Scientists grow tiny human kidney in mouse   December 23rd, 2002

Scientists have grown a miniature human kidney inside a mouse using a technique that could one day mean an end to organ transplants.

Although the kidney was tiny, it was functional, suggesting that patients suffering from organ failure might be able to grow replacements.

In a paper published yesterday in Nature Medicine, an Israeli team of scientists reveal how they grew organs from kidney precursor cells stem cells that are destined to become kidney cells.

 The cells were taken from human and pig fetuses and transplanted into mice where they grew into perfect kidneys, the size of mice kidneys.

A spokesman for the team at the Weizmann Institute of Science in Rehovot said: “The miniature human and pig kidneys were functional, producing urine.

“In addition blood supply within the kidney was provided by host blood vessels as opposed to donor blood vessels, greatly lowering the risk of rejection.”

The team, led by Professor Yair Reisner, found that the risks of rejection were lowest if the human cells were transplanted from a human fetus at 7-8 weeks and a pig fetus at 4 weeks. 

If cells are removed any earlier, the kidneys grow erratically and include muscle, bone and cartilage cells.  Any later and the risk of rejection is too late.

To check how the human immune system might react to the new kidneys, the researchers grew the organs and mice with no immune system at all and injected human lymphocytes, or white blood cells.

As long as the kidney stem cells were transplanted at the right time the lymphocytes did not attack the new pig or human kidneys.  The study is now in the pre-clinical stage and if all goes well might be tested in people within the next few years.

More than 5,000 people are waiting for kidney transplants in Britain.  The shortage of donors is so severe that the Department of Health is actively encouraging live donors.

The crisis has prompted scientists to investigate whether patients could grow replacement kidneys from stem cells – the unspecialized “parent” cells which have yet to differentiate into full grown tissue or body parts.

 Researchers are also looking into xenotransplantation, or kidney transplants from genetically modified pigs.

A spokesman for the Britain’s National Kidney Research Fund said: “any scientific advance that will help relieve the chronic shortage of organs can only go towards benefiting patients.  If they have been able to do this with stem cells it is terrific news, although of course these are still very early days.”

 Because of the ethical issues involved in using fetal stem cells, it is likely that pig stem cells will be more acceptable to doctors and patients. Pig stem cell transplants are thought unlikely to trigger the massive immune rejection found with animal whole organ transplants.

Kidneys filter toxins from the blood and excrete them in urine.  Each day, the kidneys filter around 200 liters of blood – or the entire blood supply 7 or 8 times.  Common causes of kidney failure include diabetes, mellitus, uncontrolled high blood pressure, drug abuse, cysts, kidney stones and systemic lupus erythematosus.

Telegraph UK