Choroidal neovascularization (CNV) is the defining characteristic feature of the wet subtype of age-related macular degeneration (AMD) and may result in irreversible blindness. Based on anti-vascular endothelial growth factor (anti-VEGF), the current therapeutic approaches to CNV are fraught with difficulties, and mammalian target of rapamycin (mTOR) has recently been proposed as a possible therapeutic target, although few studies have been conducted. Here, we show that a recombinant adeno-associated virus-delivered mTOR-inhibiting short hairpin RNA (rAAV-mTOR shRNA), which blocks the activity of both mTOR complex 1 and 2, represents a promising therapeutic approach for the treatment of CNV. Eight-week-old male C57/B6 mice were treated with the short hairpin RNA (shRNA) after generating CNV lesions in the eyes via laser photocoagulation. The recombinant adeno-associated virus (rAAV) delivery vehicle was able to effectively transduce cells in the inner retina, and significantly fewer inflammatory cells and less extensive CNV were observed in the animals treated with rAAV-mTOR shRNA when compared with control- and rAAV-scrambled shRNA-treated groups. Presumably related to the reduction of CNV, increased autophagy was detected in CNV lesions treated with rAAV-mTOR shRNA, whereas significantly fewer apoptotic cells detected in the outer nuclear layer around the CNV indicate that mTOR inhibition may also have neuroprotective effects. Taken together, these results demonstrate the therapeutic potential of mTOR inhibition, resulting from rAAV-mTOR shRNA activity, in the treatment of AMD-related CNV.
Purpose To assess differences in the progression of macular atrophy (MA) between neovascular age‐related macular degeneration (AMD) subtypes and to identify the risk factors associated with the foveal involvement among patients with MA undergoing long‐term anti‐vascular endothelial growth factor (VEGF) treatment. Methods Eighty eyes of 80 patients with neovascular AMD who developed incident MA following anti‐VEGF therapy were retrospectively included. Macular atrophy (MA) was quantified using autofluoresence (AF) images within 24 months after the onset of MA, and the enlargement rate was compared between neovascular AMD subtypes. Regression models were constructed to explore relationships between foveal involvement in MA and baseline characteristics. Results The growth rate of MA was 0.18 mm2/year for type 1 neovascularization (NV), 0.24 mm2/year for type 2 NV, and 1.21 mm2/year for type 3 NV; differences between groups were significant (p = 0.022). Multivariate logistic regression analysis revealed that thin subfoveal choroidal thickness (p = 0.028), presence of subretinal drusenoid deposit (p = 0.005), type 2 or 3 NV (p = 0.023), and geographic atrophy in the fellow eye (p = 0.035) were significant risk factors for MA with foveal involvement. The number of injections showed no significant association with the progression or the foveal involvement in MA. Conclusions The progression of MA in patients with neovascular AMD undergoing anti‐VEGF treatment differed significantly depending on the subtype of neovascularization. The risk of foveal involvement in MA was associated with the baseline factors or phenotype of neovascular AMD rather than with injection frequency of anti‐VEGF.
Background The mechanistic target of rapamycin (mTOR) pathway is a potential target to inhibit pathologic processes in choroidal neovascularization. However, the exact role of mTOR signaling in the development of CNV remains obscure. In this study, we assessed the role of mTORC1 and mTORC2 as well as the effect of rapamycin (sirolimus) on choroidal neovascularization (CNV) in a laser-induced mouse model. Methods In experiment A, we observed the natural course of CNV development and the dynamics of mTOR-related proteins during the 12 days after the laser injury. The expression of mTOR-related proteins was evaluated using Western blot (WB). Cryosections of CNV-induced mice were immunostained for the visualization of the vascular and extravascular components of the CNV. Experiment B was performed to confirm the critical period of mTOR signaling in the development of laser-induced CNV, we administered rapamycin before and/or during the active period of mTOR complexes. WB and immunofluorescence staining was performed to evaluate the mode of action and the effect of mTOR inhibition on CNV development. Results In experiment A, we detected high levels of p-mTOR S2448 and p-mTOR S2481 from the 5th to 12th day of laser injury. Immunofluorescence imaging of cryosections of mice sacrificed on day 7 revealed greater co-immunoreactivity of p-mTOR S2448 positive cells with CD11b and F4/80, while p-mTOR S2481 positive cells showed colocalization with CD31, α-SMA, and cytokeratin. In experiment B, rapamycin injection during the active period of mTOR signaling demonstrated near-complete inhibition of CNV lesion as well as significant induction of autophagy. Conclusion Our study suggests the mTOR as a critical player during CNV development in laser-induced mouse model through differentially acting with the mTORC1 and mTORC2. mTORC1 activity was high predominantly in inflammatory cells in CNV lesion, while mTORC2 activity was higher in vascular components and the RPE. Electronic supplementary material The online version of this article (10.1186/s12964-019-0380-0) contains supplementary material, which is available to authorized users.
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