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 (VEG F) and its receptors in the human corpus luteum (CL), expression of VEGF an d 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 localiz ed in luteal cells and both flt-1 and KDR were also localized in luteal cel ls, in addition to vascular endothelial cells. Messenger RNA (mRNA) express ion of VEGF, flt-1, and KDR remained constant in the CL during the luteal p hase and was lower in the regression phase. In the pregnant CL, VEGF mRNA e xpression was higher compared with that in the midluteal phase, and mRNA ex pression 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 VE GF, flt-1, and KDR was similar to that in their mRNA expression. To study t he effect of human CG (hCG) on VEGF expression in the CL, corpora lutea obt ained from the midluteal phase were incubated with hCG (1 IU/ml) for 6 h. h CG increased the expression of mRNA and protein of VEGF. In conclusion, VEG F 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 VE GF expression when pregnancy occurs.