Embryonic stem cell trials for macular degeneration: a preliminary report

Human embryonic stem cell-derived retinal pigment epithelium in patients with age-related macular degeneration and Stargardt's macular dystrophy: follow-up of two open-label phase 1/2 studies

A primary pathological defect in the heritable eye disorder Stargardt disease is excessive accumulation of cytotoxic lipofuscin bisretinoids in the retina. Age-dependent accumulation of lipofuscin in the retinal pigment epithelium (RPE) matches the age-dependent increase in the incidence of the atrophic (dry) form of age-related macular degeneration (AMD) and therefore may be one of several pathogenic factors contributing to AMD progression. Lipofuscin bisretinoid synthesis in the retina depends on the influx of serum retinol from the circulation into the RPE. Formation of the tertiary retinol-binding protein 4 (RBP4)-transthyretin-retinol complex in the serum is required for this influx. Herein, we report the pharmacological effects of the non-retinoid RBP4 antagonist, BPN-14136. BPN-14136 dosing in the Abca4-/- mouse model of increased lipofuscinogenesis significantly reduced serum RBP4 levels and inhibited bisretinoid synthesis, and this inhibition correlated with a partial reduction in visual cycle retinoids such as retinaldehydes serving as bisretinoid precursors. BPN-14136 administration at doses inducing maximal serum RBP4 reduction did not produce changes in the rate of the visual cycle, consistent with minimal changes in dark adaptation. Abca4-/- mice exhibited dysregulation of the complement system in the retina, and BPN-14136 administration normalized the retinal levels of proinflammatory complement cascade components such as complement factors D and H, C-reactive protein, and C3. We conclude that BPN-14136 has several beneficial characteristics, combining inhibition of bisretinoid synthesis and reduction in retinaldehydes with normalization of the retinal complement system. BPN-14136, or a similar compound, may be a promising drug candidate to manage Stargardt disease and dry AMD.

In order to evaluate alternative visual acuity testing techniques, especially to discriminate between small changes and for high visual acuity, we conducted a study covering several state-of-the-art techniques. In this cross-sectional study, a homogeneous cohort of healthy and young patients (n = 33; 66 eyes) underwent ETDRS vision acuity (VA) testing, testing for contrast sensitivity (CS), VA determination with spatial frequency sweep visual evoked potentials (VEP) and a series of examinations of perifoveal retinal nerve fibre layer thickness (RNFLT) using Spectralis SD-OCT. To simulate the effect of artificial media opacity, CS, and VEP were repeated with Bangerter foils. We found that Bangerter foils can be used to reduce VA effectively measured by VA testing and VEP VA. CS correlated significantly with VA (correlation coefficients ranging from 0.54 to 0.77). VEP may be used to estimate VA; nevertheless, we found no significant correlation. RNFLT did not correlate significantly with VA. CS seems to correlate well with VA when used for high VA. All other used examinations seem to have difficulties distinguishing between small differences in VA or when the VA is high.

SummaryEmbryonic stem cells hold great promise for various diseases because of their unlimited capacity for self-renewal and ability to differentiate into any cell type in the body. However, despite over 3 decades of research, there have been no reports on the safety and potential efficacy of pluripotent stem cell progeny in Asian patients with any disease. Here, we report the safety and tolerability of subretinal transplantation of human embryonic-stem-cell (hESC)-derived retinal pigment epithelium in four Asian patients: two with dry age-related macular degeneration and two with Stargardt macular dystrophy. They were followed for 1 year. There was no evidence of adverse proliferation, tumorigenicity, ectopic tissue formation, or other serious safety issues related to the transplanted cells. Visual acuity improved 9–19 letters in three patients and remained stable (+1 letter) in one patient. The results confirmed that hESC-derived cells could serve as a potentially safe new source for regenerative medicine.

To describe different patterns of diabetic macular oedema (DMO) using a computerized alignment and averaging of sequences in optical coherence tomography (OCT) B-scans and to show the correlation of these patterns with the pathophysiology of the condition. We carried out a prospective, uncontrolled study, including 46 human subjects with untreated DMO. Enhanced OCT images were produced. We correlated different OCT patterns of DMO with ETDRS visual acuity and with the thickness of the central 1-mm of the macula. We also correlated these patterns with theories of the pathophysiology of DMO. Enhanced OCT images enabled us to examine how different layers of the macula were affected. The external limiting membrane (ELM) was clearly seen in all stages, including advanced stages. The sequence of DMO events in different macular layers can be divided into five patterns. Morphologically, DMO starts at the outer nuclear layer/Henle's layer. As the oedema progresses, cysts are seen in the fovea and the DMO spreads further into the inner nuclear layer. The ELM seems to act as a barrier for proteins and plays an important role in the development of DMO. Enhanced OCT revealed new details of DMO pathophysiology. The different morphological patterns of DMO seen in enhanced OCT may represent different levels of severity of the disease.

