Hydrogels have attracted tremendous attention as favorable corneal substitutes for treating severe infectious keratitis (IK). However, current hydrogel-based corneal substitutes were majorly designed to promote the single stage of corneal regeneration, which falls short in meeting the clinical management needs of severe IK including the multiple phases of corneal wound healing. Herein, we introduce a versatile hybrid hydrogel (SQPV) composed of silk fibroin and chitosan, which exhibits spatiotemporal properties for drug release. The SQPV is fabricated by incorporating verteporfin-loaded poly(lactic--glycolic)-polyethylene glycol--nitrobenzene micelles into a hydrogel network, which is formed from methacrylate silk fibroin and glycidyl methacrylate functionalized quaternized chitosan containing polydeoxyribonucleotide. This double network approach results in a material with exceptional anti-inflammatory, antibacterial, and proliferative stimulation and tissue remodeling regulation capabilities. Furthermore, SQPV showcases mechanical strength and transparency akin to those of native cornea. Extensive and studies validate SQPV's ability to effectively eliminate residual bacteria, mitigate inflammation, foster regeneration of corneal epithelium and stroma, prevent corneal scarring, and ultimately expedite wound healing. In summary, the SF/CS-based hybrid hydrogel may represent a promising substitute for comprehensive corneal repair and regeneration in severe IK.

Reactive oxygen species (ROS) scavenging is a viable approach to promote corneal epithelium wound healing. This study created a single-component hydrogel (HA Gel) with a novel dual-functionalized hyaluronic acid derivative (HA-GA-PBA) containing gallol and phenylboronic acid (PBA) moieties. Both of these moieties were dual-functional. Specifically, they not only functioned as structural building blocks for hydrogel formation, but also served as bioactive ingredients for therapeutic purpose. Dynamic covalent complexation between gallol and PBA moieties led to the self-crosslinked HA Gel, which was antioxidative and tissue-adhesive. It was demonstrated that the hydrogel enhanced the proliferation rate of human corneal epithelial cells by over 2.5 folds. When treating the mouse corneal alkali burn model with HA Gel, the corneal epithelial healing percentages reached 69.19 ± 9.41 % and 84.12 ± 6.09 % on day 3 and 5, respectively, which were significantly higher than the placebo group (51.14 ± 9.63 % and 67.32 ± 10.54 % on day 3 and 5, respectively). Meanwhile, reduced scar formation and inflammation was observed. These findings indicated HA Gel could find applications in various of ocular diseases for improved corneal epithelial wound healing.

Diabetic keratopathy, commonly associated with a hyperactive inflammatory response, is one of the most common eye complications of diabetes. The peptide hormone fibroblast growth factor-21 (FGF-21) has been demonstrated to have anti-inflammatory and antioxidant properties. However, whether administration of recombinant human (rh) FGF-21 can potentially regulate diabetic keratopathy is still unknown. Therefore, in this work, we investigated the role of rhFGF-21 in the modulation of corneal epithelial wound healing, the inflammation response, and oxidative stress using type 1 diabetic mice and high glucose-treated human corneal epithelial cells. Our experimental results indicated that the application of rhFGF-21 contributed to the enhancement of epithelial wound healing. This treatment also led to advancements in tear production and reduction in corneal edema. Moreover, there was a notable reduction in the levels of proinflammatory cytokines such as TNF-α, IL-6, IL-1β, MCP-1, IFN-γ, MMP-2, and MMP-9 in both diabetic mouse corneal epithelium and human corneal epithelial cells treated with high glucose. Furthermore, we found rhFGF-21 treatment inhibited reactive oxygen species production and increased levels of anti-inflammatory molecules IL-10 and SOD-1, which suggests that FGF-21 has a protective role in diabetic corneal epithelial healing by increasing the antioxidant capacity and reducing the release of inflammatory mediators and matrix metalloproteinases. Therefore, we propose that administration of FGF-21 may represent a potential treatment for diabetic keratopathy.

