Steady Advances in Tissue Engineering

Tissue engineers are, as one might expect, steadily becoming better at building comparatively simple forms of human tissue - not that any tissue is actually simple. Even straightforward muscle like heart tissue is formed of layered types and laced with tiny blood vessels. A great deal of money and expertise is involved these days, however, and challenges will be overcome step by step:

University of Washington (UW) researchers have succeeded in engineering human tissue patches free of some problems that have stymied stem-cell repair for damaged hearts. The disk-shaped patches can be fabricated in sizes ranging from less than a millimeter to a half-inch in diameter. Until now, engineering tissue for heart repair has been hampered by cells dying at the transplant core, because nutrients and oxygen reached the edges of the patch but not the center. To make matters worse, the scaffolding materials to position the cells often proved to be harmful.


Stevens and her fellow researchers added two other types of cells to the heart muscle cell mixture. These were cells similar to those that line the inside of blood vessels and cells that provide the vessel's muscular support. All of the heart muscle cells were derived from embryonic stem cells, while the vascular cells were derived from embryonic stem cells or a variety of more mature sources such as the umbilical cord. The resulting cell mixture began forming a tissue containing tiny blood vessels.

"These were rudimentary blood vessel networks like those seen early in embryonic development," Murry said.

In contrast to the heart muscle cell-only tissue, which failed to survive transplantation and which remained apart from the rat's heart circulatory system, the pre-formed vessels in the mixed-cell tissue joined with the rat's heart circulatory system and delivered rat blood to the transplanted graft.

This isn't as flashy as demonstrations of entire tissue-matched hearts created using decellularizing techniques and stem cells, but you should pay attention to progress in straightforward construction of tissue sections from scratch - especially progress in solving the blood vessel issues. The odds are good that you'll have pieces of fabricated tissue working away inside you thirty years from now, replacements for areas where age got the better of your standard issue physiology.


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