Human retinal progenitor cell transplantation preserves vision.

Cell transplantation is a potential therapeutic strategy for retinal degenerative diseases involving the loss of photoreceptors. However, it faces challenges to clinical translation due to safety concerns and a limited supply of cells. Human retinal progenitor cells (hRPCs) from fetal neural retina are expandable in vitro and maintain an undifferentiated state. This study aimed to investigate the therapeutic potential of hRPCs transplanted into a Royal College of Surgeons (RCS) rat model of retinal degeneration. At 12 weeks, optokinetic response showed that hRPC-grafted eyes had significantly superior visual acuity compared with vehicle-treated eyes. Histological evaluation of outer nuclear layer (ONL) characteristics such as ONL thickness, spread distance, and cell count demonstrated a significantly greater preservation of the ONL in hRPC-treated eyes compared with both vehicle-treated and control eyes. The transplanted hRPCs arrested visual decline over time in the RCS rat and rescued retinal morphology, demonstrating their potential as a therapy for retinal diseases. We suggest that the preservation of visual acuity was likely achieved through host photoreceptor rescue. We found that hRPC transplantation into the subretinal space of RCS rats was well tolerated, with no adverse effects such as tumor formation noted at 12 weeks after treatment.

Adapting biodegradable oligo(poly(ethylene glycol) fumarate) hydrogels for pigment epithelial cell encapsulation and lens regeneration.

This study investigated the encapsulation of newt iris pigment epithelial cells (PECs), which have the ability to regenerate a lens by trans-differentiation in vivo, within a biodegradable hydrogel of oligo(poly(ethylene glycol) fumarate) crosslinked with poly(ethylene glycol)-diacrylate. Hydrogel beads of initial diameter of 1 mm were fabricated by a molding technique. The swelling ratio and degradation rate of the hydrogel beads decreased with increasing crosslinking ratios. Confocal microscopy confirmed the cytocompatibility of crosslinking hydrogel formulations as evidenced by the viability of an encapsulated model cell line within a crosslinked hydrogel bead. Hydrogel beads encapsulating iris PECs were also implanted into lentectomized newts in vivo; histological evaluation of explants after 30 days revealed a regenerated lens, thus demonstrating that the presence of degrading hydrogel did not adversely affect lens regeneration. The results of this study suggest the potential of a method for lens regeneration involving oligo(poly(ethylene glycol) fumarate) hydrogels for iris PEC encapsulation and transplantation.

TrkB-T1 receptors on Muller cells play critical role in brain-derived neurotrophic factor-mediated photoreceptor protection against phototoxicity.

PURPOSE: To determine how brain-derived neurotrophic factor (BDNF) protects photoreceptors against phototoxicity. METHODS: Iris pigment epithelial cells (IPE) that were transduced with different concentrations of adeno-associated virus (AAV) mediated BDNF (AAV-BDNF-IPE) were transplanted into the subretinal space of rats. We also injected small interfering RNAs (siRNAs) for TrkB, a BDNF receptor. The rats were exposed to continuous light to induce phototoxicity. We examined the expression of TrkB in the retina by Western blot and immunohistochemistry. RESULTS: Significant photoreceptor protection was detected when more than 1 x 10(7) capsids/ml AAV-BDNF was transplanted. An intravitreal injection of siRNAs showed that the photoreceptor protection by AAV-BDNF-IPE was reduced by injecting the siRNA of TrkB-T1, one of the TrkB isoforms. TrkB-T1 was slightly upregulated by Western blot, and one of the cells that upregulated TrkB-T1 was Muller cells by immunohistochemistry. CONCLUSION: We conclude that Muller cells are one of the cells responsible for the expression of TrkBs, and TrkB-T1 may play a role in the protection of photoreceptors against phototoxicity.

Pathologic findings in retinal pigment epithelial cell implantation for Parkinson disease.

