Biochemistry of adolescent idiopathic scoliosis

Rare variant association analyses reveal the significant contribution of carbohydrate metabolic disturbance in severe adolescent idiopathic scoliosis

BACKGROUND

Adolescent idiopathic scoliosis (AIS), the predominant genetic-influenced scoliosis, results in spinal deformities without vertebral malformations. However, the molecular aetiology of AIS remains unclear.

METHODS

Using genome/exome sequencing, we studied 368 patients with severe AIS (Cobb angle >40°) and 3794 controls from a Han Chinese cohort. We performed gene-based and pathway-based weighted rare variant association tests to assess the mutational burden of genes and established biological pathways. Differential expression analysis of muscle tissues from 14 patients with AIS and 15 controls was served for validation.

RESULTS

SLC16A8, a lactate transporter linked to retinal glucose metabolism, was identified as a novel severe AIS-associated gene (p=3.08E-06, false discovery rate=0.009). Most AIS cases with deleterious SLC16A8 variants demonstrated early onset high myopia preceding scoliosis. Pathway-based burden test also revealed a significant enrichment in multiple carbohydrate metabolism pathways, especially galactose metabolism. Patients with deleterious variants in these genes demonstrated a significantly larger spinal curve. Genes related to catabolic processes and nutrient response showed divergent expression between AIS cases and controls, reinforcing our genomic findings.

CONCLUSION

This study uncovers the pivotal role of genetic variants in carbohydrate metabolism in the development of AIS, unveiling new insights into its aetiology and potential treatment.

The Role of Muscle Biomarkers in Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis (AIS) is the predominant orthopedic disorder in children, affecting 1-3% of the global population. Research in this field has tried to delineate the genetic factors behind scoliosis and its association with heredity since AIS is considered a polygenic disease and has different genetic and epigenetic factors. The current study conducted a narrative review of the literature, focusing on biomarkers in the pathophysiology of muscle in AIS patients. Articles were collected from Scopus, Pubmed, and Web of Science. The key screening parameters were scoliosis classification, sampling, and the biomarkers evaluated. This review emphasizes potential key mechanisms and molecular regulators in muscle tissue. While there has been limited focus on the proteins contributing to muscle changes in AIS, significant attention has been given to genomic studies of single-nucleotide polymorphisms, particularly in LBX1. Despite these efforts, the exact causes of AIS remain elusive, with several theories suggesting genetic and hormonal factors. This review identified critical protein biomarkers such as Gi-protein alpha subunits, fibrillin-1 and -2, and various differentially expressed proteins, which may be linked to muscle alterations in AIS. This field of research is still limited due to a lack of homogeneity in the distinction of patients by groups and curve severity. Although the pathophysiology of AIS is still unclear, molecular research is important to guide the treatment of AIS before achieving skeletal maturity, thus avoiding serious problems associated with posture changes and low quality of life. In the future, a more comprehensive synergy between orthopedic and molecular research might ameliorate the diagnosis and treatment of AIS patients.

The Human Microbiome and Its Role in Musculoskeletal Disorders

Musculoskeletal diseases (MSDs) are characterized as injuries and illnesses that affect the musculoskeletal system. MSDs affect every population worldwide and are associated with substantial global burden. Variations in the makeup of the gut microbiota may be related to chronic MSDs. There is growing interest in exploring potential connections between chronic MSDs and variations in the composition of gut microbiota. The human microbiota is a complex community consisting of viruses, archaea, bacteria, and eukaryotes, both inside and outside of the human body. These microorganisms play crucial roles in influencing human physiology, impacting metabolic and immunological systems in health and disease. Different body areas host specific types of microorganisms, with facultative anaerobes dominating the gastrointestinal tract (able to thrive with or without oxygen), while strict aerobes prevail in the nasal cavity, respiratory tract, and skin surfaces (requiring oxygen for development). Together with the immune system, these bacteria have coevolved throughout time, forming complex biological relationships. Changes in the microbial ecology of the gut may have a big impact on health and can help illnesses develop. These changes are frequently impacted by lifestyle choices and underlying medical disorders. The potential for safety, expenses, and efficacy of microbiota-based medicines, even with occasional delivery, has attracted interest. They are, therefore, a desirable candidate for treating MSDs that are chronic and that may have variable progression patterns. As such, the following is a narrative review to address the role of the human microbiome as it relates to MSDs.

