Human retinal pigment epithelial cell implants ameliorate motor deficits in two rat models of Parkinson disease.

Intrastriatal transplantation of gelatin microcarrier-attached human retinal pigment epithelial cells (hRPE-GM) may represent an alternative source for cell therapy in Parkinson disease (PD). The use of human retinal pigment epithelial (hRPE) cells in PD relies on the capacity of these cells to produce l-dopa as an intermediate product in the eumelanin synthesis pathway. We investigated the behavioral effects of hRPE-GM implants on forelimb use asymmetries and hindlimb motor deficits in unilateral and bilateral 6-hydroxydopamine (6-OHDA) rat models of PD. We report that intrastriatal unilateral implantation of hRPE-GM in rats with 6-OHDA nigrostriatal lesions produce an amelioration of the contralateral forelimb disuse and the contralateral hindlimb deficits. These results further support the possibility that implantation of cultured hRPE cells may be a promising therapeutic option for patients with PD.

Characterization and survival of long-term implants of human retinal pigment epithelial cells attached to gelatin microcarriers in a model of Parkinson disease.

Previous studies have demonstrated that the intrastriatal implantation of human retinal pigment epithelial cells attached to gelatin microcarriers (hRPE-GM) ameliorates behavioral deficits in animal models of Parkinson disease. However, there are only sparse data on cell survival in the host. In this study, we characterized a variety of retinal pigment epithelial (RPE)-specific markers in vitro and used these markers to investigate the long-term survival of hRPE-GM implants. Sprague-Dawley rats (n = 22) were unilaterally lesioned with 6-hydroxydopamine (6-OHDA) and implanted with hRPE-GM without immunosuppression. Rats were euthanized at 48 hours, 7 days, 4 weeks, and 5 months postimplant and immunohistochemically processed using the following antibodies: 1) human-specific nuclear mitotic apparatus protein (NuMA-Ab2), 2) epithelial-specific extracellular matrix metalloproteinase inducer (EMMPRIN), 3) RPE cell-specific RPE65, and the inflammation markers 4) glial fibrillary acidic protein and 5) ED1 (rat CD68). Our analysis revealed NuMA-, EMMPRIN-, and RPE65-immunoreactive cells at different times postimplant. The morphologic features of hRPE cell implants (at 48 hours and 5 months) were confirmed by electron microscopy. Furthermore, despite evidence of chronic inflammation at the later time point, there is an appreciable number of surviving hRPE cells. This study suggests that hRPE-GM implants can survive in the absence of immunosuppression and can be potentially used as an alternative for treating Parkinson disease.

Modulation of Abnormal Metabolic Brain Networks by Experimental Therapies in a Nonhuman Primate Model of Parkinson Disease: An Application to Human Retinal Pigment Epithelial Cell Implantation.

Abnormal covariance pattern of regional metabolism associated with Parkinson disease (PD) is modulated by dopaminergic pharmacotherapy. Using high-resolution 18F-FDG PET and network analysis, we previously derived and validated a parkinsonism-related metabolic pattern (PRP) in nonhuman primate models of PD. It is currently not known whether this network is modulated by experimental therapeutics. In this study, we examined changes in network activity by striatal implantation of human levodopa-producing retinal pigment epithelial (hRPE) cells in parkinsonian macaques and evaluated the reproducibility of network activity in a small test-retest study. METHODS: 18F-FDG PET scans were acquired in 8 healthy macaques and 8 macaques with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced bilateral nigrostriatal dopaminergic lesions after unilateral putaminal implantation of hRPE cells or sham surgery. PRP activity was measured prospectively in all animals and in a subset of test-retest animals using a network quantification approach. Network activity and regional metabolic values were compared on a hemispheric basis between animal groups and treatment conditions. RESULTS: All individual macaques showed clinical improvement after hRPE cell implantation compared with the sham surgery. PRP activity was elevated in the untreated MPTP hemispheres relative to those of the normal controls (P < 0.00005) but was reduced (P < 0.05) in the hRPE-implanted hemispheres. The modulation observed in network activity was supported by concurrent local and remote changes in regional glucose metabolism. PRP activity remained unchanged in the untreated MPTP hemispheres versus the sham-operated hemispheres. PRP activity was also stable (P ≥ 0.29) and correlated (R2 ≥ 0.926; P < 0.00005) in the test-retest hemispheres. These findings were highly reproducible across several PRP topographies generated in multiple cohorts of parkinsonian and healthy macaques. CONCLUSION: We have demonstrated long-term therapeutic effects of hRPE cell implantation in nonhuman primate models of PD. The implantation of such levodopa-producing cells can concurrently decrease the elevated metabolic network activity in parkinsonian brains on an individual basis. These results parallel the analogous findings reported in patients with PD undergoing levodopa therapy and other symptomatic interventions. With further validation in large samples, 18F-FDG PET imaging with network analysis may provide a viable biomarker for assessing treatment response in animal models of PD after experimental therapies.

