Skin graft with dermis and appendages generated in vivo by cell competition.

Autologous skin grafting is a standard treatment for skin defects such as burns. No artificial skin substitutes are functionally equivalent to autologous skin grafts. The cultured epidermis lacks the dermis and does not engraft deep wounds. Although reconstituted skin, which consists of cultured epidermal cells on a synthetic dermal substitute, can engraft deep wounds, it requires the wound bed to be well-vascularized and lacks skin appendages. In this study, we successfully generate complete skin grafts with pluripotent stem cell-derived epidermis with appendages on p63 knockout embryos' dermis. Donor pluripotent stem cell-derived keratinocytes encroach the embryos' dermis by eliminating p63 knockout keratinocytes based on cell-extracellular matrix adhesion mediated cell competition. Although the chimeric skin contains allogenic dermis, it is engraftable as long as autologous grafts. Furthermore, we could generate semi-humanized skin segments by human keratinocytes injection into the amnionic cavity of p63 knockout mice embryos. Niche encroachment opens the possibility of human skin graft production in livestock animals.

Comparative Analysis of Olive-Derived Phenolic Compounds' Pro-Melanogenesis Effects on B16F10 Cells and Epidermal Human Melanocytes.

Olive leaf contains plenty of phenolic compounds, among which oleuropein (OP) is the main component and belongs to the group of secoiridoids. Additionally, phenolic compounds such as oleocanthal (OL) and oleacein (OC), which share a structural similarity with OP and two aldehyde groups, are also present in olive leaves. These compounds have been studied for several health benefits, such as anti-cancer and antioxidant effects. However, their impact on the skin remains unknown. Therefore, this study aims to compare the effects of these three compounds on melanogenesis using B16F10 cells and human epidermal cells. Thousands of gene expressions were measured by global gene expression profiling with B16F10 cells. We found that glutaraldehyde compounds derived from olive leaves have a potential effect on the activation of the melanogenesis pathway and inducing differentiation in B16F10 cells. Accordingly, the pro-melanogenesis effect was investigated by means of melanin quantification, mRNA, and protein expression using human epidermal melanocytes (HEM). This study suggests that secoiridoid and its derivates have an impact on skin protection by promoting melanin production in both human and mouse cell lines.

Efficacy of 233 nm LED far UV-C-radiation against clinically relevant bacterial strains in the phase 2/ step 2 in vitro test on basis of EN 14561 and on an epidermis cell model.

INTRODUCTION: Healthcare-acquired infections and overuse of antibiotics are a common problem. Rising emergence of antibiotic and antiseptic resistances requires new methods of microbial decontamination or decolonization as the use of far-UV-C radiation. METHODS: The microbicidal efficacy of UV-C radiation (222 nm, 233 nm, 254 nm) was determined in a quantitative carrier test and on 3D-epidermis models against Staphylococcus (S.) aureus, S.epidermidis, S.haemolyticus, S.lugdunensis, Klebsiella pneumoniae, and Pseudomonas aeruginosa. To mimic realistic conditions, sodium chloride solution, mucin, albumin, artificial saliva, artificial wound exudate and artificial sweat were used. RESULTS: In sodium chloride solution, irradiation with a dose of 40 mJ/cm2 (233 nm) was sufficient to achieve 5 lg reduction independent of bacteria genus or species. In artificial sweat, albumin and artificial wound exudate, a reduction >3 lg was reached for most of the bacteria. Mucin and artificial saliva decreased the reduction to <2 lg. On 3D epidermis models, reduction was lower than in the carrier test. CONCLUSION: UV-C radiation at 233 nm was proven to be efficient in bacteria inactivation independent of genus or species thus being a promising candidate for clinical use in the presence of humans and on skin/mucosa.

In vitro generation of epidermal keratinocytes from human CD34-positive hematopoietic stem cells.

