Abstract
Introduction
Although the association between osteoporosis and adolescent idiopathic scoliosis (AIS) has become widely accepted, the mechanism behind the development of osteoporosis and AIS remains unknown. To elucidate this relationship, we investigated the radiological and histological changes in a model of scoliosis in chickens, focusing on the cervical vertebrae that are not affected by scoliosis.
Methods
40 newly hatched broiler chickens were divided randomly into four equal groups: sham-operated chickens serving as control (CNT); pinealectomised chickens (PNX); and sham-operated (CNT+MLT) and pinealectomized chickens (PNX+MLT) that received intraperitoneal administration of MLT (8 mg/kg) at 2200 h daily. Pinealectomies were done at the age of 3 days. Before killing the chickens at 2 months of age, blood samples were collected at midnight and MLT concentrations were measured by radioimmunoassay. Post-mortem radiographs were examined for the presence of scoliosis, and microcomputed tomography (micro-CT) images were taken to assess the microstructure of the cervical vertebrae. Histological specimens of the scanned cervical vertebra were prepared, and a mid-sagittal section was stained with haematoxylin and eosin (HE) and tartrate-resistant acid phosphatase (TRAP) to assess the numbers of osteoblasts and osteoclasts, respectively.
Results
Scoliosis developed at the thoracic spine in all chickens in the PNX group and in two of the PNX+MLT group. MLT concentrations in the PNX group were substantially reduced, whereas normal concentrations were restored in the PNX+MLT group and were normal in the CNT and CNT+MLT groups. Micro-CT data showed that chickens in the PNX group had a greater degree of generalised osteoporosis than did those in the other groups. The number of osteoblasts was significantly decreased in the PNX group, whereas we recorded no significant difference between the CNT, CNT+MLT, and PNX+MLT groups. The number of osteoclasts was similar in all groups.
Conclusions
Our results suggest that MLT deficiency reduces osteoblast proliferation and leads to the development of scoliosis and osteoporosis. The restoration of MLT prevented the development of scoliosis and osteoporosis, indicating that MLT concentrations might be crucial to the development of scoliotic deformity and osteoporosis in AIS.
