[Study of peroxisome proliferator-activated receptor-γ coactivator-1α expression and cytoapoptosis in masseter muscles of unilateral chewing rat].

Objective: To investigate the changes of peroxisome proliferator- activated receptor-γ coactivator -1α (PGC-1α) 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.