The release of growth factors from ischaemic retina has been hypothesized as the central stimulus for retinal neovascularization in proliferative diabetic retinopathy. Two of the growth factors implicated are insulin-like growth factor-I and basic fibroblast growth factor. We examined the effect of insulin-like growth factor-I on in vivo neovascularization using the established angiogenic model of the rabbit cornea (n = 30), and also compared the effects of insulin-like growth factor-I and basic fibroblast growth factor using two new in vivo systems. Either supraphysiologic concentrations of each growth factor (600 micrograms) were injected intravitreally into pigmented rabbits (n = 21) or porous polyfluorotetraethylene chambers filled with an emulsion containing collagen and growth factor (500 ng) were placed on the retina surface (n = 8). Our results demonstrate that when insulin-like growth factor-I was implanted together with a slow release carrier into the pocket of the normally avascular cornea, insulin-like growth factor-I (10 micrograms/pellet) induced angiogenesis in all rabbits. This degree of angiogenesis was comparable to that previously shown for basic fibroblast growth factor. For the intravitreal studies, the fibrotic component was greater in the basic fibroblast growth factor injected eyes, whereas the vascular component was accentuated in the eyes injected with insulin-like growth factor-I. Light and electron microscopy demonstrated areas of vascular proliferation in both groups. Porous polyfluorotetraethylene chamber studies with insulin-like growth factor-I and basic fibroblast growth factor demonstrated vascular proliferation in the vicinity of the chamber similar to the intravitreal injected eyes, but to a lesser degree than the injected eyes. Our experiments overall support the angiogenic potential of both insulin-like growth factor-I and basic fibroblast growth factor and support distinct but complimentary roles for each growth factor in the pathogenesis of proliferative diabetic retinopathy.

We sought to determine the effects of exogenous epidermal growth factor (EGF), heparin-binding EGF (HB-EGF), transforming growth factor alpha (TGF-alpha), single-chain precursor hepatocyte growth factor (SC-HGF), double-chain mature HGF (DC-HGF), and keratinocyte growth factor (KGF) on proliferation, motility, and differentiation of first passage cultures of human corneal epithelial cells in serum-free chemically defined medium. The effect of EGF, HB-EGF, TGF-alpha, SC-HGF, DC-HGF, KGF or combinations of the growth factors on proliferation was measured by counting cells present after 3 weeks of culture and by immunostaining for the cell-cycle-specific nuclear proliferation antigen Ki-67. The effect of the factors on epithelial cell motility was assessed by morphometric analysis of photographs of cells migrating from confluent islands of cells. The effect of growth factors on differentiation of epithelial cells were determined by immunostaining epithelial cell islands for the keratin K3 and by Western blotting for keratin K3. EGF, alone or in combination with KGF and SC-HGF, significantly stimulated motility of epithelial cells at the periphery of confluent islands of cells and induced an elongated cell morphology. TGF-alpha, HB-EGF and DC-HGF produced motility effects similar to EGF. There was diminished proliferation of the migrating cells in response to EGF, HB-EGF, TGF-alpha or DC-HGF, while non-migrating epithelial cells in the center of confluent islands continued to proliferate in response to the growth factors. EGF, HB-EGF, TGF alpha or DC-HGF inhibited expression of the differentiation-related marker keratin K3 in epithelial cells, both at the edge and at the center of the islands. KGF stimulated proliferation of corneal epithelial cells at low density and in confluent islands of cells. KGF did not affect expression of keratin K3 or migration of epithelial cells. SC-HGF had no effect on corneal epithelial cells. These results indicate that the effects of EGF, HB-EGF, TGF-alpha and DC-HGF on corneal epithelial cell proliferation, motility and differentiation vary from those of KGF and SC-HGF. EGF, HB-EGF, TGF-alpha and DC-HGF induced changes in epithelial cell morphology and motility in cells plated at low cell density or in cells located at the edge of a confluent island. Thus, these effects appear to be dependent on the extent of cell-cell contact. The inhibitory effect of EGF, HB-EGF, TGF-alpha or DC-HGF on corneal epithelial cell differentiation, however, is independent of cell density.(ABSTRACT TRUNCATED AT 400 WORDS)

