Progressive Changes in Human Follicular Fluid Composition over the Course of Ovulation: Quantitative Proteomic Analyses.

The composition of follicular fluid reflects crucial paracrine signalling between granulosa- and theca cells and the oocyte. Dynamic changes in the protein composition of human follicular fluid across multiple time points in the period where final meiotic maturation and release of the oocyte take place are previously undescribed. Twenty-five women undergoing IVF- or ICSI treatment in a standard antagonist protocol with agonist ovulation trigger were included in this prospective cohort study. From each patient one follicle was aspirated by transvaginal ultrasound guided puncture at one of five specific time points either before ovulation induction (T=0) or 12-, 17-, 32- or 36 hours after ovulation induction (five patients/time point). Proteomics was carried out by liquid chromatography-mass spectrometry. In total, 400 proteins were identified (FDR<0.05) and 30 were significantly regulated across time points (one-way ANOVA, adjusted p<0.05). Compared to compiled human plasma proteome sets, 47 proteins were unique to follicular fluid. Enriched biological functions among differentially expressed proteins included immune functions, wound healing and functions related to blood coagulation (FDR<0.02). The most profound changes occurred shortly after ovulation induction. We confirmed parallel protein expression to known granulosa cell mRNA changes and described many hitherto unknown protein expression profiles during ovulation. Thus, the study endorsed important biological functions of some proteins and suggested additional proteins, which may be crucial to intrafollicular signalling and oocyte competence that should be further investigated.