Key Component of Bio-Artificial Kidney Moves Concept Closer to Reality: Clinical Trials May Begin Soon

Researchers at the University of Michigan are developing a bio-artificial kidney that uses living kidney cells to duplicate nearly all the functions of a healthy organ. While still in the experimental stage, the bio-artificial kidney could one day provide life-saving treatment for thousands of people with serious kidney disease.

H. David Humes

"The kidney is the first human organ for which a mechanical substitute — the kidney dialysis machine — was designed," says H. David Humes, M.D., professor of internal medicine. "We believe it also will be the first organ to have a fully functioning, implantable substitute created with the new science of tissue engineering."

Humes and his U-M research team recently completed animal testing of a key component of the bio-artificial kidney, called a Renal Tubule Assist Device. This device is designed for use outside the body to treat acute kidney failure. Each year in the United States, about 190,000 people face this life-threatening condition, in which the kidneys suddenly shut down as a result of infection or injury. Individuals with acute renal failure typically spend at least 10 days in intensive care attached to a hemofiltration unit, which removes toxic waste products from their blood. Even with advanced medical care, more than 50 percent of these patients die before their kidneys can recover.

In a study published in the May, 1999, issue of Nature — Biotechnology, Humes described how the Renal Tubule Assist Device, connected to a standard hemofiltration unit, helped improve kidney function in laboratory animals with acute renal failure.

According to Humes, kidney cells lining hollow fibers in the device reabsorb vital electrolytes, water and glucose filtered out of blood during hemofiltration, in addition to producing other important molecules. Without these substances, the patient cannot fight off infections and maintain a normal fluid balance. In Humes' study, the device reabsorbed about 50 percent of water and other important molecules, an amount similar to the reabsorption capacity of a normal kidney.

Pending FDA approval, human clinical trials for the Renal Tubule Assist Device in patients with acute kidney failure could begin as early as this fall. Within five years, Humes hopes to develop additional components of the bio-artificial kidney for patients with chronic renal failure — a gradual deterioration of kidney function that currently affects over 300,000 people in the United States, a number growing by about six percent each year.

"Our goal is to bring all the components for a bio-artificial kidney together in one implantable device that will carry out all the functions of a natural kidney," Humes says. "We hope that one day it will be available as a universal-donor organ. This could eliminate the shortage of kidneys for transplant, end long waiting times for transplant organs, and replace dialysis as a treatment for chronic renal failure."

Research on the bio-artificial kidney is being conducted at the Department of Veterans Affairs Ann Arbor Healthcare System. Funding to support the research is provided by the National Institutes of Health, the VA Research Service and Nephros.