"It shows the public the biomedical research community's level of achievement, just as the Olympic Games demonstrate a high level of athletic accomplishment," said Patrick Tresco, an associate professor of bioengineering and director of the university's Keck Center for Tissue Engineering.

The "living rings" icon of five interlinked rings measures 3.4 millimeters -- about one-eighth inch long. The body of each nerve cell -- glowing as bright red dots in a fluorescence microscopic picture of the rings -- measures 20 microns, or two-fifths the width of a human hair. Each nerve fiber or axon in the rings is one micron wide -- about one-fiftieth the width of a human hair.

The nerve cells grew on a bioengineered scaffold made of other cells, which in turn grew on a plastic material.

The "living rings" were made in December by graduate student Mike Manwaring, a native of Pleasant Grove, Utah, in response to a challenge Tresco issued to his lab staff.

"The objective of our lab is to control cell behavior on materials," Tresco said. "So I challenged the group to create a living symbol of the Olympic Winter Games -- using living nerve cells and tissue engineering technology."

Tresco presented a photograph of the living rings to Utah Gov. Mike Leavitt when the governor toured Tresco's laboratory on Dec. 20 to learn about tissue engineering.

Years from now, the technology being developed in labs such as Tresco's may be used to reconnect damaged nerves in people with traumatic brain injury or spinal cord injury, or to help connect transplanted nerve cells to the appropriate places in people with brain disorders like Parkinson's or Alzheimer's diseases.

"We are at the earliest stages, but we are tremendously hopeful there will be a convergence of biological discovery and engineering know-how to help rebuild the human nervous system in the future," Tresco said.

He estimated it would take at least a decade and considerable capital investment before severed or damaged spinal cords can be repaired or damaged nervous systems can be rewired. There are numerous hurdles, including "our lack of knowledge of how the nervous system is wired," he said.

"It's one thing to get nerve cells to grow in a dish like this," Tresco said. "It is orders of magnitude more difficult to have this occur in a damaged nervous system. For one thing, we don't have the blueprint of how all the individual nerves are connected at present."

Tresco said the technology eventually might be used in several ways, including:

* A bridge of bioengineered material -- perhaps an injectable gel or a solid bundle of biodegradable material like that now used in surgical sutures -- could be placed next to a severed spinal cord or other damaged nerve so that new nerve fibers could grow along the bridge and bypass the damaged area.

* Stem cells or embryonic cells capable of growing into nervous system tissue might be transplanted to replace damaged nerves. Such cells might be used together with a bridge of bioengineered material.

A major challenge is for researchers to learn "how to get nerves to grow in specific directions," Tresco said.

The living rings were made using materials that, in certain cases, were different than the materials that would be used in attempting to repair nerve damage in human patients.

The first steps in making the living rings resulted in a mold made by a photolithographic process like that used to make circuit boards or tiny objects known as microelectromechanical systems (MEMS).

(1) A high-quality printer was used to make a tiny pattern or "mask" in the shape of the Olympic Rings.

(2) Photoresist, a plastic-like polymer substance, was sprayed on a piece of brass.

(3) The mask in the shape of the rings was put on top of the coated brass. Then the coated brass with the mask was exposed to ultraviolet light for a few minutes. That affixed the plastic coating to the brass, except where the mask was located, leaving a mold in the shape of the rings.

(4) The rings-shaped mold then was etched with acid to make it deeper.

(5) Rubbery silicone was poured over the mold, creating a tiny set of rings.

(6) Heat-moldable clear plastic (polystyrene) was pressed against the silicone rings under heat and pressure, creating a new, transparent mold of the rings.

(7) A protein named fibronectin was made to stick to the mold. Fibronectin is a protein normally found in and around cells in various tissues in the body.

(8) Then the mold of the rings was put in a culture dish with a liquid to promote growth. Meningeal fibroblasts -- cells that form the connective tissue surrounding the brain and spinal cord -- were added. The fibroblasts were cultured for four days with the fibronectin-coated mold of the rings. As a result, the fibroblasts aligned themselves so they grew within the mold, forming live scaffolding in the shape of the Olympic Rings.

(9) Nerve cells or neurons were taken from adult rats, specifically from the dorsal root ganglion -- a set of nerve cells that is located just outside the spinal cord and that relays sensory information like temperature and pressure from skin and muscles to the brain. The nerve cells were placed in the culture dish along with the scaffolding shaped like the rings. The nerve cells were grown for 96 hours, during which they stuck to the fibroblast cells and grew new nerve fibers along the shape of the rings.

(10) To make a photograph of the tiny living rings, antibodies tagged with a fluorescent red dye were added to the culture dish. The antibodies attach to proteins made by the living nerve cells. The living rings were placed under a microscope attached to an electronic camera. The microscope detects only the fluorescent red color. The resulting photograph shows the living rings, with nerve cell bodies glowing brightest red, and nerve fibers and underlying fibroblast cells glowing with a less intense red.

Related image:

High-resolution color photograph of the "living rings"


[Contact: Patrick Tresco, Coralie Alder, Lee Siegel]

15-Jan-2002