Scientists have already taken a major step toward that goal by coaxing human stem cells to grow in the laboratory. Stem cells are the early embryonic cells that differentiate to form all of the specialized cells in the body, such as muscle and skin. The first person to reach the goal of growing stem cells outside the body was a researcher at the University of Wisconsin-Madison. That was in late 1998, and in December 1999 Science magazine declared subsequent work on stem cells to be the scientific breakthrough of the year. Yet growing stem cells, or even knowing how to make them become heart muscle cells, is a long way from actually growing an organ, said Ross Gundersen, associate professor of biology at UW-Parkside.
Development is exactly the same way.
The communication is chemical, and its existence points up another barrier to growing organs. There's a lot that's said about genetics, molecular biology, genetic engineering, but one thing that became very, very apparent to people studying development a long time ago is that there is not enough genetic information in a cell to essentially have it determine an organ. It's only when these cells start communicating with one another that that possibility comes into existence. In the brain, for example, neurons branch in specific ways, yet there isn't enough genetic information in cells to determine the structure of a brain, Gundersen said. A heart is built not only of heart muscle but also of nerve cells that stimulate the heartbeat.