Etiopathogenesis of adolescent idiopathic scoliosis: Expression of melatonin receptors 1A/1B, calmodulin and estrogen receptor 2 in deep paravertebral muscles revisited

Genetics and pathogenesis of scoliosis

Background

Scoliosis is defined as a lateral spine curvature of at least 10° with vertebral rotation, as seen on a posterior-anterior radiograph, often accompanied by reduced thoracic kyphosis. Scoliosis affects all age groups: idiopathic scoliosis is the most common spinal disorder in children and adolescents, while adult degenerative scoliosis typically affects individuals over fifty. In the United States, approximately 3 million new cases of scoliosis are diagnosed annually, with a predicted increase in part due to global aging. Despite its prevalence, the etiopathogenesis of scoliosis remains unclear.

Methods

This comprehensive review analyzes the literature on the etiopathogenetic evidence for both idiopathic and adult degenerative scoliosis. PubMed and Google Scholar databases were searched for studies on the genetic factors and etiopathogenetic mechanisms of scoliosis development and progression, with the search limited to articles in English.

Results

For idiopathic scoliosis, genetic factors are categorized into three groups: genes associated with susceptibility, disease progression, and both. We identify gene groups related to different biological processes and explore multifaceted pathogenesis of idiopathic scoliosis, including evolutionary adaptations to bipedalism and developmental and homeostatic spinal aberrations. For adult degenerative scoliosis, we segregate genetic and pathogenic evidence into categories of angiogenesis and inflammation, extracellular matrix degradation, neural associations, and hormonal influences. Finally, we compare findings in idiopathic scoliosis and adult degenerative scoliosis, discuss current limitations in scoliosis research, propose a new model for scoliosis etiopathogenesis, and highlight promising areas for future studies.

Conclusions

Scoliosis is a complex, multifaceted disease with largely enigmatic origins and mechanisms of progression, keeping it under continuous scientific scrutiny.

Genetic animal modeling for idiopathic scoliosis research: history and considerations

PURPOSE

Idiopathic scoliosis (IS) is defined as a structural lateral spinal curvature ≥ 10° in otherwise healthy children and is the most common pediatric spinal deformity. IS is known to have a strong genetic component; however, the underlying etiology is still largely unknown. Animal models have been used historically to both understand and develop treatments for human disease, including within the context of IS. This intended audience for this review is clinicians in the fields of musculoskeletal surgery and research.

METHODS

In this review article, we synthesize current literature of genetic animal models of IS and introduce considerations for researchers.

RESULTS

Due to complex genetic and unique biomechanical factors (i.e., bipedalism) hypothesized to contribute to IS in humans, scoliosis is a difficult condition to replicate in model organisms.

CONCLUSION

We advocate careful selection of animal models based on the scientific question and introduce gaps and limitations in the current literature. We advocate future research efforts to include animal models with multiple characterized genetic or environmental perturbations to reflect current understanding of the human condition.

Estrogen Receptor Type 1 and Type 2 Presence in Paravertebral Skeletal Muscles: Expression Level and Relation to Phenotype in Children with Idiopathic Scoliosis

The study aimed to detect the presence and assess the expression levels of the estrogen receptors type 1 (ESR1) and type 2 (ESR2) within paravertebral skeletal muscles of female patients with idiopathic scoliosis (IS) in relation to phenotype parameters. Intraoperatively, the muscle samples were obtained from 35 adolescent females. The RT-qPCR, western blot and immunohistochemistry techniques were applied. The ESR1 and ESR2 were detected within paravertebral skeletal muscle cells, either the superficial or the deep ones. The ESR1 expression level was significantly higher in the deep muscles compared to the superficial ones. A left-right asymmetry of the ESR1 and ESR2 expression level was demonstrated in the deep muscles. There was a significant relationship between the expression asymmetry and either the Cobb angle or the progression risk factor: both parameters decreased to the smallest values in the case of symmetric ESR1 or ESR2 expression, while they increased with increasing expression asymmetry. In conclusion, the ESR1 and ESR2 presence was confirmed in skeletal paravertebral muscles of patients with idiopathic scoliosis. The increased expression level and asymmetry of estrogen receptors in deep skeletal muscles was related to increasing scoliotic deformity magnitude or increasing risk of deformity deterioration. These findings may highlight the etiopathogenesis of IS in children.

Melatonin and adolescent idiopathic scoliosis: The present evidence

INTRODUCTION

Adolescent idiopathic scoliosis (AIS) is a multifactorial condition with genetic predisposing factors, and several causes have been put forward for its aetiopathogenesis, including possible hormonal dysfunction. Melatonin seems to play significant role in AIS.

METHODS

A systematic search in different database, to July 2021, was performed to define the role of melatonin in the pathophysiology of adolescent idiopathic scoliosis. Eight suitable studies were identified.

