Kidney failure affects nearly 1 million people in the US. Without treatment, it results in the retention of excess water and waste products in the body. Renal failure can be reversed by transplanting kidneys from matched donors, but the supply of donated kidneys is insufficient to meet demand, and ∼20% of transplants undergo organ rejection within 5 years. Bioengineered artificial kidneys, created from patients' own cells, that act as permanent transplants could provide an alternative treatment for patients with renal failure. To be viable, the bioengineered organs must recapitulate both the architecture and the functions of the kidney, including perfusion, filtration, secretion, absorption and drainage of urine.

Scientists led by Harald C. Ott (Massachusetts General Hospital, Boston) now report for the first time the successful creation, transplantation and function of artificial kidneys in rats. The bioengineered kidneys could filter blood and produce urine, although they did not work as well as conventional transplants. With further development, however, this approach could help the many patients with renal failure who await organ transplants. “Based on this initial proof of principle, we hope that bioengineered kidneys will someday be able to fully replace kidney function just as donor kidneys do,” Ott told NIH Research Matters. His team is now refining the technique and working to create human-sized organs.

The researchers used a three-part procedure to create the bioengineered kidneys before transplanting them into rats (Nat. Med. doi:10.10938/nm3154; published online 14 April 2013). First, they used detergents to delicately strip the cells from donor organs, leaving behind a protein scaffold that wouldn't be rejected by a recipient's immune system. The decellularization procedure preserves the structure of the organ, maintaining intact the vascular, cortical and medullary architecture; the collecting system; and the ureters in the scaffold.

Next, the kidney scaffolds were repopulated with living epithelial and endothelial cells, and the repopulated scaffolds were then incubated in a whole-organ bioreactor for several days. The artificial kidneys produced rudimentary urine in vitro. Finally, Ott's team transplanted the bioengineered kidneys into recipient rats, where the organs produced urine and successfully filtered and reabsorbed certain molecules. The scientists did not observe any bleeding or thrombosis associated with the transplants.

The next steps in developing this technology for human application are to scale up the procedures to human-sized scaffolds and to isolate, differentiate and expand the required cell types. Ott's group hopes that refining the cell types and culture conditions will improve the function of the bioengineered kidneys.