Increased expression of receptor activator of nuclear factor-κB ligand in osteoblasts from adolescent idiopathic scoliosis patients with low bone mineral density

Abstract

Persistent generalized low bone mineral density (BMD) has been reported in patients with adolescent idiopathic scoliosis (AIS). However, the exact mechanisms and causes of the low BMD in AIS patients are largely unknown. The purpose of this study was to examine the relationship between the receptor activator of NF-κB ligand (RANKL)/osteoprotegerin (OPG) levels in osteoblasts (OBs) from AIS patients with low BMD and with comparison made between the patients and controls. Twenty AIS patients and eight age-matched controls were included in the present study. The BMD of lumbar spine and proximal femur was measured in all subjects. OBs from the cancellous bone of each subject was harvested and primarily cultured. The mRNA and protein expression of RANKL and OPG in OBs was detected by RT-PCR and Western blotting. The results showed BMD was lower in AIS patients than in controls. A significantly higher mRNA and protein expression of RANKL was observed in OBs from AIS patients, while no significant difference was found in the expression of OPG between AIS patients and controls. As a result, RANKL/OPG ratio in patients with AIS was remarkably higher than controls. Our study preliminarily demonstrated expression of RANKL was higher in OBs from AIS patients with low BMD as compared with controls, suggesting the unbalanced RANKL/OPG ratio caused by an over-expression of RANKL in OBs may be responsible for the low BMD in AIS patients.