An engineered tissue’s surprising development

Christopher K. Breuer, M.D., and Toshiharu Shinoka, M.D., Ph.D., have been studying the use of tissue-engineered vascular grafts (TEVGs) to treat congenital heart defects. TEVGs—created by seeding a biodegradable scaffold with a patient’s bone marrow cells (BMCs)—make living vessels that will grow as a child grows and could last a lifetime.

Breuer and Shinoka, both associate professors of surgery and pediatrics, and Yale colleagues explored how BMCs are transformed to vessels in TEVGs. BMCs are stem cells, so many scientists thought that BMCs differentiate into the endothelial and smooth-muscle cells that comprise blood vessels.

But in the March 9 issue of Proceedings of the National Academy of Sciences, the group reports that BMCs were undetectable soon after TEVGs were implanted into mice. Instead, the graft appeared to initiate an inflammatory response that drew white blood cells to the scaffold, replacing the BMCs. These cells were also soon replaced, with the mouse’s own blood vessel cells.

This “better understanding of how TEVGs develop in vivo will lead to improved second-generation TEVGs,” the authors write.