Epidermal growth factor signalling mediates keratinocyte mechanoregulation

The mechanical environment regulates proliferation, migration and differentiation in multiple cell types; however, the effects on human keratinocytes are not fully understood. The aim of this work was to investigate the influences of matrix stiffness on epidermal keratinocytes. Primary human keratinocytes were cultured using polydimethylsiloxane (PDMS) substrates in which the elastic moduli can be altered within a physiologically relevant range by varying the ratio of crosslinker to base polymer. Cells cultured on substrates with a higher elastic modulus (2.16 MPa) demonstrated increased colony-forming efficiency compared with those on softer substrates (180 kPa). There were no changes in terminal differentiation, spreading or adhesion between conditions; however, a decrease in apoptosis and a small increase in proliferation were observed on the stiffer PDMS substrates. The effects of substrate stiffness on keratinocyte growth and survival were regulated by activation of the epidermal growth factor receptor (EGFR) through cross-talk with focal adhesions and cytoskeletal tension. Microarray analysis of the downstream changes in gene expression further identified focal adhesions and phosphatidylinositol signalling as key pathways regulated by matrix stiffness. Finally, preliminary studies on human keloid skin samples revealed increased pEGFR activation within the stiff scar tissue compared with the softer extralesional areas, suggesting an in vivo mechanosensitive response. Together, these studies demonstrate that matrix stiffness controls keratinocyte growth and survival via the EGF signalling pathway and may play an important role in wound healing and scar formation.

Published in: British Journal of Dermatology, 174(5), pp. e43-e74.