontrolled microglial response secondary to sustained CNS damage can put neuronal survival at risk due to excessive inflammation. A neuroinflammatory response is considered among the etiological factors of the major aged-related neurodegenerative diseases of the CNS, and microglial cells are key players in these neurodegenerative lesions. The retina is an extension of the brain and therefore the inflammatory response in the brain can occur in the retina. The brain and retina are affected in several neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and glaucoma. AD is an age-related neurodegeneration of the CNS characterized by neuronal and synaptic loss in the cerebral cortex, resulting in cognitive deficit and dementia. The extracellular deposits of beta-amyloid (Aβ) and intraneuronal accumulations of hyperphosphorylated tau protein (pTau) are the hallmarks of this disease. These deposits are also found in the retina and optic nerve. PD is a neurodegenerative locomotor disorder with the progressive loss of dopaminergic neurons in the substantia nigra. This is accompanied by Lewy body inclusion composed of α-synuclein (α-syn) aggregates. PD also involves retinal dopaminergic cell degeneration. Glaucoma is a multifactorial neurodegenerative disease of the optic nerve, characterized by retinal ganglion cell loss. In this pathology, deposition of Aβ, synuclein, and pTau has also been detected in retina. These neurodegenerative diseases share a common pathogenic mechanism, the neuroinflammation, in which microglia play an important role. Microglial activation has been reported in AD, PD, and glaucoma in relation to protein aggregates and degenerated neurons. The activated microglia can release pro-inflammatory cytokines which can aggravate and propagate neuroinflammation, thereby degenerating neurons and impairing brain as well as retinal function. The aim of the present review is to describe the contribution in retina to microglial-mediated neuroinflammation in AD, PD, and glaucomatous neurodegeneration.
Retinal tau pathology in human glaucomas.
Gupta Neeru,Fong Jessica,Ang Lee C,Yücel Yeni H
Canadian journal of ophthalmology. Journal canadien d'ophtalmologie
BACKGROUND:Tau protein is a microtubule-associated protein critical to neuron structure and integrity. The abnormal hyperphosphorylated tau protein AT8 disrupts microtubules, interferes with axonal transport, and is associated with neuron injury in neurodegenerative diseases such as Alzheimer's disease. The purpose of this study was to assess the presence of tau protein and abnormal tau protein AT8 in human glaucomas and to determine whether abnormal tau protein plays a role in glaucomatous neural degeneration. METHODS:Sections from 11 surgical eye specimens with glaucoma from elevated intraocular pressure causes and 10 age-matched control eye specimens were immunostained for normal tau protein (BT2) and hyperphosphorylated tau protein (AT8). Postmortem specimens with incidental open-angle glaucoma (n = 6) were compared with controls (n = 3). Measurements of immunofluorescence intensity in glaucoma retinas were compared with those in control retinas. Abnormal tau AT8 and parvalbumin, a horizontal cell-specific marker, were studied with double-immunofluorescence techniques to determine colocalization. RESULTS:In surgical glaucoma specimens, normal tau protein was decreased in both the optic nerve and retina compared with age-matched controls. Abnormal tau AT8 was evident within the posterior retina, predominantly at the outer border of the inner nuclear layer in surgical glaucoma specimens, and this was not observed in controls or incidental glaucoma cases. Quantitative immunofluorescence techniques demonstrated significantly increased abnormal tau AT8 in surgical glaucoma specimens compared with controls. Abnormal tau AT8 colocalized with parvalbumin in horizontal cells of the retina. INTERPRETATION:Abnormal tau AT8, a marker of injury in various neurological diseases, is present in human glaucomas with uncontrolled intraocular pressure. The finding of abnormal tau protein in retinal horizontal cells may relate to elevated intraocular pressure and (or) neural degeneration in glaucoma. Tau protein abnormality in glaucoma underscores shared pathways with other neurodegenerative diseases.
Tau overexpression exacerbates neuropathology after repeated mild head impacts in male mice.
Cheng Hank,Deaton Lisa M,Qiu Minhua,Ha Sukwon,Pacoma Reynand,Lao Jianmin,Tolley Valerie,Moran Rita,Keeton Amber,Lamb John R,Fathman John,Walker John R,Schumacher Andrew M
Neurobiology of disease
Repeated mild traumatic brain injury (rmTBI) can lead to development of chronic traumatic encephalopathy (CTE), which is characterized by progressive neurodegeneration with presence of white matter damage, gliosis and hyper-phosphorylated tau. While animal models of rmTBI have been documented, few characterize the molecular pathogenesis and expression profiles of relevant injured brain regions. Additionally, while the usage of transgenic tau mice in rmTBI is prevalent, the effects of tau on pathological outcomes has not been well studied. Here we characterized a 42-impact closed-head rmTBI paradigm on 3-4 month old male C57BL/6 (WT) and Tau-overexpressing mice (Tau58.4). This injury paradigm resulted in chronic gliosis, T-cell infiltration, and demyelination of the optic nerve and associated white matter tracts at 1-month post-injury. At 3-months post-injury, Tau58.4 mice showed progressive neuroinflammation and neurodegeneration in multiple brain regions compared to WT mice. Corresponding to histopathology, RNAseq of the optic nerve tract at 1-month post-injury showed significant upregulation of inflammatory pathways and downregulation of myelin synthetic pathways in both genotypes. However, Tau58.4 mice showed additional changes in neurite development, protein processing, and cell stress. Comparisons with published transcriptomes of human Alzheimer's Disease and CTE revealed common signatures including neuroinflammation and downregulation of protein phosphatases. We next investigated the demyelination and T-cell infiltration phenotypes to determine whether these offer potential avenues for therapeutic intervention. Tau58.4 mice were treated with the histamine H3 receptor antagonist GSK239512 for 1-month post-injury to promote remyelination of white matter lesions. This restored myelin gene expression to sham levels but failed to repair the histopathologic lesions. Likewise, injured T-cell-deficient Rag2/Il2rg (R2G2) mice also showed evidence for inflammation and loss of myelin. However, unlike immune-competent mice, R2G2 mice had altered myeloid cell gene expression and fewer demyelinated lesions. Together this data shows that rmTBI leads to chronic white matter inflammatory demyelination and axonal loss exacerbated by human tau overexpression but suggests that immune-suppression and remyelination alone are insufficient to reverse damage.
Tau Is Involved in Death of Retinal Ganglion Cells of Rats From Optic Nerve Crush.
Oku Hidehiro,Kida Teruyo,Horie Taeko,Taki Koichiro,Mimura Masashi,Kojima Shota,Ikeda Tsunehiko
Investigative ophthalmology & visual science
Purpose:To determine whether tauopathies are associated with impaired autophagy and involved in the death of retinal ganglion cells (RGCs) of rats from an optic nerve crush (ONC). Methods:Short interfering RNA (siRNA) of the tau gene (si-Tau) or nontargeting siRNA (si-NC) was injected intravitreally 48 hours prior to ONC. The effects of silencing the tau gene on neuroprotection were determined by the number of Tuj-1-stained RGCs on days 7 and 14 after the ONC. The changes in the expressions of phosphorylated tau, P62, and LC3B were determined by immunoblots and immunohistochemistry on day 7. Results:Autophagy was impaired in the retina on day 7 after the ONC as the P62 level increased by 3.1-fold from the sham control level with a reduction in the ratio LC3B2/LC3B1. There was a 2.1-fold increase of phosphorylated tau (ser 396) in the retina, and si-Tau depressed the increase by 1.3-fold (n = 3 each). The expressions of tau and P62 were well colocalized. They were observed in the somas of RGCs and retinal nerve fibers (RNFs), and these expressions were increased after the ONC. Pretreatment by si-Tau showed significant protection in the number of RGCs after the ONC. Specifically, the density of RGCs was 540 ± 74.5 cells/mm2 on day 14 in the si-NC group, while the level was maintained at 1321 ± 192 cells/mm2 in the si-Tau group (n = 4 each). Conclusions:Silencing the tau gene is neuroprotective, and tauopathies may be involved in the death of RGCs after ONC. Impaired autophagy may be involved in ONC-induced tauopathies.
Extracellular vesicles derived from human ES-MSCs protect retinal ganglion cells and preserve retinal function in a rodent model of optic nerve injury.
