The Treatment Of Forearm Motor Dysfunction Following Central Nerve System Injury With The Contralateral C7Nerve Transfer:an Experimental Study In Rat

Part1A comparison of motor dysfunction between different traumatic brain injury models:an experimental study in ratsObjective The purpose of this study was to develop a rat model for the long-term longitudinal study with motor weakness after surgical brain injury and to find an adequate behavior test for the application of the model.Methods Thirty-two clean female Sprague-Dawley (SD) rats were involved in this experiment and randomly divided into four groups:(A) the group with mild controlled cortical impact (CCI);(B) the group with moderate CCI;(C) the group with severe CCI; and (D) the group with extensive unilateral motor cortex ablation. Behavioral tests such as the skilled reaching task and limb-use asymmetry test were employed to evaluate the injured forelimb motor function recovery at different point after the injury. Furthermore, the brain morphology with HE stain was used at the end of12weeks post-surgery to identify the histopathologcal change.Results The results demonstrated that all the rats showed various degrees of motor deficits in the injured forelimb while reaching and grasping the food at2weeks after the TBI, the rats in Group C and D failed to complete the extension movement. There was statistically decreased use of the right forelimbs at this point in the limb-use asymmetry test, and when the rats moved along the cylinder wall, the sliding score of the injured forelimb increased. However, all the rats exhibited obvious tendency of spontaneous recovery in skilled reach and the limb-use preference disappeared gradually with the passage of time in the asymmetry test. At the end of12weeks in this study, not only the rats in Group A, also Group B achieved the successful reaching scores very close to the baseline before injury, their scores were recorded as (78±4)%and (74±3)% respectively. However, Group C and D still showed severely affected forelimb function in skilled reaching task at the same time. Significant differences could be obtained among the four groups (P<0.05), but not between Group A and B, as well as Group C and D (P>0.05). By the end of12weeks after TBI, no asymmetry in forelimb use could be observed in Group A and B, and the forelimb activity (FLA) and the sliding score of the injured forelimb achieved very close to the preoperative performance. Sever motor deficit could be observed in both Group C and D in spite of the spontaneous recovery, while the rats in Group C performed superior to the Group D in the forelimb activity (FLA) and the sliding score. Significant differences could be obtained among the four groups (P<0.05), but not between Group A and B, as well as Group C and D (P>0.05). The gross examination from the coronal sections showed a cavity in the frontal cortex in all the rats as expected, regardless of different injuries to the four groups. Both Group C and D showed the great lesion volume and the survival announced the (81.15±4.15)%and (80.66±5.36)%of the total brain respectively, no significant difference could be recorded. In contrast, Group A and B showed smaller lesion volume, and the survival accounted for the (96.12±7.68)%and (93.24±4.41)%of the total brain respectively. Significant group differences could be recorded among the four injured groups (P<0.05).Observation under the microscope of the coronal sections with H&E staining exhibited gliosis reaction along the resection margin in all the groups.Conclusion Both models with severe controlled cortical impact (CCI) injury and extensive unilateral motor cortex ablation developed reproducible and long-lasting motor weakness, and were suitable for the long-term longitudinal study. Not only the skilled reaching task but also limb-use asymmetry test was sensitive and objective assessments for slight neurological deficits after brain injury. Part2The cortical plasticity and behavioral changes after traumatic brain injury:an experimental study in ratsObjective To observe the expression of microtubule associated protein-2(MAP-2) and synaptophysin (SYN) in central nervous system (CNS), as well as the behavioral changes of rats with traumatic brain injury (TBI) and provide a theoretical basis for study on the mechanism of regeneration and repair of neuron after TBI as well as clinical treatment of motor deficit in the late posttraumatic brain injury.Methods Eighty clean female Sprague-Dawley (SD) rats were involved in this experiment and randomly divided into10groups,8rats in each group. In addition to the normal control group, nine additional groups were prepared according to2,4,6,8weeks and3,5,7,10,12months after the extensive unilateral motor cortex ablation. Behavioral tests such as the skilled reaching task and limb-use asymmetry test were employed to evaluate the injured forelimb motor function recovery at different point after the injury. Furthermore, the immunohistochemical method were used to observe the expression of microtubule associated protein-2(MAP-2) and synaptophysin (SYN) in the frontal cortex of the normal and model rats.Results1. Behavioral test:The results demonstrated that all the rats showed sever motor deficits in the injured forelimb while reaching and grasping the food at2weeks after the TBI. The motor function of the palsy forelimb recovered spontaneously with the passage of time. By the end of5months, the function recovery tend to be stable, and the successful reaching scores achieved (31±4)%, which was significantly lower than the normal control (P<0.05). Differences were observed among all the experimental groups (P<0.05), but not among the5、7、10、12months group (P>0.05). The same recovery tendency was observed in the limb-use asymmetry test. The forelimb activity (FLA) of the injured forelimb was0.982+0.063, and the sliding score was0.341±0.033, both showed statistical difference compared to the normal control(P<0.05). The rats in the3months group achieved the best recovery, the statistical differences could be recorded among all the experimental groups (P<0.01)but the5、7、10、12months group (P>0.05).2. The immunohistochemistry test:The expression of MAP-2in the peri lesion area increased significantly and reached a peak value at2weeks after the TBI, and the expression intensity was (7.24±0.63)%, which significantly increase compared to the normal control (P<0.05) The expression of MAP-2decreased subsequently and no statistical