Patient outcomes in idiopathic scoliosis are associated with biological endophenotypes: 2020 SOSORT award winner

PURPOSE

Bracing is the treatment of choice for idiopathic scoliosis (IS), unfortunately factors underlying brace response remain unknown. Clinicians are currently unable to identify patients who may benefit from bracing, and therefore, better molecular stratification is critically needed. The aim of this study is to evaluate IS patient outcomes at skeletal maturity in relation to biological endophenotypes, and determine specific endophenotypes associated to differential bracing outcomes. This is a retrospective cohort with secondary cross-sectional comparative studies.

METHODS

Clinical and radiological data were collected from 563 IS patients, stratified into biological endophenotypes (FG1, FG2, FG3) based on a cell-based test. Measured outcomes were maximum Cobb angle at skeletal maturity, and if severe, spinal deformity (≥ 45°) or surgery was attained. Treatment success/failure was determined by standard progression thresholds (Cobb ≥ 45° or surgery; Cobb angle progression ≥ 6°). Multivariable analyses were performed to evaluate associations between endophenotypes and clinical outcome.

RESULTS

Higher Cobb angles at maturity for FG1 and FG2 patients were observed (p = 0.056 and p = 0.05), with increased likelihood of ≥ 45° and/or surgery for FG1 (OR = 2.181 [1.002-4.749] and FG2 (OR = 2.141 [1.038-4.413]) compared to FG3. FG3 was 9.31 [2.58-33.61] and 5.63 [2.11-15.05] times more likely for bracing success at treatment termination and based on the < 6° progression criterion, respectively, compared to FG1.

CONCLUSION

Associations between biological endophenotypes and outcomes suggest differences in progression and/or bracing response among IS patients. Outcomes were most favorable in FG3 patients. The results pave the way for establishing personalized treatments, distinguishing who may benefit or not from treatment.

Altered physiology of mesenchymal stem cells in the pathogenesis of adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis is the most common spinal deformity during puberty, especially in females. It is characterized by aberrant skeletal growth and generalized reduced bone density, which is associated with impaired bone mineral metabolism. Despite recent progress in multidisciplinary research to support various hypotheses, the pathogenesis of Adolescent idiopathic scoliosis is still not clearly understood. One of the hypothesis is to study the role of mesenchymal stem cells due to its involvement in the above-mentioned bone metabolic abnormalities. In this review, we will summarize reported literatures on the role of mesenchymal stem cells, particularly in the pathogenesis of Adolescent idiopathic scoliosis. In addition, we will describe the research on mesenchymal stem cells of Adolescent idiopathic scoliosis performed using bioinformatics tools.

Advances in Sensing Technologies for Monitoring of Bone Health

: Changing lifestyle and food habits are responsible for health problems, especially those related to bone in an aging population. Poor bone health has now become a serious matter of concern for many of us. In order to avoid serious consequences, the early prediction of symptoms and diagnosis of bone diseases have become the need of the hour. From this inspiration, the evolution of different bone health monitoring techniques and measurement methods practiced by researchers and healthcare companies has been discussed. This paper focuses on various types of bone diseases along with the modeling and remodeling phenomena of bones. The evolution of various diagnosis tests for bone health monitoring has been also discussed. Various types of bone turnover markers, their assessment techniques, and recent developments for the monitoring of biochemical markers to diagnose the bone conditions are highlighted. Then, the paper focuses on the potential assessment of the recent sensing techniques (physical sensors and biosensors) that are currently available for bone health monitoring. Considering the importance of electrochemical biosensors in terms of high sensitivity and reliability, specific attention has been given to the recent development of electrochemical biosensors and significance in real-time monitoring of bone health.

Emerging roles of non-coding RNAs in scoliosis

Scoliosis, a complex three‐dimensional deformity of the spine with the Cobb angle (a measure of the spinal lateral curvature) >10 degree, encompasses a spectrum of pathologies, including congenital, idiopathic, syndromic and neuromuscular aetiologies. The pathogenesis is multifactorial involving both environmental and genetic factors but the exact cellular and molecular mechanisms of disease development remain largely unknown. Emerging evidence showed that non‐coding RNAs (ncRNAs), namely microRNAs, long ncRNAs and circular RNAs, are deregulated in many orthopaedic diseases, including scoliosis. Importantly, these deregulated ncRNAs functionally participate in the initiation and progression of scoliosis. Here, we review recent progress in ncRNA research on scoliosis.