Seyedrazizadeh Seyedeh-Zahra,Poosti Sara,Nazari Abdoreza,Alikhani Mehdi,Shekari Faezeh,Pakdel Farzad,Shahpasand Koorosh,Satarian Leila,Baharvand Hossein
Stem cell research & therapy
BACKGROUND:Retinal and/or optic nerve injury is one of the leading causes of blindness due to retinal ganglion cell (RGC) degeneration. There have been extensive efforts to suppress this neurodegeneration. Various somatic tissue-derived mesenchymal stem cells (MSCs) demonstrated significant neuroprotective and axogenic effects on RGCs. An alternative source of MSCs could be human embryonic stem cells (ES-MSCs), which proliferate faster, express lower levels of inflammatory cytokines, and are capable of immune modulation. It has been demonstrated that MSCs secrete factors or extracellular vesicles that may heal the injury. However, possible therapeutic effects and underlying mechanism of human ES-MSC extracellular vesicles (EVs) on optic nerve injury have not been assessed. METHODS:EVs were isolated from human ES-MSCs. Then, ES-MSC EV was applied to an optic nerve crush (ONC) mouse model. Immunohistofluorescence, retro- and anterograde tracing of RGCs, Western blot, tauopathy in RGCs, and function assessments were performed during 2-month post-treatment to evaluate ONC improvement and underlying mechanism of human ES-MSC EV in in vivo. RESULTS:We found that the ES-MSC EV significantly improved Brn3a+ RGCs survival and retro- and anterograde tracing of RGCs, while preventing retinal nerve fiber layer (RNFL) degenerative thinning compared to the vehicle group. The EVs also significantly promoted GAP43+ axon counts in the optic nerve and improved cognitive visual behavior. Furthermore, cis p-tau, a central mediator of neurodegeneration in the injured RGCs, is detectable after the ONC at the early stages demonstrated tauopathy in RGCs. Notably, after EV treatment cis p-tau was downregulated. CONCLUSIONS:Our findings propose that human ES-MSC EVs, as an off-the-shelf and cell-free product, may have profound clinical implications in treating injured RGCs and degenerative ocular disease. Moreover, the possible mechanisms of human ES-MSC EV are related to the rescue of tauopathy process of RGC degeneration.
Soluble epoxide hydrolase inhibitor, TPPU, increases regulatory T cells pathway in an arthritis model.
Trindade-da-Silva Carlos A,Clemente-Napimoga Juliana T,Abdalla Henrique B,Rosa Sergio Marcolino,Ueira-Vieira Carlos,Morisseau Christophe,Verri Waldiceu A,Montalli Victor Angelo Martins,Hammock Bruce D,Napimoga Marcelo H
FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Epoxyeicosatrienoic acids (EET) and related epoxy fatty acids (EpFA) are endogenous anti-inflammatory compounds, which are converted by the soluble epoxide hydrolase (sEH) to dihydroxylethersatrienoic acids (DHETs) with lessened biological effects. Inhibition of sEH is used as a strategy to increase EET levels leading to lower inflammation. Rheumatoid arthritis is a chronic autoimmune disease that leads to destruction of joint tissues. This pathogenesis involves a complex interplay between the immune system, and environmental factors. Here, we investigate the effects of inhibiting sEH with 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) on a collagen-induced arthritis model. The treatment with TPPU ameliorates hyperalgesia, edema, and decreases the expression of important pro-inflammatory cytokines of Th1 and Th17 profiles, while increasing Treg cells. Considering the challenges to control RA, this study provides robust data supporting that inhibition of the sEH is a promising target to treat arthritis.
Protective effect of Soluble Epoxide Hydrolase Inhibition in Retinal Vasculopathy associated with Polycystic Kidney Disease.
Lin Jihong,Hu Jiong,Schlotterer Andrea,Wang Jing,Kolibabka Matthias,Awwad Khader,Dietrich Nadine,Breitschopf Kristin,Wohlfart Paulus,Kannt Aimo,Lorenz Katrin,Feng Yuxi,Popp Rüdiger,Hoffmann Sigrid,Fleming Ingrid,Hammes Hans Peter
Vasoregression secondary to glial activation develops in various retinal diseases, including retinal degeneration and diabetic retinopathy. Photoreceptor degeneration and subsequent retinal vasoregression, characterized by pericyte loss and acellular capillary formation in the absence diabetes, are also seen in transgenic rats expressing the polycystic kidney disease (PKD) gene. Activated Müller glia contributes to retinal vasodegeneration, at least in part via the expression of the soluble epoxide hydrolase (sEH). Given that an increase in sEH expression triggered vascular destabilization in diabetes, and that vasoregression is similar in diabetic mice and PKD rats, the aim of the present study was to determine whether sEH inhibition could prevent retinal vasoregression in the PKD rat. One-month old male homozygous transgenic PKD rats were randomly allocated to receive vehicle or a sEH inhibitor (sEH-I; Sar5399, 30 mg/kg) for four weeks. Wild-type Sprague-Dawley (SD) littermates received vehicle as controls. Retinal sEH expression and activity were measured by Western blotting and LC-MS, and vasoregression was quantified in retinal digestion preparations. Microglial activation and immune response cytokines were assessed by immunofluorescence and quantitative PCR, respectively. 19,20-dihydroxydocosapentaenoic acid (19,20-DHDP) mediated Notch signaling, microglial activation and migration were assessed and . This study demonstrates that sEH expression and activity were increased in PKD retinae, which led to elevated production of 19,20-DHDP and the depression of Notch signaling. The latter changes elicited pericyte loss and the recruitment of CD11b/CD74 microglia to the perivascular region. Microglial activation increased the expression of immune-response cytokines, and reduced levels of Notch3 and delta-like ligand 4 (Dll4). Treatment with Sar5399 decreased 19,20-DHDP generation and increased Notch3 expression. Sar5399 also prevented vasoregression by reducing pericyte loss and suppressed microglial activation as well as the expression of immune-response cytokines. Mechanistically, the activation of Notch signaling by Dll4 maintained a quiescent microglial cell phenotype, i.e. reduced both the surface presentation of CD74 and microglial migration. In contrast, in retinal explants, 19,20-DHDP and Notch inhibition both promoted CD74 expression and reversed the Dll4-induced decrease in migration. Our data indicate that 19,20-DHDP-induced alterations in Notch-signaling result in microglia activation and pericyte loss and contribute to retinal vasoregression in polycystic kidney disease. Moreover, sEH inhibition can ameliorate vasoregression through reduced activity of inflammatory microglia. sEH inhibition is thus an attractive new therapeutic approach to prevent retinal vasoregression.
An epoxide hydrolase inhibitor reduces neuroinflammation in a mouse model of Alzheimer's disease.
Ghosh Anamitra,Comerota Michele M,Wan Debin,Chen Fading,Propson Nicholas E,Hwang Sung Hee,Hammock Bruce D,Zheng Hui
Science translational medicine
Neuroinflammation has been increasingly recognized to play a critical role in Alzheimer's disease (AD). The epoxy fatty acids (EpFAs) are derivatives of the arachidonic acid metabolism pathway and have anti-inflammatory activities. However, their efficacy is limited because of their rapid hydrolysis by the soluble epoxide hydrolase (sEH). We report that sEH is predominantly expressed in astrocytes and is elevated in postmortem brain tissue from patients with AD and in the 5xFAD β amyloid mouse model of AD. The amount of sEH expressed in AD mouse brains correlated with a reduction in brain EpFA concentrations. Using a specific small-molecule sEH inhibitor, 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), we report that TPPU treatment protected wild-type mice against LPS-induced inflammation in vivo. Long-term administration of TPPU to the 5xFAD mouse model via drinking water reversed microglia and astrocyte reactivity and immune pathway dysregulation. This was associated with reduced β amyloid pathology and improved synaptic integrity and cognitive function on two behavioral tests. TPPU treatment correlated with an increase in EpFA concentrations in the brains of 5xFAD mice, demonstrating brain penetration and target engagement of this small molecule. These findings support further investigation of TPPU as a potential therapeutic agent for the treatment of AD.
The modulatory cholinergic system in goldfish tectum may be necessary for retinotopic sharpening.
