Sperm quality, reproductive hormones, and membrane-bound progesterone receptor expression in Chinese sturgeon...

Chinese sturgeon (Acipenser sinensis), a critically endangered fish species, faces significant challenges in artificial propagation, with sperm quality being a key limiting factor. This study investigated the relationships among sperm quality parameters, serum reproductive hormone concentrations, and the expression of membrane-bound progesterone receptors (membrane progestin receptor α (mprα) and progesterone receptor membrane component 1 and 2 (pgrmc1 and pgrmc2)) in sexually mature male Chinese sturgeon during the spawning season. Computer-assisted sperm analysis (CASA) revealed that the normospermic group exhibited significantly higher sperm motility, A-grade sperm proportion, and mean angular displacement (MAD) than the asthenospermic group. Serum hormone assays showed that the concentrations of 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-DHP), 11-keto testosterone (11-KT), and luteinizing hormone (LH) were markedly elevated in the normospermic group. Molecular identification and bioinformatics analysis confirmed the presence of mprα, pgrmc1, and pgrmc2 in Chinese sturgeon, revealing their structural characteristics and high conservation across vertebrates. Tissue distribution analysis demonstrated sex-specific expression patterns of these genes across various tissues (pituitary, gonad, liver, heart, skin, intestine, and gill) in two-year-old fish. Notably, mRNA expression levels of these genes were significantly down-regulated in the asthenospermic group. These findings suggest that impaired progesterone signaling and endocrine dysregulation may contribute to reduced sperm motility. Our results provide foundational insights into the role of membrane-bound progesterone receptors in Chinese sturgeon reproduction, offering potential biomarkers for sperm quality assessment and targets for improving artificial breeding strategies in this endangered species.