Autologous translocation of the choroid and retinal pigment epithelium in patients with geographic atrophy

Tissue Engineering of Outer Blood Retina Barrier for Therapeutic Development

Age related macular degeneration and other retinal degenerative disorders are characterized by disruption of the outer blood retinal barrier (oBRB) with subsequent ischemia, neovascularization, and atrophy. Despite the treatment advances, there remains no curative therapy, and no treatment targeted at regenerating native-like tissue for patients with late stages of the disease. Here we present advances in tissue engineering, focusing on bioprinting methods of generating tissue allowing for safe and reliable production of oBRB as well as tissue reprogramming with induced pluripotent stem cells for transplantation. We compare these approaches to organ-on-a-chip models for studying the dynamic nature of physiologic conditions. Highlighted within this review are studies that employ good manufacturing practices and use clinical grade methods that minimize potential risk to patients. Lastly, we illustrate recent clinical applications demonstrating both safety and efficacy for direct patient use. These advances provide an avenue for drug discovery and ultimately transplantation.

Incisional choroidal surgery

The choroid is a thin layer of highly vascular uveal tissue enclosed externally by sclera and internally by neurosensory retinal tissue. The choroid is a "middle layer" ocular tissue with anatomically challenging surgical access. The primary functional role of the choroid is to provide rapid, oxygenated, and nutrient-rich blood flow to both the highly metabolic retinal pigment epithelium and outer retina (i.e. photoreceptors) while simultaneously removing waste products. Historically, incisional choroidal surgery (ICS) has involved tumor biopsy or excision, removal of choroidal neovascular complex or autologous choroidal translocations; however, ICS also holds unique potential for novel and innovative approaches to address macular pathology. Using large-animal surgical studies, researchers have explored ICS with the objective of finding safer and more effective techniques to reduce surgical risks such as bleeding, tissue contraction, and scar tissue formation. We explore the relevant anatomy and embryology, existing surgical techniques, discuss the implications for retinal drug delivery, define ICS guiding principles, and offer a rationale for implementation of ICS into a vitreoretinal surgical practice. We also identify other future challenges and anticipate future innovations that will advance ICS.

Toward an internationally accepted standard for reading charts

Patients who suffer from sight-threatening eye diseases share a desire to regain a comfortable reading ability. In light of the modern advances achieved in ophthalmic diagnosis and therapy, and because a significant lack of comparability between reading charts still exists, there is an increasing need for a worldwide standard in the form of a norm for diagnostic reading charts. Already, applied advancements such as digital print, which allow a calibration of the print sizes of reading charts in correctly progressing geometric proportions by using the actual height of a lower case "x" in millimeters (x-height), and psychophysically standardizing reading charts and their test items by applying modern statistical methods have significantly contributed to establishing a norm for reading charts. In 2020, a proposal of the British delegation was accepted by the International Organization for Standardization (ISO) group "Visual Optics and Optical Instruments," and a working group was established. Bearing in mind the efforts of the ISO with regard to an international norm, this review article is intended to (a) give an overview of the historical background and related normative approaches for diagnostic reading tests used in ophthalmology and optometry, (b) explain psychophysical and technical concerns, and (c) discuss the possibilities and limits of concepts that seem relevant to developing a modern standard for reading charts.

Long-term Follow-up of a Phase 1/2a Clinical Trial of a Stem Cell-Derived Bioengineered Retinal Pigment Epithelium Implant for Geographic Atrophy

PURPOSE

To report long-term results from a phase 1/2a clinical trial assessment of a scaffold-based human embryonic stem cell-derived retinal pigmented epithelium (RPE) implant in patients with advanced geographic atrophy (GA).

DESIGN

A single-arm, open-label phase 1/2a clinical trial approved by the United States Food and Drug Administration.

PARTICIPANTS

Patients were 69-85 years of age at the time of enrollment and were legally blind in the treated eye (best-corrected visual acuity [BCVA], ≤ 20/200) as a result of GA involving the fovea.

METHODS

The clinical trial enrolled 16 patients, 15 of whom underwent implantation successfully. The implant was administered to the worse-seeing eye with the use of a custom subretinal insertion device. The companion nonimplanted eye served as the control. The primary endpoint was at 1 year; thereafter, patients were followed up at least yearly.

MAIN OUTCOME MEASURES

Safety was the primary endpoint of the study. The occurrence and frequency of adverse events (AEs) were determined by scheduled eye examinations, including measurement of BCVA and intraocular pressure and multimodal imaging. Serum antibody titers were collected to monitor systemic humoral immune responses to the implanted cells.

RESULTS

At a median follow-up of 3 years, fundus photography revealed no migration of the implant. No unanticipated, severe, implant-related AEs occurred, and the most common anticipated severe AE (severe retinal hemorrhage) was eliminated in the second cohort (9 patients) through improved intraoperative hemostasis. Nonsevere, transient retinal hemorrhages were noted either during or after surgery in all patients as anticipated for a subretinal surgical procedure. Throughout the median 3-year follow-up, results show that implanted eyes were more likely to improve by > 5 letters of BCVA and were less likely to worsen by > 5 letters compared with nonimplanted eyes.

CONCLUSIONS

This report details the long-term follow-up of patients with GA to receive a scaffold-based stem cell-derived bioengineered RPE implant. Results show that the implant, at a median 3-year follow-up, is safe and well tolerated in patients with advanced dry age-related macular degeneration. The safety profile, along with the early indication of efficacy, warrants further clinical evaluation of this novel approach for the treatment of GA.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Progress in Stem Cells-Based Replacement Therapy for Retinal Pigment Epithelium: In Vitro Differentiation to In Vivo Delivery

Retinal pigment epithelium (RPE) is a critical cell monolayer forming the blood-retina-barrier (BRB) and a permeable bridge between the choriocapillaris and the retina. RPE is also crucial in maintaining photoreceptor function and for completing the visual cycle. Loss of the RPE is associated with the development of degenerative diseases like age-related macular degeneration (AMD). To treat diseases like AMD, pluripotent stem cell-derived RPE (pRPE) has been recently explored extensively as a regenerative module. pRPE like other ectodermal tissues requires specific lineage differentiation and long-term in vitro culturing for maturation. Therefore, understanding the differentiation process of RPE could be useful for stem cell-based RPE derivation. Developing pRPE-based transplants and delivering them into the subretinal space is another aspect that has garnered interest in the last decade. In this review, we discuss the basic strategies currently employed for stem cell-based RPE derivation, their delivery, and recent clinical studies related to pRPE transplantation in patients. We have also discussed a few limitations with in vitro RPE culture and potential solutions to overcome such problems which can be helpful in developing functional RPE tissue.

Stem cell-derived retinal pigment epithelium transplantation in age-related macular degeneration: recent advances and challenges

PURPOSE OF REVIEW

Age-related macular degeneration (AMD) is one of the leading causes of irreversible vision loss in the world with more than 80% of the prevalence accounted for by the nonneovascular (NNAMD) or 'dry' form of the disease. NNAMD does not have any definitive treatment once vision loss has ensued and presents a major unmet medical need. This review will highlight stem cell-based therapies that are a promising form of treatment for advanced NNAMD.

