Subject: scientists develop a 3-d fabric to aid in joint cartilage repair

Spotlight on Research 2007

April 2007 (historical)

Scientists Develop 3-D Fabric to Aid in Joint Cartilage Repair

If the knees of your favorite jeans become worn and thin, patching them with a piece of fabric may provide a satisfactory fix, extending their life and delaying the need to replace them with a new pair. Someday doctors may be able to use a different kind of fabric to repair your own knees - as well as hips, shoulders and other joints - that wear out due to the common joint disease osteoarthritis (OA). Using a unique weaving machine of their own design, researchers supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) have created a three-dimensional fabric scaffold that could one day be used to patch damaged joint surfaces, allowing one's own stem cells to move in and repair the damage.

In OA, a disease that affects an estimated 21 million Americans, the smooth, elastic cartilage that normally covers and cushions the ends of bones where they meet to form a joint breaks down. For many, the result is daily joint pain, stiffness and disability. While medications can help control the pain of OA, nothing can stop the disease process. Nor is there an effective way to repair damage that has occurred.

Repair attempts in recent years have involved removing cartilage cells from patients and then growing them in a laboratory to form new cartilage. While the approach has had some success for small cartilage defects, it has a number of drawbacks, says Farshid Guilak, Ph.D., director of orthopaedic research at Duke University Medical Center and a senior member of the team that created the new fabric scaffolding. It requires at least two surgical procedures: one to remove the cartilage cells and another to replace them in the body. It can take several months to grow a piece of cartilage large enough to put back in a person.

Current techniques cannot be used to treat OA. Thus, the only sure fix for a severely damaged joint is to surgically remove it and replace it with a prosthesis, a procedure nearly one million Americans undergo each year. If further experiments are successful, however, this new fabric scaffold could be another, more desirable option.

In laboratory tests, the scaffold had the same mechanical properties as native cartilage. In the future, surgeons will likely be able to impregnate custom-designed scaffold with cartilage-forming stem cells (taken from a person's own fat tissue, for example) and biochemicals that stimulate their growth, and then implant them into a patient in a single procedure.

"We hope that this will be normal cartilage," says Guilak, whose team published their findings in the February issue of Nature Materials. "The whole idea is that it will hopefully be as strong as normal cartilage from the minute we make it because the strength comes from the scaffold, not from the new tissue that is formed. So we could take a long time to grow new tissue inside the body and use the scaffold to bear the load until it's grown." Fashioned of the same FDA-approved materials that are used for resorbable sutures, the scaffold eventually dissolves, leaving only strong new cartilage and hopefully delaying or even eliminating the need for joint replacement.

Most machines that produce fabrics weave one set of fibers that are oriented perpendicularly to another set of fibers to create a flat piece of fabric, like one might use to patch worn jeans, says Guilak. However, the machine developed by the Duke researchers adds a third set of fibers, which creates a three-dimensional product that can be made as thick as needed. "This allows us to mold it into the shape of the joint so we can cover the whole surface of the joint if we need to," says Guilak. Also, since the scaffold is woven material, there are tiny spaces where cartilage cells can nestle and grow.

NIAMS Director Stephen I. Katz, M.D., Ph.D., calls the resorbable 3-D material an important advance in bioengineering with the potential to help millions of Americans who have painful and debilitating OA. "If future studies go well, this technique could ease pain and improve function for many," he says, "enabling them to postpone or even prevent the need for a synthetic joint."

The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the Department of Health and Human Services' National Institutes of Health, is to support research into the causes, treatment and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about NIAMS, call the information clearinghouse at (301) 495-4484 or (877) 22-NIAMS (free call) or visit the NIAMS Web site at http://niams.cit.nih.gov

Additional funding for this research was provided by NASA and the Coulter Foundation.

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Moutos FT, Freed LE, Guilak F. A biomimetic three-dimensional woven composite scaffold for functional tissue engineering of cartilage. Nature Materials. 2007;6:162-167.