Expression of angiogenic proteins in the retinal pigment epithelium of SPARC and HEVIN knockout mice.

Abstract

Introduction: Unregulated angiogenesis is associated with several ocular diseases. Vascular Endothelial Growth Factor (VEGF) family members are potent angiogenic stimulators and their elevated expressions are tightly associated with these diseases. VEGF activity is regulated, in part, by the matricellular protein, Secreted Protein, Acidic and Rich in Cysteine (SPARC). However, the influence of SPARC or SPARC-like protein (HEVIN) on the expression of VEGF, its receptors and Pigment Epithelium Derived Factor (PEDF), an angiostatic factor, in retinal pigment epithelial (RPE) cells remains unknown. Therefore, we aimed to examine if SPARC-knockout (KO) and HEVIN-KO mouse RPE cells differ from wild-type (WT) RPE cells in the expression of these proteins.Methods/Results: Growth rate analysis revealed that SPARC-KO and HEVIN-KO cells proliferated faster than WT cells. Quantitative Real time-PCR showed that VEGF-B and VEGFR-1 were up-regulated in SPARC-KO and HEVIN-KO cells, while VEGF-A, -C and VEGFR-2 were down-regulated in SPARC-KO cells. Immunofluorescence staining result for VEGFR-1 and PEDF protein appeared similar in SPARC-KO and HEVIN-KO cells, and it confirmed the down-regulation of VEGFR-2 protein in HEVIN-KO and SPARC-KO cells. Conclusion: Loss of SPARC and HEVIN in RPE cells has differential effects on the individual VEGFs’ and VEGFRs’ expression, suggesting that they may regulate angiogenesis in a non-redundant manner.