RECENT FINDINGS

In the past decade, clinical trials utilizing both induced pluripotent stem cell-derived RPE and human embryonic stem cell-derived RPE have been aggressively pursued as potential treatments of RPE loss and prevention of overlying neurosensory atrophy. While promising preliminary results demonstrating safety and potential efficacy have been published, new challenges have also been identified. These include selecting the most appropriate cell-based therapy, identifying and managing potential immune response as well as characterizing anatomic and functional efficacy. In this review, we will discuss some of these challenges in light of the available data from several early phase clinical trials and discuss the strategies that are being considered to further advance the field.

SUMMARY

Cell-based therapies demonstrate promising potential to treat advanced stages of NNAMD. Several early phase clinical trials using both induced pluripotent stem cells (iPSC) and human embryonic stem cell derived (hESC) have demonstrated safety and preliminary signs of efficacy and highlighted remaining challenges which appear surmountable. These challenges include development of selection criteria for use of cell suspensions versus RPE sheets, especially in light of immunological properties of RPE that are intrinsic to the status of RPE differentiation in each of these cell formulations.

Subretinal Implantation of Human Primary RPE Cells Cultured on Nanofibrous Membranes in Minipigs

Purpose: The development of primary human retinal pigmented epithelium (hRPE) for clinical transplantation purposes on biodegradable scaffolds is indispensable. We hereby report the results of the subretinal implantation of hRPE cells on nanofibrous membranes in minipigs. Methods: The hRPEs were collected from human cadaver donor eyes and cultivated on ultrathin nanofibrous carriers prepared via the electrospinning of poly(L-lactide-co-DL-lactide) (PDLLA). “Libechov” minipigs (12–36 months old) were used in the study, supported by preoperative tacrolimus immunosuppressive therapy. The subretinal implantation of the hRPE-nanofibrous carrier was conducted using general anesthesia via a custom-made injector during standard three-port 23-gauge vitrectomy, followed by silicone oil endotamponade. The observational period lasted 1, 2, 6 and 8 weeks, and included in vivo optical coherence tomography (OCT) of the retina, as well as post mortem immunohistochemistry using the following antibodies: HNAA and STEM121 (human cell markers); Bestrophin and CRALBP (hRPE cell markers); peanut agglutining (PNA) (cone photoreceptor marker); PKCα (rod bipolar marker); Vimentin, GFAP (macroglial markers); and Iba1 (microglial marker). Results: The hRPEs assumed cobblestone morphology, persistent pigmentation and measurable trans-epithelial electrical resistance on the nanofibrous PDLLA carrier. The surgical delivery of the implants in the subretinal space of the immunosuppressed minipigs was successfully achieved and monitored by fundus imaging and OCT. The implanted hRPEs were positive for HNAA and STEM121 and were located between the minipig’s neuroretina and RPE layers at week 2 post-implantation, which was gradually attenuated until week 8. The neuroretina over the implants showed rosette or hypertrophic reaction at week 6. The implanted cells expressed the typical RPE marker bestrophin throughout the whole observation period, and a gradual diminishing of the CRALBP expression in the area of implantation at week 8 post-implantation was observed. The transplanted hRPEs appeared not to form a confluent layer and were less capable of keeping the inner and outer retinal segments intact. The cone photoreceptors adjacent to the implant scaffold were unchanged initially, but underwent a gradual change in structure after hRPE implantation; the retina above and below the implant appeared relatively healthy. The glial reaction of the transplanted and host retina showed Vimentin and GFAP positivity from week 1 onward. Microglial activation appeared in the retinal area of the transplant early after the surgery, which seemed to move into the transplant area over time. Conclusions: The differentiated hRPEs can serve as an alternative cell source for RPE replacement in animal studies. These cells can be cultivated on nanofibrous PDLLA and implanted subretinally into minipigs using standard 23-gauge vitrectomy and implantation injector. The hRPE-laden scaffolds demonstrated relatively good incorporation into the host retina over an eight-week observation period, with some indication of a gliotic scar formation, and a likely neuroinflammatory response in the transplanted area despite the use of immunosuppression.

Pluripotent stem cell therapy for retinal diseases

Pluripotent stem cells (PSCs), which include human embryonic stem cells (hESCs) and induced pluripotent stem cell (iPSC), have been used to study development of disease processes, and as potential therapies in multiple organ systems. In recent years, there has been increasing interest in the use of PSC-based transplantation to treat disorders of the retina in which retinal cells have been functionally damaged or lost through degeneration. The retina, which consists of neuronal tissue, provides an excellent system to test the therapeutic utility of PSC-based transplantation due to its accessibility and the availability of high-resolution imaging technology to evaluate effects. Preclinical trials in animal models of retinal diseases have shown improvement in visual outcomes following subretinal transplantation of PSC-derived photoreceptors or retinal pigment epithelium (RPE) cells. This review focuses on preclinical studies and clinical trials exploring the use of PSCs for retinal diseases. To date, several phase I/II clinical trials in patients with age-related macular degeneration (AMD) and Stargardt disease (STGD1) have demonstrated the safety and feasibility of PSC-derived RPE transplantation. Additional phase I/II clinical trials using PSC-derived RPE or photoreceptor cells for the treatment of AMD, STGD1, and also retinitis pigmentosa (RP) are currently in the pipeline. As this field continues to evolve, additional technologies may enhance PSC-derived cell transplantation through gene-editing of autologous cells, transplantation of more complex cellular structures such as organoids, and monitoring of transplanted cells through novel imaging technologies.

One-Year Follow-Up in a Phase 1/2a Clinical Trial of an Allogeneic RPE Cell Bioengineered Implant for Advanced Dry Age-Related Macular Degeneration

Purpose

To report 1-year follow-up of a phase 1/2a clinical trial testing a composite subretinal implant having polarized human embryonic stem cell (hESC)-derived retinal pigment epithelium (RPE) cells on an ultrathin parylene substrate in subjects with advanced non-neovascular age-related macular degeneration (NNAMD)

Methods

The phase 1/2a clinical trial included 16 subjects in two cohorts. The main endpoint was safety assessed at 365 days using ophthalmic and systemic exams. Pseudophakic subjects with geographic atrophy (GA) and severe vision loss were eligible. Low-dose tacrolimus immunosuppression was utilized for 68 days in the peri-implantation period. The implant was delivered to the worst seeing eye with a custom subretinal insertion device in an outpatient setting. A data safety monitoring committee reviewed all results.

Results

The treated eyes of all subjects were legally blind with a baseline best-corrected visual acuity (BCVA) of ≤ 20/200. There were no unexpected serious adverse events. Four subjects in cohort 1 had serious ocular adverse events, including retinal hemorrhage, edema, focal retinal detachment, or RPE detachment, which was mitigated in cohort 2 using improved hemostasis during surgery. Although this study was not powered to assess efficacy, treated eyes from four subjects showed an increased BCVA of >5 letters (6–13 letters). A larger proportion of treated eyes experienced a >5-letter gain when compared with the untreated eye (27% vs. 7%; P = not significant) and a larger proportion of nonimplanted eyes demonstrated a >5-letter loss (47% vs. 33%; P = not significant).

