Figure 1.
Muscle fiber size of mice flown on board ISS and ground-based controls.
Exposure to microgravity for 91 days caused the reduction of the mean cross-sectional area (CSA) of soleus fibers, but not of extensor digitorum longus (EDL) fibers. Laboratory control (L) mice were housed in normal laboratory cages for 91 days (open bars, n = 3, data expressed as means ± SEM). Ground control (G) and spaceflown (F) mice, were housed in MDS (mice drawer system) payload for 91 days on ground (light blue bars; n = 1) and on board the International Space Station (dark blue bars; n = 1), respectively.
Figure 2.
MyHC isoform composition of muscles from mice flown on board ISS and ground-based controls.
A. Representative SDS-PAGE of myosin heavy chain (MyHC) isoform protein bands from EDL and soleus muscle lysates from ground control mice housed for 91 days in a normal laboratory cage (L) or in the MDS payload (G) and from the spaceflight mouse housed in the MDS payload on board ISS for 91 days (F). B. Mean content of MyHC isoform protein bands of laboratory controls housed in laboratory cages (open bars, n = 3, data expressed as means ± SEM), ground control, housed in MDS payload (light blue bars; n = 1), and spaceflight mouse in MDS payload on board ISS for 91 days (blue bars; n = 1).
Figure 3.
Fiber typing of muscles flown on board ISS for 91 days and ground-based controls.
Immunofluorescence fiber type identification by means of monoclonal antibodies specific for the different myosin heavy chain isoforms. The different fiber types were identified as described in Materials and Methods. Note the de novo appearance of type 2B fibers. The figure also illustrates the general atrophy of spaceflown soleus muscle fibers, compared to laboratory and ground controls.
Figure 4.
Fiber type composition of muscles from mice flown on board ISS and ground-based controls.
Fiber type compositions of EDL and soleus muscles from mice housed in normal laboratory cage (open bars; n = 3, data are expressed as means ± SEM), ground control housed in MDS payload (light blue bars, n = 1), and spaceflight mouse housed in MDS payload (blue bars; n = 1). The prolonged exposure to the microgravity environment caused a slow-to-fast rearrangement of fiber type composition in soleus muscle, but not in EDL.
Figure 5.
CSA of different fiber types in muscles from mice flown on board ISS and ground-based controls.
The CSA was measured in individual fiber types in normal laboratory cage controls (open bars, n = 3, data are expressed as means ± SEM), ground control in MDS payload (light blue bars, n = 1), and spaceflight mouse housed in MDS payload for 91 days on board ISS (blue bars, n = 1). A similar CSA reduction of about 35% was observed in all soleus fibers independently of the fiber type, whereas no changes were evident in EDL fibers.
Figure 6.
Mislocalization of NOS1 in muscle fibers from mice flown on board ISS.
A. Confocal immunofluorescence analysis of NOS1 localization in soleus and EDL muscle fibers from ground control mouse housed in a normal laboratory cage (LAB) and of the spaceflight mouse housed in the MDS payload (Flight). NOS1 mislocalization was seen in soleus muscle of the spaceflown mice, but not in EDL. B. The sarcolemmal (SL) to cytoplasmic localization of nitric oxide synthase-1 (NOS1) isoform was analyzed in soleus muscle fibers of control mice housed in a normal laboratory cage (LAB) or in the MDS payload (Ground) and in mice flown for 91 days on board ISS (Flight). *: P<0.05 vs. Lab and Ground.
Figure 7.
Variations in gene expression in soleus muscle induced by spaceflight.
Transcript levels were determined by real-time PCR for selected genes, classified on the basis of the functional role of the protein they encode. The numbers on the abscissa indicate the fold change in gene expression normalized for housekeeping gene. The bars in green show the variation between the spaceflown mouse (Flight) and LAB mice, whereas the bars in blue show the variation between Ground and LAB control mice.
Figure 8.
Variations in gene expression in EDL muscle induced by spaceflight.
Transcript levels were determined by real-time PCR for selected genes, classified on the basis of the functional role of the protein they encode. The numbers on the abscissa indicate the fold change in gene expression normalized for housekeeping gene. Numbers in the horizontal bars indicate the fold change when out of scale. The bars in green show the variation between the spaceflown mouse (Flight) and LAB mice, whereas the bars in blue show the variation between Ground and LAB control mice.