difference was recorded among all the rest groups and the normal control group (P>0.05). Significant group differences could be recorded between the2weeks group and other experimental groups (P<0.05). There was the same tendency of expression of SYN in the peri lesion area, with the peak value of (4.7±0.24)%at2weeks after the TBI. The difference was not statistically significant compared to the normal control, in spite of the higher value of expression (P>0.05). Decreased expression of SYN in the frontal cortex could be observed, and no statistical differences were recorded among all the groups (P>0.05).Conclusion1. To some extent, spontaneous recovery of motor function of the injured forelimb after the extensive unilateral motor cortex ablation, although the recovery was limited and uncompleted. The contralateral motor cortex participated in the control of the injured forearm through the ipisilateral pathway after the TBI.2. Significant increased expression of MAP-2, as well as SYN could be observed early after the injury, with the peak value at2weeks post-trauma, and decreased subsequently. Functional reorganization occurred in the peri lesion cortex after the injury, both MAP-2and SYN played an important role in the neural regeneration and synaptogenesis. Part3The treatment of upper extremity motor dysfunction following central nerve system injury with the contralateral C7nerve transfer:an experimental study in rat Objective The objective of this study was to investigate the feasibility of contralateral C7nerve transfer in the treatment of dysfunction in the forearm following central nerve system injury in rodent models and provide a theoretical basis for study on the clinical treatment of motor deficit in the late posttraumatic brain injury.Methods Eighty clean female Sprague－Dawley (SD) rats were involved in this experiment and randomly divided into10groups,8rats in each group. In addition to the normal control group, all the experimental rats accepted the extensive unilateral (left) motor cortex ablation and contralateral (left) C7nerve transfer to the paralyzed (right) side. And the rest nine groups were prepared according to2,4,6,8weeks and3,5,7,10,12months after the operation. Behavioral tests such as the skilled reaching task and limb-use asymmetry test were employed to evaluate the injured forelimb motor function recovery at different point after the injury. And the latency and maximum amplitude of compound muscle action potential (CMAP) were recorded from the triceps brachii muscle with the technique of neurological electrophysiology. Nerve histological study were carried out to assess the number and function of the regenerated myelinated nerve fibers after the transfer of contralateral C7nerve. Furthermore, the immunohistochemical method were used to observe the expression of microtubule associated protein-2(MAP-2) and synaptophysin (SYN) in the frontal cortex of both sides in the normal and model rats.Results1. Behavioral test:Sever motor deficits in the injured forelimb of the experimental rats could be observed at2weeks after the operation, and spontaneous motor recovery occurred with the passage of time. By the end of7months, the successful reaching scores by the palsy forelimb achieved(61±5)%, and statistical difference could be observed when compared to the normal control (P<0.05). The statistical differences could be recorded among all the experimental groups (P<0.01) but the5、7、10、12months group (P>0.05). The forelimb activity (FLA) of the injured forelimb of the rats in the7months group achieved very close to the preoperative performance, and no significant difference were observed between the experimental group and the normal control (P>0.05). However, the rats in the7months group showed significant higher sliding score compared to the normal group (P<0.05). Differences were observed among all the experimental groups (P<0.05) in both FLA and the sliding score, but not among the5、7、10、12months group (P>0.05).2. Neurological electrophysiology and nerve histological study:No CMAP were recorded from the right triceps brachii muscle at the end of2weeks post operation. And the recorded CMAP amplitude increased in all the experimental groups with time, while the latency of the CMAP response shortened gradually. At7months after the operation, the amplitude recovery rate and latency delaying rate of CMAP of the right triceps brachii muscle were75.65±6.67%and119.76±8.34%, respectively. There was a significant difference in the respective measures of the mean CMAP amplitude between experimental and normal control group (P<0.05), but not in the measurements of latency of the CMAP (P>0.05). Histological analysis of the C7nerve segments distal from the site of the anastomosis showed limited new nerve fibers with small diameters2weeks after the operation. The total number of myelinated axons increased with time and reached the peak value at the end of7month post operation. Differences were observed among all the experimental groups (P<0.05), but not among the5、7、10、12months group(P>0.05).3. The immunohistochemistry test:The expression of MAP-2in the peri lesion area increased significantly and reached a peak value at2weeks after the TBI, and decreased subsequently. By the end of5months after the operation, the expression of MAP-2in the motor cortex contralateral to the injury, and achieved the peak in the7months group. Significant group differences could be recorded among all the experimental groups (P<0.05). There was the same tendency of expression of SYN in the peri lesion area, at2weeks after the TBI. And the expression of the SYN increased in the contralateral motor cortex at3month post operation, while the peak value was also detected in the7months group. Significant group differences could be recorded among all the experimental groups (P<0.05)Conclusion1. The expression of MAP-2, as well as SYN, represented the "double peak" in the frontal cortex in the rats accepted the extensive unilateral motor cortex ablation and the contralateral C7nerve transfer.2. The transfer of the contralateral C7nerve indued the reorganization of the motor cortex contralateral to the injury, which reinnervated the palsy forelimb through the reinforced ipsilateral pathway and the new peripheral pathway by the contralateral C7transfer.3. The transfer of the contralateral C7nerve from the healthy side is an effective method for the treatment of the forearm dysfunction following central nerve system injury in rats.