The Current Status and Future Direction of Extracellular Nano-vesicles in the Alleviation of Skin Disorders

Exosomes are extracellular vesicles (EVs) that originate from endocytic membranes. The transfer of biomolecules and biological compounds such as enzymes, proteins, RNA, lipids, and cellular waste disposal through exosomes plays an essential function in cell-cell communication and regulation of pathological and physiological processes in skin disease. The skin is one of the vital organs that makes up about 8% of the total body mass. This organ consists of three layers, epidermis, dermis, and hypodermis that cover the outer surface of the body. Heterogeneity and endogeneity of exosomes is an advantage that distinguishes them from nanoparticles and liposomes and leads to their widespread usage in the remedy of dermal diseases. The biocompatible nature of these extracellular vesicles has attracted the attention of many health researchers. In this review article, we will first discuss the biogenesis of exosomes, their contents, separation methods, and the advantages and disadvantages of exosomes. Then we will highlight recent developments related to the therapeutic applications of exosomes in the treatment of common skin disorders like atopic dermatitis, alopecia, epidermolysis bullosa, keloid, melanoma, psoriasis, and systemic sclerosis.

Merkel-like basal cells in the nasal septal island of dromedaries: Ultrastructure and possible functions

Unlike other Merkel cell types, the morphology and functions of the Merkel-like basal cells remain unclear. The aim of the present study was to investigate the ultrastructural features of Merkel-like basal cells in the nasal septal island (NSI) of dromedaries (Camelus dromedarius) using transmission electron microscopy and to speculate their potential functions. Ten pairs of nasal septal islands obtained from ten heads of dromedary camels were used for the current study. Interestingly, these cells have been identified in the basal layer of the neuroepithelium of the dromedary nasal septal island near the sensory nerve endings. These cells were ovoid to elliptical in shape and rested on the basal lamina. Their surface had spine like cytoplasmic processes which interwined with the adjacent basal cells. Their nuclei were large lobulated with 2-3 deep notches. Moreover, numerous dense-core granules surrounded by electron-lucent halo were aggregated in the basal portion of the cells close to the nerve ending as well as melanin pigments in the apical portion. The ultrastructural characteristics of the Merkel-like basal cells of NSI were typical to those of Merkel cells, but with some morphological differences, including their location, cellular attachments, and connections to other structures. The potential functions were discussed in the light of the cellular context and architecture. The Merkel-like basal cells of the NSI neuroepithelium might play a role in nociception and magnetoreception in dromedaries.

Overcome the barriers of the skin: exosome therapy

Exosomes are nano-sized cargos with a lipid bilayer structure carrying diverse biomolecules including lipids, proteins, and nucleic acids. These small vesicles are secreted by most types of cells to communicate with each other. Since exosomes circulate through bodily fluids, they can transfer information not only to local cells but also to remote cells. Therefore, exosomes are considered potential biomarkers for various treatments. Recently, studies have shown the efficacy of exosomes in skin defects such as aging, atopic dermatitis, and wounds. Also, exosomes are being studied to be used as ingredients in commercialized skin treatment products. In this review, we discussed the need for exosomes in skin therapy together with the current challenges. Moreover, the functional roles of exosomes in terms of skin treatment and regeneration are overviewed. Finally, we highlighted the major limitations and the future perspective in exosome engineering.

Epigenetic regulation and signalling pathways in Merkel cell development

Merkel cells are specialized epithelial cells connected to afferent nerve endings responsible for light-touch sensations, formed at specific locations in touch-sensitive regions of the mammalian skin. Although Merkel cells are descendants of the epidermal lineage, little is known about the mechanisms responsible for the development of these unique mechanosensory cells. Recent studies have highlighted that the Polycomb group (PcG) of proteins play a significant role in spatiotemporal regulation of Merkel cell formation. In addition, several of the major signalling pathways involved in skin development have been shown to regulate Merkel cell development as well. Here, we summarize the current understandings of the role of developmental regulators in Merkel cell formation, including the interplay between the epigenetic machinery and key signalling pathways, and the lineage-specific transcription factors involved in the regulation of Merkel cell development.

