Improving human neural stem cell formulations for geographic atrophy treatment

Abstract

Purpose : Subretinal transplantation of human neural stem cell (hNSC) clusters has been associated with slowed progression of geographic atrophy in age-related macular degeneration (AMD) patients. The main goals of this study were to improve the hNSC product by developing a single-cell suspension formulation and to determine if it improves cell spreading in the subretinal space of the RCS rat.

Methods : RCS rats were subretinally injected at postnatal day 21 (P21) with either a single-cell suspension or a cluster formulation of hNSCs at a dose of 150,000 cells in a 2 μL volume. The contralateral control eye was left unoperated or injected with balanced salt solution. Optokinetic tracking (OKT) was evaluated at P60 and P90 to measure preservation of visual performance. Whole globes were harvested at P60 for immunofluorescence (IF). We stained retinal cross-sections with a human specific marker (STEM121) and DAPI. Using confocal images, cell spread of hNSCs and outer nuclear layer (ONL) area were quantified. To decrease toxicity from long-term cyclosporine administration, we dosed RCS rats with decreasing concentrations of ad libidum cyclosporine water. Blood concentration was measured at P35, P100, and P200 to ensure therapeutic dose.

Results : At P60, IF showed a clear presence of STEM121-positive cells in the subretinal space which correlated with increased ONL area. Outside of treated areas, the retina showed progressive photoreceptor degeneration. The single-cell suspension formulation doubled cell spread compared to the original cluster formulation. Single-cell suspension injected eyes also had significantly improved visual performance over control groups at P60 and P90. We identified a new cyclosporine dose that resulted in long term (~P200) therapeutic blood concentration levels that decreased toxicity in our RCS rats.

Conclusions : A novel single-cell suspension of hNSCs with high cell viability was successfully generated. The single-cell suspension showed improved spread in the subretinal space over the previous cluster formulation providing neuroprotection to a larger portion of the eye. This product may be able to improve hNSC transplantation treatments for AMD eyes with geographic atrophy. Our new cyclosporine dosing regimen is likely to reduce adverse effects during long-term administration.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.