Bokhari, Rihana S.Metzger, Corinne E.Black, Jeremy M.Franklin, Katherine A.Boudreaux, Ramon D.Allen, Matthew R.Macias, Brandon R.Hogan, Harry A.Braby, Leslie A.Bloomfield, Susan A.2019-08-272019-08-272019-06-04Bokhari, R. S., Metzger, C. E., Black, J. M., Franklin, K. A., Boudreaux, R. D., Allen, M. R., … Bloomfield, S. A. (2019). Positive impact of low-dose, high-energy radiation on bone in partial- and/or full-weightbearing mice. NPJ microgravity, 5, 13. doi:10.1038/s41526-019-0074-3https://hdl.handle.net/1805/20588Astronauts traveling beyond low Earth orbit will be exposed to galactic cosmic radiation (GCR); understanding how high energy ionizing radiation modifies the bone response to mechanical unloading is important to assuring crew health. To investigate this, we exposed 4-mo-old female Balb/cBYJ mice to an acute space-relevant dose of 0.5 Gy 56Fe or sham (n = ~8/group); 4 days later, half of the mice were also subjected to a ground-based analog for 1/6 g (partial weightbearing) (G/6) for 21 days. Microcomputed tomography (µ-CT) of the distal femur reveals that 56Fe exposure resulted in 65-78% greater volume and improved microarchitecture of cancellous bone after 21 d compared to sham controls. Radiation also leads to significant increases in three measures of energy absorption at the mid-shaft femur and an increase in stiffness of the L4 vertebra. No significant effects of radiation on bone formation indices are detected; however, G/6 leads to reduced % mineralizing surface on the inner mid-tibial bone surface. In separate groups allowed 21 days of weightbearing recovery from G/6 and/or 56Fe exposure, radiation-exposed mice still exhibit greater bone mass and improved microarchitecture vs. sham control. However, femoral bone energy absorption values are no longer higher in the 56Fe-exposed WB mice vs. sham controls. We provide evidence for persistent positive impacts of high-LET radiation exposure preceding a period of full or partial weightbearing on bone mass and microarchitecture in the distal femur and, for full weightbearing mice only and more transiently, cortical bone energy absorption values.en-USAttribution-NonCommercial-NoDerivs 3.0 United StatesPhysiologyStructural biologyArticle