Objective: To study the roles of integrin alpha(5)beta(1) played in rat pulmonary fibrosis.
Methods: The dynamic changes of fibronectin (FN), FN receptor alpha(5)beta(1), and TGF-beta were analysed in bleomycin-induced rat pulmonary fibrosis by using immunohistochemical technique. Northern blot analysis and immunocytochemistry techniques were performed in order to detect the expression of alpha(5)beta(1), FN mRNA and their relevant proteins in cultured rat pulmonary fibroblasts (PFbs) after administration of TGF-beta1.
Results: (1) A strong positive reaction with anti-integrin alpha(5)beta(1) was seen in the pneumocytes, endothelial cells and proliferated mesenchymal cells on the 1st to 3rd day after bleomycin. The positive signals for integrin alpha(5)beta(1) were apparent mainly in those proliferated interstitial cells with fibroblast and myofibroblast differentiation 7 days after bleomycin treatment. Changes in FN were similar to that of the integrin alpha(5)beta(1). (2) Expression of alpha(5)beta(1), FN mRNAs and their relevant proteins was increased in rat PFbs after TGF-beta1 administration.
Conclusions: Integrin alpha(5)beta(1) played a key role in inducing the activation, proliferation and differentiation of PFbs, causing an increase of extra-cellular matrix synthesis during pulmonary fibrogenesis.