Cellular transplantation for Parkinson's disease: a strategy whose time has passed

Overcoming Methodological Challenges for Advancing Stem Cell Therapies in Parkinson's Disease

The quest for new and improved therapies for Parkinson's disease (PD) remains of paramount importance, despite previous trial failures. There is a current debate regarding the potential of stem cell research as a therapeutic approach for PD. The studies of dopaminergic fetal stem cells for PD treatment, their design, and the results of the initial surgical placebo-controlled trials were reviewed in this study. Some of the fundamental methodological challenges and possible strategies to resolve them were proposed. In this article, we argue that the most important impact lies in the proof-of-principle demonstrated by clinical trials for cell replacement strategies in reconstructing the human brain. While some researchers argue that the considerable technical challenges associated with cell therapies for PD warrant the discontinuation of further development using stem cells, we believe that the opposing viewpoints are instrumental in identifying a series of methodological misunderstandings. Here, we propose to expose key challenges to ensure the advancement of the field and unlock the potential of stem cell therapies in PD treatment. Overall, this review underscores the need for further research and innovation to overcome the hurdles in realizing the potential of stem cell-based therapies for PD.

Current Status and Future Perspectives on Stem Cell-Based Therapies for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease, affecting 1%-2% of the population over the age of 65. As the population ages, it is anticipated that the burden on society will significantly escalate. Although symptom reduction by currently available pharmacological and/or surgical treatments improves the quality of life of many PD patients, there are no treatments that can slow down, halt, or reverse disease progression. Because the loss of a specific cell type, midbrain dopamine neurons in the substantia nigra, is the main cause of motor dysfunction in PD, it is considered a promising target for cell replacement therapy. Indeed, numerous preclinical and clinical studies using fetal cell transplantation have provided proof of concept that cell replacement therapy may be a viable therapeutic approach for PD. However, the use of human fetal cells remains fraught with controversy due to fundamental ethical, practical, and clinical limitations. Groundbreaking work on human pluripotent stem cells (hPSCs), including human embryonic stem cells and human induced pluripotent stem cells, coupled with extensive basic research in the stem cell field offers promising potential for hPSC-based cell replacement to become a realistic treatment regimen for PD once several major issues can be successfully addressed. In this review, we will discuss the prospects and challenges of hPSC-based cell therapy for PD.