Alterations of the gut microbiome and plasma proteome in Chinese patients with adolescent idiopathic scoliosis

The etiology of adolescent idiopathic scoliosis (AIS), the most common rotational deformity of the spine, is still unclear. Emerging evidence suggests that gut microbiota dysbiosis influences musculoskeletal diseases such as arthritis and osteoporosis. However, the alterations of the fecal microbiome in AIS remain unknown. Thus, the current study was conducted to explore the gut microbiota compositions of Chinese AIS patients. Microbiota communities in the feces of 51 AIS patients and 34 age- and sex-matched healthy individuals were investigated using 16S rRNA sequencing. Meanwhile, the changes in the plasma proteome were detected using tandem mass tag (TMT) labeling coupled with liquid chromatography-mass spectrometry (LC-MS). The relationship between gut microbiota and AIS clinical characteristics as well as the correlation between gut microbiota and the changes in plasma proteins were analyzed. The structure of the gut microbiota differed between the AIS and healthy groups, however, the richness was similar. The genera Prevotella, Gelria, and Desulfovibrio were enriched in the feces of AIS patients. In contrast, the abundance of Parasutterella, Tyzzerella, and Phascolarctobacterium was decreased in the AIS group. More remarkably, a positive correlation between the abundance of the fecal genera Prevotella and the Cobb angles of the AIS patients was observed. Moreover, the major differential plasma proteins related to AIS were Fibronectin 1 (FN1), voltage-dependent anion channel 1 (VDAC1), Ras homolog family member A (RHOA), and AHNAK nucleoprotein (AHNAK). Additionally, the positive correlations between fecal Prevotella and the expression of host plasma FN1 as well as the negative relationships between fecal Prevotella and the expression of host VDAC1 and AHNAK were confirmed. Elucidating these differences in the gut microbiota will provide a foundation to improve our understanding of the pathogenesis of AIS and to support potential therapeutic options based on modifying the gut microbiota.

Clinical outcomes of posterior pedicle screw instrumentation without osteotomy in the management of adolescent idiopathic scoliosis

The aim of the study was to identify the effectiveness of posterior pedicle screw instrumentation without osteotomy in the management of adolescent idiopathic scoliosis (AIS).The AIS patients underwent standing anteroposterior and lateral radiography before and after surgery. Age, sex, Lenke type, preoperative and postoperative Cobb angle, and all the related complications were recorded at final follow-up.We investigated data from 137 AIS patients who underwent posterior pedicle screw instrumentation without osteotomy from January 2012 to January 2016 with >2 years follow-up. Mean age was 14.3 ± 1.5 years at operation. The preoperative and latest postoperative coronal Cobb angle was 60 ± 12° and 9 ± 5°, respectively. Additionally, complications were noted in 6 patients. However, the prognosis of all the AIS patients was good, and the satisfaction of the Scoliosis Research Society Outcomes Instrument (SRS-22) questionnaire was 4.4 ± 0.5 at final follow-up.In the management of mild and moderate AIS, satisfactory clinical results can be obtained using posterior pedicle screw instrumentation without osteotomy.

Association between polymorphisms in vitamin D receptor gene and adolescent idiopathic scoliosis: a meta-analysis

PURPOSE

This meta-analysis was performed to clarify whether the two single nucleotide polymorphisms (ApaI and BsmI) in vitamin D receptor (VDR) gene conferred susceptibility to adolescent idiopathic scoliosis (AIS).

METHODS

A comprehensive literature search in five online databases (PubMed, EMBASE, ISI Web of Science, CNKI, and Wanfang) was performed to identify studies that analyzed the association between VDR gene polymorphisms and risk of AIS. Observational studies met the predetermined inclusion criteria were selected for meta-analysis. The most appropriate genetic model was identified using a genetic model-free approach. Meta-analysis was performed using RevMan 5.3 software.

RESULTS

Five eligible studies were included in this meta-analysis, which involved a total of 717 cases and 554 controls. A statistically significant association was observed between BsmI polymorphism and AIS (OR 1.90, 95% CI 1.32, 2.62). In subgroup analysis by ethnicity, the association between BsmI polymorphism and AIS was significant in Asians (OR 2.06, 95% CI 1.56, 2.73) but not in Caucasians (OR 0.70, 95% CI 0.23, 2.19). However, the ApaI polymorphism was not associated with AIS. Moreover, no evidence of association between BMD and the two VDR gene polymorphisms was detected.

CONCLUSIONS

Meta-analysis of existing data suggested that BsmI was associated with increased risk of AIS in Asian populations. Nevertheless, further studies with rigorous design and more ethnic groups are encouraged to validate our findings. These slides can be retrieved under Electronic Supplementary Material.

