Equine epidermis: a source of epithelial-like stem/progenitor cells with in vitro and in vivo regenerative capacities

Besides the presence of somatic stem cells in hair follicles and dermis, the epidermis also contains a subpopulation of stem cells, reflecting its high regenerative capacity. However, only limited information concerning epidermis-derived epithelial-like stem/progenitor cells (EpSCs) is available to date. Nonetheless, this stem cell type could prove itself useful in skin reconstitution after injury. After harvesting from equine epidermis, the purified cells were characterized as EpSCs by means of positive expression for CD29, CD44, CD49f, CD90, Casein Kinase 2β, p63, and Ki67, low expression for cytokeratin (CK)14 and negative expression for CD105, CK18, Wide CK, and Pan CK. Furthermore, their self-renewal capacity was assessed in adhesion as well as in suspension. Moreover, the isolated cells were differentiated toward keratinocytes and adipocytes. To assess the regenerative capacities of EpSCs, six full-thickness skin wounds were made: three were treated with EpSCs and platelet-rich-plasma (EpSC/PRP-treated), while the remaining three were administered carrier fluid alone (PRP-treated). The dermis of EpSC/PRP-treated wounds was significantly thinner and exhibited more restricted granulation tissue than did the PRP-treated wounds. The EpSC/PRP-treated wounds also exhibited increases in EpSCs, vascularization, elastin content, and follicle-like structures. In addition, combining EpSCs with a PRP treatment enhanced tissue repair after clinical application.