Sequence-independent Suppression of Choroidal Neovascularization by siRNA Is Mediated via Thrombospondins

Abstract

Purpose: : We have shown that 21-nt siRNAs can suppress laser-induced choroidal neovascularization (CNV) in mice via toll-like receptor 3 (TLR3) and without invoking RNA interference (Kleinman et al. Nature 2008). We sought to further elucidate the signaling mediators that drive this generic anti-angiogenic activity of siRNAs.

Methods: : Real-time PCR arrays were used to profile the expression of 84 genes involved in angiogenesis following laser injury in C57BL/6J mice with or without 21-nt-siRNA treatment. CNV responses to 21-nt siRNAs targeting VEGF-A, VEGFR-1 (both of which are in clinical trials), or firefly luciferase (Luc) were tested in wild-type mice and in mice deficient in thrombospondin-1 (TSP1) and/or thrombospondin-2 (TSP2).

Results: : Real-time PCR showed marked upregulation of TSP1 and TSP2 mRNAs in the RPE/choroid following siRNA administration. The suppression of CNV in wild-type mice by siRNA-Vegfa, siRNA-Vegfr1, and siRNA-Luc was equivalent, and either reduced or abolished in TSP1^-/-, TSP2^-/-, and TSP1^-/- x TSP2^-/- mice.

Conclusions: : These data demonstrate that TSP1 and TSP2 play a non-redundant function in the signaling cascades mediating sequence- and target-independent suppression of CNV by siRNA.

Keywords: age-related macular degeneration • RNAi • choroid: neovascularization