Adaptation of mouse skeletal muscle to long-term microgravity in the MDS mission
So far, the effect of microgravity on skeletal muscles has been examined in mice only after a
short-term (5-20 day) exposition. It has been observed that spaceflight has adverse effects on
muscles, including atrophy and partial shift of muscle fibres towards a faster, more glycolytic
phenotype.
The MDS experiment gave the first opportunity to study long time exposure to microgravity
effects on skeletal muscles. After the 91 day flight, muscle atrophy was observed in the fibres of
the soleus muscle, but this atrophy was only slightly increased when compared to shorter
periods in microgravity. Alterations were observed in the soleus and to a lesser extent in the
extensor digitorum longus (EDL) muscle, in particular with regard to slow-to-fast fibre transition
and ion channel activity.
Gene expression of the atrophy-related ubiquitin ligases was up-regulated in both soleus and
EDL muscles from flight mice, whereas autophagy (self-degradation) was in the control range.
In the same animals, various stress related genes were up-regulated in the EDL, but not in the
soleus. Overall, gene expression results suggested that EDL muscle may resist microgravity-
induced atrophy by activating compensatory and protective mechanisms and identified some
molecular targets for the development of countermeasures (Sandona 2012).
The impact of long-term exposure to space
environment on adult mammalian organisims:
A study on a mouse thyroid and testis
Human hormonal levels are known to change
during spaceflight, but the underlying
mechanisms are still unknown. To clarify this
point, thyroid and testis/epididymis from the
flight and ground control mice were analyzed
both morphologically and functionally.While Wt ground samples showed variable size
and spatial orientation, spaceflight animals had
a more homogenous thyroid tissue structure
with a reduction in the interior spacing. In
spaceflight animals, the follicular size in both
Wt and Tg mice was greatly varied.Structural modification correlated with altered thyroid functionality. Both Wt and Tg cells
stimulated with thyrotropin enhanced cAMP production in ground cells. After spaceflight a
more pronounced enhancement with Wt mice was observed. At the end of the MDS
experiment, the thyrotropin receptor and caveolin-1 in the thyroid were overexpressed in the
spaceflight mice.
MDS integrated inside the Double Payload Container.
ASI image.