Stem cell breakthrough on mice ‘reverses Alzheimer’s’: Chinese scientists in breakthrough experiment
Researchers repair rodents’ brains by transplanting neurons, raising hopes for human cure
In a groundbreaking experiment, Chinese scientists have used human embryonic stem cells to nurse back to health mice afflicted with Alzheimer’s disease.
A team in Shanghai found that by transplanting neurons derived from the cells into the rodents they could reverse their cognitive degeneration.
The breakthrough showed for the first time a practical method to rejuvenate an ageing brain with a fertilised egg, and paved the way for the eventual application of the method to human patients, the researchers said.
Alzheimer’s is a neurodegenerative disorder that affects tens of millions of people. It causes a general decline in brain activity, characterised by memory loss and difficulty in speaking, due to neuron damage in the brain.
Scientists have spent decades searching for a way to reverse such neuron damage.
Previous studies have suggested Alzheimer’s involved too many types of neurons and molecular mechanisms to be treated with stem-cell therapy. Many researchers have regarded stem-cell therapy as too limited and able only to repair very specific types of neurons.
“Stem-cell treatment would offer no cure for Alzheimer’s – that was the impression of many people, including us before the experiment,” said Professor Jing Naihe, lead scientist of the study with the Shanghai Institutes for Biological Sciences, part of the Chinese Academy of Sciences.
But in a paper in Stem Cell Reports, Jing and colleagues reported “encouraging” findings.
Jing’s team used proteins as “lures” to trigger the transformation of the human stem cells into neurons, then transplanted these into the rodents.
About 60 per cent of the human neurons were identified as alien and killed by the rodents’ immune systems, but the rest survived and repaired the damaged regions in their brains.
Mice treated with the method were “comparable” to normal mice in performing cognitive tasks two months after the treatment, and showed steady improvement in memory tests.
“These results indicate the cognitive deficiency of Alzheimer’s disease in mice can be reversed,” they added.
The cells were collected from fertilised human eggs under the guidelines of ethics authorities.
“We used human embryonic stem cells because this method will eventually be used on humans. If the human neurons can get a footing and grow in the brain of a mouse, the chance is high the effect will be even better on a human host,” Jing said.
“The biggest concern of this development is safety. We were afraid that the transplanted cells would mutate to other types of neurons or even cause brain tumours,” Jing said.
“We have been improving the technology and making close observation of the mice for more than seven years. So far no mutation or cancerous development has been detected,” he added.
But he said it was too early to use the method on humans.
“Mice are still very different from humans, so the results on mice do not guarantee the same success on human patients. Our next step is to test the method on primates.
“It will probably be a long time before clinical trials can be carried out on human volunteers,” he added.