Distinct and complementary roles of papillary and reticular fibroblasts in skin morphogenesis and homeostasis

To study the biological properties of dermal fibroblast sub-populations, we used a reconstructed skin model with a dermal compartment populated with either papillary or reticular fibroblasts. The histological and immunohistological characterization of these reconstructed skins revealed distinct biological and structural differences, depending on the site-matched fibroblast population incorporated. Epidermal differentiation and maturation was favored and found optimum in the presence of papillary fibroblasts with little effect on ECM, as opposed to reticular fibroblasts, which had a significant positive effect on the production of the ECM molecules of the dermal epidermal junction and the dermis. In addition, the synthesis and release of MMPs and soluble factors like VEGF and KGF into the culture medium were influenced by the fibroblast population. MMP1 and VEGF were increased in the presence of papillary fibroblasts, whereas MMP3 and KGF levels were higher in the presence of reticular fibroblasts. Our results suggest that papillary and reticular fibroblasts exert distinct functions and activities in skin as revealed by the reconstructed skin model. These functional differences may have implications in wound healing and skin aging processes, considering the slow loss of papillary fibroblasts in human skin that occurs with age.