The epidermis is largely composed of keratinocytes (KCs), and the proliferation and differentiation of KCs from the stratum basale to the stratum corneum is the cellular hierarchy present in the epidermis. In this study, we explore the differentiation abilities of human hematopoietic stem cells (HSCs) into KCs. Cultured HSCs positive for CD34, CD45, and CD133 with prominent telomerase activity were induced with keratinocyte differentiation medium (KDM), which is composed of bovine pituitary extract (BPE), epidermal growth factor (EGF), insulin, hydrocortisone, epinephrine, transferrin, calcium chloride (CaCl2), bone morphogenetic protein 4 (BMP4), and retinoic acid (RA). Differentiation was monitored through the expression of cytokeratin markers K5 (keratin 5), K14 (keratin 14), K10 (keratin 10), K1 (keratin 1), transglutaminase 1 (TGM1), involucrin (IVL), and filaggrin (FLG) on day 0 (D0), day 6 (D6), day 11 (D11), day 18 (D18), day 24 (D24), and day 30 (D30) using immunocytochemistry, fluorescence microscopy, flow cytometry, qPCR, and Western blotting. The results revealed the expression of K5 and K14 genes in D6 cells (early keratinocytes), K10 and K1 genes in D11-D18 cells (mature keratinocytes) with active telomerase enzyme, and FLG, IVL, and TGM1 in D18-D24 cells (terminal keratinocytes), and by D30, the KCs were completely enucleated similar to cornified matrix. This method of differentiation of HSCs to KCs explains the cellular order exists in the normal epidermis and opens the possibility of exploring the use of human HSCs in the epidermal differentiation.

Upregulation of IDO gene expression reduces the immunogenicity of epidermal cells and strengthens the immune protection of epidermal cells during transplantation treatment of wounds.

BACKGROUND: Epidermal cell transplantation is a feasible treatment option for large wounds; however, sources of autologous epidermal cells are often limited. Allogeneic epidermal cells can be cultured conveniently; however, related immune rejection needs to be addressed. Herein, we hypothesized that the immunogenicity of epidermal cells with high indoleamine 2,3-dioxygenase (IDO) expression may be reduced by gene transfection. METHODS/RESULTS: To test this hypothesis, we obtained stable transfectants by transfecting epidermal stem cells with a lentiviral vector encoding the IDO gene and screening them for puromycin resistance (a marker for successful transfection). The phenotype tested using cell counting kit -8 and Transwell assays confirmed that IDO-transfected epidermal cells maintained their characteristics. Co-culture of IDO-transfected epidermal cells with allogeneic CD4+ T cells in vitro showed that the upregulation of IDO expression in epidermal cells inhibited the proliferation of CD4+ T cells (P < 0.001, P < 0.001, and P < 0.001, respectively) and promoted their apoptosis (P = 0.00028, P = 0.0006, and P = 0.00247, respectively) and transformation into functional regulatory T cells (Tregs) (P = 0.0051, P = 0.0132, and P = 0.0248, respectively) compared with Con, NC, and 1-MT groups. The increased proportion of Tregs may be related to the overexpression of IDO, which promoted the expression of transforming growth factor beta (TGF-ß) (P = 0.0001, P = 0.0013, and, P = 0.0009) and interleukin (IL) 10 (IL-10) (P = 0.0062, P = 0.0058, and P = 0.0119) while inhibited the expression of IL-2 (P = 0.0012, P = 0.0126, and P = 0.0066). We further verified these effects in vivo as transplanted IDO-transfected epidermal stem cells were effective in treating wounds in mice. On days 5 and 7, wounds treated with IDO cells healed faster than those in the other groups (day 5: P = 0.012 and P = 0.0136; day 7: P = 0.0242 and P = 0.0187, respectively), whereas this effect was significantly inhibited by 1-methyltryptophan (1-MT) (day 5: P = 0.0303; day 7: P = 0.0105). Immunofluorescence staining detected IDO and CD4+ Foxp3+ Tregs in the transplanted wounds, which may promote Foxp3+ Tregs in the wound tissue (day 5: P < 0.0001, P < 0.0001, and P < 0.0001; day 7: P < 0.0001, P < 0.0001, and P < 0.0001), respectively) and decrease CD4+ T cells (day 5: P < 0.0001, P < 0.0001, and P < 0.0001; day 7: P < 0.0001, P < 0.0001, and P < 0.0001). CONCLUSION: Our results suggest that the upregulation of IDO expression in epidermal stem cells can reduce their immunogenicity by promoting Tregs, thus inducing the immune protection of epidermal stem cells.