In an effort to improve the regenerative nature of corneal repair, this study reports the use of an in vitro human corneal fibroblasts (HCFs) wound model after treatment with three of the main growth factors (GFs) involved in corneal healing: transforming growth factor beta 1 (TGFβ1), platelet-derived growth factor BB-isoform (PDGF-BB), and basic fibroblast growth factor (bFGF) in order to delve in cell proliferation and differentiation processes. HCFs were mechanically wounded. The individual effect of TGFβ1, PDGF-BB, and bFGF on cell proliferation and differentiation during the repair process was studied at different time points until wound closure. Wound dimensions and morphological changes were evaluated by microscopy. Cell proliferation and myofibroblast differentiation were analyzed by immunofluorescence cytochemistry. Changes in cell morphology were apparent at Day 4. PDGF-BB- and bFGF-treated cells had fibroblast-like morphology. TGFβ1 stimulated proliferation in the wound edge and surrounding area, induced myofibroblast differentiation and inhibited cellular migration. PDGF-BB induced rapid wound closure due to proliferation, high motility, and late myofibroblast differentiation. The time course of closure induced by bFGF was similar to that for PDGF-BB, but was mostly due to proliferation in the wound area, and inhibited myofibroblast differentiation. Each of the GFs induced increases in responses promoting stromal repair differently. This study provides insight regarding how to optimize the outcome of stromal repair following corneal injury.

Corneal injuries are among the major causes of ocular morbidity and vision impairment. Optimal epithelial wound healing is critical for the integrity and transparency of the cornea after injury. Hepatocyte growth factor (HGF) is a mitogen and motility factor that primarily regulates epithelial cell function. Herein, we investigate the effect of HGF on proliferation of corneal epithelial cells (CECs) in inflamed conditions both in vitro and in vivo. We demonstrate that HGF not only promotes CEC proliferation in homeostatic conditions but also reverses the anti-proliferative effect of the inflammatory environment on these cells. Furthermore, using a mouse model of ocular injury, we show that HGF treatment suppresses ocular inflammation and actively augments CEC proliferation, leading to improved and accelerated corneal epithelial repair. These findings have potential translational implications and could provide a framework for the development of novel HGF-based therapies for corneal epithelial defects.

With 1.5-2.0 million new cases annually worldwide, corneal injury represents a common cause of vision loss, often from irreversible scarring due to surface corneal defects. In this study, we assessed the use of hepatocyte growth factor (HGF) loaded into an in situ photopolymerizable transparent gelatin-based hydrogel for the management of corneal defects. In vitro release kinetics showed that, in regard to the total amount of HGF released over a month, 55 ± 11% was released during the first 24 h, followed by a slow release profile for up to one month. The effect of HGF was assessed using an ex vivo model of pig corneal defect. After three days of organ culture, epithelial defects were found to be completely healed for 89% of the corneas treated with HGF, compared to only 11% of the corneas that had fully re-epithelialized when treated with the hydrogel without HGF. The thickness of the epithelial layer was found to be significantly higher for the HGF-treated group compared to the group treated with hydrogel without HGF (p = 0.0012). Finally, histological and immunostaining assessments demonstrated a better stratification and adhesion of the epithelial layer in the presence of HGF. These results suggest that the HGF-loaded hydrogel system represents a promising solution for the treatment of persistent corneal defects at risk of scarring.

