Abstract
Purpose:
Retinal microvascular endothelial cells (RMVECs) barrier is damaged in diabetic retinopathy (DR). Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis and vascular permeability. Many reports show VEGF-responsive genes in other types of endothelial cells, such as those in umbilical vein and lymphatic vessels. To our knowledge, comprehensive analyses of transcript levels in VEGF-stimulated RMVECs have not been reported. The purposes of the present study were to 1) determine changes in gene expression in VEGF-treated RMVECs, and 2) compare the changes with those previously reported in other types of endothelial cells.
Methods:
hRMVECs were cultured for 6 hrs in serum-free medium and then cultured with VEGF for 2, 6, 12, and 24 hrs. Extracted total cellular RNAs were reverse-transcribed, amplified, and hybridized for microarray analysis. Raw data were normalized and summarized using a robust multichip averaging algorithm. Differential expression of transcripts was analyzed with Pathway Studio software. Quantitative real-time PCR was used to validate the microarray data.
Results:
At various time points, VEGF up-regulated a total of 288 transcripts and down-regulated 208 transcripts by at least 2-fold. Six genes were up-regulated at every time-point after VEGF stimulation: angiogenesis-related genes NEDD9 and HLX; the anti-angiogenesis-related genes MGP, SPRY1 & 4; and the pseudo gene RPL23AP32. Nineteen genes increased more than 5-fold at 24 hrs. The most over-expressed gene was FABP4, a known potential target for pathologic retinal angiogenesis in DR. Several genes (e.g., sterol biosynthesis-related genes, signal transduction-related genes and membrane potential-related gene) up-regulated in the present study were not up-regulated in other types of endothelial cells.
Conclusions:
VEGF treatment of RMVECs causes up-regulation of angiogenesis-related genes, such as FABP4. For some genes (e.g., NEDD9, SPRY1, CHRNA1 and SQLE), the up-regulation occurs only in RMVECs and not in other types of endothelial cells. These genes may have specific roles in the retina during VEGF-induced proliferation of microvascular endothelial cells.