Conclusions

Outpatient delivery of the implant can be performed routinely. At 1 year, the implant is safe and well tolerated in subjects with advanced dry AMD.

Translational Relevance

This work describes the first clinical trial, to our knowledge, of a novel implant for advanced dry AMD.

Choriocapillaris: Fundamentals and advancements

The choriocapillaris is the innermost structure of the choroid that directly nourishes the retinal pigment epithelium and photoreceptors. This article provides an overview of its hemovasculogenesis development to achieve its final architecture as a lobular vasculature, and also summarizes the current histological and molecular knowledge about choriocapillaris and its dysfunction. After describing the existing state-of-the-art tools to image the choriocapillaris, we report the findings in the choriocapillaris encountered in the most frequent retinochoroidal diseases including vascular diseases, inflammatory diseases, myopia, pachychoroid disease spectrum disorders, and glaucoma. The final section focuses on the development of imaging technology to optimize visualization of the choriocapillaris as well as current treatments of retinochoroidal disorders that specifically target the choriocapillaris. We conclude the article with pertinent unanswered questions and future directions in research for the choriocapillaris.

Retinal Pigment Epithelium Replacement Therapy for Age-Related Macular Degeneration: Are We There Yet?

Pluripotent stem cells (PSCs) are a potential replacement tissue source for degenerative diseases. Age-related macular degeneration (AMD) is a blinding disease triggered by degeneration of the retinal pigment epithelium (RPE), a monolayer tissue that functionally supports retinal photoreceptors. Recently published clinical and preclinical studies have tested PSC-derived RPE as a potential treatment for AMD. Multiple approaches have been used to manufacture RPE cells, to validate them functionally, to confirm their safety profile, and to deliver them to patients either as suspension or as a monolayer patch. Since most of these studies are at an early regulatory approval stage, the primary outcome has been to determine the safety of RPE transplants in patients. However, preliminary signs of efficacy were observed in a few patients. Here, we review the current progress in the PSC-derived RPE transplantation field and provide a comparative assessment of various approaches under development as potential therapeutics for AMD.

Multimodal Evaluation of Visual Function in Geographic Atrophy versus Normal Eyes

Purpose

To comprehensively evaluate visual function in eyes with geographic atrophy (GA) as compared to normal eyes.

Patients and Methods

Sixty-three eyes from 63 patients ≥50 years old were recruited for this observational study; 31 were identified as normal macular health eyes and 32 with GA. Visual function was tested with best corrected visual acuity (BCVA), low luminance visual acuity (LLVA), low luminance deficit (LLD), reading speed, macular integrity microperimetry, fixation stability, and contrast sensitivity function (CSF). Anatomic function was evaluated with spectral-domain optical coherence tomography (SD-OCT) and fundus autofluorescence (FAF). Quality of life and vision were assessed with the National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25).

Results

Visual function and quality of life are reduced in patients with GA. Moderate and strong correlations in the GA group were found between maximum reading speed (r = 0.787) (p˂0.01), CS spatial frequency 3 cpd (r = 0.441) (p˂0.05), CS spatial frequency 6 cpd (r = 0.524) (p˂0.01), fixation P1 (r = 0.379) (p˂0.05), macular sensitivity (r = 0.484) (p˂0.05) and atrophic area (r = -0.689) (p˂0.01), and the VFQ-25 composite score.

Conclusion

The decreased visual function is reflected in a poor quality of life in patients with GA. Reading speed, contrast sensitivity, fixation, and macular sensitivity are strongly associated with vision-related quality of life. The results suggest the importance of the reading letter size in patients with GA. Microperimetry and reading speed are useful tools to better assess visual impairment in patients with GA.

Surgical Method for Implantation of a Biosynthetic Retinal Pigment Epithelium Monolayer for Geographic Atrophy: Experience from a Phase 1/2a Study

PURPOSE

To report the intraoperative methods and anatomic results for subretinal implantation of an investigational human embryonic stem cell-derived retinal pigment epithelium (RPE) monolayer seeded on a synthetic substrate (California Project to Cure Blindness Retinal Pigment Epithelium 1 [CPCB-RPE1]) in geographic atrophy (GA).

DESIGN

Single-arm, open label, prospective, nonrandomized, Phase 1/2a study.

PARTICIPANTS

Advanced non-neovascular age-related macular degeneration (NNAMD).

METHODS

The worse-seeing eye (≤20/200) of each subject underwent subretinal implantation of a single 3.5×6.25 mm CPCB-RPE1 implant with a preplanned primary end point of safety and efficacy at 365 days. Commercially available 23-gauge vitrectomy equipment, custom surgical forceps, and operating microscope with or without intraoperative OCT (iOCT) were used. Exact Wilcoxon rank-sum tests and Spearman rank correlation coefficients were used to assess the association of the percentage of the GA area covered by the implant with patient and surgery characteristics. The partial Spearman correlation coefficient was calculated for the correlation between duration of surgery and baseline GA size after adjustment for surgeon experience.

MAIN OUTCOME MEASURES

Intraoperative exploratory measures are reported, including area of GA covered by implant, subretinal position of implant, duration of surgery, and incidence of adverse events. Operative recordings and reports were used to determine exploratory outcome measures.

RESULTS

Sixteen subjects were enrolled with a median age of 78 years (range, 69-85 years). Median duration of the surgery for all subjects was 160 minutes (range, 121-466 minutes). Intraoperative OCT was used to guide subretinal placement in 9 cases. Intraoperative OCT was potentially useful in identifying pathology not evident with standard intraoperative visualization. Median GA area at baseline was 13.8 mm² (range, 6.0-46.4 mm²), and median GA area left uncovered by the implant was 1.7 mm² (range, 0-20.4 mm²). On average, 86.9% of the baseline GA area was covered by the implant. In 5 subjects, >90% of the GA area was covered. Baseline GA size was inversely correlated with percentage of GA area covered by the implant (r_s=-0.72; P = 0.002). No unanticipated serious adverse events related to the implant or surgery were reported.

CONCLUSIONS

Surgical implantation of CPCB-RPE1 targeted to the area of GA in subjects with advanced NNAMD is feasible in an outpatient setting. Intraoperative OCT is not necessary but potentially useful in identifying subretinal pathology and confirming implant location.

