A Look at Scaling Up the Tissue Engineering of Larger Blood Vessels
Perhaps the greatest challenge in the field of tissue engineering is the production of integrated networks of small blood vessels sufficient to support larger tissue sections. Without a reliable way to do this, researchers are limited to producing the tiny functional tissue masses known as organoids. When it comes to making larger blood vessels, however, good progress is being made. This article takes a look at the efforts of one alliance of research groups, aiming for the widespread, cost-effective availability of engineered arteries:
The prospect of creating artery "banks" available for cardiovascular surgery, bypassing the need to harvest vessels from the patient, could transform treatment of many common heart and vascular ailments. But it's a big leap from concept to reality. Patients needing bypass surgeries would benefit from a better source for arteries. Replacement tissue currently comes from another part of the patient's body, and suitable tissue can't be found for many patients. Current synthetic alternatives also fail at a high rate. Diseases of blood vessels - including coronary artery disease - kill more people worldwide than any other single cause.
"Tissue engineering for blood vessels is a pretty mature field. But there are still two major problems: One is the time it takes to make the vessels, and the other is the source of the cells to grow them." For example, taking induced pluripotent (iPS) stem cells from an individual patient, growing the relevant cells and assembling them into an artery would overcome the problem of transplant rejection. However, it would be cost-prohibitive and take months to complete - too long to be clinically useful to a patient. The promising alternative is to create tissue with cells banked from a unique population of people who are genetically compatible donors, based on rare alleles that circumvent rejection. It has been estimated that about 100 different cell lines from this rare population would be enough to cover a majority of the U.S. population.
A new effort covers four phases and addresses key questions about the feasibility of this approach. The model for the project is designed around treating critical limb ischemia, a debilitating condition that restricts blood flow to limbs and often leads to amputation or death. Researchers are working to create the optimal cellular building blocks of the artery - endothelial and smooth muscle cells - that will be most suitable for transplantation and continue to grow and remodel in the patient. In tandem, a different team will develop scaffolds from natural and synthetic materials to provide structure and shape for the artery. Other researchers will build a bioreactor that provides an environment in which the arterial cells can grow around the scaffolding. The transplant surgery and resulting immune response will then be tested using a monkey limb ischemia model. Having a primate model is important to produce results more relevant to human health than those from mice or other short-lived animals. Finally, there is the production of arterial cells that meet FDA standards for human clinical trials, paving the way for potential treatments for limb ischemia in humans. If the entire process works, researchers estimate that potential human therapies remain about 10 years away.
Link: http://news.wisc.edu/morgridge-uw-project-investigates-tissue-engineered-arteries-for-transplant/