Comparison of segmental spinal movement control in adolescents with and without idiopathic scoliosis using modified pressure biofeedback unit

Background

Postural rehabilitation emphasizing on motor control training of segmental spinal movements has been proposed to effectively reduce the scoliotic spinal deformities in adolescent idiopathic scoliosis (AIS). However, information regarding the impairments of segmental spinal movement control involving segmental spinal stabilizers in adolescent idiopathic scoliosis remains limited. Examination of segmental spinal movement control may provide a window for investigating the features of impaired movement control specific to spinal segments that may assist in the development of physiotherapeutic management of AIS.

Objectives

To compare segmental spinal movement control in adolescents with and without idiopathic scoliosis using modified pressure biofeedback unit.

Methods

Segmental spinal movement control was assessed in twenty adolescents with idiopathic scoliosis (AISG) and twenty healthy adolescents (CG) using a modified pressure biofeedback unit. Participants performed segmental spinal movements that primarily involved segmental spinal stabilizing muscles with graded and sustained muscle contraction against/off a pressure cuff from baseline to target pressures and then maintained for 1 min. Pressure data during the 1-minute maintenance phase were collected for further analysis. Pressure deviation were calculated and compared between groups.

Results

The AISG had significantly greater pressure deviations for all segmental spinal movements of cervical, thoracic, and lumbar spine than the CG.

Conclusion

Pressure biofeedback unit was feasible for assessing segmental spinal movement control in AIS. AISG exhibited poorer ability to grade and sustain muscle activities for local movements of cervical, thoracic, and lumbar spine, suggesting motor control training of segmental spinal movements involving segmental spinal stabilizing muscles on frontal, sagittal, and transverse planes were required.

Genetics and pathogenesis of idiopathic scoliosis

Idiopathic scoliosis (IS), the most common spinal deformity, affects otherwise healthy children and adolescents during growth. The aetiology is still unknown, although genetic factors are believed to be important. The present review corroborates the understanding of IS as a complex disease with a polygenic background. Presumably IS can be due to a spectrum of genetic risk variants, ranging from very rare or even private to very common. The most promising candidate genes are highlighted.

Sensorimotor Control Impairment in Young Adults With Idiopathic Scoliosis Compared With Healthy Controls

OBJECTIVE

It has been hypothesized that the impaired sensorimotor control observed in adolescents with idiopathic scoliosis (IS) may be related more to the onset of scoliosis than to the maturation of sensory systems or sensorimotor control mechanisms. The objective of this study was to assess sensorimotor control in adults diagnosed with IS in adolescence versus healthy controls.

METHODS

The study included 20 young adults 20 to 24 years of age (10 healthy controls and 10 diagnosed with adolescent IS but not treated for it). Binaural bipolar galvanic vestibular stimulation (GVS) was delivered to assess sensorimotor control. Vertical forces under each foot and upper body kinematics along the frontal plane were measured before GVS (2-second window), during GVS (2-second window), immediately after the cessation of GVS (1-second window), and during the following 2 seconds. Balance control was assessed by calculating the root mean square values of vertical forces and upper body kinematics.

RESULTS

Compared with healthy controls, the IS group showed greater body sway upon GVS; the amplitude of this sway was even greater immediately after the cessation of GVS-an outcome requiring sensorimotor control.

CONCLUSION

Compared with normal controls, adults who had been diagnosed with IS in adolescence showed altered balance control immediately following GVS. This finding suggests that dysfunctional sensorimotor control may be related to the onset of scoliosis rather than to a transient suboptimal development of the sensory systems or sensorimotor control mechanisms.

Understanding the role of the immune system in adolescent idiopathic scoliosis: Immunometabolic CONnections to Scoliosis (ICONS) study protocol

INTRODUCTION

Adolescent idiopathic scoliosis (AIS) affects up to 3% of children around the world. There is limited knowledge of AIS aetiopathogenesis, and this evidence is needed to develop new management strategies. Paraspinal muscle in AIS demonstrates evidence of differential fibrosis based on curve sidedness. Fibrosis is the hallmark of macrophage-driven inflammation and tissue remodelling, yet the mechanisms of fibrosis in paraspinal muscle in AIS are poorly understood.

OBJECTIVES

The primary objective of this study is to determine the influence of curve sidedness on paraspinal muscle inflammation. Secondary objectives include defining the mechanisms of macrophage homing to muscle, and determining muscle-macrophage crosstalk in muscle fibrosis in AIS.

