Characterization of long non-coding RNA and messenger RNA profiles in follicular fluid from mature and immature ovarian follicles of healthy women and women with polycystic ovary syndrome

STUDY QUESTION: Do long non-coding RNA (lncRNA) and messenger RNA (mRNA) profiles in follicular fluid from mature and immature ovarian follicles differ between healthy women and women with polycystic ovary syndrome (PCOS)? SUMMARY ANSWER: lncRNA and mRNA profiles in follicular fluid from both mature and immature ovarian follicles differed significantly between healthy women and PCOS patients. WHAT IS KNOWN ALREADY: Unlike microRNAs, which have been extensively studied, lncRNAs present in follicular fluid have never been sequenced and the biological associations of lncRNAs in healthy follicles and follicles in women who develop PCOS remain largely unknown. STUDY DESIGN, SIZE, DURATION: A total of 18 subjects (8 controls and 10 PCOS patients) were recruited to participate in this study. Recruitment took place from May 2016 to September 2016. PARTICIPANTS/ MATERIALS, SETTING, METHODS: The follicular fluid donors underwent their first round of in-vitro fertilization treatment. Follicle size was determined based on the average follicular diameter, and follicular fluid samples were collected from mature follicles (17-22 mm) and matched-immature follicles (8-13 mm). RNA sequencing was performed on follicular fluids from mature and immature follicles of healthy women and PCOS patients. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 1583 novel lncRNAs were identified in 36 human follicular fluid samples and some were expressed differently in healthy and PCOS women. lncRNAs associated with the metabolic process were highly enriched in the follicular fluid of mature follicles from the PCOS group versus the healthy group. In the PCOS group, nervous system process lncRNAs were highly enriched in the follicular fluid of mature versus immature follicles, whereas in the healthy group, lncRNAs associated with junction adhesion and communication-related processes were highly enriched in the follicular fluid of mature versus immature follicles. In addition, differentially expressed mRNAs were principally linked to olfactory transduction pathways. Consistent results from Gene Set Enrichment Analysis (GSEA) and Gene Ontology (GO) indicated that telomere maintenance and MAPK and Wnt pathways may be conserved processes, active in follicular development, and monosaccharide biosynthesis might provide possible pathway markers to distinguish between normal and PCOS follicles. We constructed gene co-expression networks that identified many co-regulatory relationships among follicular fluid lncRNAs, mRNAs, and PCOS phenotypes. Weighted Gene Co-expression Network Analysis (WGCNA) revealed lncRNAs and mRNAs that were core and others associated with the PCOS phenotype. LIMITATIONS, REASONS FOR CAUTION: It remains unclear whether these differential transcripts contribute directly to follicular development or the pathogenesis of PCOS, or are merely biomarkers. WIDER IMPLICATIONS OF THE FINDINGS: It will be important in the future for investigators to ascertain the biologic mechanisms underlying the development of both normal and PCOS follicles. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the National Natural Science Foundation of China (No. 81671423, No. 81402130 and No. 81501247), the Fok Ying Tung Education Foundation (No. 151039), and Distinguished Talent Program of Shengjing Hospital (No. ME76). No competing interests declared.