Introduction: Melatonin signaling dysfunction has been suggested in girls with adolescent idiopathic scoliosis (AIS). The signaling dysfunction was observed in osteoblasts from AIS girls. The associated the occurrence of AIS with melatonin receptor-2 gene polymorphism has been shown previously.
Objective: To determine whether there is abnormality on the protein expression of melatonin receptors in AIS osteoblasts.
Methods: Intraoperative bone biopsies were obtained from 13 girls with severe AIS and 9 normal controls. The isolated osteoblasts were detected for the presence of melatonin receptor expressions (MT1 and MT2) by Western blotting. Also, the effect of melatonin on proliferation of osteoblasts was tested against different melatonin concentrations (0, 1nM, 100uM).
Results: Both MT1 and MT2 were found in the controls. MT1 was normally expressed in the AIS osteoblasts, however only 69% showed positive MT2 expression when compared with controls. Proliferation of AIS osteoblasts without MT2 was the least when compared with control and those with MT2 expression with melatonin added. Also, melatonin significantly enhanced the control osteoblasts to proliferate. The proliferation of AIS with MT2 was higher than those without.
Conclusion: This is the first to report the difference between the AIS and control osteoblasts in the expression of MT2. The results indicated there is possible functional effect toward osteoblasts proliferation.
Significance: Although the physiological significance on the expression remains uncertain, the absence of MT2 in AIS osteoblasts showed the lowest percentage of viable cells with melatonin treatment which indicating a modulator role toward osteoblasts proliferation.