Assessment of rat endometrial pinopodes in normal cycles and following HCG ovarian hyperstimulation with or without progesterone supplementation: scanning electron microscopic study

ABSTRACT

Pinopodes, mushroom-like projections, arise from the endometrial surface at or just before the time of implantation. They have been proposed as a method of identifying endometrial receptivity for transferred embryo in programs of IVF. The present work was planned to assess the expression of pinopodes in rat endometrium in normal cycles and following ovarian hyperstimulation with or without progesterone supplementation as a trial to estimate the optimal date for successful embryo transfer in IVF programs. Forty-five adult female albino rats were divided equally into three groups. In the control group, ovulation was induced by mechanical vagino-cervical stimulation. Group II was subjected to ovarian hyperstimulation using human chorionic gonadotrophin [HCG] 350 IU/kg injected intraperitoneally [two injections 48h apart and vagino-cervical stimulation was performed on the evening of administration of the second injection. Group III was treated in the same way as group II, followed by a daily subcutaneous injection of progesterone 35mg/kg. All rats were sacrificed 3, and 5 days after vagino-cervical stimulation. The middle third of the right uterine horn were processes for scanning electron microscope examination. The mean number of pinopodes was statistically analyzed. In control rats, pinopodes started to appear on day 4 and significantly increased in number on day 5. In the HCG-ovarian hyperstimulated group, there was an early appearance of pinopodes on day 3, which increased in number on day 4 and regressed on day 5. With progesterone supplementation, there was an obvious increase in the number of pinopodes especially on day 4. It could be concluded that ovarian hyperstimulation using HCG may cause early expression of pinopodes and premature formation of an implantation window. Also, progesterone supplementation could enhance endometrial receptivity. This should be taken into consideration in IVF programs to synchronize embryo and endometrial development, which could improve pregnancy rates