The IL-36 cytokines are known to play various roles in mediating the immune and inflammatory response to tissue injury in a context-dependent manner. This study investigated the role of IL-36R signaling in mediating epithelial wound healing in normal (NL) and diabetic (DM) C57BL/6 mouse corneas. The rate of epithelial wound closure was significantly accelerated in IL-36 receptor-deficient (IL-36R) compared to wild-type (WT) mice. Wounding increased IL-36α and -36γ but repressed IL-36R antagonist (IL-36Ra) expression in B6 mouse corneal epithelial cells. The wound-induced proinflammatory cytokines CXCL1 and CXCL2 were dampened, while the antimicrobial peptides (AMPs) S100A8 and A9 were augmented in IL-36R mouse corneas. Intriguingly, the expression of AMP LCN2 was augmented at the mRNA level. LCN2 deficiency resulted in an acceleration of epithelial wound healing. IL-36R deficiency also greatly increased the healing rate of the corneal epithelial wound in DM mice. IL-36R deficiency also suppressed IL-1β, IL-1Ra, and ICAM expression in unwounded-DM mice and wounded NL corneas. Opposing IL-1β and ICAM, the expression of IL-Ra in DM corneas of IL-36R mice was augmented. The presence of recombinant IL-1Ra and IL-36Ra accelerated epithelial wound closure in T1DM corneas of B6 mice. Our study revealed an unprecedented role of IL-36R signaling in controlling corneal epithelial wound healing in normal (NL) and diabetic (DM) mice. Our data suggest that IL-36Ra, similar to IL-1Ra, might be a therapeutic reagent for improving wound healing and reducing wound-associated ulceration, particularly in the cornea and potentially in the skin of DM patients.

Chitosan/poloxamer-based thermosensitive hydrogels containing zinc gluconate/recombinant human epidermal growth factor (ZnG/rhEGF@Chit/Polo) were developed as a convenient, safe and effective dressing for skin wound treatment. Their fabrication procedure and characterization were reported, and their morphology was examined by a scanning electron microscope. Antibacterial and biofilms activities were evaluated by in vitro tests to reveal the inhibitory effects and scavenging activity on the biofilms of Staphylococcus aureus and Pseudomonas aeruginosa. ZnG/rhEGF@Chit/Polo was also investigated as a potential therapeutic agent for wound healing therapy. In vivo wound healing studies on rats for 21 days proves that ZnG/rhEGF@Chit/Polo supplements the requisite Zn and rhEGF for wound healing to promote the vascular remodeling and collagen deposition, facilitate fibrogenesis, and reduce the level of interleukin 6 for wound basement repair, and thus is a good wound therapy.

The proinflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) are involved in the corneal inflammatory response and wound healing following corneal injuries. However, the mechanism by which proinflammatory cytokines modulate corneal epithelial wound healing remains unclear. In this study, we found that IL-1β or TNF-α was transiently elevated during corneal epithelial wound healing in mice. After corneal epithelial debridement, persistent treatment with IL-1β or TNF-α restrained the level of phosphorylated signal transducer and activator of transcription 3 (p-STAT3) and boosted the level of cell cycle inhibitor p16 , resulting in impaired corneal epithelial repair. When p16 was deleted, the p-STAT3 level in corneal epithelium was enhanced and corneal epithelial wound healing was clearly accelerated. In diabetic mice, IL-1β, TNF-α, and p16 appeared a sustained and strong expression in the corneal epithelium, and p16 knockdown partially reverted the defective diabetic corneal epithelial repair. Furthermore, immunoprecipitation proved that p16 interacted with p-STAT3 and thus possibly suppressed the STAT3 activity. Our findings revealed a novel mechanism that the proinflammatory cytokines modulate corneal epithelial wound healing via the p16 -STAT3 signaling.

