Distribution of extracellular matrices, matrix receptors, and transforming growth factor-beta 1 in human and experimental lung granulomatous inflammation

Abstract

Aberrant deposition of extracellular matrices (ECMs) may affect lung inflammation by influencing cell adhesion, migration, and activation. Little is known about the expression of ECMs in lungs with granulomatous inflammation. Therefore the authors investigated the distribution of ECMs, matrix receptors of the integrin family, and transforming growth factor-beta 1 (TGF-beta 1) in lungs from patients with pulmonary sarcoidosis and animals with experimental granulomatosis. Immunohistochemistry revealed increased deposition of type I collagen and fibronectin in human lung granulomas when compared with healthy human lungs. Procollagen type I and cellular fibronectin also were increased, suggesting local synthesis of ECM in sarcoid granulomas. These findings were accompanied by increased staining for fibronectin (alpha 5 beta 1) and collagen (alpha 2 beta 1) integrin receptors. The matrix-inducing cytokine TGF-beta 1 was co-distributed with the aforementioned molecules in the granulomas, whereas no significant staining for TGF-beta 1 was found in healthy lungs. Similar to sarcoid lungs, analysis of lung sections obtained from a murine model of granuloma formation revealed increased expression of fibronectin, collagen, integrin receptors, and TGF-beta 1 within granulomas. Based on these observations, there is increased expression of ECM and matrix receptors in both human and experimental lung granulomas. Such alterations may influence the recruitment and activation of inflammatory cells and fibroblasts, promoting granuloma formation and remodeling of tissue by fibrosis. Activation of mononuclear cells resulting in production of TGF-beta 1 is likely to contribute to the changes described.