Wherever we find some of the worse medical events – heart attacks, strokes, pulmonary embolisms, we find blocked blood vessels. Obstructed blood vessels are a lurking time bomb in our bodies and they usually have to be replaced. Blood vessel replacement requires cutting another blood vessel from another part of the body or the implantation of artificial vascular prostheses.
A new option might emerge in the future, however. Vienna University of Technology, in collaboration with the Vienna Medical University developed artificial blood vessels that were fabricated from specialized elastomer material that have excellent mechanical properties. After implantation, these artificial blood vessels are dissolved and replaced by the body’s own blood vessels. At the end of the healing process, natural, fully functional blood vessels are once again in place. The technique works quite well in tissue cultures systems, but now it has been shown to successfully regenerate blood vessels in laboratory animals, specifically rats.
Atherosclerotic vascular disorders, in which blood vessels are obstructed by cholesterol-filled plaques, are one of the most common causes of death in industrialized countries. Typically, patients are treated with a bypass operation, and for such procedures, blood vessels are extirpated from another part of the patient’s body and used to replace the damaged vessel. This creates a new wound and a new area of the body with less than optimal blood supply that must heal. Also, the transplanted vessel rarely has the properties necessary to thrive in its new location.
This new strategy to replace diseased blood vessels is the result of a fruitful collaboration between Vienna University of Technology (or TU Wien, which is short for Technische Universität Wien) and the Medical University of Vienna. Hopefully the success of this research will cause artificially manufactured vessels to be used more frequently in future.
To make an artificial blood vessel, the most important thing is to start with the right material. The material must be compatible with body tissue, and pliable enough to be formed into a small diameter tube that is not easily blocked by blood clots.
Extensive work at TU Wien has resulted in the development of new polymers. “These are so-called thermoplastic polyurethanes,” explains Robert Liska from the Institute of Applied Synthetic Chemistry of TU Wien. “By selecting very specific molecular building blocks we have succeeded in synthesizing a polymer with the desired properties.”
In order to generate artificial blood vessels from their thermoplastic polyurethanes, TU Wien materials scientists spun polymer solutions in an electrical field. This allowed them to form very fine threads and that could be wound into a spool. “The wall of these artificial blood vessels is very similar to that of natural ones,” says Heinz Schima of the Medical University of Vienna. The thermoplastic polyurethanes form a polymer fabric that is slightly porous and allows a small amount of blood to leak through it. This also enriches the blood vessel wall with growth factors, which encourages the migration of endothelial progenitor cells. Martina Marchetti-Deschmann at TU Wien studied the interaction between the thermoplastic polyurethane material and blood by using spatially resolved mass spectrometry.
This new technology has already proven to successfully form functional blood vessels in rats. “The rats’ blood vessels were examined six months after insertion of the vascular prostheses,” says Helga Bergmeister of MedUni Vienna. “We did not find any aneurysms, thromboses or inflammation. Endogenous cells had colonized the vascular prostheses and turned the artificial constructs into natural body tissue.” In fact, the body’s own blood vessel-forming tissues re-grew significantly faster than expected, which shortened the degradation period of the plastic tubes and their replacement with the body’s own endothelial cells. TU Wein and the Medical University of Vienna are making further adaptations to the material.
A few more preclinical trials are necessary before the artificial blood vessels can be used in human clinical trials. However, based on the results so far, the research team is very confident that the new method will prove itself for use in humans in a few years’ time.
This project was recently awarded PRIZE prototype funding from Austria Wirtschaftsservice (AWS).