Generation of a new immunodeficient rat model of retinal degeneration with LSL TdTomato reporter and TdTomato-Pcp2 expression

Purpose To develop an immunodeficient retinal degenerate (RD) rat model with fluorescent label for studying retinal degeneration and transplant-host connectivity. Methods Gene constructs for CAG-LSL-TdTomato and Pcp2-Cre were developed and injected into rat embryos at Envigo. The LSL TdTomato reporter strain, created on immunodeficient RhoS334ter-3 rats (RRRC#539), was bred to homozygosity at UCI (strain SD-Foxn1rnuTg((Rho-S334X)3,CAG-TdTomato)1010Mjsuc , “RNT”). The second gene construct Pcp2-Cre was injected into Long-Evans (LE) rat embryos, resulting in two Pcp2-cre founders (strain PCP2 Cre-1105 RKI, “Pcp2”), with targeted and targeted/random insertion. Founders were mated with an LE male and a foxn1+/- NIH nude female. F1 offspring was bred to homozygosity and immunodeficiency. Homozygous rats of both strains were crossbred to generate TdTomato-Pcp2 RD (“RTP”) rats. Retinas were processed for immunohistochemistry for various retinal markers. GFP-expressing rat retinas were transplanted to 6 week old “RTP” rats and analyzed 37 and 77 days post-surgery (pilot experiments). Results TdTomato-Pcp2 RD rats exhibit RD similar to the original Rho S334ter-3 rat strain, with < 1 row photoreceptors remaining at 1 month. Retinas with targeted Pcp2 insertion showed TdTomato in retinal interneurons and cones. Retinas with random Pcp2 insertion exhibited additional TdTomato in RPE, glial, and endothelial cells. Pcp2-TdTomato expression was useful to define transplant-host boundaries. Conclusions We created an unique RD rat model for studying retinal transplant connectivity. The RD LSL-TdTomato reporter rat can also be used to generate RD rats with other cell-specific labels using the cre/lox system. Translational relevance This newly created rat model is useful for cell therapy studies.