The two patients were part of a small exploratory study in Halifax. In the study, the cells were bathed in the trophic factor GDNF before being implanted into the striatum, the target of dopamine-producing cells. One patient also had cells implanted into the substantia nigra, the origin of the dopamine neurons involved in Parkinson’s.
The study provides a picture of both the clinical improvements in the patients and the physiological outcomes of the experiment. The two patients both experienced progressive improvement in symptoms over a three- to four-year period after their transplantation. The patients also showed positive PET scans for dopamine activity in the regions where grafts had been placed. In their postmortem analysis, Isacson’s team found dopamine-producing neurons along the graft sites, representing about a 10- to 30-percent survival rate in the putamen and slightly lower survival rate in the substantia nigra.
This is the first reported evidence that cells can survive and form connections in the substantia nigra, which Isacson believes may be an important target for future transplant therapies. The postmortem findings also closely correlate to clinical improvements.
Isacson’s team believes it can continue to improve cell-based therapies for Parkinson’s disease by better characterizing and controlling specific populations of cells.