Clinical-grade stem cell-derived retinal pigment epithelium patch rescues retinal degeneration in rodents and pigs

Considerable progress has been made in testing stem cell-derived retinal pigment epithelium (RPE) as a potential therapy for age-related macular degeneration (AMD). However, the recent reports of oncogenic mutations in induced pluripotent stem cells (iPSCs) underlie the need for robust manufacturing and functional validation of clinical-grade iPSC-derived RPE before transplantation. Here, we developed oncogenic mutation-free clinical-grade iPSCs from three AMD patients and differentiated them into clinical-grade iPSC-RPE patches on biodegradable scaffolds. Functional validation of clinical-grade iPSC-RPE patches revealed specific features that distinguished transplantable from nontransplantable patches. Compared to RPE cells in suspension, our biodegradable scaffold approach improved integration and functionality of RPE patches in rats and in a porcine laser-induced RPE injury model that mimics AMD-like eye conditions. Our results suggest that the in vitro and in vivo preclinical functional validation of iPSC-RPE patches developed here might ultimately be useful for evaluation and optimization of autologous iPSC-based therapies.

COMBINED AUTOLOGOUS TRANSPLANTATION OF NEUROSENSORY RETINA, RETINAL PIGMENT EPITHELIUM, AND CHOROID FREE GRAFTS

PURPOSE

To evaluate the feasibility and initial functional and anatomical outcomes of transplanting a full-thickness free graft of choroid and retinal pigment epithelium (RPE), along with neurosensory retina in advanced fibrosis and atrophy associated with end-stage exudative age-related macular degeneration with and without a concurrent refractory macular hole.

METHODS

During vitrectomy, an RPE-choroidal and neurosensory retinal free graft was harvested in nine eyes of nine patients. The RPE-choroidal and neurosensory retinal free graft was either placed subretinally (n = 5), intraretinally to cover the foveal area inside an iatrogenically induced macular hole over the RPE-choroidal graft (n = 3) or preretinally (n = 1) without a retinotomy wherein both free grafts were placed over the concurrent macular hole. Silicone oil endotamponade was used in all cases.

RESULTS

Mean follow-up was 7 ± 5.5 months (range 3-19). The mean preoperative visual acuity was ∼count fingers (logarithm of the minimum angle of resolution = 2.11, range 2-3), which improved to ∼20/800 (logarithm of the minimum angle of resolution 1.62 ± 0.48, range 0.7-2, P = 0.04). Vision was stable in 5 eyes (55.6%) and improved in 4 eyes (44.4%). Reading ability improved in 5 eyes (55.6%). Postoperative complications were graft atrophy (n = 1), epiretinal membrane (n = 1), and dislocation of neurosensory retina-choroid-RPE free graft (n = 1).

CONCLUSION

Combined autologous RPE-choroid and neurosensory retinal free graft is a potential surgical alternative in eyes with end-stage exudative age-related macular degeneration, including concurrent refractory macular hole.

In situ regeneration of retinal pigment epithelium by gene transfer of E2F2: a potential strategy for treatment of macular degenerations

The retinal pigment epithelium (RPE) interacts closely with photoreceptors to maintain visual function. In degenerative diseases such as Stargardt disease and age-related macular degeneration, the leading cause of blindness in the developed world, RPE cell loss is followed by photoreceptor cell death. RPE cells can proliferate under certain conditions, suggesting an intrinsic regenerative potential, but so far this has not been utilised therapeutically. Here, we used E2F2 to induce RPE cell replication and thereby regeneration. In both young and old (2 and 18 month) wildtype mice, subretinal injection of non-integrating lentiviral vector expressing E2F2 resulted in 47% of examined RPE cells becoming BrdU positive. E2F2 induced an increase in RPE cell density of 17% compared with control vector-treated and 14% compared with untreated eyes. We also tested this approach in an inducible transgenic mouse model of RPE loss, generated through activation of diphtheria toxin-A gene. E2F2 expression resulted in a 10-fold increase in BrdU uptake and a 34% increase in central RPE cell density. Although in mice this localised rescue is insufficiently large to be demonstrable by electroretinography, a measure of massed retinal function, these results provide proof-of-concept for a strategy to induce in situ regeneration of RPE for the treatment of RPE degeneration.

A comparison of autologous transplantation of retinal pigment epithelium (RPE) monolayer sheet graft with RPE-Bruch's membrane complex graft in neovascular age-related macular degeneration

PURPOSE

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.

METHODS

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.

RESULTS

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 ± 9.31 months. 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 ± 6.25 months. 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 from 16.61 ± 27.98 to 29.16 ± 23.80 (p = 0.02) in a mean period of 21.72 ± 11.09 months. 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.

CONCLUSIONS

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.

Induced pluripotent stem cell-based therapy for age-related macular degeneration

INTRODUCTION

In age-related macular degeneration (AMD), stem cells could possibly replace or regenerate disrupted pathologic retinal pigment epithelium (RPE), and produce supportive growth factors and cytokines such as brain-derived neurotrophic factor.  Induced pluripotent stem cells (iPSCs)-derived RPE was first subretinally transplanted in a neovascular AMD patient in 2014. Areas covered: Induced PSCs are derived from the introduction of transcription factors to adult cells under specific cell culture conditions, followed by differentiation into RPE cells. Induced PSC-derived RPE cells exhibit ion transport, membrane potential, polarized VEGF secretion and gene expression that is similar to native RPE. Despite having similar in vitro function, morphology, immunostaining and microscopic analysis, it remains to be seen if iPSC-derived RPE can replicate the myriad of in vivo functions, including immunomodulatory effects, of native RPE cells.  Historically, adjuvant RPE transplantation during CNV resections were technically difficult and complicated by immune rejection. Autologous iPSCs are hypothesized to reduce the risk of immune rejection, but their production is time-consuming and expensive.  Alternatively, allogenic transplantation using human leukocyte antigen (HLA)-matched iPSCs, similar to HLA-matched organ transplantation, is currently being investigated. Expert opinion: Challenges to successful transplantation with iPSCs include surgical technique, a pathologic subretinal microenvironment, possible immune rejection, and complications of immunosuppression.

Reading charts in ophthalmology

A new generation of logarithmic reading charts has sparked interest in standardized reading performance analyses. Such reading charts have been developed according to the standards of the International Council of Ophthalmology. The print size progression in these calibrated charts is in accordance with the mathematical background of EN ISO 8596. These reading charts are: the Bailey–Lovie Word Reading Chart, the Colenbrander English Continuous Text Near Vision Cards, the Oculus Reading Probe II, the MNREAD Charts, the SKread Charts, and the RADNER Reading Charts. The test items used for these reading charts differ among the charts and are standardized to various extents. The Bailey–Lovie Charts, MNREAD Charts, SKread Charts, and RADNER Charts are also meant to measure reading speed and allow determination of further reading parameters such as reading acuity, reading speed based on reading acuity, critical print size, reading score, and logMAR/logRAD ratio. Such calibrated reading charts have already provided valuable insights into the reading performance of patients in many research studies. They are available in many languages and thus facilitate international communication about near visual performance. In the present review article, the backgrounds of these modern reading charts are presented, and their different levels of test-item standardization are discussed. Clinical research studies are mentioned, and a discussion about the immoderately high number of reading acuity notations is included. Using the logReading Acuity Determination ([logRAD] = reading acuity equivalent of logMAR) measure for research purposes would give reading acuity its own identity as a standardized reading parameter in ophthalmology.