Intrastriatal implantation of human retinal pigment epithelial cells attached to microcarriers in advanced Parkinson disease.

BACKGROUND: Human retinal pigment epithelial (RPE) cells produce levodopa and can be isolated from postmortem human eye tissue, grown in culture, and implanted into the brain attached to microcarriers. These implants ameliorated the motor deficits in rodent and nonhuman primate models of Parkinson disease. OBJECTIVE: To evaluate the safety and efficacy of unilateral implantation of human RPE cells attached to gelatin microcarriers into the putamen contralateral to the more symptomatic side of patients with Parkinson disease. DESIGN: Open-label pilot study. SETTING: A tertiary referral center for movement disorders. PATIENTS: Six patients with advanced Parkinson disease. INTERVENTIONS: We performed stereotactic intrastriatal implantation of approximately 325,000 RPE cells on microcarriers. MAIN OUTCOME MEASURE: Change from baseline to 12 months in the Unified Parkinson's Disease Rating Scale motor subscore with the patients in the practically defined off state (not taking antiparkinsonian medications for at least 12 hours overnight). RESULTS: The implants were well tolerated. We observed an average improvement of 48% at 12 months after implantation in the Unified Parkinson's Disease Rating Scale motor subscore with the patient in the off state, which was sustained through 24 months. Improvement was also observed in activities of daily living, quality of life, and motor fluctuations. No off-state dyskinesias were observed. CONCLUSIONS: Implants of human RPE cells attached to gelatin microcarriers appear to be safe and well tolerated, and they improved motor symptoms in patients with Parkinson disease. On the basis of these results, a randomized, double-blind, placebo-controlled study has been initiated.

Implantation of Spheramine in advanced Parkinson's disease (PD).

Evaluation of the safety and efficacy of unilateral stereotactic implantation of cultured human retinal pigment epithelial (hRPE) cells attached to microcarriers (Spheramine) in patients with advanced PD in an open label pilot study. Six patients with advanced PD (3 males; 3 females; mean age 52.2 years; mean duration of PD 10.2 years; mean Hoehn and Yahr stage "off" 3.75) were assessed at baseline and post-operatively using the modified CAPIT. Each patient underwent MRI-guided stereotactic transplantation of 325,000 hRPE cells attached to microcarriers in 5 tracts, 5 mm apart in the post-commissural putamen contralateral to the most affected side. Immunosuppression was not used. The UPDRS Motor (UPDR-M) score in the practically defined "off" state was the primary outcome measure. At 6 months post-op, the mean UPDRS-M (off) score improved to 35 (34%) from a pre-op baseline mean of 52 (p <.001). Secondary outcome measures improved including the total UPDRS (33%), Timed Motor Tests (on, 14%; off, 23%), PDQ39 QOL (30%), and Schwab and England score (on, 11%; off, 30%). Bilateral improvements have been observed in motor symptoms, with the greatest effect seen contralateral to the implants. Three of six patients currently have lower Dyskinesia Rating Scale scores than at baseline, while the scores of the other three are unchanged from baseline values. No "off-state" dyskinesias have been observed. Thus Spheramine implantation therapy appears to be safe and well tolerated for 6 months post-implantation.

