( ed inside the body. So Hoffman-Kim put ...)Growing nerve cells in 3-D dramatically affects gene expression

To answer that question, Hoffman-Kim and researchers in her lab took a line of cancerous nerve cells and cultured them in different environments. They placed one batch of cells in standard petri dishes coated with collagen. They suspended the other batch in a thicker collagen gel. The bioengineers took great pains to be sure that this one-dimension difference was the only difference in the culture conditions. Team members even counted individuals cells as they went into the dishes to be sure that each dish contained precisely the same amount.

After a day of growth, the researchers extracted RNA from the cells and conducted a microarray analysis to determine differences in gene activity. The results: A whopping 1,766 genes responded differently, either switching on or switching off. To check their work, researchers repeated the experiments but this time produced multiple copies of eight genes specifically linked to cell growth. Those experiments confirmed the differences in gene activity.

Hoffman-Kim and her team deployed high-powered microscopes to detect other differences. Cells cultured in 3-D had a rounder, more realistic shape, and their neurites ?spindly projections sprouting from the cell body ?were longer.

"The cells in 3-D culture grew faster and looked more like the body's cells," she said. "This means that this culture method might create tissue that could be more successfully implanted."