It might gratify scientists if they can someday grow an entire organ from scratch, but a part-biologic, part-synthetic kidney looks pretty impressive in light of indications that it already has saved some very ill patients.
In early clinical trials at the University of Michigan, a bioartificial kidney has been used in a handful of intensive-care patients who were deemed very likely to die because kidneys and other organs were failing. All but one recovered with normal kidney function.
"It's just been amazing to us," said Dr. H. David Humes, a professor at the university's medical school. "This is beyond what we'd predicted."
He spoke yesterday about the development and testing of the so-called Renal Assist Device on the final day of the Engineering Tissue Growth International Conference at the Westin Convention Center, Downtown.
Acute renal failure can occur as a result of overwhelming infection, trauma, poisonings and other conditions. Kidney function declines rapidly, in a matter of hours or days, leading to reduced urine production and imbalanced fluid and salt levels in the body.
More than half of all acute renal failure patients die. An intensive care patient who develops the problem is six times more likely to die than one who doesn't, regardless of the use of conventional dialysis machines, Humes said.
The Renal Assist Device is an external machine through which the patient's blood is circulated. The blood first goes through a standard dialysis filter, but then passes through a cartridge that is lined with human kidney cells before returning to the patient.
These healthy kidney cells were isolated from donor organs that proved unsuitable for transplantation. A special membrane covers the cells to prevent contact with immune components of the patient's blood that might attack them.
Unlike conventional dialysis, the bioartificial kidney is able to perform a kidney's hormonal and metabolic functions.
Five patients who were in the intensive care unit with multiple organ failure due to conditions such as septic shock were treated with the assist device for about 24 hours. Before and afterward, they had standard dialysis.
Most of them had less than one chance in 10 of surviving with conventional treatment, Humes noted.
During the time the device was used, the patients required fewer blood pressure medications and less oxygen support, and produced more urine. Those effects wore off within a few hours of being taken off the device.
But even that brief respite appeared to make a difference. The only patient who did not recover was found to have an extensive fungal infection on autopsy that had little likelihood of cure.
Humes suspects that the bioartificial organ was helpful in these patients because the kidney cells produced reactions that helped cope with widespread inflammation associated with their severe illnesses.
"It's like a forest fire throughout the whole body," he explained. "We view this treatment as almost like a drenching rain for 24 hours. There's still inflammation after the therapy, but it's now controllable."
Humes cautioned that the trial has been designed to rule out toxicity, not to look for benefit. Cleveland Clinic researchers recently joined the trial, and several more patients have to be studied before conclusions can be drawn.
The Michigan researchers are evaluating sites for the next stage of testing, which will require perhaps 60 patients. A Pittsburgh medical center is being considered, Humes added.
The technology could perhaps play a role in chronic renal failure, as well.