Striatal xenotransplantation of human retinal pigment epithelial cells attached to microcarriers in hemiparkinsonian rats ameliorates behavioral deficits without provoking a host immune response.

Attachment of donor cells to microcarriers has been reported to make them more tolerable for transplantation into the brain. Human retinal pigment epithelial (hRPE) cells have been previously reported to contain enzymes for the production of dopa. Therefore, we examined the host immune response and behavioral effects of xenotransplantation of hRPE cells attached to microcarriers (hRPE-M) into the striatum of unilateral dopamine-depleted rats. Thirty-four adult rats were lesioned with 6-OHDA injections into the medial forebrain bundle on the right side. After 5 weeks of testing for apomorphine-induced rotations (AIR), animals were randomized for right striatal surgery into the following four groups: hRPE-M (group 1), hRPE alone (group 2), microcarriers alone (group 3), or needle tract alone (group 4). Following surgery, animals were tested for AIR every 4 weeks for a period of 12-18 weeks and thereafter euthanized. There was a significant reduction in AIR scores posttransplantation in all groups of animals in the initial observation points at 4 weeks and 8 weeks. However, there was a gradual return to baseline scores in groups 2, 3, and 4 animals at 12 weeks and at 18 weeks only group 1 animals had statistically significant (p = 0.001, repeated measures ANOVA, means comparison, predetermined contrasts) reduction in AIR scores. Brain tissue from representative animals from each group was cut into 30-microm coronal sections, stained for cresyl violet, tyrosine hydroxylase (TH), and markers for host immune activation. Sections through the striatum from group 1 animals revealed microcarriers with attached cells resembling RPE cells. No evidence of transplanted hRPE cells could be detected in sections from group 2 animals while those from groups 3 and 4 animals showed microcarriers and a needle tract alone, respectively. There was no host TH-immunoreactive sprouting response in the striatum in any of the groups and the host immune response was minimal. These results suggest that intrastriatal hRPE-M xenotransplantation into rats is well tolerated without systemic immunosuppression and that such transplants may provide behavioral benefit for parkinsonism.

Intrastriatal transplantation of microcarrier-bound human retinal pigment epithelial cells versus sham surgery in patients with advanced Parkinson's disease: a double-blind, randomised, controlled trial.

BACKGROUND: Human retinal pigment epithelial (RPE) cells produce levodopa and their transplantation into the striatum might improve continuity of administration compared with that achieved with oral levodopa. We aimed to assess the safety, tolerability, and efficacy of transplantation of microcarrier-bound human RPE cells versus a sham surgery control in patients with advanced Parkinson's disease. METHODS: In this randomised, double-blind study eligible patients were aged 36-70 years, had been symptomatic for at least 5 years, were in Hoehn and Yahr stage 3-4 and had unified Parkinson's disease rating scale (UPDRS) motor scores of 38-70 when off medication (off state), and had symptoms that responded to oral levodopa but were insufficiently controlled by optimised pharmacotherapy. Randomisation was done in a 1:1 ratio. Only the neurosurgical team was aware of treatment assignments. During stereotactic transplantation around 325,000 cells per side were injected into the postcommissural putamen; sham surgery patients received partial burr holes. The primary efficacy endpoint was change in UPDRS off-state motor score at 12 months. This study is registered with ClinicalTrials.gov, number NCT00206687. FINDINGS: Of 71 enrolled patients, 35 underwent cell transplantation and 36 sham surgery. Change in mean motor scores did not differ significantly between groups (-10.5 [SD 10.26] for transplantation vs -10.1 [SD 12.26] for sham surgery, p=0.9). The overall rate of adverse events was similar in the two study groups, although the number attributable to surgery or RPE cells (mostly neurological or psychiatric) was higher in transplant recipients. Two and seven patients died in the sham surgery and transplantation group, respectively; one death in the latter group was possibly related to surgery or RPE cells. INTERPRETATION: Transplantation of human RPE cells provided no antiparkinsonian benefits compared with sham surgery. FUNDING: Bayer HealthCare AG.