EDA-containing cellular fibronectin induces fibroblast differentiation through binding to α4β7 integrin receptor and MAPK/Erk 1/2-dependent signaling

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 alpha-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 alpha(4)beta(7) integrin receptor (FACS and RT-PCR). Blocking of alpha(4)beta(7) reduces fibroblast adhesion to EDA-FN and inhibits alpha-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 alpha(4)beta(7). EDA-FN induces MAPK-Erk1/2 activation and inhibition of MEK1/2 attenuates EDA-FN-induced alpha-SMA expression. Our findings demonstrate that EDA-FN induces fibroblast differentiation by a mechanism that involves binding of EDA to alpha(4)beta(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 alpha(4)beta(7) integrin receptor and MAPK/Erk 1/2-dependent signaling. FASEB J. 24, 4503-4512 (2010). www.fasebj.org