Matrix stiffness induces epithelial mesenchymal transition phenotypes of human epidermal keratinocytes on collagen coated two dimensional cell culture

Purpose Keratinocytes are epithelial cells in epidermis tightly connected to each other by cell-cell junction. During the process of wound re-epithelization, these epithelial cells undergo significant phenotypic changes that are reminiscent of the EMT process occurring during development and tumor progression. As the wound healing progresses, the reepithelization is initiated by activation and migration of keratinocytes from the edges of the wound. As they migrate toward the wound center, keratinocytes set off from their laminin-rich niche, and are forced to experience the abrupt changes in ECM microenvironment consisting of fibronectin and collagen matrices with locally elevated stiffness along the interface of the blood clot and the granulation tissue layer. In this study, thus, we tried to elucidate the effect of alteration of ECM proteins and substrate stiffness in keratinocytes during wound re-epithelization. Methods We expose primary normal human epidermal keratinocytes (NHEK) to the culture microenvironment, rich in fibronectin or collagen with varying stiffness, to investigate the role of the physiochemical stimuli on induction of EMTlike changes in NHEKs. Results Our results show that a stiffer substrate coated with either fibronectin or collagen induces faster migration with elevated expressions of mesenchymal genes (vimentin, MMP1), and proteins (vimentin, FAK) while suppressing those of the epithelial origin (CK10, CK14, Fillagrin, and Ecadherin) when compared to the laminin coated surfaces. Conclusions Various physicochemical stimuli inherently present at the wounds must orchestrate to induce the EMT process in NHEKs, promoting the re-epithelization.