Human filaggrin monomer does not seem to be a proteasome target.

Absence of a functional proteasome in the suprabasal layers of the epidermis is responsible for keratosis linearis with ichthyosis congenital and sclerosing keratoderma syndrome. Patient epidermis shows hypergranulosis associated with abnormally shaped keratohyalin granules and abnormal distribution of filaggrin in the Stratum granulosum and Stratum corneum. This suggests that the proteasome is involved in the degradation of filaggrin. To test this hypothesis, the proteasome proteolytic activity was inhibited in 3D reconstructed human epidermis (RHE) with the specific clasto-lactacystin ß-lactone inhibitor. Confirming the efficacy of inhibition, ubiquitinated proteins accumulated in treated RHEs as compared to controls. Levels of urocanic acid (UCA) and pyrrolidone carboxylic acid (PCA), the end products of filaggrin degradation, were reduced. However, neither filaggrin accumulation nor appearance of filaggrin-derived peptides were observed. On the contrary, the amount of filaggrin was shown to decrease, and a similar tendency was observed for profilaggrin, its precursor. Accumulation of small cytoplasmic vesicles associated with a significant increase in autophagy markers indicated activation of the autophagy process upon proteasome inhibition. Taken together, these results suggest that the perturbation of UCA and PCA production after proteasome inhibition was probably due to down-regulation of filaggrin expression rather than to blocking of filaggrin proteolysis.

LGN loss randomizes spindle orientation and accelerates tumorigenesis in PTEN-deficient epidermis.

Loss of cell polarity and disruption of tissue organization are key features of tumorigenesis that are intrinsically linked to spindle orientation. Epithelial tumors are often characterized by spindle orientation defects, but how these defects impact tumor formation driven by common oncogenic mutations is not fully understood. Here, we examine the role of spindle orientation in adult epidermis by deleting a key spindle regulator, LGN, in normal tissue and in a PTEN-deficient mouse model. We report that LGN deficiency in PTEN mutant epidermis leads to a threefold increase in the likelihood of developing tumors on the snout, and an over 10-fold increase in tumor burden. In this tissue, loss of LGN alone increases perpendicular and oblique divisions of epidermal basal cells, at the expense of a planar orientation of division. PTEN loss alone does not significantly affect spindle orientation in these cells, but the combined loss of PTEN and LGN fully randomizes basal spindle orientation. A subset of LGN- and PTEN-deficient animals have increased amounts of proliferative spinous cells, which may be associated with tumorigenesis. These results indicate that loss of LGN impacts spindle orientation and accelerates epidermal tumorigenesis in a PTEN-deficient mouse model.

Systemically administered wound-homing peptide accelerates wound healing by modulating syndecan-4 function.

CAR (CARSKNKDC) is a wound-homing peptide that recognises angiogenic neovessels. Here we discover that systemically administered CAR peptide has inherent ability to promote wound healing: wounds close and re-epithelialise faster in CAR-treated male mice. CAR promotes keratinocyte migration in vitro. The heparan sulfate proteoglycan syndecan-4 regulates cell migration and is crucial for wound healing. We report that syndecan-4 expression is restricted to epidermis and blood vessels in mice skin wounds. Syndecan-4 regulates binding and internalisation of CAR peptide and CAR-mediated cytoskeletal remodelling. CAR induces syndecan-4-dependent activation of the small GTPase ARF6, via the guanine nucleotide exchange factor cytohesin-2, and promotes syndecan-4-, ARF6- and Cytohesin-2-mediated keratinocyte migration. Finally, we show that genetic ablation of syndecan-4 in male mice eliminates CAR-induced wound re-epithelialisation following systemic administration. We propose that CAR peptide activates syndecan-4 functions to selectively promote re-epithelialisation. Thus, CAR peptide provides a therapeutic approach to enhance wound healing in mice; systemic, yet target organ- and cell-specific.