Integrating a novel concept of sentence optotypes into the RADNER Reading Charts

PURPOSE

To add a new set of 24 sentence optotypes to the German version of the RADNER reading charts and to investigate whether sentences constructed based upon an optimised concept of sentence optotypes can be used together with the original 38 sentences.

METHODS

Twenty-eight optimised sentence optotypes were constructed based upon the concept of sentence optotypes as established for the RADNER Reading Charts, with words having the same number of characters and syllables being placed in the same positions. The best comparable sentences were statistically selected in 30 volunteers. Reading speed and the number of errors were determined. Validity was analysed in comparison to a 111-word long standardised paragraph and 7 of the 38 original sentence optotypes.

RESULTS

The mean reading speed obtained with the 28 sentences was 192.30±26.69 words per minute (wpm), as compared with 192.47±25.32 wpm for the 7 original sentence optotypes and 165.28±20.82 wpm for the long paragraph; 24 of the 28 optimised sentences met our selection criteria for reading speed/time (mean reading speed: 192.41±26.58). The mean number of reading errors was 0.10±0.30. The correlation between the 24 optimised sentence optotypes and the long paragraph was r=0.90. Reliability analyses yielded an overall Cronbach's α coefficient of 0.992.

CONCLUSION

The 24 new sentence optotypes can be integrated into the existing set of 38 original sentences. Since all the statistical results obtained were similar to those of the original sentences, the best possible reliability had apparently already been achieved with the original sentence optotypes.

Near vision examination in presbyopia patients: Do we need good homologated near vision charts?

Presbyopia correction is mainly concerned with the goal of regaining an uncorrected reading performance. Since historic reading charts do not provide a unique standard that is applicable for the analysis of clinical and scientific reading performance, new standardized reading charts have been developed, in order to provide reading performance analyses analogous to modern single-optotype distance acuity measurements: the Bailey-Lovie Word Reading Chart, the Colenbrander English Continuous Text Near Vision Cards, the MNREAD Charts, and the RADNER Reading Charts. The last three are also meant to measure reading speed, thus allowing detailed analysis of the reading capabilities of the patient’s functional vision. Furthermore, these reading charts can be declared homologated, based on the standards that were published for reading charts by the Visual Function Committee of the International Council of Ophthalmology (ICO) in 1988. Many research studies have shown that by analyzing the reading performance with homologated reading charts, valuable insight into the reading performance of patients suffering from various diseases can be obtained. These reading charts have also been successfully used in presbyopia research. It therefore seems evident that homologated, standardized reading charts facilitate not only research concerning functional vision in many fields of ophthalmology but also international communication about near visual performance. Homologated reading charts are available in almost all languages and have become a valuable tool in analyzing reading performance. We argue in this review that homologated reading charts are clearly a necessity for presbyopia research.

Looking into the future: Using induced pluripotent stem cells to build two and three dimensional ocular tissue for cell therapy and disease modeling

Retinal degenerative diseases are the leading cause of irreversible vision loss in developed countries. In many cases the diseases originate in the homeostatic unit in the back of the eye that contains the retina, retinal pigment epithelium (RPE) and the choriocapillaris. RPE is a central and a critical component of this homeostatic unit, maintaining photoreceptor function and survival on the apical side and choriocapillaris health on the basal side. In diseases like age-related macular degeneration (AMD), it is thought that RPE dysfunctions cause disease-initiating events and as the RPE degenerates photoreceptors begin to die and patients start loosing vision. Patient-specific induced pluripotent stem (iPS) cell-derived RPE provides direct access to a patient's genetics and allow the possibility of identifying the initiating events of RPE-associated degenerative diseases. Furthermore, iPS cell-derived RPE cells are being tested as a potential cell replacement in disease stages with RPE atrophy. In this article we summarize the recent progress in the field of iPS cell-derived RPE "disease modeling" and cell therapies and also discuss the possibilities of developing a model of the entire homeostatic unit to aid in studying disease processes in the future. This article is part of a Special Issue entitled SI: PSC and the brain.

Induced Pluripotent Stem Cell Therapies for Degenerative Disease of the Outer Retina: Disease Modeling and Cell Replacement

Stem cell therapies are being explored as potential treatments for retinal disease. How to replace neurons in a degenerated retina presents a continued challenge for the regenerative medicine field that, if achieved, could restore sight. The major issues are: (i) the source and availability of donor cells for transplantation; (ii) the differentiation of stem cells into the required retinal cells; and (iii) the delivery, integration, functionality, and survival of new cells in the host neural network. This review considers the use of induced pluripotent stem cells (iPSC), currently under intense investigation, as a platform for cell transplantation therapy. Moreover, patient-specific iPSC are being developed for autologous cell transplantation and as a tool for modeling specific retinal diseases, testing gene therapies, and drug screening.

Regenerating Retinal Pigment Epithelial Cells to Cure Blindness: A Road Towards Personalized Artificial Tissue

Retinal pigment epithelium (RPE) is a polarized monolayer tissue that functions to support the health and integrity of retinal photoreceptors (PRs). RPE atrophy has been linked to pathogenesis of age-related macular degeneration (AMD), a leading cause of blindness in elderly in the USA. RPE atrophy in AMD leads to the PR cell death and vision loss. It is thought that replacing diseased RPE with healthy RPE tissue can prevent PR cell death. Retinal surgical innovations have provided proof-of-principle data that autologous RPE tissue can replace diseased macular RPE and provide visual rescue in AMD patients. Current efforts are focused on developing an in vitro tissue using natural and synthetic scaffolds to generate a polarized functional RPE monolayer. In the future, these tissue-engineering approaches combined with pluripotent stem cell technology will lead to the development of personalized and "off-the-shelf" cell therapies for AMD patients. This review summarizes the historical development and ongoing efforts in surgical and in vitro tissue engineering techniques to develop a three-dimensional therapeutic native RPE tissue substitute.

Treatment of macular degeneration using embryonic stem cell-derived retinal pigment epithelium: preliminary results in Asian patients

Embryonic 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.

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Human embryonic-stem-cell-derived retinal pigment epithelial cells were transplanted

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Patches of increasing pigmentations were observed after transplantation of the cells

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Visual function stabilized or improved in all of these macular degeneration patients

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There were no serious adverse events associated with the cells up to 1 year

English sentence optotypes for measuring reading acuity and speed--the English version of the Radner Reading Charts

PURPOSE

To develop 28 short sentence optotypes for the English version of the Radner Reading Charts that are as comparable as possible in number and length of words, as well as in difficulty and syntactical construction.

METHODS

Thirty-four English sentences were constructed following the method used for other Radner Reading Charts to obtain "sentence optotypes" with comparable structure and the same lexical and grammatical difficulty. Best comparable sentences were statistically selected and standardized in 50 volunteers. Reading speed and the number of errors were determined. Validity was analyzed with a 124-word long 4th-grade paragraph of the Florida Comprehensive Assessment Test®. Computerized measurements of reading parameters were performed with the RADNER Reading Device (RAD-RD©; in conjunction with a PC and microphone).

