A single injection of recombinant human growth and differentiation factor (GDF-5) may induce recovery of intravertebral disc height (IVD), according to a study of New Zealand white rabbits presented Sunday at the annual meeting of the Orthopaedic Research Society in Chicago, Illinois.¹ A member of the bone morphogenic protein (BMP) family, GDF-5 is important for the development of the musculoskeletal system. Injections of this protein target the earliest stage of disc degeneration when cells are both viable and functional.

In the new 16-week study, researchers induced degenerative changes in rabbits by needle puncture, which resulted in a significant decrease in disc height. The animals were then given a single injection of either 10 ng, 1 mg, 100 mg, or a negative control of GDF-5. Rabbits in the 1 mg and 100 mg groups showed significant improvements in disc height. These two groups also showed improvement on magnetic resonance imaging exams conducted at 16 weeks. There was a slight positive effect seen in disc height early in the 10 ng group, but this was not sustained.

"A single injection of GDF-5 induced recovery of disc height in the IVD of rabbits with degenerative changes induced by needle puncture," says study presenter Koichi Masuda, MD, an orthopaedic surgeon at Rush Medical College in Chicago, Illinois. "Further research, including a long-term study that looks at histological, biochemical, and biomechanical mechanisms is needed," he says, adding that the effect of this protein on pain has not yet been addressed and will be "a future challenge."

Finding holds promise, but no definitive answers

Session co-moderators Jung Yoo, MD, an orthopaedic surgeon at Oregon Health and Science University in Portland, Oregon, and Leon Nesti, MD, PhD, assistant professor of surgery at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, and a resident in the department of orthopaedics and rehabilitation at the Walter Reed Army Medical Center in Washington, DC, tell CIAOMed that they are not completely convinced that GDF-5 is the answer. While GDF-5 may hold promise, Dr. Yoo says, "[there] is still a long way to go to get the IVD back to normal." Calling the new finding "an important baby step," Dr. Yoo says that "it is not likely that a single injection of GDF-5 will make it all better." He explains that while injections of other BMPs have met with limited results in joints and at fracture sites, the IVD is a protected space, so proteins remain in the surrounding space longer than if you had just injected them into the joint.

 "It's not a magic bullet," Dr. Nesti agrees.

Reference

1. Chujo T, Akeda K, An HS, et al. In vivo effect of recombinant human growth and differentiation factor-5 on the intervertebral disc. Presented at: 52nd Annual Meeting of the Orthopaedic Research Society; March 18–22, 2006; Chicago, Ill. Paper No. 14.