Modelling the effects of age-related morphological and mechanical skin changes on the stimulation of tactile mechanoreceptors

Our sense of fine touch deteriorates as we age, a phenomenon typically associated with neurological changes to the skin. However, geometric and material changes to the skin may also play an important role on tactile perception and have not been studied in detail. Here, a finite element model is utilised to assess the extent to which age-related structural changes to the skin influence the tactile stimuli experienced by the mechanoreceptors. A numerical, hyperelastic, four-layered skin model was developed to simulate sliding of the finger against a rigid surface. The strain, deviatoric stress and strain energy density were recorded at the sites of the Merkel and Meissner receptors, whilst parameters of the model were systematically varied to simulate age-related geometric and material skin changes. The simulations comprise changes in skin layer stiffness, flattening of the dermal-epidermal junction and thinning of the dermis. It was found that the stiffness of the skin layers has a substantial effect on the stimulus magnitudes recorded at mechanoreceptors. Additionally, reducing the thickness of the dermis has a substantial effect on the Merkel disc whilst the Meissner corpuscle is particularly affected by flattening of the dermal epidermal junction. In order to represent aged skin, a model comprising a combination of ageing manifestations revealed a decrease in stimulus magnitudes at both mechanoreceptor sites. The result from the combined model differed from the sum of effects of the individually tested ageing manifestations, indicating that the individual effects of ageing cannot be linearly superimposed. Each manifestation of ageing results in a decreased stimulation intensity at the Meissner Corpuscle site, suggesting that ageing reduces the proportion of stimuli meeting the receptor amplitude detection threshold. This model therefore offers an additional biomechanical explanation for tactile perceptive degradation amongst the elderly. Applications of the developed model are in the evaluation of cosmetics products aimed at mitigating the effects of ageing, e.g. through skin hydration and administration of antioxidants, as well as in the design of products with improved tactile sensation, e.g. through the optimisation of materials and surface textures.

Keeping in Touch with Mental Health: The Orienting Reflex and Behavioral Outcomes from Calatonia

Physical and psychological therapy based on touch has been gradually integrated into broader mental health settings in the past two decades, evolving from a variety of psychodynamic, neurobiological and trauma-based approaches, as well as Eastern and spiritual philosophies and other integrative and converging systems. Nevertheless, with the exception of a limited number of well-known massage therapy techniques, only a few structured protocols of touch therapy have been standardized and researched to date. This article describes a well-defined protocol of touch therapy in the context of psychotherapy-the Calatonia technique-which engages the orienting reflex. The orienting reflex hypothesis is explored here as one of the elements of this technique that helps to decrease states of hypervigilance and chronic startle reactivity (startle and defensive reflexes) and restore positive motivational and appetitive states.

Study on the Role of Histochemical Stains in Identifying Merkel Cells in Dogs

Merkel cells (MCs) are neuroendocrine cells involved with tactile sense, growth, differentiation, and homeostasis of the skin as well as in different cutaneous diseases. Specific staining techniques are required for their identification because they are not easily visible in paraffin sections stained with hematoxylin and eosin. The present study assess the histochemical features of the MCs in dogs comparing with those described for other mammals in the literature and with the use of immunohistochemistry. A systematic study of samples from MCs-rich areas from healthy dogs was carried out by use of several histologic stains, including metachromatic staining, silver stains, methylene blue, periodic acid-Schiff stain, and osmium-based staining method. MCs were detected by the Grimelius argyrophilic stain in 86.7% of the specimens. The staining was showed as dark-brown granular cytoplasmic and consistently polarized to the basal cell cytoplasm matching with the cellular distribution of the characteristic neurosecretory granules. Some modifications in the standard staining protocol, including rinsing, silver reimpregnation, and counterstain dye, enhanced the MCs identification in stratified squamous epithelium. When compared with Cytokeratin 20-immunolabeled serial sections several MCs appeared nonstained with the argyrophilic method. These differences in MC numbers between stains were statistically significant. Other histologic stains failed to identify MCs in the specimens. The results of this study indicate that Grimelius argyrophilic stain is a suitable method for demonstration of MCs in the stratified squamous epithelium of skin and mucosa. Discussion on its utility when compared with immunohistochemistry and a review of the scientific literature is also presented. Anat Rec, 302:1458-1464, 2019. © 2018 Wiley Periodicals, Inc.