Nearly 90,000 patients in the United States are waiting for a lifesaving kidney transplant, yet only about 25,000 kidney transplants were performed last year. Thousands die each year while they wait. Others are not suitable transplant candidates.
Half a million people are on dialysis, the only transplant alternative for those with kidney failure. This greatly impacts their work, relationships, and quality of life.
Researchers from The Kidney Project hope to solve this public health crisis with a futuristic approach: an implantable bioartificial kidney. That hope is slowly approaching reality. Early prototypes have been tested successfully in preclinical research and clinical trials could lie ahead.
This news organization spoke with two researchers who came up with the idea: nephrologist William Dr. Fissell, MD, of Vanderbilt University in Nashville, Tenn., and Shuvo Dr. Roy, PhD, a biomedical engineer at the University of California, San Francisco. This interview has been edited for length and clarity.
Question: Could you summarize the clinical problem with chronic kidney disease?
Dr. Fissell: Dialysis treatment, although lifesaving, is incomplete. Healthy kidneys do a variety of things that dialysis cannot provide. Transplant is absolutely the best remedy, but donor organs are vanishingly scarce.
Do you envision your implantable, bioartificial kidney as a bridge to transplantation? Or can it be even more, like a bionic organ, as good as a natural organ and thus better than a transplant?
Dr. Roy: We see it initially as a bridge to transplantation or as a better option than dialysis for those who will never get a transplant. We’re not trying to create the “Six Million Dollar Man.” The goal is to keep patients off dialysis – to deliver some, but probably not all, of the benefits of a kidney transplant in a mass-produced device that anybody can receive.
Dr. Fissell: The technology is aimed at people in stage 5 renal disease, the final stage, when kidneys are failing, and dialysis is the only option to maintain life. We want to make dialysis a thing of the past, put dialysis machines in museums like the iron lung, which was so vital to keeping people alive several decades ago but is mostly obsolete today.
How did you two come up with this idea? How did you get started working together?
Dr. Roy: I had just begun my career as a research biomedical engineer when I met Dr. William Fissell, who was then contemplating a career in nephrology. He opened my eyes to the problems faced by patients affected by kidney failure. Through our discussions, we quickly realized that while we could improve dialysis machines, patients needed and deserved something better – a treatment that improves their health while also allowing them to keep a job, travel readily, and consume food and drink without restrictions. Basically, something that works more like a kidney transplant.
How does the artificial kidney differ from dialysis?
Dr. Fissell: Dialysis is an intermittent stop-and-start treatment. The artificial kidney is continuous, around-the-clock treatment. There are a couple of advantages to that. The first is that you can maintain your body’s fluid balance. In dialysis, you get rid of 2-3 days’ worth of fluid in a couple of hours, and that’s very stressful to the heart and maybe to the brain as well. Second advantage is that patients will be able to eat a normal diet. Some waste products that are byproducts of our nutritional intake are slow to leave the body. So in dialysis, we restrict the diet severely and add medicines to soak up extra phosphorus. With a continuous treatment, you can balance excretion and intake.
The other aspect is that dialysis requires an immense amount of disposables. Hundreds of liters of water per patient per treatment, hundreds of thousands of dialysis cartridges and IV bags every year. The artificial kidney doesn’t need a water supply, disposable sorbent, or cartridges.
How does the artificial kidney work?
Dr. Fissell: Just like a healthy kidney. We have a unit that filters the blood so that red blood cells, white blood cells, platelets, antibodies, albumin – all the good stuff that your body worked hard to synthesize – stays in the blood, but a watery soup of toxins and waste is separated out. In a second unit, called the bioreactor, kidney cells concentrate those wastes and toxins into urine.
Dr. Roy: We used a technology called silicon micro-machining to invent an entirely new membrane that mimics a healthy kidney’s filters. It filters the blood just using the patient’s heart as a pump. No electric motors, no batteries, no wires. This lets us have something that’s completely implanted.
We also developed a cell culture of kidney cells that function in an artificial kidney. Normally, cells in a dish don’t fully adopt the features of a cell in the body. We looked at the literature around 3-D printing of organs. We learned that, in addition to fluid flow, stiff scaffolds, like cell culture dishes, trigger specific signals that keep the cells from functioning. We overcame that by looking at the physical microenvironment of the cells – not the hormones and proteins, but instead the fundamentals of the laboratory environment. For example, most organs are soft, yet plastic lab dishes are hard. By using tools that replicated the softness and fluid flow of a healthy kidney, remarkably, these cells functioned better than on a plastic dish.
Would patients need immunosuppressive or anticoagulation medication?
Dr. Fissell: They wouldn’t need either. The structure and chemistry of the device prevents blood from clotting. And the membranes in the device are a physical barrier between the host immune system and the donor cells, so the body won’t reject the device.
What is the state of the technology now?
Dr. Fissell: We have shown the function of the filters and the function of the cells, both separately and together, in preclinical in vivo testing. What we now need to do is construct clinical-grade devices and complete sterility and biocompatibility testing to initiate a human trial. That’s going to take between $12 million and $15 million in device manufacturing.
So it’s more a matter of money than time until the first clinical trials?
Dr. Roy: Yes, exactly. We don’t like to say that a clinical trial will start by such-and-such year. From the very start of the project, we have been resource limited.
A version of this article first appeared on Medscape.com.