Measurements of Chemical and Mechanical Properties of Rats and Mice Bones under Simulated Space‐Like Environment

Abstract

Changes in elemental composition and mechanical properties of leg bones were determined following hind‐limb suspension (HLS) and irradiation of rats and mice. Tibia and Femur were bent with an applied force and corresponding elastic modulus determined. The bones were cross sectioned for elemental composition using Scanning Electron Microscopy with Energy Dispersive capabilities (EDX). The effect of microgravity on bones was evident after 4 days of suspension. There was a strong relationship between the compositional ratios of calcium, carbon, phosphorus and oxygen with the location on the leg. Two methods were used to measure mechanical strength of the bones; a LASER based bending setup (Cantilever) and a 3‐point bending setup with sensor to measure bending steps and stepping mechanism. Results showed that the femur bones had Young's modulus between 6 and 18 GN/m. For control groups, it was ~2.5 times larger than that for the HLS group. This clearly points to a less elastic nature of leg bones exposed to HLS. Also the trend of the stress versus strain graph (beyond the linear range) indicates a substantially lower breaking point for HLS leg bones. The results for tibia and femur provided similar conclusion. The elemental compositions in combination with mechanical properties indicated weakening of the bones under space‐like conditions of microgravity. These changes were even larger when radiation effects were taken into account. Supported by Arkansas Space Grant Consortium