Dysregulation of collagen expression in peri-implantation endometrium of women with high ovarian response

AimTo analyze the effects of high ovarian response on endometrial collagen synthesis and related gene expression during the peri-implantation period in patients undergoing in vitro fertilization-embryo transfer. MethodsPeripheral blood and endometrial biopsies were obtained from infertile women on day 6 after oocytes retrieval or ovulation in 16 stimulated cycles (SC) and 16 natural cycles (NC) respectively. Serum estrogen (E-2), progesterone (P-4), histological staging, endometrial collagen, matrix metalloproteinases (MMP2, 9) and tissue inhibitors of metalloproteinases (TIMP1, 3) were assayed. ResultsSerum levels of both E-2 and P-4 were significantly higher in the SC group than those in the NC group. All endometrial samples were in the secretory phase. The collagen in the stroma of the SC group was more dense and higher than that in the NC group. MMP2 and MMP9 were detected significantly lower in the SC group than those in the NC group, while TIMP1 and TIMP3 were significantly higher. MMP2, 9 expressions are increased by estrogen and reduced by progesterone in dose-dependent manner through estrogen receptor and progesterone receptor. Correspondingly, TIMP1, 3 expressions decreased by estrogen dose-dependently while progesterone played the opposite role. ConclusionHigh levels of P-4 could stimulate excessive synthesis of collagen in peri-implantation endometrium of women with high ovarian response, and the mechanisms may be related to the decrease of MMP2, 9 and the increase of TIMP1, 3 through P-4 receptor.