Preventing visual function loss in the rd10 mouse model of retinitis pigmentosa using gene editing

Currently, there is no known cure for retinitis pigmentosa (RP). Even if some treatments can slow down the progression of the disease, none of them can effectively stop retinal degeneration. This study exploits the possibility of an early intervention in photoreceptor progenitors aiming at preventing cell death. For this purpose, we selected the rd10 mouse model, which carries a point mutation in a gene associated with human RP. We designed a CRISPR/Cas9 gene editing system to repair the mutation taking advantage of the increased activity of the homologous directed repair mechanism in dividing cells. The efficiency of the editing system (composed of guide RNA, Cas9, and DNA repair template) was first tested in vitro in neural progenitor cells derived from rd10 mice (52.8±11.1%, n=3). The constructs were then injected in vivo in the subretinal space of rd10 pups either at postnatal day (P) 3 (early treated, ET) or at P8 (late treated, LT); we also tried a P3-P8 combined treatment (multiple treated, MT). One eye was injected, while the other one was kept as internal control. The injection was followed by electroporation (electric field: 40 V/cm). Histological analysis of the eyes showed GFP expression in the photoreceptors layer starting from 2 days after electroporation. The visual acuity was measured at P30, P60 and P90 with the optomotor response test in ET, MT, LT, sham treated (ST), non-treated rd10 (NT), and WT (WT) mice. The treated eye showed a higher visual acuity than the control eye in ET, MT and LT for all the time points tested, despite a decreased visual acuity at P90 (p