Research About The Mechanism Of Calcineurin In Masticatory Muscle Dysfunctional Induced By Lateral Chewing

Objectives:To study the mechanism in masticatory muscle dysfunctional induced by lateral chewing, and to find out the infection of calcinerin acting on dysfunctional syndromes of the masticatory muscles from muscle fibre type. Finally, explore the possibility of lateral chewing induced to temporomandibular disorders (TMD).Methods:36 female Wistar rats were randomly divided into control and experimental group, using the maxillary posterior teeth extraction method result in animal model of unilateral chew, and in 2 weeks,4weeks,6 weeks and 8 weeks after tooth extraction, tested Ca2+concentration, calcineurin activity and muscle fiber type and other indicators in the mouse masseter muscle tissue. Compare the indicators between experimental and control groups, the extraction side and non-extraction side of the rats masseter, analysis the revelance of Ca2+and calcineurin enzyme, calcineurin activity and proportion of muscle fiber type. The experimental use atomic spectrometry detection to survey the Ca2+concentration; colorimetric method to detect calcineurin activity; with ATPase staining the muscle fiber types.Results:1) Ca2+concent of extraction side of the masseter muscle was significantly higher in 2 weeks,4 weeks and 6 weeks experimental groups(P< 0.05).In the 4 weeks experimental group of non-wxtraction side of the masseter muscle, Ca2+content of tissues was significantly higher than that in 2 weeks,6 weeks, 8 weeks groups'(P<0.05); and in 4-week experimental group extraction side of the masseter muscle tissue Ca2+content was significantly higher than non-extraction side (P <0.01).2) The proportion of slow muscle fibers in experimental groups of non-extraction side of masseter muscle tissues was higher than normal controls(P<0.05); in the experimental extraction side of the masseter muscle tissue, the proportion of type I muscle fibers have increased, especially the 2 weeks,4 weeks,8 weeks groups (P <0.05); non-extraction side was higher than of the extraction side in 4 weeks,6 week experimental groups (P<0.05).3) Calcinuerin activity increased with Ca2+contents change as a bell-shape.4) The ratio of slow-type fiber was positively correlated to the activities of calcinuerin(r=0.876,p<0.05).Conclusions:Ca2+concentrations arose in masticatory muscle tissue was caused by long-term unilateral chewing (eg,the side of the posterior teeth missing of deficient).High concentrations of Ca2+activited CaN/NAFT signaling pathway which related to muscle fibers and skeletal muscle growth and transformation. And the activated signaling pathways promoted slow muscle phenotype of protein coding gene transcription, transformed the muscle fiber from fast to slow,which may be the mechanism that unilateral chewing caused the muscle dysfunction. Therefore, a new target of the clinical treatment of TMD research was provided.