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.

Kidney function

Your kidneys are your blood’s best friend. They act as natural filters, removing cellular waste products and extra fluid from the blood and passing them 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 also support other essential biological processes, such as regulating blood pressure, making new blood cells, and maintaining healthy bones. Kidney failure is a serious problem. Without this built-in filtration system, toxic byproducts build up in your blood and cause a multitude of not fun symptoms.

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 rejection by the 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

Humacyte, a North Carolina company, aims to improve hemodialysis by engineering human acellular vessels, or HAVs, that can be transplanted and form a patient‑specific shunt. It sounds complex, but the process is straightforward.

Scientists start by taking muscle cells from human organ donors and coaxing them to grow into tube‑like structures. As they grow, the cells secrete cellulose, which forms a scaffold that supports the shape.

Next, the scientists wash away the muscle cells, leaving a pinky‑sized hollow scaffold. They implant these scaffolds under the skin of dialysis patients. A patient’s stem cells then migrate into the scaffold, settle in, and build a new vein suitable for hemodialysis.

Humacyte’s Chief Medical Officer, Jeff Lawson, explained the process in an interview with KQED Science.

“This scaffold, once implanted, becomes repopulated with the patient’s stem cells. Those cells form new vascular tissue that becomes indistinguishable from the patient’s own vessels within months. One goal in vascular surgery is creating a graft that behaves like natural blood vessels.”

Humacyte is testing this technology in a Phase III clinical trial, the final step before potential FDA approval. In Phase III, a therapy already shown to be safe and effective in earlier studies is tested in more patients to confirm results.

In July, CIRM invested $10 million in Humacyte’s Phase III trial to improve care for dialysis patients. Randy Mills, CIRM’s President and CEO, sees kidney failure as a major unmet need that may benefit from a stem‑cell‑based approach.

“This approach could greatly improve care for people with kidney disease,” Mills said. “Reducing infections and clotting and improving consistency in dialysis access would have a real impact on patients’ lives.”

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

Yesterday, David Gorn of KQED Science published a piece on Humacyte’s stem‑cell‑derived technology and highlighted kidney failure patient Raymond Ramirez. He is a Vietnam veteran who has faced bladder cancer, vision loss in his right eye, and now kidney failure. His veins no longer support dialysis, so he cannot continue treatment.

Raymond was the first patient treated in Humacyte’s Phase III trial. You can read more about his story at the link above.

Gorn also noted CIRM’s recent efforts to fund stem cell projects ready for clinical testing. He ended with a quote from UC San Diego’s stem cell program director, Larry Goldstein, on the importance of continued clinical funding.ical trials.

“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.”