Vascularity and expression of angiogenic factors in bovine dominant follicles of the first follicular wave

¹ Department of Animal and Range Sciences, North Dakota State University, Fargo, ND 58105; Center for Nutrition and Pregnancy, North Dakota State University, Fargo, ND 58105; Cell Biology Center, North Dakota State University, Fargo, ND 58105
² Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand 40002
³ Department of Animal and Range Sciences, North Dakota State University, Fargo, ND 58105; Center for Nutrition and Pregnancy, North Dakota State University, Fargo, ND 58105
⁴ Department of Animal Science, University of Wyoming, Laramie, WY 82071

^* To whom correspondence should be addressed. E-mail: Dale.Redmer{at}ndsu.edu.

	Abstract

To determine the relationship among vascularity, expression of angiogenic factors, and selected intrafollicular factors in dominant and non-dominant follicles of the first follicular wave, ovaries were obtained on d 3 of the estrous cycle from mature crossbred beef heifers (n = 8) with synchronized estrus. Follicular fluid (FF) was collected from marked follicles for determination of estradiol-17 (E), progesterone (P4), vascular endothelial growth factor (VEGF) and IGFBP concentrations. Ovaries were then perfusion-fixed and used for histochemical detection of lectin BS-1 (marker of endothelial cells and thus vascularization) binding, and immunolocalization of VEGF, endothelial nitric oxide synthase (eNOS) and proliferating cell nuclear antigen (PCNA), followed by image analysis in selected follicles. Based on E and P4 concentrations in FF, follicles were classified as dominant, estrogen-active (EA; E:P4 1) or non-dominant, estrogen-inactive (EI; E:P4 < 1). The concentration of E and VEGF in FF, area of positive staining for lectin BS-1, VEGF and eNOS, and labeling index in granulosa and theca layers were greater (P < 0.05) in the EA than EI follicles, but concentration of P4 and IGFBP in FF was less (P < 0.05) in EA than EI follicles. In addition, vascularity was positively correlated (P < 0.05) with VEGF and eNOS protein expression, tended (P < 0.1) to be positively correlated with E:P4 ratio in FF, but tended (P < 0.1) to be negatively correlated with IGFBP and P4 concentration in FF. These data highlight the importance of vascularity, angiogenic factors and IGFBP in the health of the dominant follicle in heifers, and indicate that concentrations of E, VEGF, IGFBP and P4, and E:P4 ratio in FF can be used as markers of dominant follicles.

Key Words: Cow, cell proliferation, dominant follicle, nitric oxide, vascularity, vascular endothelial growth factor

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