BACKGROUND: Attempts at cell-based dopamine replacement therapy in Parkinson disease (PD) have included surgical implantation of adrenal medullary, fetal mesencephalic, and cultured human mesencephalic tissue grafts. Trials involving putamenal implantation of human retinal pigment epithelial (RPE) cells in PD have also been performed. Neuropathologic findings in humans undergoing RPE cell implantation have not heretofore been reported. We describe the brain autopsy findings from a subject enrolled in a clinical trial of RPE cells in gelatin microcarriers for treatment of PD, and suggest factors which may have impacted cell survival. METHODS: A 68-year-old man underwent bilateral surgical implantation of 325,000 RPE cells in gelatin microcarriers (Spheramine) but died 6 months after surgery. The left cerebral hemisphere was examined. Routine postmortem formalin fixation was performed and standard, as well as immunohistochemical methods used to highlight senile plaque and Lewy body pathologic changes, iron deposition, cellular inflammation, and reactive astrocytosis in implant regions. Manual cell counts were done of RPE cells. RESULTS: Hematoxylin-eosin and alpha-synuclein immunostains confirmed the diagnosis of PD. Needle tracts with matrix material and RPE cells were observed in the context of local inflammatory and astrocytic reactive change. A total of 118 cells were counted (estimated 0.036% survival). CONCLUSIONS: Retinal pigment epithelial cells are seen in human brain 6 months postimplantation, but overall survival of implanted cells appeared poor.

Replacement of the RPE monolayer.

There are numerous scenarios in which replacing the diseased RPE monolayer is an attractive but as yet unrealised goal. The proof of concept that vision can be improved by placing a healthy neuroretina onto a different, healthy, underlying RPE layer is demonstrated in patch graft transplantations. The surgical procedure to relocate the neuroretina is both complex and is hampered by postoperative complications and as such newer replacement procedures are also being investigated including stem cell replacement therapies. Past studies have largely focused on using cell suspensions and have had disappointing outcomes largely due to the lack of control over cellular differentiation, incomplete attachment onto Bruch's membrane and subsequent integration into the existing RPE monolayer. The choice of which cells to transplant is still under investigation and is complicated by factors such as the ease of collection of an adequate sample, rejection following implantation, the age of the cells and ethical issues. In all these situations, however, understanding the mechanisms of cellular differentiation are likely to be prerequisite to future successes.The current research into replacing the RPE monolayer is briefly discussed with reference to our experiences comparing IPE and RPE cells in an in vitro environment.

Overexpression of integrin alpha6 and beta4 enhances adhesion and proliferation of human retinal pigment epithelial cells on layers of porcine Bruch's membrane.

Transplantation of retinal pigment epithelium (RPE) following removal of choroidal neovascular membranes has been attempted in patients with age-related macular degeneration (AMD). However, inability of transplanted RPE to initially attach and subsequently proliferate on Bruch's membrane may lead to failure of RPE transplants and poor visual outcomes. Integrin alpha(6)beta(4) functions as a receptor for laminin, the major component of Bruch's membrane, and mediates the stable attachment of most epithelial cells to the underlying basement membrane. To improve adhesion and proliferation of transplanted RPE on Bruch's membrane, we elucidated the roles of integrin alpha(6)beta(4) in RPE adhesion to extracellular matrix and investigated whether ex vivo gene transfer of integrin alpha(6) and beta(4) in RPE could promote adhesion and proliferation of transplanted RPE on Bruch's membrane. The expression of integrin alpha(6) and beta(4) mRNA and surface protein in ARPE-19 cells was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometric analysis. We generated point mutation in the ligand binding domain of integrin alpha(6) and beta(4) by using site-directed mutagenesis and transfected these mutated constructs into ARPE-19 cells. Adhesion assay was used to determine the roles of integrin alpha(6) and beta(4) in RPE adhesion to extracellular matrix. In addition, we transfected full-length alpha(6) cDNA or beta(4) cDNA into ARPE-19 cells. The reattachment and proliferation ratios of alpha(6)-cDNA- or beta(4)-cDNA-transfected ARPE-19 cells on different layers of Bruch's membrane were determined by cell adhesion and proliferation assays. Cell morphology and surface coverage were evaluated by scanning electron microscopy 7 days after plating on various layers of Bruch's membrane. We found that integrin alpha(6) and beta(4) mRNA and proteins were constitutively expressed in ARPE-19 cells. Decreased endogenous integrin alpha(6) and beta(4) expression by selective mutation of amino acid residues caused a significant reduction in adhesion of ARPE-19 cells to laminin 5. Modification of integrin expression by transfection of alpha(6) cDNA into ARPE-19 cells induced a significant increase in cell adhesion to laminin 5, fibronectin, whereas transfection with beta(4) cDNA caused increased adhesion only to laminin 5. alpha(6)-cDNA-transfectants increased cell attachment and proliferation on all layers of Bruch's membrane, whereas beta(4)-cDNA-transfectants enhanced adhesion and proliferation on basal lamina and inner collagenous layers. These data indicate that integrin alpha(6) and beta(4) play a role in adhesion of ARPE-19 cells to extracellular matrix. Modification of integrin expression by ex vivo genetic manipulation in RPE might be an alternative strategy to increase the success of RPE transplantation.

