Role of Tissue-Type Plasminogen Activator in Remodeling of the Ductus Arteriosus.

Vascular remodeling (e.g., intimal thickening) is necessary for complete closure of the ductus arteriosus (DA). Smooth muscle cells are reported to contribute to DA remodeling. In contrast, the contribution of endothelial cells remains largely unknown. Recent data showed that tissue-type plasminogen activator (t-PA) was highly expressed in the endothelial cells of rat and human DA. It is well known that t-PA is an activator of the blood fibrinolytic system, but t-PA-induced localized proteolysis has been reported to play an important role in vascular development. We found that t-PA-induced plasminogen-plasmin conversion promoted matrix metalloproteinase-2 activation in endothelial cells of rat DA. Gelatinase activity was noted at the internal elastic laminae (IEL) of rat and human DA on in situ gelatin zymography. The in vivo injection of plasminogen to pre-term rats increased gelatinase activation, IEL disruption, and the subsequent intimal thickening formation in the pre-term rat DA. Human DA results partly supported the rat DA findings, suggesting that t-PA-mediated DA remodeling may also be present in the human DA. Current pharmacotherapy for patent DA (PDA) mainly focuses on increasing vascular constriction. Elucidating the molecular mechanisms of DA remodeling may help to expand the range of therapeutic strategies for PDA.