Extracellular Matrix Components in Bronchoalveolar Lavage Fluid in Sarcoidosis and Their Relationship to Signs of Alveolitis

Abstract

In lung sarcoidosis, the mutual relationships of three components of the extracellular matrix, fibronectin (FN), hyaluronan (HA), and type III procollagen peptide (PCP), were investigated in the bronchoalveolar lavage (BAL) fluid. Furthermore, their relation to signs of alveolitis and of fibrosis was examined. Sarcoidosis patients (n = 74) had significantly (p less than 0.001) increased BAL fluid concentrations of FN, HA, and PCP, as well as albumin and lymphocytes, compared to controls (n = 57). The increases were significantly higher in clinically active than in inactive sarcoidosis. FN, HA, and PCP were significantly correlated to markers of alveolitis, such as albumin (r approximately 0.6-0.7; p less than 0.001) and lymphocytes (r approximately 0.4-0.5; p less than 0.001 for FN and HA; p less than 0.05 for PCP), indicating that an alveolar inflammatory process may be a prerequisite for the increased production of the three components. Since correlations between FN and HA and functional parameters (VC, TLC, FEV1.0, and DLCO) were low (r approximately 0.2-0.3, p less than 0.05-0.01 for FN and HA), the increased levels of the extracellular markers do not seem to reflect developed fibrosis. The three markers of extracellular matrix showed significant (p less than 0.001) mutual correlations in the sarcoid patients (r approximately 0.7). FN and HA were correlated even in controls (r = 0.5; p less than 0.01). The findings are in agreement with our hypothesis that these compounds may participate in the buildup of an extracellular network that supports the healing process but in excess may eventually lead to fibrosis.