Abstract
Purpose :
Stem cell derived retinal pigment epithelial (RPE) cell products have been developed for refractory retinal diseases. It has been reported that leaked RPE graft cells are frequently induced to form an epiretinal membrane (ERM). We investigated surgical administration of RPE cells for prevention of cell leakage and ERM formation in monkey models.
Methods :
In our preceding monkey study, we observed ERMs in 100%(3/3) of monkeys without fluid air exchange and 15.0%(3/20) with it (Fisher’s exact test; p<0.05), confirming the ERM suppression effect of fluid air exchange. So, this study was conducted on 6 monkeys under the following conditions. Following vitrectomy, a suspension of HLCR011 human induced pluripotent stem (hiPS) cell-derived RPE cells was administered (5.0×105 cells in 50 µL/eye) with a 38G subretinal cannula via the vitreous cavity into the right eyes of cyclosporin A-immunosuppressed monkeys. After injecting the cell suspension into the subretinal space, the vitreous cavity was cleaned with intraocular perfusion fluid and then subjected to fluid air exchange. After surgery, the monkeys were placed in a supine position for at least 3 hours. Clinical signs, slit lamp, fundus photography, fluorescein fundus angiography, fundus autofluorescence photography (FAF), and Optical Coherence Tomography(OCT) were performed over the 13-week observation period. The animals were examined histopathologically and immunohistochemically with human specific PMEL17 antibodies to confirm RPE cell engraftment.
Results :
No ERM developed(0/6) during the 13-week period. Brown pigment-laden cells (hiPS-RPE cells) were observed broadly from the site of administration into the RPE layer. PMEL17-positive sites in the RPE layer were observed in consecutive sections in the area of the administration in all monkeys at 4 and 13 weeks. The hiPS-RPE cell monolayer integrated with the host RPE layer covered a wide area. In vivo imaging with OCT and FAF was only able to detect RPE cells that were engrafted in multiple layers.
Conclusions :
We confirmed that the improved fluid air exchange procedure and postoperative supine positioning prevented development of ERMs. The histopathological and immunohistochemical results showed that the hiPS-RPE cells were also widely engrafted in the form of a monolayer integrated with the host RPE layer in addition to multilayered graft observed by optical instruments.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.