Transplantation of tissue-engineered retinal pigment epithelial cell sheets in a rabbit model.

The retinal pigment epithelium (RPE) plays an important role in maintaining a healthy neural retina. With changes due to age, morbidity or removal of choroidal neovascularis developed as a means ofation, damage or defects of the RPE occur. Accordingly, RPE transplantation techniques have been repairing the damaged RPE. We conducted a study to transplant tissue-engineered RPE cell sheets in a rabbit model. RPE cells were isolated from pigmented rabbit eyes and seeded on temperature-responsive culture surfaces. Cultured RPE cells were arranged as a monolayer with a cobblestone cell shape that is characteristic of native RPE. The pigmented RPE cell sheets were non-invasively harvested without enzymatic treatment simply by reducing the culture temperature. Using 3-port vitrectomy, RPE cell sheets were transplanted into the subretinal space of albino rabbits. Seven days after surgery, the rabbits were sacrificed, and the eyes were enucleated and examined under both light and electron microscopy. After transplantation, our results show that the RPE cell sheets attached to the host tissues in the subretinal space more effectively than with the injection of isolated cell suspensions. Although the cell sheets maintained a monolayer structure in most areas, they were slightly folded or wrinkled in some regions. We conclude that tissue-engineered RPE cell sheets harvested from temperature-responsive culture dishes can be effectively transplanted beneath the neural retina.

Topical doxycycline can induce expression of BDNF in transduced retinal pigment epithelial cells transplanted into the subretinal space.

PURPOSE: To determine whether topical doxycycline (DOX) induces the expression of brain-derived neurotrophic factor (BDNF) by BDNF-transduced retinal pigment epithelial (RPE) cells transplanted into the subretinal space of rats. METHODS: A rat RPE cell line that can express BDNF by exposure to DOX was created (Tet-BDNF-RPE). The expression of BDNF was examined by ELISA, Western blot analysis, and real-time PCR. The expression of BDNF was controlled by exposure to DOX in vitro. Tet-BDNF-RPE cells were transplanted into the subretinal space of rats, and the rats were exposed to constant light 1 day or 1 month after the transplantation. The rats were followed with or without topical DOX and examined electrophysiologically and histologically. RESULTS: The expression of BDNF was upregulated by exposure of Tet-BDNF-RPE cells to DOX in vitro. The optimal concentration for inducing BDNF expression was 0.5 to 1.0 microg/mL DOX. BDNF expression was also increased in vivo by topical DOX after subretinal transplantation of Tet-BDNF-RPE cells. Statistically significant protection of the electroretinogram amplitudes were found 3 days or 1 month after transplantation, and the outer nuclear layer was better preserved 7 days or 1 month after transplantation in the rats treated by 5 or 10 mg/mL/d topical DOX than rats treated by other conditions or sham-operation rats. CONCLUSIONS: The expression of BDNF can be significantly increased by topical DOX after Tet-BDNF-RPE subretinal transplantation. Better photoreceptor protection against phototoxicity was achieved by DOX eye drops after the cell transplantation.

Vision improvement in retinal degeneration patients by implantation of retina together with retinal pigment epithelium.

PURPOSE: To demonstrate efficacy and safety of the implantation of neural retinal progenitor cell layers (sheets) with its retinal pigment epithelium (RPE) in retinitis pigmentosa (RP) and dry age-related macular degeneration (AMD) patients with 20/200 or worse vision in the surgery eye. DESIGN: Interventional nonrandomized clinical trial. METHODS: Ten patients (six RP, four AMD) received retinal implants in one eye and were followed in a phase II trial conducted in a clinical practice setting. Early Treatment Diabetic Retinopathy Study (EDTRS) was the primary outcome measure. All implant recipients and nine of 10 tissue donors were deoxyribonucleic acids typed. RESULTS: Seven patients (three RP, four AMD) showed improved EDTRS visual acuity (VA) scores. Three of these patients (one RP, two AMD) showed improvement in both eyes to the same extent. Vision in one RP patient remained the same, while vision in two RP patients decreased. One RP patient has maintained an improvement in vision from 20/800 to 20/200 ETDRS for more than five years; at the six-year examination, it was still maintained at 20/320 while the nonsurgery eye had deteriorated to hand motion vision. This patient also showed a 22.72% increase in light sensitivity at five years compared to microperimetry results at two years; the other patients showed no improved sensitivity. Although no match was found between donors and recipients, no rejection of the implanted tissue was observed clinically. CONCLUSIONS: Seven (70%) of 10 patients showed improved VA. This outcome provides clinical evidence of the safety and beneficial effect of retinal implants and corroborates results in animal models of retinal degeneration.

