Differential proteome analysis in adolescent idiopathic scoliosis patients with thoracolumbar/lumbar curvatures

Metabolic Imbalances and Bone Remodeling Agents in Adolescent Idiopathic Scoliosis: A Study in Postmenarcheal Girls

The causes and mechanisms underlying adolescent idiopathic scoliosis (AIS) remain unclear, and the available information regarding metabolic imbalances in AIS is still insufficient. This investigation aimed to evaluate the concentrations of specific bone remodeling-related agents in postmenarcheal girls diagnosed with AIS. The study encompassed thirty-six scoliosis patients and eighteen age-matched healthy individuals assigned to the control group. The patients underwent clinical and radiological examinations to assess the degree of the spinal deformity, type of curvature, and skeletal maturity. Blood and urine samples were collected from all participants and serological markers were measured using an enzyme-linked immunosorbent assay. Our study results demonstrated that the balance of phosphate-calcium and parathormone levels seems normal in individuals with AIS. Furthermore, no statistically significant differences were observed in the content of Klotho protein, osteocalcin, osteoprotegerin, C-terminal telopeptide of type I collagen (CTX), sclerostin, and alkaline phosphatase. Nevertheless, the serum levels of vitamin D (25-OH-D) were lowered, while N-terminal propeptide of type I procollagen (PINP), and fibroblast growth factor-23 (FGF23) were increased in the AIS group, with p-values of 0.044, 0.001, and 0.022, respectively. This finding indicates the potential involvement of these factors in the progression of AIS, which necessitates further studies to uncover the fundamental mechanisms underlying idiopathic scoliosis.

Do Adolescent Idiopathic Scoliosis Patients With Vitamin D Deficiency Have Worse Spine Fusion Outcomes?

BACKGROUND

Prior research has shown that patients with adolescent idiopathic scoliosis (AIS) have a higher prevalence of vitamin D deficiency compared with healthy peers. In adult orthopaedic populations, vitamin D deficiency has been shown to be a risk factor for higher reported pain and lower function. We investigated whether there was an association between vitamin D levels and AIS patient-reported outcomes, as measured by the Scoliosis Research Society (SRS-30) questionnaire.

METHODS

This was a single-center, cross-sectional study. Postoperative AIS patients were prospectively recruited during routine follow-up visits, 2 to 10 years after spine fusion. Vitamin D levels were measured by serum 25-hydroxyvitamin D (ng/mL). Patients were categorized based on vitamin D level: deficient (<20 ng/mL), insufficient (20 to 29 ng/mL), or sufficient (≥30 ng/mL). The correlation between vitamin D levels and SRS-30 scores was analyzed using multivariable analysis and pair-wise comparisons using Tukey method.

RESULTS

Eighty-seven AIS patients (83% female) were enrolled who presented at median 3 years (interquartile range: 2 to 5 y; range: 2 to 10 y) after spine fusion. Age at time of surgery was mean 15 (SD±2) years. Major coronal curves were a mean of 57 (SD±8) degrees preoperatively and 18 (SD±7) degrees postoperatively. It was found that 30 (34%) of patients were vitamin D sufficient, 33 (38%) were insufficient, and 24 (28%) were deficient. Although there was no correlation between vitamin D level and Pain, Mental Health, or Satisfaction domains ( P >0.05), vitamin D-deficient patients were found to be younger ( P <0.001) and had lower SRS-30 function ( P =0.002), Self-image ( P <0.001), and total scores ( P =0.003).

CONCLUSIONS

AIS patients with vitamin D deficiency (<20 ng/mL) are more likely to be younger age at time of surgery, and report lower Function, Self-image, and Total SRS-30 scores postoperatively. Further work is needed to determine whether vitamin D supplementation alters curve progression and patient outcomes.

LEVEL OF EVIDENCE

Level II-prognostic study.

Biological effect of dysregulated LBX1 on adolescent idiopathic scoliosis through modulating muscle carbohydrate metabolism

BACKGROUND CONTEXT

Abnormal energy metabolism such as lower body weight and body mass index (BMI) and less fat mass is widely reported in patients with adolescent idiopathic scoliosis (AIS) and has been implicated in deformity development. However, the underlying mechanism is largely unclear. LBX1 is one of the promising AIS predisposing genes validated by multicenter studies.

