Subretinal Transplantation of Forebrain Progenitor Cells in Nonhuman Primates: Survival and Intact Retinal Function

Abstract

Purpose Cell-based therapy rescues retinal structure and function in rodent models of retinal disease, but translation to clinic will require more information about consequences of transplantation in an eye closely resembling the human eye. Therefore we explored donor cell behavior using human cortical neural progenitor cells (hNPCctx) introduced into the subretinal space of normal rhesus macaques. Methods hNPCctx transduced with Green Fluorescent Protein (hNPCctx-GFP) were delivered bilaterally into the subretinal space of six normal adult rhesus macaques under conditions paralleling those of the human operating room. Outcome measures included clinical parameters of surgical success, multifocal electroretinogram (mfERG) and histopathological analyses performed between 3 and 39 days post-engraftment. To test the effects of GFP transduction on cell bioactivity, hNPCctx –GFP from the same batch were also injected into RCS rats and compared with non-labeled hNPCctx. Results Studies using RCS rats indicated that GFP transduction did not alter the ability of the cells to rescue vision. After cells were introduced into the monkey subretinal space by a pars plana transvitreal approach, the resulting detachment was rapidly resolved and retinal function showed little or no disturbance in mfERG recordings. Retinal structure was unaffected and no signs of inflammation or rejection were seen. Donor cells survived as a single layer in the subretinal space and no cells migrated into the inner retina. Conclusions Human neural progenitor cells can be introduced into a primate eye without complication, using an approach that would be suitable for extrapolation to human patients.

A Subsequent Human Neural Progenitor Transplant into the Degenerate Retina Does Not Compromise Initial Graft Survival or Therapeutic Efficacy

“…Consistently, long-term graft survival was seen after NPC transplantation into the eye of RCS rats up to P280, 21 rd mice, 55 or monkeys briefly treated postsurgically with topical steroids without cyclosporine (up to 5 weeks). 22 The T cell-mediated immune response is known to play a major role in graft rejection. 36,[56][57][58] For example, CD8…”

“…In addition, their ability to migrate long distances after subretinal injection permits the injection site to be targeted at the transient zone to avoid damaging macular vision that is already fragile from degeneration. Finally, hNPC ctx do not compromise normal retinal function after subretinal transplantation into nonhuman primates 22 and do not appear to form tumors following transplantation in the central nervous system (CNS). [23][24][25][26][27][28] While there are several clinical trials using stem/ progenitor cells to treat retinal degeneration (ClinicalTrials.gov), some fundamental questions remain to be addressed.…”

Stem Cells for Retinal Replacement Therapy

“…Some of the transplanted NSCs integrate into inappropriate retinal layers with the age of the host having an important role in determining NSC fate [40][41][42], whereas other NSCs do not integrate but survive in the subretinal space with limited expression of retinal cell phenotypes [40]. As with RPCs, integration increases when NSCs are transplanted into young or injured host retina [43,44], and at the other extreme, NSCs transplanted into healthy adult monkey show little migration or integration, forming a monolayer of stable NSCs [45]. Integration may not be necessary to rescue photoreceptor cell loss; however, NSCs derived from committed CNS tissue rescue photoreceptor cells in animal models of retinal disease presumably by release of growth factors and/or phagocytosis of photoreceptor cell outer segments shed during the early steps of vision [46,47].…”

Subretinal Injection: A Review on the Novel Route of Therapeutic Delivery for Vitreoretinal Diseases

“…In rats, photoreceptor degeneration can be prevented by subretinal transplantation of human fetal lung fibroblasts expressing the ciliary neurotrophic factor gene [66] , and laser-induced choroidal neovascularization can be inhibited by subretinal transplantation of RPE overexpressing fibulin-5 [67] . Of all of the cell types, progenitor cells and stem cells, such as human neural progenitor cells [68] , human retinal progenitor cells [69] , progenitor cells from the porcine neural retina [70] , forebrain progenitor cells [71] , brain-derived precursor cells [72] , human embryonic stem cell-derived retinal progenitors [73] , human RPE stem cells [74] , human bone marrow mesenchymal stem cells [75] , and rat mesenchymal stem cells [76] , are the most popular when given subretinally for cell replacement therapy for retinal degeneration. All these cells are considered to have the capability to survive and migrate into retinal layers and restore retina function or induce cell regeneration in different types of retinal cells when delivered via the subretinal route.…”