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 conti-nuous 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.

Automated summary

The objective of this study was to examine the expression patterns of hypoxia-inducible factor-1alpha and vascular endothelial growth factor isoforms during periovulation in cows. The results showed that both genes exhibited significant changes in expression levels before and after ovulation, suggesting their important roles in follicle regulation and angiogenesis during early corpora lutea formation.