Objective

Retinal organoid (RO) are 3D retina-likes structures that recapitulate the morphological and functional features of the human retina. Since the last decade, emergence of RO allows us access to more physiologically relevant model system for clinical transplantation. Indeed, more complex system can allow us to obtain more functional cells, essential criteria for graft cell survival. In this context, we develop RO from human induced pluripotent stem cells (hiPSC) and transplant this cell in subretinal into a dystrophic rat model, RCS rat. We evaluated the ability of OR to survive, integrate in vivo and slow down the degeneration of photoreceptors.

Methods

hiPSC-RO were differentiated until D46 followed the protocol previously described by Chichagova, and characterized by morphology and immunofluorescence.

RCS rats have a mutation in the Mertk gene leading to an inability to phagocytosis the outer segments of PR, resulting in accumulation of outer segment debris and subsequently, degeneration of PR. We transplanted RCS rats aged 22 days with subretinal injection of hiPSC-RO (n=17) or balanced salt solution (n=10) into the left eye. Control group do not receive any chirurgical procedure (n=23). For each group, animals will be divided into 3 groups that corresponds to 3 different time point for behavioral functional assessment and post-mortem analysis: 3-, 7- and 13-weeks post-transplantation.

Results

At D46, hiPSC-RO expressed typical retinal markers such as PAX6 (eye filed fate - 26.18 ± 3.73%), HuC/D (amacrine / ganglion cells - 42.43 ± 2.92%), Recoverin (photoreceptors precursors - 16.59 ± 1.55%), NRL (rods-8.14 ± 1.01%) and RXRϒ (cones - 11.95 ± 2.94%). Presence of transplanted cells was showed with expression of KI67, specific to human, into retina of rat at 13-weeks post-transplantation. We observed that hiPSC-RO integration lead to an increase of visual acuity of transplanted eyes (0,65454545 c/d ± 0,03) and contralateral eyes (0.,7 ± 0.2) compared to control eyes (0,10344828 c/d ± 0,01 and 0,09310345 ± 0.1 respectively) at 16 weeks post-natal.

Conclusion

In our study, we transplanted hiPSC-RO into RCS rat, a model of retinal degeneration. We showed that transplantation lead to an increase of visual acuity in transplanted eyes, but surprisingly, also in contralateral eye. More investigation has to be made to explain how transplantation into right eye could affect vision of left eye.