Clinical Guideline for Treatment of Symptomatic Thoracic Spinal Stenosis

Diagnosis and Management of Thoracic Myelopathy

Thoracic myelopathy can be a challenging condition to diagnose and treat. Successful outcomes depend on early recondition of the pathology and appropriate surgical referral in cases of progressive neurologic deterioration. The thoracic cord is tethered in kyphosis by the dentate ligaments and contains a tenuous blood supply. These conditions make the thoracic cord particularly susceptible to external compression and ischemic damage. Careful preoperative planning with specific attention to the location and source of thoracic stenosis is critical to successful decompression and complication avoidance. The purpose of this discussion is to outline the common sources of thoracic myelopathy and current recommendations regarding diagnosis and management. The review concludes with an overview of the most up-to-date literature regarding clinical outcomes.

Nondysraphic Intradural Spinal Lipoma: A Case Report and Review of Pathogenesis

Intradural spinal lipomas are rare benign lesions typically located in the lumbosacral region and associated with spinal dysraphism in children. When unassociated with spinal dysraphism, they are most often diagnosed in young children or adolescents following the emergence of neurological symptoms. In their most rare form, intradural spinal lipomas may be found in adults without spinal dysraphism. Here, we present a case of a 42-year-old female with an intradural spinal lipoma without dysraphism at the T10-T11 level, demonstrating the diagnostic challenge of atypical lipomas and the importance of timely assessment and management. We also reviewed the embryopathogenesis of the different types of intradural spinal lipomas and the importance of surgical interventional planning and approach.

Improvement of Postoperative Quality of Life in Patients Over 80 Years Old With Thoracic Spinal Stenosis

STUDY DESIGN

A retrospective comparative study was conducted to analyze the outcome of surgical and conservative treatment for patients over 80 years old with thoracic spinal stenosis (TSS).

OBJECTIVE

To evaluate the safety and efficiency of posterior spinal cord decompression surgery for over 80-year-old patients with TSS.

SUMMARY OF BACKGROUND DATA

Concerned about the risk of surgery, over 80-year-old patients with TSS are usually treated conservatively, which often leads to a decline in quality of life. So far as we know, no study demonstrates the risk and benefit of spine surgery for these patients.

METHODS

Over 80 years of age who underwent dorsal decompression surgery or conservative treatment due to TSS between January 2010 and November 2020 were analyzed. Sixty-four patients who completed follow-up PROM (patient-reported outcome measure) data were collected, including the mJOA (modified Japanese Orthopedic Association score) scoring system, VAS (visual analogue scale), questionnaire-based assessment of the ODI (Oswestry disability index), BI (Barthel index), and SF-36v2 (Short Form-36v2) Health Survey. The clinical characteristics, preoperative and postoperative imaging findings, operative records, complications, and individual outcomes were analyzed.

RESULTS

Of the 64 patients, 38 underwent posterior decompression, pedicle screw fixation, and posterolateral fusion; another 26 chose conservative treatment. The baseline characteristics of the TSS patients in 2 groups show no significant differences. The clinical symptoms and imaging outcomes showed a significant improvement in the surgical group compared with the nonsurgical group, according to mJOA, VAS, ODI, BI, and SF-36v2. Cerebrospinal fluid leakage occurred in 6 patients, and transient neurological impairment occurred in 2 patients.

CONCLUSIONS

Posterior decompression surgery for over 80-year-old patients with TSS is a safe and effective treatment, it has a good clinical outcome as well as an acceptable complication rate. However, there were no obvious improvements in quality of life or pain with conservative treatment.

Prevalence, diagnosis, and impact on clinical outcomes of dural ossification in the thoracic ossification of the ligamentum flavum: a systematic review

STUDY DESIGN

Systematic review.

BACKGROUND CONTEXT

Thoracic ossification of the ligamentum flavum (TOLF) has become the principal cause of thoracic spinal stenosis. Dural ossification (DO) was a common clinical feature accompanying with TOLF. However, on account of the rarity, we know little about the DO in TOLF so far.

PURPOSE

This study was conducted to elucidate the prevalence, diagnostic measures, and impact on the clinical outcomes of DO in TOLF by integrating the existing evidence.

