Assessments of non-surgical office-based aesthetic treatments' efficacy including lasers are mostly based on subjective evaluation of clinical photography. Accumulating evidence suggest that non-invasive skin imaging such as optical coherence tomography (OCT) can be effectively used to assess not only the skin surface but also the underlying epidermis and dermis, providing objective and clinically relevant data. In this review, we highlight the potential of OCT imaging for the aesthetic medicine field along with OCT measurement parameters and their clinical relevance to healthy and pathological skin conditions. Lasers Surg. Med. © 2020 Wiley Periodicals, Inc.

Supersonic shear imaging is a non-invasive technique used for detecting physiologic and pathologic changes in biological tissues. In this study, supersonic shear imaging was used to measure and compare shear wave speed (c) and normalized elastic modulus (E) values of skin with and skin without dermal striae (DS) in vivo. The values were measured at angles of 0°, 45°, 90° and 315° to the skin tension lines. In the presence of DS, a statistically significant reduction in the elasticity dermis was observed (p value <0.05). The mean values of c and E for STLs were higher in normal skin at 45° (4.26 ± 1.05 m/s and 56.23 ± 25.31 kPa) and 90° (4.26 ± 0.55 m/s and 54.91 ± 14.22 kPa), and those for DS were also higher at 45° (3.59 ± 0.72 m/s and 42.71 ± 27.97 kPa) and 90° (3.52 ± 0.65 m/s and 42.34 ± 31.68 kPa) than at other angles. Supersonic shear imaging was found to be a promising technique in the study of skin with DS. The data obtained in this study are expected to be relevant for future studies using shear wave elastography for the aforementioned purpose.

Although nude mice are an ideal photoaging research model, skin biopsies result in inflammation and are rarely performed at baseline. Meanwhile, studies on antiphotoaging antioxidants or rejuvenation techniques often neglect the spontaneous reversal capacity. Full-field optical coherence tomography (FFOCT) can acquire cellular details noninvasively. This study aimed to establish a photoaging and sequential function reversal nude mice model assisted by an in vivo cellular resolution FFOCT system. We investigated whether a picosecond alexandrite laser (PAL) with a diffractive lens array (DLA) accelerated the reversal. In the sequential noninvasive assessment using FFOCT, a spectrophotometer, and DermaLab Combo®, the photodamage percentage recovery plot demonstrated the spontaneous recovery capacity of the affected skin by UVB-induced transepidermal water loss and UVA-induced epidermis thickening. A PAL with DLA not only accelerated skin barrier regeneration with epidermal polarity, but also increased dermal neocollagenesis, whereas the nonlasered group still had >60% collagen intensity loss and 40% erythema from photodamage. Our study demonstrated that FFOCT images accurately resemble the living tissue. The photoaging and sequential function reversal model provides a reference to assess the spontaneous recovery capacity of nude mice from photodamage. This model can be utilized to evaluate the sequential noninvasive photodamage and reversal effects after other interventions.

Surgery is the definitive treatment for burn patients who sustain full-thickness burn injuries. Visual assessment of burn depth is made by the clinician early after injury but is accurate only up to 70% of the time among experienced surgeons. Collagen undergoes denaturation as a result of thermal injury; however, the association of collagen denaturation and cellular death in response to thermal injury is unknown. While gene expression assays and histologic staining allow for ex vivo identification of collagen changes, these methods do not provide spatial or integrity information in vivo. Thermal effects on collagen and the role of collagen in wound repair have been understudied in human burn models due to a lack of methods to visualize both intact and denatured collagen. Hence, there is a critical need for a clinically applicable method to discriminate between damaged and intact collagen fibers in tissues. We present two complementary candidate methods for visualization of collagen structure in three dimensions. Second harmonic generation imaging offers a label-free, high-resolution method to identify intact collagen. Simultaneously, a fluorophore-tagged collagen-mimetic peptide can detect damaged collagen. Together, these methods enable the characterization of collagen damage in human skin biopsies from burn patients, as well as ex vivo thermally injured human skin samples. These combined methods could enhance the understanding of the role of collagen in human wound healing after thermal injury and potentially assist in clinical decision-making.

The skin is a vital organ for life and, among its many functions, the role as a protective barrier is one of the most important. It is the main boundary between the body and the external environment. As defensive barrier, the epidermis protects internal organs from physical and chemical trauma, microorganism invasion, and ultraviolet radiation. It also acts in the regulation of transepidermal movement of water and electrolytes, and in preventing dehydration, all of which are essential for sustaining life. The main role is allotted to the stratum corneum and to the lipid matrix located in the intercellular space. The occurrence of dysfunction in the epidermal barrier is an important factor in the physiopathogenesis of skin diseases, particularly atopic dermatitis and psoriasis. There are few, but important, systemic changes that influence or are influenced by dysfunctions in the epidermal barrier. We review the effects of some systemic diseases on the maintenance of the skin's homeostasis.

The development of mathematical models for describing the thermal behavior of living tissues under normal or hyperthermia conditions is of increasing importance. In this research, a 3D forearm model based on anthropometric measurement of 25 samples in Tehran, Iran was developed. The tissue temperature distribution is obtained via the Finite Volume Method (FVM) by considering the appropriate boundary conditions, blood perfusion, body metabolism, and the application of hyperthermia conditions on the tissue. The Pennes Bioheat Transfer Equation (PBHTE) is considered in this regard. Also, various thermophysical properties are assumed for the model in order to clarify the effects of such parameters on the tissue temperature distribution. The results of this study indicate that it is possible to provide the desired conditions for many therapeutic processes by controlling the parameters such as blood perfusion, body metabolism and the type of external heat source applied on the tissue. Generally, by decreasing the body metabolism, increasing the blood perfusion rate in tissue and applying a fluctuating heat flux, instead of uniform heat flux on the surface of the forearm skin, it is possible to provide the hyperthermia conditions without causing damages such as burn injuries to the other parts of the tissue. By using the results of this study, the appropriate conditions of hyperthermia can be obtained.

The skin is the largest organ of the body, at the boundary with the outside environment. Primarily, it provides a physical and chemical barrier against external insults, but it can act also as immune organ because it contains a whole host of immune-competent cells of both the innate and the adaptive immune systems, which cooperate in eliminating invading pathogens following tissue injury. On the other hand, improper skin immune responses lead to autoimmune skin diseases (AISD), such as pemphigus, bullous pemphigoid, vitiligo, and alopecia. Although the interplay among genetic, epigenetic, and environmental factors has been shown to play a major role in AISD etiology and progression, the molecular mechanisms underlying disease development are far from being fully elucidated. In this context, epidemiological studies aimed at defining the association of different AISD with other autoimmune pathologies revealed possible shared molecular mechanism(s) responsible for disease progression. In particular, over the last decades, a number of reports have highlighted a significant association between thyroid diseases (TD), mainly autoimmune ones (AITD), and AISD. Here, we will recapitulate the epidemiology, clinical manifestations, and pathogenesis of the main AISD, and we will summarize the epidemiological evidence showing the associations with TD as well as possible molecular mechanism(s) underlying TD and AISD pathological manifestations.