Researchers at the University of Pittsburgh School of Medicine have developed artificial blood vessels, which may have significant implications for the treatment of heart and kidney disorders.
The vessels, made from muscle-derived stem cells (MDSCs) and a biodegradable polymer, exhibit extensive remodelling, and remain free of blockages when grafted into rats.
The saphenous vein taken from a patient's leg is used for coronary artery bypass grafting, even though a significant percentage of vein grafts eventually fail. Arterial grafts are the preferred conduits because they are less prone to becoming obstructed.
However, they are in very limited supply, as many patients require multiple grafts, which is why the researchers have been looking for the ideal small-caliber arterial substitute for re-vascularization procedures.
Led by Dr. David A. Vorp, Associate Professor of Surgery and Bioengineering, the researchers developed vascular graft by "bulk seeding" MDSCs inside a biodegradable porous, tubular polyester urethane scaffold using a rotational vacuum seeding device.
After they had cultured their vascular constructs for seven days, the researchers implanted them in the abdominal aortas of rats eight weeks before performing tests to determine how well the grafts had performed.
It was found that the cell-seeded constructs showed a significantly higher blockage-free rate than unseeded controls. The researchers also found that there was an extensive remodelling of the MDSC-seeded polymer by surrounding tissue, exhibiting tissue formation that is consistent with a mature artery.
Dr. Vorp says that the new findings demonstrate the feasibility of developing MDSC-seeded tissue-engineered vascular grafts for eventual human application.
"The next step is to demonstrate the use of the tissue-engineered blood vessel in a larger animal model, such as a pig, which has a coagulation system more similar to that in humans. The advantage of our approach is that the graft could utilize the patient's own stem cells and be ready for implantation almost immediately or, at most, after a relatively short culture period. This suggests that we could make these available 'off-the-shelf,' which is an essential element for clinical translation," he explained.