“The question is, How do you turn 100 donated kidneys into 100,000 devices?” says David Humes, an internist at the University of Michigan, in Ann Arbor, and creator of the device. “You have to isolate the cells, expand them, and make sure they haven’t lost any potency in the process.”
Unlike small-molecule drugs or mechanical devices such as pacemakers, cells behave in unpredictable ways. That makes it difficult to develop reliable methods for growing massive quantities of a specific type of cell. Experts say this issue is proving to be a serious hurdle to the development of cell-based treatments. Despite huge demand for replacement organs, few companies have managed to produce tissue-engineered therapies for market. And the problem is likely to grow as more companies attempt to commercialize these therapies.
In the United States, 400,000 people have chronic kidney problems that require weekly dialysis, and 120,000 suffer acute renal failure, in which kidney function is knocked out by toxins or infection. Dialysis extends the lives of these patients, but it’s not a cure: life expectancy for most patients is just five years.
Traditional dialysis filters and discards metabolic waste from the blood, and then returns cleansed blood to the patient. Humes’s artificial kidney, also known as a renal assist device, adds an extra step to this process, passing blood and filtrate through a cartridge of human kidney cells. Humes theorizes that these cells perform some of the kidney’s noncleansing functions, such as regulating inflammation and metabolic processes, by secreting crucial chemicals into the blood.
To make bioartificial kidneys, scientists grow cells harvested from donor kidneys not suitable for transplant and then insert them into a specially developed filter tube. Because the finished product contains live cells, it is treated like an organ for transplant, flown to the receiving hospital by helicopter in a temperature-controlled case. Humes founded a company, now known as RenaMed, to commercialize the device, which has not yet been approved by the Food and Drug Administration.
Early clinical trials of the device show that it can dramatically improve the health of patients with acute renal failure. According to the results of a trial released last year, patients treated with the device showed a 70 percent improved survival rate 28 days after treatment. (Scientists at RenaMed are currently analyzing interim results from a subsequent trial.)