Stem cell-derived retinal co-grafts repair permanent retinal damage in a rat model of laser injury

Abstract

Purpose : To develop cell replacement therapies for permanent retinal damage caused by the loss of photoreceptors and retinal pigment epithelial (RPE) cells.

Methods : Athymic nude rats (2 months old, male, n=9) with laser-damaged retina were used for transplantation studies. Co-grafts (0.4mmx0.9 mm) were made of human pluripotent stem cell-derived retinal organoid (RO) sheets, and polarized RPE monolayer grown on ultrathin parylene membrane. The two entities were assembled using fibrin glue. After the retinas were damaged (~0.4mmx0.9 mm area) by a green diode laser, co-grafts were placed into the subretinal space over the damaged area using a specially designed tool. Sham surgery (n=5) rats received identical laser injuries but did not receive a tissue implant. Grafts were evaluated by optical coherence tomography (OCT) imaging. Visual function was tested at different time points (1 month, 3 months and 6 months), by optokinetic testing (OKT) and electroretinogram (ERG). Electrophysiological recording in the superior colliculus (SC) was conducted as the terminal visual functional testing followed by histology evaluation.

Results : Histology evaluation (H&E staining and immunohistochemistry) demonstrated co-graft survival, complete degradation of fibrin glue, and integration with the host retina. All co-graft implanted rats (n=9) showed the presence of transplanted cells (RPE monolayer and different retinal cell types, including rod and cone photoreceptors and bipolar cells) in the laser-damaged area. OKT and ERG results suggested improved visual preservation in the co-graft implanted rats. Mapping of the visual activities in the SC at 6 months post-surgery demonstrated a significantly higher percentage of SC sites (p<0.02, student t-test) showing visual activities (88.99±3.47% in co-graft implanted rats vs 70.13±5.83% in the sham surgery group).

Conclusions : This study describes a new stem cell-based tissue engineering technique to create retinal co-grafts by combining RO sheet and polarized RPE monolayer using fibrin glue as the bioadhesive. Our study provides strong support that stem cell-derived co-grafts made of RPE+RO sheets can repair laser-induced injuries of the retina. The development of photoreceptors in the co-graft after transplantation and the corresponding visual functional improvements make this technique suitable for treating permanent retinal injuries.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.