Abstract

BackgroundFollicular fluid is a unique biological fluid in which the critical events of oocyte and follicular maturation and somatic cell-germ cell communication occur. Because of the intimate proximity of follicular fluid to the maturing oocyte, this fluid provides a unique window into the processes occurring during follicular maturation. A thorough identification of the specific components within follicular fluid may provide a better understanding of intrafollicular signaling, as well as reveal potential biomarkers of oocyte health for women undergoing assisted reproductive treatment. In this study, we used high and low pH HPLC peptide separations followed by mass spectrometry to perform a comprehensive proteomic analysis of human follicular fluid from healthy ovum donors. Next, using samples from a second set of patients, an isobaric mass tagging strategy for quantitative analysis was used to identify proteins with altered abundances after hCG treatment.ResultsA total of 742 follicular fluid proteins were identified in healthy ovum donors, including 413 that have not been previously reported. The proteins belong to diverse functional groups including insulin growth factor and insulin growth factor binding protein families, growth factor and related proteins, receptor signaling, defense/immunity, anti-apoptotic proteins, matrix metalloprotease related proteins, and complement activity. In a quantitative analysis, follicular fluid samples from age-matched women undergoing in vitro fertilization oocyte retrieval were compared and 17 follicular fluid proteins were found at significantly altered levels (p < 0.05) between pre-hCG and post-hCG samples. These proteins belong to a variety of functional processes, including protease inhibition, inflammation, and cell adhesion.ConclusionsThis database of FF proteins significantly extends the known protein components present during the peri-ovulatory period and provides a useful basis for future studies comparing follicular fluid proteomes in various fertility, disease, and environmental exposure conditions. We identified 17 differentially expressed proteins after hCG treatment and together these data showed the feasibility for defining biomarkers that illuminate how the ovarian follicle microenvironment is altered in various infertility-related conditions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12014-015-9077-6) contains supplementary material, which is available to authorized users.

Highlights

  • The biologic niche where oocyte growth and maturation occurs within the ovary is termed the ovarian follicle

  • Proteomic analysis of biological fluids is complicated by the large dynamic range of protein concentrations, spanning ten orders of magnitude, greatly exceeding that of any methods used for proteomic analysis [28]

  • This analysis has been the most comprehensive proteomic evaluation of human follicular fluid in a single study to date, with 742 distinct proteins identified. This extends the FF proteome to 982 high confidence proteins, underscoring the utility of multiple, orthogonal protein and peptide methodologies for comprehensive examination of this complex proteome. This database of FF proteins provides a useful basis for studies comparing follicular fluid proteomes in various fertility, disease, and environmental exposure conditions

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Summary

Introduction

The biologic niche where oocyte growth and maturation occurs within the ovary is termed the ovarian follicle. It is evident that there is communication from the mural granulosa cells to the cumulus complex [4,5,6]; from the cumulus complex to the oocyte; and from the oocyte back to the somatic compartment [7,8,9,10] These signaling events can be mediated by soluble small molecules via gap junctions or lipid signals (e.g., cGMP, ffMAS, sphingosine-1-p) [11,12,13,14], but the majority of the components for paracrine intrafollicular signaling identified to date involve peptide hormones [15,16,17,18,19]. Follicular fluid is a unique biological fluid in which the critical events of oocyte and follicular maturation and somatic cell-germ cell communication occur. Using samples from a second set of patients, an isobaric mass tagging strategy for quantitative analysis was used to identify proteins with altered abundances after hCG treatment

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