Diabetic wound is a chronic wound in which normal process of wound healing is interrupted. Lack of blood supply, infection and lack of functional growth factors are assumed as some of the conditions that lead to non-healing environment. Epidermal growth factor (EGF) acts primarily to stimulate epithelial cell growth across wound. Erythropoietin (EPO) is a haematopoietic factor, which stimulates the production, differentiation and maturation of erythroid precursor cells. This study hypothesised combining these two factors, non-healing process of diabetic wound will be compensated and eventually lead to acceleration of wound healing compared with single growth factor treatment. A total of 30 diabetic Sprague-Dawley rats were divided into three treatment groups (single treatment of rh-EPO or rh-EGF or combined treatment on a full-thickness skin wound). To assess the wound healing effects of the components, the wound size and the healing time were measured in each treatment groups. The skin histology was examined by light microscopy and immunohistochemical analysis of proliferating markers was performed. The combined treatment with rh-EPO and rh-EGF improved full-thickness wound significantly (P < 0·05) accelerating 50% healing time with higher expression of Ki-67 compared with single growth factor-treated groups. The combined treatment failed to accelerate the total healing time when compared with single growth factor treatments. However, the significant improvement were found in wound size reduction in the combined treatment group on day 4 against single growth factor-treated groups (P < 0·05). This study demonstrated that the combined treatment of rh-EPO and rh-EGF improved the wound healing possibly through a synergistic action of each growth factor. This application provides further insight into combined growth factor therapy on non-healing diabetic wounds.

The present study was designed to investigate the effect of topical erythropoietin on the healing process of induced necrotizing scleritis and to evaluate the ocular side effects of this treatment modality in a rabbit model. Necrotizing scleritis was induced in 8 New Zealand albino rabbits. The animals were then randomly divided into one of two groups: a treated group administered a topical erythropoietin-containing cellulose-based gel every 8 h or a control group treated with a cellulose-based gel without erythropoietin every 8 h. The sizes of the lesions measured at different time points were compared between the groups. After three months, the rabbits' eyes were enucleated and histologically and immunohistochemically evaluated for angiogenesis and apoptosis. The lesions were completely vascularized in all eyes of the treated group and 50% of eyes of the control group. The mean interval from the induction of scleral necrosis to a complete improvement was 28 days in the treated group and 62.5 days in the control group (P = 0.04). Histological examination revealed that erythropoietin enhanced the improvement of necrotizing scleritis by stimulating angiogenesis and reducing apoptosis. Neovascularization of the cornea, iris, or retina was not observed in the treated group. We observed a significantly faster recovery to complete improvement of necrotizing scleritis in rabbit eyes treated with erythropoietin compared to those of the control group. Treated eyes had a higher rate of complete healing and had no ocular safety concerns. This therapeutic modality represents a promising treatment for scleral necrosis following various types of ocular surgery.

Purpose:Regulation of inflammation is critical for achieving favorable outcomes in wound healing. In this study, we determine the functional role and mechanism of action of IL-11, an immunomodulatory cytokine, in regulating inflammatory response at the ocular surface. Methods:Corneal injury was induced by mechanical removal of the epithelium and anterior stroma using an AlgerBrush II. Transcript and protein levels of IL-11 in injured cornea were quantified using real-time PCR and ELISA analysis. Corneal inflammation was assessed by measuring frequencies of total CD45+ inflammatory cells, CD11b+Ly6G+ polymorphonuclear cells (neutrophils), and CD11b+Ly6G- mononuclear cells (macrophages, monocytes) at the ocular surface using flow cytometry. To assess the effect of IL-11 on innate immune cell function, cell activation marker and inflammatory cytokines including major histocompatibility complex (MHC) class II, myeloperoxidase (MPO), TNFα, and inducible nitric oxide synthase (iNOS) were measured following recombinant IL-11 treatment (1 µg/mL). Injured corneas were topically treated with IL-11 (1 µg/mL), and wound healing was evaluated using corneal fluorescein staining. Results:Corneal injury resulted in increased levels of IL-11 in the cornea, particularly in the stroma. Neutrophils and CD11b+ mononuclear cells (macrophages, monocytes) substantially expressed IL-11 receptor. Interestingly, IL-11 significantly downregulated the activation of immune cells, as evidenced by the lower expression of MHC II and TNFα by CD11b+ mononuclear cells and lower levels of MPO by neutrophils. Topical administration of IL-11 to injured corneas led to faster wound healing and better retention of tissue architecture. Conclusions:Our findings demonstrate IL-11 is a key modulator of ocular surface inflammation and provide novel evidence of IL-11 as a potential therapeutic to control inflammatory damage and accelerate wound repair following injury.

