Transforming growth factor-β1 in sarcoidosis

Transforming growth factor-beta (TGF-beta) is a cytokine that promotes extracellular matrix accumulation and inhibits matrix degradation. Although the natural course of sarcoidosis is usually favourable, granuloma healing in the lung may result in pulmonary fibrosis and respiratory impairment in some patients. In this study TGF-beta(1) was evaluated in bronchoalveolar lavage (BAL) fluid and culture supernatants of alveolar macrophages (AM) from 73 patients with biopsy-proven sarcoidosis. Disease activity was defined when patients recently developed or increased symptoms (cough, dyspnoea, systemic symptoms) and/or demonstrated increasing opacities on chest radiography, Pulmonary function tests were performed in all patients including forced expiratory volume in one second (FEV1), forced vital capacity (FVC), total lung capacity (TLC) and the diffusing capacity of the lung for carbon monoxide (DL,CO), Fourteen patients with idiopathic pulmonary fibrosis (IPF) and 14 healthy subjects were investigated as a control group, Immunohistochemistry was used to evaluate the cell distribution of TGF-beta(1), on lung specimens. TGF-beta(1), levels in BAL and in AM supernatants were not different between sarcoidosis and healthy subjects, whereas they were markedly increased in IPF, However, the TGF-beta(1) level was significantly increased in BAL fluid but not in AM supernatants from sarcoidosis with altered lung function, compared with patients with normal lung function. The TGF-beta(1) level in BAL was increased in active sarcoidosis but this increased level was mainly related to the higher level observed in patients with altered lung function. TGF-beta(1) levels in BAL correlated significantly with the lymphocyte percentage, TGF-beta(1) staining assessed by immunohistochemistry was intense in epithelioid histiocytes comprising non-necrotizing granuloma and in bronchiolar epithelial cells, in hyperplastic type II pneumocytes and occasionally in AM, This study supports the hypothesis that overproduction of transforming growth factor-beta(1) is associated with functional impairment in patients with pulmonary sarcoidosis.