METHODS

PubMed, Embase, and Cochrane Database were comprehensively searched for studies relevant to the prevalence, diagnostic measures, or impact on the clinical outcomes of DO in TOLF. All retrieved studies meeting the inclusion and criterion were included into this systematic review.

RESULTS

The prevalence of DO in TOLF treated surgically was 27% (281/1046), ranging from 11 to 67%. Eight diagnostic measures have been put forward to predict the DO in TOLF using the CT or MRI modalities, including "tram track sign", "comma sign", "bridge sign", "banner cloud sign", "T2 ring sign", TOLF-DO grading system, CSAOR grading system, and CCAR grading system. DO did not affect the neurological recovery of TOLF patients treated with the laminectomy. The rate of dural tear or CSF leakage in TOLF patients with DO was approximately 83% (149/180).

CONCLUSION

The prevalence of DO in TOLF treated surgically was 27%. Eight diagnostic measures have been put forward to predict the DO in TOLF. DO did not affect the neurological recovery of TOLF treated with laminectomy but was associated with high risk of complications.

Clinical progression of ossification of the ligamentum flavum in thoracic spine: a 10- to 11-year follow-up study

BACKGROUND

Thoracic ossification of ligamentum flavum (TOLF) can be asymptomatic and progress insidiously. But, long-term follow-up results of clinical progression of TOLF are still unknown.

METHODS

The clinical progression of 81 patients with TOLF at our center, followed for 10 to 11 (mean, 10.3) years from May 2010 to November 2021, were analyzed. Among them, 51 patients with thoracic myelopathy were caused by single- or multi-segment TOLF, and received partial TOLF resection (30 patients) or total TOLF resection (21 patients). The remaining 30 patients showed TOLF on imaging examinations, but TOLF was not the responsible compressing factor causing myelopathy and with no TOLF resection. The mJOA score (total 11 scores) and spinal operation were used to evaluate the clinical progression at follow-up.

RESULTS

During the 10- to 11-year follow-up of 81 TOLF patients, 71 (87.7%) had no deterioration of neurological function, and 10 (12.3%) patients had deterioration of neurological function and had another spinal operation, including only 4 (4.9%) suffered thoracic myelopathy caused by the progression of TOLF; 6 (7.4%) for other spinal diseases: 2 (2.5%) had fall damage and acute spinal cord injury at the TOLF level; 2 (2.5%) had thoracic myelopathy caused by ossification of posterior longitudinal ligament (OPLL); 2 (2.5%) had cervical spondylosis and received cervical operation.

CONCLUSIONS

Most TOLF (87.7%) patients had no clinical progression and received no reoperations for TOLF in the ten-year dimension (mean, 10.3 years). Narrow spinal canal for TOLF increases the risk of traumatic paraplegia.

Significance of body mass index on thoracic ossification of the ligamentum flavum in Chinese population

PURPOSE

To investigate the risk factors for thoracic ossification of the ligamentum flavum (TOLF), especially the relationship between BMI and TOLF.

METHODS

A total of 856 individuals consisting of 326 controls without ossification of spinal ligaments and 530 TOLF inpatients who underwent thoracic spine decompression surgery at our hospital between January 2013 and September 2020 were included. All subjects were classified into 4 grades: Grade 0) control; Grade 1) single-segment TOLF; Grade 2) multi-segment TOLF; and Grade 3) TOLF combined thoracic ossification of the posterior longitudinal ligament (T-OPLL). Logistic regression analysis was performed to identify the risk factors for TOLF. The TOLF index was calculated to assess the severity of TOLF, and its relationship with BMI was investigated by correlation analysis.

RESULTS

Overall, TOLF patients are most numerous in the 50-59 age group. Age and gender were considered as independent risk factors for Grades 1 and 2. BMI was identified as an independent risk factor for TOLF. Furthermore, BMI was significantly higher in Grade 1 (26.1 VS 24.5 kg/m², P = 0.0001), Grade 2 (28.2 VS 24.5 kg/m², P < 0.0001), and Grade 3 (29.1 VS 24.5 kg/m², P < 0.0001) than Grade 0. Notably, in TOLF patients without combined T-OPLL, BMI was positively correlated with TOLF index, while BMI was negatively correlated with age in younger individuals.

CONCLUSION

BMI is a crucial risk factor for TOLF. It highlights the necessity of close follow-up of asymptomatic TOLF patients with high BMI to detect and treat their TOLF progression promptly.

