The overarching aim of this study is to investigate and characterize the molecular and cellular players in the microenvironment of human skin dermis in order to improve skin tissue regeneration.
At the molecular level, the affects of both canonical and non-canonical Wnt signaling ligands on human primary keratinocyte proliferation and differentiation were studied using Wnt conditioned medium from L-cells secreting wnt3a and wnt5a. Our data suggest that canonical Wnt3A suppresses keratinocyte proliferation in vitro by inducing differentiation, whereas non-canonical Wnt5A promotes keratinocyte proliferation.
At the cellular level, our lab has previously identified a VLA-1 (integrin alpha 1) bright population in human skin dermis that bears clear pericyte properties. Our previous studies have firmly demonstrated that the inclusion of VLA-1bri pericytes with fibroblast-populated dermal equivalents (DEs) promotes epidermal reconstitution in organotypic cultures. We now further characterize VLA-1bri pericytes in epidermal regeneration and skin ageing. We demonstrate that DEs comprised solely of pericytes are sufficient to promote epidermal tissue regeneration in organotypic culture assays, and induce a more polarized basal keratinocyte morphology, with a densely packed and well-organized stratum basale that highly resembles normal skin. Our data also show, for the first time, that pericyte populated DEs restore basal expression of keratin 15 (K15), which is present in normal healthy skin but absent in in vitro reconstituted skin, psoriatic or wounded skin. We have also begun to investigate the incidence of pericytes in skin from donors of increasing age and have established that the proportion of VLA-1bri pericytes as a function of overall dermal cellularity decreases with increasing age. However, their ability to promote epidermal regeneration was maintained despite ageing.
We conclude that the regenerative microenvironment in skin can be manipulated to improve ex vivo regeneration of skin grafts for autologous transplantation.