Vascular endothelial growth factor expression in the rat uterus and placenta throughout pregnancy

To elucidate the physiological roles during pregnancy of vascular endotheli al growth factor (VEGF), we examined the temporal and spatial expression of VEGF protein and mRNA in the rat uterine and placental tissues throughout pregnancy. The uterine tissue of nonpregnant rats, pregnant rats, and the r at placental tissue were examined by Northern blotting, in situ hybridizati on and immunohistochemistry. Northern analysis revealed the existence of VE GF mRNA in the uterus and placenta regardless of the stage of estrous cycle or pregnancy. The results of in situ hybridization and histochemistry for nonpregnant rat specimens showed that VEGF mRNA and protein accumulated in myometrial smooth muscle cells, glandular epithelial cells, stromal cells, and endometrial epithelial cells during each stage of the estrous cycle. Th e level of accumulation increased in all but the myometrial smooth muscle c ells on estrus, and further increased during pregnancy. Furthermore fetal c ompartments such as trophoblasts, trophoblast giant cells, vitelline epithe lial cells, and amnion were labeled more strongly than the maternal compart ment. In conclusion, the spatial expression of VEGF was relatively constant in ra t maternal uterus during the estrous cycle and during pregnancy; however, t here was a temporal change of VEGF expression.