This trial is a longitudinal, prospective, interventional, uncontrolled study designed to test, firstly, the safety and secondly, the potential efficacy of intraputaminal grafting of undifferentiated hfSC for the treatment of PD. Patients were monitored carefully for any adverse effects. All patients underwent baseline and 6- and 12-month post-surgery neurological, neuropsychological, MRI, and PET evaluations.