A novel rabbit model for studying RPE transplantation.

PURPOSE: The goal of this project was to develop a model of retinal pigment epithelium (RPE) transplantation that permits extensive and reliable analysis of the transplants. METHODS: Cultures of newborn rabbit RPE were evaluated by morphology, electrophysiology, and the expression of zonula occludens-1, cytokeratin, and the melanocyte marker S-100. Cells labeled with 5,6-carboxyfluorescein diacetate succinimidyl ester (CFDA-SE) were transplanted into the subretinal space of rabbits with a 30-gauge needle without making a conjunctival flap or sclerotomy. The transplants were examined by fundus photography, confocal scanning laser ophthalmoscopy (cSLO), optical coherence tomography (OCT), and angiography. At 2 months, the retina was examined histochemically. RESULTS: A 1-minute incubation at 37 degrees C with 20 muM CFDA-SE did not affect morphology or the expression of marker proteins. In coculture, the labeled cells integrated into monolayers that developed a normal transepithelial electrical resistance of 400 to 450 Omega . cm(-2). Dye was not transferred from labeled to nonlabeled RPE cells. Transplanted RPE was detectable for at least 2 months. Angiography demonstrated an intact blood-retinal barrier. The normal morphology of the retina and lack of debris in the subretinal space suggested that the transplanted RPE was functional. CONCLUSIONS: Primary cultures of newborn rabbit RPE were highly differentiated, even when labeled with CFDA-SE. Labeled cells were observed long-term in vitro and in vivo. This model can be used to examine how culture and transplantation protocols affect the reformation of a functional RPE monolayer. The similar size of rabbit and human eyes will facilitate the translation of these protocols to the bedside.

Spheramine for treatment of Parkinson's disease.

Spheramine (Bayer Schering Pharma AG, Berlin, Germany) is currently being tested as a new approach for the treatment of Parkinson's disease (PD). It consists of an active component of cultured human retinal pigment epithelial (hRPE) cells, attached to an excipient part of cross-linked porcine gelatin microcarrriers. Spheramine is administered by stereotactic implantation into the striatum of PD patients and the use of immunosuppression is not required. Current pharmacologic therapies of PD are oriented to the administration of dopaminergic medications. Human RPE cells produce levodopa, and this constitutes the rationale to use Spheramine for the treatment of PD. The preclinical development of Spheramine included extensive biologic, pharmacologic, and toxicologic studies in vitro and in animal models of PD. The first clinical trial in humans evaluated the safety and efficacy of Spheramine implanted in the postcommissural putamen contralateral to the most affected side in six patients with advanced PD. This open-label study demonstrated good tolerability and showed sustained motor clinical improvement. A phase II double-blind, randomized, multicenter, placebo-controlled (sham surgery) study is underway to evaluate safety, tolerability, and efficacy of Spheramine implanted bilaterally into the postcommissural putamen of patients with advanced PD. Spheramine represents a treatment approach with the potential of supplying a more continuous delivery of levodopa to the striatum in advanced PD than can be achieved with oral therapy alone.

In-vivo PET imaging of implanted human retinal pigment epithelium cells in a Parkinson's disease rat model.

