The trophic effect of ciliary neurotrophic factor on injured masseter muscle in rat

OBJECTIVE(S): Occlusal trauma is one of the most common forms of oral biting dysfunction. Long-term occlusal trauma could weaken the stomatognathic system; especially damage one’s masticatory muscle. Through using the rat model, this study investigated the trophic effect of ciliary neurotrophic factor (CNTF) on injured masseter muscle. MATERIALS AND METHODS: Male Wistar rats (n=36) were randomly divided into five experimental groups and one control group (6 rats per group). Animals in the experimental group were cemented modified crowns on their mandibular first molars to artificially induce occlusal trauma in 1, 3, 7, 14, and 28 days. Control group was sham-treated with forced mouth-opening for about 5 min, while no crowns were placed. After 28 days of treatment, all rats were euthanized and their masseter muscle was collected. Through immunofluorescence and real-time quantitative PCR, the expression of desmin, CNTF, and CNTFRα was investigated in rat masseter muscle. The microstructure of masseter muscle was observed by transmission electron microscope. RESULTS: The expression of desmin showed a time-dependent decrease on traumatic and non-traumatic sides masseter, until reached the nadir at the 14(th) day, then restored to its normal level at the 28(th) day; however, the expression of CNTF and CNTFRα on the traumatic and non-traumatic sides increased from day 7, reached the peak at the 14(th) day, and returned to normal level on the 28(th) day. CONCLUSION: CNTF, as an important neurotrophic factor, was tightly associated to the restoring of rat injured masseter muscle, which provides new target and treatment method for clinical application.