MINIATURE HUMAN KIDNEYS GROWN IN MICE   By JUDY SIEGEL-ITZKOVICH

December 23, 2002 - Researchers at the Weizmann Institute have managed to grow functional miniature human kidneys in a mouse, opening the possibility of creating an unlimited supply for transplants in kidney-disease patients.

Details about the breakthrough appear in Monday's issue of Nature Medicine.

A team headed by Prof. Yair Reisner of the institute's immunology department induced human stem cell tissue to grow into functional kidneys and have accomplished the same with stem cell tissue taken from pigs.

The procedure is in the pre-clinical study phase, said Reisner, but if all goes well, it could be applied in human kidney transplantation within a few years.

As a result, instead of a kidney patient having to search for a donor, one may be able eventually to grow a new kidney for the patient, Reisner said.

Reisner's team, which included scientists from Sheba Hospital at Tel Hashomer and Hebrew University computer scientists and engineers, said they used kidney precursor cells (stem cells destined to become kidney cells) taken at their earliest gestational point. They thus differentiated into functional kidney cells and not into other cell types. The miniature kidneys they produced released dilute urine. The team also showed that the tiny kidneys caused less immune-system resistance in the recipient mice than adult kidney transplants.

In response to the breakthrough, Prof. Michael Friedlaender, of the Hadassah-University Hospital's department of nephrology and chief of its kidney transplant clinic, said that "if  has been done, I can only rejoice for my patients."

"We have longed for the time when we could go to an 'orchard' of kidneys and pluck those we needed, and we seem to be getting closer to that time," Friedlaender said.

He estimated "there are 600 people in Israel waiting for a kidney donation. About half of kidney transplants involve an organ from a live related donor."

There are still kidney failure patients living on dialysis because they are not suited to a transplant because they have other serious chronic diseases, he said. But if there is a greater supply of kidneys thanks to stem cells, many people will be able to live longer and with a higher quality of life.

The Weizmann findings suggest that human or pig fetal tissue might take on the shape and function of a healthy kidney if transplanted into humans as well. The scientists hope that porcine stem cells might thus provide a source for those in need of a kidney.