This CNN headline was too good to pass up! : Mouse Spotted on Mars?
Given that Mouse Specifics, Inc. is now internationally recognized as a leader in novel in vivo life sciences instrumentation, is it possible that perhaps our innovative technology is making its way throughout the solar system? Is that the ECGenie set up in the HAB in The Martian, director Ridley Scott’s film adaptation of the best selling book by Andy Weir?
All kidding aside, our DigiGait technology has been applied to mice in a Martian gravity environment, to evaluate how low gravity may affect gait kinematics. Ellam et al. (1) studied gait in BALB/c mice at a treadmill speed of 14 cm/s at five different weight-bearing levels (20%, 40%, 60%, 80%, and 100%) (1). With decreased weight bearing, gait changed modestly with a longer swing phase and shorter stance phase and a concomitant decrease in stance/swing ratio for the hind limbs only. Their partial unloading model largely preserved normal gait to demonstrate that bone and muscle loss are linearly related to the degree of unloading (1). Yet, botulinum -toxin-induced muscle inhibition, combined with hind limb unloading, has an even larger detrimental effect on the skeleton (2), underscoring the direct effect of muscle on bone (1,2).
Video: Hind limb suspension of B6 mouse, with forelimb stepping on DigiGait treadmill, and fictive stepping of the hind limbs. Canu et al. showed that two weeks of chronic hind limb suspension induces plastic modifications of the central networks of neurons implicated in the locomotor command (3).
In contrast, intermittent applied mechanical loading induces subchondral bone thickening (4). Poulet et al. demonstrated that repetitive loads, applied directly across articular surfaces, can produce bone thickening in intact joints and that load-induced subchondral bone thickening is further accentuated in regions underlying cartilage lesions (4). Gait analysis via DigiGait indicates that altered compensatory limb use underpins subchondral bone thickening and the accrual of underlying epiphyseal bone (4). One might think that arthritis symptoms for those folks heading out to Mars in 2026 might be alleviated. Watching Mark Watney [deftly played by Matt Damon] prance around Mars gives us a pretty good indication that gait per se is not overtly affected. Yet, taken together, the recent murine studies suggest there may not be too many Martian musculoskeletal benefits for folks exploring the red planet.
References:
- Ellman R, et al. Partial reductions in mechanical loading yield proportional changes in bone density, bone architecture, and muscle mass. J Bone Miner Res. 2013; 28(4):875-85. Article
- Warden SJ, et al. Reduced gravitational loading does not account for the skeletal effect of botulinum toxin-induced muscle inhibition suggesting a direct effect of muscle on bone. Bone. 2013; 54(1):98-105. Article
- Canu MH et al. Fictive motor activity in rat after 14 days of hindlimb unloading. Exp Brain Res. 2001; 139(1):30-8. Abstract
- Poulet B, et al. Intermittent applied mechanical loading induces subchondral bone thickening that may be intensified locally by contiguous articular cartilage lesions. Osteoarthritis Cartilage. 2015; 23(6):940-8. Article