Structural analysis of rat bone explants kept in vitro in simulated microgravity conditions

Skeletal abnormalities reported in humans and laboratory animals after spaceflight include cancellous osteopenia, decreased cortical and cancellous bone formation, aberrant matrix ultrastructure, decreased mineralization and reduced bone strength. Although considerable efforts have been made up to now to understand the skeletal effects of spaceflight for estimating health risk, our knowledge in this area is still largely incomplete. It is widely accepted that the mechanical strength of cancellous bone is related not only to the mineral content, but also to the trabecular micro-architecture arrangement. Three dimensional numerical analysis of bone volumes has been shown to be an important tool in this field. The Cell Method, a recently introduced numerical method, has been applied to the static analysis of microstructures obtained from the 3D reconstruction of micro-computed tomography scans performed at the Elettra Synchrotron facility in order to quantify micro-structural changes in trabecular bone. In the present study, the Cell Method model is used to compare the micro-tomographed structure of fragments of rats bone explants (tibial proximal epiphyses) harvested after 3 days and after 1, 2, 3 and 4 weeks of culture in the RCCS™ bioreactor, which represents the unique existing bioreactor operating on Earth’s surface capable to successfully reproduce, in vitro, optimal conditions for simulating a microgravity environment. Even if preliminary, our results seem to suggest that the exposure of tibial bone explants to the simulated microgravity conditions obtained by the RCCSTM bioreactor are consistent with skeletal changes observed after spaceflight.