MDS mission pre-flight study. Characterization of skeletal muscles of wild type and osf-1 transgenic mice kept on ground in the mice drawer system.

A group of OSMA investigators working on skeletal muscle is taking advantage of the planned ASI mission regarding the Mice Drawer System (MDS) developed by Alenia-Space, which will host mice on board the International Space Station. The first MDS mission is aimed at identifying countermeasures to prevent osteoporosis by means of transgenic mice over-expressing osteoblast stimulating factor-1 in a 100-day long space flight (R. Cancedda program). In this context, ASI has promoted a tissue sharing program involving the OSMA muscle atrophy group. Preliminary pre-flight experiments have been performed on mice kept on ground in the MDS for 20 days. Ongoing analyses of muscle tissues obtained from these mice aim to determine i) the effects of the stringent MDS conditions on skeletal muscle and ii) the effect, if any, of the bone transgene on skeletal muscle properties. The study includes hematoxylin-eosin and SDH staining of muscle serial sections, to determine the cross-sectional area of individual fibers and evaluate mitochondria content. Fiber type composition is determined on muscle sections with specific monoclonal antibodies, while MyHC isoform expression is evaluated on muscle lysates by SDS-PAGE. Total RNA is isolated from contralateral muscles to study gene expression by real time PCR, and the results validated by parallel proteomic analyses. Genes of interest include those encoding ion channels, the expression of which is altered by muscle disuse in models of simulated microgravity, thereby representing easy therapeutic targets. Genes involved in IGF-1 signaling and protein degradation will also be examined.