Catfish Epidermal Club Cell Morphologic and Immunologic Attributes: Heterogeneous S-100 Immunoreactivity and Possible Neuroendocrine Function.

The fish epidermis (EP) contains several cell types, and it has several functional roles, though the secretory role prevails. The alarm or epidermal club cells (ECCs) represent a voluminous immune cell secreting an alarm substance. Our work targeted the histochemical and immunologic attributes of the ECCs in catfish. Matrix metalloproteinase (MMP-9) immunostaining revealed strong immunoreactive signals in the cytoplasm of all ECCs, while S-100 protein immunoreactivity selectively marked the ECCs. Individual ECCs exhibit intense S-100 immunoreactivity compared to neighboring ECCs. The difference in the intensity of the S-100 immunostaining was associated with the difference in the ECC size. This was confirmed by the semithin results where several developmental stages of ECCs could be distinguished. Some eosinophilic granular cells with their characteristic metachromatic granules were recorded juxtaposing the ECCs. Moreover, some free electron-dense granules could be demonstrated in the intercellular spaces surrounding the ECCs. Collectively, these findings suggest several functional profiles for the catfish ECCs depending on their developmental stage. Most importantly, S-100 immunoreactivity in the ECCs suggests its neuroendocrine function. Moreover, the difference in the intensity and polar distribution of S-100 staining is a sign of its role in the differentiation of the ECCs.

Invasion depth estimation of carcinoma cells using adaptive stain normalization to improve epidermis segmentation accuracy.

Submucosal invasion depth is a significant prognostic factor when assessing lymph node metastasis and cancer itself to plan proper treatment for the patient. Conventionally, oncologists measure the invasion depth by hand which is a laborious, subjective, and time-consuming process. The manual pathological examination by measuring accurate carcinoma cell invasion with considerable inter-observer and intra-observer variations is still challenging. The increasing use of medical imaging and artificial intelligence reveals a significant role in clinical medicine and pathology. In this paper, we propose an approach to study invasive behavior and measure the invasion depth of carcinoma from stained histopathology images. Specifically, our model includes adaptive stain normalization, color decomposition, and morphological reconstruction with adaptive thresholding to separate the epithelium with blue ratio image. Our method splits the image into multiple non-overlapping meaningful segments and successfully finds the homogeneous segments to measure accurate invasion depth. The invasion depths are measured from the inner epithelium edge to outermost pixels of the deepest part of particles in image. We conduct our experiments on skin melanoma tissue samples as well as on organotypic invasion model utilizing myoma tissue and oral squamous cell carcinoma. The performance is experimentally compared to three closely related reference methods and our method provides a superior result in measuring invasion depth. This computational technique will be beneficial for the segmentation of epithelium and other particles for the development of novel computer-aided diagnostic tools in biobank applications.

New insights into inflammatory memory of epidermal stem cells.

Inflammatory memory, as one form of innate immune memory, has a wide range of manifestations, and its occurrence is related to cell epigenetic modification or metabolic transformation. When re-encountering similar stimuli, executing cells with inflammatory memory function show enhanced or tolerated inflammatory response. Studies have identified that not only hematopoietic stem cells and fibroblasts have immune memory effects, but also stem cells from various barrier epithelial tissues generate and maintain inflammatory memory. Epidermal stem cells, especially hair follicle stem cells, play an essential role in wound healing, immune-related skin diseases, and skin cancer development. In recent years, it has been found that epidermal stem cells from hair follicle can remember the inflammatory response and implement a more rapid response to subsequent stimuli. This review updates the advances of inflammatory memory and focuses on its mechanisms in epidermal stem cells. We are finally looking forward to further research on inflammatory memory, which will allow for the development of precise strategies to manipulate host responses to infection, injury, and inflammatory skin disease.

