“We’re interested in ways to repair holes and other soft tissue injuries because, well, bullets make those kinds of holes,” says Morrison, who confirmed that human trials with the elastin patch are not far down the road.
As promising as these internal injury patches are, another potential market for elastin – vascular grafts – is much greater. They can be used to treat, among other medical problems, heart disease. An estimated 70,000 people a year cannot undergo invasive treatment for heart disease because their blood vessels are too small and fragile for a plastic stent (tubes used to hold open hollow structures within the body).
“The problem with current synthetics is that they have a high rate of clotting,” explains Raul Guzman, assistant professor of surgery at Vanderbilt University Medical Center.
What’s more, potential grafts from a patient’s own legs, arms, or chest are often too weakened themselves or have already been used in a previous surgery, leaving few options.
Despite its potential, though, pure elastin has limitations when used alone to make vessels. For one thing, it can tear easily, making suturing difficult, if not impossible. As a result, Gregory’s work now focuses on elastin “scaffolds” that incorporate a layer of stiffer protein (collagen) for structural integrity, grafts, and elastin-coated stents. If implant experiments using the stent on pigs prove successful this summer, Gregory hopes to gain approval for human clinical trials of stents in 2006.
In addition to the hundreds of thousands of bypass surgery patients who could benefit from the improved patching and support of valves, elastin research is aimed at helping soldiers who suffer injuries to their extremities – now one of the most common types of field casualties. Military surgeons would have a much better chance of saving a soldier’s hand or foot, for instance, if they could replace the smaller vessels that supply it with blood.
Finally, Gregory and his colleagues are hoping to literally grow vessels for patients. He’s an advisor to Honolulu-based Tissue Genesis Inc. (TGI), which is developing the mechanism to rapidly introduce populations of cells inside an elastin graft.
The idea, explains Gene Boland, TGI’s senior scientist for vascular tissue engineering, is to “harvest cells and rapidly put them on the inside of any conduit [vessel or a segment of a vessel] that we can then re-implant into the body. And we don’t need to go back to lab and grow it; we can do it all in the operating room.”
Vanderbilt’s Guzman describes the real-life case of a patient who would benefit from such improved vascular technology: a 69-year-old male with diabetes who had previously undergone a coronary artery bypass operation and two lower-extremity bypass procedures on his left leg.
“The first [bypass] was performed with PTFE [Gore-Tex] and the second [bypass]…with his own greater saphenous vein,” says Guzman, “Unfortunately, the vein graft clotted and he developed a non-healing ulcer on his foot. There were no suitable conduits available for revascularization and the patient subsequently underwent left leg amputation.”
When asked about the potential benefit for the kind of breakthrough technology that Gregory is pursuing, Guzman was unequivocal: “On a scale of 1 to 10, the value of solving this problem would be a 10.”
Portland, Oregon-based writer David Wolman reports on a variety of subjects, including health, energy, and oceanography. His first book, A Left-Hand Turn Around the World, about the science and culture of left-handedness, is due out this fall.