RESULTS

The mean reading speed obtained with the 28 selected short sentences was 201.53 ± 35.88 words per minute (wpm), as compared to 215.01 ± 30.37 wpm for the long paragraph. The mean reading times were 4.30 ± 0.79 s and 35.26 ± 4.85 s, respectively. The mean number of reading errors was 0.11 ± 0.34. The correlation between the short sentences and the long paragraph was high (r = 0.76; p < 0.05; n = 50). Reliability analyses yielded an overall Cronbach's alpha coefficient of 0.9743.

CONCLUSION

The present study indicates that the 28 selected English sentence optotypes are comparable in terms of both lexical difficulty as well as in reading length, and it demonstrates the validity and reliability of such sentences as test items for determining reading parameters such as reading acuity and speed.

Generation of retinal pigment epithelial cells from small molecules and OCT4 reprogrammed human induced pluripotent stem cells

Autologous retinal pigment epithelium (RPE) grafts derived from induced pluripotent stem cells (iPSCs) may be used to cure blinding diseases in which RPE dysfunction results in photoreceptor degeneration. Four-, two-, and one-factor-derived iPSCs (4F-, 2F-, and 1F-iPSCs, respectively) were differentiated into fully functional cuboidal pigmented cells in polarized monolayers that express RPE-specific markers. 1F-iPSCs-RPE (1F-iPS-RPE) strongly resembles primary human fetal RPE (hfRPE) based on proteomic and untargeted metabolomic analyses, and using novel in vivo imaging technology coupled with electroretinography, we demonstrated that 1F-iPS-RPE mediate anatomical and functional rescue of photoreceptors after transplantation in an animal model of RPE-mediated retinal degeneration. 1F-iPS0RPE cells were injected subretinally as a suspension and formed a monolayer dispersed between host RPE cells. Furthermore, 1F-iPS-RPE do not simply provide trophic support to rescue photoreceptors as previously speculated but actually phagocytose photoreceptor outer segments in vivo and maintain visual cycling. Thus, 1f-iPS-RPE grafts may be superior to conventional iPS-RPE for clinical use because 1F-IPS-RPE closely resemble hfRPE, mediate anatomical and functional photoreceptor rescue in vivo, and are generated using a reduced number of potentially oncogenic reprogramming factors.

Stem cell-based treatment in geographic atrophy: promises and pitfalls

Geographic atrophy is a common and untreatable form of advanced age-related macular degeneration. The degeneration primarily affects the retinal pigment epithelium and photoreceptors of the retina and their restoration by cell transplantation seems attractive. Recently, a patient with geographic atrophy was the first human to receive cells derived from human embryonic stem cells. In this short review, the rationale, potential and obstacles for stem cell-derived therapy in geographic atrophy are discussed.

Utilizing stem cell-derived RPE cells as a therapeutic intervention for age-related macular degeneration

Degeneration or dysfunction of the retinal pigment epithelium (RPE) can induce secondary photoreceptor atrophy and catastrophic vision loss in patients with age-related macular degeneration (AMD). AMD is the leading cause of vision loss in the elderly in industrialized countries and no cure exists for the "dry" or atrophic form to date. However, recent pre-clinical data from several groups suggests that embryonic stem cell-derived RPE cell transplantation may prevent photoreceptor degeneration in animal models of RPE degeneration. Another approach may be to derive RPE cells from autologous induced pluripotent stem cells (iPSCs) reprogrammed from dermal tissue. However, the safety of this approach has been questioned on several levels. In this chapter we will summarize work reported by several groups, including our own, that clearly demonstrate that transplanted RPE cells can provide anatomical and functional photoreceptor rescue in animal models of retinal degeneration. We will also discuss some of the prevailing concerns and challenges associated with this technique.

Characterization of the effects of retinal pigment epithelium-conditioned media on porcine and aged human retina

BACKGROUND

Retinal pigment epithelium (RPE) cells produce neurotrophic factors that rescue photoreceptors from degeneration. Previously, we showed that conditioned medium (CM) from fetal vs adult RPE cells resulted in significantly better porcine retinal preservation, and possessed significantly higher levels of hepatocyte growth factor (HGF) and pigment epithelium-derived factor (PEDF). This study aimed to further describe the effects of human fetal RPE-CM on porcine and aged human retina, and to characterize its effects biochemically.

METHODS

RPE-CM was harvested from passage-2 fetal RPE, 7 days after passage, 24-hours after exposure to basal medium. After culture in RPE-CM, porcine retinal morphology was assessed with confocal microscopy. The effects of RPE-CM on porcine and aged human retina survival were assessed by cytotoxicity and apoptosis biochemical assays. To characterize RPE-CM biochemically, effects of heating, digesting with proteinase-K, dilution, concentration, and fractionation were tested. Recombinant proteins and neutralizing antibodies were used to identify proteins that might contribute to the salutary effects of RPE-CM on porcine retina.

RESULTS

Culturing porcine retina in RPE-CM significantly preserved outer nuclear layer width and the number of nuclei in cross-section, and significantly decreased photoreceptor axon retraction. RPE-CM decreased porcine retinal death by 17-34 % (p<0.05) compared to basal medium. Human retina from age-related macular degeneration (AMD) and non-AMD donors responded similarly after culture in RPE-CM. Heating, proteinase-K digestion, and dilution significantly diminished RPE-CM-mediated preservation of porcine retina, whereas concentrating RPE-CM significantly enhanced its preservation of porcine retina. Molecular cut filtration identified retina-preserving activity in the 3-100 kDa filtrate. PEDF or HGF at 90 % receptor occupancy significantly improved retinal preservation over 48 h of culture compared to basal medium. Neutralizing PEDF in RPE-CM decreased its ability to reduce retinal apoptosis by 23-27 % (p<0.05).

CONCLUSION

RPE-CM reduced biochemically and histologically measured degeneration in porcine retinae. This effect was concentration-dependent, and can be attributed to a protein component(s) in a 3-100 kDa molecular cut fraction. Human retina (including non-AMD and AMD Caucasian and non-AMD African-American) responds to culture in RPE-CM similarly to porcine retina. Receptor occupancy calculations and retinal viability data indicate that PEDF may be one of the components that contribute to retina preservation by RPE-CM.

Histology and immunochemistry evaluation of autologous translocation of retinal pigment epithelium-choroid graft in porcine eyes

PURPOSE

To evaluate structure and cellular functionality of retinal pigment epithelium (RPE)-choroid grafts after autologous translocation in porcine eyes.

METHODS

Retinal pigment epithelium-choroid grafts were obtained from the nasal midperiphery donor site and translocated to the central area in 12 pigs (12 eyes). Grafts were placed under the central retina through a retinotomy. Ophthalmoscopic and pathological evaluations were performed immediately (n = 1) and at 15 (n = 3) and 30 (n = 3) days after surgery. Untranslocated nasal RPE-choroid grafts were obtained at time of surgery and used as controls. Specimens were evaluated by standard histology and by immunochemical studies of RPE65, CRALBP and GFAP.

