An artificial kidney that is able to mimic the regulatory functions of the organ could provide an alternative for the thousands of kidney failure patients waiting for an organ transplant, claim researchers.

The invention has, so far, been tested on 10 patients with kidney failure, report Professor David Humes, from the University of Michigan Medical School, and colleagues.

Importantly, the bioartificial kidney reclaims crucial plasma components in the same way as a functioning kidney, unlike kidney dialysis, which removes all such vital particles.

Key to the device's function is a renal tubule assist device (RAD) that consists of hollow fibres lined with renal proximal tubule cells generated from human stem cells.

Once the cell cartridge of the artificial kidney has filtered the blood like a dialysis machine, cells in the RAD reclaim electrolytes, salt, glucose and water molecules from the plasma. Just like cells in the kidney, the tubule cells also control the production of cytokines – molecules vital for the immune system's fight against infection.

The small trial involved 10 patients with acute renal failure who faced an average 86% chance of dying and suffered from other illnesses, including sepsis, multiple organ failure, acute respiratory distress syndrome and postoperative complications.

Each patient underwent up to 24 hours of treatment with the bioartificial kidney, although some had to be taken off the therapy earlier due to hypoglycaemia, low platelet counts or factors due to other illnesses.

Six of the 10 survived more than 30 days after the treatment, report the investigators in the journal Kidney International.

"These results showed this type of human adult progenitor or stem cell is well tolerated by patients with acute renal failure, and resulted in some improvement of the patients' clinical conditions," commented Professor Humes.

"It's a small study, but it was compelling enough for us and the Food and Drug Administration to go forward with a full phase II study."

A randomised, controlled phase II trial into the bioartificial kidney is now underway at six centres, says the team. They are also working on making the device smaller so that it could be implanted into a patient with kidney failure.

A spokesman for the National Kidney Research Fund commented: "We are very encouraged that scientists are constantly looking for ways to overcome the organ shortage problem, as there are currently some 6400 people needing a kidney transplant in the UK."

However, he added that the bioartificial kidney "is premature and a long way from being a readily available replacement to human donor organs for transplantation".

Useful Links
Kidney International
University of Michigan Medical School
The National Kidney Research Fund