Unique local bone tissue characteristics in iliac crest bone biopsy from adolescent idiopathic scoliosis with severe spinal deformity

Biomechanical analysis of spinal cord injury during scoliosis correction surgery

Introduction: Surgical correction is a common treatment for severe scoliosis. Due to the significant spinal deformation that occurs with this condition, spinal cord injuries during corrective surgery can occur, sometimes leading to paralysis. Methods: Such events are associated with biomechanical changes in the spinal cord during surgery, however, their underlying mechanisms are not well understood. Six patient-specific cases of scoliosis either with or without spinal complications were examined. Finite element analyses (FEA) were performed to assess the dynamic changes and stress distribution of spinal cords after surgical correction. The FEA method is a numerical technique that simplifies problem solving by replacing complex problem solving with simplified numerical computations. Results: In four patients with poor prognosis, there was a concentration of stress in the spinal cord. The predicted spinal cord injury areas in this study were consistent with the clinical manifestations of the patients. In two patients with good prognosis, the stress distribution in the spinal cord models was uniform, and they showed no abnormal clinical manifestations postoperatively. Discussion: This study identified a potential biomechanical mechanism of spinal cord injury caused by surgical correction of scoliosis. Numerical prediction of postoperative spinal cord stress distribution might improve surgical planning and avoid complications.

Potential Interaction between WNT16 and Vitamin D on Bone Qualities in Adolescent Idiopathic Scoliosis Patients and Healthy Controls

Adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal deformity that is associated with low bone mineral density (BMD). Vitamin D (Vit-D) supplementation has been suggested to improve BMD in AIS, and its outcomes may be related to genetic factors. The present study aimed to (a) investigate the synergistic effect between a low BMD-related gene (wingless-related integration site 16, WNT16) and two important Vit-D pathway genes (Vit-D receptor, VDR, and Vit-D binding protein, VDBP) on serum Vit-D and bone qualities in Chinese AIS patients and healthy adolescents, and (b) to further investigate the effect of ablating Wnt16 on the cortical bone quality and whether diets with different dosages of Vit-D would further influence bone quality during the rapid growth phase in mice in the absence of Wnt16. A total of 519 girls (318 AIS vs. 201 controls) were recruited, and three selected single-nucleotide polymorphisms (SNPs) (WNT16 rs3801387, VDBP rs2282679, and VDR rs2228570) were genotyped. The serum 25(OH)Vit-D level was significantly associated with VDBP rs2282679 alleles (OR = -4.844; 95% CI, -7.521 to -2.167, p < 0.001). Significant multi-locus models were identified by generalized multifactor dimensionality reduction (GMDR) analyses on the serum 25(OH)Vit-D level (p = 0.006) and trabecular area (p = 0.044). In the gene-edited animal study, Wnt16 global knockout (KO) and wildtype (WT) male mice were provided with different Vit-D diets (control chow (1000 IU/Kg) vs. Vit-D-deficient chow (Nil in Vit-D) vs. high-dose Vit-D chow (20,000 IU/Kg)) from 4 weeks to 10 weeks old. Wnt16 global KO mice had significantly lower serum 25(OH)Vit-D levels and higher liver Vdbp mRNA expression levels than WT mice. In addition, Wnt16 global KO mice showed a decrease in bone density, cortical thickness and cortical area compared with WT mice. Interestingly, high-dose Vit-D chow led to lower bone density, cortical thickness, and cortical area in WT mice, which were less obvious in Wnt16 global KO mice. In conclusion, WNT16 may regulate the serum 25(OH)Vit-D level and bone qualities, which might be associated with VDBP expression. Further investigations with a larger sample size and wider spectrum of scoliosis severity are required to validate our findings regarding the interaction between WNT16 and Vit-D status in patients with AIS.

Risk factors associated with low bone mineral density in children with idiopathic scoliosis: a scoping review

BACKGROUND

Children with idiopathic scoliosis (IS) have a high risk of osteoporosis and IS with low bone mineral density (BMD) are susceptible to curve progression. This review aims to explore the risk factors of low BMD in children with IS.

