EDA‐containing cellular fibronectin induces fibroblast differentiation through binding to α 4 β 7 integrin receptor and MAPK/Erk 1/2‐dependent signaling

Abstract

Fibroblast differentiation is an essential step during wound healing and fibrosis. Fibronectin (FN) is a major component of the extracellular matrix and occurs in two main forms: plasma and cellular FN. The latter includes the alternatively spliced domain A (EDA). Although EDA‐containing cellular fibronectin (EDA‐FN) is associated with fibroblast differentiation, how EDA‐FN promotes differentiation is incompletely understood. In this study, we investigate the mechanism by which EDA‐FN contributes to fibroblast differentiation with emphasis on the characterization of the EDA‐FN receptor. We show that EDA‐FN increases α‐SMA expression (immunofluorescence), collagen deposition, cell contractility, and focal adhesion kinase (FAK) activation (immunoblotting); whereas plasma FN, a form lacking EDA, shows no effect. Primary lung fibroblasts constitutively express α 4 β 7 integrin receptor (FACS and RT‐PCR). Blocking of α 4 β 7 reduces fibroblast adhesion to EDA‐FN and inhibits α‐SMA expression, collagen deposition, and FAK activation induced by EDA‐FN. Using recombinant EDA‐containing peptides, we demonstrate that the EDA segment is sufficient to induce fibroblast differentiation via binding to α 4 β 7 . EDA‐FN induces MAPK‐Erk1/2 activation and inhibition of MEK1/2 attenuates EDA‐FN‐induced α‐SMA expression. Our findings demonstrate that EDA‐FN induces fibroblast differentiation by a mechanism that involves binding of EDA to α 4 β 7 integrin followed by activation of FAK and MAPK‐associated signaling pathways.— Kohan, M., Muro, A. F., White, E. S., Berkman, N. EDA‐containing cellular fibronectin induces fibroblast differentiation through binding to α 4 β 7 integrin receptor and MAPK/Erk 1/2‐dependent signaling. FASEB J . 24, 4503–4512 (2010). www.fasebj.org