The cornea is continuously exposed to injuries, ranging from minor scratches to deep traumas. An effective healing mechanism is crucial for the cornea to restore its structure and function following major and minor insults. Transforming Growth Factor-Beta (TGF-β), a versatile signaling molecule that coordinates various cell responses, has a central role in corneal wound healing. Upon corneal injury, TGF-β is rapidly released into the extracellular environment, triggering cell migration and proliferation, the differentiation of keratocytes into myofibroblasts, and the initiation of the repair process. TGF-β-mediated processes are essential for wound closure; however, excessive levels of TGF-β can lead to fibrosis and scarring, causing impaired vision. Three primary isoforms of TGF-β exist-TGF-β1, TGF-β2, and TGF-β3. Although TGF-β isoforms share many structural and functional similarities, they present distinct roles in corneal regeneration, which adds an additional layer of complexity to understand the role of TGF-β in corneal wound healing. Further, aberrant TGF-β activity has been linked to various corneal pathologies, such as scarring and Peter's Anomaly. Thus, understanding the molecular and cellular mechanisms by which TGF-β1-3 regulate corneal wound healing will enable the development of potential therapeutic interventions targeting the key molecule in this process. Herein, we summarize the multifaceted roles of TGF-β in corneal wound healing, dissecting its mechanisms of action and interactions with other molecules, and outline its role in corneal pathogenesis.

PURPOSE:Chronic refractory wounds are a multifactorial comorbidity of diabetes mellitus with the characteristic of impaired vascular networks. Currently, there is a lack of effective treatments for such wounds. Various types of mesenchymal stem cell-derived exosomes (MSC-exos) have been shown to exert multiple therapeutic effects on skin regeneration. We aimed to determine whether a constructed combination of human umbilical cord MSC (hUCMSC)-derived exosomes (hUCMSC-exos) and Pluronic F-127 (PF-127) hydrogel could improve wound healing. MATERIALS AND METHODS:We topically applied human umbilical cord-derived MSC (hUCMSC)-derived exosomes (hUCMSC-exos) encapsulated in a thermosensitive PF-127 hydrogel to a full-thickness cutaneous wound in a streptozotocin-induced diabetic rat model. The material properties and wound healing ability of the hydrogel and cellular responses were analyzed. RESULTS:Compared with hUCMSC-exos, PF-127-only or control treatment, the combination of PF-127 and hUCMSC-exos resulted in a significantly accelerated wound closure rate, increased expression of CD31 and Ki67, enhanced regeneration of granulation tissue and upregulated expression of vascular endothelial growth factor (VEGF) and factor transforming growth factor beta-1 (TGFβ-1). CONCLUSION:The efficient delivery of hUCMSC-exos in PF-127 gel and improved exosome ability could promote diabetic wound healing. Thus, this biomaterial-based exosome therapy may represent a new therapeutic approach for cutaneous regeneration of chronic wounds.