METHODS

Studies were retrieved from 5 databases that were published up to January 2022. Search terms are keywords in titles or abstracts, including subject headings related to "Scoliosis", "Bone Mineral Density", and "Risk Factors". Observational studies on risk factors of low BMD in children with IS were enrolled in this review. The number of studies, sample size, outcome measures, research type, endocrine, and lifestyle-related factors, gene/signal pathway, and other contents were extracted for qualitative analysis.

RESULTS

A total of 56 studies were included in this scoping review. Thirty studies involved genetic factors that may affect BMD, including the Vitamin-D receptor gene, RANK/RANKL signal pathway, the function of mesenchymal stem cells, Runx2, Interleukin-6 (IL-6), and miR-145/β-catenin pathway. Eight studies mentioned the influence of endocrine factors on BMD, and the results showed that serum levels of IL-6, leptin and its metabolites, and ghrelin in children with IS were different from the age-matched controls. In addition, there were 18 articles on lifestyle-related factors related to low BMD in children with IS, consisting of physical activity, calcium intake, Vitamin D level, and body composition.

CONCLUSIONS

Genetic, endocrine, and lifestyle-related factors might relate to low BMD and even osteoporosis in IS. To prevent osteoporosis, the effectiveness of regular screening for low BMD risk factors in children with IS needs to be investigated. Additionally, clear risk factors suggest strategies for bone intervention. Future studies should consider the effectiveness of calcium and vitamin D supplements and physical activity in BMD improvement.

Bone mineral density in children and young adults with idiopathic scoliosis: a systematic review and meta-analysis

PURPOSE

Osteoporosis is a risk factor for idiopathic scoliosis (IS) progression, but it is still unclear whether IS patients have bone mineral density (BMD) loss and a higher risk of osteoporosis than asymptomatic people. This systematic review aims to explore the differences in BMD and prevalence of osteoporosis between the IS group and the control group.

METHODS

We searched 5 health science-related databases. Studies that were published up to February 2022 and written in English and Chinese languages were included. The primary outcome measures consisted of BMD z score, the prevalence of osteoporosis and osteopenia, and areal and volumetric BMD. Bone morphometry, trabecular microarchitecture, and quantitative ultrasound measures were included in the secondary outcome measures. The odds ratio (OR) and the weighted mean difference (WMD) with a 95% confidence interval (CI) were used to pool the data.

RESULTS

A total of 32 case-control studies were included. The pooled analysis revealed significant differences between the IS group and the control group in BMD z score (WMD -1.191; 95% CI  - 1.651 to -0.732, p  <  0.001). Subgroup analysis showed significance in both female (WMD -1.031; 95% CI -1.496 to -0.566, p  <  0.001) and male participants (WMD -1.516; 95% CI -2.401 to -0.632, p  =  0.001). The prevalence of osteoporosis and osteopenia in the group with IS was significantly higher than in the control group (OR  =  6.813, 95% CI 2.815-16.489, p  <  0.001; OR 1.879; 95% CI 1.548-2.281, p  <  0.000). BMD measures by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography showed a significant decrease in the IS group (all p  <  0.05), but no significant difference was found in the speed of sound measured by quantitative ultrasound between the two groups (p > 0.05).

CONCLUSION

Both the male and female IS patients had a generalized lower BMD and an increased prevalence of osteopenia and osteoporosis than the control group. Future research should focus on the validity of quantitative ultrasound in BMD screening. To control the risk of progression in IS patients, regular BMD scans and targeted intervention are necessary for IS patients during clinical practice.

Upregulation of microRNA-96-5p is associated with adolescent idiopathic scoliosis and low bone mass phenotype

