Different Types of Grafts

There are 3 different types of vascular grafts: in vitro, in vivo, and in situ. In vitro vascular tissue engineering is a method in which the vascular grafts are formed outside the body. In my last post, I described in vitro vascular tissue engineering which is characterized by a biodegradable scaffold, cells, and signals. With in vivo vascular tissue engineering, a graft is made in the vessel by using the peritoneum (under layer of the skin) as a bioreactor. The only difference between in vitro and in situ tissue engineering is that in vitro grafts take a much longer time to culture and develop. In situ grafts are thus more appealing because they have the capacity to be produced and distributed quickly.

The Basics

The fundamental idea of tissue engineering in relation to the vasculature is to replace arteries and veins by restructuring them. The ultimate goal is to create what researchers call "neotissue." Neotissue is comprised of 3 components: cells, a biodegradable scaffold, and signals. Existing cells in the vasculature are required to ensure that the body accepts the new tissue without any complications. The biodegradable scaffold is designed to keep the new vasculature in place temporarily. Eventually, the scaffold biodegrades. By that point, though, the neotissue will be fully functioning an able to support itself. Lastly, signals, or nerves, are required. In order for arteries to pump blood they must receive nerve impulses. It is important that the neotissue receives these signals (through signals) so that the neotissue pumps blood properly. It should be noted that tissue engineering can be used to replace both arteries, which carry blood from the heart, and veins, which carry oxygenated blood.