Expression of vascular endothelial growth factor and its receptors in the human corpus luteum during the menstrual cycle and in early pregnancy

To investigate the possible role of vascular endothelial growth factor (VEGF) and its receptors in the human corpus luteum (CL), expression of VEGF and its receptors, the fms-like tyrosine kinase and the kinase insert domain-containing region (KDR), was analyzed in the CL during the menstrual cycle and in early pregnancy. Immunohistochemistry revealed that VEGF was localized in luteal cells and both flt-1 and KDR were also localized in luteal cells, in addition to vascular endothelial cells. Messenger RNA (mRNA) expression of VEGF, flt-1, and KDR remained constant in the CL during the luteal phase and was lower in the regression phase. In the pregnant CL, VEGF mRNA expression was higher compared with that in the midluteal phase, and mRNA expression of both flt-1 and KDR was the same as that in the midluteal phase. Western blot analyses revealed that the change in protein expression of VEGF, flt-1, and KDR was similar to that in their mRNA expression. To study the effect of human CG (hCG) on VEGF expression in the CL, corpora lutea obtained from the midluteal phase were incubated with hCG (1 IU/ml) for 6 h. hCG increased the expression of mRNA and protein of VEGF. In conclusion, VEGF and its receptors may play important roles in development and function of the CL, and VEGF may exert a paracrine-autocrine role in regulating luteal function. hCG may act to prolong the life span of the CL by stimulating VEGF expression when pregnancy occurs.