644 Papillary and reticular fibroblasts generate specific microenvironments in vitro that impact their angiogenic profile

Abstract

Human dermis is divided between the superficial papillary dermis and the deeper reticular dermis that show distinct extracellular matrix (ECM) and vasculature. Papillary and reticular fibroblasts have distinct phenotype and gene signature but the contribution of each subtype of fibroblasts in the generation of specific ECM and vasculature is poorly documented. This study aimed to determine if papillary and reticular fibroblasts generate specific microenvironments in vitro when cultivated as cell sheet and evaluate their impact on angiogenesis. RNAseq transcriptomic analysis of papillary and reticular cell sheets revealed that genes related to ECM and angiogenesis were the most regulated in both subtypes. Papillary and reticular fibroblasts showed specific matrisomes and we identified biological functions suggesting the deposition of distinct ECM. We then verified differences in ECM composition and ultrastructure at the protein level. We also identified angiogenesis gene signature with an enrichment in pro-angiogenic genes in the papillary fibroblasts. In agreement, the conditioned medium from these fibroblasts has a higher angiogenic potential compared to the reticular fibroblasts in 3D. Moreover, when cultivated with endothelial cells, papillary microenvironment induced the formation of a denser network of thinner capillaries compared to the reticular one, thus reproducing some features of dermis vasculature. These results indicate that papillary and reticular fibroblasts generate specific microenvironments when cultivated as cell sheets that differentially impact angiogenesis. This indicates that dermal fibroblast heterogeneity should be taken into consideration for tissue engineering and regenerative medicine applications.