METHODS AND ANALYSIS

This is a cross-sectional study conducted in a tertiary paediatric centre in Hamilton, Ontario, Canada. We will recruit boys and girls, 10-17 years of age, who are having surgery to correct AIS. We will exclude children who have an active infection or are on immunosuppressive therapies within 2 weeks of surgery, smokers and pregnant girls. Paraspinal muscle biopsies will be obtained at the start of surgery. Also, blood and urine samples will be collected from participants, who will fill questionnaires about their lifestyle. Anthropometric measures will also be collected including height, weight, waist and hip circumferences.

ETHICS AND DISSEMINATION

This study has received ethics authorisation by the institutional review board. This work will be published in peer-reviewed journals and will be presented in oral and poster formats at scientific meetings.

DISCUSSION

This study will explore the mechanisms of paraspinal muscle inflammation, remodelling and fibrosis in AIS. This will help identify pathways and molecules as potential therapeutic targets to treat and prevent AIS. It may also yield markers that predict scoliosis progression and response to treatment in these children.

Abnormal osteogenic and chondrogenic differentiation of human mesenchymal stem cells from patients with adolescent idiopathic scoliosis in response to melatonin

Abnormalities of membranous and endochondral ossification in patients with adolescent idiopathic scoliosis (AIS) remain incompletely understood. To investigate abnormalities in the melatonin signaling pathway and cellular response to melatonin in AIS, a case-control study of osteogenic and chondrogenic differentiation was performed using human mesenchymal stem cells (hMSCs). AIS was diagnosed by physical and radiographic examination. hMSCs were isolated from the bone marrow of patients with AIS and control subjects (n=12 each), and purified by density gradient centrifugation. The expression levels of melatonin receptors (MTs) 1 and 2 were detected by western blotting. Osteogenic and chondrogenic differentiation was induced by culturing hMSCs in osteogenic and chondrogenic media containing vehicle or 50 nM melatonin. Alkaline phosphatase (ALP) activity assays, quantitative glycosaminoglycan (GAG) analysis, and reverse transcription-quantitative polymerase chain reaction analysis were performed. Compared with controls, MT2 demonstrated low expression in the AIS group. Melatonin increased ALP activity, GAG synthesis and upregulated the expression of genes involved in osteogenic and chondrogenic differentiation including, ALP, osteopontin, osteocalcin, runt-related transcription factor 2, collagen type II, collagen type X, aggrecan and sex-determining region Y-box 9 in the normal control hMSCs, but did not affect the AIS groups. Thus, AIS hMSCs exhibit abnormal cellular responses to melatonin during osteogenic and chondrogenic differentiation, which may be associated with abnormal membranous and endochondral ossification, and skeletal growth. These results indicate a potential modulating role of melatonin via the MT2 receptor on abnormal osteogenic and chondrogenic differentiaation in patients with AIS.

Adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is the most common form of structural spinal deformities that have a radiological lateral Cobb angle - a measure of spinal curvature - of ≥10(°). AIS affects between 1% and 4% of adolescents in the early stages of puberty and is more common in young women than in young men. The condition occurs in otherwise healthy individuals and currently has no recognizable cause. In the past few decades, considerable progress has been made towards understanding the clinical patterns and the three-dimensional pathoanatomy of AIS. Advances in biomechanics and technology and their clinical application, supported by limited evidence-based research, have led to improvements in the safety and outcomes of surgical and non-surgical treatments. However, the definite aetiology and aetiopathogenetic mechanisms that underlie AIS are still unclear. Thus, at present, both the prevention of AIS and the treatment of its direct underlying cause are not possible.

Idiopathic scoliosis and the vestibular system

PURPOSE

Despite its high prevalence, the etiology underlying idiopathic scoliosis remains unclear. Although initial scrutiny has focused on genetic, biochemical, biomechanical, nutritional and congenital causes, there is growing evidence that aberrations in the vestibular system may play a role in the etiology of scoliosis. In this article, we discuss putative mechanisms for adolescent idiopathic scoliosis and review the current evidence supporting a role for the vestibular system in adolescent idiopathic scoliosis.

METHODS

A comprehensive search of the English literature was performed using PubMed ( http://www.ncbi.nlm.nih.gov/pubmed ). Research articles studying interactions between adolescent idiopathic scoliosis and the vestibular system were selected and evaluated for inclusion in a literature review.

