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Working kidney grown in mouse

Complete working kidneys have been grown in mice using stem cells derived from human and pig fetuses. If the feat can be repeated in humans, it will allow doctors to replace damaged organs without the need for a donor.

NewScientist.com news service

The Israeli team, who used three-month-old mice as recipients for the growing kidneys, were able to avoid immune rejection by using embryonic stem cells. The developing kidney takes time to acquire ‘antigen presenting cells’ which are recognised by the host immune system as foreign.

Embryonic stem cells are also able to adapt to their host, reducing the chance that they will be rejected later in development, says Camillo Ricordi, University of Miami, who works on transplanting islet cells into the pancreas to cure type I diabetes.

"Our data pinpoint a window … that may be optimal for transplantation in humans," say the researchers in their paper in Nature Medicine. If the cells are too young, they do not develop into all the necessary cell types. But if taken too late, the developing kidney will be rejected.

The kidneys functioned well enough to produce dilute urine. But the organs did not connect up with the host’s excretory system. Instead, the researchers, led by Yair Reisner at the Weizmann Institute of Science in Rehovot, Israel, connected a catheter directly into the developing organ. If the technique were used on patients, surgery would be required to connect up the developing kidney.

Safety questions

Reisner’s team hopes that if the technique can be applied to humans it will mean an end to the years of waiting that patients often have to undergo for a donor. Over 50,000 people are on the waiting list for a kidney transplant in the US and more than 2000 people die annually waiting for a match.

However, growing a kidney from pig cells transplanted into a human body will raise safety questions. There are fears that such xenotransplantation could allow porcine endogenous retroviruses (PERVs), which are present in the pig genome, to jump to a human host.

"That is always a concern," says Ricordi. "But more and more data support the fact that it is not a possibility." Hundreds of patients have been given pig islet cells, but none have shown signs of the virus.

Using human embryonic stem cells would avoid the risk of PERVs but involves the destruction of human embryos, which is ethically unacceptable to some.

Journal reference: Nature Medicine (DOI:10.1038/nm812)

http://www.newscientist.com/news/news.jsp?id=ns99993216

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