5-Prime | Tissue Engineering Trends
What is tissue engineering? It's the use of engineering and life sciences principles and methods to obtain a basic understanding of structure-function relationships in novel and pathological mammalian tissues and using biological substitutes to restore, maintain, and improve function.
What's new? Researchers have developed products and therapies that include a combination of living cells and biomaterials to repair or replace diseased or damaged tissue. Some are also using stem cells for tissue regeneration. The Food and Drug Administration has approved tissue engineered cartilage and skin products. The next step, developing functioning organs, is in the works. Researchers have successfully implanted tissue-engineered bladders in dogs, for example, and have designed whole human bladders.
What's newer? "Tissue engineering historically grew out of materials science," says Sangeeta Bhatia, University of California, San Diego. Now, materials-based tissue engineering is beginning to merge with developmental biology to find ways of encouraging cells to grow and organize within an artificial system, she says. For instance, some are exploring ways to design bioreactors to mimic the environmental conditions experienced by tissues as they grow in the body.
What about using biomaterials? "What I'm very excited about is the idea of developing materials that allow us to control what combination of signals or information are available at a specific time for some duration," says the University of Michigan's David Mooney. At the Massachusetts Institute of Technology, researchers are developing polymers with shape-memory properties that more closely mimic the elastic properties of organs like the heart and lung.
What are some challenges? Tissue Engineering's Peter Johnson says that one obstacle is developing "plumbing and electrical systems" to create three-dimensional organs that behave like their biological counterparts--blood vessels, nerves, and lymphatic ducts. Another is the problem of immune rejection. Scientists, says Johnson, have not determined "that you can even theoretically overcome the specific immunity that would prevent us from creating a uniform-donor type of tissue in tissue engineering." Harvard Medical School's Anthony Atala says another obstacle is growing implantable cells outside the body in large quantities. Adult stem cells can be differentiated into various cell types, but their expansion ability is limited; embryonic stem cells don't have this problem, but they are immunogenetic and may be rejected unless immunosuppressed.