374 Dermal fibroblasts from aged human skin express elevated levels of pro-inflammatory mediators

The dermal extracellular matrix (ECM) provides mechanical support to the skin and a microenvironment that is critical for the function of dermal cells. Dermal fibroblasts synthesize, organize, and reside within the dermal ECM. During aging, the ECM becomes fragmented. This fragmentation is associated with the clinical manifestations of aging, i.e., thin, fragile skin, and deleterious alterations of fibroblast function, most notably reduced expression of ECM structural genes and increased expression of pro-inflammatory mediators. We have investigated the degree to which the functional alterations of fibroblasts in aged skin reflect adaptation to the aged dermal ECM microenvironment versus cell-autonomous age-driven responses. Primary dermal fibroblasts from young (20-30 years, 6 females, 6 males) and aged (>80 years, 6 females, 6 males) individuals were placed in standard monolayer culture and harvested at 70% confluence (P1) for RNAseq transcriptome analysis. 477 genes were differentially expressed (DEGs); 300 upregulated and 177 downregulated in aged versus young. Interestingly, upregulated DEGs and protein-protein interactions were enriched in cytokine and chemokine-mediated signaling, including cytokine-cytokine receptor interactions, TNF signaling pathway, and chemokine activity (all p<10-5). Down-regulated DEGs and protein-protein interactions were enriched in the regulation of lipid biosynthesis, and fatty acid metabolism. Notably, P1 fibroblasts from young and aged skin expressed similar levels of genes that encode ECM structural proteins including collagens (42 genes expressed), proteoglycans (29 genes expressed), and glycoproteins (157 genes expressed). The above findings indicate that aging causes fibroblasts to acquire a cell-autonomous pro-inflammatory phenotype. In contrast, fibroblasts cultured from aged skin retain the capacity to express “youthful” levels of ECM structural genes, suggesting that diminished expression of these genes in vivoreflects adaptation to the aged dermal microenvironment.