Barrier function and ultrastructure characteristics of epidermis in patients with primary cutaneous amyloidosis.

Previous studies on primary cutaneous amyloidosis (PCA) have mainly focused on exploring genetic mutation and components of amyloid in patients with PCA. However, studies on skin barrier function in PCA patients are scarce. Here, we detected the skin barrier function in PCA patients and healthy people by using noninvasive techniques and characterized ultrastructural features of PCA lesions compared with healthy people using transmission electron microscopy (TEM). The expression of proteins related to skin barrier function was examined by immunohistochemistry staining. A total of 191 patients with clinically diagnosed PCA and 168 healthy individuals were enrolled in the study. Our analysis revealed that all investigated lesion areas displayed higher transepidermal water loss and pH values, and lower Sebum levels and stratum corneum hydration levels in PCA patients compared with the same site area in healthy individuals. The TEM results showed that the intercellular spaces between the basal cells were enlarged and the number of hemidesmosomes decreased in PCA lesions. Immunohistochemical staining showed that the expression of integrin α6 and E-cadherin in PCA patients was less than that in healthy controls, while no differences in the expression of loricrin and filaggrin were observed. Our study revealed that individuals with PCA displayed skin barrier dysfunction, which may be related to alterations in epidermal ultrastructure and a decrease in the skin barrier-related protein E-cadherin. However, the molecular mechanisms underlying skin barrier dysfunction in PCA remain to be elucidated.

Decoding the Human Epidermal Complexity at Single-Cell Resolution.

The epidermis is one of the largest tissues in the human body, serving as a protective barrier. The basal layer of the epidermis, which consists of epithelial stem cells and transient amplifying progenitors, represents its proliferative compartment. As keratinocytes migrate from the basal layer to the skin surface, they exit the cell cycle and initiate terminal differentiation, ultimately generating the suprabasal epidermal layers. A deeper understanding of the molecular mechanisms and pathways driving keratinocytes' organization and regeneration is essential for successful therapeutic approaches. Single-cell techniques are valuable tools for studying molecular heterogeneity. The high-resolution characterization obtained with these technologies has identified disease-specific drivers and new therapeutic targets, further promoting the advancement of personalized therapies. This review summarizes the latest findings on the transcriptomic and epigenetic profiling of human epidermal cells, analyzed from human biopsy or after in vitro cultivation, focusing on physiological, wound healing, and inflammatory skin conditions.

The value of adding platelet-rich plasma (PRP) to noncultured epidermal cell suspension (NCECS) in surgical treatment of stable resistant vitiligo: A self-controlled randomised double-blinded study.

BACKGROUND: Noncultured epidermal cell suspension (NCECS) is a commonly used surgical treatment for resistant stable acral vitiligo and vitiligo overlying joints. Platelet-rich plasma (PRP) has been reported to enhance the repigmentation response of different therapeutic modalities for vitiligo, including vitiligo surgery. OBJECTIVE: To assess the value of adding of PRP to NCECS in the surgical treatment of acral vitiligo and vitiligo overlying joints. PATIENTS AND METHODS: This self-controlled randomised trial included 15 patients with 30 lesions in which NCECS suspended in PRP was performed for one lesion and NCECS in ringer's lactate for another comparable lesion. Following NCECS, patients underwent thrice weekly excimer light sessions for 3 months. After 8 weeks, patients underwent preliminary assessment. By the end of the 3 months, both lesions were compared as regards improvement in surface area and pigmentation. Additionally, physician global assessment was made by a blinded investigator. RESULTS: Significant improvement was reported in both lesional extent and pigmentation (after PRP and lactated ringer NCECS) with no statistical difference between them. CONCLUSION: Despite previous promising results, suspending NCECS in PRP offered no privilege in surgical treatment of acral vitiligo and vitiligo overlying joints, which are quite resistant to treat. PAN AFRICAN CLINICAL TRIAL REGISTRY ID: PACTR202108873035929, Date: 16 August 2021.

