Sun, 08 Jun 2003

'Tissue engineering' the future for replacment body parts

Christiane Loell, Deutsche Presse-Agentur, Stuttgart

People suffering from liver failure, heart attacks or worn knee joints often need replacement parts, and researchers around the world are working to develop artificial tissue so these patients can be helped.

The process within the biotechnology discipline is known as "tissue engineering". Biologists, doctors and engineers are cooperating to devise ways of developing functioning tissue from human cells, nutrients and plastics.

Professor Heinrich Planck, director of the German Centre for Biomaterial and Organ Substitutes, said: "This is a business in which you need a lot of patience."

Planck has been working in tissue engineering for almost 30 years. He heads projects to work on substitutes for blood vessels, nerves and skin. A team he heads began 15 years ago developing an artificial pancreas.

Planck: "This is something which could help diabetes sufferers, whose pancreas produces no insulin."

The idea is to implant a tiny polyurethane tube containing insulin-producing pig cells and to integrate the tube into the blood-vessel network. So the pig cells are not rejected, a fine membrane of capillaries separates the human tissue from the animal cells.

Planck said that the project received a setback when it became clear in laboratory tests that human blood and the plastic being used did not tolerate each other well. Tiny blood clots emerged in the Petri dish.

So the researchers were forced to look for a better suited material.

This summer, the centre will begin to place artificial pancreases in pigs. If everything goes according to plan, it would mean that within a few years, diabetics should be able to benefit from the implantation. This would mean they would no longer need to inject themselves with insulin each day.

Planck added that it would be better if human cells were used, but he said that stem-cell research was not yet sufficiently advanced and human donor organs were rare.

The centre also wants to help in the field of worn-out joint cartilage. The aim is to remove a person's own, healthy cartilage cells, place them on a shaped poly-lactic-acid matrix and allow them to multiply. Later, the tissue thus grown would be placed in the patient.

Planck: "The challenge here is to grow the cartilage which is able to withstand the strongest mechanical movements."

Trials with more elastic cartilage found in the nose and ears turned out to be more difficult than expected. "The cartilage was not hard enough - and on top of that, who wants a set of floppy ears?"

Artificially grown tissue is not only finding a use in humans. Researchers are also creating it to use in testing medicines and to improve pharmaceutical research.

Dominik Monz is from the Fraunhofer Institute for Biomedical Technology (IBMT) in the town of St. Ingbert, in Saarland. He said that this type of research offered the chance in the long term to dispense with animal experiments.

At IBMT, biologists and engineers work together. The biologists grow retina material and heart muscle tissue from cells taken from chicken embryos and nutrients.

"The tissue is not visible to the naked eye but, if you look through a microscope, the heart muscle cells can be seen twitching," Monz said.

Engineers at IBMT also design microchips with capillaries which are placed in the grown tissue. Using electrical measurements, engineers can see what is happening with the cells.

"You can see, for example, if the cell nucleus dies during cell division," Monz said.

This process could be employed to test the efficiency of chemotherapy treatment for cancer or to check if pesticides are harmful to healthy cells.

"In that way, limits to individual toxins can be established," he added.

The use of these technologies for pharmaceutical research has in some cases has been disappointing for tissue engineers: they noticed that entire livers or hearts cannot easily be grown.

Planck: "For a time there were some euphoric reports, especially from the United States, but these were aimed at drumming up cash for the research." This time was now past.

His opinion is: "Almost everything is possible. But we just need time."