To evaluate the functional and anatomical outcome of patients undergoing autologous transplant of retinal pigment epithelium (RPE) and choroid after RPE tear secondary to age-related macular degeneration (AMD). Data from nine eyes of nine patients were analysed retrospectively. Examinations included fluorescein and indocyanine green angiography, fundus autofluorescence imaging, optical coherence tomography, microperimetry and determination of visual acuity (far and reading ability). Data regarding intraoperative and postoperative complications were recorded. Mean follow-up time was 18 months (range 4 months to 5 years). After surgery, far visual acuity improved or remained stable (±3 lines) in three of nine eyes and for the near visual acuity in three of nine eyes. Visual acuity decreased postoperatively at the last follow-up in four eyes mainly because of postoperative complications, i.e. retinal detachment due to proliferative vitreoretinopathy, retinal artery occlusion, pucker and fibrosis of the graft. In one case, retinal stimuli were restored over the scotoma as seen in microperimetry. Autologous transplant of RPE and choroid is a therapy option for RPE tears. Retinal stimuli can be restored in selected cases. Numerous intra- and postoperative complications compromise the functional prognosis and outcome.

To compare the outcome after choroidal neovascular (CNV) membrane excision and retinal pigment epithelium (RPE) transplantation and make further evaluation of two types of RPE grafts on the visual function in patients with neovascular age-related macular degeneration (AMD), complicated by massive subretinal haemorrhage. We retrospectively reviewed 80 patients who underwent CNV membrane excision with or without RPE transplantation. Two types of RPE grafts were adopted, RPE-Bruch's membrane complex graft (subgroup 1) and RPE monolayer sheet graft (subgroup 2). Outcome measures included pre- and postoperative visual acuity score (VAS), clinical findings, complications and recurrence rates. The mean VAS [Early Treatment of Diabetic Retinopathy Study (ETDRS)] in the CNV membrane excision group was 11.06±18.28 at baseline and 14.41±16.86 at follow-up (p=0.12) in a mean follow-up period of 24.35±9.31months. While in subgroup 1, VAS increased from 22.62±23.72 to 35.50±24.46 (p=0.02) in a mean period of 20.63±6.25months. The percentage of visual acuity (VA) improvement (at least two or more lines changed) in subgroup 1 is 62.5%, which is significantly higher than that in CNV excision group (23.5%), p=0.02. In subgroup 2, VAS increased from16.61±27.98 to 29.16±23.80 (p=0.02) in a mean period of 21.72±11.09months. The percentage of VA improvement in subgroup 2 is 58.0%, which is also significantly higher than that in CNV excision group (23.5%), p=0.02. Postoperative VA elevation was comparable between the two subgroups (p=0.05). Complications including retinal detachment, proliferative vitreal retinopathy and CNV recurrence occurred in both techniques. Central fixation stability was observed in eight eyes in subgroup 1 and five eyes in subgroup 2. The autologous RPE transplantation can increase the vision of patients with haemorrhagic AMD. Two types of autologous RPE grafts were both effective and comparable in restoring visual function and central fixation stability.

This chapter summarizes the design and outcomes of the first clinical trials of human embryonic stem cell (hESC)-derived retinal pigment epithelial (RPE) cell transplantation therapy for retinal regeneration. The MA09-(hESC) line was derived from the blastomere stage of a donated embryo and expanded on mitotically inactivated mouse embryonic fibroblasts according to the Good Manufacturing Practices. The MA09-hRPE cells were then tested for safety and terminal differentiation into mature RPE cells by gene expression analysis, karyotyping, phagocytosis assay, and differentiation and purity evaluation by way of morphology, quantitative polymerase chain reaction, and quantitative immune staining for RPE and hESC markers. Two phase I/II open-label, multicenter, prospective clinical trials investigating the safety of subretinal injection of hESC-derived RPE cell suspension in patients with end-stage atrophic age-related macular degeneration (AMD) and Stargardt macular dystrophy (SMD) were performed. The visual outcomes were encouraging with some patients gaining more than ten letters in both groups; however, these results must be tempered by the lack of a control group, poor initial visual acuity, short follow-up, and limited number of patients. Thirteen of eighteen patients (72%) developed areas of increased subretinal pigmentation, some of which appeared to correlate to hyper-reflective bands on optical coherence tomography. The transplanted cells showed no evidence of tumor formation, adverse preretinal RPE cell engraftment, or clinically apparent rejection. Aside from a case of acute postoperative endophthalmitis, there were no issues with the surgical procedure itself. These promising results suggest that hESC-derived RPE cells could represent a novel treatment paradigm for retinal degenerations hallmarked by tissue loss or dysfunction.

