Development and Characterization of a Novel Chronic Thromboembolic Pulmonary Hypertension Rat Model: Identifying...

Chronic thromboembolic pulmonary hypertension is characterized by proximal pulmonary artery obstruction and distal microvasculopathy. However, the mechanisms driving this dual-compartment pulmonary vascular remodeling remain unclear.

Male Sprague-Dawley rats were injected with gelatin sponge combined with SU5416 as a secondary insult. Hemodynamics, echocardiography, and pulmonary vascular remodeling were evaluated to investigate the development of chronic thromboembolic pulmonary hypertension. Single-cell RNA sequencing of rat lung tissue was conducted to elucidate the molecular mechanisms underlying pulmonary vascular remodeling. The results were validated by immunofluorescence and cell-based experiments.

The optimal size range of gelatin sponge for large pulmonary artery obstruction was 710 to 1000 µm, which synergized with a low dose of SU5416 (10 mg/kg) to induce significant increases in right ventricular systolic pressure and right ventricular hypertrophy at 5 weeks. The model exhibited persistent elastic pulmonary artery obstruction and remodeling, along with significant wall thickening and muscularization of pulmonary microvessels. Single-cell transcriptomic analysis revealed a significant reduction in microvascular endothelial cells and an increase in smooth muscle cells in the chronic thromboembolic pulmonary hypertension rats. STAT3, EGR1, and HIF1A were identified as key genes driving aberrant smooth muscle cell proliferation. The Sell (encoding L-selectin)-Podxl (encoding PODXL, podocalyxin) ligand-receptor pair was found specifically in diseased rats and mediated immune cell-endothelial cell interactions. L-selectin promoted neutrophil adhesion and dysfunction in pulmonary arterial and microvascular endothelial cells, both of which were reversed by PODXL knockdown.

Our new model recapitulates human chronic thromboembolic pulmonary hypertension pathophysiology and is useful for understanding pulmonary microvasculopathy. Sell-Podxl is a previously unrecognized link between inflammation and vascular remodeling, offering a potential therapeutic target.