RESULTS

Eighteen manuscripts of level 3-4 clinical evidence to support an association between adolescent idiopathic scoliosis (AIS) and dysfunction of the vestibular system were identified. These studies include data from physiologic and morphologic studies in humans. Clinical data are supported by animal model studies to suggest a causative link between the vestibular system and AIS.

CONCLUSIONS

Clinical data and a limited number of animal model studies suggest a causative role of the vestibular system in AIS, although this association has not been reproduced in all studies.

Segmental torso masses in adolescent idiopathic scoliosis

BACKGROUND

Adolescent idiopathic scoliosis is the most common type of spinal deformity whose aetiology remains unclear. Studies suggest that gravitational forces in the standing position play an important role in scoliosis progression, therefore anthropometric data is required to develop biomechanical models of the deformity. Few studies have analysed the trunk by vertebral level and none have performed investigations of the scoliotic trunk. The aim of this study was to determine the centroid, thickness, volume and estimated mass, for sections of the scoliotic trunk.

METHODS

Existing low-dose CT scans were used to estimate vertebral level-by-level torso masses for 20 female adolescent idiopathic scoliosis patients. ImageJ processing software was used to analyse the CT images and enable estimation of the segmental torso mass corresponding to each vertebral level.

FINDINGS

The patients' mean age was 15.0 (SD 2.7) years with mean major Cobb angle of 52 (SD 5.9)° and mean patient weight of 58.2 (SD 11.6) kg. The magnitude of torso segment mass corresponding to each vertebral level increased by 150% from 0.6kg at T1 to 1.5kg at L5. Similarly, segmental thickness from T1-L5 increased inferiorly from a mean 18.5 (SD 2.2) mm at T1 to 32.8 (SD 3.4) mm at L5. The mean total trunk mass, as a percentage of total body mass, was 27.8 (SD 0.5) % which was close to values reported in previous literature.

INTERPRETATION

This study provides new anthropometric reference data on segmental (vertebral level-by-level) torso mass in adolescent idiopathic scoliosis patients, useful for biomechanical models of scoliosis progression and treatment.

Otolith dysfunction as a possible cause for the development of idiopathic scoliosis

BACKGROUND

To investigate whether otolith system, as a major contributor to muscles for postural control, might play a role in the pathogenesis of idiopathic scoliosis (IS).

METHODS

Cervical vestibular-evoked myogenic potentials (VEMP) testing was applied to investigate the otolith function in patients with IS. Twenty-nine healthy patients (mean age 13.5±2.5 y, 4 males) were included. In all but 2 patients, the major curve deviation was to the right and the mean angle deviation was 49.7±21.6 degrees. Nineteen age-matched individuals (10 males) served as controls.

RESULTS

The P13 (first positive wave) latencies were comparable in both groups. Patients with IS had significantly longer N23 (first negative wave) latencies than controls. A high correlation between the age and N23 latencies on the right was found in IS patients. A link between the scoliosis angle and VEMP latencies could not be demonstrated.The VEMP amplitudes were higher in patients than in controls, whereas the amplitude asymmetry ratio was similar in both groups.

CONCLUSIONS

This work brings further evidence for vestibular abnormalities in patients with IS. Prospective studies are needed to elucidate a possible causative relationship between otolith dysfunction and the development of scoliosis.

LEVEL OF EVIDENCE

III.

Body mass index in relation to truncal asymmetry of healthy adolescents, a physiopathogenetic concept in common with idiopathic scoliosis: summary of an electronic focus group debate of the IBSE

There is no generally accepted scientific theory for the cause of adolescent idiopathic scoliosis (AIS). As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE).introduced the electronic focus group (EFG) as a means of increasing debate on knowledge of important topics. This has been designated as an on-line Delphi discussion. The text for this debate was written by Dr TB Grivas. It is based on published research from Athens, Greece evaluating schoolchildren age 11-17 years for the relation of body mass index (BMI) to each of truncal asymmetry (TA) and menarcheal status. Girls with relatively lower BMI were found to have a significant excess of severe TAs and significantly later menarche confirming the well-known relation of BMI to menarche. Together with other evidence linking nutritional status to skeletal growth, the observations suggest energy balance via the hypothalamus is related to trunk asymmetry. As with a recent speculative hypothesis for the pathogenesis of AIS in girls, Grivas et al. suggest that the severe TAs involve a genetically-determined selectively increased sensitivity (up-regulation) of the hypothalamus to circulating leptin with asymmetry as an adverse response to stress (hormesis). The TA is expressed bilaterally via the sympathetic nervous system to produce left-right asymmetry in ribs and/or vertebrae leading to severe TAs when beyond the capacity of postural mechanisms of the somatic nervous system to control the shape distortion in the trunk. This EFG discusses the findings and interpretations of the paper by Grivas and colleagues as research at the borderland between the genesis of TA (physiogenesis) and AIS (pathogenesis). It is suggested that TAs, here regarded in common with AIS, result from the combination of secondary sexual development affecting body composition, adolescent skeletal growth velocity, and an asymmetry process. The possible involvement of epigenetic factors is not considered.

