Proof of concept for AAV2/5-mediated gene therapy in iPSC-derived retinal pigment epithelium of a choroideremia patient

Abstract

Inherited retinal dystrophies (IRDs) comprise a large group of genetically and clinically heterogeneous diseases that lead to progressive vision loss, for which a paucity of disease-mimicking animal models renders preclinical studies difficult. We sought to develop pertinent human cellular IRD models, beginning with choroideremia, caused by mutations in the CHM gene encoding Rab escort protein 1 (REP1). We reprogrammed REP1-deficient fibroblasts from a CHM-/y patient into induced pluripotent stem cells (iPSCs), which we differentiated into retinal pigment epithelium (RPE). This iPSC-derived RPE is a polarized monolayer with a classic morphology, expresses characteristic markers, is functional for fluid transport and phagocytosis, and mimics the biochemical phenotype of patients. We assayed a panel of adeno-associated virus (AAV) vector serotypes and showed that AAV2/5 is the most efficient at transducing the iPSC-derived RPE and that CHM gene transfer normalizes the biochemical phenotype. The high, and unmatched, in vitro transduction efficiency is likely aided by phagocytosis and mimics the scenario that an AAV vector encounters in vivo in the subretinal space. We demonstrate the superiority of AAV2/5 in the human RPE and address the potential of patient iPSC–derived RPE to provide a proof-of-concept model for gene replacement in the absence of an appropriate animal model.

Subretinal AAV2.COMP-Ang1 suppresses choroidal neovascularization and vascular endothelial growth factor in a murine model of age-related macular degeneration

“…Subretinal AAV2 localization was first tested with well-established reporter genes: AcGFP, which has a fluorescent product (Cereso et al, 2014; Cronin et al, 2012; Li et al, 2008; Zhang et al, 2012, 2015), and LacZ, which has a chromogenic product (Hojo et al, 2004), to validate successful inoculation of the targeted tissue.…”

Strategies for retinal cell generation from human pluripotent stem cells

“…Often an affected gene or specific mutation will lack a corresponding animal model, making pre-clinical treatment studies difficult or impossible to extrapolate to humans. hiPSCs provide a unique opportunity to generate personalized models of disease to be used in a variety of studies, from determining pathology to demonstrating intervention efficacy (57). Additionally, they are a source of autologous cells for transplantation.…”

Looking into the future: Using induced pluripotent stem cells to build two and three dimensional ocular tissue for cell therapy and disease modeling

“…In addition to the two studies discussed here (Singh et al, 2013b; Yang et al, 2014), a number of other studies have discussed other forms of retinal degenerative diseases (Cereso et al, 2014; Li et al, 2014; Polinati et al, 2014). Combined together, all these studies have provided the critical first steps that were needed to demonstrate the utility of patient-specific iPS cells for in vitro disease modeling.…”