Introduction: Melatonin signaling pathway has been suggested to be one of the key etiopathogenic factors of adolescent idiopathic scoliosis (AIS). Our previous pilot study showed that melatonin receptor 1B (MTNR1B) was not detected in the osteoblast of some AIS girls which may be related to abnormal melatonin signaling. However, it is necessary to clarify whether it is a quantitative or qualitative change. The present study aimed to investigate the possible problem of MTNR1B expression in AIS.
Methods: Intra-operative bone biopsies were obtained from 41 AIS girls and 9 normal controls. Osteoblasts were cultured from the biopsies and harvested for protein and mRNA extraction. Semi-quantification for both MTNR1A and 1B protein expressions was done by Western blotting. mRNA expression of the 2 receptors were quantified using Taqman Real Time PCR. Student's t-test was employed to compare the expression level of the receptors between AIS girls and controls.
Results: Both MTNR1A and MTNR1B were found in all examined individuals. While the protein and mRNA expression of MTNR1A was similar between AIS and controls, the expression of MTNR1B was significantly lower in AIS for protein (p<0.01) and mRNA (p=0.019).
Conclusion: In this study with larger sample size, the relatively lower MTNR1B expression in AIS girls suggested that its abnormal expression was a quantitative change rather than qualitative as shown in the previous study. The lower MTNR1B expression in AIS patients may lead to the irresponsiveness of melatonin and eventually contribute to the development of the disease. Previous studies also suggested the stoichiometry of MTNR1A and 1B could affect their function. Further studies on melatonin receptor and its related signaling pathways would provide a better understanding on the etiopathogenesis of AIS.
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