Six decades ago the physiologist and philosopher, Dr. Homer Smith, once extolled the kidneys in his book From Fish to Philosopher:
Recognizing that we have the kind of blood we have because we have the kind of kidneys we have, we must acknowledge that our kidneys constitute the major foundation of our philosophical freedom. Only because they work the way they do has it become possible for us to have bones, muscles, glands and brains. Superficially, it might be said that the function of the kidney is to make urine; but in a more considered view one can say that the kidneys make the stuff of philosophy itself.
Though perhaps hyperbolic, the kidney is often taken for granted especially compared to organs such as the brain and the heart. The body knows better and, at rest, actually sends about a quarter of cardiac output to the kidneys (rivaling that provided to the brain and greatly surpassing those to other vital organs, the heart itself included). The kidney may be relatively ignored because most of us have two of them and thus live-donor transplants are more readily available than they are for other organs. What is often forgotten, however, is that demand still greatly surpasses supply, which is why we still have thousands of people in end stage renal disease (ESRD) who spend their lives on dialysis.
Within a decade or two, this may no longer be the case. Researchers at UCSF have made strides towards developing an artificial, implantable kidney – essentially a self-contained dialysis unit. We had the opportunity to speak with team leader, Dr. Shuvo Roy, about his team’s work:
Shiv Gaglani, Medgadget: How did you come up with the implantable artificial kidney?
Dr. Shuvo Roy: Dialysis is the primary option for the vast majority of chronic kidney patients. While transplant remains the gold standard, there simply are not enough donor organs available. Unfortunately, dialysis patients experience poor survival and low quality of life. The implantable artificial kidney attempts to deliver on the benefits of transplant – better health, better quality of life – while overcoming the shortage of organs.
Medgadget: Which patient population is it intended for (e.g. ESRD Category, GFR range, inclusion/exclusion criteria)?
Roy: It would be ESRD patients that were on dialysis. Typical GFR for these patients is <15 mL/min). Some exclusion criteria might be patient age – will they be able to survive the surgery?
Medgadget: Do you have an estimate of characteristics such as cost and operational lifetime of the device?
Roy: Too early to nail down costs of the device with high level of confidence, but likely to cost the payer equivalent or less than what is spent on a transplant patient. Operational lifetime can be projected as far as a decade, but it is possible that periodic maintenance will be required via doctor/hospital visits.
Medgadget: What are the key technologies that enabled the creation of this device (e.g. power, computation, biomaterials, miniaturization, etc)?
Roy: Miniaturization of hemofilter and its filtration performance enabled by new high-efficiency membrane technology enabled by semiconductor/silicon fabrication technology – no pump or electrical power needed. Blood compatibility enabled by thin-film polymer coatings that prevent fouling while preventing pore blockage. Cell bioreactor enabled by isolation of renal tubule cells and new techniques for culture/expansion/storage of cells, as well as superior immunoisolation provided by silicon membranes.
Medgadget: Is the artificial kidney capable of performing more than filtration? For example, can it secrete or respond to chemicals, such as the RAAS system? Can it dynamically adjust its filtration rate depending upon body requirements (e.g. sympathetic stimulation results in a decrease in filtration)?
Roy: Yes, it will provide the functions that are associated with the proximal tubule cells: reclaim vital electrolytes, salt, glucose, and water, as well control production of cytokines. The bioreactor of cells will control reabsorption rate, which, in tandem with the hemofilter, will provide some level of feedback control.
Medgadget: Can you describe any preliminary tests of efficacy of this device? Do you expect this to be standard of care, and if so when do you anticipate it reaching its goal?
Roy: A large scale (non-implantable) version of the device was tested on acute renal failure patients with success. This version used commercial-off-the-shelf polymermembrane technology, but it established that a combination of hemofilter and bioreactor could mimic kidney functionality. We have since (successfully) focused on miniaturizing the hemofilter and shown superior filtration parameters relative to conventional polymer membranes, and resolved cell sourcing for the bioreactor and confirmed their functional performance. To date tests have been done in pigs, sheep, and rodents. First clinical trials are planned for 2017.
To learn more, check out the video below: