Abstract
Polycystic ovary syndrome (PCOS) is a complex endocrinopathy affecting women of reproductive age, and whose etiology is not well understood yet. In these women, the follicular growth is arrested at preantral stage leading to cyst formation, consequently resulting in anovulatory infertility in these women. As the follicular fluid provides the conducive microenvironment for the growth of oocytes, molecular profiling of the fluid may provide unique information about pathophysiology associated with follicular development in PCOS. Post-translational addition of oligosaccharide residues is one of the many modifications of secreted proteins influencing their functions. These glycoproteins play a significant role in disease pathology. Despite glycoproteins having such essential functions, very limited information is available on their profiling in human reproductive system, and glycoproteomic profile of follicular fluid of women with PCOS is yet unexplored. In the present study, we performed a comparative glycoproteomic analysis of follicular fluid between women with PCOS and controls undergoing in vitro fertilization, by enrichment of glycoproteins using three different lectins viz. concanavalin A, wheat germ agglutinin and Jacalin. Peptides generated by trypsin digestion were labeled with isobaric tags for relative and absolute quantification reagents and analyzed by liquid chromatography tandem mass spectrometry. We identified 10 differentially expressed glycoproteins, in the follicular fluid of women with PCOS compared to controls. Two important differentially expressed proteins- SERPINA1 and ITIH4, were consistently upregulated and downregulated respectively, upon validation by immunoblotting in follicular fluid and real-time polymerase chain reaction in granulosa cells. These proteins play a role in angiogenesis and extracellular matrix stabilization, vital for follicle maturation. In conclusion, a comparative glycoproteomic profiling of follicular fluid from women with PCOS and controls revealed an altered expression of proteins which may contribute to the defects in follicle development in PCOS pathophysiology.
Highlights
Polycystic ovary syndrome (PCOS) is the most common endocrine disorder affecting 6% to 15% of reproductive age women, its etiology and pathogenesis remains uncertain till [1]
Baseline serum luteinizing hormone (LH) levels, LH/follicular stimulating hormone (FSH) ratio and anti-Mullerian hormone (AMH) levels were significantly higher with lower FSH in the PCOS group when compared to controls (Table 1)
On the day of ovum pick up (d-OPU), follicular fluid levels of E2, TT, T, bioavailable testosterone and free androgen index (FAI) were significantly high and sex hormone binding globulin (SHBG), P4, levels were significantly low in women with PCOS compared to controls (Table 2)
Summary
Polycystic ovary syndrome (PCOS) is the most common endocrine disorder affecting 6% to 15% of reproductive age women, its etiology and pathogenesis remains uncertain till [1] It is characterized by altered gonadotropin secretion, irregular menses, enlarged ovaries with multiple cysts on ultrasound imaging, together with hyperandrogenism (hirsutism, acne, alopecia), insulin resistance, obesity and abnormal glucose metabolism. Follicular fluid is present in the antrum of growing follicle and consists of secretions from granulosa cells (GCs) and exudates from plasma through thecal capillaries. It contains crucial growth factors, proteins, steroids, polysaccharides etc. Alterations in the proteomic signature of follicular fluid could reveal the molecular mechanisms involved in healthy follicle development and oocyte maturation and help to decipher the underlying pathophysiology of ovarian disorders [8]
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