Study About The Protective Effects Of CNTF On Rat Masseter Injury Induced By Occlusal Trauma

Objectives:To investigate the expression of CNTF, CNTFRa, desmin and the changes in the microstructure of the masseter muscle caused by traumatic occlusion, before and after injection of endogenous ciliary neurotrophic factor. To explore the correlation between the two factors. To study the etiology mechanism of the masticatory muscle dysfunction and advance effective treatment ideas for the dysfunction of the masticatory muscles induced by occlusal trauma.Methods:36healthy male Wistar rats were divided into1day,3days,7days,14days,28days and the control group with a random number table(1day,3days,7days,14days,28days are the experimental groups). The right first molar of rats in the experimental group were bonded1mm thick cast crown, after1day,3days,7days,14days,28days to take the trauma side (the right side) and non-traumatic side (the left side) masseter; the control goup analoged the operation.24healthy male Wistar rats were divided into occlusal trauma+normal saline (Normal saline, NS) group, occlusal trauma+CNTF group, normal+NS group, normal+CNTF group with a random number table; occlusal trauma+NS group and occlusal trauma+CNTF group established animal model of traumatic occlusion using the same modeling methods, normal+NS group and normal+CNTF group simulated the same operation, rats of normal+CNTF group and occlusal trauma+CNTF group were daily injected of recombinant CNTF (3mg/kg) in double side massete, rats of normal+NS group and occlusal trauma+NS group were daily injected of the same dose of NS, bilateral masseter were taked14days after the injection. The expression CNTFRa and CNTF were measured by immunohistochemical; the expression of desmin were measured byimmunofluorescence; the relative expression of CNTFmRNA, CNTFRamRNA, desmin mRNA were detected by real-time PCR; the the microstructure of the masseter muscle were observed under the TEM. Results:1) The expression levels of CNTF, CNTFRa, CNTFmRNA, CNTFRamRNA in the trauma side of714days group, the non-traumatic side of14days group masseter were significantly higher than the control group (p<0.01), and the trauma side of714days group were significantly higher than the non-traumatic side (p<0.05); the expression levels of CNTF, CNTFRa, CNTFmRNA, CNTFRamRNA in the trauma and non-traumatic side of14days group were significantly higher than the corresponding side of the other groups (p<0.05). The expression levels of CNTF, CNTFRa, CNTFmRNA in the trauma side and non-traumatic side of occlusal trauma+NS group were significantly higher than normal+NS group, normal+CNTF group, occlusal trauma+CNTF group (p<0.01), and the trauma side were significantly higher than the non-traumatic side (p<0.05); the expression levels of CNTFRa and CNTFRamRNA in bothsides of trauma+CNTF group were significantly higher than occlusal trauma+NS group (p<0.01), while the occlusal trauma+NS group was significantly higher than normal+NS and normal+CNTF group (p<0.01).2) The expression levels of desmin in both sides of714days group, the traumatic side of3days group masseter were significantly lower than the control group (p<0.01), and the trauma side of3714days group were significantly lower than the non-traumatic side (p<0.05), while the expression levels of desmin in the trauma and non-traumatic side of14days group were significantly lower than the corresponding side of the other groups (p<0.01); the expression levels of desmin in both sides of714days group, the traumatic side of3days group masseter were significantly higher than the control group (p<0.01), the trauma side of3714days group were significantly higher than the non-traumatic side (p<0.05), the expression levels of desmin in the trauma and non-traumatic side of714days group were significantly higher than other groups (p<0.01) and non-traumatic side of14days group were significantly higher than the corresponding side of the other groups (p0.01); the expression levels of desmin desmin mRNA in the trauma side and non-traumatic side of occlusal trauma+NS group were significantly higher than normal+NS group, normal+CNTF group, occlusal trauma+CNTF group (p<0.01), and the trauma side were significantly higher than the non-traumatic side (p<0.05).3) The ultrastructural changes at different stages of the masseter muscle: masseter muscle fiber disorderation, muscle fiber shrinked or broken, striated muscle blurred or disappeared, muscle internal vascular proliferation, expansion and so on.Conclusion: The occlusal trauma can degrade desmin, destructing the cytoskeleton, leading to the masseter injury, ultrastructural changes in masseter muscle cells can be observed under the TEM. CNTF, as an important neurotrophic factor, played an effective role in the restoration of masticatory muscle damage, whose decreased expression may be involved in the destruction of masseter muscle cytoskeleton. Therefore, a new theoretical basis could be provided for the clinical treatment of masticatory muscle disorders caused by occlusal trauma.