Chemically modified microfibrous vascular grafts have good patency
MedWire News: US scientists have used chemical modification of microfibers to create small-diameter, acellular, vascular grafts that are nonthrombogenic and have long-term patency.
"Arterial replacement is a common treatment for vascular diseases, with more than 500,000 vascular grafts being used in the bypass procedures of coronary and peripheral arteries each year," remark Song Li (University of California, Berkeley) and colleagues.
"However, small-diameter synthetic vascular grafts frequently have issues with thrombosis and occlusion," they add.
In the present study, Li and team used an electrospinning technique to produce microfibrous vascular grafts with a 1 mm internal diameter. They then conjugated hirudin, a naturally-occurring thrombin inhibitor, to the poly(L-lactate) microfibers through an intermediate linker of poly(ethylene glycol) (PEG).
To determine whether the grafts modified by PEG and hirudin-PEG can reduce platelet adhesion, the researchers incubated them with platelet-rich plasma for 30 minutes. They found that microfibrous scaffolds with conjugated PEG and hirudin-PEG had significantly fewer platelets on their surfaces than untreated microfibrous scaffolds. The similar reduction of platelet adhesion by PEG and hirudin-PEG suggested that PEG was responsible for the antiplatelet adhesion property.
Li and team then implanted the grafts into the common carotid artery of rats for 1 month to compare their antithrombogenic properties. At 1 month, 50% of untreated grafts were patent, 75% of PEG grafts were patent, and 83% of hirudin-PEG grafts were patent, indicating that both PEG and hirudin improved the patency rate.
Further studies showed that all patent samples had complete endothelial coverage at 1 and 6 months post implantation, and the microfibrous structure of the vascular grafts allowed efficient graft remodeling and integration, with mechanical property (elastic modulus) improving from 3.5 MPa before implantation to 11.1 MPa 6 months after implantation.
There were also few CD68-positive cells within the walls of the graft, suggesting minimal inflammatory responses to the grafts.
Writing in the journal Arteriosclerosis, Thrombosis and Vascular Biology, Li and co-authors conclude that the ability to create antithrombogenic small-diameter vascular grafts may make it feasible to offer vascular grafts off the shelf in the near future.
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By Laura Dean