High Systemic Immune-Inflammation Index and Body Mass Index Are Independent Risk Factors of the Thoracic Ossification of the Ligamentum Flavum

Background

Inflammation has been considered to play an important role in the pathogenesis of the thoracic ossification of the ligamentum flavum (OLF). However, the inflammation-related risk factors of thoracic OLF have not been fully investigated to date.

Methods

A total of 95 patients (48 in the OLF group and 47 in the control group) were included in this retrospective study to explore the independent risk factors of thoracic OLF. The following demographic and clinical variables were compared between the two groups: gender, age, body mass index (BMI), coexistence of hypertension or diabetes, and inflammation-related variables. Multivariate logistic regression analysis was utilized to determine the independent risk factors.

Results

High systemic immune-inflammation index (SII) (≥621) (odds ratio [OR] = 12.16, 95% confidence interval [CI] = 2.95-50.17, p < 0.01) and BMI (≥25 kg/m2) (OR = 9.17, 95%CI = 3.22-26.08, p < 0.01) were independent risk factors of thoracic OLF. SII (R = 0.38, p < 0.01) and BMI (R = 0.46, p < 0.01) were positively associated with OLF score.

Conclusion

High SII and BMI were the independent risk factors of thoracic OLF. Multicenter prospective studies with a large population should be conducted in the future to verify our findings.

Association analysis and functional study of COL6A1 single nucleotide polymorphisms in thoracic ossification of the ligamentum flavum in the Chinese Han population

PURPOSE

Genetic factors play a crucial role in thoracic ossification of the ligamentum flavum (TOLF). This study aimed to better understand the association between single nucleotide polymorphisms (SNP) in functional regions of the collagen VI, alpha 1 gene (COL6A1) and TOLF, and to confirm COL6A1 as a TOLF susceptibility gene.

METHODS

Ten tag SNPs in COL6A1 were genotyped using the SNaPshot assay, and allele and genotype frequencies were compared between TOLF patients and control individuals. The function of SNPs associated with disease was studied. For COL6A1 promoter SNPs, the transcriptional activity of each haplotype was determined by luciferase reporter assays. For COL6A1 exonic SNPs, the effect of nucleotide substitutions on COL6A1 expression was determined by western blotting. COL6A1 mRNA expression in ligamentum flavum tissues from TOLF patients with different genotypes was examined using reverse transcription real-time PCR.

RESULTS

Four SNPs were associated or possibly associated with TOLF, with higher pathogenic allele and genotype frequencies seen in TOLF patients compared with controls. The rs17551710/rs7671-GG/GG genotype appeared to be related to disease severity. Nucleotide substitutions at rs17551710 and rs7671 increased COL6A1 transcriptional activity and nucleotide substitutions at rs1053312 and rs13051496 increased COL6A1 protein expression. COL6A1 mRNA expression was significantly up-regulated in individuals with rs17551710/rs7671-GG/GG and rs1053312/rs13051496-AA+AG/CC genotypes compared with other genotypes.

CONCLUSION

SNPs in the COL6A1 promoter and exonic regions are associated with TOLF in the Chinese Han population, and lead to up-regulated COL6A1 expression. We confirmed COL6A1 as a TOLF susceptibility gene that may be involved in TOLF pathology.

Thoracic ligamentum flavum ossification: a rare cause of spinal cord injury without tomographic evidence of trauma in a Caucasian patient. Case report and literature review

INTRODUCTION

Acute spinal cord injury without tomographic evidence of vertebral fracture or dislocation in patients post trauma can represent a diagnostic challenge for the treating physician. The ossification of thoracic ligamentum flavum has been widely published as a cause of thoracic myelopathy, however its association with acute traumatic spinal cord injury is limited to isolated cases.

CASE PRESENTATION

we report a Caucasian 37-year-old man who suffered a high-energy thoracolumbar spine trauma in a motorcycle accident with acute paraplegia. He presented ossification of the ligamentum flavum between the thoracic vertebrae T10 and T11 with a decrease in the diameter of the vertebral canal as the only pathological finding. We treated the patient with early surgical release before 72 h of trauma. We performed a posterior approach with hemilaminectomy and T10-T11 flavectomy. Arthrodesis was done with T10-T11 pedicle screws. Postoperative neurological status improved from ASIA Impairment Scale (AIS) A to C with severe functional dependence.

