The Kidney Project is a long-term effort to engineer an implantable artificial kidney to improve the lives of patients with renal failure.
There’s an old saying that one doesn’t miss the water until the well runs dry. When you are feeling well, its easy to forget how lousy you felt when you were sick. Half a million Americans and two million people worldwide feel sick every single day because they have severe kidney disease, and each patient with kidney failure knows he or she will not ever have a day again when they can forget how it feels to be sick.
Our best treatment for kidney failure is a replacement kidney through a medical procedure called transplantation. Kidney transplant recipients lead pretty normal lives other than a daily burden of pills and increased risk of infections and cancers. Transplant kidneys come from altruistic living donors who donate one of their two kidneys to someone with kidney failure, or from deceased donors whose surviving family decides to make a gift of their loved ones kidneys. (For how this all works, visit the United Network for Organ Sharing web site.)
Transplant is limited by scarcity of donor organs. In 2014, there were five times as many people waiting for a kidney as received a kidney transplant. Everyone else either accepts the finality of death or chooses some form of dialysis. Very briefly, dialysis uses a salt water solution to clean the blood of waste products. This can happen inside the body, using peritoneal dialysis, or outside the body, using hemodialysis. These treatments happen somewhere between every day and a few times a week. At best, dialysis replaces a tiny fraction of the function of a healthy kidney. For example, what do you like to eat? Steak? Potato chips? Pizza? Maybe you are a little more health conscious. Fresh tomatoes. Grapes. An orange? A dialysis patient cannot eat any of these these. The dialysis procedure cannot get rid of the wastes until it is time for the dialysis session, and during the time between the meal, the levels of waste products can rise high enough to be dangerous.
A 2010 article in ProPublica, reprinted in part in The Atlantic magazine, described the shortcomings of dialysis as it is prescribed in the United States. Many doctors objected to the article, saying it was not representative of kidney care in the US. Other doctors and patients have begun to see that dialysis is not always the best option.
What can we all do? Every year the number of patients with kidney failure grows larger and larger, and the burden of suffering and the dollar cost of care grow right alongside.
The Solution: an Implantable Artificial Kidney
Dr. William H. Fissell of Vanderbilt University holds a prototype artificial kidney cartridge.
Treating patients with hemodialysis is costing us a fortune and leaving us sick. To answer this need, since 1998 we have worked to create an implantable artificial kidney. Our design is modeled on the body’s own strategy for cleaning the blood.
There are a few features of the kidney that we copy. First, the kidney is a massively parallel structure. Each one of your kidneys has about one million little nephrons all pretty much alike. Remove half a kidney, you have half as many nephrons and half the function. We mimic both the kidney and the microelectronics industry by implementing hundreds of copies of the same plan to achieve the desired level of function. Need more function? Add more units!
Second, each little nephron subunit has two parts that work together: a filtration unit, called the glomerulus, and a processing unit, called the tubule. The filters are the part that are ruined in most kidney diseases, and the cells that make the filters do not grow well in the laboratory. Right now, there’s no good way to grow replacements, although other scientists are pursuing this approach. Instead, we use silicon nanotechnology to make artificial filters instead. The tubule sorts out the substances in the filtrate and decides what to keep and what to discard: how much salt, how much potassium, how much water, and so on. These cells, fortunately, are easy to grow in the laboratory and have even been used in artificial kidneys before.