BackgroundAdolescent idiopathic scoliosis (AIS) is a scoliotic deformity of unknown etiology that occurs during adolescent development. Abnormal bone metabolism is closely related to AIS, but the cause is uncertain. Recent studies have shown that heat shock protein 27 (HSP27) and its phosphorylation (pHSP27) play important roles in bone metabolism. However, whether HSP27 and pHSP27 are involved in abnormal bone metabolism in AIS is unclear.MethodsOsteoblasts (OBs) and bone marrow stem cells (BMSCs) were extracted from the facet joints and bone marrow of AIS patients and controls who underwent posterior spinal fusion surgery. The expression levels of HSP27 and pHSP27, as well as the expression levels of bone formation markers in OBs from AIS patients and controls, were examined by quantitative real‐time PCR (qRT–PCR) and Western blotting. The mineralization ability of OBs from AIS patients and controls was analyzed by alizarin red staining after osteogenic differentiation. Heat shock and thiolutin were used to increase the levels of pHSP27 in OBs, and the levels of bone formation markers were also investigated. In addition, the levels of pHSP27 and the bone formation ability of BMSCs from AIS patients and controls were investigated after heat shock treatment.ResultsLower pHSP27 levels and impaired osteogenic differentiation abilities were observed in the OBs of AIS patients than in those of controls. Thiolutin increased HSP27 phosphorylation and increased the mRNA levels of SPP1 and ALPL in OBs from AIS patients. Heat shock treatment increased SPP1 and HSP27 mRNA expression, pHSP27 levels, OCN expression, and mineralization ability of both OBs and BMSCs from AIS patients.ConclusionHeat shock treatment and thiolutin can increase the levels of pHSP27 and further promote the bone formation of OBs and BMSCs from AIS patients. Therefore, decreased pHSP27 levels may be associated with abnormal bone metabolism in AIS patients.
Background: Congenital scoliosis (CS) is a complex spinal malformation of unknown etiology with abnormal bone metabolism. Fibroblast growth factor 23 (FGF23), secreted by osteoblasts and osteocytes, can inhibit bone formation and mineralization. This research aims to investigate the relationship between CS and FGF23. Methods: We collected peripheral blood from two pairs of identical twins for methylation sequencing of the target region. FGF23 mRNA levels in the peripheral blood of CS patients and age-matched controls were measured. Receiver operator characteristic (ROC) curve analyses were conducted to evaluate the specificity and sensitivity of FGF23. The expression levels of FGF23 and its downstream factors fibroblast growth factor receptor 3 (FGFr3)/tissue non-specific alkaline phosphatase (TNAP)/osteopontin (OPN) in primary osteoblasts from CS patients (CS-Ob) and controls (CT-Ob) were detected. In addition, the osteogenic abilities of FGF23-knockdown or FGF23-overexpressing Ob were examined. Results: DNA methylation of the FGF23 gene in CS patients was decreased compared to that of their identical twins, accompanied by increased mRNA levels. CS patients had increased peripheral blood FGF23 mRNA levels and decreased computed tomography (CT) values compared with controls. The FGF23 mRNA levels were negatively correlated with the CT value of the spine, and ROCs of FGF23 mRNA levels showed high sensitivity and specificity for CS. Additionally, significantly increased levels of FGF23, FGFr3, OPN, impaired osteogenic mineralization and lower TNAP levels were observed in CS-Ob. Moreover, FGF23 overexpression in CT-Ob increased FGFr3 and OPN levels and decreased TNAP levels, while FGF23 knockdown induced downregulation of FGFr3 and OPN but upregulation of TNAP in CS-Ob. Mineralization of CS-Ob was rescued after FGF23 knockdown. Conclusions: Our results suggested increased peripheral blood FGF23 levels, decreased bone mineral density in CS patients, and a good predictive ability of CS by peripheral blood FGF23 levels. FGF23 may contribute to osteopenia in CS patients through FGFr3/TNAP/OPN pathway.
Paravertebral muscle (PVM) abnormalities play important roles in the pathogenesis of idiopathic scoliosis (IS), and elevated oxidative stress could result in PVM injury in IS patients, but the underlying mechanism of oxidative stress generation is still unclear. Increased apoptosis, impaired myogenesis and elevated oxidative stress were found in primary skeletal muscle mesenchymal progenitor cells (hSM-MPCs), which are essential for the myogenesis process of vertebrate skeletal muscles, of IS patients. Through RNA-sequencing (RNA-seq) and further analysis, we identified significantly upregulated myostatin (MSTN) in IS hSM-MPCs. Overexpression of MSTN in hSM-MPCs from control patients increased the expression of NADPH oxidase 4, promoted reactive oxygen species production and apoptosis, and suppressed myogenesis. However, MSTN knockdown decreased the expression of NADPH oxidase 4, inhibited reactive oxygen species production and apoptosis, and enhanced myogenesis in hSM-MPCs from IS patients. In addition, overexpression of MSTN in the PVMs of mice induced elevated oxidative stress and scoliosis without abnormal vertebral structure. Altogether, our study suggested that abnormal PVM changes and accumulated oxidative stress in IS patients may result from upregulation of MSTN.
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