In Situ Tissue Engineering of an Artery
The logical progression for tissue engineering is to move to building inside the body rather than building outside and then transplanting the resulting new tissue. Here is an example of that trend: "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. ... [Researchers] designed the graft with three properties in mind. 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. [They wrapped] the vascular graft with a fibrous sheath to trap the cells. Finally, [researchers] wanted a coating for the grafts that would reduces blood clotting and bind many growth factors, so they used heparin, a molecule that does just that. ... [Researchers] made grafts as small as 1 mm in diameter and monitored the graft's transformation in vivo for three months. Because the graft was highly porous, cells were easily able to penetrate the graft wall, and mononuclear cells occupied many of the pores within three days. 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. The artery was regenerated in situ and pulsed in sync with the host. Furthermore, the composition and properties of the new arteries are nearly the same as native arteries."
Link: http://www.eurekalert.org/pub_releases/2012-06/uop-pdb061912.php