328 Chorionic villi angiogenic protein expression in normal human pregnancy

Abstract

Our goal was to examine the changes in chorionic villi (CV) expression of angiogenic proteins VEGF165, VEGF165b and MMP-9 throughout gestation in normal human pregnancy. Placentas were obtained from normal pregnant women who underwent elective abortion in the first and second trimesters of pregnancy, and from women who delivered at term. CV protein expressions were analyzed by ELISA using monoclonal antibodies to human VEGF165, VEGF165b and MMP-9 proteins (R&D Systems, Minneapolis, MN). Non-parametric test considered p<0.05 as significant. Our study highlights gestational age-specific alterations in all three CV proteins. VEGF165b protein peaked in the 2nd trimester while VEGF165 protein peaked in the third. MMP-9 protein progressively increased with increase in gestational age. Spearman's correlation showed that VEGF165, VEGF165b and MMP-9 proteins were significantly correlated with gestational age in days (r2=+0.236, p=0.001; r2= +0.158, p=0.028; r2=+0.475, p=0.0001, respectively). In the 3rd trimester, a significant positive correlation was seen between VEGF165 and VEGF165b (r2=+0.368, p=0.001); and a significant negative correlation was seen between VEGF165 and MMP-9 proteins (r2= -0.306, p=0.003). Of the three proteins selected, VEGF165 is the dominant angiogenic protein and its overexpression can result in tumorigenesis. VEGF165b is down-regulated in tumors. MMP-9 degrades ECM and promotes endothelial cell migration and is considered angiogenic. The 3rd trimester of human pregnancy is a unique phase when maximum angiogenesis needs to occur, yet as pregnancy approaches parturition the angiogenic process needs to be terminated. The correlation seen between the two isoforms of VEGF in the 3rd trimester suggest that when fetal demand is at its peak the two VEGF isoforms work synergistically to maximize angiogenesis. And, the ample presence of VEGF165b in the 3rd trimester and the inverse correlation seen between MMP-9 and VEGF165 could be mechanisms at place to restrict overexpression of VEGF165 and placental angiogenesis as pregnancy approaches parturition.