Dance the Bionic Electric
By Michael Cervieri and Fang Cui

Michelle Caldwell is a painter in New York. On days when the sun shines and the weather is right she likes to put down her paints, put on her rollerblades and skate around Central Park.

Cloudy days are a bit different. On these days she waits and sees if a dull throb pulsates through her knee.

If it does, she will say, before the clouds darken or the first drop even touches the ground, "It's going to rain. I feel it in my bones."

The bones in question are held together by two screws inserted 15 years ago when Caldwell's knee began to fall apart. She did not suffer some dramatic injury or have a great fall. Instead, her knee degraded slowly until it was painful to walk. Seven surgeries and two screws later she was back on her feet with an impressive sixth sense of meteorological foresight but an inability to pursue anything more strenuous on a rainy day than hobbling about and waiting for the weather to clear.

Today, however, an army of scientists — backed by universities and Wall Street to the tune of hundreds of millions of dollars — are pushing forward to provide radical new cures for people with degenerative bone and organ conditions.

Part bionics, part evolutionary manipulation, the day is not so far away when living implants grown from a patient's cells will replace the metal screws that currently hold people like Caldwell together.

Debuting in mid-1980s, tissue engineering has made great progress partly due to advances in other related disciplines — cell biology, genetics and engineering.

But while some researchers are just scratching the surface of what's possible with cells and tissues, others have embarked on a new journey to put the engineered organs into functional tests.

Not only are they developing cells that behave like a heart or a liver, but they are also making sure that these new creations can withstand the stress and strain of actually acting like those organs once inside a living, breathing body.

"The next big new thing is functional tissue engineering," says Dr. Van C. Mow, chairman of Department of Biomedical Engineering at Columbia University.

Next: Scaffold, Matrices and Mice with Ears on Their Backs

Say What? A Glossary

Tissue engineering: The loss or failure of an organ or tissue is one of the most frequent, devastating, and costly problems in human health care. A new field, tissue engineering, applies the principles of biology and engineering to the development of functional substitutes for damaged tissue.
Biomaterials: A crucial mainstay of tissue engineering is the biomaterial from which scaffolds are fashioned. Many biomaterials direct the growth of cells in culture. However, tissue regeneration in vivo (i.e., within the subject) involving the guided growth of nerve, bone, blood vessels, or corneal epithelia across critical injury sites requires that cells receive more specific instructions.
Cell: The smallest structural unit of an organism that is capable of independent functioning, consisting of one or more nuclei, cytoplasm, and various organelles, all surrounded by a semi-permeable cell membrane.
Stem cell: An unspecialized cell that gives rise to a specific specialized cell, such as a blood cell.
Matrix: The lifeless portion of tissue, either animal or vegetable, situated between the cells; the intercellular substance.
Scaffolds: Scaffolds are porous, degradable structures fabricated from either natural materials (collagen, fibrin) or synthetic polymers (polyglycolide, polylactide, polylactide coglycolide). They can be spongelike sheets, gels, or highly complex structures with intricate pores and channels fabricated using new materials-processing technologies. Virtually all scaffolds used in tissue engineering are intended to degrade slowly after implantation in the patient and be replaced by new tissue.
Tissue architecture: The correct molecular and macroscopic architecture of cartilage, blood vessels, bone, and other tissue is essential for proper tissue function. Connective tissue cells grown on 3D scaffolds in vitro secrete biochemically appropriate extracellular matrix molecules yet fail to acquire the appropriate tissue architecture.