Revealing the Meissner Corpuscles in Human Glabrous Skin Using In Vivo Non-Invasive Imaging Techniques.

The presence of mechanoreceptors in glabrous skin allows humans to discriminate textures by touch. The amount and distribution of these receptors defines our tactile sensitivity and can be affected by diseases such as diabetes, HIV-related pathologies, and hereditary neuropathies. The quantification of mechanoreceptors as clinical markers by biopsy is an invasive method of diagnosis. We report the localization and quantification of Meissner corpuscles in glabrous skin using in vivo, non-invasive optical microscopy techniques. Our approach is supported by the discovery of epidermal protrusions which are co-localized with Meissner corpuscles. Index fingers, small fingers, and tenar palm regions of ten participants were imaged by optical coherence tomography (OCT) and laser scan microscopy (LSM) to determine the thickness of the stratum corneum and epidermis and to count the Meissner corpuscles. We discovered that regions containing Meissner corpuscles could be easily identified by LSM with an enhanced optical reflectance above the corpuscles, caused by a protrusion of the strongly reflecting epidermis into the stratum corneum with its weak reflectance. We suggest that this local morphology above Meissner corpuscles has a function in tactile perception.

Polarity in skin development and cancer.

The epidermis is a stratified squamous epithelium that forms the outermost layer of the skin. Its primary function is to act as a barrier, keeping pathogens and toxins out and moisture in. This physiological role has necessitated major differences in the organization and polarity of the tissue as compared to simple epithelia. We discuss four aspects of polarity in the epidermis - the distinctive polarities of basal progenitor cells as well as differentiated granular cells, the polarity of adhesions and the cytoskeleton across the tissue as keratinocytes differentiate, and the planar cell polarity of the tissue. These distinctive polarities are essential for the morphogenesis and the function of the epidermis and have also been implicated in regulating tumor formation.

Automatic granular and spinous epidermal cell identification and analysis on in vivo reflectance confocal microscopy images using cell morphological features.

Significance: Reflectance confocal microscopy (RCM) allows for real-time in vivo visualization of the skin at the cellular level. The study of RCM images provides information on the structural properties of the epidermis. These may change in each layer of the epidermis, depending on the subject's age and the presence of certain dermatological conditions. Studying RCM images requires manual identification of cells to derive these properties, which is time consuming and subject to human error, highlighting the need for an automated cell identification method. Aim: We aim to design an automated pipeline for the analysis of the structure of the epidermis from RCM images of the Stratum granulosum and Stratum spinosum. Approach: We identified the region of interest containing the epidermal cells and the individual cells in the segmented tissue area using tubeness filters to highlight membranes. We used prior biological knowledge on cell size to process the resulting detected cells, removing cells that were too small and reapplying the used filters locally on detected regions that were too big to be considered a single cell. The proposed full image analysis pipeline (FIAP) was compared with machine learning-based approaches (cell cutter, different U-Net configurations, and loss functions). Results: All methods were evaluated both on simulated data (four images) and on manually annotated RCM data (seven images). Accuracy was measured using recall and precision metrics. Both accuracy metrics were higher in the proposed FIAP for both real ( precision = 0.720 ± 0.068 , recall = 0.850 ± 0.11 ) and synthetic images ( precision = 0.835 ± 0.067 , recall = 0.925 ± 0.012 ). The tested machine learning methods failed to identify and segment keratinocytes on RCM images with a satisfactory accuracy. Conclusions: We showed that automatic cell segmentation can be achieved using a pipeline based on membrane detection, with an accuracy that matches expert manual cell identification. To our knowledge, this is the first method based on membrane detection to study healthy skin using RCM images evaluated against manually identified cell positions.