RESULTS

The concentration and rhythm of melatonin secretion can play an important role by influencing the pathogenesis of adolescent idiopathic scoliosis.

CONCLUSIONS

Although there are many alterations of melatonin in subjects with adolescent idiopathic scoliosis, the many variables present do not allow to establish a direct cause-effect relationship.

LEVEL OF EVIDENCE

Level IV.

The role of endocrine hormones in the pathogenesis of adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a common spinal deformity characterized by changes in the three-dimensional structure of the spine. It usually initiates during puberty, the peak period of human growth when the secretion of numerous hormones is changing, and it is more common in females than in males. Accumulating evidence shows that the abnormal levels of many hormones including estrogen, melatonin, growth hormone, leptin, adiponectin and ghrelin, may be related to the occurrence and development of AIS. The purpose of this review is to provide a summary and critique of the research published on each hormone over the past 20 years, and to highlight areas for future study. It is hoped that the presentation will help provide a better understanding of the role of endocrine hormones in the pathogenesis of AIS.

Plasma proteomics analysis of adolescent idiopathic scoliosis patients revealed by Quadrupole-Orbitrap mass spectrometry

OBJECTIVE

We aim to investigate the changes of plasma proteome among mild, severe adolescent idiopathic scoliosis (AIS) patients and healthy controls.

METHODS

In this retrospective study, there were 84 individuals including 56 confirmed AIS patients (27 follow-up AIS patients and 29 surgical AIS patients) and another 28 healthy teenagers. Plasma samples were obtained and Quadrupole-Orbitrap Mass Spectrometer was performed to identify proteins in AIS patients and control group. T-test and ANOVA were performed to screen for differential proteins. GO and KEGG pathway, Pearson's correlation analysis and PLS model were applied to identify enriched proteins, investigate correlation between proteins and Cobb angles. ELISA was performed to further verify the quantitative proteomics results.

RESULTS

A total of 349 proteins were identified, among which 55 protein levels changed significantly in AIS group, compared with control group. Post hoc test indicated 36 proteins were significantly different between surgical and control group, 35 proteins between follow-up and control group. Fibronectin, fibrinogen and calmodulin were statistically different among three groups through mass spectrometry and were positively correlated with the Cobb angle.

CONCLUSIONS

We performed the proteomic study and revealed that fibronectin, fibrinogen and calmodulin might not only be considered as biomarkers for AIS but could be correlated with curve severity.

Exome sequencing analysis identifies frequent oligogenic involvement and FLNB variants in adolescent idiopathic scoliosis

Background

Adolescent idiopathic scoliosis (AIS) is a genetically heterogeneous disease characterised by three-dimensional deformity of the spine in the absence of a congenital spinal anomaly or neurological musculoskeletal disorder. The clinical variability and incomplete penetrance of some genes linked with AIS indicate that this disease constitutes an oligogenic trait.

Objective

We aimed to explore the oligogenic nature of this disease and identify novel AIS genes.

Methods

We analysed rare damaging variants within AIS-associated genes by using exome sequencing in 40 AIS trios and 183 sporadic patients.

Results

Multiple variants within AIS-associated genes were identified in eight AIS trios, and five individuals harboured rare damaging variants in the FLNB gene. The patients showed more frequent oligogenicity than the controls. In the gene-based burden test, the top signal resided in FLNB. In functional studies, we found that the AIS-associated FLNB variants altered the protein’s conformation and subcellular localisation and its interaction with other proteins (TTC26 and OFD1) involved in AIS. The most compelling evidence of an oligogenic basis was that the number of rare damaging variants was recognised as an independent prognostic factor for curve progression in Cox regression analysis.

Conclusion

Our data indicate that AIS is an oligogenic disease and identify FLNB as a susceptibility gene for AIS.

GENETIC ASPECTS OF IDIOPATHIC ESCOLIOSIS - A LITERATURE REVIEW

ABSTRACT The idiopathic scoliosis (IS) is the most common form of spinal deformity. The pathogenesis of IS is still poorly understood. Several studies show evidence that the genetic component is determinant to the development of IS. In this setting, a crescent focus has been placed on the identification of genes, associated genetic polymorphisms, and multiple susceptibility loci. This review highlights the genes and genetic polymorphisms currently studied, identified as influential in the genesis of IS, such as MMP-3, IL-6, type I collagen, and vitamin D and estrogen receptors. We concluded that IS remains a complex disease with a polygenic background and that genetic polymorphisms are intrinsically related to this condition. Level of evidence III; Narrative Review.

Could the Clinical Effectiveness Be Improved Under the Integration of Orthotic Intervention and Scoliosis-Specific Exercise in Managing Adolescent Idiopathic Scoliosis?: A Randomized Controlled Trial Study

OBJECTIVE

The aim of the study was to compare the effectiveness of the integration of orthotic intervention and scoliosis-specific exercise with orthotic intervention only via assessing the spinal deformity, back muscle endurance, and pulmonary function of the patients with adolescent idiopathic scoliosis.