Bone densitometry revealed low bone mass in patients with adolescent idiopathic scoliosis (AIS) and its prognostic potential to predict curve progression. Recent studies showed differential circulating miRNAs in AIS but their diagnostic potential and links to low bone mass have not been well-documented. The present study aimed to compare miRNA profiles in bone tissues collected from AIS and non-scoliotic subjects, and to explore if the selected miRNA candidates could be useful diagnostic biomarkers for AIS. Microarray analysis identified miR-96-5p being the most upregulated among the candidates. miR-96-5p level was measured in plasma samples from 100 AIS and 52 healthy girls. Our results showed significantly higher plasma levels of miR-96-5p in AIS girls with an area under the curve (AUC) of 0.671 for diagnostic accuracy. A model that was composed of plasma miR-96-5p and patient-specific parameters (age, body weight and years since menarche) gave rise to an improved AUC of 0.752. Ingenuity Pathway Analysis (IPA) indicated functional links between bone metabolic pathways and miR-96-5p. In conclusion, differentially expressed miRNAs in AIS bone and plasma samples represented a new source of disease biomarkers and players in AIS etiopathogenesis, which required further validation study involving AIS patients of both genders with long-term follow-up.

Sclerostin and Its Involvement in the Pathogenesis of Idiopathic Scoliosis

Idiopathic scoliosis is a disorder of unknown etiology. Bone biopsies from idiopathic scoliosis patients revealed changes at cellular and molecular level. Osteocytic sclerostin is downregulated, and serum level of sclerostin is decreased. Osteocytes in idiopathic scoliosis appear to be less active with abnormal canaliculi network. Differentiation of osteoblasts to osteocytes is decelerated, while Wnt/β-catenin signaling pathway is overactivated and affects normal bone mineralization that leads to inferior mechanical properties of the bone, which becomes susceptible to asymmetrical forces and causes deformity of the spinal column. Targeting bone metabolism during growth by stimulating sclerostin secretion from osteocytes and restoring normal function of Wnt/β-catenin signaling pathway could, in theory, increase bone strength and prevent deterioration of the scoliotic deformity.

Loss of longitudinal superiority marks the microarchitecture deterioration of osteoporotic cancellous bones

Osteoporosis (OP), a skeletal disease making bone mechanically deteriorate and easily fracture, is a global public health issue due to its high prevalence. It has been well recognized that besides bone loss, microarchitecture degradation plays a crucial role in the mechanical deterioration of OP bones, but the specific role of microarchitecture in OP has not been well clarified and quantified from mechanics perspective. Here, we successfully decoupled and identified the specific roles of microarchitecture, bone mass and tissue property in the failure properties of cancellous bones, through μCT-based digital modeling and finite element method simulations on bone samples from healthy and ovariectomy-induced osteoporotic mice. The results show that the microarchitecture of healthy bones exhibits longitudinal superiority in mechanical properties such as the effective stiffness, strength and toughness, which fits them well to bearing loads along their longitudinal direction. OP does not only reduce bone mass but also impair the microarchitecture topology. The former is mainly responsible for the mechanical degradation of bones in magnitude, wherever the latter accounts for the breakdown of their function-favorable anisotropy, the longitudinal superiority. Hence, we identified the microarchitecture-deterioration-induced directional mismatch between material and loading as a hazardous feature of OP and defined a longitudinal superiority index as measurement of the health status of bone microarchitecture. These findings provide useful insights and guidelines for OP diagnosis and treat assessment.

The construction of the scoliosis 3D finite element model and the biomechanical analysis of PVCR orthopaedy

Objective

The objective is to investigate the biomechanical conditions of the Posterior Vertebral Column Resection (PVCR) of the constructed scoliosis 3D finite element model.

Methods

A patient with scoliosis was selected; before the PVCR orthopaedy, the patient was submitted to the radiography of normal and lateral full-length vertebral column scans and the total magnetic resonance imaging (MRI) scans; then, the idiopathic scoliosis model was constructed by the 3D finite element method, and the 3D finite element software utilized in the process of model construction included Mimics software, Geomagic Studio 12 software, and Unigraphic 8.0 (UG 8.0) software; in addition, PVCR orthopaedy was utilized to correct the scoliosis of the patient, and the biomechanical parameters, such as orthodontic force, vertebral body displacement, orthopedic rod stress, stress on the pin-bone interface of the vertebral body surface, and the stress on the intervertebral disc, were studied.

