Kidneys Created in Mice from Stem Cell Tissue

Israeli researchers have induced human and porcine stem cell tissue to grow into functional kidneys in mice. Their work was reported in the December 23, 2002 online issue of Nature Medicine.

Human and porcine kidney precursor cells were transplanted into mice by researchers at the Weizmann Institute (Rehovet, Israel) and both human and porcine tissue grew into perfect kidneys. The miniature kidneys were functional, producing urine. Blood supply was provided by host blood vessels instead of donor blood vessels, greatly lowering the risk of rejection.
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The scientists pinpointed the ideal time during embryonic development in which the stem cells have the best chance to form well-functioning kidneys with minimal risk for immune rejection. Their research suggests that seven to eight week (human) and four- week (porcine) tissue offer an optimal window for transplantation. If taken earlier, the tissues will develop disorganized tissue that would include non-kidney structures such as one and cartilage. If taken later, the risk of immune rejection is substantial. Within this optimal time range, the tissue does not contain certain cells that the body recognizes as foreign. These cells reach a developing kidney only after 10 weeks.

After growing the human and porcine kidney tissue in mice, the researchers injected human lymphocytes into immunodeficient mice to see how these fighter cells might react to the kidney tissue. They found that as long as the kidney precursors were transplanted within the right time range, the lymphocytes did not attack the new kidneys. This suggests that human or porcine fetal tissue might take on the shape and function of a healthy kidney if transplanted into humans. Pig tissue is not expected to cause hyperacute rejection, as shown in recent research. Thus, porcine stem cells could provide a ubiquitous source for patients in need of a kidney. In the United States alone, more than 50,000 people are on the waiting list for a kidney transplant.



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