Creating the body's microenvironment to grow artificial organs.

• Author: Jean, Grace V.
• Position: INSIDE SCIENCE + TECHNOLOGY

Whether due to disease, injury or other causes, millions of Americans suffer tissue loss or organ failure every year. Those who need replacements are put on organ donor lists. But the supply falls far short of demand.

To supplement the low numbers of donors, scientists during the past two decades have attempted to grow human organs in laboratories. While they have had limited success with skin and other simple tissues, they have encountered many challenges in producing complicated organs, such as the liver, kidney and lung.

Part of the difficulty is that those organs require an intricate network of blood vessels to support their growth. Such vascular systems bring oxygen and nutrients to the tissue and carry away waste. Unlike in the human body, tissues grown in the laboratory do not necessarily generate their own vascular supply, says Jeffrey Borenstein, director of the biomedical engineering center at Draper Laboratory in Boston.

[ILLUSTRATION OMITTED]

"There's only so much of a distance that the oxygen and nutrients and waste can travel, so you need to have not just a few large blood vessels, but this incredible network of blood vessels that goes down to the capillary level," he says.

Most of the work in tissue engineering has focused on the biology of the cells and the material properties of the "scaffold" that the cells thrive on. Just as the walls of a house need a foundation upon which to rise, the cells of tissues require a flame upon which to grow.

"If you just grow the cells in a dish, you're going to have an amorphous blob of cells that do not have much mechanical integrity or stability, and that do not take a very defined shape," says Borenstein.

Conventional tissue grids lack sufficient structures to support a sophisticated vascular system. By addressing the engineering of the scaffold itself, Borenstein and his team have taken a novel approach to the vascularization problem.

Using processes and tools commonly employed to manufacture small electronics, known as micro-electromechanical systems, or MEMS, the researchers are micromachining minuscule scaffolds made of biodegradable or bio-absorbable polymers with tiny channels in which vascular cells can attach and multiply. Once the blood vessel network is viable, the scientists can spur the growth of tissues and organs around it.

"Our hypothesis is that you need to create a microenvironment that the cells experience in the body. You need to recreate that in the lab, and...