Expression pattern of HIF1alpha and vasohibins during follicle maturation and corpus luteum function in the bovine ovary

Abstract

The aim of this study was to characterize expression patterns of hypoxia-inducible factor-1alpha (HIF1A) and vasohibin family members (VASH1 and VASH2) during different stages of ovarian function in cow. Experiment 1: Antral follicle classification occurred by follicle size and estradiol-17beta (E2) concentration in the follicular fluid into 5 groups (<0.5, 0.5-5, 5-40, 40-180 and >180 E2 ng/ml). Experiment 2: Corpora lutea (CL) were assigned to the following stages: days 1-2, 3-4, 5-7, 8-12, 13-16 and >18 (after regression) of oestrous cycle and of pregnancy (months 1-2, 3-4, 6-7, >8). Experiment 3: Cows on days 8-12 were injected with a prostaglandin F2alpha (PGF) analogue and CL were collected before and 0.5, 2, 4, 12, 24, 48 and 64 hr after PGF injection. Expression of mRNA was measured by qPCR, steroid hormone concentration by EIA and localization by immunohistochemistry. HIF1A mRNA expression in our study increases significantly in follicles during final maturation. The highest HIF1A mRNA expression was detected during the early luteal phase, followed by a significant decrease afterwards. In contrast, the mRNA of vasohibins in small follicle was high, followed by a continuous and significant downregulation in preovulatory follicles. The obtained results show a remarkable inverse expression and localization pattern of HIF1A and vasohibins during different stages of ovarian function in cow. These results lead to the assumption that the examined factors are involved in the local mechanisms regulating angiogenesis and that the interactions between proangiogenic (HIF1A) and antiangiogenic (vasohibins) factors impact all stages of bovine ovary function.

Keywords: angiogenesis; antral follicle; cattle; corpus luteum; endocrinology; ovary; pregnancy.