Schmidt J T
The cholinergic circuit within the tectum and the cholinergic input from the nucleus isthmi mediate a presynaptic augmentation of retinotectal transmitter release via nicotinic receptors. In this study, the cholinergic systems were either eliminated using the cholinergic neurotoxin AF64A or blocked using nicotinic antagonists to test for effects on the activity-driven sharpening of the regenerating retinotectal projection. The effectiveness of the AF64A was verified by recording field potentials elicited by optic tract stimulation and by immunohistochemical staining for choline acetyltransferase (ChAT). At 1 week after intracranial (IC) injection of AF64A (12 to 144 nmoles) into the fluid above the tectum, field potentials showed a selective dose-dependent decrement of the cholinergic polysynaptic component with no effect on the amplitude of the glutamatergic monosynaptic component. The decrement was only partially recovered in recordings at 2 and 6 weeks. In normal fish, the ChAT antibody stains a population of periventricular neurons, their apical dendrites, and a dense plexus within the optic terminal lamina that consists of their local axons and fine dendrites and of input fibers from the nucleus isthmi. One week after IC AF64A injection (48-72 nmoles), most immunostaining in superficial tectum was lost but most neuronal somas in the deep tectum could still be seen, and staining in the tegmentum below the tectum was completely intact. At 2 weeks and later, the staining of neuronal somata largely recovered, but staining of the superficial plexus did not. AF64A treatment at 18 days after nerve crush, when regenerating retinal fibers are beginning to form synapses, prevented retinotopic sharpening of the projection. Recordings showed a rough retinotopic map on the tectum but the multiunit receptive fields (MURFs) at each tectal point averaged 34 deg vs. 11 deg in vehicle-injected control regenerates. AF64A treatment before nerve crush also blocked sharpening, ruling out a direct effect on retinal growth cones or retinal fibers, as AF64A rapidly decomposes, whereas its effect on the cholinergic fibers is long-lasting. IC injection or minipump infusion of the nicotine antagonists alpha-bungarotoxin (alpha BTX), neuronal bungarotoxin (nBTX), and pancuronium during regeneration also prevented sharpening (MURFs averaging 29.4 deg, 33.0 deg, and 31.4 deg, respectively). Control Ringer's solution infusions or injections over the same period (19-37 days postcrush) had no effect on regenerated MURF size (11.7 deg). The results show that the cholinergic innervation, which modulates transmitter release, is required for activity-driven retinotopic sharpening, thought to be triggered by NMDA receptor activation.
Activation and proliferation of murine microglia are insensitive to glucocorticoids in Wallerian degeneration.
Castaño A,Lawson L J,Fearn S,Perry V H
The European journal of neuroscience
Activation and proliferation of microglia are commonly described in the central nervous system after a wide range of insults, but the mechanisms that regulate their phenotype in vivo are still poorly understood. We have studied the effect that adrenalectomy and dexamethasone treatment have on the proliferation and activation of microglia during Wallerian degeneration of the optic nerve in BALB/c mice. We found that the onset and rate of microglia proliferation is independent of glucocorticoids. There was an increase in F4/80-positive cells 3 days after optic nerve crush, with a peak at 7 days, both in the optic nerve and its target, the superior colliculus. The numbers of F4/80-positive cells remained high up to 3 weeks after crush, the longest time point examined. We also found that up-regulation of F4/80 and the complement receptor type 3 and expression of major histocompatibility complex class II antigens were not affected by adrenalectomy or dexamethasone treatment. These observations show that, unlike microglia in vitro or peripheral macrophages, microglia do not readily respond to glucocorticoids, which could indicate a lack of or reduced expression of glucocorticoid receptor in these cells.
Cholesterol synthesis and nerve regeneration.
Heacock A M,Klinger P D,Seguin E B,Agranoff B W
Journal of neurochemistry
In this report, we examine the requirement of cholesterol biosynthesis and its axonal transport for goldfish optic nerve regeneration. Cholesterol, labeled by intraocular injection of [3H]mevalonolactone, exhibited a delayed appearance in the optic tectum. Squalene and other minor components were labeled but not transported. Following optic nerve crush, the amount of labeled cholesterol transport was elevated, while retinal labeling was not altered relative to control fish. A requirement for cholesterol biosynthesis is inferred from the inhibition of neurite outgrowth in retinal explants caused by the cholesterol synthesis inhibitor, 20,25-diazacholesterol. The inhibition of growth could be overcome by addition of mevalonolactone, but not cholesterol, to the medium. Intraperitoneal administration of 200 nmol of diazacholesterol resulted in 92-98% inhibition of retinal cholesterol synthesis and accumulation of labeled desmosterol and other lipids in fish retina and brain which persisted for 2 weeks. Diazacholesterol-treated fish showed no reduction in the amount of lipid-soluble radioactivity transported following intraocular injection of [3H]mevalonolactone, but there were alterations in the chromatographic pattern of the transported labeled lipids. In contrast to its effects on neurite outgrowth in vitro, diazacholesterol did not inhibit optic nerve regeneration in vivo, as measured both by arrival of labeled rapidly transported protein at the tectum and by time required for the return of visual function.
Daidzein Augments Cholesterol Homeostasis via ApoE to Promote Functional Recovery in Chronic Stroke.
Kim Eunhee,Woo Moon-Sook,Qin Luye,Ma Thong,Beltran Cesar D,Bao Yi,Bailey Jason A,Corbett Dale,Ratan Rajiv R,Lahiri Debomoy K,Cho Sunghee
The Journal of neuroscience : the official journal of the Society for Neuroscience
UNLABELLED:Stroke is the world's leading cause of physiological disability, but there are currently no available agents that can be delivered early after stroke to enhance recovery. Daidzein, a soy isoflavone, is a clinically approved agent that has a neuroprotective effect in vitro, and it promotes axon growth in an animal model of optic nerve crush. The current study investigates the efficacy of daidzein on neuroprotection and functional recovery in a clinically relevant mouse model of stroke recovery. In light of the fact that cholesterols are essential lipid substrates in injury-induced synaptic remodeling, we found that daidzein enhanced the cholesterol homeostasis genetic program, including Lxr and downstream transporters, Apoe, Abca1, and Abcg1 genes in vitro. Daidzein also elevated the cholesterol homeostasis genes in the poststroke brain with Apoe, the highest expressing transporter, but did not affect infarct volume or hemispheric swelling. Despite the absence of neuroprotection, daidzein improved motor/gait function in chronic stroke and elevated synaptophysin expression. However, the daidzein-enhanced functional benefits and synaptophysin expression were abolished in Apoe-knock-out mice, suggesting the importance of daidzein-induced ApoE upregulation in fostering stroke recovery. Dissociation between daidzein-induced functional benefits and the absence of neuroprotection further suggest the presence of nonoverlapping mechanisms underlying recovery processes versus acute pathology. With its known safety in humans, early and chronic use of daidzein aimed at augmenting ApoE may serve as a novel, translatable strategy to promote functional recovery in stroke patients without adverse acute effect. SIGNIFICANCE STATEMENT:There have been recurring translational failures in treatment strategies for stroke. One underlying issue is the disparity in outcome analysis between animal and clinical studies. The former mainly depends on acute infarct size, whereas long-term functional recovery is an important outcome in patients. In an attempt to identify agents that promote functional recovery, we discovered that an FDA-approved soy isoflavone, daidzein, improved stroke-induced behavioral deficits via enhancing cholesterol homeostasis in chronic stroke, and this occurs without causing adverse effects in the acute phase. With its known safety in humans, the study suggests that the early and chronic use of daidzein serves as a potential strategy to promote functional recovery in stroke patients.
Functional regeneration of the visual system in teleosts. Comparative investigations after optic nerve crush and damage of the retina.
Kästner R,Wolburg H
Zeitschrift fur Naturforschung. Section C, Biosciences
Goldfish and carp are shown to be capable of functional reconstitution of the visual system, although their neural retina except of the marginal growth zone at the ora serrata was completely destroyed by injection of the Na-K-ATPase inhibitor ouabain. This was demonstrated by the observation of the recovery of the optokinetic nystagmus after damage of the retina. Recovery of vision coincides well with the morphological reconstitution of the visual system. The regenerated axons within the optic nerve are still unmyelinated at the moment of visual recovery, whereas some fibers within the stratum opticum pars profunda of the corresponding optic tectum are already myelinated. The recovery of vision after regeneration of the retina was compared with the recovery of vision after crush of the optic nerve. The range of time needed for visual recovery was smaller and better reproducible after crush than after damage of the retina.
