Apolipoprotein A1 as a novel anti-implantation biomarker in polycystic ovary syndrome: A case-control study

BACKGROUND Women with polycystic ovary syndrome have lower pregnancy rates, possibly due to the decreased uterine receptivity. Successful implantation depends on protein networks that are essential for cross-talk between the embryo and endometrium. Apolipoprotein A1 has been proposed as a putative anti-implantation factor. In this study, we evaluated apolipoprotein A1 expression in human endometrial tissues. MATERIALS AND METHODS Endometrial apolipoprotein A1 messenger RNA (mRNA) and protein expression were investigated using quantitative real-time polymerase chain reaction (PCR) and Western blot. The distribution of apolipoprotein A1 was also detected by immunostaining. Samples were obtained from 10 patients with polycystic ovary syndrome and 15 healthy fertile women in the proliferative (on day 2 or day 3 before ovulation, n = 7) and secretory (on days 3-5 after ovulation, n = 8) phases. RESULTS Endometrial apolipoprotein A1 expression was upregulated in patients with polycystic ovary syndrome compared to normal subjects. However, apolipoprotein A1 expression in the proliferative phase was significantly higher than in the luteal phase (P value < 0.05). CONCLUSION It seems that differentially expressed apolipoprotein A1 negatively affects endometrial receptivity in patients with polycystic ovary syndrome. The results showed that apolipoprotein A1 level significantly changes in the human endometrium during the menstrual cycle with minimum expression in the secretory phase, coincident with the receptive phase (window of implantation). Further studies are required to clarify the clinical application of this protein.