May 15, 2013

Inner ear’s role in bone remodeling

The inner ear system that senses gravity and movement plays a role in bone remodeling – a finding that has clinical implications for space travel and for patients with inner ear disorders.

Microgravity conditions during space flight cause bone loss. Microgravity also alters the function of the inner ear’s vestibular system – the main sensory organ for gravity and movement. Florent Elefteriou, Ph.D., director of the Vanderbilt Center for Bone Biology, and colleagues explored a possible connection between bone remodeling and the inner ear by altering vestibular system function in both ears of rats and analyzing the skeletal response.

They report in the Journal of Bone and Mineral Research that vestibular lesions in rats generated bone loss, which was restricted to the weight-bearing bones and was associated with a reduction in bone formation, similar to what has been observed in astronauts. They found that the bone loss was accompanied by increased sympathetic nervous system outflow, and that it could be prevented with the beta-blocker propranolol – suggesting that beta-blockers may be useful for preventing bone loss during long-term space travel.

The findings reveal that the vestibular system combines with the sympathetic nervous system to regulate bone remodeling, and suggest that patients with vestibular pathologies may have fragile bones and a higher risk for fracture.

This research was supported by grants from Centre National d’Etudes Spatiales (CNES-2012-004884), ANR-09-BLAN-0148-07, Lower-Normandy Region, France and the National Space Biomedical Research Institutethrough NASA NCC9-58.

(Wellcome Images)