The future of medicine: a load of old cobblers

Family jewels promise stem cell breakthrough

A US company has claimed it has produced human stem cells from testes. California firm PrimeGen Biotech says its technology has been used to coax brain, heart and bone cells from a type of cell in gonads called the germ line.

The germ line is the group of cells that divide to produce the sperm and eggs. PrimeGen says it can reprogram the testes cells so, instead of just being able to make the male gamete, they take on the characteristic pluripotency of stem cells. This means they can become any tissue in the body - from nerves to hair follicles.

The news trumps a widely publicised Nature report from a German group last week of similar technology in mice. The PrimeGen work has yet to pass through the peer-review and scrutiny process, however.

PrimeGen CEO Thomas C K Yuen puffed: "[This is] one of the most significant breakthroughs in regenerative medicine. These cells advance the potential for cellular replacement for everyone."

Soft target

Theoretically, the germ-line represents an obvious quarry of stem cells in terms of adult tissues. The DNA in these cells is the stuff that has the potential to be physically passed on to the next generation.

Because of this, the germ line has evolved such that its DNA doesn't suffer the same ravages of aging that, say, kidney cells do. To borrow the 'Selfish Gene' way of thinking, our DNA isn't 'stupid' – it looks after its own.

For stem cell therapies this is a boon; the DNA you can get from a germ line cell is of the same quality as that you can get from an embryo. This is an advantage over other efforts to find 'ethical stem cell' sources in other parts of adult bodies.

If it's validated the announcement could be great news for men suffering from an array of diseases, such as Alzheimer's or diabetes.

They just need to be the owner at least one testicle - the vital point is that the stem cells produced from a germ line will be genetically identical to their owner.

This is the key to using stem cells in therapies, and something of a Holy Grail in the field.

The same prize drove disgraced Hwang Woo-Suk to claim he'd been able to take adult DNA from anywhere in the body and inject it into empty eggs to get stem cells from the resulting embryo.

In at least one way the PrimeGen announcement is more exciting, because it doesn't carry the ethical baggage of using embryos.

Women: they lack balls

For women the situation is more complicated. The male germ line remains active throughout life – the age of the father, in genetic terms, is more or less irrelevant to the development of the child. Women are born with all the eggs they'll ever need, though, which age over time. That's the fundamental reason why older mothers are more likely to give birth to children with Down's syndrome.

The germ line has already done its turn while the woman was a foetus. It was long thought it wasn't present at all in adult women's ovaries. Recent studies have offered a glimmer of hope, though. New eggs have been shown to be generated in mice, so the prospect of PrimeGen's reprogramming technology working for female patients is also there.

'Breakthrough' is an oft-used hyperbole in science stories. In this case it could well be deserved, but the proof will be in the injecting, when PrimeGen's testes-derived stem cells are soon used to treat heart conditions. ®

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