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.