Abstract
Purpose: :
Inhibition of ocular neovascularization represents a therapeutic perspective for several common retinal and choroidal blinding diseases, including proliferative diabetic retinopathy and age-related macular degeneration. We previously reported that the Sonic Hedgehog (Shh) pathway is activated in animal models of retinal and choroidal neovascularization and that its pharmacological inhibition results in significant reduction of neovascularization in both models. This candidates the Shh pathway as a molecular target for treatment of ocular neovascular diseases. We are currently testing two nucleic acid-based strategies for inhibition of the Shh pathway in the retina.
Methods: :
We have generated adeno-associated viral vectors (AAV) expressing the Shh-decoy receptor HIP-Δ-22, obtained by deleting the transmembrane domain of the Hedgehog Interacting Protein (HIP); In a second approach, to inhibit Shh expression we have designed five different short interfering RNA (siRNA) complementary to human and murine Shh mRNA.
Results: :
We show that recombinant HIP-Δ-22, secreted in the medium of transfected cells, binds to Shh and inhibits Shh-induced osteogenic differentiation of the mesenchymal cell line C3H10T1/2. AAV-mediated HIP-Δ-22 expression in the retina of retinopathy of prematurity (ROP) mice results in reduced expression of Shh target genes and reduction of retinal neovascularization, suggesting that HIP-Δ-22 blocks the Shh pathway in this model.For the RNA interference approach, we have selected one siRNA resulting in >70% reduction of Shh expression in vitro and in inhibition of Shh-induced osteogenic differentiation in the C3H10T1/2 cells. In addition, upon periocular injection in ROP mice, the siRNA localizes to the inner retina and reduces Shh and its transcriptional targets retinal expression. Experiments aimed at inhibiting ocular neovascularization in ROP mice are in progress.
Conclusions: :
Our results confirm the involvement of the Shh pathway in the development of ocular neovascularization and provide novel therapeutic strategies to inhibit Shh pathway for treatment of ocular neovascular diseases.
Keywords: retinal neovascularization • gene transfer/gene therapy • retina