Neurosteroid allopregnanolone reduces ipsilateral visual cortex potentiation following unilateral optic nerve injury.
Sergeeva Elena G,Espinosa-Garcia Claudia,Atif Fahim,Pardue Machelle T,Stein Donald G
In adult mice with unilateral optic nerve crush injury (ONC), we studied visual response plasticity in the visual cortex following stimulation with sinusoidal grating. We examined visually evoked potentials (VEP) in the primary visual cortex ipsilateral and contralateral to the crushed nerve. We found that unilateral ONC induces enhancement of visual response on the side ipsilateral to the injury that is evoked by visual stimulation to the intact eye. This enhancement was associated with supranormal spatial frequency thresholds in the intact eye when tested using optomotor response. To probe whether injury-induced disinhibition caused the potentiation, we treated animals with the neurosteroid allopregnanolone, a potent agonist of the GABA receptor, one hour after crush and on post-injury days 3, 8, 13, and 18. Allopregnanolone diminished enhancement of the VEP and this effect was associated with the upregulated synthesis of the δ-subunit of the GABA receptor. Our study shows a new aspect of experience-dependent plasticity following unilateral ONC. This hyper-activity in the ipsilateral visual cortex is prevented by upregulation of GABA inhibition with allopregnanolone. Our findings suggest the therapeutic potential of allopregnanolone for modulation of plasticity in certain eye and brain disorders and a possible role for disinhibition in ipsilateral hyper-activity following unilateral ONC.
Intravitreal triamcinolone acetonide, retinal microglia and retinal ganglion cell apoptosis in the optic nerve crush model.
Wang Jiawei,Chen Shida,Zhang Xiulan,Huang Wenbin,Jonas Jost B
PURPOSE:To evaluate the effect of intravitreal triamcinolone acetonide (TA) on the activation of retinal microglia cells (RMGCs) and survival of retinal ganglion cells (RGCs) in an optic nerve crush (ONC) model. METHODS:Adult female Sprague-Dawley rats underwent a standardized ONC and either received an intravitreal injection of TA (TA group) or of phosphate-buffered saline (PBS, PBS group) in the right eyes. At 1, 3, 7, 14 and 28 days after the ONC, the animals were killed. The retinas were examined by immunohistochemistry, light microscopy, Western blot or retrograde labelling of RGCs by fluorogold injected into the superior colliculi. RESULTS:The TA group as compared to the PBS control group showed a significantly (p < 0.0001) lower density of activated RMGCs, at 14 days [4.2 ± 1.6 versus 9.3 ± 2.2 cells/high-power microscopic field (HPF)] and at 28 days (2.3 ± 1.1 versus 4.4 ± 1.5 cells/HPF), and with a significantly lower expression of inflammatory factors. Central density of RGCs as stained by haematoxylin-eosin or by fluorogold was significantly (all p < 0.05) more reduced in the PBS group than in the TA group at days 14 and 28 after baseline. The survival rate (cell density in the study eye as compared to cell density in the contralateral unaffected eye) was significantly higher in the TA group than in the PBS group on days 14 (58% versus 45%; p = 0.003) and 28 (52% versus 41%; p = 0.022). CONCLUSIONS:Intravitreal TA as compared to intravitreal PBS was associated with a lower density of activated RMGCs and a higher density of surviving RGCs in an ONC model.
Dexamethasone and methylprednisolone in treatment of indirect traumatic optic neuropathy.
Kitthaweesin K,Yospaiboon Y
Journal of the Medical Association of Thailand = Chotmaihet thangphaet
A randomized, double blind study was carried out to compare the efficacy of dexamethasone and methylprednisolone in the treatment of indirect traumatic optic neuropathy. Twenty-one patients, 20 male and 1 female, were diagnosed as having suffered from indirect traumatic optic neuropathy. The time from injury to treatment was within 7 days. The average age was 26.38 +/- 11.89 years. The most common cause of injury was motor vehicle accident (MVA). Associated head and maxillofacial injury were reported 43.48 and 34.78 per cent, respectively. Before treatment, no light perception was detected in 19.05 per cent of the participants. Treatments were randomized: ten patients received dexamethasone intravenously for 72 hours and 11 methylprednisolone. The best corrected visual acuities (BCVA) were determined using the Snellen Chart before and 1, 2, 3, 7, 14 and 60 days after treatment. Three or more lines of improvement of the BCVA, were found in 70 and 67 per cent of patients treated with dexamethasone, and 45.45 and 33.33 per cent of patients treated with methylprednisolone, at 2 weeks and 2 months, respectively. There were no significant differences in age, cause of injury, injury to treatment interval, initial BCVA and visual improvement between the two groups.
Hydrocortisone stimulates neurite outgrowth from mouse retinal explants by modulating macroglial activity.
Toops Kimberly A,Berlinicke Cynthia,Zack Donald J,Nickells Robert W
Investigative ophthalmology & visual science
PURPOSE:There is mounting evidence that retinal ganglion cells (RGCs) require a complex milieu of trophic factors to enhance cell survival and axon regeneration after optic nerve injury. The authors' goal was to examine the contribution of components of a combination of hormones, growth factors, steroids, and small molecules to creating a regenerative environment and to determine if any of these components modulated macroglial behavior to aid in regeneration. METHODS:Postnatal day 7 mouse retinal explants embedded in collagen were used as an in vitro model of neurite regeneration. Explants were treated with the culture supplements fetal bovine serum, N2, and G5 and a mixture of G5 and N2 components, designated enhanced N2 (EN2). Explants were evaluated for neurite outgrowth over 7 days in culture. The effects of each treatment were also evaluated on cultured RGCs purified by Thy1 immunopanning. Immunohistochemistry and qPCR analysis were used to evaluate differences in gene expression in the explants due to different treatments. RESULTS:EN2 stimulated significant neurite outgrowth from explants but not from purified RGCs. Elimination of hydrocortisone (HC) from EN2 reduced the mean neurites per explant by 37%. EN2-treated explants demonstrated increased expression of Gfap, Glul, Glt1, Cntf, Pedf, and VegfA compared with explants treated with EN2 without HC. Subsequent experiments showed that increased expression of Cntf and Glul was critical to the trophic effect of HC. CONCLUSIONS:These data suggest that the HC in EN2 indirectly contributed to neurite outgrowth by activating macroglia to produce neurotrophic and neuroprotective molecules.
Lack of protective effect of local administration of triamcinolone or systemic treatment with methylprednisolone against damages caused by optic nerve crush in rats.
Huang Tzu Lun,Chang Chung Hsing,Lin Kung Hung,Sheu Min Muh,Tsai Rong Kung
Experimental eye research
The purpose of the present study was to investigate the effects of administrations of triamcinolone acetonide and systemic methylprednisolone sodium succinate on optic nerves (ON) and retinal ganglion cells (RGC) in a rat model of optic nerve crush. The treated groups either received triamcinolone immediately in the form of two pieces of soaked-gelform surrounding retrobulbar optic nerves (0.5 mg/per gelform) or methylprednisolone via peritoneal injection, and control group received intra-peritoneal injection with phosphate-buffered saline (PBS) after crush experiments. RGC density was counted by retrograde labeling with Fluorogold, and visual function was assessed by flash visual-evoked potentials. Terminal transferase dUTP nick end-labeling (TUNEL) assays, Western blot analysis of serine/threonine kinase (p-Akt), extracellular signal-regulated kinases (p-ERK) and signal transducer and activator of transcription 3 (p-STAT3) and immunohistochemistry of ED1, marker of macrophage/microglia in the optic nerve were conducted. Two and four weeks after optic nerve crush experiments, neither triamcinolone nor methylprednisolone treatment rescued the RGC from death in the central and mid-peripheral retinas compared with those of the corresponding optic nerve-crushed and PBS-treated rats. Visual-evoked potentials measurements showed a prolonged latency of the P(1) wave in all treated groups (triamcinolone-treated: 123 ± 23 ms, methylprednisolone-treated: 133 ± 25 ms and PBS-treated: 151 ± 55 ms) after two weeks. TUNEL assays showed that there was no decrease in apoptotic cells in the RGC layers of both triamcinolone treated and methylprednisolone-treated retinas. Western blot analysis showed that p-AKT, p-ERK and p-Stat3 were not up-regulated in either retina of the triamcinolone or methylprednisolone treated rats. In addition, the number of ED1-positive cells was not attenuated at the lesion sites of the ON in either treatment group. Based upon these results, we conclude that neither retrobulbar administration of triamcinolone nor systemic administration of methylprednisolone has any neuroprotective effects in a rat model of optic nerve crush.
