Application of murine hindlimb deep vein thrombosis model to assess temporal evolution and hemodynamic sequelae of pulmonary embolism.

Abstract

Pulmonary embolism (PE) remains a leading cause of cardiovascular mortality worldwide. However, the natural course of embolized thrombi and the organization process to initiate chronic thromboembolic pulmonary hypertension (CTEPH) lesions remain poorly understood, due to the lack of experimental models that reproduce clinical features of acute PE in humans. Building on our previous murine saphenous deep venous thrombosis (DVT) model, our PE model enabled thrombus embolization from endogenously formed DVT in the hindlimb vein, whereas conventional animal PE models are based on the injection of ex vivo clot. We evaluated the temporal remodeling of emboli structure and the associated hemodynamic impairment following acute PE. Multiple embolized thrombi were successfully visualized in the whole lung with fluorescence microscopy using an ultra-low-magnification objective, allowing assessment of the incidence and severity of PE. Ex vivo imaging of embolized thrombi revealed a gradual platelet accumulation within hours of PE induction. The combination of repeated PE and chronic hypoxia (10% oxygen, 3 weeks) resulted in marked elevation of right ventricular pressure. Molecular analysis demonstrated a significant upregulation of pro-inflammatory markers and HIF-1α in hypoxic mice with PE. Ultimately, our model enabled the evaluation of the natural course of embolized thrombi in the pulmonary artery and could recapitulate the clinical features of acute human PE both with and without hemodynamic compromise, providing a valuable platform for mechanistic and therapeutic investigations of acute PE and CTEPH.