Transplanted Dopamine Neurons Can Last a Long Time
Many cell transplants have been shown to produce no long-lasting cells in the recipient. In stem cell treatments, for example, it is frequently the case that the stem cells have a short-term effect on the signaling environment that boosts regeneration by changing the behavior of native cell populations, but the transplanted cells do not take up residence and are gone within a few days to a few weeks. The research noted here lies at the opposite end of the spectrum, however, and confirms that dopamine-generating neurons transplanted to replace those lost to the mechanisms of Parkinson's disease last for a very long time indeed:
To determine the long-term health and function of transplanted dopamine neurons in Parkinson's disease (PD) patients, the expression of dopamine transporters (DATs) and mitochondrial morphology were examined in human fetal midbrain cellular transplants. DAT was robustly expressed in transplanted dopamine neuron terminals in the reinnervated host putamen and caudate for at least 14 years after transplantation.The transplanted dopamine neurons showed a healthy and nonatrophied morphology at all time points. Labeling of the mitochondrial outer membrane protein Tom20 and α-synuclein showed a typical cellular pathology in the patients' own substantia nigra, which was not observed in transplanted dopamine neurons. These results show that the vast majority of transplanted neurons remain healthy for the long term in PD patients, consistent with clinical findings that fetal dopamine neuron transplants maintain function for up to 15-18 years in patients.