Zero Gravity is a Factor that Induces Negative Changes in Myelinated Fibers of the Spinal Tracts

The development of hypogravitational motor syndrome is an essential negative consequence of weightlessness for humans; an important role in the pathogenesis of this syndrome is played by changes in axons of the spinal tracts. Myelinated fibers and transcriptome of the spinal cord were studied in mice exposed to hypogravity during a 30-day flight on a biosatellite. Morphometric analysis of myelinated fibers of the spinal tracts showed a decrease in the thickness of the myelin sheath. Analysis of spinal cord transcriptome revealed a decrease in the expression of genes involved in the myelination of nerve fibers. These results suggest that the processes of nerve fiber myelination are involved in the development of the hypogravitational motor syndrome under weightless conditions; the 7-day readaptation period was found to be insufficient for reversion of the negative changes in the myelinated fibers of the spinal cord.