The oocyte microenvironment is altered in adolescents compared to oocyte donors.

STUDY QUESTION: Are the molecular signatures of cumulus cells (CCs) and follicular fluid (FF) of adolescents undergoing fertility preservation differ from that of reproductively adult oocyte donors?

SUMMARY ANSWER: The microenvironment immediately surrounding the oocyte, including the CCs and FF, is altered in adolescents undergoing fertility preservation compared to oocyte donors.

WHAT IS KNOWN ALREADY: Adolescents experience a period of subfecundity following menarche. Recent evidence suggests that this may be at least partially due to increased oocyte aneuploidy. Reproductive juvenescence in mammals is associated with suboptimal oocyte quality.

STUDY DESIGN SIZE DURATION: This was a prospective cohort study. Adolescents (10-19 years old, N=23) and oocyte donors (22-30 years old, N=31) undergoing ovarian stimulation and oocyte retrieval at the Northwestern Fertility and Reproductive Medicine Center between November 1, 2020 and May 1, 2023 were enrolled in this study.

PARTICIPANTS/MATERIALS SETTING METHODS: Patient demographics, ovarian stimulation, and oocyte retrieval outcomes were collected for all participants. The transcriptome of CCs associated with mature oocytes was compared between adolescents (10-19 years old, n=19), and oocyte donors (22-30 years old, n=19) using bulk RNA-sequencing. FF cytokine profiles (10-19 years old, n=18 vs. 25-30 years old, n=16) were compared using cytokine arrays.

MAIN RESULTS AND THE ROLE OF CHANCE: RNA-seq analysis revealed 581 differentially expressed genes (DEGs) in cumulus cells of adolescents relative to oocyte donors, with 361 genes downregulated and 220 upregulated. Genes enriched in pathways involved in cell cycle and cell division (e.g., GO:1903047, p= 3.5 x 10 -43 ; GO:0051983, p= 4.1 x 10 - 30 ; GO:0000281, p= 7.7 x 10 -15 ; GO:0044839, p= 5.3 x 10 -13 ) were significantly downregulated, while genes enriched in several pathways involved in cellular and vesicle organization (e.g., GO:0010256, p= 1.2 x 10 -8 ; GO:0051129, p= 6.8 x 10 -7 ; GO:0016050, p= 7.4 x 10 -7 ; GO:0051640, p= 8.1 x 10 -7 ) were upregulated in CCs of adolescents compared to oocyte donors. The levels of 9 cytokines were significantly increased in FF of adolescents compared to oocyte donors: IL-1 alpha (2-fold), IL-1 beta (1.7-fold), I-309 (2-fold), IL-15 (1.6-fold), TARC (1.9-fold), TPO (2.1-fold), IGFBP-4 (2-fold), IL-12-p40 (1.7-fold) and ENA-78 (1.4-fold). Interestingly, 7 of these cytokines have known pro-inflammatory roles. Importantly, neither the CC transcriptomes or FF cytokine profiles were different in adolescents with or without cancer.

LARGE SCALE DATA: Original high-throughput sequencing data will be deposited in Gene Expression Omnibus (GEO) before publication, and the GEO accession number will be provided here.

LIMITATIONS REASONS FOR CAUTION: This study aims to gain insights into the associated gamete quality by studying the immediate oocyte microenvironment. The direct study of oocytes is more challenging due to sample scarcity, as they are cryopreserved for future use, but will provide a more accurate assessment of oocyte reproductive potential.

WIDER IMPLICATIONS OF THE FINDINGS: Understanding the underpinnings of altered immediate oocyte microenvironment of adolescent patients may provide insights into the reproductive potential of the associated gametes in the younger end of the age spectrum. This has implications for the fertility preservation cycles for very young patients.

STUDY FUNDING/COMPETING INTERESTS: This project was supported by Friends of Prentice organization SP0061324 (M.M.L and E.B.), Gesualdo Family Foundation (Research Scholar: M.M.L.), and NIH/NICHD K12 HD050121 (E.B.). The authors have declared that no conflict of interest exists.