Tuesday, May 29, 2012

Engineers create functioning blood vessels

Creating artificial organs could in the future solve the lack of organ donors and provide increased compatibility for the patient receiving an organ. However, there are several roadblocks on the way, including the lack of vascularisation in artificial tissues. Basically, that means stuff that scientists grow in the lab does not achieve growth of blood vessels, causing a lack of nutrients and oxygen, meaning tissues cannot fully develop. To create a functional organ, a blood vessel system is necessary, which is why scientists from the University of Washington have created a synthetic system that allows for artificial development.

Using so-called endothelial cells, that form the inner lining of blood vessels, the engineers managed to create hollow tubes that allow for transport of blood. For this, they used a network of channels made of collagen gel: it allows formation of vessels that possess the right characteristics. A similar idea has been developed to clean blood, which also makes use of an artificial network of channels. Basically, the hollow collagen-based tubes function as a mould for a vascular system, allowing for formation of vessels out of a mix of endothelial cells. Being only a few micrometers in width, the resulting tubes are as small as capillaries, which are the smallest blood vessels in the body. These micro-vessels are responsible for the actual exchange of oxygen, carbon dioxide and nutrients in organs and tissues, while bigger vessels are used exclusively for transport.
From big to small: arteries, arterioles and capillaries. Tissues receive oxygen and nutrients from capillaries.
To assess whether their artificially engineered blood vessels were functional, the scientists subjected them to a series of tests. It appeared that the tubes did their job of transporting blood quite well: they even managed to keep up circulation with 90-degree bends in the vascular system, and the blood also did not stick to the walls. After pumping blood filled with inflammatory proteins, produced by the body after damage or trauma, through the artificial network, the scientists found clotting just like it would in an ordinary vascular system. 

Blood vessels are important to keep tissues and organs alive, which is why we need them if we want to create artificial organs ourselves. As I experienced first-hand, getting a functional blood vessel system to keep up growth of your lab-cultured tissues is not an easy task. Therefore, the collagen tubes ought to help scientists grow tissues, which take us another step forward to our goal of creating on-demand transplantable organs in the lab. 

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