The mechanisms affecting epidermal homeostasis during aging remain poorly understood. To identify age-related microRNAs, a class of non-coding RNAs known to play a key role in the regulation of epidermal homeostasis, an exhaustive miRNA expression screen was performed in human keratinocytes from young or elderly subjects. Many microRNAs modulated by aging were identified, including miR-30a, in which both strands were overexpressed in aged cells and epidermal tissue. Stable MiR-30a over-expression strongly impaired epidermal differentiation, inducing severe barrier function defects in an organotypic culture model. A significant increase was also observed in the level of apoptotic cells in epidermis over-expressing miR-30a. Several gene targets of miR-30a were identified in keratinocytes, including LOX (encoding lysyl oxidase, a regulator of the proliferation/differentiation balance of keratinocytes), IDH1 (encoding isocitrate dehydrogenase, an enzyme of cellular metabolism) and AVEN (encoding a caspase inhibitor). Direct regulation of LOX, IDH1 and AVEN by miR-30a was confirmed in human keratinocytes. They were, moreover, observed to be repressed in aged skin, suggesting a possible link between miR-30a induction and skin-aging phenotype. This study revealed a new miRNA actor and deciphered new molecular mechanisms to explain certain alterations observed in epidermis during aging and especially those concerning keratinocyte differentiation and apoptosis.

Skin is constantly exposed to environmental factors such as pollutants, chemicals and ultra violet radiation (UV), which can induce premature skin aging and increase the risk of skin cancer. One strategy to reduce the effect of oxidative stress produced by environmental exposure is the application of antioxidant molecules. Among the endogenous antioxidants, selenoproteins play a key role in antioxidant defense and in maintaining a reduced cellular environment. Selenium, essential for the activity of selenoproteins, is a trace element that is not synthesized by organisms and must be supplied by diet or supplementation. The aim of this study is to evaluate the effect of Selenium supplementation on skin aging, especially on keratinocytes, the main cells of the epidermis. Our results demonstrate for the first time to our knowledge, the major role of Selenium on the replicative life span of keratinocytes and on aging skin. Selenium protects keratinocyte stem cells (KSCs) against senescence via preservation of their stemness phenotype through adhesion to the basement membrane. Additionally, Selenium supplementation maintains the homeostasis of skin during chronological aging in our senescent skin equivalent model. Controlled supplementation with Selenium could be a new strategy to protect skin against aging.

Vasculature cross-talking with epithelial stem cells is not understood in adult skin homeostasis. Skin vasculature undergoes dramatic remodeling during adult hair cycle. Specifically, a dermal horizontal plexus transiently neighbors the hair follicle stem cell activation zone during the quiescence phase of hair homeostasis (cycle). We showed that increased density of this plexus was induced by reciprocal mutations in the epithelium (Runx1) and endothelium (Alk1). This increase in vasculature correlates with prolonged quiescence of hair follicle stem cells and delayed entry into the hair growth phase, suggesting an inhibitory role of dense vasculature neighboring stem cells. Suggestively, we find that skin vasculature produces BMP4, a known hair follicle stem cell quiescence-inducing factor. Our work provides a scaffold for understanding how reciprocal cross-talking between epithelial stem cells and their neighboring vasculature promotes coordinated remodeling and modulates timing of hair follicle stem cell activation for proper tissue homeostasis of adult skin.

