HANNOVER, Germany ¿ Nearly 100 experts met last month to discuss tissue engineering and regenerative medicine at the Second Transdisciplinary Conference on Principles and Perspectives in Regenerative Medicine during the international biotechnology trade fair, Biotechnica 2001.

¿The goal of our congress is presenting technologies, which enable reconstitution and imitation of natural structures,¿ said Augustinus Bader, of the University of T|bingen in Germany.

Reconstituting damaged tissue by use of a patient¿s own cells is becoming clinical reality. Bader¿s group, for example, has developed artificial heart valves and vessels that are in preclinical trials. Other examples of tissue engineering projects close to clinical application or available for therapy involve blood vessels and skin.

The next step is to develop more complex structures, Bader said. ¿In Germany, there are several groups in good shape for international competition in this field.¿

Buddy Ratner, of the University of Washington in Seattle, leads a network of scientists who plan to engineer a chunk of living heart muscle in the next five years. Such a patch could be used for replacement of damaged tissue in heart after myocardial infarction. In a 10-year project, the goal is ¿creating a fifth [heart] ventricle, a fifth chamber for the heart that could be used when the left ventricle is failing in myocardial insufficiency,¿ Ratner told BioWorld International.

Surgical and biological approaches are readily available. But there are obstacles.

¿The normal cells of the heart do not grow,¿ Ratner said. Scientists in his network investigate whether cells taken from a heart biopsy could be reverted to cells with growth potential. ¿This would be the ideal, but nobody knows quite how to do this.¿

Other obstacles in the project include the strength of the tissue-to-be and blood supply, for example. ¿The heart muscle has an extreme need for oxygen and an extreme need for vasculization. One can grow cells, but when the cells reach a high enough density, they need the blood vessels to come in,¿ Ratner explained.

Vladimir Mironov, chief scientific officer of Charleston, S.C.-based Cardiovascular Tissue Technologies, aims at generating artificial organs by a prototyping printing process. He presented a technology called ¿organ printer.¿

¿Instead of ink we use an aggregate of stem cells, called spheres. Instead of paper we use a thermo-sensitive gel,¿ he said. ¿We first printed a very fine circle layer of this gel [in its liquid phase], solidified it, and then printed the cells on this circle.¿ So the new biological structure, the organ-to-be, was built up, layer by layer, of gels and cells. ¿At last we received a 3-dimensional tube incorporated in gel.¿ The cells after that need some time for integration, need to be perfused, supplied with growth factors, and exercised mechanically, Mironov explained. ¿After the cells¿ integration the gel can be removed by liquifying it,¿ he said.

Mironov told BioWorld International that he generated a tubular structure, which he considers the prototype for organs like the heart, esophagus and vessels. He currently uses stem cells derived from liposuction. He received very thin tubular monolayers of endothelial cells, he said, and the next steps planned will include tubes from smooth muscle cells, myocardial cells.

Other subjects of the congress included hepatic tissue engineering, blood vessels, skin, cartilage and bone repair.

The worldwide market potential of tissue engineering according to different studies is estimated at $20 billion to $40 billion, said Robert Simmoteit, director of biotechnology at Jostra AG, a specialist in extra corporal circulation devices in Hirrlingen, Germany. ¿Considering segments like skin, liver, blood vessels, bone and cartilage, the market potential is US$1.5 billion to $2 billion,¿ he said. ¿That is big enough for industry to invest in this field,¿ he said, adding that tissue engineering in Germany and around Europe is at a highly advanced stage, competitive to the U.S. ¿We now need start-up companies driving products quickly into clinical trials,¿ he said.

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