In tissue engineering, human cells are introduced into a scaffold on which they grow and divide, producing replacement tissue. Images courtesy of Advanced Tissue Sciences, Inc.

Tissue Engineering: A Case Study

Tissue engineering is a new specialty which creates usable human tissues for repairing or replacing damaged ones. Engineers have tackled this problem by relating medical and biological approaches to those of chemical engineers, materials scientists and engineers, and mechanical and electrical engineers.

Some of the basic approaches of tissue engineers also borrow from civil engineering: "scaffolds" are used for building tissues, providing biodegradable structures on which cells can grow. Another key device used by some tissue engineers is the "bioreactor," a vessel especially designed for the cultivation of living tissue.

Tissue engineering is just now emerging from the laboratory into medical applications. Among the pioneers are engineers and scientists at Advanced Tissue Sciences, Inc., in San Diego, California. Their experimental products include skin, cartilage, and liver tissue.

The sequence of cell seeding and growth can be seen in these drawings. Scaffolds are designed for specific tissues; this one is for skin.	Millions of living skin cells, called fibroblasts, are seeded within the scaffold. The cells multiply on the scaffold, which is contained and nourished within a device called a bioreactor.	In the bioreactor, the cells grow and multiply. As they organize themselves into three-dimensional layers of skin, the scaffold material slowly degrades and disappears.
Over a period of a few weeks, human skin tissue is formed, ready to treat victims of serious burns. This photograph shows skin cells that have multiplied. The cells have been tricked into thinking they are in their natural environment instead of an engineered structure. Several days after seeding, they completely fill in the space of the scaffold. A few weeks of further growth will produce a piece of artificial skin large enough to be used for healing burns or replacing diseased tissue. Courtesy of Advanced Tissue Sciences, Inc.