The rat model of pulmonary hypertension was induced by monocrotaline (MCT), and the intervention of potassium oxonate (OA) and benzbromarone (BBR) was used to investigate whether uric acid was involved in the occurrence and development of PAH by damaging the glycocalyx of pulmonary vascular endothelium and inducing the conversion of pulmonary vascular endothelial cells to mesenchymal cells (EndMT) leading to pulmonary vascular remodeling, in order to provide a scientific basis for the treatment of PAH with uric acid-lowering drugs.

1. Animal Grouping and Model Establishment

Twenty 2-month-old male SD rats were randomly divided into 4 groups : control group (CON group), pulmonary hypertension group (MCT group), hyperuricemia combined with pulmonary hypertension group (MCT+OA group), hyperuricemia combined with pulmonary hypertension and BBR intervention group (MCT+OA+BBR group), with 5 rats in each group. MCT group, MCT + OA group and MCT + OA + BBR group were established by single subcutaneous injection of MCT 60 mg / kg to establish pulmonary hypertension model. The control group was injected with equal volume of solvent A (solvent A was prepared by anhydrous ethanol and normal saline according to V/V=1:4, and the final concentration of ethanol was 20%). The MCT+OA group and MCT+OA+BBR group were fed with high yeast extract diet by intraperitoneal injection of OA 300mg/kg. The MCT+OA+BBR group was given BBR 10mg/kg daily by gavage. The control group and MCT group were given 0.5%CMC-Na by gavage.

2. Experimental Procedure and Sample Collection

The rats in each group were fasted overnight at the end of the 0th, 1st, 2nd, 3rd, and 4th weeks. After isoflurane inhalation anesthesia, blood was collected from the inner canthus to detect three indicators of renal function (uric acid, creatinine, urea nitrogen). At the end of the 4th week, the survival rate of rats in each group was recorded, and the right ventricular systolic pressure (RVSP) and right ventricular hypertrophy index (RVHI) were detected and calculated. Lung tissue was stained with HE to observe the pathological changes of lung tissue. The percentage of lumen area of pulmonary arterioles to total vascular area (VA%) and the percentage of wall area to total vascular area (WA%) were measured.

3. Molecular Biological Assays

Immunohistochemistry (IHC) and Western blot were used to detect the expression levels of α-smooth muscle actin (α-SMA), vascular endothelial cadherin (VE-cadherin), CD-31 and von Willebrand factor (VWF) in lung tissue. Enzyme-linked immunosorbent assay (ELISA) was used to detect the concentration of syndecan-1 in plasma.

1. Successfully constructed PAH rat model :

(1) There was no death in each group during the experiment, and the survival rate was 100%.

(2) At the end of the 4th week of the experiment, compared with CON group, RVSP in MCT group, MCT+OA group and MCT+OA+BBR group were significantly increased (P<0.05). Compared with CON group, RVHI in MCT group, MCT+OA group and MCT+OA+BBR group were significantly increased (P<0.05) .

(3) At the end of the 4th week of the experiment, the rats in each group were dissected, and the lung tissue was stained with HE. The pathology of the lung tissue of each group was observed : uniform vascular wall was observed in the lung tissue of the CON group, and there was no obvious stenosis, thickening and inflammatory cell infiltration. In the lung tissue of rats in the MCT group, the vascular wall was thickened, the lumen was narrowed, and inflammatory cell infiltration was seen around it ; in MCT+OA group and MCT+OA+BBR group, the vascular wall was significantly thickened, the lumen was significantly narrowed, the lumen was occluded, and a large number of inflammatory cells and foam cell infiltration were seen around the lung tissue.

(4) Compared with CON group, WA% and WT% in MCT group, MCT+OA group and MCT+OA+BBR group were significantly increased (P<0.05);

(5) The results of immunohistochemical staining showed that there were significant differences in the expression of α-SMA in lung tissue of rats in each group. In MCT group, MCT+OA group and MCT+OA+BBR group, the positive expression of α-SMA in pulmonary vascular wall was significantly enhanced, and different degrees of lumen stenosis, wall thickening and even lumen occlusion occurred in small vessels with vascular diameter OD100-500μm or OD<100μm.

2.RVSP and RVHI were significantly higher in the MCT+OA group than in the MCT group, indicating that hyperuricemia exacerbates PAH severity.

3.Pathological analysis showed WA% and WT% were significantly higher in MCT+OA vs. MCT group (P<0.05), suggesting hyperuricemia aggravates vascular remodeling. WA% and WT% were significantly lower in MCT+OA+BBR vs. MCT+OA group (P<0.05), indicating BBR intervention partially reversed hyperuricemia-aggravated remodeling.

4.Plasma syndecan-1 concentration was significantly elevated in MCT, MCT+OA, and MCT+OA+BBR groups vs. CON group (P<0.05), confirming glycocalyx shedding in MCT-induced PAH. Although syndecan-1 showed a decreasing trend after BBR intervention compared to the MCT+OA group, the difference was not statistically significant, suggesting BBR may not effectively prevent glycocalyx shedding during PAH/hyperuricemia.

5.Western blot analysis showed that endothelial markers (VWF, VE-cadherin) were significantly decreased, while the mesenchymal marker (α-SMA) was significantly increased in the MCT+OA group, indicating chronic hyperuricemia promotes EndMT. BBR intervention partially reversed this process (increased VWF/VE-cadherin, decreased α-SMA) and alleviated vascular remodeling.

1．This study confirmed glycocalyx shedding and EndMT occur in the pulmonary vasculature of MCT-induced PAH rats.

2．Hyperuricemia may be a factor exacerbating PAH, potentially via inducing glycocalyx shedding and EndMT, thereby aggravating pulmonary vascular remodeling. Urate-lowering therapy (e.g., with benzbromarone) shows promise as a novel strategy for treating vascular remodeling in PAH.