Doctors try to kick-start growth of knee cartilage
 By Lauran Neergaard
 August 22, 2006

 WASHINGTON - Doctors are testing new ways to spur cartilage to
 regrow in damaged knees, from implanted "cartilage plugs" to
 injections of bone-marrow stem cells.

 The need is huge. Knees are the joint most likely to go bad, and the
 cartilage that cushions them has only a limited natural ability to
 repair itself.

 The question is how to unlock that ability and give it a boost.
 The potential new options are being tried first in people who
 injured their knees and thus need small amounts of cartilage to
 regrow. If they work, the techniques one day might offer hope for
 arthritis sufferers, whose cartilage erodes.

 Most eagerly anticipated: the first clinical trial using stem cells
 from donated bone marrow to try to regenerate the knee's shock
 absorber, a cartilage pad called the meniscus.

 Meniscus injuries are common, and not just among athletes. Because
 the pad weakens with age, a simple wrong step can leave an older
 person with the painful tear. About 800,000 Americans a year have
 part of the meniscus surgically removed, to relieve pain when jagged
 edges won't heal.

 Stem cells are building blocks for tissue. Mesenchymal stem cells
 are a type of adult stem cell that live in the bone marrow and can
 transform into cartilage-forming cells called chondrocytes. Mixing
 these stem cells with a knee-lubricating fluid helped the meniscus
 regrow in goats. Will it work in people?

 Researchers enrolled 55 patients who had about half their meniscus
 removed. About a week after that surgery, each participant received
 a single injection - either a dummy shot or one containing millions
 of mesenchymal stem cells.

 With a high-powered MRI machine, scientists now are measuring each
 patient's remaining meniscus, for signs of regrowth.

 "No one's ever looked at the meniscus in terms of volume," says Dr.
 C. Thomas Vangsness Jr. of the University of Southern California,
 lead researcher for the study funded by stem cell producer Osiris
 Therapeutics. "It's very interesting what I'm seeing."

 While he reports no safety problems, he can't say yet if the stem
 cells are working because the study still is blinded, meaning
 researchers don't yet know which patients got the real injections.
 Initial results are due in October.

 "It's very, very exciting research," says Dr. David C. Johnson, an
 orthopedic surgeon and sports medicine specialist at Washington
 Hospital Center in the nation's capital, who is closely watching the
 work.

 But, "it's like The Sorcerer's Apprentice," he cautions. "You want
 to make some cartilage cells. Well, how do you turn it off? You
 don't want too many. . . . We're sort of walking a tightrope."

 The meniscus isn't the knee's only cartilage. A tougher kind called
 articular cartilage coats the ends of bones so that they glide past
 each other smoothly instead of grinding - and if stem cells can
 regrow the meniscus, trying it on this cartilage is the logical next
 step, Johnson says.

 Articular cartilage is the kind that wears away in arthritis, making
 total knee replacements the only option once a patient's pain
 becomes too severe. Doctors have few surgical options for injuries
 to this cartilage, either, mostly trying a procedure that
 essentially roughs up the bone to stimulate natural repair.

 Enter cartilage plugs, tiny scaffolds that can be inserted into the
 gap when a blow to the knee - from a car crash, fall or sports
 injury - kills a chunk of articular cartilage.

 The Food and Drug Administration initially approved the TruFit plugs
 as a filler for gaps in bone, not cartilage. But the plugs,
 officially known as bone-graft substitutes, have an almost magnetic
 ability to attract chondrocytes, explains Dr. Preston Wolin, sports
 medicine chief at the Neurologic and Orthopedic Institute of
 Chicago.

 First, doctors started transplanting some of the patient's cartilage
 from a less-stressed part of the knee into the harder-working
 injured spot, and using the plug to heal the weaker donor site.

 That is "really robbing one part of the knee to pay the other part,"
 says Wolin. So now he and a number of surgeons use the plugs to fill
 the direct injury.

 Washington's Johnson is skeptical that the plugs produce cartilage
 as sturdy as the original.

 But Wolin says he's getting good results, with healing in a few
 months - faster than some other cartilage-repair surgery.

 "This is not a substitute for knee replacement," he cautions,
 because the plugs are only for small injuries, not arthritis'
 widespread cartilage loss.

 Manufacturer Smith & Nephew, which just bought the plugs' original
 maker, is funding early-stage research to see if the plugs could be
 expanded to cover a larger surface.

... Husband:  A handyman with bedroom privileges.