Compartment-specific expression of collagens and their processing enzymes in intrapulmonary arteries of IPAH patients

Alterations in extracellular matrix (ECM) have been implicated in the pathophysiology of pulmonary hypertension (PH). Here, we have undertaken a compartment-specific study to elucidate the expression profile of collagens and their processing enzymes in donor and IPAH pulmonary arteries. Predominant intimal, but also medial and perivascular remodeling and reduced lumen diameter were detected in IPAH pulmonary arteries. Two photon microscopy demonstrated accumulation of collagen fibers. Quantification of collagen in pulmonary arteries revealed collagen accumulation mainly in the intima of IPAH pulmonary arteries as compared to donors. Laser capture microdissected pulmonary artery profiles (intima+media and perivascular tissue) were analyzed by real-time PCR for ECM gene expression. In the intima+media of IPAH vessels, collagens (COL4A5, COL14A1 and COL18A1), matrix metalloproteinase (MMP) 19, and a disintegrin and metalloprotease (ADAM) 33 were higher expressed, whereas MMP10, ADAM17, TIMP1 and TIMP3 were less abundant. Localization of COLXVIII, its cleavage product endostatin and MMP10, ADAM33 and TIMP1 was confirmed in pulmonary arteries by immunohistochemistry. ELISA for collagen XVIII/endostatin demonstrated significantly elevated plasma levels in IPAH patients as compared to donors, while circulating MMP10, ADAM33 and TIMP1 levels were similar between the two groups. Endostatin levels were correlated with pulmonary arterial wedge pressure (PAWP), and established prognostic markers of IPAH, right atrial pressure (RAP), cardiac index (CI), six minute walking distance (6MWD), NT-proBNP and uric acid. Expression of unstudied collagens, MMPs, ADAMs and TIMPs were found to be significantly altered in IPAH intima+media. Elevated levels of circulating collagen XVIII/endostatin are associated with markers of a poor prognosis.