BACKGROUND AND AIM: Researchers find that monitoring the differentiation of implanted cells in vivo is difficult. This study was designed to show that it is possible to track the efficacy of transplanted human retinal pigment epithelial cells (RPE cells) in a rat model of Parkinson's disease by using positron emission tomography (PET). METHODS: RPE cells or normal saline were injected into striatum of the injured side of the rat model in treated and control groups, respectively. PET imaging of both groups was undertaken before transplantation and at intervals afterwards, using C-raclopride and C-beta-CFT as the markers. Observation of the rats' behaviour and immunofluorescence confocal microscopy were also used to prove the PET results. RESULTS: PET studies showed increased accumulation of C-raclopride and decreased C-beta-CFT in the injured side of striatum in both groups. C-raclopride decreased along with a concomitant increase of C-beta-CFT after transplantation in the treated group. The changes shown by the PET studies paralleled the behavioural states and confocal microscopy observations in the treated animals. CONCLUSION: These results suggest that even a clinical PET scanner could, to a certain extent, provide some information on the existence and in-vivo differentiation of RPE cells in a rat model of Parkinson's disease.

[Autologous translocation of large retinal pigment epithelium choroid patches in age-related macular degeneration]. / Autologe Translokation grosser Pigmentepithel-Aderhaut-Exzisate bei feuchter Altersmakulopathie.

BACKGROUND: The latest development in ARMD surgery is the translocation of an autologeous pigment epithelium choroid patch. The method has technical shortcomings: The transplant is excised including the overlaying retina and inserted through a retinotomy near the posterior pole thus causing iatrogenic field defects. For the same reasons the size of the transplant is limited. MATERIALS AND METHODS: The technique was modified as follows: lens surgery using a special PCL with equal power in water and silicone oil, 180 degrees retinotomy just at the temporal ora serrata, subretinal surgery including patch transplantation with the retina folded over nasally and fixed by PFCL, complete silicone oil tamponade without any water remaining. PATIENTS: 12 consecutive cases, age 79 (70 - 86) years, 4 RPE detachments and rips, 8 subretinal hemorrhages from wet ARMD, follow-up in 10 eyes over 15.3 (3 - 23) months. Time courses for visual acuity, depth of central scotoma, OCT and FAG. RESULTS: The mean diameter of the transplants was 16.5 (9 - 33) degrees . Silicone explantation in 7 / 10. Complications in 3 / 10: 1 macula puckering, 1 peripheral detachment, 1 PVR detachment. According to FAG the transplant vascularises in 4 - 6 weeks. 4 / 10 eyes reached visual acuity > 0.2 with limited reading capability. Central scotoma depth remained constant at -11 dB. Function deteriorated again after 6 - 9 months with cystoid degeneration and retinal thickening. 8 / 11 patients estimated the operated eye to be superior to the untreated partner eye. CONCLUSIONS: Patch transplantation is able to restore limited reading capability in eyes having minor damage of the central retina. The best cases for this type of operation are RPE rips and recent sub-RPE haemorrhages. The functional success lasts 5 to 9 months, then the retina over the transplant begins to degenerate.

Angiographic evidence for revascularization of an rpe-choroid graft in patients with age-related macular degeneration.

PURPOSE: To study graft perfusion using fluorescein angiography (FA) and indocyanine green angiography (ICG) after the translocation of an autologous retinal pigment epithelium (RPE)-choroid graft in patients with exudative age-related macular degeneration (AMD). METHODS: Retrospective observational case series of 31 patients with AMD who had FA and/or ICG performed after an RPE-choroid graft translocation. The FAs (n = 25) and ICGs (n = 23) were assessed by an independent masked reader for the presence of early fluorescence of the graft in FA, and for perfusion of the choroidal vessels of the graft and recipient bed in ICG. RESULTS: Early fluorescence of the graft was present in 23 of the 25 FAs. Perfusion of the graft vasculature was observed in 12 of the 23 ICGs. The two grafts that lacked early fluorescence in FA also had no signs of choroidal perfusion of the graft and the recipient bed with ICG. CONCLUSION: Revascularization of the RPE-choroid graft was observed in all but 2 of the 31 patients either by early fluorescence of the graft by FA or by identification of perfused choroidal graft vessels with ICG from 1 week up to 3 years after surgery. For assessment of revascularization of the graft evaluation of the early phase of the FA is recommended.

Retinal pigment epithelium (RPE)-choroid graft translocation in the treatment of an RPE tear: preliminary results.

