Focal adhesion kinase and reactive oxygen species contribute to the persistent fibrotic phenotype of lesional scleroderma fibroblasts

Objective. Fibrotic diseases such as SSc (systemic sclerosis, scleroderma) are characterized by the abnormal presence of the myofibroblast, a specialized type of fibroblast that overexpresses the highly contractile protein alpha-smooth muscle actin. Myofibroblasts display excessive adhesive properties and hence exert a potent mechanical force. We aim to identify the precise contribution of adhesive signalling, which requires integrin-mediated activation of focal adhesion kinase (FAK)/src, to fibrogenic gene expression in normal and fibrotic SSc fibroblasts. Methods. We subject either FAK wild-type and knockout fibroblasts or normal and SSc fibroblasts treated with FAK/src inhibitors to real-time polymerase chain, western blot, cell migration and collagen gel contraction analyses. Results. FAK operates downstream of both integrin beta 1 and reactive oxygen species (ROS) to promote the expression of genes involved in matrix production and remodelling, including CCN2, alpha-smooth muscle actin and type I collagen. Blocking either FAK/src with PP2 or ROS with N-acetyl cysteine alleviates the elevated contractile and migratory capability of lesional SSc dermal fibroblasts. Conclusions. Excessive adhesive signalling is intimately involved with the fibrotic phenotype of lesional SSc fibroblasts; blocking adhesive signalling or ROS generation may be beneficial in controlling the fibrosis observed in SSc.