Altered Gene Expression Profile of Microvascular Endothelium in Placentas from IUGR/Preeclamptic Pregnancies

The placental microvasculature of the human fetus is essential for the efficient transfer of gases, nutrients and waste between the mother and fetus. Microvascular hypoplasia of the terminal villi is associated with the placental pathology observed in cases of severe Intra Uterine Growth Restriction (IUGR). We used novel methods to isolate a pure population of placental microvascular endothelial cells from control preterm placentas (n=3) and placenta complicated by severe IUGR (n=6) with superimposed preeclampsia (n=5). Distal placental villous tissue was collected to enrich for terminal villi. Tissue was minced, digested and placental microvascular endothelial cells (PlMEC) were positively selected using tocosylated magnetic Dynabeads labeled with Human Endothelial Antigen lectin. The purity of the PlMEC (95%) was assessed by CD31 immunocytochemistry. RNA was extracted from the PlMEC samples and also from 3 term placenta and subjected to Affymetrix microarray analysis (U133Plus2 array chips). Data from the 3 term placentas and 3 preterm PlMEC arrays was used to generate an endothelial cell specific gene profile. This profile was used to identify the endothelial genes differentially regulated in all 6 IUGR cases. BTNL9 and NTRK2 transcripts were upregulated and SAA1, GNAS and SLAMF1 transcripts were downregulated as relative to the preterm controls. These changes were validated by Real time PCR in the PlMEC samples. This novel study is the first to identify endothelial candidate genes that may play a role in the villous hypoplasia of severe IUGR. This work advances our understanding of the molecular defects in placental microvascular endothelial cells in normal and pathologic pregnancies. Three normal control placentas were compared against endothelial cells isolated from IUGR, IUGR and preeclampsia and normal pregancies. In this way enrichment of endothelial genes could be determined as well as changes in the expression pattern of endothelial genes due to different pathologies.