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Elliott Sohn, Chunhua Jiao, Robert Mullins, Woojin Jung, Stephen Russell, Edwin Stone, Budd Tucker; Comparison of intraocular retinal pigment epithelial (RPE) cell injections in vitrectomized wild type pigs. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1948.
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Various sources of RPE cells have been proposed for cell replacement therapy (e.g. in the subretinal space to treat geographic atrophy) and in generating models of proliferative vitreoretinopathy (PVR). In this pilot study we sought to determine the effects of induced pluripotent stem cell derived RPE cells (iPS-RPE) delivered to the subretinal space and allogeneic RPE cells injected into the vitreous cavity of vitrectomized wild-type mini-pigs.
23 gauge vitrectomy was performed in 12-week-old yucatan miniature swine (n=10). Three treatment cohorts consisted of those given blebs of balanced salt solution alone (controls); blebs followed by intravitreal injection of porcine-derived GFP-positive RPE cells (250,000 cells, RPE group); and subretinal blebs of porcine-derived, GFP-positive iPS-RPE cells (250,000 cells, iPS-RPE group). Indirect ophthalmoscopy, fundus photography and spectral-domain-OCT were performed at weekly post-op intervals. Post-op vitreous samples were screened for inflammatory cytokines using a commercial cytokine array and total proteins were evaluated on silver-stained SDS-PAGE gels for proteomic analysis.
Vitreous membranes were seen in all eyes in the iPS-RPE cell group but no PVR or retinal detachment was observed. Epiretinal membranes and retinal detachment were seen in a third of eyes in the RPE group. No PVR or vitreous membranes were seen in the saline controls. At post-op week 3, vitreous IL-8 levels were elevated in the iPS-RPE group compared to the porcine RPE and saline controls (image 1); these levels were higher than those observed in post-op weeks 1 and 2. IL-12 levels were greater in post-op week 3 compared to post-op week 1 of the iPS-RPE group (image 2). TGF-beta levels were very low or below limits of detection in all eyes. Silver staining revealed a distinct subset of bands in the vitreous of pigs that received iPS-RPE cells. MALDI-MS of one of these bands identified several proteins including transthyretin and beta-2-microglobulin.
Subretinal injection of iPS-RPE cells in wild-type mini-pigs may result in an increase in inflammatory response specific to particular cytokines. Exogenous intravitreal RPE cells may result in a modest rate of PVR. Further research is needed to verify these findings.
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