TXNDC5 Governs Extracellular Matrix Homeostasis in Pulmonary Hypertension

BACKGROUNDPulmonary hypertension (PH) is characterized by vascular remodeling without effective treatments. Thioredoxin domain containing 5 (TXNDC5), a member of the protein disulfide isomerases (PDI) family, regulates protein folding and vascular homeostasis, yet its role in PH remains unknown. METHODSLabel-free proteomics profiled protein expression in lungs from PH patients. TXNDC5 was analyzed by single-cell RNA sequencing, immunofluorescence, and Western blot. Endothelial gain- and loss-of-function approaches were applied in Sugen5416/hypoxia (SuHx)-induced rodent PH models. RNA sequencing and protein-protein interaction analysis were used to investigate underlying mechanisms. RESULTSTXNDC5 was significantly upregulated in the lungs of patients with PH and in experimental PH models, with predominant localization in endothelial cells (ECs) of remodeled distal pulmonary arteries. Endothelial TXNDC5 overexpression exacerbated pulmonary vascular remodeling, elevated right ventricular systolic pressure, and promoted right ventricular hypertrophy, whereas global or endothelial-specific TXNDC5 deficiency conferred protection against SuHx-induced PH. Hypoxia-induced factor (HIF)-2 transcriptionally activated TXNDC5 to drive PH development. Single-cell RNA sequencing identified a distinct subpopulation characterized by TXNDC5high extracellular matrix (ECM)-producing ECs. Bulk RNA sequencing combined with protein-protein interaction analysis revealed that TXNDC5 regulated ECM homeostasis through biglycan (BGN). Pharmacological inhibition of TXNDC5 with E64FC26 and endothelial-targeted TXNDC5 gene therapy significantly attenuated PH severity in rats. CONCLUSIONSOur study reveals that TXNDC5 is a main modulator to regulate ECM homeostasis and may serve as a promising target for the treatment of PH.