Joseph
Bonventre, MD, PhD,
Chronic Kidney Disease (CKD) affects 26
million people in the
Theodore I.
Steinman, MD,
The mortality rate for patients with
end-stage renal disease is around 22 % per year. At the moment, the only way to treat the
disease is with dialysis, usually three times a week for four hours at a time,
and dialysis machines are far from perfect.
Their efficiency is only around 10 % of that of a functioning kidney,
and they lead to a variety of complications both during and between dialysis
treatments. Being on a dialysis machine
activates cytokines in the body, and these cytokines cause inflammation that
can destroy residual kidney function in the patient. Dialysis treatments also pose risks
associated with infection, bleeding, clotting, and cardiac disease. On top of everything else, long and frequent
dialysis sessions severely reduce a patient’s quality of life. Designing a wearable artificial kidney would
make dialysis a more effective therapy.
Nanotechnology offers enticing
possibilities in this area. Dialysis
membranes used today are thick and permit a low flux of particles to pass
through them. Thinner “nanomembranes”
would be more permeable. These new
membranes could also be carefully engineered to contain highly selective pores,
instead of the almost randomly sized pores present in membranes used today. Particular pores, for example, could be designed
to help filter middle-sized molecules from the blood. Some middle-sized molecules, such as
beta-microglobulin, can cause debilitating health problems when they accumulate
in the body, and traditional dialysis machines do a poor job of filtering these
molecules from the blood. Creating a
library of engineered pores would allow nephrologists to come up with
customized dialysis regimens tailored to their individual patients. Incorporating nanomembranes into a wearable
device would allow patients to receive almost continuous dialysis, which would
eliminate damaging fluctuations in the blood’s urea concentration. Before wearable devices enter clinical use,
however, the challenge of safely accessing the blood must be overcome.
Greg Erman,
MBA, former president and CEO of Renalworks Medical Corporation
There exists a clinical need for a device
that will deliver continuous dialysis therapy to stabilize the roller-coaster
hemodynamics experienced by most patients receiving dialysis three times a
week. From a venture capital
perspective, investing in the development of a wearable kidney has both
advantages and disadvantages. If an
artificial kidney were ever brought to market, it could potentially be very
lucrative, for per capita spending on patients with end-stage renal disease is
enormous. The extremely high costs
currently associated with dialysis therapy would presumably encourage dialysis
providers to adopt new technology.
Investors also see reasons, however, to be wary of backing research to
develop this technology. Continuous
dialysis devices, even more so that today’s machines, would involve risks
associated with blood access, such as bleeding, clotting, and infection. Another reason for investors to pause before
funding research is the fact that many patients receiving dialysis today seem
resigned to their condition and unwilling to embrace new therapies. There is also a widespread perception among
investors that nephrologists are not aggressive technology adopters. Finally, daily or continuous dialysis
therapies are not currently reimbursed.
Thus, although continuous dialysis machines could result in enormous
quality of life increases for patients, investors will not back product
development until researchers have independently shown the devices to be safe
and effective.
View this video: Greg Erman
Jeffrey
Borenstein, PhD, Drapers Labs
To create an artificial kidney,
researchers are seeking to combine engineered structures with engineered
tissue. Current designs being
investigated involve microfluidic networks in which each tube is coated with
endothelial tissue. These networks are
designed to have smooth flow patterns, and the endothelial tissue helps reduce
the chance of clot formation. In a
device being developed by Jeffrey Borenstein of Draper Labs, blood is filtered
through a thin, engineered membrane in order to improve the clearance of
middle-sized molecules relative to clearance rates obtained by current dialysis
machines. Modeling blood flow and
metabolite diffusion in the blood has been and will continue to be very
important to the project.