Issue (Who cares and why?)
It's bad news, says your doctor. Your liver is failing. So he extracts stem cells from your bone marrow and injects them into a sheep fetus while it is still in the womb. When the sheep is born, much of the animal's liver will consist of your own cells - ready to be harvested and given back to you. This dream therapy is still years off, if it happens at all, but the first steps have already been taken by a team led at the University of Nevada, Reno.
What has been done?
UNR researchers original goal was to see if unborn children with genetic defects could be treated by injecting healthy stem cells into the fetus. This is still his main aim, but while doing animal experiments he realized the technique could also be used to grow "humanized" organs. Researchers first showed that when human stem cells extracted from bone marrow are injected into sheep fetuses, the human cells become part of the heart, skin, muscle, fat and other tissues. But the numbers of human cells were very low. In recent months, the team has now managed to produce sheep-human chimeras with a surprisingly high proportion of human cells in some organs. With recent results showing between 7 and 15 per cent of all the cells in the sheep's livers are human. In some special cases the human liver cells cluster together to form functional, fully human liver units, which could be transplanted whole as auxiliary organs.
Impact
If perfected, the technique could overcome some of the big stumbling blocks facing researchers who want to make tissues and organs for implants. It might yield significant quantities of just about any kind of cell or tissue, for instance, with no need to fiddle about with different culture conditions or growth factors. Instead, the host animal's own developmental program guides the injected human stem cells into their final roles. "We take advantage of the growing nature of the fetus," Dr. Esmail Zanjani says.
It would also allow doctors to obtain immune-compatible cells without having to create human embryos by therapeutic cloning. Human cells could be separated from the animal ones simply by modifying existing cell-sorting machines. Providing the method really does produce normal human cells, they would not be rejected. And any stray animal cells would be killed off by the recipient's immune system.
Contact
Esmail Zanjani
Animal Biotechnology/ MS202
University of Nevada, Reno
Reno, NV 89557-0104
Zanjani@nevada.unr.edu