Direct thrombin inhibitors as alternatives to heparin to preserve lung growth and function in a murine model of compensatory lung growth

Infants with congenital diaphragmatic hernia (CDH) may require cardiopulmonary bypass and systemic anticoagulation. Expeditious lung growth while on bypass is essential for survival. Previously, we demonstrated that heparin impairs lung growth and function in a murine model of compensatory lung growth (CLG). We investigated the effects of the direct thrombin inhibitors (DTIs) bivalirudin and argatroban. In vitro assays of lung endothelial cell proliferation and apoptosis were performed. C57BL/6 J mice underwent left pneumonectomy and subcutaneous implantation of osmotic pumps. Pumps were pre-loaded with normal saline (control), bivalirudin, argatroban, or heparin and outcomes were assessed on postoperative day 8. Heparin administration inhibited endothelial cell proliferation in vitro and significantly decreased lung volume in vivo, while bivalirudin and argatroban preserved lung growth. These findings correlated with changes in alveolarization on morphometric analysis. Treadmill exercise tolerance testing demonstrated impaired exercise performance in heparinized mice; bivalirudin/argatroban did not affect exercise tolerance. On lung protein analysis, heparin decreased angiogenic signaling which was not impacted by bivalirudin or argatroban. Together, this data supports the use of DTIs as alternatives to heparin for systemic anticoagulation in CDH patients on bypass. Based on this work, clinical studies on the impact of heparin and DTIs on CDH outcomes are warranted.