Researchers have developed a new biodegradable graft that helps regenerate coronary arteries within 90 days of bypass surgeries, leaving no trace of itself in the body.
Designed by principal investigator professor Yadong Wang and his team from the University of Pittsburgh Swanson School of Engineering, the graft fully harnesses the body’s regenerative capacity.
“The host site, the artery in this case, is an excellent source of cells and provides a very efficient growth environment. This is what inspired us to skip the cell culture altogether and create these cell-free synthetic grafts,” said Wang, the journal Nature Medicine reports
The team, which included former Pitts postdoctoral associate Wei Wu and bioengineering doctoral student Robert Allen, designed the graft with three properties in mind, according to a Pittsburgh statement.
First, they chose a graft material – an elastic polymer called PGS – that is resorbed quickly by the body. Then, they examined graft porosity and selected parameters that allow immediate cell infiltration.
Wang’s team borrowed a procedure developed by another team of Pitt researchers – David Vorp, professor of bioengineering and surgery, and William R. Wagner, professor of surgery, bioengineering and chemical engineering – wrapping the vascular graft with a fibrous sheath to trap the cells.
Finally, Wang’s team wanted a coating for the grafts that would reduce blood clotting and bind many growth factors, so they used heparin, a molecule that does just that.
“The results were porous grafts that are suturable,” said Wang. “And the rapid re-modelling of the grafts led to strong and compliant new arteries. The extent of the changes in the grafts that occurred in just 90 days was remarkable.”
Wang and his colleagues made grafts as small as one mm across and monitored the graft’s transformation in the body for three months. Within 14 days, smooth muscle cells – an important blood vessel builder – appeared.
At 28 days, cells were distributed more evenly throughout the graft. At 90 days, most inflammatory cells were gone, which correlated with the disappearance of the graft materials.
“This report is the first that shows a nearly complete transformation of a synthetic plastic tube to a new host artery with excellent integration within three months,” said Wang.
“Most likely, the amount of time it takes to regenerate an artery can be further shortened as we refine the system.”