Typically, if an arthritis patient needs a new joint, surgery is performed and the damaged joint is replaced with an artificial, or prosthetic, joint. But a new study demonstrates that people may one day be able to "grow" new, natural joints created from their own stem cells.

A team of scientists at Columbia University, along with researchers from the University of Missouri and Clemson University, took laser scans of rabbits' hip bones. They reconstructed the contours using a "bio-printer" that yielded 3-D models of the hip bones made of substances designed to work with natural bone. The team injected growth factor into these bone "scaffolds," then placed them back inside the rabbits and watched as the rabbits' own stem cells migrated to the bone scaffolds and caused actual joints to grow. The rabbits soon were able to walk around and hop easily with their new joints, and stress tests performed after four months showed that the joints were fully functioning and virtually indistinguishable from the joints the rabbits had been born with.

The researchers were particularly encouraged by the results because the new joints were grown without the need for the stem cells to be removed from the rabbits' bodies. Their ultimate hope is for humans to be able to grow new joints to replace arthritic ones. Right now, people who need new joints usually are given ones made out of titanium or steel, which typically last 10 to 15 years. This is not long enough since more and more younger patients-who will probably live at least 15 more years-need joint replacement. Another complication is that patients who are quite elderly may not have enough bone to support the prosthetic replacements. Scientists are hopeful that joints grown out of natural material will be easier to work with and will last longer than artificial ones. For the 400,000 people who need joint replacement each year, the possibility of "growing their own" should be an exciting development.



Arthritis Foundation, www.arthritis.org;

Columbia University Medical Center, http://cumc.columbia.edu

National Institutes of Health, www.nlm.nih.gov