DISCUSSION

Ossification of the ligamentum flavum should be considered in the differential diagnosis in patients presenting with acute traumatic spinal cord injury without tomographic evidence of trauma. A proper diagnosis in time is the key to decision making and treatment of spinal cord injury. Especially in adult patients, we must consider nontraumatic associated factors that could be involved in the spinal cord injury mechanism, such as ossification of the ligamentum flavum.

Relationship between Scheuermann disease and symptomatic thoracic spinal stenosis: A retrospective study

OBJECTIVE

This study aimed to investigate the possible relationship between Scheuermann disease (SD) and the pathophysiological factors of thoracic spinal stenosis (TSS), including ossification of the ligamentum flavum (OLF), ossification of the posterior longitudinal ligament (OPLL), and thoracic disc herniation (TDH) in patients with symptomatic TSS.

METHODS

Demographic and radiological data from 66 consecutive patients diagnosed with symptomatic TSS from 2013 to 2018 were retrospectively collected and divided into 3 groups depending on the underlying pathomechanism of TSS: TDH group (18 patients; 6 women; mean age ± standard deviation [Sd] = 59.89 ± 11.34), OPLL group (12 patients; 8 women; mean age ± Sd = 56.08 ± 14.74), and OLF group (36 patients; 20 women; mean age ± Sd = 58.69 ± 9.77). A total of 41 age-matched healthy individuals (19 women; mean age ± Sd = 54.88 ± 13.63) were designated as the control group. In each group, both typical and atypical SD criteria were radiologically examined. The demographic data and presence of SD between the control group and 3 subgroups of TSS pathomechanisms were evaluated.

RESULTS

SD characteristics were identified in 83.33% (15/18) of patients in the TDH group, 44.44% (16/36) in the OLF group, 25% (3/12) in the OPLL group, and 17.07% (7/41) of the control individuals. When analyzed by the chi-squared test and logistic regression analysis, the presence of SD was significantly associated with TDH (P < 0.01) and OLF (P < 0.05) but not OPLL (P > 0.05). Patients with TDH and OLF showed peak involvement of T10/11, and patients with OPLL did not. Furthermore, we determined that age, sex, body-mass index, and smoking status were not the risk factors for TDH, OPLL, and OLF (P > 0.05). SD was found to be a risk factor for TDH (P < 0.01) and OLF (P < 0.05) but not for OPLL (P > 0.05).

CONCLUSION

Evidence from this study indicated that SD might be a risk factor for OLF and TDH but not for OPLL.

Full endoscopic surgery for thoracic pathology: an assessment of supportive evidence

In the last five years, surgeons have applied endoscopic transforaminal surgical techniques mastered in the lumbar spine to the treatment of thoracic pathology.

The aim of this systematic review was to collate the available literature to determine the place and efficacy of full endoscopic approaches used in the treatment of thoracic disc prolapse and stenosis.

An electronic literature search of PubMed, Embase, the Cochrane database and Google Scholar was performed as suggested by the Preferred Reporting Items for Systematic Review and Meta-analysis statements. Included were any full-text articles referring to full endoscopic thoracic surgical procedures in any language.

We identified 17 patient series, one cohort study and 13 case reports with single or of up to three patients.

Although the majority included disc pathology, 11 papers related cord compression in a proportion of cases to ossification of the ligamentum flavum or posterior longitudinal ligament. Two studies described the treatment of discitis and one reported the use of endoscopy for tumour resection.

Where reported, excellent or good outcomes were achieved for full endoscopic procedures in a mean of 81% of patients (range 46–100%) with a complication rate of 8% (range 0–15%), comparing favourably with rates reported after open discectomy (anterior, posterolateral and thoracoscopic) or by endoscopic tubular assisted approaches. Twenty-one of the 31 author groups reported use of local anaesthesia plus sedation rather than general anaesthesia, providing ‘self-neuromonitoring’ by allowing patients to respond to cord and/or nerve stimuli.