Chronic non-healing wounds, frequently caused by diabetes, lead to lower quality of life, infection, and amputation. These wounds have limited treatment options. We have previously engineered growth factors to bind to exposed extracellular matrix (ECM) in the wound environment using the heparin-binding domain of placental growth factor-2 (PlGF-2), which binds promiscuously to ECM proteins. Here, in the type 1 diabetic (T1D) NOD mouse model, engineered growth factors (eGFs) improved both re-epithelialization and granulation tissue formation. eGFs were even more potent in combination, and the "triple therapy" of vascular endothelial growth factor-A (VEGF-PlGF-2), platelet-derived growth factor-BB (PDGF-BB-PlGF-2), and heparin-binding epidermal growth factor (HB-EGF-PlGF-2) both improved wound healing and remained at the site of administration for significantly longer than wild-type growth factors. In addition, we also found that changes in the cellular milieu of a wound, including changing amounts of M1 macrophages, M2 macrophages and effector T cells, are most predictive of wound-healing success in the NOD mouse model. These results suggest that the triple therapy of VEGF-PlGF-2, PDGF-BB-PlGF-2, and HB-EGF-PlGF-2 may be an effective therapy for chronic non-healing wounds in that occur as a complication of diabetes.

PURPOSE:To study the role played by HB-EGF in corneal epithelial wound healing. METHODS:A 2-mm corneal epithelial wound was created in keratinocyte-specific, HB-EGF-deficient mice--HB(lox/lox):K-5Cre (HB(-/-))--and the speed of wound healing was compared with that in wild-type (WT) mice. Cultured confluent mouse corneal epithelial cells (MCECs) from WT and HB(-/-) mice were scraped, and the bare area was measured. The proliferation of MCECs was determined by BrdU incorporation. The degree of attachment of WT and HB(-/-) MCECs was also determined. The mRNA expression of EGF family and cell adhesion molecules was determined by real-time PCR. RESULTS:Corneal epithelial wound healing was significantly delayed in HB(-/-) mice, and the expression of HB-EGF was detected at the leading edge of the wound in HB(lox/+):K5-Cre (HB(+/-)) mice by the presence of lacZ staining. The wound closure was significantly impaired in HB(-/-) MCECs and was improved by adding HB-EGF. The number of BrdU-positive MCECs of WT and HB(-/-) mice was not significantly different, and both increased to different degrees when HB-EGF was added. The adhesion of isolated HB(-/-) MCECs was lower than that of WT MCECs, but the degree of adhesion was restored by adding HB-EGF. The expression of epiregulin was upregulated in HB(-/-) MCECs, and α6- and β1-integrin were upregulated by adding HB-EGF. CONCLUSIONS:HB-EGF plays an important role in corneal epithelial cell healing by enhancing cellular attachment and part of cell proliferation.

Chronic wounds such as diabetic ulcers pose a significant challenge as a number of underlying deficiencies prevent natural healing. In pursuit of a regenerative wound therapy, we developed a heparin-based coacervate delivery system that provides controlled release of heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) within the wound bed. In this study, we used a polygenic type 2 diabetic mouse model to evaluate the capacity of HB-EGF coacervate to overcome the deficiencies of diabetic wound healing. In full-thickness excisional wounds on NONcNZO10 diabetic mice, HB-EGF coacervate enhanced the proliferation and migration of epidermal keratinocytes, leading to accelerated epithelialization. Furthermore, increased collagen deposition within the wound bed led to faster wound contraction and greater wound vascularization. Additionally, in vitro assays demonstrated that HB-EGF released from the coacervate successfully increased migration of diabetic human keratinocytes. The multifunctional role of HB-EGF in the healing process and its enhanced efficacy when delivered by the coacervate make it a promising therapy for diabetic wounds.

Hepatocyte growth factor (HGF) is a glycoprotein produced by mesenchymal cells and operates as a key molecule for tissue generation and renewal. During corneal injury, HGF is primarily secreted by stromal fibroblasts and promotes epithelial wound healing in a paracrine manner. While this mesenchymal-epithelial interaction is well characterized in various organs and the cornea, the role of HGF in corneal stromal and endothelial wound healing is understudied. In addition, HGF has been shown to play an anti-fibrotic role by inhibiting myofibroblast generation and subsequent production of a disorganized extracellular matrix and tissue fibrosis. Therefore, HGF represents a potential therapeutic tool in numerous organs in which myofibroblasts are responsible for tissue scarring. Corneal fibrosis can be a devastating sequela of injury and can result in corneal opacification and retrocorneal membrane formation leading to severe vision loss. In this article, we concisely review the available literature regarding the role of HGF in corneal wound healing. We highlight the influence of HGF on cellular behaviors in each corneal layer. Additionally, we suggest the possibility that HGF may represent a therapeutic tool for interrupting dysregulated corneal repair processes to improve patient outcomes.

