Scientists use living cells to create `bionic' kidney

SCIENTISTS HAVE come a step closer to creating the first "bionic" organs by growing living kidney cells inside synthetic tubes to filter the blood of laboratory animals suffering from renal failure.

It is the first artificial kidney to use living tissue to mimic the functions of real organs and its development could alleviate the chronic shortage of kidneys for transplant operations. Scientists grew the cells taken from a pig's kidney on the inside surfaces of the hollow fibres used in kidney dialysis machines, which filter blood of toxic substances.

The cells stuck to the fibre - which is about as thick as a human hair - and proliferated to form a continuous lining of living material through which the filtered blood flowed. The research team intends to test the device on the first human patients later this year. The experiment demonstrated that the cultured kidney cells secreted vital substances into the filtered blood of the animals. These compounds are lacking when a kidney patient undergoes conventional dialysis treatment, a shortcoming that is thought to increase the risk of severe side-effects.

Medical researchers believe the study marks an important breakthrough in the attempts to find an alternative to kidney dialysis, which fails to save the lives of more than half the patients who need the treatment after suffering from acute renal failure. They also hope to develop the technique further to manufacture fully functioning kidneys for transplant operations by growing living cells on a man-made "scaffold" designed to hold together the tissues. David Humes, who led the team at the University of Michigan, has applied to the US Food and Drugs Administration for clinical trials in humans, which are expected to start this autumn. "The project falls into a larger framework of research aimed at making bio- artificial kidneys that could be implanted into patients," said Dan Cutler, a spokesman for Dr Humes' laboratory.

The team reports in next month's issue of the journal Nature Biotechnology that the cells were able to secrete vital substances back into the blood of a dog suffering from acute renal failure, something that was not possible with conventional kidney dialysis. "What is new and different is that Dr Humes has demonstrated that he can grow these cells and that they can perform the function of releasing metabolites [biological substances] as they would in a natural situation," Mr Cutler said. Although the living kidney cells were grown in a kidney dialysis machine outside the body, the scientists hope to be able to culture them in a kidney-sized artificial organ, which could then be transplanted permanently into a patient with renal failure.

Because the cells were encapsulated inside hollow fibres they were protected against attack from the body's immune defences, making organ rejection less likely. Clark Colton, professor of chemical engineering at the Massachusetts Institute of Technology, said it was an important development.