To extrapolate from the results of the Freed group Parkinson's study to not just cell implantation but all regenerative therapy strategies is sadly simplistic and underinformed, just as Ms. Kolata's NYT article suffered from a lack of perspective. She neglected to speak with any of the other major researchers involved in Parkinsonian implant work.
The Freed study involved (ultimately) 33 patients who received injections of strands of fetal tissue into the putamen. Five of them have now developed what is obviously a tragic outcome, uncontrollable motor activity. But the context is:
1) The Freed treatment protocol is different from that used by any of the other cell implantation programs. They use tissue strands, which are less easily manipulated and easily placed than are the cells in liquid suspension used by all other programs. And while they know some dopamine production was present, such tissue samples are a hodgepodge of cells. They injected them through the forehead, a different vector than used by any other program.
2) In contrast, the implant groups in Sweden, France, and Canada have completed 35 research implantations in Parkinson's patients. These date back as far as 1987. None of these patients has ever developed the 'persistent dyskinesia' described in the five patients in the Freed study. Many of them are described as having shown improvement for up to 3-4 years, after which time, the gradual degeneration in the substantia nigra overtook the benefits provided by the implants.
3) The other major cohort of implantation patients is Diacrin's, the more than thirty patients who have received porcine cell implants for Parkinson's. These go back more than four years. Again, no cases of persistent dyskinesia have ever been seen. There will be an unblinding of a placebo controlled study this month, which will be a counterpoint to the Freed study.
4) The symptoms reported by the Freed group in those sadly afflicted patients ('writhing and twisting') strike me as more choreiform than Parkinsonian. There is a hypothesis going around the cell implant field (which has been aware of these patients for a year now) that this particular surgical protocol used may have inadvertently damaged inhibitory GABAnergic tracts, leading to the eventual development of what sounds somewhat like a Huntington's Chorea constellation of motor sx--rather than the dopamine overrelease postulated.
All in all, rather than indicting the field--and strategy--of cell implantation as a whole, the fact that this particular adverse event was restricted to a small group in one study whose treatment protocol was unique to the field may say more about the treatment protocol than the overriding strategy. And to conclude that this proves that current regenerative/trophic treatment strategies are all dangerous and doomed is somewhat histrionic.
NeuroInvestment
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