Fibroblast-derived matrix human skin equivalents reveal distinct roles for papillary and reticular fibroblasts in human skin barrier integrity and aging

The lipidic skin barrier can be compromised by skin aging, driven by internal and external factors. With age the reticular dermal layer increases, suggesting that changes in the dermal phenotype influences skin barrier integrity with age. Fibroblast-derived matrix human skin equivalents (FDMs) containing either papillary (Pfs) or reticular fibroblasts (Rfs) were generated and analyzed for epidermal differentiation, expression of lipid processing enzymes, stratum corneum (SC) lipid matrix structure, and barrier function. Compared to Rf-FDMs, Pf-FDMs exhibit improved epidermal differentiation, demonstrated by basal cell layer proliferation and organization, early differentiation and late differentiation. Further, the expression of several lipid processing enzymes increased in Pf-FDMs, indicating enhanced barrier structure. Intercellular lipid matrix organization differs between Pf-FDMs and Rf-FDMs. Rf-FDMs exhibit decreased long periodicity phase (LPP) repeat distances of the lipid lamellae, and altered relative abundances of ceramide subclasses within Cer [N], Cer [A], Cer [EO] and Cer [O] are found. Average ceramide chain length in Cer [N] and Cer [A] is decreased in Rf-FDMs, and higher percentages of monounsaturation in Cer [NS] are observed. In line, Rf-FDMs have increased transepidermal water loss (TEWL). Concluding, Pf-FDMs and Rf-FDMs resemble characteristics of young and aged skin, and demonstrate distinct roles for Pfs and Rfs in skin barrier integrity.