Steroid Treatment of Optic Neuropathies.
Stunkel Leanne,Van Stavern Gregory P
Asia-Pacific journal of ophthalmology (Philadelphia, Pa.)
The etiologies of optic neuropathy include inflammation, ischemia, toxic and metabolic injury, genetic disease, and trauma. There is little controversy over the practice of using steroids in the treatment of optic neuritis--it is well established that intravenous steroid treatment can speed visual recovery but does not alter final visual function. However, there is controversy surrounding the acceptable routes of administration, dosage, and course of treatment. Additionally, the typical patient with optic neuritis is young and otherwise healthy, and thus is likely to tolerate steroids well. In ischemic and traumatic causes of optic neuropathies, the initial injury is not inflammatory, but damage may be compounded by secondary injury due to resultant inflammation and swelling in the confined space of the optic canal. Steroids have been considered as a means of minimizing inflammation and swelling, and thus minimizing the secondary injury that results. However, the use of steroids in traumatic and ischemic optic neuropathies is highly controversial-the evidence for the efficacy of treatment with steroids is insufficient to show that there is significant benefit. Additionally, patients with these conditions are more likely to have comorbidities that make them vulnerable to significant adverse events with the use of steroids. In this article, we attempt to analyze the current state of the literature regarding the use of steroids in the treatment of optic neuropathies, specifically optic neuritis, nonarteritic anterior ischemic optic neuropathy, and traumatic optic neuropathy.
Traumatic optic neuropathy treatment trial (TONTT): open label, phase 3, multicenter, semi-experimental trial.
Kashkouli Mohsen Bahmani,Yousefi Sahar,Nojomi Marzieh,Sanjari Mostafa Soltan,Pakdel Farzad,Entezari Morteza,Etezad-Razavi Mohammad,Razeghinejad Mohammad Reza,Esmaeli Manuchehr,Shafiee Masoud,Bagheri Mansoureh
Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie
PURPOSE:Intravenously administered erythropoietin (EPO) was firstly commenced (phase 1) in patients with indirect traumatic optic neuropathy (TON) by this group in 2011. It was re-tested by another group (phase 2) in 2014. This multicenter clinical trial was designed to compare its effect with intravenous steroid and observation. METHODS:Included were TON patients ≥5 years of age and with trauma-treatment interval of ≤3 weeks. Follow-up visits were set at 1, 2, 3, 7, 14, 30, and at least 90 days after treatment. EPO and methylprednisolone were infused intravenously every day for three consecutive days. Primary outcome measure was change in the best corrected visual acuity (BCVA). Secondary outcomes included change in color vision and relative afferent pupillary defect (RAPD), side effects, and factors affecting the final visual improvement. RESULTS:Out of 120 patients, 100 (EPO: 69, steroid: 15, observation: 16) were finally included. All three groups showed a significant improvement of BCVA which was not significantly different between the groups (adjusted for pretreatment BCVA). Color vision was significantly improved in the EPO group. Late treatment (>3 days) (odds ratio = 2.53) and initial BCVA of NLP (odds ratio = 5.74) significantly worsened visual recovery. No side effect was observed in any group. CONCLUSION:EPO, steroid, and observation showed a significant improvement of BCVA in patients with TON. Initial BCVA of NLP and late treatment (>3 days) were significant risk factors for visual improvement.
Controversies in neuro-ophthalmology: steroid therapy for traumatic optic neuropathy.
Saxena Rohit,Singh Digvijay,Menon Vimla
Indian journal of ophthalmology
BACKGROUND:There is an increase in the incidence of traumatic optic neuropathy (TON) due to increasing urbanization and rapid spurt in the number of motor vehicles on the road. Despite early presentation and ease of diagnosis the visual outcomes in TON are still limited. There is also significant confusion about the timing, dose and efficacy of steroid treatment in its management. PURPOSE:To provide a clinical update of the pros and cons of steroid therapy for TON. DESIGN:The paper is a retrospective review of the currently available literature in the English language indexed in PubMed. METHODS:A PubMed search was conducted by the authors using the following terms: Traumatic optic neuropathy, megadose, steroids, methylprednisolone. Relevant original articles, review articles, and case reports related to the topic of discussion were evaluated and discussed in the paper. RESULTS:There is no prospective randomized control trial evaluating the effect of steroids in TON. There are varying reports on the effect of steroid therapy from significant improvement to no difference compared to observation. CONCLUSION:The decision to give steroids to patients with TON has to be on an individual case to case basis and must involve informed consent from the patient. There are documented advantages and disadvantages of steroid therapy and a prospective, randomized, controlled trial is necessary comparing steroids, surgery and observation before definitive management can be evolved.
In vivo effects of single or combined topical neuroprotective and regenerative agents on degeneration of retinal ganglion cells in rat optic nerve crush model.
Kitamura Yuta,Bikbova Guzel,Baba Takayuki,Yamamoto Shuichi,Oshitari Toshiyuki
To determine the effectiveness of a single or a combination of topical neurotrophic factors (NFs) in protecting retinal ganglion cells (RGCs) in the rat optic nerve crush (ONC) model, the left ONC was performed to induce the death of the RGCs in adult Sprague-Dawley rats. The NFs studied were tauroursodeoxycholic acid (TUDCA), citicoline, neurotrophin-4 (NT-4), combined TUDCA/citicoline (Doublet-1), combined TUDCA/NT-4 (Doublet-2), combined TUDCA/citicoline/NT-4 (Triplet), and PBS. After 2 weeks, the number of RGCs was determined by Brn3a immunostaining. The optic nerves were immunostained for anti-Growth Associated Protein-43(GAP-43) and -200kD neurofilament heavy antibody to study optic nerve regeneration. Two weeks after the ONC, the densities of RGCs in all treated eyes were significantly higher than that of the PBS treated eyes. In the Triplet group, the number of RGC axons after ONC was significantly higher than that in all of the single treatment groups and the number of TUNEL positive cells was significantly reduced and the number of GAP-43 immunopositive axons was significantly greater than those in the PBS group. Neovascularization was observed only in the Doublet-1 group. We conclude that the combination of the three NFs was the most effective way to protect RGCs after the ONC.
The effect of steroids in combination with optic nerve decompression surgery in traumatic optic neuropathy.
Ropposch Thorsten,Steger Bernhard,Meço Cem,Emesz Martin,Reitsamer Herbert,Rasp Gerd,Moser Gerhard
OBJECTIVES/HYPOTHESIS:Traumatic optic neuropathy (TON) is an important cause of severe visual impairment following blunt or penetrating head trauma. Treatment options include steroids, decompression, or both. Studies have failed to show a clear benefit for either steroids or surgery or a combined therapy. This study describes the visual outcome in surgically managed patients with or without steroid treatment. STUDY DESIGN:Retrospective analysis. METHODS:In a retrospective chart review we included patients (n = 42) with TON who were managed with optic nerve decompression surgery with or without steroids. Comparison of initial and final visual acuity was the primary outcome parameter. RESULTS:In 42 consecutive patients, steroids were used in 21 cases (50%). Ten patients received a high-dose systemic regimen of more than 500 mg methylprednisolone initial dose, and 11 patients were treated with a lower dose. The overall visual improvement rate was 33%, no change was noted in 50%, and no outcome data were available in 17%. The visual improvement rate of patients treated with decompression surgery and steroids was lower (29%, 6 of 21) than those treated with surgery alone (53%, 8 of 15). Comparing both groups, additional steroids had no beneficial effect on the visual outcome (P = .97). There was no case with a deterioration of visual function due to therapy. CONCLUSIONS:In patients with traumatic optic neuropathy who were treated with optic nerve decompression surgery, steroids had no beneficial effect on the visual outcome. LEVEL OF EVIDENCE:2c.
