A methodological and functional proteomic approach of human follicular fluid en route for oocyte quality evaluation

Abstract

Human follicular fluid (HFF) has been proven to contain biologically active molecules and proteins that may affect follicle growth and oocyte fertilization. Based on this concept, HFF proteomic characterization is having a significant impact in the delineation of a biomarkers' profile for oocyte quality estimation and, maybe, for in vitro fertilization (IVF) success improvement. Follicular fluid is characterized by a vast protein complexity and a broad dynamic range of protein abundances that hinder its analysis. In this study we determined a proper solubilization and resolution method of HFF in 2-DE, minimizing sample manipulation, protein loss, and experimental artifacts. According to our methodology some low-abundance proteins were detected and identified by MS. Identified proteins were then functionally cross-linked by a pathway analysis. The generated path highlighted the occurrence in HFF of a tight functional-network in which effectors and inhibitors control and balance a space- and time-dependent induction/inhibition of inflammation, coagulation, and ECM degradation/remodeling. Such fine modulation of enzymatic activities exerts a fundamental role in follicle development and in oocyte competence acquiring. Alpha-1-antitrypsin resulted in the core protein of the delineated net and we interestingly detected its differential incidence in FF and serum from two small cohorts of patients who underwent IVF.

Biological significance: Human ovarian follicular fluid (HFF) is the in vivo microenvironment for oocyte during folliculogenesis. It contains biologically active molecules that may affect oocyte quality, fertilization, and embryo development. HFF is also one of the most abundant "waste product" in assisted reproduction. This makes HFF a readily accessible source of biomolecules for competence evaluation of collected oocytes. The methodological improvement we obtained in proteomics characterization of HFF lead to a wide overview on the functional correlation existing between several fluid components and on how their aberrant occurrence/activity may affect oocyte quality and ovulation.

Keywords: Functional proteomics; Human follicular fluid; In vitro fertilization; Inflammatory reaction; Oocyte quality; Ovulation.