A bioengineered kidney that shows renal function and produces urine both outside of a body and after transplantation in a rat, is reported online this week in Nature Medicine. Although the functional studies have only been shown in rats, the findings suggest a promising approach for bioengineering kidneys using patient-derived cells to circumvent rejection.

Even though hemodialysis-the use of a machine to filter wastes and fluids from the body-has increased survival of individuals with advanced kidney disease, organ transplantation remains the only curable treatment. However, there are not sufficient donor kidneys and a considerable number of transplant rejections or even post-operative deaths still occur.

Harald Ott and his colleagues remove the cellular components of cadaveric rat, porcine and human kidneys to create renal scaffolds that hold intact renal structures, waste collecting system and ureters, which are important for filtration, secretion and reabsorption of body liquids. After adding back a combination of rat kidney and blood vessel cells to a rat renal scaffold, the authors grew the tissue in a whole-organ bioreactor; the regenerated kidneys produce urine. These bioengineered kidneys also have excretory function without signs of bleeding or clot formation after transplantation in rats.