RESULTS

Five animals were lost to follow-up owing to surgery or anaesthesia complications. Ophthalmoscopic examination revealed that the grafts remained in place at all time-points studied. Fifteen and thirty days postsurgery, some areas of the transplanted RPE maintained a monolayered structure. Retinal pigment epithelium cells were firmly attached to Bruch's membrane and predominantly preserved polarity and pigment distribution. However, RPE65, CRALBP and GFAP patterns of expression and distribution were diminished and modified during follow-up. Ophthalmoscopic retinal detachment and proliferative vitreoretinopathy (PVR), confirmed by microscopic evaluation, complicated all cases at 30 days of follow-up.

CONCLUSION

Autologous RPE-choroid grafts survived up to 30 days in porcine eyes. Histological and immunochemical evaluation revealed preserved transplanted RPE cells morphology accompanied by alterations in the immunoreactivity expression of functional proteins, and development of significant PVR. The data presented in this manuscript provide insights into the fate, viability and cellular functionality of the transplanted RPE-choroid graft, serving as foundation for further knowledge and improvement of this technique.

Ophthalmic transplantology: posterior segment of the eye--part II

Background

Transplants of the retina are among the new strategies being used in the treatment of genetic and degenerative macular diseases. Moreover, various cell cultures are being tested to treat retinal disorders.

Material/Methods

Literature dated from 2004 to 2011 was comprehensively examined via Medline and PubMed searches for the following terms: auto-, homo-, heterologous transplantation, retina, stem cells, cultivated cells.

Results

Tissue and cell therapy of retinal diseases are reviewed, including full-thickness retina/retinal pigment epithelium (RPE)/choroid graft; full and partial thickness RPE/choroid complex grafts; RPE/Bruch membrane complex graft; and RPE, iris pigment epithelium and stem cell grafts. Recommendations for transplants, as well as the benefits and weaknesses of specific techniques in retina transplants, are discussed.

Conclusions

Auto- and allogenic transplants of a full or partial thickness retina/RPE/Bruch membrane/choroid complex represent an alternative treatment offered to patients with some macular diseases. Stem cell transplantation to reconstruct and regenerate the macula requires further biomolecular and animal research studies.

Autologous translocation of the retinal pigment epithelium and choroid in the treatment of neovascular age-related macular degeneration

PURPOSE

To evaluate clinical results of an autologous translocation of retinal pigment epithelium (RPE) and choroid in the treatment of neovascular age-related macular degeneration (AMD).

METHODS

Twelve eyes which underwent surgery for neovascular AMD were included into the study, in four eyes moderate or massive submacular haemorrhage was present. The surgical procedure included standard pars plana vitrectomy; cataract surgery in phakic patients; peripheral 180°-retinotomy; extraction of the submacular neovascular complex and removal of blood if present; preparation of a full-thickness graft consisting of RPE, Bruch's membrane and choroid; translocation of the graft to the macular area; and silicone oil endotamponade.

RESULTS

Visual acuity (VA) ranged from perception of hand movements (HM) to 20/125 (median, counting fingers (CF)-1/50) before surgery. During follow-up (FU) mean, 11.1 months, VA increased to a maximum median of 1/10 (range, HM-20/40). At the end of FU, VA had dropped to a median of CF-1/40 (range, HM-20/50). Comparing VA preoperatively and at the end of FU, VA had improved in six eyes, was unchanged in three eyes, and had deteriorated in three eyes. One eye had reading ability. Surgery-associated postoperative complications impairing the functional outcome occurred in five eyes, including rhegmatogenous retinal detachment and proliferative vitreoretinopathy. Revision surgery had to be performed in four eyes (30%). Three eyes had to be left with permanent silicone endotamponade. Results tended to be better in the subgroup of eyes with massive submacular haemorrhage preoperatively.

CONCLUSION

Functional results of a translocation of RPE and choroid were heterogeneous and rather disappointing in this study. Results may have been influenced negatively by case selection. We found a relatively high rate of adverse events in the postoperative course. In selected cases, e.g. massive submacular haemorrhage or progressive neovascular AMD unresponsive to other treatment options, autologous translocation of RPE and choroid may still be considered.

[Perfluorocarbon liquids and vitreoretinal surgery in 2011]

Perfluorocarbon liquids (PFCLs) are one of the most innovative recent tools for vitreoretinal surgery. PFCLs are characterized by their number of carbon atoms, which has an impact on the density, viscosity, surface tension, vapor pressure, the boiling point, and the refraction index. PFCLs are routinely used because of their high gravity (double that of water) and their low viscosity. Furthermore, they are immiscible in water, optically clear with refraction indices similar to that of water, allowing visualization of an interface between the PFCL and saline. The use of intravitreally injected liquid PFCLs as adjunctive agents to vitreoretinal surgery plays an important role in facilitating retinal reattachment, especially in cases of giant retinal tear, trauma, and/or proliferative vitreoretinopathy. PFCLs are also used as intraoperative instruments to re-establish intraocular volume, assist in separating membranes adherent to the retina (in proliferative diabetic retinopathy, for example), and manage the dislocated crystalline lens and intraocular lens.

Cell-deposited matrix improves retinal pigment epithelium survival on aged submacular human Bruch's membrane

PURPOSE

To determine whether resurfacing submacular human Bruch's membrane with a cell-deposited extracellular matrix (ECM) improves retinal pigment epithelial (RPE) survival.

METHODS

Bovine corneal endothelial (BCE) cells were seeded onto the inner collagenous layer of submacular Bruch's membrane explants of human donor eyes to allow ECM deposition. Control explants from fellow eyes were cultured in medium only. The deposited ECM was exposed by removing BCE. Fetal RPE cells were then cultured on these explants for 1, 14, or 21 days. The explants were analyzed quantitatively by light microscopy and scanning electron microscopy. Surviving RPE cells from explants cultured for 21 days were harvested to compare bestrophin and RPE65 mRNA expression. Mass spectroscopy was performed on BCE-ECM to examine the protein composition.

RESULTS

The BCE-treated explants showed significantly higher RPE nuclear density than did the control explants at all time points. RPE expressed more differentiated features on BCE-treated explants than on untreated explants, but expressed very little mRNA for bestrophin or RPE65. The untreated young (<50 years) and African American submacular Bruch's membrane explants supported significantly higher RPE nuclear densities (NDs) than did the Caucasian explants. These differences were reduced or nonexistent in the BCE-ECM-treated explants. Proteins identified in the BCE-ECM included ECM proteins, ECM-associated proteins, cell membrane proteins, and intracellular proteins.

CONCLUSIONS

Increased RPE survival can be achieved on aged submacular human Bruch's membrane by resurfacing the latter with a cell-deposited ECM. Caucasian eyes seem to benefit the most, as cell survival is the worst on submacular Bruch's membrane in these eyes.