Background In human subcutaneous adipose tissue, the superficial fascia distinguishes superficial and deep microenvironments showing extensions called retinacula cutis. The superficial subcutaneous adipose tissue has been described as hyperplastic and the deep subcutaneous adipose tissue as inflammatory. However, few studies have described stromal-vascular fraction (SVF) content and adipose-derived stromal/stem cells (ASCs) behavior derived from superficial and deep subcutaneous adipose tissue. In this study, we analyzed a third conjunctive microenvironment: the retinacula cutis superficialis derived from superficial subcutaneous adipose tissue. Methods The samples of abdominal human subcutaneous adipose tissue were obtained during plastic aesthetic surgery in France (Declaration DC-2008-162) and Brazil (Protocol 145/09). Results The SVF content was characterized in situ by immunofluorescence and ex vivo by flow cytometry revealing a high content of pre-adipocytes rather in superficial subcutaneous adipose tissue microenvironment. Adipogenic assays revealed higher percentage of lipid accumulation area in ASCs from superficial subcutaneous adipose tissue compared with retinacula cutis superficialis (p < 0.0001) and deep subcutaneous adipose tissue (p < 0.0001). The high adipogenic potential of superficial subcutaneous adipose tissue was corroborated by an up-regulation of adipocyte fatty acid-binding protein (FABP4) compared with retinacula cutis superficialis (p < 0.0001) and deep subcutaneous adipose tissue (p < 0.0001) and of C/EBPα (CCAAT/enhancer-binding protein alpha) compared with retinacula cutis superficialis (p < 0.0001) and deep subcutaneous adipose tissue (p < 0.0001) microenvironments. Curiously, ASCs from retinacula cutis superficialis showed a higher level of adiponectin receptor gene compared with superficial subcutaneous adipose tissue (p = 0.0409), widely known as an anti-inflammatory hormone. Non-induced ASCs from retinacula cutis superficialis showed higher secretion of human vascular endothelial growth factor (VEGF), compared with superficial (p = 0.0485) and deep (p = 0.0112) subcutaneous adipose tissue and with adipogenic-induced ASCs from superficial (p = 0.0175) and deep (p = 0.0328) subcutaneous adipose tissue. Furthermore, ASCs from retinacula cutis superficialis showed higher secretion of Chemokine (C–C motif) ligand 5 (CCL5) compared with non-induced (p = 0.0029) and induced (p = 0.0089) superficial subcutaneous adipose tissue. Conclusions This study highlights the contribution to ASCs from retinacula cutis superficialis in their angiogenic property previously described for the whole superficial subcutaneous adipose tissue besides supporting its adipogenic potential for superficial subcutaneous adipose tissue.

ABCA12 is known to be critical for skin barrier integrity. Mutations in this gene cause the most severe form of Autosomal Recessive Congenital Ichthyosis, Harlequin Ichthyosis (HI). HI patients have marked hyperkeratosis at birth with fissuring, leading to life-threatening complications due to increased risk of infection, trans-epidermal water and heat loss. The aim of this study was to identify essential pathways involved in the pathomechanisms of Harlequin Ichthyosis, responsible for aberrant epidermal differentiation. We performed RNA-seq on calcium induced primary keratinocytes with siRNA knockdown of ABCA12 and identified 118 genes significantly down-regulated and 36 genes significantly up-regulated (FDR < 0.05). Functional annotation clustering analysis showed changes in epidermal differentiation, fatty acid metabolism, cytokine and interferon signaling. The suppressor of cytokine signaling 3 (SOCS3), a negative feedback regulator of the JAK-STAT signaling pathway, was 2.5 fold downregulated whereas Interleukin-1 (IL1A and IL1B) were 2 fold increased. To investigate these findings further we engineered an ABCA12 CRISPR-Cas9 knockout keratinocyte cell line and compared this with a HI patient-derived cell line and wild type controls. Alterations in differentiation and lipid profile in the HI OT models were observed, recapitulating the HI epidermis phenotype. We found that phospho-STAT1 (Y701) was strongly upregulated in the HI model compared to control. In HI patient skin, the STAT1 expression pattern was altered compared to control skin. The secretion of IL-1a was increased in the HI model compared to control. Both STAT1 and IL-1 regulate the Nitric Oxide (NO) pathway upregulating transcription of inducible NO synthase (iNOS), which we found to be significantly upregulated in HI skin. These data provide insights into the pathogenesis of HI suggest that the NO signaling pathway may be a possible therapeutic target in this disorder. 089MiR-30a is an aged-related microRNA that impairs differentiation and induces apoptosis in human epidermis The age-related alterations of epidermis are essentially characterized by a defect in the tissue renewal caused by a reduced keratinocytes proliferation and by a disturbance of their differentiation. However, the mechanisms disturbing epidermal homeostasis during aging remain poorly understood. To go further into this question, we focused on microRNAs (miRNAs), a class of non-coding RNAs known to play a key role in the regulation of epidermal homeostasis. To identify age-related microRNAs, we performed an exhaustive miRNAs microarray expression screen in human primary keratinocytes from young or elderly peoples. This screening revealed many microRNAs modulated by aging including miR-30a, exhibiting both strands overexpressed in aged cells and tissue. We also observed that miR-30a-3p and -5p were significantly induced in a reconstructed skin model mimicking chronological aging. We then constructed a lentiviral vector allowing its inducible and stable overexpression in primary...