Regulation of fibroblast gene expression by keratinocytes in organotypic skin culture provides possible mechanisms for the antifibrotic effect of reepithelialization

Abstract

To investigate the mechanisms behind the antifibrotic effect associated with epidermal regeneration, the expression of 12 fibroblast genes important for the modulation of the extracellular matrix (ECM), as well as α-smooth muscle actin, was studied in a keratinocyte-fibroblast organotypic skin culture model. The study was performed over time during epidermal generation and in the presence or absence of the profibrotic factor transforming growth factor-β. the Presence of epidermal differentiation markers in the model was essentially coherent with that of native skin. Fibroblast gene expression was analyzed with real-time polymerase chain reaction after removal of the epidermal layer. After 2 days of air-exposed culture, 11 out of the 13 genes studied were significantly regulated by keratinocytes in the absence or presence of transforming growth factor-β. The regulation of connective tissue growth factor, collagen I and III, fibronectin, plasmin system regulators, matrix metalloproteinases and their inhibitors as well as α-smooth muscle actin was consistent with a suppression of ECM formation or contraction. Overall, the results support a view that keratinocytes regulate fibroblasts to act catabolically on the ECM in epithelialization processes. This provides possible mechanisms for the clinical observations that reepithelialization and epidermal wound coverage counteract excessive scar formation.