Assessment of vascular endothelial growth factor expression and apoptosis in the ovarian graft: can exogenous gonadotropin promote angiogenesis after ovarian transplantation?

OBJECTIVE: To evaluate the effects of gonadotropin on angiogenesis by assessing vascular endothelial growth factor (VEGF) expression in rat ovaries transplanted after freezing and thawing.

DESIGN: In vitro laboratory experiments.

SETTING: Academic research institute.

ANIMAL(S): Sixty immature female rats.

INTERVENTION(S): Frozen-thawed ovaries were autotransplanted into the SC tissue of 60 rats (ages between 21 and 28 days). After transplantation, either pregnant mare's serum gonadotropin (PMSG) or saline was administered. The grafted ovaries were collected 2, 7, and 30 days after transplantation for evaluation.

MAIN OUTCOME MEASURE(S): Assessment of the morphology and number of follicles, evaluation of apoptosis, and analysis of VEGF expression in the grafted ovaries.

RESULT(S): Most follicles in the grafts were apoptotic on day 2 but recovered by day 7. The proportion of antral follicles and corpora lutea in the graft correlated with the duration after transplantation. A significant increase in the expression of VEGF188 mRNA was noticed in the grafted ovaries on day 2. Moreover, the mRNA expression in the PMSG group was higher than that in the control group. The increased VEGF protein production in the graft was confirmed by Western blot analysis.

CONCLUSION(S): In ovariectomized animals, gonadotropin treatment may not provide any added benefits for folliculogenesis and angiogenesis. Nevertheless, a significant increase in the VEGF188 isoform in the gonadotropin-treated group may suggest the positive effect of exogenous gonadotropin therapy in the early stages of angiogenesis.