A new artificial kidney consisting of living kidney cells on a plastic scaffolding restored the major functions of the organ when tested in dogs. If the device, described in the May issue of Nature Biotechnology, can replace failing kidneys in humans, it could save the lives of thousands of patients who suffer sudden kidney failure each year.
More than half the people whose kidneys fail during or after major surgery die, usually within 2 weeks. That's because the standard treatment for kidney failure, pumping the blood through a dialysis machine, only filters out metabolic wastes from the blood, says nephrologist David Humes of the University of Michigan, Ann Arbor. A kidney, in comparison, pumps out hormones such as activated vitamin D that may boost the body's infection fighting abilities and reabsorbs salts and nutrients from the liquid that will become the urine. To create a better kidney replacement, Humes and his colleagues enlisted the real experts--kidney cells themselves.
First, the team extracted primitive kidney cells called renal tubule cells from adult pigs and injected them into plastic tubes. These tubes make up a hemofiltration cartridge, a blood-filtering device already used by a handful of renal failure patients. Cells can collect on the tubes, which have tiny holes to allow dissolved molecules to squeeze through. The cells then join up to form a sheet of tissue, just as they do in a normal kidney. When blood from dogs that had just had their kidneys removed was routed through the device, it filtered the blood more efficiently than a standard dialysis machine. Moreover, devices with cells better maintained blood pH balance and actively secreted the infection-fighting hormones glutathione and activated vitamin D into the animals' blood compared to devices without cells. The group is seeking regulatory approval to begin clinical trials for acute renal failure patients later this year, Humes says. And a variant of the device designed for chronic renal failure is slated for animal trials.
The new device "should provide many more of the normal kidney functions than possible with conventional dialyzers," says biomedical engineer Barry Solomon of Circe Biomedical Inc. in Lexington, Massachusetts, which has produced similar devices to fill in for failing livers. The device also demonstrates the promise of bioartificial organs composed of synthetic material and living tissue, says biomedical engineer Clark Colton of the Massachusetts Institute of Technology. "I think it's a big step forward for the field."