Safety outcome of subretinal human embryonic stem cell-derived pigment epithelium (hESC-RPE) transplantation in Yucatan mini-pigs with oral or intravenous immunosupression.

Abstract

Purpose: To evaluate retinal morphology after subretinal transplantation of a human embryonic stem cell-derived retinal pigment epithelium (hESC-RPE) monolayer in Yucatan mini-pig eyes, dependent on oral or intravenous tacrolimus immunosuppression regimen as a safety model for future human trials of dry AMD treatments.

Methods: Five Yucatan mini-pigs underwent vitrectomy with the creation of a localized subretinal saline solution bleb. A limited peripheral retinotomy was performed and the transplant consisting of hESC-RPE polarized cells cultured on parylene membranes was placed into the subretinal space using a specially designed inserter. Animals received tacrolimus during the 1 month follow-up either orally (group 1; n=2) or intravenously, through a vascular access port and a continuous infusion pump (group 2; n=3). Examinations included in vivo spectral domain optical coherence tomography (SD-OCT) and fluorescein angiography (FA). Ex vivo histological analyses included hematoxylin and eosin (H&E) with immunohistochemical anti-RPE65 (RPE cell marker), rhodopsin and TRA-1-85 (human cell marker) antibody evaluation.

Results: All animals reached the 1 month follow-up with thorough in vivo and ex vivo documentation. Both groups achieved blood levels of tacrolimus within the therapeutic range in humans (4-10ng/mL). No animal had retinal detachment or evidence of unduly increased intraocular inflammation. SD-OCT showed excellent placement for the majority of the implant with only rare small areas of folds in the parylene substrate. FA similarly demonstrated no anterior or posterior segment leakage. Immunohistochemical analysis showed hESC-RPE cell survival in both groups.

Conclusions: In this animal model, pars plan vitrectomy followed by subretinal RPE-parylene sheet implantation was very well tolerated. The immunosuppression delivered either via intravenous or oral was effective in reducing the inflammation induced by the xenograft. The optimum immunosuppression to be used in patients as this approach is advanced will require clinical evaluation.

Keywords: 721 stem cells • 412 age-related macular degeneration • 555 immunomodulation/immunoregulation