Think again

 作者:终唇钺     |      日期:2019-03-07 04:09:00
By Emma Young A US experiment which produced “disastrous” results after fetal cells were transplanted into the brains of Parkinson’s disease sufferers has been severely criticised by international experts. Five of 20 patients were left with uncontrollable and untreatable jerky movements, which the US team says are caused by the new dopamine-producing cells going into overdrive. Previous trials of fetal cell transplants in Parkinson’s sufferers in Europe have relieved symptoms in many patients without producing severe side effects. These new “absolutely devastating” results mean fetal transplant experiments have to go right back to the drawing board, said Paul Greene, a neurologist at Columbia University in New York, and one of the researchers. But leading European Parkinson’s experts say the US experiment was seriously flawed. “This study unfortunately used a technique different to those used in previous primate and human studies,” says Lucy Annett of Cambridge University, who has performed transplants in primates. “It had not been properly validated by animal studies.” Anders Björklund, a world leader in human fetal cell transplants at Lund University in Sweden, told New Scientist: “We are convinced this study has no implications for ongoing fetal transplant Parkinson’s programmes.” Over 20 European scientists wrote to the journal Science seven years ago expressing their concern that the funding of a large trial for this technique ignored other, perhaps more promising, approaches. The trial, conducted by a team from Columbia University, involved transplanting fetal brain tissue into the brains of 20 long term Parkinson’s sufferers. Controversially, 20 other patients received sham surgery. Some of the patients showed no improvement in symptoms. For others, the improvements were slight. But after one year, the patients that had showed the most improvement began to develop severe dyskenesia – uncontrollable jerky movements. These were more intense than their original symptoms. The Columbia team say the embryonic cells had gone into overdrive, and were producing too much dopamine. There is no way to turn these cells off. Björklund says other experiments using much higher volumes of fetal tissue have not produced these side effects. He says technical problems with the trial make it impossible to estimate how many of the dopamine-producing cells reached the vital part of the patients’ brains. The surgical technique itself was unusual, he says. The injections were made through the frontal cortex, requiring a long needle. “There are concerns that the tissue may have spilled over into the frontal cortex and have unpredictable results,” he says. Long term storage of the fetal tissue before transplant, and a lack of immuno-suppressive drugs, could also affect the results, he says. Björklund says the study does not in any way dim hopes to use stem cells to cure Parkinson’s. Stem cell experiments in mice have already reported good results. “Using stem cells will make it possible to carefully control the amounts of dopamine-producing tissue being transplanted,” he says. More at: New England Journal of Medicine (vol 344, p 710) Science (vol 263,