Prior to this study, the SUNY Buffalo researchers thought fibrin could be substituted for collagen as a scaffold for TEV because it shares high seeding efficiency (with smooth muscle cells, or SMCs) and uniform cell distribution. Indeed, in "contrast to collagen, fibrin stimulates synthesis of collagen and elastin and yields TEV constructs with improved mechanical properties, suggesting that fibrin may be a more appropriate scaffold for cardiovascular tissue engineering," they said.
In the current study, the SUNY Buffalo researchers took lamb vascular smooth muscle and endothelial cells to engineer small diameter (4mm) blood vessels, "which attained considerable mechanical strength and vasoractivity after only two weeks in culture." When the thrombin/fibrinogen solution was poured into the fibrin mold to start the process, it "gelled within 5-10 seconds."
Tests using vasoactive receptor and nonreceptor substances showed that the fibrin-based TEVs exhibited an ability to expand and contract over time, similar to native vessels. This is a very important property that allows blood vessels to adapt to changes in blood flow rate.
Transplanted TEVs produce new collagen, elastin
Furthermore, after "a short time in culture, SMCs remodeled the extracellular matrix by substituting the fibrin gel with collagen." They found that after only about two weeks, the structure was ready for transplantation. "TEVs containing SMC and endothelial cells were implanted as interpositional grafts into the external jugular veins of 12-week-old lambs," Swartz et al. reported. "After implantation TEVs int