Today's News

Friday, February 23, 1996

Growth factors offer promise for treating orthopaedic problems

Growth factors may one day provide important nonsurgical treatments for orthopaedic conditions, a panel of researchers said Thursday at a press conference held prior to a symposium sponsored by the Orthopaedic Research Society and the Academy.

"Orthopaedic diseases traditionally have been approached from a surgical standpoint," said Stephen B. Trippel, MD, associate professor of orthopaedic surgery, Harvard Medical School, and associate orthopaedic surgeon, Massachusetts General Hospital. "Now we have to adjust our perspective and see disease from the level of the cell."

Because they regulate cell behavior, growth factors may prove valuable in the treatment of a number of orthopaedic diseases. "They may give us the ability to directly manipulate the actions at the site of the problem - in the bone, in the cartilage, in the fracture site, in the growth plate - so that we can prevent orthopaedic problems," he said.

Skeletal growth deficiencies are one area of potential usefulness for growth factors, according to Ronald G. Rosenfeld, MD, professor and chairman, department of ortho-paedics, Oregon Health Sciences University. Dr. Rosenfeld described a study in which recombinant insulin-like growth factor 1 (IGF-1) was given to a population of children in Ecuador with growth hormone receptor deficiency.

In a clinical trial, IGF-1 was found to stimulate growth in these children. "In other words, one can bypass the need for growth hormone by giving IGF-1," Dr. Rosenfeld said.

This success raises the possibility of using IGF-1 to treat children with a wide variety of growth disorders, but it also has a number of other biological effects, including regulation of metabolism and new bone formation, he said.

"Studies are now beginning with IGF-1 to see if it can not only stimulate growth in children with this rare disorder but also reverse many of the metabolic disorders associated with growth hormone or IGF deficiency in adults," he said.

Growth factors also offer promise for treating patients with fractures. According to Mark E. Bolander, MD, professor of orthopaedics at the Mayo Medical School and a consultant in orthopaedic surgery at the Mayo Clinic, repair of nonunion fractures demands this approach.

"Good fracture treatment requires an understanding both of the biomechanics of the fracture and the biology of the fracture, which is something that really we have to learn quite a bit about," he said.

Studies are indicating that the normal healing process is driven by growth factors, which control the cascade of cellular events that are required for healing, Dr. Bolander said.

"So we are investigating the potential uses of growth factors therapeutically to influence this cascade, both to try to augment the healing process in normal fracture repair and to use these growth factors specifically to treat problems where there is some defect in the cascade of healing responses," he said.

Growth factors also may prove effective in stimulating repair of articular cartilage. Although hip and knee replacement surgery has proven very successful for many patients, the finite life of the replacements means their utility is limited, especially for younger patients. But use of growth factors may offer a way to restore absent cartilage, said Richard D. Coutts, MD, medical director and professor of orthopaedics, University of California at San Diego.

"There is now a glimmer of hope that in fact we may be able to influence metabolic processes and affect healing of cartilage" using growth factors, Dr. Coutts said.

Although physicians once thought cartilage could not reproduce itself to heal defects, cartilage cells are now know to be capable of division. "The problem is that these cells are trapped in the tissue and cannot migrate to the site of injury to effect a repair," Dr. Coutts said.

But three growth factors - IGF-1, fibroblastic growth factor and TGF-beta - have been shown to have effects on cartilage cells. They "turn on the machinery of cartilage cells to produce more matrix than they would under ordinary circumstances," he said.

Taking the most optimistic perspective on the future of arthritis treatment, Dr. Coutts said, "we may be able to treat it chemically rather than surgically. That may be a little farfetched, but there certainly are lesions for which we can use these growth factors to great benefit. The prospects for the future really are quite bright."

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Last modified 27/September/1996