Expression of vascular endothelial growth factor (VEGF) receptor in goat ovaries and improvement of in vitro caprine preantral follicle survival and growth with VEGF
The aim of the present study was to evaluate the effect of vascular endothelial growth factor (VEGF) on the survival and growth of goat preantral follicles after in vitro culture and to verify the expression of VEGF receptor (VEGFR)-2 in goat ovaries. Ovarian fragments were cultured for 1 or 7 days in minimal essential medium (MEM) with different concentrations of VEGF (1, 10, 50, 100 or 200 ng mL(-1)). Non-cultured (fresh control) and cultured tissues were processed for histological and ultrastructural studies. The results showed that 200 ng mL(-1) VEGF resulted in a similar percentage of normal preantral follicles after 1 and 7 days of culture compared with control. Compared with basic culture medium alone, an increase in follicular and oocyte diameters was observed in the presence of 10 ng mL(-1) VEGF after 7 days culture. Ultrastructural analysis confirmed follicular integrity after 7 days culture in the presence of 200 ng mL(-1) VEGF. Immunohistochemical studies demonstrated the expression of VEGFR-2 in oocytes and granulosa cells of all follicular stages, except in granulosa cells of primordial follicles. In conclusion, the present study has shown that VEGF maintains follicular ultrastructural integrity and promotes follicular growth. In addition, VEGFR-2 is expressed in oocytes of caprine ovarian follicles at all developmental stages and in granulosa cells of developing follicles.
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