Cite this article: EFORT Open Rev 2021;6:50-60. DOI: 10.1302/2058-5241.6.200080

The projection of the thoracic nerve roots and their connection with intervertebral discs: a cadaver and radiological study

BACKGROUND

The anatomical features of the thoracic nerve roots in connection with intervertebral discs may prevent surgery-related complications and improve patients' neurological functional status during thoracic spine surgery. There is limited literature evidence regarding this concept using cadavers.

PURPOSE

To elucidate the qualitative anatomical features of the thoracic nerve roots in connection with intervertebral discs.

MATERIAL AND METHODS

Fifteen formalin-preserved spine specimens were used in this study. Small pieces of stainless-steel wires were placed along the root sleeves from their points of origin, after exposing the dural sac and bilateral nerve roots. The standard anteroposterior and lateral radiographs were taken after the placement of the wires. Measurements were done on radiographs using the picture archiving communication system.

RESULTS

Take-off angles of the nerve roots at the coronal plane gradually increased from the level of T2 (36.1°±2.72°) to T9 (84.1°±1.84°) and from T9, it decreased to T12 (46.3° ± 2.67°). Similar variation tendency was discovered in take-off angles of the nerve roots at the sagittal plane. No consistent tendency was found both in the distance from the origin of the root sleeve to its superior and inferior vertebral endplate. Distance from the origin of the root sleeve to the posterior midline (DM) exponentially decreased from T1 (8.2 ± 0.87 mm) to T4 (6.0 ± 0.93 mm). It slowly increased from T5 (5.5 ± 0.68 mm) to T12 (10.9 ± 1.79 mm), with T5 having the smallest DM. Distance between the origins of neighboring nerve roots showed an obvious increase from the T1-T2 interval (23.1 ± 2.22 mm) to T7-T8 interval (30.9 ± 2.68 mm). However, it progressively decreased at the T10-T11 interval (26.0 ± 2.40 mm).

CONCLUSION

The dimensions of the thoracic nerve roots vary greatly from T1 to T12 intervertebral discs. Sound knowledge of these anatomical features of the thoracic nerve is mandatory for the thoracic spine surgery, especially in the posterolateral approach and transforaminal endoscopic surgery.

Role of lordotic rod contouring in thoracic myelopathy: a technical note

Introduction

Decompressive surgery for thoracic myelopathy due to anterior pathology can be challenging. Direct decompression through anterior approaches is associated with approach-related complications, whereas anterior decompression through posterior approaches is technically demanding and may result in neurological deterioration. We present a simple and effective surgical technique of indirect decompression through lordotic rod contouring to reduce such complications.

Case presentation

Patients who presented to our center between March 2016 and March 2017 with symptoms and signs suggestive of thoracic myelopathy predominantly due to anterior pathologies such as ossification of the thoracic posterior longitudinal ligament, posterior bony spur, and thoracic disc herniation were evaluated in our study. The indications for surgical treatment were progressive neurological impairment and severe myelopathy (grade III or more on Nurick grade). Only those patients classified as grade III and above on American Society of Anaesthesiologists (ASA) physical status scale were included in the study. All the cases were operated by a single surgeon by a posterior-only approach. We have used this technique in four patients with thoracic myelopathy due to combined or predominant anterior pathology. Postoperative imaging confirmed adequate decompression of the spinal cord. All the cases improved substantially in terms of clinical outcome.

Discussion

This surgical technique could be a useful alternative to direct anterior decompression in patients who present with symptoms of progressive severe myelopathy due to anterior compression and could be the standard of care in those at high risk for major surgery.

The efficacy and safety of tranexamic acid in reducing perioperative blood loss in patients with multilevel thoracic spinal stenosis: A retrospective observational study

STUDY DESIGN

A retrospective study.

OBJECTIVE

To investigate the effectiveness and safety of intravenous tranexamic acid for reducing perioperative blood loss in patients with multilevel thoracic spinal stenosis (TSS).

METHODS

This is a retrospective observational study of 42 patients with multilevel TSS admitted from December 2016 to October 2017 to the spine department of Honghui Hospital who underwent posterolateral bone graft fusion with posterior laminectomy and decompression fixation. The patients were divided into 2 groups. All the surgeries were completed by the same surgeon. Group A received an intravenous infusion of 15 mg/kg 15 min prior to surgery. Continuous infuse on of tranexamic acid (TXA) at a dose of 1 mg/kg/h was provided throughout the operation until the skin was closed. Group B received no TXA as a blank control group. Group A comprised 10 males and 10 females with an average age of 53.41 ± 7.93 years; group B comprised 11 males and 11 females with an average age of 55.10 ± 8.43 years. The need for blood transfusion, volume of blood transfusion, blood coagulation function, extubation time, postoperative hospital stay and incidence of postoperative deep venous thrombosis (DVT) were recorded during and after the operation for the 2 groups.