Whither the etiopathogenesis (and scoliogeny) of adolescent idiopathic scoliosis? Incorporating presentations on scoliogeny at the 2012 IRSSD and SRS meetings

This paper aims to integrate into current understanding of AIS causation, etiopathogenetic information presented at two Meetings during 2012 namely, the International Research Society of Spinal Deformities (IRSSD) and the Scoliosis Research Society (SRS). The ultimate hope is to prevent the occurrence or progression of the spinal deformity of AIS with non-invasive treatment, possibly medical. This might be attained by personalised polymechanistic preventive therapy targeting the appropriate etiology and/or etiopathogenetic pathways, to avoid fusion and maintain spinal mobility. Although considerable progress had been made in the past two decades in understanding the etiopathogenesis of adolescent idiopathic scoliosis (AIS), it still lacks an agreed theory of etiopathogenesis. One problem may be that AIS results not from one cause, but several that interact with various genetic predisposing factors. There is a view there are two other pathogenic processes for idiopathic scoliosis namely, initiating (or inducing), and those that cause curve progression. Twin studies and observations of family aggregation have revealed significant genetic contributions to idiopathic scoliosis, that place AIS among other common disease or complex traits with a high heritability interpreted by the genetic variant hypothesis of disease. We summarize etiopathogenetic knowledge of AIS as theories of pathogenesis including recent multiple concepts, and blood tests for AIS based on predictive biomarkers and genetic variants that signify disease risk. There is increasing evidence for the possibility of an underlying neurological disorder for AIS, research which holds promise. Like brain research, most AIS workers focus on their own corner and there is a need for greater integration of research effort. Epigenetics, a relatively recent field, evaluates factors concerned with gene expression in relation to environment, disease, normal development and aging, with a complex regulation across the genome during the first decade of life. Research on the role of environmental factors, epigenetics and chronic non-communicable diseases (NCDs) including adiposity, after a slow start, has exploded in the last decade. Not so for AIS research and the environment where, except for monozygotic twin studies, there are only sporadic reports to suggest that environmental factors are at work in etiology. Here, we examine epigenetic concepts as they may relate to human development, normal life history phases and AIS pathogenesis. Although AIS is not regarded as an NCD, like them, it is associated with whole organism metabolic phenomena, including lower body mass index, lower circulating leptin levels and other systemic disorders. Some epigenetic research applied to Silver-Russell syndrome and adiposity is examined, from which suggestions are made for consideration of AIS epigenetic research, cross-sectional and longitudinal. The word scoliogeny is suggested to include etiology, pathogenesis and pathomechanism.

Normal leptin expression, lower adipogenic ability, decreased leptin receptor and hyposensitivity to Leptin in Adolescent Idiopathic Scoliosis

Leptin has been suggested to play a role in the etiology of Adolescent Idiopathic Scoliosis (AIS), however, the leptin levels in AIS girls are still a discrepancy, and no in vitro study of leptin in AIS is reported. We took a series of case-control studies, trying to understand whether Leptin gene polymorphisms are involved in the etiology of the AIS or the change in leptin level is a secondary event, to assess the level of leptin receptor, and to evaluate the differences of response to leptin between AIS cases and controls. We screened all exons of Leptin gene in 45 cases and 45 controls and selected six tag SNPs to cover all the observed variations. Association analysis in 446 AIS patients and 550 healthy controls showed no association between the polymorphisms of Leptin gene and susceptibility/severity to AIS. Moreover, adipogenesis assay of bone mesenchymal stem cells (MSCs) suggested that the adipogenic ability of MSCs from AIS girls was lower than controls. After adjusting the differentiation rate, expressions of leptin and leptin receptor were similar between two groups. Meanwhile, osteogenesis assay of MSC showed the leptin level was similar after adjusting the differentiation rate, but the leptin receptor level was decreased in induced AIS osteoblasts. Immunocytochemistry and western blot analysis showed less leptin receptors expressed in AIS group. Furthermore, factorial designed studies with adipogenesis and osteogenesis revealed that the MSCs from patients have no response to leptin treatment. Our results suggested that Leptin gene variations are not associated with AIS and low serum leptin probably is a secondary outcome which may be related to the low capability of adipogenesis in AIS. The decreased leptin receptor levels may lead to the hyposensitivity to leptin. These findings implied that abnormal peripheral leptin signaling plays an important role in the pathological mechanism of AIS.

