Propeptide levels of type III and type I procollagen in the serum and bronchoalveolar lavage fluid of patients with pulmonary sarcoidosis

No single test is available to reliably assess the activity or prognosis of pulmonary sarcoidosis. In this study, we have evaluated two procollagen markers, aminoterminal propeptide of type III procollagen (PIIINP) and carboxyterminal propeptide of type I procollagen (PICP) in serum and bronchoalveolar lavage fluid (BALF) and compared them to other disease markers of pulmonary sarcoidosis, such as serum level of angiotensin converting enzyme (S-ACE) or serum interleukin-2 receptor (S-IL-2R). Bronchoalveolar lavage was performed in 40 sarcoidosis patients without (stages 0-I) and 20 patients with lung parenchymal involvement (stages II-III), as well as in 17 controls. Serum (S)- and BALF-PIIINP and PICP, S-ACE, S-IL-2R, BALF-albumin, BALF-lymphocytes and mast cells were determined in these patients. BALF-PIIINP was clearly and S-PIIINP slightly elevated in sarcoidosis compared to the controls. Similarly BALF-PICP, but not S-PICP, was significantly higher in sarcoidosis. BALF-PIIINP, but not BALF-PICP correlated with S-ACE and S-IL-2R levels. Patients with lung parenchymal disease had higher S-ACE and BALF-PIIINP, but neither S-IL-2R, S-PIIINP nor S- or BALF-PICP were elevated. S-PIIINP and S-IL-2R but not S-ACE were higher in symptomatic than nonsymptomatic patients. Symptomatic patients with parenchymal disease had elevated BALF-PIIINP whereas in the symptomatic nonparenchymal group S-PIIINP was elevated. In conclusion, this is the first study to evaluate carboxyterminal propeptide of type I procollagen in sarcoidosis and showed elevated levels in bronchoalveolar lavage fluid. In contrast to the levels of bronchoalveolar lavage fluid aminoterminal propeptide of type III procollagen, levels of carboxyterminal propeptide of type I procollagen did not correlate with serum level of angiotensin converting enzyme and serum interleukin-2 receptor levels, suggesting that carboxyterminal propeptide of type I procollagen may be less suitable disease marker in sarcoidosis than aminoterminal propeptide of type III procollagen. However, the role of carboxyterminal propeptide of type I procollagen as an indicator of fibrogenesis must be further studied.

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