BACKGROUND: The transplantation of homogenous cells has emerged as an investigational strategy for Parkinson's disease (PD), offering an alternative to symptomatic treatment. OBJECTIVE: We performed a systematic review and meta-analysis to assess its clinical efficacy and safety. METHODS: Electronic searches of MEDLINE, EMBASE, and Cochrane Library were performed on November 2025 to identify clinical trials of defined homogenous cell populations in PD. Eligible studies required validated outcome reporting and extractable data. Continuous measures were synthesized as mean differences (MD) under fixed- or random-effects models depending on heterogeneity. Risk of bias was appraised using Cochrane methodology. RESULTS: Twenty studies including 374 patients met inclusion criteria, of which 14 contributed to pooled analyses. In the OFF state, homogenous cell transplantation demonstrated consistent, statistically significant improvements in total UPDRS at 3 months Mean Difference (MD) 22.04, 95% CI 17.40-26.68, 6 months 27.09, 15.47-38.70, 12 months 29.13, 18.04-40.21, and 24 months 21.01, 3.97-38.06; benefits attenuated beyond 36 months 9.93, -2.16-22.02. Motor UPDRS III showed robust gains across all intervals, particularly in the OFF state at 3 months 14.34, 11.22-17.45 and 12 months 13.59, 10.22-16.97. ON-state outcomes were less consistent, with modest improvements limited to 6 and 24 months. Subgroup analyses indicated beneficial responses with dopaminergic progenitor and retinal pigment epithelial grafts. Reported adverse events were generally mild, transient, and perioperative in nature. CONCLUSIONS: In these open label studies of PD patients, homogenous cell transplantation is associated with meaningful and durable motor improvements, particularly in the OFF state, and demonstrates a favorable safety profile.
Reinisch et al. (Sun,) studied this question.
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