PURPOSE

This study aimed to identify differentially expressed proteins (DEPs) relating to energy metabolism in AIS by using proteomic and metabolic analysis and to explore if the expression of these DEPs is associated with clinical parameters and modulated by LBX1.

STUDY DESIGN

This is a cross-sectional study using clinical data and biological samples followed by basic study using a cellular model.

PATIENT SAMPLE

Plasma samples were collected from Chinese girls with nonprogressive and progressive AIS (N=7 and 8, respectively) and age-matched healthy girls (N=50). Paraspinal muscle tissues were collected intraoperatively from concave and convex side of the apex of the major spinal curve in AIS (N=24) and either side from nonscoliosis patients (N=14).

OUTCOME MEASURES

Radiological Cobb angle and basic anthropometric data of recruited subjects were measured. The DEPs and metabolites were compared in plasma using proteomics and metabolomics technique. The relative expression of selected genes was measured in muscles.

METHODS

Plasma samples from AIS were collected at first clinical visit and were further divided into nonprogressive or progressive groups according to Cobb angle changes in 6-year follow-up. Age-matched healthy girls were recruited as control. High-performance liquid chromatography-mass spectrometry based proteomic analysis was carried out in three groups to identify DEPs and their annotated metabolic pathways. An independent cohort was used for validation by gas chromatography-mass spectrometry based metabolomic analysis. Paraspinal muscles were subjected to quantitative polymerase chain reaction (qPCR) followed by correlation analysis. Human skeletal muscle myoblast (HSMM) was used as the cellular model.

RESULTS

The likelihood of aberrant galactose metabolism and glycolysis was found to be associated with AIS curve progression as evidenced by the thirteen DEPs and seven related metabolites according to proteomic and metabolomic analysis. Some of the DEPs showed significantly altered expression in AIS concave and convex sides paraspinal muscles compared with those in nonscoliosis control. Four DEPs were found significantly and negatively correlated with LBX1 in AIS convex side paraspinal muscles. Overexpressing LBX1 in HSMM cells led to increased expression of three DEPs and decreased expression of three DEPs, respectively.

CONCLUSIONS

This is the first integrated proteomic and metabolomic analysis on AIS. Our findings show dysregulated galactose metabolism and glycolysis pathways in progressive group of AIS, suggesting the presence of abnormal energy metabolism at early stage of this disease, and their association with higher risk of progressing into more severe curvature. Evidence from ex vivo study with human muscle biopsies and in vitro study with human myoblast cells propose the possible effect of LBX1 on these two pathways in skeletal muscles. The present study provides new evidence of LBX1 function in AIS via modulating effect on the expression of energy metabolism related genes. This study might provide new insights into etiopathogenesis and development of novel treatment strategy targeting on abnormal body weight and BMI in patients with AIS. Additionally, the plasma proteomic and metabolomic studies suggested new candidates as biomarkers for establishing predictive model for AIS onset/progression.

Potential Muscle-Related Biomarkers in Predicting Curve Progression to the Surgical Threshold in Adolescent Idiopathic Scoliosis-A Pilot Proteomic Study Comparing Four Non-Progressive vs. Four Progressive Patients vs. A Control Cohort

Previous studies have reported abnormal muscle morphology and functions in patients with adolescent idiopathic scoliosis (AIS). To answer whether such abnormalities could be reflected in their circulation and their clinical implication for predicting curve progression to the surgical threshold, this preliminary study explored the presence of baseline muscle-related proteins and their association with curve progression. Plasma samples were collected at the first clinical visit for AIS, with patients divided into non-progressive or progressive groups (N = four and four) according to their Cobb angle in six-year follow-ups, with age- and sex-matched healthy subjects (N = 50). Then, the samples were subjected to isobaric tags for relative and absolute quantitation (iTRAQ) for global comparison of untargeted protein expression. Seventy-one differentially expressed proteins (DEPs) were found elevated in progressive AIS. Functional analysis showed that 18 of these are expressed in muscles and play an essential role in muscle activities. Among the muscle-related DEPs, α-actin had the highest fold change in progressive/non-progressive groups. This preliminary study firstly suggested higher circulating levels of muscle structural proteins in progressive AIS, indicating the likelihood of structural damage at the microscopic level and its association with progression to the surgical threshold. Further studies with larger sample sizes are warranted to validate these novel candidates for early diagnosis and predicting progression.

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.