Rapid Cellular-Resolution Skin Imaging with Optical Coherence Tomography Using All-Glass Multifocal Metasurfaces.

Cellular-resolution optical coherence tomography (OCT) is a powerful tool offering noninvasive histology-like imaging. However, like other optical microscopy tools, a high numerical aperture (N.A.) lens is required to generate a tight focus, generating a narrow depth of field, which necessitates dynamic focusing and limiting the imaging speed. To overcome this limitation, we developed a metasurface platform that generates multiple axial foci, which multiplies the volumetric OCT imaging speed by offering several focal planes. This platform offers accurate and flexible control over the number, positions, and intensities of axial foci generated. All-glass metasurface optical elements 8 mm in diameter are fabricated from fused-silica wafers and implemented into our scanning OCT system. With a constant lateral resolution of 1.1 µm over all depths, the multifocal OCT triples the volumetric acquisition speed for dermatological imaging, while still clearly revealing features of stratum corneum, epidermal cells, and dermal-epidermal junctions and offering morphological information as diagnostic criteria for basal cell carcinoma. The imaging speed can be further improved in a sparse sample, e.g., 7-fold with a seven-foci beam. In summary, this work demonstrates the concept of metasurface-based multifocal OCT for rapid virtual biopsy, further providing insights for developing rapid volumetric imaging systems with high resolution and compact volume.

Transgenic skin biomechanical properties following first lifesaving epidermal regeneration using combined gene and cell therapy.

BACKGROUND: In 2017, we reported the first life-saving regeneration of virtually an entire epidermis by combined gene and stem cell therapy. Recently, we demonstrated excellent long-term stability of this transgenic epidermis. Skin quality in this experimental approach and its potential application in other conditions were elucidated here regarding long-term outcomes of biomechanical properties. PATIENTS AND METHODS: Analysis of biomechanical properties including skin elasticity, anisotropy and friction was performed on multiple body sites 24, 36 and 60 months following transplantation. Firstly, the sites were matched against and compared to remaining stable non-transgenic areas as well as to a control group of 13 healthy subjects. Parameters for skin elasticity, deformation and friction were assessed non-invasively. RESULTS: Biomechanical properties of the transgenic epidermis showed encouraging results in comparison to both the remaining stable non-transgenic skin as well as healthy controls. Skin elasticity was comparable to the controls. Skin friction showed some decrease in both transgenic and non-transgenic areas as compared to the controls. CONCLUSIONS: The excellent functional outcomes of the transgenic epidermis demonstrate stable long-term results of this novel combined gene and stem cell therapy for epidermal regeneration. Thus, other applications for this technology, such as treatment of specific burns, should be explored.

Ageing is associated with a reduction in markers of mitochondrial energy metabolism in the human epidermis.

The decline of mitochondrial function throughout the lifespan is directly linked to the development of ageing phenotypes of the skin. Here, we assessed alterations in markers of epidermal mitochondrial energy metabolism as a function of skin age. Human skin samples from distinct anatomical regions were obtained during routine dermatological surgery from 21 young (27.6 ± 1.71 year) and 22 old (76.2 ± 1.73 year) donors. Sections of skin samples were analysed by immunohistochemistry for mitochondrial subunits of each electron transport chain complex (I-V)/oxidative phosphorylation (OXPHOS), as well as proteins serving as a marker of mitochondrial mass (VDAC1) and the regulation of DNA transcription (TFAM). Staining intensities of ATP5F1A (comprising complex V) and TFAM in the epidermis of older subjects were significantly decreased compared with younger donors. Moreover, these effects were independent of UV exposure of the stained skin section. Overall, we demonstrate that ageing is associated with reduced protein levels of complex V of the mitochondrial respiratory chain and TFAM. These alterations may impair essential mitochondrial functions, exacerbating the cutaneous ageing process.