The cKit Inhibitor, Masitinib, Prevents Diabetes-Induced Retinal Vascular Leakage.

Purpose: Stem cell factor (SCF) has recently demonstrated activity as a novel endothelial permeability factor that contributes to the development of diabetes-induced hyperpermeable retinal vasculature. This study investigated the therapeutic potential of masitinib, a pharmacologic inhibitor of the SCF receptor cKit, for prevention of diabetes-induced breakdown of blood retinal barrier (BRB).

Methods: Permeability assays were performed with human retinal microvascular endothelial cells (HRMECs) and murine retinal vasculature. Localization of vascular endothelial (VE)-cadherin and activation of SCF signaling pathway was determined by immunofluorescence and Western blotting assays. Mice and rats with streptozotocin (STZ)-induced diabetes were used to investigate the role of cKit and masitinib in diabetes-induced retinal vascular hyperpermeability.

Results: Masitinib substantially blocked SCF-induced phosphorylation of cKit in HRMECs. In vitro and in vivo vascular permeability assays showed that masitinib significantly inhibited SCF-induced endothelial hyperpermeability and junctional loss of VE-cadherin. Streptozotocin-induced diabetes was induced in cKit-mutant mice with low cKit expression in their endothelial cells. Although diabetic wild-type mice exhibited enhanced retinal vascular leakage, diabetic cKit-mutant mice showed no increase in retinal vascular leakage or alteration in the distribution of VE-cadherin; this indicates the crucial role of cKit in diabetes-induced breakdown of BRB. Moreover, in vivo prevention experiments showed that an intravitreal injection of masitinib substantially inhibited the development of hyperpermeable retinal vasculature.

Conclusions: These results provide the first demonstration that cKit inhibitors, such as masitinib, might be promising therapeutics for prevention of diabetes-induced breakdown of the BRB.