Asymmetric expression of melatonin receptor mRNA in bilateral paravertebral muscles in adolescent idiopathic scoliosis

Study Design. Comparison of melatonin receptor mRNA expression in bilateral paravertebral muscles in adolescent idiopathic scoliosis (AIS). Objectives. To investigate the change of melatonin receptor mRNA expression in bilateral paravertebral muscles in AIS, congenital scoliosis ( CS), and control in order to analyze its association to the pathogenesis of AIS. Summary of Background Data. Muscle imbalance and asymmetry of stretch receptors in the paravertebral muscles of patients with AIS were supposed to have a large role to play in the development and production of the deformity. Melatonin is a focus of studies of the mechanism underlying the development of scoliosis, and there is no research on the expression of melatonin receptors in the paravertebral muscles of patients with AIS. Methods. Twenty cases with average age of 15.1 +/- 2.2 years and average Cobb angle of 56.2 degrees +/- 16.1 degrees, including 10 cases with Cobb angle > 50 degrees and 10 cases with Cobb angle <= 50 degrees, were included in AIS group. The apical vertebrae were from T6 to T11. Twelve cases with an average age of 11.6 +/- 3.2 years and average Cobb angle of 59.2 degrees +/- 33.3 degrees were included in CS group. The apical vertebrae were from T7 to T12. Ten cases without scoliosis were in the control group. The mRNA expression of melatonin receptor subtype MT1 and MT2 was detected by the RTPCR method. Results. The MT2 mRNA expression on the concave side of the paravertebral muscle was higher than that on the convex side in AIS and CS groups (P < 0.05), but the MT1 mRNA expression showed no significant difference (P > 0.05). In the AIS group, the ratio of MT2 mRNA expression on the concave side compared with the convex side in cases with Cobb angle > 50 degrees and cases with Cobb angle <= 50 degrees showed no significant difference (P > 0.05). The MT1 and MT2 mRNA expression showed no significant difference in control group (P > 0.05). Conclusion. The melatonin receptor expression in bilateral paravertebral muscles in AIS is asymmetric, which may be a secondary change. The bilateral asymmetry in force exerted on the scoliotic spine may be the cause.