The loss of a specific cell type, midbrain dopamine neurons in the substantia nigra, is the main cause of motor dysfunction in PD. 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.
Although stem cell-based therapies for PD have some limitations (e.g., dopamine-related stem cell therapy may not correct all known nonmotor symptoms of PD resulting from nondopaminergic pathology; none of the cell-based therapies has yet undergone a successful phase 3 clinical trial), and the use of hPSC derivatives may continue to raise concerns about safety and feasibility, intensive scientific efforts have been committed – and are ongoing – to improve and further optimize the hPSC-based cell therapeutic approach to make it safer, more efficient, and less costly.
Continuing effort, including both basic and clinical investigations, into a deeper understanding of PD etiology is imperative to translate our discoveries into novel therapeutic avenues to treat both motor and nonmotor PD symptoms. In addition, considerable commercial and governmental investment in this field will also be important for overcoming practical limitations, such as the cost of manufacturing mDAPs to make hPSC-based cell therapy a viable therapeutic approach available to large numbers of PD patients.
Stem cell treatment Parkinson’s 
Stem Cell Therapy for Parkinsons
Stem Cell therapy for PD
Presentation by Prof R Barker - University of Cambridge: \"Can we repair the brain in PD using cell-based therapies?\"