Documentation of Intraretinal Retinal Pigment Epithelium Migration via High-Speed Ultrahigh-Resolution Optical Coherence Tomography

Choroideremia Gene Therapy

Advanced macular degeneration is a major cause of visual impairment in the United States with over one million people affected by the disease. Although treatments exist for the wet form of age-related macular degeneration (AMD), the severe vision loss accompanying geographic atrophy in dry AMD or Stargardt’s macular dystrophy remains untreatable. In both diseases, the retinal pigment epithelium (RPE) becomes compromised and eventually dies with subsequent loss of the photoreceptors. We set out to replace this diseased RPE with healthy human embryonic stem cell-derived RPE (hESC-RPE) in order to rescue photoreceptors and visual function. In preclinical work using mice with retinal dystrophies, hESC-RPE cells injected into the subretinal space engrafted successfully and improved visual function. In the first ever clinical trial of subretinal hESC-RPE transplantation in humans, we reported on the first two patients, one with dry AMD and one with Stargardt’s. Functional improvements were observed, but our conclusions were limited by the short follow-up time, lack of control group, and poor initial visual acuity. Importantly, no adverse events related to the treatment, such as hyperproliferation, tumorigenicity, inflammation, infection, or rejection, were noted in either patient. This first-in-human safety study has opened the door to future studies looking at patients with less advanced disease, utilizing a weaker immunosuppressive regimen, and including patients with other diseases that result in RPE loss. The ultimate goal is the reduction of human suffering by meeting an otherwise unmet medical need.

AimTo compare retinal pigment epithelium–Bruch's membrane (RPE–BM) complex thickness in patients with early and intermediate dry age-related macular degeneration (AMD) and age-matched controls using spectral domain optical coherence tomography (SD-OCT).MethodsIn...

VEGF and ELAVL1/HuR protein levels are increased in dry and wet AMD patients. A new tile in the pathophysiologic mechanisms underlying RPE degeneration?

Purpose In the pathophysiolgy of dry (atrophic) age related macular degeneration (AMD) aging of the retinal pigment epithelium (RPE) plays a key role. Accumulation of lipofuscin granules in the RPE cells represents a common downstream pathogenetic pathway in AMD. Lipofuscin is derived from chemically modified residues of incompletely digested photoreceptor outer segment discs. Detection of lipofuscin in vivo is possible by using fundus autofluorescence (FAF) imaging. The clinical application and possible implications of autofluorescence imaging in dry AMD will be discussed. Methods When stimulated with light in the blue to green range, lipofuscin granules emit a characteristic yellow fluorescence. FAF imaging using a scanning laser ophthalmoscope allows visualization of the topographic distribution of lipofuscin over large retinal areas. Examples of FAF images will be presented to demonstrate various FAF patterns and to discuss the clinical significance of these findings. Results In areas of geographic atrophy FAF images show very low autofluorescence intensity. This is due to the loss of RPE cells including the lipofuscin granules. In the junctional zone between atrophic and normal retina, levels of increased autofluorescence intensity may occur due to excessive accumulation of lipofuscin in the RPE cells. Longitudinal observations further suggest that the extension of the total area with increased autofluorescence intensity surrounding atrophy at baseline has a strong positive correlation with atrophy progression rate over time. Conclusion FAF imaging is an important diagnostic tool to follow the progression of dry AMD and other degenerative macular diseases and should always be considered in cases were the status of the RPE is unknown.

Conventional time-domain optical coherence tomography (OCT) has become an important tool for following dry or exudative age-related macular degeneration (AMD). Fourier-domain three-dimensional (3D) OCT was recently introduced. This study tested the reproducibility of 3D-OCT retinal thickness measurements in patients with dry and exudative AMD. Ten eyes with dry AMD and 12 eyes with exudative AMD were included in the study. Sets of three OCT 6 × 6-mm raster scans were taken by one operator. Mean retinal thickness was calculated for 36 areas. Coefficients of variation (CoV) were calculated for each patient and area. For analysis, two separate areas (central and peripheral) were defined. Generalized estimating equations (GEEs) were applied to all 36 subfields in order to analyse possible differences in CoV and mean retinal thickness between dry and exudative AMD. Mean retinal thickness values were significantly larger in the central area in exudative AMD (p < 0.001). Mean CoV for exudative AMD was 3.7% (standard deviation [SD] 1.4%). Mean CoV for dry AMD was 1.8 (SD 0.6%). The reproducibility of retinal thickness measurements was significantly less in exudative AMD (p = 0.009). Reproducibility of 3D-OCT retinal thickness measurements was good in both groups. However, reproducibility was significantly better in dry AMD than in exudative AMD.