AIM: To investigate whether retinal pigment epithelium (RPE)-choroid translocation would be a suitable treatment for RPE tears, which have a poor prognosis and are encountered more often since the introduction of anti-(vascular endothelial growth factor (VEGF)) therapy for exudative age-related macular degeneration (AMD). METHODS: Prospective interventional case series of six eyes of six patients with AMD with an RPE tear treated with an RPE-choroid translocation. The RPE tear occurred in a vascularised pigment epithelium detachment in four patients and after treatment in the other two. Preoperative and postoperative evaluation included ETDRS visual acuity (VA) and fixation testing. The follow-up period ranged from 6 months to 2 years. RESULTS: The mean preoperative VA was 20/160 (range 20/400-20/80). The mean VA at the last examination after surgery was 20/80 (range 1/60-20/50). One of the six patients had a preoperative VA of >/=20/80, and four had a VA of 20/80 or better at their last examination. Foveal fixation on the graft was present in five of the six eyes up to the last examination. CONCLUSION: These preliminary data show that an RPE-choroid translocation may be a treatment option for patients with an RPE tear.

Evidence of retinal function using microperimetry following autologous retinal pigment epithelium-choroid graft in macular dystrophy.

PURPOSE: To describe the outcomes of autologous retinal pigment epithelium (RPE)-choroid graft in macular dystrophy. METHODS: In this prospective interventional case series, five patients with macular dystrophy were enrolled to undergo autologous RPE-choroid patch graft between August 2005 and January 2007. All patients received preoperative and postoperative evaluations including visual acuity, contrast sensitivity, reading ability, microperimetry, fluorescein angiography, indocyanine green angiography, fundus autofluorescence (AF) imaging, and optical coherence tomography (OCT). RESULTS: Patients were followed up for an average of 13.4 (9-23) months. Two patients gained reading acuity but only one regained visual task function after graft. This was maintained for approximately 12 months. Although there is an overall loss of visual acuity, contrast sensitivity, and reading ability, postoperative microperimetry demonstrated retinal sensitivity over the graft in all patients with maximum sensitivity, using a Goldmann size III stimulus of 200-ms duration, ranging from 12 to 20 dB. After surgery, one patient developed retinal detachment and two required cataract extraction at the time of removal of oil. ICG angiography demonstrated perfusion of the graft in four patients. With image registration, homogenous AF pattern in areas of the graft was found to be associated with retinal sensitivity. CONCLUSIONS: Autologous RPE-choroid graft can be performed in patients with macular dystrophy. Although microperimetry showed evidence of retinal function over a perfused and autofluorescent graft, the overall loss of visual acuity and reading ability raises concerns over the use of this novel surgical technique in these patients.

Influence of intraoperative course on visual outcome after an RPE-choroid translocation.

PURPOSE: In a previous study, preoperative variables were correlated with postoperative visual outcome after the translocation of a free RPE-choroid graft. The present study was conducted to investigate whether the intraoperative course was an independent factor influencing visual outcome in these patients. METHODS: This was a prospective interventional case series of 48 patients with exudative AMD treated with an RPE-choroid translocation. Preoperative and postoperative evaluation included ETDRS visual acuity (VA) and fixation testing by a masked examiner. Four critical surgical steps were evaluated, and the intraoperative course was graded from 0 (uncomplicated surgery) to 5 (most complicated surgery). The relationship between intraoperative course adjusted for preoperative delay/lesion composition and visual outcome at 3 months and 1 year after surgery was analyzed with multivariate analysis. RESULTS: The mean VA (logMAR) improved slightly from 0.99 before surgery to 1.00, 0.94, 0.89, and 0.91 after 3, 6, 9, and 12 months, respectively. Foveal fixation on the graft was present in 34 (71%) of the eyes at 1 year after surgery. The intraoperative course was statistically significantly associated with the DeltaVA (logMAR) at 3 months (P = 0.037) and at 1 year after surgery (P = 0.020) and if measured as gain or loss of > or =2 ETDRS-lines (odds ratio [OR] 1.8, 95% confidence interval [CI] 1.7 to 2.8, P = 0.027) and > or =3 ETDRS lines (OR, 2.2, 95% CI 1.9-3.5, P = 0.003); better surgery was associated with visual gain whereas eventful surgery was associated with visual loss. CONCLUSIONS: The intraoperative course adjusted for preoperative variables had a statistically significant influence on postoperative visual outcomes in patients treated with a free RPE-choroid translocation. Refining the surgery could improve results.

Morphological and functional rescue in RCS rats after RPE cell line transplantation at a later stage of degeneration.

