Patients may be able to grow new kidneys By Nigel Hawkes  23 December 2002

Kidney patients may one day be able to grow new organs and avoid the often fruitless wait for a donor organ, experiments suggest

            Scientists in Israel grew tiny copies of human and pig kidneys by transplanting stem cells into mice.

            The cells developed into mouse-size kidneys, with normal blood circulation and urine production.  The results suggest that by transplanting cells at the right stage of development – seven to eight weeks in human beings and four weeks in pigs – it may be possible to create new kidneys inside a patient.

            Professor Yair Reisner, of the Weizmann Institute of Science, worked with colleagues to take human and pig stem cells, “kidney precursors” – cells that have already begun developing into kidneys – and found that both grew into perfect kidneys.

            The mice in the experiments lacked immune systems, which means that they could not recognise the transplanted as foreign.  It is uncertain how easy it would be to reproduce that in human patients.

            The stem cells came from embryonic tissue which, in human terms, would raise ethical objections because it would mean using foetal tissue.

            An alternative, suggested by the team in Nature Medicine, would be to use cells from a pig, whose organs are roughly the same size as human organs.

            The study was designed to establish the optimum time during embryonic development at which the stem cells have the best chance to form well functioning kidneys, with the lowest risk of immune rejection.  If taken too early, the cells could include non-kidney structures such as bone, cartilage and muscle.  If taken later, the risk of rejection by the immune system is greater.

            To test how effective this scheme might be, the scientists injected human immune system killer cells, called lymphocytes, into the mice that had been given human kidney tissue.  They found that as long as the tissue had been transplanted within the right time range, the lymphocytes did not attack the new kidneys.

            They concluded that as long as the cells were at the optimum stage of development, the patient should require no more immunosuppressive drugs than recipients of normal kidney transplants today.

            The team said the research was in a preclinical study stage, but that if all went well, a treatment could follow within a few years.

THE TIMES (London)