Subretinal Transplantation of Human Central Nervous System Stem Cells Stimulates Controlled Proliferation of Endogenous Retinal Pigment Epithelium.

Trevor J. McGill,Ann Tsukamoto,Alexandra Capela,Stephen Huhn,Linda Osborne,Bin Lu,Jonathan Stoddard

doi:10.1167/tvst.8.3.43

Abstract

PurposeThe loss of retinal pigment epithelial (RPE) cells is a feature common to age-related macular degeneration (AMD) and retinitis pigmentosa (RP) and multiple early phase clinical trials are underway testing the safety of RPE cell replacement for these diseases. We examined whether transplantation of human neural stem cells into the subretinal space could enhance the endogenous proliferative capacity of the host RPE cell to regenerate.MethodsHuman central nervous system stem cells (HuCNS-SC) were isolated from enzymatically treated brain tissue using flow cytometry. Pigmented dystrophic Royal College of Surgeons (RCS) and S334ter-4 rats treated with oral bromodeoxyuridine (BrdU) received a unilateral subretinal injection of 1.0 × 105 HuCNS-SC cells at either postnatal day 21 or 60. Animals were sacrificed at 90, 120, and 150 days of age. Eyes were fixed processed for cryostat sectioning. Sections were immunostained with Stem101, Ku80, RPE65, OTX1/2, BrdU, and CRALBP antibodies and analyzed via confocal microscopy.ResultsRCS rats that received transplantation of HuCNS-SC had significantly more (approximately 3-fold) Ki67-positive or BrdU-labelled host RPE cells adjacent to the HuCNS-SC graft than controls. Significantly increased host RPE cell proliferation as a result of HuCNS-SC transplantation also was confirmed in S334ter-line 4 transgenic rats with higher proliferation observed in animals with longer posttransplantation periods.ConclusionsThese results suggest that controlled proliferation of endogenous RPE by HuCNS-SC may provide another mechanism by which RPE cell diseases could be treated.Translational RelevanceEngaging the capacity for endogenous RPE cell regeneration in atrophic diseases may be a novel therapeutic strategy for degenerative diseases of the RPE and retina.

Highlights

The retinal pigmented epithelium (RPE) is a layer of highly polarized supportive cells that are critical for survival and function of the retina
Using long-term continuous oral administration of the thymidine analogue bromodeoxyuridine (BrdU), we demonstrated that RPE proliferation is augmented preferentially in the RPE layer directly adjacent to the HuCNS-SC graft in both rat models, indicating that this phenomenon is directly related to the transplanted cells, is not model-specific, and appears independent of the status of the underlying RPE
In all our transplantation studies to date in which HuCNS-SC were injected into the subretinal space, we never observed donor cells engraft in the RPE layer nor to express RPE65.9,11 Because RPE cells are thought to be mostly postmitotic, we decided to further investigate this initial observation and quantified the number of RPE65þKi67þ cells in transplanted and control eyes of Royal College of Surgeons (RCS) rats injected and sacrificed at different time points

Summary

Introduction

The retinal pigmented epithelium (RPE) is a layer of highly polarized supportive cells that are critical for survival and function of the retina. Microvilli from the apical side of the RPE protrude into the photoreceptor layer and envelop photoreceptor outer segments (OS). This intimate connection between the RPE and photoreceptors enables the RPE to efficiently phagocytose shed OS, recycle oxidized photopigments, and provide additional. Critical trophic support to the outer retina while removing waste.[1,2] dysfunction or death of the RPE can have significant consequences for the survival of the host retina and for visual function.[3] millions of patients worldwide suffer from progressive and permanent vision loss due to RPE death/dysfunction in diseases, such as advanced age-related macular degeneration (AMD), Stargard’s macular dystrophy, and certain forms of retinitis pigmentosa (RP)

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Conclusion