Adult stem cells may hold key

By BRETT FOLEY MEDICAL REPORTER Thursday 16 August 2001 Infographic: The stem cell breakthrough A treatment for Parkinson's and Alzheimer's diseases may be a step closer after Melbourne researchers identified a key to regenerating brain tissue, without using the controversial embryonic stem cells.

The team at the Walter and Eliza Hall Institute identified and isolated from the brains of mice an adult stem cell, which can develop into new nerve cells, or neurons.

The findings, which will be published in the international journal Nature today, will prove that adult neural stem cells may have properties previously thought to be held only in embryonic stem (ES) cells.

ES cell research has attracted controversy recently after US President George W. Bush faced opposition before agreeing to continue federal funding for existing ES cell lines. ES cells, which must be harvested from embryos, are cellular building blocks that can develop into any tissue in the body. A Federal Government committee examining human cloning is poised to deliver a report that may allow Australian scientists to collect ES cells from embryos discarded after the IVF process.

Neural stem cells are rare and their precise position and features have remained unclear since the same research team proved, nine years ago, that the adult brain contained small quantities of these cells.

The head of the research team, Perry Bartlett, and his colleagues embarked on a four-year process to pinpoint the neural stem cells, using sophisticated sieving and marking techniques, from millions of mouse brain cells. After identification they were able to make a concentrated population of mouse stem cells - about 80 per cent pure compared with natural concentrations of less than 0.1 per cent. In laboratory tests the study proved a single stem cell could give rise to thousands of new neurons or muscle cells.

Researchers then transplanted those stem cells back into mouse brains and found they developed into both nerve cells and support cells, which were incorporated into the existing network of brain fibres.

Dr Bartlett said the findings were exciting because they potentially provided a solution to the ethical issues associated with ES cell research. It also avoided the need to transplant foreign stem cells back into adults and risk rejection.

"ES cells probably have got a greater potential to differentiate, but this questions the belief that they are the only cells that can give rise to different cell types," he said. "We see our discovery directed more towards self-repair rather than the idea of putting these cells back into the animal after isolating them. That's a possibility, but there is no deficiency in these stem cells, it's just a matter of activating them."

The next step was to isolate and purify human neural stem cells so they could develop a drug that could trigger those cells to form into human neurons - thus replacing the neurons damaged by Alzheimer's and Parkinson's disease or stroke. Dr Bartlett said they had been given ethics committee approval to begin using human brain tissue, removed during routine surgical procedures, to try to replicate the process with human neural stem cells.

"We know under certain conditions these (neural stem) cells will replace nerve cells naturally, but they are tightly inhibited from developing into neurons," he said. "So the goal is now to drive these cells to overcome their inhibition.

"For stroke and brain injury it could lead to a full replacement of the damaged neurons but in Alzheimer's or Parkinson's you may not be treating the underlying cause, that is the loss of neurons. But if you are replacing the ones that are being lost you may be able to reach a steady state and lessen the impact of the disease for decades."

The director of the Monash Centre for Early Human Development, Martin Pera, said the study was important because it provided the first precise identification and isolation of the adult neural stem cells. However, he said, ES cells provided more applications because they could be grown indefinitely in large numbers, were capable of differentiating into many types of adult cells and developing into tissue that functioned exactly as normal cells.

-- (moreinterpretation@ugly.com), August 16, 2001

Answers

Multipotent stem cells found in adult tissue have potential benefits and drawbacks as well. Although scientists are finding that some types of multipotent adult stem cells can "change course" and develop into other types of cells -- such as a blood stem cell switching to a skin stem cell -- there are "some significant limitations" to what they may do. The paper adds that adult stem cells are "present only in minute quantities, are difficult to isolate and purify and their numbers may decrease with age" (NIH, "Stem Cell Primer," May 2000).

-- Cherri (jessam6@home.com), August 16, 2001.

Your points are taken, but the facts remain that embryonic stem cell harvesting will remain controversial, as it should. Else we become further immunized to a lowering of our ethical boundaries in the pursuit of scientific research. The leap to harvesting the organs of prisoners or other undesirables is not that far off.

-- libs are idiots (moreinterpretation@ugly.com), August 16, 2001.

Libs, I agree with you completly. I had noticed the slow integration of the concept of stem cell research, cloning, genetic research and simular concepts into media over the past 5 years or so. I remember a time when cloning was considered taboo world-wide. it is like we were exposed to the different ideas slowly, until the seemed to be a normal part of our culture.

Being a life long science fiction reader, I had been exposed to ideas and scenerios that that we should never allow to happen. Clones with minimal brain function grown for spare body parts, experiments in genetic manipulation resulting in the birth of babies of inhuman forms. The idea of one human being being sacrificed for the sake of another is immoral. I cannot undestand how they will be able to prevent the harvesting of stem cells from future fertalized eggs. But then itisn't being banned, only government funding for it, which will allow it to continue. I'm afraid we have reached a point were many things will be attempted and done which we will end up regretting.

-- Cherri (jessam6@home.com), August 17, 2001.