Abstract
Purpose :
Vision loss from age-related macular degeneration (AMD) is currently irreversible as the retinal photoreceptors lack regenerative capacity. Regenerative cell therapies offer a promising treatment in restoring retinal function through transplanted stem cells, but face challenges in tracking the cells in vivo. This study used indocyanine green contrast (ICG) and multimodal imaging to longitudinally monitor the movement and growth of transplanted stem cells in vivo.
Methods :
A model of 12 New Zealand White rabbits with localized retinal pigment epithelial (RPE) lesions from photocoagulation represented the RPE cell atrophy causing vision loss in patients experiencing AMD. Optical coherence tomography (OCT) was used to visualize the structural layers of the retina and guide an injection of progenitor human retinal pigment epithelium cells (ARPE-19) labeled with ICG into the lesions. The ICG increased the cell signal sensitivity to allow a noninvasive, multimodal system of photoacoustic microscopy (PAM), OCT, and fluorescence imaging to longitudinally track the distribution of ARPE-19 cells in vivo for 28 days.
Results :
PAM and fluorescence imaging optimally visualized ICG labeled ARPE-19 cells at 700 nm. After an injected dose of 30 µL labeled ARPE-19 cells at a concentration of 106 cells/mL, PAM and fluorescence imaging tracked cell movement and growth. PAM signals (0.2±0.01 a.u. pre-injection) increased 20-fold (3.93±0.05 a.u.; P<0.001) and were detectable for 28 days. Fluorescence signals (0.07 ±0.01 a.u. pre-injection) initially increased by 37-fold (2.41 ±0.01 a.u.; P<0.001) and were also detectable for 28 days. Both signals detected stronger concentrations of ARPE-19 cells localized to photocoagulation lesions in the RPE. As a control, injected ICG without ARPE-19 cells did not localize to the lesions and was cleared from the body within 7 days. Histological staining with hematoxylin and eosin (H&E), as well as immunohistochemistry staining with RPE65 antibody confirmed localization and growth of ARPE-19 cells in the photocoagulation lesions as seen in OCT images.
Conclusions :
The movement and growth of subretinal transplanted ARPE-19 cells labeled with ICG can be longitudinally tracked in vivo for up to 28 days using a noninvasive multimodal system of PAM, OCT, and fluorescence imaging.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.