Possible Role of Hypoxia-Inducible Factor-1Alpha and Vascular Endothelial Growth Factor During Periovulation and Corpus Luteum Formation in Cows

The objective of the study was to characterize expression patterns of hypoxia-inducible factor-1alpha and vascular endothelial growth factor isoforms during periovulation in the cow. Ovaries containing follicles or corpora lutea were collected by transvaginal ovariectomy (n = 5 cows/group) and timely defined (after gonad otrop in-re leasi ng hormone application) as follows: (I) 0 h; (II) 4 h; (III) 10 h; (IV) 20 h; (V) 25 h (follicles); and (VI) 60 h (early corpora lutea). The mRNA expression of genes encoding hypoxia-inducible factor-1alpha and vascular endothelial growth factor isoforms was quantified by reverse transcriptase quantitative polymerase chain reaction. The high mRNA expression of hypoxia-inducible factor-1alpha in the control follicle group (before gonad otrop in-re leasi ng hormone) was followed by a continuous and significant downregulation afterward with a minimum level in follicle group close to ovulation, and a significant increase just after ovulation. The mRNA of vascular endothelial growth factor isoforms was high during luteinizing hormone peak (4 h after gonad otrop in-re leasi ng hormone), decreased significantly thereafter to the lowest levels in follicle group 25 h after gonadotrop in-re leasi ng hormone, followed by a rapid and significant increase just after ovulation (newly corpora lutea). In conclusion, our results of hypoxia-inducible factor-1alpha and vascular endothelial growth factor regulation in follicle groups around ovulation indicate them to be necessary mediators of the luteinizing hormone-dependent ovulation and significant molecular mechanisms of angiogenesis during early corpora lutea formation.