Administration of a Gonadotropin-Releasing Hormone agonist affects corpus luteum development, angiogenesis and induces apoptosis in a rat model of Ovarian Hyperstimulation Syndrome.

SCOTTI LEOPOLDINA; IRUSTA GRISELDA; ABRAMOVICH DALHIA; TESONE MARTA; FERNANDA PARBORELL

Congreso; 43rd SSR Annual Meeting; 2010

Moderate to severe ovarian hyperstimulation syndrome (OHSS) has been calculated to occur in 0.2% to 2% of all ovarian stimulation cycles.  Risk factors include low body weight, high follicle count, polycystic ovarian syndrome, previous OHSS and elevated serum estradiol. Gonadotropin-releasing hormone analogs are thought to be effective in preventing this complication and several clinical trials have found lower incidence of OHSS in patients treated with these molecules. Our objective was to analyze the in vivo effect of GnRH-I agonist on corpus luteum (CL) development, angiogenesis, luteal regression and cell proliferation in ovaries from rat OHSS model. Group OHSS (hyperstimulated immature Sprague Dawley rats) received excessive doses of pregnant mare serum gonadotropin (PMSG, 50 UI/day) injected for 4 consecutive days (from the 21th day to 24th of life), followed by human chorionic gonadotropin (hCG, 25 UI, 25th day of life). Group OHSS + GnRH-I a (GnRH-agonist treated hyperestimulated immature rats) received the same doses of gonadotropins than in group OHSS and, in turn, received injections of GnRH-I a for 5 consecutive days (Leuprolide Acetate, 100 μg/kg/día, from the 21th to the 25th day of life; twice a day), followed by hCG (25 UI, 25th day of life). Immature female Sprague Dawley rats were hyperstimulated and treated with GnRH-I agonist from the start of pregnant mare serum gonadotropin (PMSG) until the day of hCG (human chorionic gonadotropin) for 5 consecutive days. Blood and tissue samples were collected at 48 hours after hCG injection. VEGFA levels were evaluated in the peritoneal fluid by ELISA. Serum progesterone and estradiol were measured by RIA. Histological features of sectioned ovaries were assessed in hematoxilin and eosin stained slides. Cell proliferation and apoptosis were assessed by immunohistochemistry for PCNA and TUNEL, respectively. FLK-1 (VEGFA receptor) and PCNA protein levels were evaluated by western blot. In the OHSS model, treatment with GnRH-I agonist resulted in a significant decrease in ovarian weight as well as a decrease in progesterone and estradiol serum levels. Moreover, this agonist significantly decreased the concentration of peritoneal VEGF. GnRH-I agonist significantly decreased the number of development CLs and mature CLs in the OHSS group compared to the OHSS group without treatment. The treatment with GnRH-I agonist significantly decreased the levels of FLK-1 in the OHSS rats. GnRH-I agonist treatment reduced the diameter of CLs, as well as decreased CL cell proliferation in OHSS model. Finally, GnRH-I agonist increased apoptosis in CLs from OHSS group. In conclusion, in the OHSS model, the administration of GnRH-I agonist interferes with luteal steroidogenesis, angiogenesis and CL development associated with a decrease in luteal proliferation and an increase in apoptosis process. Therefore, the treatment with a GnRH-I agonist decreased the severity of OHSS in an immature rat model stimulated by PMSG/hCG.