AIS and spondylolisthesis

INTRODUCTION

The association of scoliosis and spondylolisthesis is well documented in literature; the nature and modalities of the relationship of the two pathologies are variable and not always clear. Also, etiologic particulars of scoliosis associated with spondylolisthesis are not well defined, even in cases where scoliosis is called idiopathic. In this paper, we review previous literature and discuss the different aspects of the mutual relationship of scoliosis and spondylolisthesis in the adolescent age.

MATERIALS AND METHODS

It is a common notion that the highest occurrence of scoliosis associated with spondylolisthesis is at the lumbar level, both in adolescent and in adult patients. It is probable that the scoliosis that is more heavily determined by the presence of spondylolisthesis is at the lumbar level and presents curve angle lower than 15° Cobb and mild rotation. The scoliosis with curve value over 15° Cobb that is present at the lumbar level in association with spondylolisthesis probably is not prominently due to spondylolisthesis: in these cases, spondylolisthesis is probably only partially responsible for scoliosis progression with a spasm mechanism and/or due to rotation of slipping "olisthetic" vertebra.

DISCUSSION

We think that the two pathologies should be treated separately, as stated by many other authors, but we would highlight the concept that, whatever be the scoliosis curve origin, spasm, olisthetic or mixed together, this origin has no influence on treatment. The curves should be considered, for all practical effects, as so-called idiopathic scoliosis. We think that generally patient care should be addressed to treat only spondylolisthesis or only scoliosis, if it is necessary on the basis of clinical findings and therapeutic indications of the isolated pathologies, completely separating the two diseases treatments.

CONCLUSIONS

Scoliosis should be considered as an independent disease; only in the case of scoliosis curve progression over time, associated scoliosis must be treated, according to therapeutic principles of the care of any so-called idiopathic scoliosis of similar magnitude, and a similar approach must be applied in the case of spondylolisthesis progression or painful spondylolisthesis.

Adolescent idiopathic scoliosis (AIS), environment, exposome and epigenetics: a molecular perspective of postnatal normal spinal growth and the etiopathogenesis of AIS with consideration of a network approach and possible implications for medical therapy

Genetic factors are believed to play an important role in the etiology of adolescent idiopathic scoliosis (AIS). Discordant findings for monozygotic (MZ) twins with AIS show that environmental factors including different intrauterine environments are important in etiology, but what these environmental factors may be is unknown. Recent evidence for common chronic non-communicable diseases suggests epigenetic differences may underlie MZ twin discordance, and be the link between environmental factors and phenotypic differences. DNA methylation is one important epigenetic mechanism operating at the interface between genome and environment to regulate phenotypic plasticity with a complex regulation across the genome during the first decade of life. The word exposome refers to the totality of environmental exposures from conception onwards, comprising factors in external and internal environments. The word exposome is used here also in relation to physiologic and etiopathogenetic factors that affect normal spinal growth and may induce the deformity of AIS. In normal postnatal spinal growth we propose a new term and concept, physiologic growth-plate exposome for the normal processes particularly of the internal environments that may have epigenetic effects on growth plates of vertebrae. In AIS, we propose a new term and concept pathophysiologic scoliogenic exposome for the abnormal processes in molecular pathways particularly of the internal environment currently expressed as etiopathogenetic hypotheses; these are suggested to have deforming effects on the growth plates of vertebrae at cell, tissue, structure and/or organ levels that are considered to be epigenetic. New research is required for chromatin modifications including DNA methylation in AIS subjects and vertebral growth plates excised at surgery. In addition, consideration is needed for a possible network approach to etiopathogenesis by constructing AIS diseasomes. These approaches may lead through screening, genetic, epigenetic, biochemical, metabolic phenotypes and pharmacogenomic research to identify susceptible individuals at risk and modulate abnormal molecular pathways of AIS. The potential of epigenetic-based medical therapy for AIS cannot be assessed at present, and must await new research derived from the evaluation of epigenetic concepts of spinal growth in health and deformity. The tenets outlined here for AIS are applicable to other musculoskeletal growth disorders including infantile and juvenile idiopathic scoliosis.