Bioengineered veins give hope to kidney disease patients on dialysis

As blood travels around your body, it helps your body get around. Blood is essential for delivering oxygen and nutrients to all the cells in your body and for removing waste products made by these cells. Your body contains approximately 1.5 gallons of blood, which translates to around 7% of your body weight. In order for all this blood to do its job, it needs to be constantly cleaned of waste and extra fluids.

Your kidneys are your blood’s best friend. They act as natural filters that remove those cellular waste products and extra fluid from the blood and pass them off to the bladder, where they are disposed of through urine. Kidneys have the important job of maintaining the proper balance of fluids, electrolytes and chemicals in the blood. They are also involved in other essential biological processes such as regulating blood pressure, making new blood cells, and maintaining healthy bones. It’s a big problem when your kidneys stop working. Without this built-in filtration system, toxic byproducts build up in your blood and cause a multitude of not fun symptoms.

Hemodialysis acts as an artificial kidney to filter the blood of kidney disease patients. (wikipedia)

Hemodialysis acts as an artificial kidney to filter the blood of kidney disease patients. (wikipedia)

More than half a million Americans suffering from kidney dysfunction or failure are being treated by hemodialysis. This process involves connecting a patient to a machine that acts as an artificial kidney. “Old blood” is pumped into the machine from a plastic tube, also known as a shunt, that’s inserted into the patient’s vein. The blood is then passed through a dialyzer which filters out the waste products and extra fluid and allows clean blood to pass through and be put back into the patient (see image).

While hemodialysis is successful at extending the lifespan of kidney disease patients, serious complications can arise from this treatment including uncontrolled changes in blood pressure, bone disease, and anemia. Another common problem occurs with the shunt that’s inserted into a patient’s vein. Shunts can cause infection, blood clots, and can also be rejected by a patient’s immune system. As a result, patients have to get new shunts implanted every year. This is not always feasible for older patients whose veins cannot hold up to this invasive procedure.

A tubular alternative for better hemodialysis

A North Carolina company called Humacyte is trying to improve current hemodialysis technology by engineering human acellular vessels (HAVs) (meaning that the vessels don’t have any cells) that can be transplanted into patients and develop into a human version of a shunt. Sounds complicated, but it’s not really!

First, scientists take muscle cells from human organ donors and coax these cells to grow into tube-like structures. During this process, the cells secrete a compound called cellulose – a component of the extracellular matrix – which forms a biological scaffold that maintains the structure of the cells.

Next, the scientists chemically wash away the muscle cells, leaving an intact scaffold with a hole the diameter of your pinky finger. These scaffolds are then placed under the skin of patients on dialysis. Once transplanted, a patient’s own stem cells migrate to the empty scaffold, set up shop and create a new vein with a wide enough hole that can be used for hemodialysis.

Humacyte’s Chief Medical Officer, Jeff Lawson, explained it an interview with KQED Science:

Jeff Lawson, Humacyte

Jeff Lawson, Humacyte

“This scaffold, once implanted, uniquely becomes repopulated with their own stem cells. That then turns back into something that looks like a vascular cell. And it now transitions over the period of a few months into something that’s indistinguishable from your own tissue. One of the holy grails in vascular surgery is to come up with a prosthetic artificial graft that has the same properties as the patient’s own blood vessels.”

The great news about this promising technology is that Humacyte is testing it in a Phase III clinical trial – the final stage before a drug or treatment is approved by the US Food and Drug Administration (FDA). In a Phase III trial, the treatment has already proven to be safe and shown some effectiveness (in a Phase II trial) and is now being tested in a larger group of patients to hopefully confirm these findings.

In July, CIRM invested $10 million in Humacyte’s Phase III trial in hopes that this technology will improve the lives and health of dialysis patients. Randy Mills, the President and CEO of CIRM, views kidney failure as an unmet medical need that could benefit from a stem cell related treatment:

“This approach has the potential to significantly improve our ability to care for people with kidney disease. Being able to reduce infections and clotting problems, and increase the consistency of care hemodialysis patients get, would meaningfully impact the quality of their lives.”

A patient’s story and CIRM’s efforts to fund clinical trials

Raymund Ramirez

Raymond Ramirez (KQED Science)

Yesterday, David Gorn from KQED Science published a nice piece about Humacyte’s stem cell derived technology and featured the story of a kidney failure patient, Raymond Ramirez. Raymond’s story is very emotional. He is a Vietnam war veteran that has experienced a gauntlet of maladies including bladder cancer and blindness in his right eye. On top of that, his kidneys aren’t functioning well and he is unable to continue his dialysis treatments because his veins aren’t holding up.

Raymond was the first patient to be treated in Humacyte’s Phase III trial. You can read more about his story here.

Gorn also highlighted CIRM’s recent efforts to fund promising stem cell projects that are further along in development and ready for clinical trials in patients. He ended with a quote from UC San Diego’s director of stem cell research, Larry Goldstein, on how important it is for our agency to continue funding stem cell clinical trials.

Larry Goldstein

Larry Goldstein

“Ten years ago I don’t think there were that many [stem cell] projects that were really ready for clinical trials. The field itself has developed projects that are at clinical stage. If the agency [CIRM] keeps pumping out these types of clinical results, California voters may soon see another ballot measure to keep it going.”

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