DESIGN

It is a prospective randomized controlled study. Patients who fulfilled the SRS criteria for orthotic intervention were randomly assigned to the orthosis combined with exercise group (combined orthotic and exercise intervention) or the orthotic intervention group (orthotic intervention only). All the subjects were prescribed with a rigid thoracolumbosacral orthosis and scoliosis-specific exercise program was provided to the subjects in the orthosis combined with exercise group. Cobb angle, back muscle endurance, and pulmonary function of subjects were measured at baseline, 1-mo, and 6-mo follow-up visits.

RESULTS

After 6 mos of intervention, the subjects in the orthosis combined with exercise group showed better Cobb angle correction than those in the orthotic intervention group. The back muscle endurance and pulmonary function decreased in the subjects of the orthotic intervention group, whereas some improvement happened in the subjects of the orthosis combined with exercise group. Between-group statistical significance was detected at the 6-mo follow-up among back muscle endurance time and parameters of pulmonary function.

CONCLUSIONS

In this study, orthotic intervention combined with scoliosis-specific exercise offered better Cobb angle correction and improvement of the respiratory parameters and back muscle endurance of the patients with adolescent idiopathic scoliosis as compared with orthotic intervention only.

Etiology of Adolescent Idiopathic Scoliosis: A Literature Review

Adolescent idiopathic scoliosis (AIS) is the peripubertal development of spinal curvature of a minimum of 10°. AIS is thought to be attributable to genetic factors, nutrition, early exposure to toxins, and hormonal dysregulation. Recent literature suggests these factors may compound to determine both disease onset and severity. Currently, treatment is limited to observation, bracing, and surgical intervention. Intervention is presently determined by severity and risk of curve progression. As they emerge, new therapies may target specific etiologies of AIS.

Imbalanced development of anterior and posterior thorax is a causative factor triggering scoliosis

Objective

Scoliosis is a common disease characterized by spinal curvature with variable severities. There is no generally accepted theory about the physical origin of the spinal deformation of scoliosis. The aim of this study was to explore a new hypothesis suggesting that the curvatures in scoliosis may be associated with the imbalance growth between thoracic vertebral column and sternum.

Methods

We undertook a comparative computed tomography (CT) based morphology study of thoracic vertebrae and sternum of patients with adolescent idiopathic scoliosis (AIS) and age-gender matched normal subjects. We further measured the ratios between the lengths of the sternum and thoracic vertebra of mice with deficiency of fibroblast growth factor receptor 3 (FGFR3), which exhibit scoliosis. Three-week-old C57BL/6J mice were used to generate bipedal and sternal growth plate injury model. Radiographs and histological images were obtained to observe the presence of sternal and spinal deformity.

Results

There was a significant correlation between the severities of scoliosis and the ratios of the sternum to thoracic vertebral lengths. We also found that FGFR3 deficient mice showed smaller ratio of the sternum to thoracic vertebra lengths than that of the wild-type mice, which were similar with that of the AIS patients. Surgery-induced injuries of sternal growth plates can accelerate and aggravate the scoliosis in bipedal mice and imbalanced development of anterior and posterior thoracic occurred before the appearance of scoliosis.

Conclusions

Our findings suggest that the imbalanced growth between the thoracic vertebral column and the sternum is an important causative factor for the pathogenesis of scoliosis including AIS.

The translational potential of this article

Imbalanced growth between the thoracic vertebral column and the sternum is associated with scoliosis. Surgical or rehabilitation intervention for scoliosis should focus on all components involved in the pathogenesis of curvature to obtain better outcome.

Radiologic comparison of posterior release, internal distraction, final PSO and spinal fusion with one-stage posterior vertebral column resection for multi-level severe congenital scoliosis

Background

To compare radiologic results of posterior release, internal distraction, and final pedicle subtraction osteotomy (PSO) and spinal fusionwith one-stage posterior vertebral column resection (PVCR) in treating multi-level severe congenital scoliosis.

Methods

Forty-onesevere congenital scoliosis patients were used in the study. Group A comprised 24 patients who underwent one-stage PVCR. Group B comprised 17 patients who underwent posterior release with internal distraction, followed by final posterior fusion and instrumentation. The average preoperative main curve was 110.4° (95–130°) in group A and 109.4° (range 90°–126°) in group B. Postoperative follow-up time was ≥2 years (2.0–4.5 years) to analyze the radiographic and clinical outcomes.

Results

A comparison of posterior release, internal distraction, and final spinal fusion with PVCR showed no significant differences in postoperative main curve and compensatory caudal curve correction, coronal and sagittal imbalance. However, significant differences were found between the 2 groups in compensatory cranial curve correction.

Conclusions

Posterior release, internal distraction, and final spinal fusion produce better corrective results in compensatory cranial curve correction than PVCR in treating severe multi-level congenital scoliosis.