PURPOSE: It is well documented that grafting of cells in the subretinal space of Royal College of Surgeons (RCS) rats limits deterioration of vision and loss of photoreceptors if performed early in postnatal life. What is unclear is whether cells introduced later, when photoreceptor degeneration is already advanced, can still be effective. This possibility was examined in the present study, using the human retinal pigment epithelial cell line, ARPE-19. METHODS: Dystrophic RCS rats (postnatal day [P] 60) received subretinal injection of ARPE-19 cells (2 x 10(5)/3 microL/eye). Spatial frequency was measured by recording optomotor responses at P100 and P150, and luminance threshold responses were recorded from the superior colliculus at P150. Retinas were stained with cresyl violet, retinal cell-specific markers, and a human nuclear marker. Control animals were injected with medium alone. Animals comparably treated with grafts at P21 were available for comparison. All animals were treated with immunosuppression. RESULTS: Later grafts preserved both spatial frequency and threshold responses over the control and delayed photoreceptor degeneration. There were two to three layers of rescued photoreceptors even at P150, compared with a scattered single layer in sham and untreated control retinas. Retinal cell marker staining showed an orderly array of the inner retinal lamination. The morphology of the second-order neurons was better preserved around the grafted area than in regions distant from graft. Sham injection had little effect in rescuing the photoreceptors. CONCLUSIONS: RPE cell line transplants delivered later in the course of degeneration can preserve not only the photoreceptors and inner retinal lamination but also visual function in RCS rats. However, early intervention can achieve better rescue.

Optical coherence tomography on autologous translocation of choroid and retinal pigment epithelium in age-related macular degeneration.

PURPOSE: To analyse structural changes after autologous translocation of choroid and retinal pigment epithelium (RPE) in patients with age-related macular degeneration (AMD) using optical coherence tomography (OCT). METHODS: We performed a prospective nonrandomised study in 29 consecutive patients, who underwent submacular surgery with translocation of an autologous full-thickness graft of RPE, Bruch's membrane, and choroid. All patients had recent loss of reading vision due to AMD. OCT was performed before surgery and at 3- and 6- month follow-up to analyse the morphological appearance of the graft and the overlying retina. RESULTS: Maximum retinal thickness decreased from mean 408 microm (standard deviation (SD) 127 microm) preoperative to mean 373 microm (SD 104 microm) at 6-month follow-up (P=0.094). In 11 cases (40%), a nearly physiological shape of the retina was seen at this time point. A macular hole persisted in two eyes after silicone oil removal. In most eyes, the highly reflective band of the graft presumably corresponding to RPE was continuous with the surrounding RPE band in all six OCT scans. Eyes with flat appearance of the graft at 6-month follow-up (<300 microm) showed a significantly better functional outcome than eyes with more prominent grafts. Interestingly, most patients did not complain about metamorphopsia, even though the graft was prominent or wrinkled in some cases. CONCLUSION: OCT is a useful tool in monitoring intra- and subretinal changes after subretinal surgery with graft translocation. We demonstrated that graft translocation may lead to a normalisation of retinal thickness and stabilisation of visual acuity.

RPE transplantation and its role in retinal disease.

Retinal pigment epithelial (RPE) transplantation aims to restore the subretinal anatomy and re-establish the critical interaction between the RPE and the photoreceptor, which is fundamental to sight. The field has developed over the past 20 years with advances coming from a large body of animal work and more recently a considerable number of human trials. Enormous progress has been made with the potential for at least partial restoration of visual function in both animal and human clinical work. Diseases that have been treated with RPE transplantation demonstrating partial reversal of vision loss include primary RPE dystrophies such as the merTK dystrophy in the Royal College of Surgeons (RCS) rat and in humans, photoreceptor dystrophies as well as complex retinal diseases such as atrophic and neovascular age-related macular degeneration (AMD). Unfortunately, in the human trials the visual recovery has been limited at best and full visual recovery has not been demonstrated. Autologous full-thickness transplants have been used most commonly and effectively in human disease but the search for a cell source to replace autologous RPE such as embryonic stem cells, marrow-derived stem cells, umbilical cord-derived cells as well as immortalised cell lines continues. The combination of cell transplantation with other modalities of treatment such as gene transfer remains an exciting future prospect. RPE transplantation has already been shown to be capable of restoring the subretinal anatomy and improving photoreceptor function in a variety of retinal diseases. In the near future, refinements of current techniques are likely to allow RPE transplantation to enter the mainstream of retinal therapy at a time when the treatment of previously blinding retinal diseases is finally becoming a reality.