Abstract

Summary Background Hydrosalpinx affects 10–30% of infertile women, creating a hostile tubal microenvironment that impairs embryonic development. Although fluid embryotoxicity is recognised, specific toxic metabolites and their molecular mechanisms remain elusive. Methods We performed untargeted metabolomics on fallopian tube fluid from 49 patients with hydrosalpinx and 52 controls. The functional impact of the identified key metabolite, inosine, was validated in mouse embryos both in vivo and in vitro . Mechanisms were deciphered using integrated transcriptome and translatome sequencing (T&T-seq), and the inosine-induced embryonic arrest was rescued by the purine nucleoside phosphorylase (PNP) inhibitor forodesine and si PNP . Findings Purine metabolism was the most significantly upregulated pathway in hydrosalpinx fluid, with inosine being a highly elevated metabolite. Functional studies demonstrated that inosine induced a developmental arrest at the 2- to 4-cell stage in mouse embryos. Multi-omics analysis revealed that inosine disrupted the maternal-to-zygotic transition (MZT) and significantly reduced global translation efficiency, leading to cytoskeletal dysfunction and suppression of zygotic genome activation. Critically, both the PNP inhibitor forodesine and si PNP partially rescued the inosine-induced embryonic arrest. Interpretation Our findings establish inosine accumulation as a key metabolic cause of embryonic arrest in hydrosalpinx, functioning through the disruption of translation efficiency and the MZT process. This study not only provides a mechanistic understanding of tubal factor infertility but also highlights the PNP pathway as a potential target for non-surgical interventions to improve fertility. Funding National Key R&D Program of China (2022YFC2702204 and 2023YFA1800300), National Natural Science Foundation of China (NSFC) under the Youth Student Basic Research Project (Grant No. 825B2046), and NSFC (82201838 and 82495190).