Interretinal transduction of injury signals after unilateral optic nerve crush.
Macharadze Tamar,Goldschmidt Jürgen,Marunde Monika,Wanger Tim,Scheich Henning,Zuschratter Werner,Gundelfinger Eckart D,Kreutz Michael R
In this study, we report that partial unilateral optic nerve crush in the rat affects the number of retinal ganglion cells of the contralateral eye still in continuity with the ipsilateral superior colliculus. The reduction in cell number of the uncrossed retinal projection was accompanied by a microglia response and could be prevented by the local intravitreal application of the anti-inflammatory agent dexamethasone. Interestingly, the level of neuronal activity after optic nerve crush as evidenced by thallium autometallography was enhanced in the termination area of the uncrossed projection, the rostro-medial superior colliculus, suggesting that a dying-back mechanism is not involved. We propose that injury signals from the damaged optic nerve and retina are transduced to the unaffected eye.
Delayed optic nerve decompression for indirect optic nerve injury.
Thakar A,Mahapatra A K,Tandon D A
OBJECTIVE:To test the efficacy of delayed optic nerve decompression in traumatic optic nerve injury. STUDY DESIGN:Critical analysis of Proforma-based, prospectively accrued data of all cases with injury to surgery interval of greater than 2 weeks. METHODS:Thirty-five cases with a median injury to surgery interval of 56 days (range, 16-374 d). Surgical decompression was undertaken only in cases that continued to have poor vision after treatment with steroids in conventional doses (1 mg/kg prednisolone). Pre- and postoperative visual acuity measurements were converted to the logMAR scale of visual acuity and the percentage of visual improvement was calculated. RESULTS:Surgery was universally unrewarding in all 9 cases with persistent and complete blindness of greater than 2 weeks and no response to steroid therapy. Of the cases with some residual vision, 20 of 26 cases improved (mean percentage improvement, 41.0 +/- 5.7%). Cases were categorized on the basis of the injury to surgery interval into groups of 2 weeks to 2 months, 2 months to 4 months, and greater than 4 months. No significant difference was demonstrated in the probability or quantum of improvement in these groups (P =.97). CONCLUSIONS:Optic nerve decompression remains useful as a salvage procedure for conventional dose steroid failed cases of traumatic optic neuropathy. In cases that are not completely blind, vision can be improved even when surgery is undertaken a few months after the injury.
Visual Outcome after Treatment with High Dose Intravenous Methylprednisolone in Indirect Traumatic Optic Neuropathy.
Pokharel S,Sherpa D,Shrestha R,Shakya K,Shrestha R,Malla O K,Pradhananga C L,Pokhrel R P,Shrestha P
Journal of Nepal Health Research Council
BACKGROUND:Traumatic optic neuropathy is an acute injury of the optic nerve due to trauma. It is an ocular emergency, requiring early treatment though there is no proven standard treatment protocol for the condition. Various studies have shown improvement in vision after intravenous steroids, but not statistically significant. Studies have revealed even optical decompression surgery is not the ultimate treatment because of no significant improvement of vision. Our study aims to assess visual outcome after high dose (1 gram) of intravenous methylprednisolone in cases with indirect optic neuropathy. METHODS:This was a non-randomized interventional study carried out in Kathmandu Medical College Teaching Hospital from May 1st 2013- June 1st 2014. RESULTS:There were 10 cases with indirect traumatic optic neuropathy included in the study. Four cases received IV methylprednisolone and six cases were observed without steroid treatment. Traumatic optic neuropathy was observed more in males[8 (80%)]with higher number in age group 21-30 years old. The visual recovery after intravenous steroid treatment was rapid and beneficial in cases with vision better than Non Perception of Light (NPL), even in cases presented 4 days after the trauma. CONCLUSIONS:There was rapid and beneficial improvement in visual acuity after high dose of intravenous steroid treatment in cases with indirect traumatic optic neuropathy with vision better than Non Perception of Light (NPL).
Methylprednisolone treatment does not influence axonal regeneration or degeneration following optic nerve injury in the adult rat.
Ohlsson Marcus,Westerlund Ulf,Langmoen Iver A,Svensson Mikael
Journal of neuro-ophthalmology : the official journal of the North American Neuro-Ophthalmology Society
BACKGROUND:Methylprednisolone (MP) is often used to treat optic nerve injury. However, its effects in experimental crush injury have not been extensively evaluated. METHODS:Adult Sprague-Dawley rats were subjected to a standardized optic nerve crush injury. Animals were treated either with 30 mg/kg MP intravenous bolus followed by subcutaneous injections every 6 hours for 48 hours, or with a drug vehicle alone. RESULTS:The injury resulted in a partial loss of neuronal nuclei-labeled retinal neurons and a corresponding degeneration of axons distal to the injury. EDI-labeled macrophages accumulated at the site of lesion, phagocyting FJ-labeled axonal debris. Regenerative fibers expressing growth associated protein-43 were seen proximal to the lesion, but did not traverse the glial scar. Analysis of optic nerve function using visual evoked potentials showed typical signals in intact animals, which were abolished after injury in MP-treated and untreated animals. CONCLUSIONS:We did not detect any effects of MP on retinal cell survival, macrophage activity at the site of injury, axonal degeneration/regeneration, or visual function. These experimental results provide a physiologic underpinning for the lack of efficacy demonstrated in a large trial of MP treatment of clinical optic nerve injury.
Risk Factors Analysis for the Outcome of Indirect Traumatic Optic Neuropathy With Steroid Pulse Therapy.
Lai I-Li,Liao Han-Tsung,Chen Chien-Tzung
Annals of plastic surgery
BACKGROUND:Although recent evidence suggests a controversy effect of steroids in the management of indirect traumatic optic neuropathy (TON), steroid pulse therapy remains one of the reasonable treatments for patients with indirect TON. It is thought that microcirculatory spasms, edema, and nerve cell necrosis can be prevented or reduced by large doses of steroids. The aim of this study is to analyze the predisposing factors for the recovery of patients with indirect TON who were treated with steroid pulse therapy. MATERIALS AND METHODS:In tracing the 2008 to 2014 data from the Trauma Center of Chang Gung Memorial Hospital, 20 consecutive cases of indirect TON were identified retrospectively. Twenty cases showed no light perception (NLP) under initial ophthalmologic examination. They all received steroid pulse therapy with methylprednisolone in IV form after examination by ophthalmologists, and they did not receive optic nerve decompression. The general data, fracture pattern from images, hospital courses, trauma-related data from ER record, and the initial and final visual data from ophthalmologic records are reviewed. The odds ratio (OR) and 95% confidence intervals (CI) are calculated. Fisher exact test is used for 2 variables to test differences between proportions. Nonparametric statistics are applied to compare the mean values of the data. RESULTS:The results show that for female patients (OR, 3.400; 95% CI, 1.628-7.101; P = 0.049), the administration of methylprednisolone in less than 24 hours from the injury (OR, 3.429; 0.297-39.637), lateral force fracture pattern (OR, 3.500; 0.313-39.153), age of 40 years or younger (OR, 2.333; 0.197-27.567), and pure facial trauma (OR, 3.667; 0.273-49.288) are the predisposing factors for improvement of visual acuity. Patients with orbital blowout fractures (OR, 9.800; 95% CI, 0.899-106.845; P = 0.070), initial free extraocular movement (EOM) (OR, 6.667; 0.809-54.597; P = 0.145), initial intraoptic pressure (IOP) greater than 25 mmHg (OR, 8.000; 0.598-106.936), and higher triage grade (OR, 3.000; 0.447-20.153) are at risk of showing no improvement. CONCLUSIONS:From this study, we might suggest to apply steroid pulse therapy on those patients without contraindication, with an incurring injury less than 24 hours previously. Factors such as sex, age, lateral force fracture pattern, and pure facial trauma revealed a better outcome for improvement of visual acuity. Orbital blowout fractures, initial free EOM, initial IOP greater than 25 mmHg, and higher triage grade suggested poor improvement of visual acuity.
