Transcriptome of Angiopoietin 1–Activated Human Umbilical Vein Endothelial Cells

Angiopoietin 1 (Ang-1) is the main ligand for endothelial cell-specific tyrosine kinase (Tie-2) receptors and it promotes migration and proliferation and inhibits apoptosis and vascular leakage. The exact mechanisms through which the Ang-1 exerts these effects remain unclear. The authors exposed human umbilical vein endothelial cells (HUVECs) to Ang-1 (300 ng/mL) for 4 h and conducted gene expression profiling using oligonucleotide microarrays. Real-time polymerase chain reaction (PCR) was also conducted to verify several of the genes that were regulated by Ang-1. Exposure to Ang-1 resulted in induction of 86 genes that are involved in endothelial cell (EC) proliferation, differentiation, migration, and survival. Thirty-six of these genes, including stanniocalcin, cyclin D1, vascular endothelial growth factor C, fms-related tyrosine kinase 1, interleukin 8, and CXCR4 have previously been shown to be induced by vascular endothelial growth factor (VEGF), suggesting significant similarities between VEGF and Ang-1 pathways. Ang-1 exposure also inhibited mRNA expressions of 49 genes, most of which are involved in cell cycle arrest, apoptosis, and suppression of transcription. These results indicate that Ang-1 triggers coordinated responses in endothelial cells designed to inhibit the expression of proapoptotic and antiproliferative genes and up-regulate proproliferative, proangiogenic, and antiapoptotic pathways. Moreover, we also found that the Erk1/2, phosphatidylinositol (PI) 3-kinase, and the mTOR pathways are involved in Ang-1-induced gene expression in HUVECs.