Remedies to bone loss in space may benefit Earth patients first

November 28, 2001

HOUSTON - Spinal cord injury patients may be the first to benefit from studies to reduce bone loss in astronauts on long missions.

"These two groups, astronauts and paraplegic patients, experience bone and muscle loss in the same areas - the lower part of the trunk and the legs," said Dr. Jay Shapiro, bone loss team leader for the National Space Biomedical Research Institute (NSBRI). "The rate of bone loss in space is almost as profound as it is in spinal cord injury patients."

Through an NSBRI-funded study at the National Rehabilitation Hospital in Washington, Shapiro is testing a medication, zoledronate, to see if it can inhibit bone loss in spinal cord injury patients. The drug, produced by Novartis, is a bisphosphonate, a class of medication known to inhibit the activity of cells responsible for reabsorbing, or eating up, bone. Bisphosphonates are commonly used to slow down bone loss related to osteoporosis.

"Throughout our lives, new bone is formed and old bone is absorbed," said Shapiro, a professor of medicine at the Uniformed Services University of the Health Sciences. "Bisphosphonates inhibit the cycle of bone breakdown that occurs, keeping you from losing as much and allowing the bone-forming processes a little more breathing room."

More time for bone growth is crucial for persons experiencing acute bone loss.

"Fracture risk is extremely high in adults and children immobilized by spinal cord or brain injuries, strokes, neuromuscular disorders, or developmental disorders like spina bifida and cerebral palsy," Shapiro said. "Once you lose muscle function, you will lose bone. This is true in space for astronauts because their muscles no longer have to function against gravity."

Weakened bones would be a great risk for astronauts exploring other planets or returning to Earth after long stays on the International Space Station.

In the one-year study, patients will receive zoledronate intravenously at widely spaced intervals. Participants and physicians will not know if the patient is receiving the medication or a harmless substitute.

"This particular medication is many times stronger than the treatments in common use," Shapiro said. "Current intravenous treatments must be taken every two-to-three months, and oral medications of this type are taken daily."

Measurements taken throughout the study will assess the medication's effectiveness and side effects. Patients will undergo bone density measurements, computer measurements of muscle and of bone structure and geometry, and blood and urine biochemical analyses.

"If we can show that the medication inhibits bone loss in spinal cord injury patients, then it is likely that it would be effective in space," Shapiro said.
Shapiro's work is part of the NSBRI's research effort involving scientists looking at health issues relating to long-duration space flight. Benefits to similar conditions on Earth - muscle wasting, sleep loss, radiation exposure -- are also being pursued. The NSBRI is funded by NASA.

The NSBRI's consortium members include Baylor College of Medicine, Brookhaven National Laboratory, Harvard Medical School, The Johns Hopkins University, MIT, Morehouse School of Medicine, Mount Sinai School of Medicine, Rice University, Texas A&M University, University of Arkansas for Medical Sciences, University of Pennsylvania Health System and University of Washington.

National Space Biomedical Research Institute

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