Chronic Dicer1 deficiency promotes atrophic and neovascular outer retinal pathologies in mice

Degeneration of the retinal pigmented epithelium (RPE) and aberrant blood vessel growth in the eye are advanced-stage processes in blinding diseases such as age-related macular degeneration (AMD), which affect hundreds of millions of people worldwide. Loss of the RNase DICER1, an essential factor in micro-RNA biogenesis, is implicated in RPE atrophy. However, the functional implications of DICER1 loss in choroidal and retinal neovascularization are unknown. Here, we report that two independent hypomorphic mouse strains, as well as a separate model of postnatal RPE-specific DICER1 ablation, all presented with spontaneous RPE degeneration and choroidal and retinal neovascularization. DICER1 hypomorphic mice lacking critical inflammasome components or the innate immune adaptor MyD88 developed less severe RPE atrophy and pathological neovascularization. DICER1 abundance was also reduced in retinas of the JR5558 mouse model of spontaneous choroidal neovascularization. Finally, adenoassociated vector-mediated gene delivery of a truncated DICER1 variant (OptiDicer) reduced spontaneous choroidal neovascularization in JR5558 mice. Collectively, these findings significantly expand the repertoire of DICER1 in preserving retinal homeostasis by preventing both RPE degeneration and pathological neovascularization.

Clinical experience with the surgical removal of subfoveal neovascular membranes. Short-term postoperative results

BACKGROUND

Severe visual loss occurs in the presumed ocular histoplasmosis syndrome (POHS) and in age-related macular degeneration (ARMD) from subfoveal neovascularization. Although laser photocoagulation has recently been recommended for this complication in ARMD, treatment is inevitably associated with a loss of central vision. In an attempt to restore and/or preserve central vision, the authors undertook surgical removal of subfoveal neovascular membranes in these diseases.

METHODS

Patients with POHS and ARMD with reduced Snellen visual acuity to 20/80 or less were selected if there was angiographic evidence of a neovascular membrane beneath the fovea. Modern vitreoretinal techniques were used to remove the subfoveal neovascular complex.

RESULTS

The authors' first 15 patients with POHS and 19 patients with ARMD were followed for an average of 4 months postoperatively. Snellen visual acuity improved by 2 lines or more in 8 of 15 (53%) cases of POHS. Although similar improvements in Snellen visual acuity were not observed in cases of ARMD, 14 of 19 (74%) cases showed either slight improvement or stabilization of their vision postoperatively. Complications included recurrent neovascularization in 2 of 15 (13%) and 3 of 19 (16%) eyes with POHS and ARMD, respectively. No retinal detachment or preretinal proliferation was observed.

CONCLUSIONS

These results suggest that subfoveal neovascularization can be successfully removed with preservation of foveal vision in POHS and stabilization in ARMD, at least for the short term. Visual improvement was observed in POHS even after 6 months of decreased vision. Finally, visual prognosis is most dependent on the integrity of the subfoveal RPE after removal of the membrane.