Fibroblast growth factors (FGFs) play important roles in many aspects of embryonic development. During eye development, the lens and corneal epithelium are derived from the same surface ectodermal tissue. FGF receptor (FGFR)-signaling is essential for lens cell differentiation and survival, but its role in corneal development has not been fully investigated. In this study, we examined the corneal defects in Fgfr2 conditional knockout mice in which Cre expression is activated at lens induction stage by Pax6 P0 promoter. The cornea in LeCre, Fgfr2(loxP/loxP) mice (referred as Fgfr2(CKO)) was analyzed to assess changes in cell proliferation, differentiation and survival. We found that Fgfr2(CKO) cornea was much thinner in epithelial and stromal layer when compared to WT cornea. At embryonic day 12.5-13.5 (E12.5-13.5) shortly after the lens vesicle detaches from the overlying surface ectoderm, cell proliferation (judged by labeling indices of Ki-67, BrdU and phospho-histone H3) was significantly reduced in corneal epithelium in Fgfr2(CKO) mice. At later stage, cell differentiation markers for corneal epithelium and underlying stromal mesenchyme, keratin-12 and keratocan respectively, were not expressed in Fgfr2(CKO) cornea. Furthermore, Pax6, a transcription factor essential for eye development, was not present in the Fgfr2(CKO) mutant corneal epithelial at E16.5 but was expressed normally at E12.5, suggesting that FGFR2-signaling is required for maintaining Pax6 expression in this tissue. Interestingly, the role of FGFR2 in corneal epithelial development is independent of ERK1/2-signaling. In contrast to the lens, FGFR2 is not required for cell survival in cornea. This study demonstrates for the first time that FGFR2 plays an essential role in controlling cell proliferation and differentiation, and maintaining Pax6 levels in corneal epithelium via ERK-independent pathways during embryonic development.

In this study, we investigated the corneal epithelial cell growth rate and adhesion to novel hydrogels with (1) extracellular matrix proteins [fibronectin, laminin, substance P, and insulin-like growth factor-1 (IGF-1)] and (2) peptide sequences [RGD and fibronectin adhesion-promoting peptide (FAP)] tethered to their surface on poly(ethylene glycol) (PEG) chains. The growth rate to confluence of primary rabbit cornea epithelial cells was compared for plain polymethacrylic acid-co-hydroxyethyl methacrylate (PHEMA/MAA) hydrogels, PHEMA/MAA hydrogels coated with extracellular matrix proteins or peptides, and PHEMA/MAA hydrogels with tethered extracellular matrix proteins or peptides on the surface. The development of focal adhesions by the epithelial cells grown on the surfaces was determined by F-actin staining. Little to no epithelial cell growth occurred on the plain hydrogel surfaces throughout the 15-day culture period. Of the coated hydrogels, only the fibronectin-coated surfaces showed a significant increase in cell growth compared to plain hydrogels (p < 0.009). However, even these surfaces reached a maximum of only 20% confluence. Laminin, fibronectin adhesion-promoting peptide (FAP), and fibronectin/laminin (1:1) tether-modified hydrogels all achieved 100% confluence by the end of the culture period, although the rates at which confluence was reached differed. F-actin staining showed that focal adhesions were formed for the laminin, FAP, and fibronectin/laminin tether-modified surfaces. The results support the hypothesis that tethering certain extracellular matrix proteins and/or peptides to the hydrogel surface enhances epithelial cell growth and adhesion, compared with that seen for protein-coated or plain hydrogel surfaces.