Steroids for traumatic optic neuropathy.
Yu-Wai-Man Patrick,Griffiths Philip G
The Cochrane database of systematic reviews
BACKGROUND:Traumatic optic neuropathy (TON) is an important cause of severe visual loss following blunt or penetrating head trauma. Following the initial injury, optic nerve swelling within the optic nerve canal can result in secondary retinal ganglion cell loss. Optic nerve decompression with steroids or surgical interventions or both has therefore been advocated as a means of improving visual prognosis in TON. OBJECTIVES:The aim of this review was to examine the effectiveness and safety of using steroids in TON. SEARCH METHODS:We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2013, Issue 4), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE, (January 1950 to May 2013), EMBASE (January 1980 to May 2013), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to May 2013), Web of Science Conference Proceedings Citation Index- Science (CPCI-S) (January 1990 to May 2013), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (http://clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 21 May 2013. We also searched the reference lists of included studies, other reviews and book chapters on TON to find references to additional trials. The Science Citation Index was used to look for papers that cited the studies included in this review. We did not manually search any journals or conference proceedings. We contacted trial investigators and experts in the field to identify additional published and unpublished studies. SELECTION CRITERIA:We planned to include only randomised controlled trials (RCTs) of TON in which any steroid regime, either on its own or in combination with surgical optic nerve decompression, was compared to surgery alone or no treatment. DATA COLLECTION AND ANALYSIS:Two review authors independently assessed the titles and abstracts identified from the electronic searches. MAIN RESULTS:We included one study that met our selection criteria; a double-masked, placebo-controlled, randomised trial of high dose intravenous steroids in patients with indirect TON diagnosed within seven days of the initial injury. A total of 31 eligible participants were randomised to receive either high dose intravenous steroids (n = 16) or placebo (n = 15), and they were all followed-up for three months. Mean final best corrected visual acuity (BCVA) was 1.78±1.23 Logarithm of the Minimum Angle of Resolution (LogMAR) in the placebo group, and 1.11±1.14 LogMAR in the steroid group. The mean difference in BCVA between the placebo and steroid groups was 0.67 LogMAR (95% confidence interval -1.54 to 0.20), and this difference was not statistically significant (P = 0.13). At three months follow-up, an improvement in BCVA of 0.40 LogMAR occurred in eight eyes (8/15, 53.3%) in the placebo group, and in 11 eyes (11/16, 68.8%) in the treatment group. This difference was not statistically significant (P = 0.38). AUTHORS' CONCLUSIONS:There is a relatively high rate of spontaneous visual recovery in TON and there is no convincing data that steroids provide any additional visual benefit over observation alone. Recent evidence also suggests a possible detrimental effect of steroids in TON and further studies are urgently needed to clarify this important issue. Each case therefore needs to be assessed on an individual basis and proper informed consent is paramount.
Traumatic optic neuropathy and second optic nerve injuries.
Guy William Marshall,Soparkar Charles N S,Alford Eugene L,Patrinely James R,Sami Mirwat S,Parke Robert B
IMPORTANCE:Current controversy about the primary treatment of traumatic optic neuropathy (TON) has anchored on final vision following injury, but, to our knowledge, no study has examined the effect of different treatments on regaining and protecting optic nerve reserve or on the outcome of second optic nerve injuries. OBJECTIVE:To assess vision improvement in patients treated by various methods who have a second incidence of TON. DESIGN, SETTING, AND PARTICIPANTS:Retrospective medical record review of 12 patients with a second TON seen in an 18-year period (mean follow-up, 11.3 months) at a single tertiary care oculoplastic practice. INTERVENTIONS:Observation, high-dose corticosteroids, optic nerve decompression, or high-dose corticosteroids plus optic nerve decompression. MAIN OUTCOMES AND MEASURES:Change in vision on the Snellen eye chart. RESULTS All second TON events involved the same-side optic nerve as initially injured, and with observation alone, corticosteroids, or corticosteroids and partial optic canal decompression, all patients had vision improvement after their initial injury (P = .004). However, following the second optic nerve injury, most patients' vision fell to the pretreatment level of the first injury, and subsequent management of the second injury with corticosteroids and/or optic canal decompression provided little or no vision return (P = .05). In contrast, optic canal decompressions performed for 91 primary TON injuries resulted in 82.4% having some degree of vision improvement. CONCLUSIONS AND RELEVANCE:Patients with TON may have a second optic nerve insult, and vision recovery from the second event may be limited regardless of primary treatment choice.
CNS progenitor cells promote a permissive environment for neurite outgrowth via a matrix metalloproteinase-2-dependent mechanism.
Zhang Yiqin,Klassen Henry J,Tucker Budd A,Perez Maria-Thereza R,Young Michael J
The Journal of neuroscience : the official journal of the Society for Neuroscience
Transplantation of progenitor cells to the CNS has shown promise in neuronal and glial replacement and as a means of rescuing host neurons from apoptosis. Here we examined the effect of progenitor grafts on neurite extension in the degenerating retina of rd1 (retinal degeneration 1) mice. Transplantation of retinal progenitor cells induced increased matrix metalloproteinase-2 (MMP2) secretion, partly from activated glial cells, which was then activated by neuronally expressed MMP14. Active MMP2 resulted in proteolysis of the neurite outgrowth inhibitors CD44 and neurocan in the degenerative retina, allowing significantly increased neurite outgrowth across the border between abutting nondystrophic and rd1 retinas. Progenitor-induced enhancement of outgrowth was abrogated by an MMP inhibitor or by coculture with retinal explants from MMP2-/- mice. This study provides the first identification of an MMP2-dependent mechanism by which exogenous progenitor cells alter the host environment to promote neural regeneration. This suggests a novel therapeutic role for progenitor cells in the treatment of CNS degenerative diseases.
Proteoglycans in retina.
Inatani Masaru,Tanihara Hidenobu
Progress in retinal and eye research
In this article, we summarize the roles of proteoglycans in retinal tissue. Chondroitin sulfate and heparan sulfate proteoglycans are the major constituents in proteoglycans expressed in retinal tissue. Soluble heparan sulfate proteoglycans are found in the extracellular matrices of the basement membrane, such as the inner limiting membrane and Bruch's membrane, whereas heparan sulfate proteoglycans with their membrane-binding domain are localized primarily in the neurites of retinal neuronal cells, indicating their role as receptors for cytokines. The distribution of chondroitin sulfate proteoglycans is classified into two regions: nerve fiber-rich layers such as the optic nerve, inner plexiform layer and outer plexiform layer, and the interphotoreceptor matrix (IPM). The expression in the nerve fiber-rich layers of several chondroitin sulfate proteoglycans, such as neurocan and phosphacan, is restricted in the nervous tissues, and is upregulated as retinal development proceeds, then decreases after maturation of the retina. In vitro data suggest that these proteoglycans regulate axon guidance and synapse formation during the development of nervous tissue. In contrast, in adult vertebrate retina, the IPM is a rich source of chondroitin sulfate proteoglycans. Histologic data from animals with experimental retinitis pigmentosa, and the existence of the hyaluronan-binding domain in their core proteins, indicate that these proteoglycans contribute to the structural link between the neural retina and retinal pigment epithelium via the interaction with hyaluronan, which is also abundant in the IPM. Furthermore, several chondroitin sulfate proteoglycans in the nerve fiber-rich layers contain the hyaluronan-binding domain, so it is likely that the interaction of proteoglycans with hyaluronan plays an important role in neural network formation in the central nervous system.
Coordinate regulation of cadherin and integrin function by the chondroitin sulfate proteoglycan neurocan.
Li H,Leung T C,Hoffman S,Balsamo J,Lilien J
The Journal of cell biology
N-cadherin and beta1-integrins play decisive roles in morphogenesis and neurite extension and are often present on the same cell. Therefore, the function of these two types of adhesion systems must be coordinated in time and space to achieve the appropriate cell and tissue organization. We now show that interaction of the chondroitin sulfate proteoglycan neurocan with its GalNAcPTase receptor coordinately inhibits both N-cadherin- and beta1-integrin-mediated adhesion and neurite outgrowth. Furthermore, the inhibitory activity is localized to an NH(2)-terminal fragment of neurocan containing an Ig loop and an HA-binding domain. The effect of neurocan on beta1-integrin function is dependent on a signal originating from the cadherin cytoplasmic domain, possibly mediated by the nonreceptor protein tyrosine kinase Fer, indicating that cadherin and integrin engage in direct cross-talk. In the developing chick, neural retina neurocan is present in the inner plexiform layer from day 7 on, and the GalNAcPTase receptor becomes restricted to the inner nuclear layer and the ganglion cell layer (as well as the fiber layer), the two forming a sandwich. These data suggest that the coordinate inhibition of cadherin and integrin function on interaction of neurocan with its receptor may prevent cell and neurite migration across boundaries.
