Caspase-14, a cysteine endoproteinase belonging to the conserved family of aspartate-specific proteinases, was shown to play an important role in the terminal differentiation of keratinocytes and barrier function of the skin. In the present study, we developed a biofunctional compound that we described as a modulator of caspase-14 expression. Using normal human keratinocytes (NHK) in culture and human skin biopsies, this compound was shown to increase caspase-14 expression and partially reverse the effect of caspase-14-specific siRNA on NHK. Moreover, the increase in filaggrin expression visualized on skin biopsies and the recovery of the barrier structure after tape-stripping indicated that this compound could exhibit a beneficial effect on the skin barrier function. Considering the possible link between caspase-14 and the barrier function, a UVB irradiation on NHK and skin biopsies previously treated with the caspase-14 inducer, was performed. Results indicated that pretreated skin biopsies exhibited less signs of UV damage such as active caspase-3 and cyclobutane pyrimidine dimers (CPDs). Likewise, pretreated NHK were protected from UV-induced genomic DNA damage, as revealed by the Comet Assay. Finally, a clinical test showed a reduction of transepidermal water loss (TEWL) on the treated skin compared with placebo, under UV stress condition, confirming a protecting effect. Taken together, these results strongly suggest that, by increasing caspase-14 expression, the biofunctional compound could exhibit a protective effect on the skin barrier function, especially in case of barrier damage and UV irradiation.

The stem cell factor (SCF) and its protein-tyrosine kinase receptor KIT are together implicated in the regulation of diverse biological processes and particularly in melanogenesis. Indeed, this signalling pathway controls melanoblast migration from the neural crest during embryogenesis and allows the communication between keratinocytes and melanocytes in the adult. In melanocytes, the binding of SCF to its transmembrane receptor leads to the activation of signalling pathways implicating protein kinases which finally control the expression of pigmentation-related genes. We have developed a biological compound called IV09.007, which we previously described as a modulator of the SCF/KIT signalling pathway with a pro-pigmenting effect. In the present work, we have studied the expression and localization of both SCF and KIT mRNAs and proteins in the skin or skin-derived cell lines. Then, we explored with a microarray approach the ability of IV09.007 to modulate the expression of genes in human keratinocytes and melanocytes in culture. Thereby, we observed the regulation of genes implicated in DNA repair, mainly related to base/nucleotides excision pathways. A modulated transcriptional response was also observed for some genes implicated in the response against oxidative stress, in apoptosis inhibition and in lowering inflammatory immune response. These microarray results predicted a conferred protective effect of IV09.007 and we verified this hypothesis by performing comet assays on UVB-irradiated keratinocytes or melanocytes, to demonstrate the efficacy of IV09.007 on preventing DNA damage.

Skin-derived precursors (SKPs) have been described as multipotent dermal precursors. Here, we provide a review of the breadth and depth of scientific literature and studies regarding SKPs, accounting for a large number of scientific publications. Interestingly, these progenitors can be isolated from embryonic and adult skin, as well as from a population of dermal cells cultured in vitro in monolayer. Gathering information from different authors, this review explores different aspects of the SKP theme, such as the potential distinct origins of SKPs in rodents and in humans, and also their ability to differentiate in vitro and in vivo into multiple lineages of different progeny. This remarkable capacity makes SKPs an interesting endogenous source of precursors to explore in the framework of experimental and therapeutic applications in different domains. SKPs are not only involved in the skin's dermal maintenance and support as well as wound healing, but also in hair follicle morphogenesis. This review points out the interests of future researches on SKPs for innovative perspectives that may be helpful in many different types of scientific and medical domains. exp erimentations en cours et a venir concernant les SKPs en vue de perspectives innovantes pouvant influencer la recherche dans de nombreux domaines scientifiques et m edicaux.

Skin aging is a process of structural and compositional remodeling that can be manifested by wrinkling and sagging. Remarkably, the dermis plays a dominant role in the aging process. Recent studies suggest that microRNAs are implicated in the regulation of gene expression during aging. However, studies about age-related microRNAs and how they modulate skin aging remain limited. In the present work, a complex of hydrolyzed natural yeast proteins (Saccharomyces cerevisiae) and hydrolyzed natural soya bean was developed and showed the ability to modulate the expression of telomere-binding protein TRF2, which is a key factor for telomere protection and to prevent cellular senescence in vitro and DNA damage. The aim of the study was to identify microRNAs specifically modulated after application of the ingredient complex to cultured fibroblasts, and their possible involvement in remodeling of the human extracellular matrix and fibroblast senescence. Consequently, human skin fibroblasts were cultured and treated with 1% of the ingredient complex for 48 h before analyzing microRNA modulation by RT-qPCR. The use of bioinformatics allowed us to predict the target genes for modulated microRNAs. Results show that the ingredient complex modulated a pattern of microRNAs including the down-regulation of miR-29a-3p, miR-30a-5p and miR-34a-5p, which are associated with fibroblast senescence and remodeling of * Corresponding author. X. H. Yan et al. 333 the human dermal extracellular matrix. In conclusion, our results indicate that miR-29a-3p, miR-30a-5p and miR-34a-5p possibly represent key microRNAs that impact human fibroblast senescence and remodeling of the dermal extracellular matrix.

Compound IV08.009 demonstrated to be effective in regulating survivin expression and in preserving the basal epidermis from stresses such as UVB and H2 O2 . These results suggest a protective activity of IV08.009 on the essential renewing potential of KSCs.