Introduction: Melatonin deficiency and abnormal growth have been suggested to be involved in the development of adolescent idiopathic scoliosis (AIS). Multiple functions of melatonin have been described in skeleton system. It was hypothesized that melatonin might modulate endochondral ossification and regulate systemic skeletal growth.
Objectives: To investigate the role of melatonin on endochondral ossification in human in vitro organ culture.
Materials and Methods: Metacarpal (MC) and metatarsal (MR) bones (eleven pairs) harvested from aborted human fetus were cultured with melatonin (10 μM) for five-day with the contralateral side served as control. Longitudinal bone length was measured during culture. At the end the bones were fixed and embedded in paraffin for histomorphometry with the middle longitudinal section stained with Safranin O. The length of resting, proliferative and hypertrophic zones was measured. The expressions of membrane melatonin receptors (MT1, MT2) in the growth plate chondrocytes were determined by immunofluorescent staining.
Results: Both MT1 and MT2 receptors were detected in the resting and hypertrophic chondrocytes but not in the proliferative chondrocytes. Melatonin treated bones showed significantly shorter length (p<0.01), the lengths of the proliferative zone and hypertrophic zone were controls.
Conclusion: This is the first report showing the inhibitory effect of melatonin on longitudinal bone growth in human in vitro. The expression pattern of melatonin receptors indicated that they might be involved in the effect of melatonin.
Significance: The present study indicates that melatonin might play an important modulating role in endochondral ossification and longitudinal bone growth in human.