To determine whether spinal facet osteoblasts at the curve apex display a different phenotype to osteoblasts from outside the curve in patients with adolescent idiopathic scoliosis (AIS). Intrinsic differences in the phenotype of spinal facet bone tissue and in spinal osteoblasts have been implicated in the pathogenesis of AIS. However, no study has compared the phenotype of facet osteoblasts at the curve apex with the facet osteoblasts from outside the curve in patients with AIS. Facet bone tissue was collected from three sites, the concave and convex side at the curve apex and from outside the curve from three female patients with AIS (aged 13–16 years). Micro-CT analysis was used to determine the density and trabecular structure. Osteoblasts were then cultured from the sampled bone. Osteoblast phenotype was investigated by assessing cellular proliferation (MTS assay), cellular metabolism (alkaline phosphatase and Seahorse Analyser), bone nodule mineralisation (Alizarin red assay), and the mRNA expression of Wnt signalling genes (quantitative RT-PCR). Convex bone showed greater bone mineral density and trabecular thickness than did concave bone. The convex side of the curve apex exhibited a significantly higher proliferative and metabolic phenotype and a greater capacity to form mineralised bone nodules than did concave osteoblasts. mRNA expression of SKP2 was significantly greater in both concave and convex osteoblasts than in non-curve osteoblasts. The expression of SFRP1 was significantly downregulated in convex osteoblasts compared with either concave or non-curve. Intrinsic differences that affect osteoblast function are exhibited by spinal facet osteoblasts at the curve apex in patients with AIS

Background. We have reported an injectable L-pNIPAM-co-DMAc hydrogel with hydroxyaptite nanoparticles (HAPna) which promotes mesenchymal stem cell (MSC) differentiation to bone cells without the need for growth factors. This hydrogel could potentially be used as an osteogenic and osteoconductive bone filler of spinal cages to improve vertebral body fusion. Here we investigated the biocompatibility and efficacy of the hydrogel in vivo using a proof of concept femur defect model. Methods. Rat sub-cut analysis was performed to investigate safety in vivo. A rat femur defect model was performed to evaluate efficacy. Four groups were investigated: sham operated controls; acellular L-pNIPAM-co-DMAc hydrogel; acellular L-pNIPAM-co-DMAc hydrogel with HAPna; L-pNIPAM-co-DMAc hydrogel with rat MSCs and HAPna. Following 4 weeks, defect site and organs were histologically examined to determine integration, repair and inflammatory response, as well as Micro-CT to assess mineralisation. Results. No inflammatory reactions or toxicity were seen in any animal. Enhanced bone healing was observed in aged exbreeder female rats where hydrogel was injected with increased deposition of collagen type I. Integration of the hydrogel with surrounding bone was observed without the need for delivered MSCs; native cell infiltration was also seen and bone formation was observed within all hydrogel systems investigated. Conclusion. This novel hydrogel is biocompatible, facilitates migration of cells, promotes increased bone formation and integrates with surrounding bone. This system could be injected to fill spaces within and surrounding spinal cages to aid in cage fixation and spinal fusion without the need for harvesting of bone autografts, thus reducing operative risk and surgical cost. Conflicts of Interest: None. Source of Funding: BMRC, MERI Sheffield Hallam University

Introduction. Adolescent idiopathic scoliosis (AIS) is the most common spinal deformity in children, and its cause is unknown. Recently, researchers have traced a defect in the gene CHD7 to AIS. CHD7 encodes for a chromodomain helicase of the DNA-binding domain protein family and is thought to have a crucial role in many basic cellular functions. However, the functional role of CHD7 in AIS is still elusive. In this study, we investigated the potential pathogenic effect of gene defects in CHD7 in vivo by evaluating their effect on spine formation and development in zebrafish. Methods. To investigate the function of the CHD7 encoded protein, we generated an antisense morpholino oligonucleotide against the CHD7 gene to disrupt the translation of the gene transcripts and knockdown the levels of its protein. The morpholino was injected into single-cell stage zebrafish embryos. The injected fish were allowed to develop and were then assessed for distinct phenotypes reminiscent of scoliosis by histological stains. Results. Knockdown of CHD7 resulted in a spectrum of ocular and heart anomalies. We noted that 26% of the zebrafish morphants exhibited curvature of the body axis at early stages. Histological stains of the vertebrae at later stages revealed that the spine of the zebrafish morphant had abnormal kinks rather than scoliotic curves. These defects were accompanied by reduced vertebral mineralisation around the kink area. The CHD7 morphant also showed severe cranial nerve abnormalities and had missing or malformed otolith—a part of the vestibular system analogous to the human ear. Conclusions. Our findings indicate a key role of CHD7 in eye, heart, and ear development but not in the onset of skeletal deformities as observed in scoliosis. Our results are similar to the congenital abnormities associated with CHD7 mutations in the CHARGE syndrome. Acknowledgments. This study is supported by the Yves Cotrel Fondation