Elbow Grease

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Science Translational Medicine  22 Oct 2014:
Vol. 6, Issue 259, pp. 259ec180
DOI: 10.1126/scitranslmed.aaa0572

As we age, the cartilage lining our joints becomes rough and fibrillar, leading to increased friction, tissue damage, and osteoarthritis. Eventually, we may need a joint replacement. To halt this progression, many have turned to injecting a lubricant, such as hyaluronic acid (HA), which is a natural component of healthy cartilage and the synovial fluid, into the joint. HA may also have anti-inflammatory and antioxidant properties, but its therapeutic benefit is limited by rapid clearance from the site of injection.

To improve retention of HA in the joint, Singh and colleagues attached an HA-binding peptide to the surface of cartilage via a polymer spacer and a collagen-binding peptide. This noncovalent surface treatment captured free HA from simulated synovial fluid and drastically reduced the friction between cartilage tissue samples ex vivo. Remarkably, the lubricating effects of the HA-binding strategy were even more pronounced when used to treat diseased cartilage that was isolated from osteoarthritic patients undergoing total joint replacement surgery. The therapeutic potential of this strategy was validated in vivo by injecting a mixture of HA and the HA-binding polymer into the joints of rats. HA was retained in the joints for up to 3 days, compared with 6 hours for HA without the polymer. Toward the treatment of dry eye disease—another condition lacking lubrication—the HA-binding polymer was packaged into an eye drop solution. HA binding was then observed on the sclera, conjunctiva, and cornea of rabbit eyes ex vivo. Water retention was also improved on the surface of contact lenses coated with the HA binding peptide compared with untreated lenses.

The safety of the HA-binding polymer has not been evaluated, and the long-term benefits of the treatment have yet to be revealed. Nevertheless, modifying tissue surfaces may be a simple yet effective way to treat osteoarthritis as well as dry eye disease and other ocular conditions.

A. Singh et al., Enhanced lubrication on tissue and biomaterial surfaces through peptide-mediated binding of hyaluronic acid. Nat. Mat. 13, 988–995 (2014). [Abstract]

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