Results

The 3D effective finite element model of scoliosis was successfully constructed by the Mimics software, the Geomagic Studio 12 software, and the UG 8.0 software, and the effectiveness was tested. PVCR orthopaedy could effectively solve the problem of scoliosis. The magnitude of the orthodontic force that a patient needed depended on the physical conditions and the personal orthodontic requirements of the patient. The maximum vertebral body displacement on the X-axis was the vertebral body L1, the maximum displacement on the Y-axis was the vertebral body T3, the maximum displacement on the Z-axis was the vertebral body T1, and the rang of orthopedic rod stress was 0.0050214e⁷ MPa to 0.045217e⁷ MPa, in which the maximum stress of 2 vertebral bodies in, above, and below the osteotomy area reached 0.045217e⁷ MPa, the stress on the pin-bone interface of the T10 vertebral body surface reached 11.83 MPa, and the stress of T8/T9 intervertebral disc reached 13.84 MPa.

Conclusion

The 3D finite element model based on 3D finite element software was highly efficient, and its numerical simulation was accurate, which was important for the subsequent biomechanical analysis of PVCR orthopaedy. In addition, the vertebral stress of PVCR orthopaedy was different in each body part, which was mainly affected by the applied orthodontic force and the sites of the orthodontic area.

A validated composite model to predict risk of curve progression in adolescent idiopathic scoliosis

BACKGROUND

In adolescent idiopathic scoliosis (AIS), the continuous search for effective prognostication of significant curve progression at the initial clinical consultation to inform decision for timely treatment and to avoid unnecessary overtreatment remains a big challenge as evidence of the multifactorial etiopathogenic nature is increasingly reported. This study aimed to formulate a composite model composed of clinical parameters and circulating markers in the prediction of curve progression.

METHOD

This is a two-phase study consisting of an exploration cohort (120 AIS, mean Cobb angle of 25°± 8.5 at their first clinical visit) and a validation cohort (51 AIS, mean Cobb angle of 23° ± 5.0° at the first visit). Patients with AIS were followed-up for a minimum of six years to formulate a composite model for prediction. At the first visit, clinical parameters were collected from routine clinical practice, and circulating markers were assayed from blood.

FINDING

We constructed the composite predictive model for curve progression to severe Cobb angle > 40° with a high HR of 27.9 (95% CI of 6.55 to 119.16). The area under curve of the composite model is higher than that of individual parameters used in current clinical practice. The model was validated by an independent cohort and achieved a sensitivity of 72.7% and a specificity of 90%.

INTERPRETATION

This is the first study proposing and validating a prognostic composite model consisting of clinical and circulating parameters which could quantitatively evaluate the probability of curve progression to a severe curvature in AIS at the initial consultation. Further validation in clinic will facilitate application of composite model in assisting objective clinical decision.

Abnormal lacuno-canalicular network and negative correlation between serum osteocalcin and Cobb angle indicate abnormal osteocyte function in adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a prevalent spinal deformity occurring during peripubertal growth period that affects 1-4% of adolescents globally without clear etiopathogenetic mechanism. Low bone mineral density is an independent and significant prognostic factor for curve progression. Currently, the cause underlying low bone mass in AIS remains elusive. Osteocytes play an important role in bone metabolism and mineral homeostasis, but its role in AIS has not been studied. In the present study, iliac bone tissues were harvested from 21 patients with AIS (mean age of 14.3 ± 2.20 yr old) with a mean Cobb angle of 55.6 ± 10.61° and 13 non-AIS controls (mean age of 16.5 ± 4.79 yr old) intraoperatively. Acid-etched scanning electron microscopy (SEM) images of AIS demonstrated abnormal osteocytes that were more rounded and cobblestone-like in shape and were aligned in irregular clusters with shorter and disorganized canaliculi. Further quantitative analysis with FITC-Imaris technique showed a significant reduction in the canalicular number and length as well as an increase in lacunar volume and area in AIS. SEM with energy-dispersive X-ray spectroscopy analysis demonstrated a lower calcium-to-phosphorus ratio at the perilacunar/canalicular region. Moreover, microindentaion results revealed lower values of Vickers hardness and elastic modulus in AIS when compared with controls. In addition, in the parallel study of 99 AIS (27 with severe Cobb angle of 65.8 ± 14.1° and 72 with mild Cobb angle of 26.6 ± 9.1°) with different curve severity, the serum osteocalcin level was found to be significantly and negatively associated with the Cobb angle. In summary, the findings in this series of studies demonstrated the potential link of abnormal osteocyte lacuno-canalicular network structure and function to the observed abnormal bone mineralization in AIS, which may shed light on etiopathogenesis of AIS.-Chen, H., Zhang, J., Wang, Y., Cheuk, K.-Y., Hung, A. L. H., Lam, T.-P., Qiu, Y., Feng, J. Q., Lee, W. Y. W., Cheng, J. C. Y. Abnormal lacuno-canalicular network and negative correlation between serum osteocalcin and Cobb angle indicate abnormal osteocyte function in adolescent idiopathic scoliosis.

