Spare vessels
Bioengineered Blood Vessels May Help People on Dialysis
The patients did not have immune or other negative reactions to bioengineered blood vessels, writes EurekAlert! (Self-sustaining, bioengineered blood vessels could replace damaged vessels in patients) with reference to Science Translational Medicine (Kirkton et al., Bioengineered human acellular vessels recellularize and evolve into living blood vessels after human implantation).
During clinical trials, these vessels were installed in the hands of dialysis patients and successfully integrated into their circulatory systems. The new blood vessels, which contain the patient's own cells, are designed to be safer and more effective than the currently existing options. Traditional implants consisting of synthetic polymers or donor tissue can cause inflammation or rejection by the immune system.
In the United States alone, hundreds of thousands of people need blood vessel implants for dialysis. These bioengineered vessels can help not only such patients, but also people who have lost blood vessels as a result of tumor removal or injury, says Christopher Breuer, director of the Center for Regenerative Medicine at the National Children's Hospital in Columbus (Ohio), who was not involved in the study.
Heather Pritchard, a biomedical engineer at the medical research company Humacyte in Durham, North Carolina, and colleagues created each blood vessel by seeding a biodegradable polymer tube with vascular cells from a deceased donor. Inside the bioreactor tank, which supplied the vascular cells with nutrients, these cells multiplied and secreted proteins that formed an intercellular network. After eight weeks, the polymer framework collapsed, and the researchers washed the donor cells from the remaining protein tube. Then a vessel about 6 millimeters in size was implanted into the patient, where his own cells gradually migrated into the tube.
"Think of it as a tenant–free apartment building," says Laura Niklason, a biomedical engineer at Yale University. – This is an empty space for [the patient's] cells to occupy it" after implantation of the protein tube.
The team tested the vessels of 60 patients who needed dialysis for kidney disease – a process that involves filtering the patient's blood through a machine. The procedure requires the implantation of a large additional vessel in the arm, so that it serves for bypass blood circulation, feeding blood to the dialysis machine.
The newly designed blood vessels did not cause any significant immune reactions in any of the patients. Tissue samples from 13 participants showed that the vessels matured within one to two years after implantation. The patients' bodies filled the new blood vessel with both smooth muscle cells, which usually make up the walls of blood vessels, and endothelial cells, which cover the inner surfaces of blood vessels. The new vessels were also covered with microvessels, which supplied the implant with oxygen and nutrients.
Researchers are currently testing the effectiveness of bioengineered vessels compared to a synthetic alternative in clinical trials involving hundreds of patients.
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