Development and Characterization of a Novel Chronic Thromboembolic Pulmonary Hypertension Rat Model: Identifying Sell-Podxl as Potential Regulators

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.