Abstract
Abstract: :
Purpose: Vascular endothelial growth factor (VEGF) family plays an essential role in vascular development, angiogenesis and lymphangiogenesis in vivo. Among these, both VEGF-C and VEGF-D are known to stimulate angiogenesis and lymhangiogenesis via the VEGF receptor-2 (VEGFR-2/KDR) and VEGFR-3 (Flt-4). Regulational mechanism of expression, however,.has not been fully defined. We here assessed that the effect of cell-cell or cell-matrix interaction on the transcriptional regulation of VEGF-C and -D. Methods: Human retinal pigment epithelium cell line (ARPE-19) was used in this study. In several conditions, ARPE-19 was grown in a 1:1 mixture of Dulbecco's modified Eagle's medium (DMEM) and Ham's F12 medium with 3 mM L-glutamine and 10% fetal bovine serum (FBS). Total cellular RNA was extracted from cells using the Isogen-chloroform mixtured solution, and the expression of VEGF-C or VEGF-D mRNA was evaluated by semi-quantitative RT-PCR. Results: VEGF-D mRNA expression was strongly up-regulated in the presence of 2.2mM EGTA (deprivation of Ca2+ from the culture medium). When culture plate was coated with poly-HEME, an inhibitor for cell adhesion, VEGF-D expression was similarly upregurated, compared to that in cells without coating. The treatment with Ca2+ channel blockers (20uM nifedipine or 10uM diltiazem), however, did not affect the VEGF-D mRNA expression, suggesting that VEGF-D expression may be regulated by extracellular Ca2+, but not, Ca2+ influx . Meanwhile, no significant change of the VEGF-C expression was found under these culture conditions. Conclusions: These data demonstrated that VEGF-D, but not VEGF-C, mRNA was strongly induced by depletion of extracellular Ca2+ from the culture medium and did not be affected by calcium influx. These findings suggest that VEGF-D expression can be regulated by cell-matrix and/or cell-cell contact, and may imply a potential angiogenic/lymphangiogenic potential of proliferating RPE cells when the.RPE layer is broken down.
Keywords: retinal pigment epithelium • gene/expression • extracellular matrix