ABSTRACT
@#Objective:To study the molecular biology mechanisms of Wistar rats after spinal cord injury, and find out key microRNAs. Methods:A total of 15 Wistar rats were divided into control group (<italic>n</italic> = 3) and spinal cord injury group (<italic>n</italic> = 12). The latter group was divided into four hours, three days, seven days and 14 days subgroups, with three rats in each subgroup. Microarray 3.0 was used to investigate microRNA expression profiles of Wistar rats with spinal cord injury. Bioinformatics was used to predict microRNAs playing key regulatory roles, and to predict target genes. Reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR) was applied to detect the expression of miR-20a-3p. Western blotting was employed to detect the signal transducer and activator of transcription (STAT) 3 level. The correlation between target protein and microRNA expression trend in each group was analyzed. The key microRNA was inhibited in the neurons. The relationship between target protein expression and axon growth was observed with immunofluorescence. Results:In the rats with spinal cord injury, totally 658 microRNAs had changed at least once. In all the altered microRNAs, miR-20a-3p was upregulated obviously. It predicted that the target gene of miR-20a-3p was STAT3 via application of bioinformatics analysis. The expression trend of STAT 3 and miR-20a-3p in spinal cord was opposite. After the inhibition of miR-20a-3p, the expression of STAT3 in neurons was unregulated and axonal growth was extended. Conclusion:The upregulation of miR-20a-3p leads to downregulation of STAT3, and miR-20a-3p is one of the key targets in the treatment of spinal cord injury.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect on intramuscular connective tissue and passive range of joint motion by the stress produced in limb lengthening.</p><p><b>METHODS</b>An animal model of limb lengthening was established in the tibia of rabbits. Distraction was initiated at a rate of 1 mm/d and 2 mm/d in two steps respectively, and both proceeded until 10% and 20% of the tibia length was achieved. Muscle samples were harvested at the time when distraction ended and at the 4th week of consolidation after the distraction. Scanning electron microscope was applied to observe the morphological changes of the perimysium. The goniometer, which we made for this study, was used to measure the passive range of joint motion.</p><p><b>RESULTS</b>The collagen fibers were partitioned in bundles, crimped and interconnected closely and orderly. In the regime of 1 mm/d distraction with 10% lengthening, no apparent changes of the collagen fiber and passive range of joint motion was demonstrated. When tibia was increased to 20%, the crimped fibers showed a tendency of being straightened while the passive range of joint motion was reduced. The findings remained the same at the 4th week of consolidation. In the regime of 2 mm/d distraction with 10% lengthening, the crimped structure of the collagen fibers in the perimysium disappeared and the fibers were almost straightened. Additionally, the interconnection of the collagen fibers became loosened and interstice was presented among the fibers. At the 4th week of consolidation, the restoration to the original crimped structure was not completed. When the lengthening ratio was increased to 20%, the collagen fibers were straightened completely. This condition remained unchanged throughout all 4 weeks. The passive range of joint motion was reduced dramatically in the regime of 2 mm/d distraction.</p><p><b>CONCLUSION</b>The ultrastructure of perimysium and the passive range of joint motion in the regime of 1mm/d lengthening shows the condition closest to the normal ones. The regime of 2 mm/d lengthening may cause an apparent change in the ultrastructure of perimysium and passive range of joint motion.</p>