Stemming vision loss with stem cells

Dramatic advances in the field of stem cell research have raised the possibility of using these cells to treat a variety of diseases. The eye is an excellent target organ for such cell-based therapeutics due to its ready accessibility, the prevalence of vasculo- and neurodegenerative diseases affecting vision, and the availability of animal models to demonstrate proof of concept. In fact, stem cell therapies have already been applied to the treatment of disease affecting the ocular surface, leading to preservation of vision. Diseases in the back of the eye, such as macular degeneration, diabetic retinopathy, and inherited retinal degenerations, present greater challenges, but rapidly emerging stem cell technologies hold the promise of autologous grafts to stabilize vision loss through cellular replacement or paracrine rescue effects.

Transplantation of reprogrammed embryonic stem cells improves visual function in a mouse model for retinitis pigmentosa

BACKGROUND

To study whether C57BL/6J-Tyr/J (C2J) mouse embryonic stem (ES) cells can differentiate into retinal pigment epithelial (RPE) cells in vitro and then restore retinal function in a model for retinitis pigmentosa: Rpe65/Rpe65 C57BL6 mice.

METHODS

Yellow fluorescent protein (YFP)-labeled C2J ES cells were induced to differentiate into RPE-like structures on PA6 feeders. RPE-specific markers are expressed from differentiated cells in vitro. After differentiation, ES cell-derived RPE-like cells were transplanted into the subretinal space of postnatal day 5 Rpe65/Rpe65 mice. Live imaging of YFP-labeled C2J ES cells demonstrated survival of the graft. Electroretinograms (ERGs) were performed on transplanted mice to evaluate the functional outcome of transplantation.

RESULTS

RPE-like cells derived from ES cells sequentially express multiple RPE-specific markers. After transplantation, YFP-labeled cells can be tracked with live imaging for as long as 7 months. Although more than half of the mice were complicated with retinal detachments or tumor development, one fourth of the mice showed increased electroretinogram responses in the transplanted eyes. Rpe65/Rpe65 mice transplanted with RPE-like cells showed significant visual recovery during a 7-month period, whereas those injected with saline, PA6 feeders, or undifferentiated ES cells showed no rescue.

CONCLUSIONS

ES cells can differentiate, morphologically, and functionally, into RPE-like cells. Based on these findings, differentiated ES cells have the potential for the development of new therapeutic approaches for RPE-specific diseases such as certain forms of retinitis pigmentosa and macular degeneration. Nevertheless, stringent control of retinal detachment and teratoma development will be necessary before initiation of treatment trials.

Induced pluripotent stem cell therapies for retinal disease

PURPOSE OF REVIEW

This review will discuss how recent advances with induced pluripotent stem (iPS) cells have brought the science of stem cell biology much closer to clinical application for patients with retinal degeneration.

RECENT FINDINGS

The ability to generate embryonic stem cells by reprogramming DNA taken from adult cells was demonstrated by the cloning of Dolly, the sheep, by somatic cell nuclear transfer, over 10 years ago. Recently, it has been shown that adult cells can be reprogrammed directly, without the need for a surrogate oocyte, through the generation of iPS cells. The method of reprogramming has since been optimized to avoid the use of retroviruses, making the process considerably safer. Last year, human iPS cells were isolated from an 80-year-old patient with neurodegenerative disease and differentiated into neurons in vitro.

SUMMARY

For stem cell therapies, the retina has the optimal combination of ease of surgical access, combined with an ability to observe transplanted cells directly through the clear ocular media. The question now is which retinal diseases are most appropriate targets for clinical trials using iPS cell approaches.

Surgery for CNV and autologous choroidal RPE patch transplantation: exposing the submacular space

BACKGROUND

To evaluate the feasibility of transplanting a full-thickness patch of choroid, choriocapillaries, Bruch's membrane and RPE (RPE-choroid FTAP) from the peripheral to the subfoveal area of the same eye, after performing a 180 degrees peripheral retinotomy and removing subfoveal choroidal neovascularization. Thereafter, to study the surgical complications, anatomical outcome and patch perfusion during follow-up.

METHODS

A retrospective case series of 13 eyes of 13 consecutive patients with a follow-up of 4 to 20 months. All patients suffered from advanced subfoveal choroidal neovascularization and were non-responders to standard care. After performing a complete vitrectomy, a 180 degrees peripheral temporal retinotomy and the removal of subfoveal neovascularization, a FTAP of choroid, choriocapillaris, Bruch's membrane and the RPE were isolated from the mid periphery of the uveal bed, transpositioned under the fovea and covered with the retina. Patients received a complete ophthalmic examination, fluorescein angiography (FA), indocyanin green angiography (ICGA) and optical coherence tomography (OCT) during follow-up.

RESULTS

An FTAP could be harvested in every eye and transplanted under the fovea. No intraoperative complications occurred. The FTAP was recognizable at FA, ICGA and OCT at each time point, up to 20 months postoperatively. Perfusion of the choroidal bed were observed into the FTAP during follow-up, from one week after surgery.

CONCLUSION

The creation of an FTAP through a 180 degrees peripheral retinotomy is feasible and safe. The FTAP is vital and perfused. Further studies are needed to collect more data.

Autologous translocation of choroid and retinal pigment epithelium in geographic atrophy: long-term functional and anatomical outcome

Purpose

To evaluate the long-term outcome of autologous graft of retinal pigment epithelium (RPE) in patients with geographic atrophy.

Methods

Ten patients with progressive geographic atrophy underwent translocation of an autologous graft of RPE, Bruch membrane and choroid. The visual acuity (VA), reading performance, microperimetry, optical coherence tomography (OCT), fundus autofluorescence, fluorescein angiography and indocyanine green angiography were assessed.

Results

No recurrence of RPE atrophy was seen. All but one transplant were revascularised. Vascularisation persisted throughout the 3 years' follow-up. Spectral-domain OCT in some cases showed intact photoreceptors or intact outer nuclear and outer plexiform layer overlying the graft. In three cases, the grafts were positioned eccentrically; these patients did not benefit from surgery. The mean VA decreased from 20/80 (range: 20/800 to 20/40) at baseline to 20/200 (range: perception of hand movements to 20/32) at last follow-up. In two patients, VA were stable from 20/50 to 20/32 and 20/40 at the last follow-up, respectively. Postoperative complications included retinal detachment due to proliferative vitreoretinopathy, macular pucker, iritis, branch retinal vein occlusion and secondary ocular hypertension.

Conclusions

Some patients benefit for at least 3 years from a functioning RPE-choroid graft. Functional outcome in most patients, however, was limited due to complications and unfavourable patient selection.

The treatment of wet age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is a progressive disease affecting the macula, the area of the retina that has the highest visual acuity. It can progress to geographic atrophy or choroidal neovascularization.

METHOD

Selective literature review.

RESULTS

The authors discuss the results of therapeutic trials and the treatment recommendations of the ophthalmological societies. Mechanism-targeted treatments and improved modes of administration offer the potential for improved therapy.

CONCLUSIONS

With the advent of the antivascular endothelial growth factor (anti-VEGF) therapy, the prognosis of choroidal neovascularization has changed dramatically. Visual acuity can actually be improved, but, in most cases, the improvement can only be sustained with repeated intravitreal injections.