SPRY4 is responsible for pathogenesis of adolescent idiopathic scoliosis by contributing to osteogenic differentiation and melatonin response of bone marrow-derived mesenchymal stem cells

Adolescent idiopathic scoliosis (AIS) is a complex, three-dimensional deformity of the spine that commonly occurs in pubescent girls. Decreased osteogenic differentiation and aberrant melatonin signalling have been demonstrated in mesenchymal stem cells (MSCs) from AIS patients and are implicated in the pathogenesis of AIS. However, the molecular mechanisms underlying these abnormal cellular features remain largely unknown. Our previous work comparing gene expression profiles between MSCs from AIS patients and healthy controls identified 1027 differentially expressed genes. In the present study, we focused on one of the most downregulated genes, SPRY4, in the MAPK signalling pathway and examined its role in osteogenic differentiation. We found that SPRY4 is markedly downregulated in AIS MSCs. Knockdown of SPRY4 impaired differentiation of healthy MSCs to osteoblasts, while SPRY4 overexpression in AIS MSCs enhanced osteogenic differentiation. Furthermore, melatonin treatment boosted osteogenic differentiation, whereas SPRY4 ablation ablated the promotional effects of melatonin. Moreover, SPRY4 was upregulated by melatonin exposure and contributed to osteogenic differentiation and melatonin response in a MEK-ERK1/2 dependent manner. Thus, loss of SPRY4 in bone marrow derived-MSCs results in reduced osteogenic differentiation, and these defects are further aggravated under the influence of melatonin. Our findings provide new insights for understanding the role of melatonin in AIS aetiology and highlight the importance of MSCs in AIS pathogenesis.

Aberrant miR-145-5p/β-catenin signal impairs osteocyte function in adolescent idiopathic scoliosis

Recently, noncoding RNAs have been thought to play important roles in the sporadic occurrence of spinal deformity of adolescent idiopathic scoliosis (AIS). As a prognostic factor for curve progression, low bone mass has been hypothesized to crosstalk with AIS pathogenesis. Abnormal osteoblasts activities are reported in AIS without a clear mechanism. In this study, bone biopsies from patients with AIS and control subjects and the primary osteoblasts derived from those samples were used to identify the potential microRNA (miRNA) candidates that interfere with osteoblasts and osteocytes function. Microarray analysis identified miRNA-145-5p (miR-145) as a potential upstream regulator. miR-145 and β-catenin mRNA ( CTNNB1) were overexpressed in AIS bone tissues and primary osteoblasts, and their expression correlated positively in AIS. Knockdown of miR-145 restored impaired osteocyte activity through the down-regulation of active β-catenin expression and its transcriptional activity. Significant negative correlations between circulating miR-145 and serum sclerostin, osteopontin, and osteoprotegerin were noted in patients with AIS, which was in line with our cellular findings. This is the first study to demonstrate the effect of aberrant miRNA expression and its effect on osteocyte function in AIS, which may contribute to the low bone mass. Our findings also provide insight into the development of circulating microRNAs as a bone quality biomarker or even a prognostic biomarker for AIS.-Zhang, J., Chen, H., Leung, R. K. K., Choy, K. W., Lam, T. P., Ng, B. K. W., Qiu,Y., Feng, J. Q., Cheng, J. C. Y., Lee, W. Y. W. Aberrant miR-145-5p/β-catenin signal impairs osteocyte function in adolescent idiopathic scoliosis.