| Objectives:To explore the potential protective effects of L-triiodothyronine(L-T3)on a mouse model of excitotoxic brain injury induced by ibotenate (lb). By detecting changes of the expressions of Olig2 and SOX10 in both transcriptional and translational level before and after L-T3 treatment,and to investigate the possible mechanisms of L-T3 on neuroprotection and to provide theoretical bases for L-T3 as a future intervention in periventricular leukomalacia of premature infants.Methods: 240 ICR mice of both sexes from different litters, weighing 3.0-3.6g,were selected for experiments on postnatal Day 5 (P5) and fed by their own mothers after operation. They were randomly and medially distributed into 4 groups: control group (n=60), sham surgery group (n=60),lb model group (n=60) and T3 treatment group (n=60). The mice were sacrificed by decapitation at 24, 72,168 and 336hours after operation respectively. The paraffin slices of the injured brain were observed with H-E staining, and sizes of the lesions in the impaired hemispheres were measured. The mRNA expressions of Olig2 and SOX10 were detected via Q-PCR.Frozen sections of the injured hemispheres were measured with immunofluorescence histochemistry to detect the proteinic expressions of Olig2 and SOX10. In the end, we studied the protein expression of Olig2 and SOX10 through Westen-Blot.Results:1. Pathological ChangesNo cystic lesions in brain tissue of mice were observed in sham surgery group and control group in this experiment. Cystic lesions were observed at 24,72 ,168 and 336 hours after operation in lb model group and the diameters of the cysts increased with time which were 180.00±42.42mm, 450.00±30.00mm,600.00±73.48mm and 420.00+42.43 mm, respectively. T3 treatment group also showed cystic lesions at 24, 72 ,168 and 336hours after operation, which were 165.00±25.98mm,300.00±42.43mm,180.00±42.43mm and 165.00±25.98mm,respectively. No comparable difference of lesion size was found between T3 treatment group (165.00+25.98 mm) and Ib model group (180.00+42.42 mm) at postoperative Hour 24. Significant difference was observed between T3 treatment group( 300.00±42.43mm) and Ib model group (450.00±30.00mm) at 72 hours after operation(p<0.01). At postoperative Hour 168 and 336, campared with Ib model group (600.00±73.48 mm,420.00±42.43 mm),T3 treatment significantly reduced the lesion size (180.00±42.43 mm, 165.00+25.98mm;p< 0.01).2.Q-PCR2.1 Expressions of Olig2The expression of Olig2 was not detected in all groups at postoperative Hour 24,72,168 and 336.2.2 Expressions of SOX10The expression of SOX 10 was detected in all experient groups at postoperative Hour 24, 72, 168 and 336. In Ib model group, the expression of SOX10 was detected at postoperative Hour 24 and 72 (1.70±0.58, 3.05±0.35),had statistical differences VS sham group. In T3 treatment group, expressions of SOX10 was 22.11±0.53 at postoperative Hour 72 which was lower than lb model group.It had statistical differences VS control gourp and sham group (p<0.05). Statistical differences were not found at postoperative Hour 168 and 336 in all groups.3. Immunofluorescence Histochemistry3.1 Expressions of Olig2Only small amounts of target proteins (Green fluorescence) were detected in all groups at hour 24 and 72,while not 168 and 336; the positive-cell number were 43.0±8.2.46.2?8.5 which had statistical differences. T3 treatment goup VS Ib model group (p<0.05) . What's more, the target proteins expressions of T3 treatment group in brain tissue were significantly higher than that of other groups at postoperative hour 24 and 72.3.2 Expressions of SOX 10SOX10 expressions (Green fluorescence) were detected at postoperative Hour 24 and 72 in all group, while not at hour 168 and 336. In the lb model group, SOX 10 expressions were higher than that of other groups at postoperative Hour 24and 72.The positive-cell number were 40.1 ± 9.2.39.3±8.3,which of T3 teatment group were lower than that of lb model group, but higher than that of control group and sham group. At postoperative Hour 24, it had statistical differences, lb model group VS T3 treat goup (p<0.05)4. Western Blot4.1 Expressions of Olig2Only small amounts of target proteins (Green fluorescence) were detected in all groups at postoperative hour 24 and 72, while not 168 and 336. What's more, the target proteins expressions of T3 treatment group in brain tissue were significantly higher than that of other groups at postoperative hour 24 and 72.4.2 Expressions of SOX10SOXIO expressions (Green fluorescence) were detected at postoperative Hour 24and 72 in all group, while not at hour 168 and 336. In the Ib model group, SOX10 expressions were higher than that of other groups at postoperative Hour 24 and 72,which of T3 treatment group were lower than that of Ib model group, but higher than that of control group and sham group.Conclusions: 1. L-T3 treatment could reduce the lesion size of PVL induced by ibotenate. 2. L-T3 's neuroprotective effects may be altered by changing the expression of Olig2 and SOX10. |
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