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Friday, 6 November, 1998, 17:38 GMT
'Revolution in a dish'
The dishes may not look much, but they have caused huge excitement across the scientific world. Inside them are human embryonic stem cells - the "parent" cells that have the potential to become any other cell in the body. Blood, bone, muscle and nerve cells - they all start with the cells in those small dishes. Being able to isolate and maintain these stem cells has taken years of research and has been dubbed "the biggest thing since Dolly the Sheep". BBC News Online looks at what the fuss is all about:
What have the scientists actually done?
The different teams have done it by different routes but the end result is the same. They've managed to find and maintain in the lab the cells that are the starting point for all the tissues in the body. We each have about 100 million, million cells in our bodies but they have special functions - a cell in the gut lining is different from a neurone in your brain. What the scientists have done is isolate the crucial few cells, from the earliest stages of human development, that have yet to follow the special paths that make up every part of our bodies.
But I thought we'd found stem cells before?
We have, but the trick is maintaining these cells in the lab, keeping them alive, proliferating and in that master state before they've started to follow those special paths. "We're the first ones to show that you can culture these cells for a prolonged period of time," says James Thomson, one of the scientists involved. "That's not been previously accomplished in humans before. Since it's now possible, it opens up the possibility for a lot of therapeutic applications in the future."
So what's the next step?
Simply getting enough of these cells will be one of the first tasks. Before we can even think of new medical treatments, the scientists will want to improve their techniques for culturing the cells. They also have to discover what makes a stem cell turn into a nerve cell or a bone cell, a process known as differentiation. And then work out how to turn that switch on to grow them in the laboratory. Currently, the US teams can only stand back and watch as their cultured stem cells differentiate into random, mixed populations of different cell types.
Assuming all this is possible, what can we do?
In theory, we could replace faulty cells in the body with disease-free cells "manufactured" from our cultured stem cells. There are a variety of human diseases that are caused by the death or dysfunction of just one or a few cells. Consider juvenile-onset diabetes in which a particular cell in the pancreas dies or in Leukaemia where a specific blood cell become malignant. "Because the cells we have derived have the potential to form any of these cells in tissue culture," says James Thomson, "they offer potential source of these particular differentiated cells, and a potential source of transplantation to treat these diseases." Remember that - unlike skin cells - many cells do not divide and replace themselves. When nerve cells and heart cells die, that's it - they've gone. This technology gives us the potential to replace failed tissues. Hence the exciting list of possible applications: heart disease, spinal cord injuries, Parkinson's disease, etc.
Which cells are likely to be the first candidates for replacement?
James Thomson thinks blood cells will be the first targets because of the knowledge already gained doing parallel work on mouse stem cells. They would be used in bone marrow transplants in leukaemia cases. But more immediately, these embryonic stem cells will most likely find a use in the pharmaceutical industry. By using pure samples of specific differentiated cell types, the drug companies could quickly test thousands of different chemical compounds to find the next wonder pill.
Yes, this will have to be overcome but it's conceivable that the problem might not arise because the cells transplanted would be your own. Dr Austin Smith, Director of Genome Research in Edinburgh believes this is the way forward. "Ultimately for every individual, probably early in their childhood, a sample of tissue can be taken," he says. "And this could be used to establish a stem cell culture. And that will be frozen down and available throughout their life. If they have any kind of illness or injury, their own cells will be there, to be grown up and produce the particular kind of cells to treat their disease."
We're going to face a lot of difficult ethical questions aren't we?
They've already here. One of the research teams involved in the breakthrough used embryos no longer required by couples in a in-vitro fertility programme. The other used some aborted foetal tissue. The authorities approved both approaches and both have been condemned by anti-abortion groups.
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