The Integrin-Mediated Focal Adhesion Is Critically Involved in the Macrophage-to-Myofibroblast Transition in Subretinal Fibrosis.

Fibrosis, a common end point of chronic inflammatory diseases across organs, remains a major therapeutic challenge. Macrophages are central regulators of fibrotic remodeling, with evidence suggesting their direct role through macrophage-to-myofibroblast transition. However, the upstream mechanisms governing macrophage fibrogenic reprogramming remain unclear. Using a laser-induced mouse model of subretinal fibrosis, whether adhesion-dependent mechanotransduction regulates macrophage-driven fibrosis was investigated. Bulk RNA sequencing of retinal pigment epithelium-choroid tissues revealed significant enrichment of adhesion-related genes and focal adhesion pathways, with up-regulation of integrins such as Itgb2, Itgal, and Itgax. Increased integrin expression and focal adhesion kinase (FAK) phosphorylation were detected in infiltrating F4/80+ macrophages within fibrotic lesions. Bone marrow-derived macrophages under high adherence conditions expressed higher levels of fibrosis-related genes and FAK-related genes such as Ptk2 and Ptk2b. FAK inhibitor PF562271 suppressed transforming growth factor-β1-induced up-regulation of fibrosis-related genes (Col1a1, Fn1, and Acta2) and α-smooth muscle actin in macrophages. I.P. administration of PF562271 reduced expression of adhesion molecules ITGB2 and ITGAL on circulating monocytes and alleviated subretinal fibrosis. These findings identify integrin-FAK-mediated mechanotransduction as a key regulator of macrophage fibrogenic reprogramming and macrophage-to-myofibroblast transition. Adhesion-dependent signaling is highlighted as a conserved pathway linking tissue remodeling to fibrotic macrophage activation and FAK as a potential therapeutic target.