Given the well-defined loss of a specific type of neurons (dopaminergic neurons) in a well defined region of the brain (S. nigra), the concept of cell replacement therapy in PD has emerged already in the early 1980s.Replacing diseased cells with healthy cells, called cell therapy, is similar to the process of organ transplantation only the treatment consists of transplanting cells instead of organs. Some conditions or injuries can be treated through transplantation of entire healthy organs, but there is an acute shortage of donors. Stem cells can serve as an alternate and renewable source for...