Objective To investigate the changes of peroxisome proliferator-activated receptor-γ coactivator-1 α (PGC-1 α) mRNA and cytoapoptosis in the rats' masseter muscle which had been influenced by unilateral chewing,and to explore the theoretical foundation of changes in masticatory muscles induced by unilateral chewing.Methods The animal models were established by extracting the Wistar rats' left maxillary molars.Thirty-six female Wistar rats were randomly divided into four groups of 2,4,6 and 8 weeks,nine each.In each group there were six rats with molar extracted and three as control.The Ca2+ level was detected by atomic spectrophotometric method.The relative expression of PGC-1α mRNA was detected by real-time fluorescent quantitative PCR.The apoptosis index was detected by Hoechst staining.Results The Ca2+ level in the muscle on the extraction side were significantly higher than that in the controls in the beginning stage of unilateral chewing,and reached the peak at the 4th week [(43.62 ± 2.36) μg/g].The relative expressions of PGC-1α increased from the beginning and reached the maximum level at the 4th week [extraction side:(1.57±0.10); non-extraction side:(1.92±0.06)],while the relative expressions of PGC-1α in 6 and 8 weeks decreased gradually [extraction side:(1.06 ±0.08),(1.08 ±0.07); non-extraction side:(1.09±0.10),(1.11 ± 0.08)].The changes of apoptosis index on non-extraction side increased continually and peaked at the 6th week [(38.56± 1.64)％].Conclusions PGC-1α and cytoapoptosis played important roles in different stages of tissue remodeling induced by unilateral chewing.

Objective To investigate the expression of the Toll-like receptor-4 (TLR-4) in temporomandibular joint synovitis in rats,and to discuss the correlation between the expression of TLR-4 and the synovitis.Methods Sixty male wistar rats were randomly divided into five groups,12 each.Group A was the control group in which the rats were given normal diet.In Group B,the rats' bilateral masseter muscles were cut off (masseter resection group).In Group C,An cast metal crown were bonded on the mandibular right first molar of each rat (occlusal interference group).In Group D,occlusal pad were bonded on maxillary molars of each rat (occlusal dimension increase group).In Group E,rats' bilateral masseter muscles were resected and occlusal pads were bonded on their maxillary molars (masseter resection and occlusal dimension increase group).Pathological changes of synovium were observed using hematoxylin and eosin (HE) stains and pathology scores were evaluated.The expression of TLR-4 were determined by immunohistochemical stains,and the expression of TLR-4 mRNA were determined by real-time PCR.The correlation between the expression of TLR-4,TLR-4 mRNA and the pathological score were analyzed using Spearman analysis.Results The pathological scores of Group A-E were 0.5±0.5,2.5±1.0,2.7±1.0,3.0±0.9,5.3±1.2 respectively.The expression of TLR-4 were (3.2±1.5) ％,(16.0±2.6) ％,(15.8±2.1) ％,(17.5±2.4) ％,(38.2±4.4) ％.The expression of TLR-4 mRNA were 1.07±0.09,2.12±0.33,2.07±0.29,2.17±0.34,4.53±0.46.Compared with group A,groups B-E showed significant higher pathology score (P＜0.05) and increased expression of both TLR-4 (P＜0.05) and TLR-4 mRNA (P＜0.05).An significant positive correlation was found between the expression of TLR-4 and the pathology score (r=0.785,P＜0.05),and between the expression of TLR-4 mRNA and the pathology score (r=0.720,P＜0.05).Conclusions TLR-4 may be closely associated with the development of the synovitis of TMJ of rats.