Effects of valproic acid exposure on sperm mitochondria and sncRNA profiles in male mice

Background: Valproic acid (VPA) is a broad-spectrum antiepileptic drug with potential adverse effects on male reproductive health. Materials and methods: In this study, we established a mouse model to investigate the reproductive consequences of low-dose VPA exposure. Male mice were administered VPA at 200 mg/kg for 35 days. Ultrastructural analysis was used for histological examination. Small RNA microarray profiling was used to determine the expression changes after VPA exposure. Results: Valproic acid exposure increased testicular weight but had no significant effects on body weight, epididymal size, or conventional sperm parameters, and no obvious histological abnormalities were observed. Despite the absence of overt changes in these routine reproductive indices, ultrastructural analysis revealed pronounced mitochondrial swelling in sperm, accompanied by evidence of metabolic dysfunction. Small RNA microarray profiling further demonstrated that VPA exposure altered the sperm small RNA landscape and identified a false discovery rate-significant subset of differentially expressed transfer RNA (tRNA)-derived small RNAs. Notably, 6 of these tRNA-derived small RNAs were derived from mitochondrial tRNAs, 5 of which were downregulated. Together, these findings indicate that low-dose VPA exposure induces sperm mitochondrial abnormalities and selectively alters sperm mitochondrial tRNA-derived small RNAs, with downregulation predominating among the false discovery rate-significant species. Conclusions: This study provides new insights into the molecular basis of VPA-induced male reproductive toxicity and suggests that sperm mitochondrial tRNA-derived small RNAs may serve as sensitive molecular indicators of drug-induced perturbations in male reproductive health.