Endogenous human skin equivalent promotes in vitro morphogenesis of follicle-like structures.

Three-dimensional constructs formed by cells embedded in an exogenous scaffold could not represent a faithful in vitro replica of native and functional tissues. In this work we produced an endogenous human skin equivalent by means of a tissue engineering process that induces the full morphogenesis of functional dermal and epidermal compartments. In such an organotypic context we demonstrated that -by using adult human skin cells-it is possible to generate follicle-like structures in vitro resembling what occurs in vivo in the fetal skin. Immunotypization evidences an inward-oriented differentiation of the follicular-like structures through immunopositivity for epithelial stem cell markers such as p63 and K19. Moreover we detected the presence of versican within the intricate network of the dermal compartment, suggesting its role as an inductive factor for the morphogenesis of appendage-like structures. These results support the importance of the repository and regulatory role of the endogenous extra cellular matrix in guiding tissue morphogenesis. The microenvironment provided by the endogenous human skin equivalent preserves p63 and K19 positive cells and could finally be involved in: (i) triggering the arrangement of the keratinocytes in follicle-like structures; (ii) promoting the convolute profile of the derma-epidermal junction and (iii) improving epidermis barrier function. We argue that the nature of dermal compartment plays a role in directing epithelial cell fate and function in vitro.