RESULTS

There was no significant difference between the 2 groups in general characteristics, such as age, sex and body mass index (BMI) (P > .05). There was no significant difference between the 2 groups in the levels are instrumented and the laminectomy levels in each group. The average postoperative blood loss, need for blood transfusion, time to postoperative extubation and length of postoperative hospital stay in group A were lower than those in group B, and there was a significant difference between the 2 groups (P < .05). The preoperative and postoperative coagulation, and postoperative DVT did not occur 48 h after operation.

CONCLUSION

In the treatment of multilevel thoracic spinal canal stenosis using trabeculectomy with posterior laminectomy and posterolateral bone graft fusion, TXA can reduce the amount of blood transfused and the need for blood transfusion and can shorten the extubation time and the length of postoperative hospital stay without increasing the incidence of postoperative coagulation dysfunction or postoperative DVT.

LEVEL OF EVIDENCE

4.

Thoracic Endoscopic-Assisted Mini-Open Surgery for Thoracic and Thoracolumbar Spinal Cord Compression

Intervertebral disc herniation is a common cause of spinal cord compression, especially for the thoracic and thoracolumbar spinal cord, which has limited buffer space in the spinal canal. Spinal cord compression usually causes decreased sensation and paralysis of limbs below the level of compression, urinary and fecal incontinence, and/or urinary retention, which brings great suffering to the patients and usually requires surgical intervention. Thoracotomy or abdominothoracic surgery is usually performed for the thoracolumbar cord compression caused by hard intervertebral disc herniation. However, there is high risk of trauma and complications with this surgery. To reduce the surgical trauma and obtain good visibility, we designed athoracic endoscopic-assisted mini-open surgery for thoracic and thoracolumbar disc herniation, and performed this procedure on 10 patients who suffered from hard thoracic or thoracolumbar spinal cord compression. During the procedure, the thoracic endoscopy provided clear vision of the surgical field with a good light source. The compression could be fully exposed and completely removed, and no nerve root injury or spinal cord damage occurred. All patients achieved obvious recovery of neurological function after this procedure. This technique possesses the merits of minimal trauma, increased safety, and good clinical results. The aim of this study is to introduce this thoracic endoscopic-assisted mini-open surgery technique, and we believe that this technique will be a good choice for the thoracic and thoracolumbar cord compression caused by hard intervertebral disc herniation.

Two novel BMP-2 variants identified in patients with thoracic ossification of the ligamentum flavum

Thoracic ossification of the ligamentum flavum (TOLF)is a common cause of thoracic spinal canal stenosis and has been reported almost exclusively in East Asian countries. In this study, we established a relationship between bone morphogenic protein 2 (BMP-2) and TOLF. We divided patients into two groups according to severity of ossification and identified susceptible loci through exome sequencing. We identified 39 novel likely pathogenic variants in 29 genes in the transforming growth factor-beta (TGF-β) superfamily or TGF-β/BMPs signaling pathway, including two missense variants in BMP-2 (NM_001200.3) exon region, c.460C>G:p.(R154G) and c.584G>T:p.(R195M). Further Sanger sequencing and genotyping suggested the variants were only found in patients with long regional OLF. Bioinformatic assays predicted the two BMP-2 variants to cause significant alterations to gene and protein expression. Functional assays showed upregulation of BMP-2 expression, increased osteogenic marker expression, and enhanced osteogenic differentiation. Collectively, these results suggest a genetic contribution to the pathogenesis of TOLF, particularly in patients with long segment disease, and that nucleotide substitutions associated with increased BMP-2 expression may be involved in TOLF pathogenesis.

