The stem cello "clinics", have nothing as of yet. They recently changed their tune on PD treatment, from an "peripheral injectable" form to an actual " brain opened implant" by transplanting ( so they say) " stem cells " (of a dubious nature) through a n invasive surgery, supposedly into the Substantia Nigra .
The claims for stem cell lines have been blurred and contorted in order to fill the as yet unrealized promise for neural net replacement. It has been extremely difficult to develop working, dependable cell types for the extremely complicated and sensitive task of brain regeneration, especially without making regulatory agencies in our country balk at their inclusion into the realm of approving " safe and effective" cell lines of ethically exempted nature. It really has been a long road fraught with difficulties to invent " the real thing" which will do the job that needs to be done. So many technical considerations still need work! However, I will take heart till my last breath that there still may be a way, soon, I hope!