The Effects OF Simulated Weightlessness On Morphology And GDNF In Rats Dorsal Root Ganglia

Objective To observe the effect of simulated weightlessness on morphology and GDNF (Glial cell line-derived neurotrophic factor, GDNF) in rats DRG(dorsal root ganglia, DRG). To explore the difference of gender factors between male and female rats.Method The effect of simulated weightlessness on the myelin of DRG and the difference of gender factors:160 male and female Sprague-Dawley rats were randomly divided into two groups respectively:normal control (n=80,40 male and 40 female) and HU (n=80,40 male and 40 female). The hindlimb unweighting (HU) was used to simulate microgravity in rats. Four weeks later, the morphological changes of lumbar 5 DRG were detected with HE. MBP and Degen MBP were analyzed with immunohistochemistry. Myelin ultrastructural observation was performed. The difference between male and female rats was compared.The effect of simulated weightlessness on GDNF and the difference of gender factors:200 male and female Sprague-Dawley rats were randomly divided into two groups respectively:normal control (n=100,50 male and 50 female) and HU (n=100,50 male and 50 female). The simulated weightlessness model was created by hindlimb unloading (HU). After 4 weeks, nissl bodies in lumbar 5 DRG were observed by toluidine blue staining, and electron microscope method was performed to observe the ultrastructure of mitochondria, observation. The abundance of GDNF was determined by immunohistochemistry, western blot and RT-PCR analysis. The difference between male and female rats was observed.Results 1. HE staining showed that, in HU groups, the arrangement between cells in DRG were slightly loose, some ganglion cells and satellite cells separated. In NC (normal control) groups, the expression of MBP and IOD were higher than HU groups(male group P<0.01, female group P<0.001). The degeneration of the myelin and high IOD were observed in HU rats(P<0.001). In HU group, the structure of myelin is release and twisted.2. Nissl bodies were stained light, which was smaller and scattering distribution in HU rats. Mitochondria in HU group were swollen and deformed obviously. In HU group, the abundance of GDNF and IOD were significantly decreased (P<0.001). Western-blot showed that GDNF protein expression in HU groups significantly reduced than NC groups (P<0.001). HU groups displayed a lower expression of GDNF mRNA than NC groups (male group P<0.001, female group P<0.01).3. There was a significant difference between the male and female HU group (P <0.05).Conclusion1. Stimulated weightlessness can cause the damage changes and degeneration in myelin, which may prove that microgravity can lead to DRG damage.2. Stimulated weightlessness caused morphological changes in nissl bodies and decreased the abundance of GDNF in lumbar DRG neurons. Stimulated weightlessness caused the reduction of GDNF mRNA and protein expression. Stimulated weightlessness caused the damage changes in mitochondria.3. Different gender contributed to different results.