MiR-199b-5p inhibits osteogenic differentiation in ligamentum flavum cells by targeting JAG1 and modulating the Notch signalling pathway

Ossification of the ligamentum flavum (OLF) is a pathology almost only reported in East Asian countries. The leading cause of OLF is thoracic spinal canal stenosis and myelopathy. In this study, the role of miR-199b-5p and jagged 1 (JAG1) in primary ligamentum flavum cell osteogenesis was examined. MiR-199b-5p was found to be down-regulated during osteogenic differentiation in ligamentum flavum cells, while miR-199b-5p overexpression inhibited osteogenic differentiation. In addition, JAG1 was found to be up-regulated during osteogenic differentiation in ligamentum flavum cells, while JAG1 knockdown via RNA interference caused an inhibition of Notch signalling and osteogenic differentiation. Moreover, target prediction analysis and dual luciferase reporter assays supported the notion that JAG1 was a direct target of miR-199b-5p, with miR-199b-5p found to down-regulate both JAG1 and Notch. Further, JAG1 knockdown was demonstrated to block the effect of miR-199b-5p inhibition. These findings imply that miR-199b-5p performs an inhibitory role in osteogenic differentiation in ligamentum flavum cells by potentially targeting JAG1 and influencing the Notch signalling pathway.

MiR-132-3p Regulates the Osteogenic Differentiation of Thoracic Ligamentum Flavum Cells by Inhibiting Multiple Osteogenesis-Related Genes

Ossification of the ligamentum flavum (OLF) is a disorder of heterotopic ossification of spinal ligaments and is the main cause of thoracic spinal canal stenosis. Previous studies suggested that miR-132-3p negatively regulates osteoblast differentiation. However, whether miR-132-3p is involved in the process of OLF has not been investigated. In this study, we investigated the effect of miR-132-3p and its target genes forkhead box O1 (FOXO1), growth differentiation factor 5 (GDF5) and SRY-box 6 (SOX6) on the osteogenic differentiation of ligamentum flavum (LF) cells. We demonstrated that miR-132-3p was down-regulated during the osteogenic differentiation of LF cells and negatively regulated the osteoblast differentiation. Further, miR-132-3p targeted FOXO1, GDF5 and SOX6 and down-regulated the protein expression of these genes. Meanwhile, FOXO1, GDF5 and SOX6 were up-regulated after osteogenic differentiation and the down-regulation of endogenous FOXO1, GDF5 or SOX6 suppressed the osteogenic differentiation of LF cells. In addition, we also found FOXO1, GDF5 and SOX6 expression in the ossification front of OLF samples. Overall, these results suggest that miR-132-3p inhibits the osteogenic differentiation of LF cells by targeting FOXO1, GDF5 and SOX6.

Notch signaling pathways in human thoracic ossification of the ligamentum flavum

This study investigated the pathological process of Notch signaling in the osteogenesis of ligamentum flavum tissues and cells, and the associated regulatory mechanisms. Notch receptors, ligands, and target genes were identified by quantitative polymerase chain reaction (qPCR) in ligamentum flavum cells and immunohistochemistry in ligamentum flavum sections from ossification of the ligamentum flavum (OLF) patients and controls. The temporospatial expression patterns of JAG1/Notch2/HES1 in human ligamentum flavum cells during osteogenic differentiation were determined by qPCR. Lentiviral vectors for Notch2 overexpression and knockdown were constructed and transfected into ligamentum flavum cells before osteogenic differentiation to examine the function of Notch signaling pathways in the osteogenic differentiation of ligamentum flavum cells. Alkaline phosphatase, Runx2, Osterix, osteocalcin, and osteopontin mRNA levels, alkaline phosphatase activity, and Alizarin Red staining were used as indicators of osteogenic differentiation. JAG1/Notch2/HES1 mRNA levels were up-regulated in ligamentum flavum cells from OLF patients, which increased during osteogenic differentiation. Immunohistochemical analysis suggested positive Notch2 expression at the ossification front. Down-regulation of Notch2 expression decelerated osteogenic differentiation of ligamentum flavum cells, and Notch2 overexpression promoted osteogenic differentiation of ligamentum flavum cells. Expression of Runx2 and Osterix increased in a manner similar to that of Notch2 during osteogenic differentiation of ligamentum flavum cells, and Notch2 knockdown and overexpression influenced their expression levels. Notch signaling plays an important role in OLF, and Notch may affect the osteogenic differentiation of ligamentum flavum cells via interactions with Runx2 and Osterix.© 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1481-1491, 2016.