Narrative review on expression of non-coding RNA in biofluids in conditions associated with couple infertility

Couple infertility poses a health challenge, prompting research into its multifaceted aetiology. Non-coding RNA (ncRNA) expression has emerged as a candidate for elucidating couple infertility. This review explores the roles of small and long ncRNA in biofluids in conditions associated with couple infertility. This review summarized data on ncRNA profiles in plasma, serum and follicular fluid for infertile women; and in plasma, serum and seminal plasma for infertile men. For female infertility, a salivary microRNA (miRNA) signature has been shown to enable the diagnosis of endometriosis-associated infertility. For primary ovarian insufficiency and diminished ovarian reserve, several studies have demonstrated the diagnostic value of plasma miRNA, but little is known regarding the role of circular RNA (circRNA) and long non-coding (lncRNA) biofluid expression. For polycystic ovary syndrome (PCOS), a combination of five miRNA can be used to distinguish between obese women with and without PCOS (accuracy 84%). For male infertility, seminal plasma analyses have demonstrated the diagnostic value of miRNA expression to diagnose male infertility and its theragnostic value before surgery. Moreover, expression of Piwi-interacting RNA, circRNA, transfer RNA and lncRNA in seminal plasma supports their theragnostic value. In conclusion, evidence supports the relevance of ncRNA expression in biofluids to diagnose and manage couple infertility, but further studies are required before routine use.