Dermal Papilla Cells improve the wound healing process and generate hair bud-like structures in grafted skin substitutes using Hair Follicle Stem Cells

Abstract

Tissue-engineered skin represents a useful strategy for the treatment of deep skin injuries and may contribute to the understanding of skin regeneration. The growth of hair follicles in vitro or after grafting remains a major challenge. The dermal-epidermal composites are skin substitutes comprised of dermal fibroblasts (DF) embedded in a matrix overlaid with keratinocytes. Hair Follicle Stem Cells (HFSC) contribute to hair follicle regeneration and wound repair. Dermal papilla cells (DPC) signaling orchestrates hair follicle morphogenesis and regeneration. The use of DPC as dermal component in a permanent composite skin with human HFSC was evaluated by studying tissue-engineered skin architecture, stem cell persistence and hair regeneration as well as the graft-take in nude mice. A porcine acellular dermal matrix (ADM) was seeded with HFSC alone and with human DPC or DF. Histological and immunohistochemical analyses of in vitro constructs were performed. The presence of DPC induced a more regular and multi-layered stratified epidermis with more basal p63-positive cells and invaginations. Graft-take and tissue remodeling in nude mice were favored in DPC-containing composite skin supported by the fact of graft-epidermis survival and early neovascularization. Interestingly, only in grafted constructs containing DPC, embryonic hair bud-like structures were observed from 14 days after grafting. These structures showed cells of human origin, presence of precursor epithelial cells and expression of a hair differentiation marker. These observations suggest an incipient hair follicle neogenesis inside the remodeling ADM. Taken together our results show DPC and HFSC as promising cellular components for a permanent skin substitute.