Evidence of Intrinsic Impairment of Osteoblast Phenotype at the Curve Apex in Girls With Adolescent Idiopathic Scoliosis

Abstract Study Design An observational descriptive study based on a single cohort of patients. Objective To determine whether spinal facet osteoblastsat the curve apex display a different phenotype to osteoblastsfrom outside the curve in adolescent idiopathic scoliosis (AIS) patients. Summary of Background Data Intrinsic differences in the phenotype of spinal facetbone tissue and in spinal osteoblastshave been implicated in the pathology of AIS. However, no study has compared the phenotype of facet osteoblastsat the curve apex compared with outside the curve in AIS patients. Methods Facetspinal tissue was collected perioperatively from three sites, the concave and convex side at the curve apex and from outside the curve (noncurve) from three AIS female patients aged 13–16 years. Spinal tissue was analyzed by micro–computed tomography to determine bone mineral density (BMD) and trabecular structure. Primary osteoblastswere cultured from concave, convex, and noncurve facetbone chips. The phenotype of osteoblastswas determined by assessment of cellular proliferation, cellular metabolism (alkaline phosphatase and SeahorseAnalyzer), bone nodule mineralization ( Alizarinred assay), and the mRNA expression of Wnt signaling genes (quantitative reverse transcriptase polymerase chain reaction). Results Convex facettissue exhibited greater BMD and trabecular thickness, compared with concave facettissue. Osteoblastsat the convex side of the curve apex exhibited a significantly higher proliferative and metabolic phenotype and a greater capacity to form mineralized bone nodules, compared with concave osteoblasts. mRNA expression of SKP2was significantly greater in both concave and convex osteoblasts, compared with noncurve osteoblasts. The expression of SFRP1 was significantly downregulated in convex osteoblasts, compared with either concave or noncurve. Conclusions Intrinsic differences that affect osteoblastfunction are exhibited by spinal facet osteoblastsat the curve apex in AIS patients. Level of Evidence Level IV, Prognostic.