Integration between abutting retinas: role of glial structures and associated molecules at the interface.
Zhang Yiqin,Kardaszewska Agnieszka K,van Veen Theo,Rauch Uwe,Perez Maria-Thereza R
Investigative ophthalmology & visual science
PURPOSE:Integration between subretinal grafts and the host retina is limited in part by the presence of a barrier at the graft-host interface. This study was conducted to identify factors that may contribute to this barrier, by examining the distribution of glial structures and associated molecules in different setups of overlapping retinal pieces. METHODS:Neuroretinal tissue derived from mice that express green fluorescent protein (GFP) was fragmented and transplanted into the subretinal space of adult rd1 mice. In an in vitro system, two retinal pieces, derived from GFP and rd1 mice, respectively, were placed overlapping each other and forming either laminar-laminar pairs or fragment-laminar pairs. The glia-associated markers analyzed included glial fibrillary acidic protein (GFAP), cellular retinaldehyde-binding protein (CRALBP), and two molecules known to inhibit neurite outgrowth: CD44 and neurocan. Bridging fibers and migrated cells were visualized with GFP fluorescence and retinal cell markers. RESULTS:A thick CRALBP-immunolabeled band was observed in the interface in cultured laminar-laminar pairs, whereas a thinner band was seen in cultured fragment-laminar pairs and in transplants. Accumulation of CD44 and neurocan was also observed in the interface between abutting retinal pieces in all setups. GFP(+) bridging fibers and GFP(+) cells (some of which coexpressed neuronal markers) were observed within the abutting rd1 retina in some areas. However, such integration occurred exclusively where CRALBP, CD44, and neurocan immunolabeling appeared disrupted in the interface, but coincided with high GFAP expression within the rd1 retina. CONCLUSIONS:The results demonstrate that, on the one hand, an accumulation of glial-associated inhibitory molecules in the interface correlates with limited integration between overlapping retinal pieces. On the other hand, glial reactivity within the rd1 retina does not appear to be incompatible with integration.
Interleukin-6 contributes to CNS axon regeneration upon inflammatory stimulation.
Leibinger M,Müller A,Gobrecht P,Diekmann H,Andreadaki A,Fischer D
Cell death & disease
Mature retinal ganglion cells (RGCs) do not normally regenerate injured axons and undergo apoptosis after axotomy. Inflammatory stimulation (IS) in the eye mediates neuroprotection and induces axon regeneration into the injured optic nerve. Ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF) have been identified as key mediators of these effects. Here, we investigated the role of interleukin-6 (IL-6), another member of the glycoprotein 130-activating cytokine family, as additional contributing factor. Expression of IL-6 was markedly induced in the retina upon optic nerve injury and IS, and mature RGCs expressed the IL-6 receptor. Treatment of cultured RGCs with IL-6 or specific IL-6 receptor agonist, significantly increased neurite outgrowth janus kinase/signal transducers and activators of transcription-3 (JAK/STAT3) and phosphatidylinositide 3-kinase/protein kinase B (PI3K/Akt) dependently. Moreover, IL-6 reduced myelin, but not neurocan-mediated growth inhibition mammalian target of rapamycin (mTOR) dependently in cultured RGCs. In vivo, intravitreal application of IL-6 transformed RGCs into a regenerative state, enabling axon regeneration beyond the lesion site of the optic nerve. On the other hand, genetic ablation of IL-6 in mice significantly reduced IS-mediated myelin disinhibition and axon regeneration in the optic nerve. Therefore, IL-6 contributes to the beneficial effects of IS and its disinhibitory effect adds an important feature to the effects of so far identified IS-mediating factors. Consequently, application of IL-6 or activation of its receptor might provide suitable strategies for enhancing optic nerve regeneration.
Neuroprotective Effects of Human Mesenchymal Stem Cells and Platelet-Derived Growth Factor on Human Retinal Ganglion Cells.
Osborne Andrew,Sanderson Julie,Martin Keith R
Stem cells (Dayton, Ohio)
Optic neuropathies such as glaucoma occur when retinal ganglion cells (RGCs) in the eye are injured. Strong evidence suggests mesenchymal stem cells (MSCs) could be a potential therapy to protect RGCs; however, little is known regarding their effect on the human retina. We, therefore, investigated if human MSCs (hMSCs), or platelet-derived growth factor (PDGF) as produced by hMSC, could delay RGC death in a human retinal explant model of optic nerve injury. Our results showed hMSCs and the secreted growth factor PDGF-AB could substantially reduce human RGC loss and apoptosis following axotomy. The neuroprotective pathways AKT, ERK, and STAT3 were activated in the retina shortly after treatments with labeling seen in the RGC layer. A dose dependent protective effect of PDGF-AB was observed in human retinal explants but protection was not as substantial as that achieved by culturing hMSCs on the retina surface which resulted in RGC cell counts similar to those immediately post dissection. These results demonstrate that hMSCs and PDGF have strong neuroprotective action on human RGCs and may offer a translatable, therapeutic strategy to reduce degenerative visual loss. Stem Cells 2018;36:65-78.
The use of mesenchymal stem cells for the treatment of progressive retinal diseases: a review.
Borkowska-Kuczkowska Agnieszka,Sługocka Dominika,Świątkowska-Flis Beata,Boruczkowski Dariusz
Some ocular diseases, such as dystrophies, retinal and macular degeneration, optic nerve atrophy, and Stargardt disease, are progressive and irreversible. In this review, we focus on the use of mesenchymal stem cells (MSCs) in the treatment of these diseases. In animal studies, MSC transplantation significantly delayed retinal degeneration, led to the regeneration of cone cells, and supported the survival of retinal ganglion cells and axon regeneration. In clinical practice, patients with Behcet's disease with retinal vasculitis who received MSC injections experienced a decrease in retinal vasculitis but no improvement in vision acuity. Nonetheless, there is no evidence that MSCs are carcinogenic, and they even reduce the size of tumors . Furthermore, MSCs do not trigger the immune response.
Molecular Mechanisms Mediating Retinal Reactive Gliosis Following Bone Marrow Mesenchymal Stem Cell Transplantation.
Tassoni Alessia,Gutteridge Alex,Barber Amanda C,Osborne Andrew,Martin Keith R
Stem cells (Dayton, Ohio)
A variety of diseases lead to degeneration of retinal ganglion cells (RGCs) and their axons within the optic nerve resulting in loss of visual function. Although current therapies may delay RGC loss, they do not restore visual function or completely halt disease progression. Regenerative medicine has recently focused on stem cell therapy for both neuroprotective and regenerative purposes. However, significant problems remain to be addressed, such as the long-term impact of reactive gliosis occurring in the host retina in response to transplanted stem cells. The aim of this work was to investigate retinal glial responses to intravitreally transplanted bone marrow mesenchymal stem cells (BM-MSCs) to help identify factors able to modulate graft-induced reactive gliosis. We found in vivo that intravitreal BM-MSC transplantation is associated with gliosis-mediated retinal folding, upregulation of intermediate filaments, and recruitment of macrophages. These responses were accompanied by significant JAK/STAT3 and MAPK (ERK1/2 and JNK) cascade activation in retinal Muller glia. Lipocalin-2 (Lcn-2) was identified as a potential new indicator of graft-induced reactive gliosis. Pharmacological inhibition of STAT3 in BM-MSC cocultured retinal explants successfully reduced glial fibrillary acidic protein expression in retinal Muller glia and increased BM-MSC retinal engraftment. Inhibition of stem cell-induced reactive gliosis is critical for successful transplantation-based strategies for neuroprotection, replacement, and regeneration of the optic nerve.