Abstract
Many components in ovarian follicles (follicular fluid, cumulus cells, granular cells, etc.) dynamically change during folliculogenesis and play a positive or negative role in oocyte maturation. Infertile women who underwent intracytoplasmic sperm injection (ICSI) treatment in the reproductive medicine centre of Hangzhou Women’s Hospital between October 2018 and October 2021 were included. The ovarian follicular fluid and cumulus cells of diminished ovarian response (DOR) patients and control subjects with medical records of clinical data were collected. In total, 31 differentially expressed proteins, including 10 upregulated proteins (>1.50-fold, P<0.05) and 21 downregulated proteins (<0.67-fold, P<0.05), were identified in mature vs. immature oocytes by iTRAQ labelling coupled with 2D LC-MS/MS. GO analysis revealed that ‘cell population proliferation’ was the most diverse enrichment trend between up/downregulated proteins, while phagosome process and the PI3K-Akt signaling pathway were the two most significant pathways revealed by KEGG enrichment classification. Human prostatic acid phosphatase (PAP, ACPP) and CD5 antigen-like (CD5L) were two proteins verified by ELISA to be differentially expressed between MII and Gv oocytes (P<0.0001 and P<0.0001, respectively). Further measurement found significantly lower level of ACPP in follicular fluids and cumulus cells of DOR patients (P=0.028 and P=0.004, respectively), as an indicator of oocyte quality. Otherwise, CD5L level is upregulated in follicular fluid of DOR patients (P<0.0001). Our study provided experimental data to establish the objective indicator of oocyte maturation in the microenvironment of ovarian follicles, and also provided new insight into the measurement of oocyte quality.
Highlights
Infertility is the third most common disease after tumours and cardiovascular disease
WAP four-disulfide core domain protein 2 was validated by Liu et al as a potentially follicular fluid biomarker for the diagnosis of oocyte maturation arrest caused by overweight status [9]
This study investigated the relationship between differentially expressed proteins in human ovarian follicular fluid that represent oocyte maturity by iTRAQ labelling coupled with 2D LC-MS/MS
Summary
Infertility is the third most common disease after tumours and cardiovascular disease. According to a population-based cross-sectional study, one in four couples of childbearing age in China suffers from infertility [1]. With the increase in reproductive age due to delayed childbearing, the number of patients with diminished ovarian response (DOR) is increasing in China, resulting in non-ideal. Many components in ovarian follicular fluid (e.g., proteins, cell growth factors, peptide hormones, steroids, energy metabolites) dynamically change with the growth and development of oocytes and play a positive or negative role in oocyte maturation [4]. It has been reported that the levels of estrogen [5], melatonin [6], and soluble receptor for advanced glycation end-products [7] in ovarian follicular fluid can reflect the maturity level of oocytes. Previous proteomic research highlighted midkine as a crucial protein involved in folliculogenesis by studying follicular fluid from human small antral follicles [8].
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