Expression and function of FGF9 in the hypertrophied ligamentum flavum of lumbar spinal stenosis patients

GSK-3β and β-Catenin Signaling Pathway is Involved in Myofibroblast Transition of Ligamentum Flavum in Lumbar Spinal Stenosis Patients

STUDY DESIGN

Histologic analysis of the ligamentum flavum (LF) in the lumbar spine.

OBJECTIVE

The objective of this study is to investigate the levels of glycogen synthase kinase-3β (GSK-3β) and β-catenin in the LF tissue of patients with lumbar spinal stenosis (LSS).

SUMMARY OF BACKGROUND DATA

The hypertrophy of the LF is the primary cause of the progression of LSS. Recently, Wnt signaling has been proposed as one of the molecular processes contributing to LF hypertrophy. GSK-3β and β-catenin are recognized to play a crucial part in the control of this signaling pathway.

MATERIALS AND METHODS

From May 2020 to July 2022, LF from 51 LSS patients (LSS group) and 18 lumbar disc herniation patients (control group) were prospectively collected during surgery. Histologic analysis was investigated to confirm the progression of LF fibrosis. The levels of α-smooth muscle actin, phosphorylation of GSK-3β (p-GSK-3β; inactive form), and β-catenin were analyzed in LF with Western blot analysis to reveal the GSK-3β/β-catenin signaling pathway. Continuous variables are expressed as mean±SD and compared using the student t test. Categorical variables are compared using the χ 2 test or Fisher exact test, as appropriate. To determine the association between p-GSK-3β and LF thickness, the Pearson correlation coefficient was calculated based on the results of Western blot analysis.

RESULTS

The LSS group was older and had thicker LF than the controls. The LSS group showed increased collagen fiber and cellularity than the controls. The levels of α-smooth muscle actin, p-GSK-3β, and β-catenin in the LF of the LSS group were significantly higher than that of the control group. There was a strong positive correlation between p-GSK-3β (Ser9) level and LF thickness in LSS patients ( r =0.69, P =0.01).

CONCLUSION

This research proposes a molecular mechanism for the pathogenesis of LF hypertrophy in LSS. Specifically, GSK-3β/β-catenin signaling appears to be related to LF hypertrophy in LSS and a positive correlation exists between p-GSK-3β level and LF thickness.

LEVEL OF EVIDENCE

Level 3.

Anti-Tumor Effect and Neurotoxicity of Ethanol Adjuvant Therapy after Surgery of a Soft Tissue Sarcoma

Wide resection is the main treatment for sarcomas; however, when they are located near major nerves, their sacrifices might affect limb function. The efficacy of ethanol adjuvant therapy for sarcomas has not been established. In this study, the anti-tumor effect of ethanol, as well as its neurotoxicity, were assessed. In vitro anti-tumor effect of ethanol as evaluated using MTT, wound healing, and invasion assays on a synovial sarcoma cell line (HS-SY-II). In vivo, an assessment was conducted in nude mice (implanted with subcutaneous HS-SY-II) treated with different ethanol concentrations after surgery with a close margin. Sciatic nerve neurotoxicity was assessed with electrophysiological and histological examination. In vitro, ethanol concentrations at 30% and higher showed cytotoxic effects in MTT assay and markedly reduced migration and invasive ability of HS-SY-II. In vivo, both 30% and 99.5% ethanol concentrations, compared to 0% concentration, significantly reduced the local recurrence. However, in the group treated with 99.5% ethanol, nerve conduction tests showed prolonged latency and decreased amplitude, and morphological changes suggestive of nerve degeneration were observed in the sciatic nerve, while the 30% ethanol did not cause neurological damage. In conclusion, 30% is the optimal concentration for ethanol adjuvant therapy after close-margin surgery for sarcoma.

LncRNA XIST facilitates hypertrophy of ligamentum flavum by activating VEGFA-mediated autophagy through sponging miR-302b-3p

BACKGROUND

Increasing evidences have shown that long non-coding RNAs (lncRNAs) display crucial regulatory roles in the occurrence and development of numerous diseases. However, the function and underlying mechanisms of lncRNAs in hypertrophy of ligamentum flavum (HLF) have not been report.

METHODS

The integrated analysis of lncRNAs sequencing, bioinformatics analysis and real-time quantitative PCR were used to identify the key lncRNAs involved in HLF progression. Gain- and loss-function experiments were used to explore the functions of lncRNA X inactive specific transcript (XIST) in HLF. Mechanistically, bioinformatics binding site analysis, RNA pull-down, dual-luciferase reporter assay, and rescue experiments were utilized to investigate the mechanism by which XIST acts as a molecular sponge of miR-302b-3p to regulate VEGFA-mediated autophagy.

RESULTS

We identified that XIST was outstandingly upregulated in HLF tissues and cells. Moreover, the up-regulation of XIST strongly correlated with the thinness and fibrosis degree of LF in LSCS patients. Functionally, knockdown of XIST drastically inhibited proliferation, anti-apoptosis, fibrosis and autophagy of HLF cells in vitro and suppressed hypertrophy and fibrosis of LF tissues in vivo. Intestinally, we uncovered that overexpression of XIST significantly promoted proliferation, anti-apoptosis and fibrosis ability of HLF cells by activating autophagy. Mechanistic studies illustrated that XIST directly medullated the VEGFA-mediated autophagy through sponging miR-302b-3p, thereby enhancing the development and progression of HLF.

CONCLUSION

Our findings highlighted that the XIST/miR-302b-3p/VEGFA-mediated autophagy axis is involved in development and progression of HLF. At the same time, this study will complement the blank of lncRNA expression profiles in HLF, which laid the foundation for further exploration of the relationship between lncRNAs and HLF in the future.

Periostin increased by mechanical stress upregulates interleukin-6 expression in the ligamentum flavum

Ligamentum flavum (LF) hypertrophy is a major cause of lumbar spinal canal stenosis. Although mechanical stress is thought to be a major factor involved in LF hypertrophy, the exact mechanism by which it causes hypertrophy has not yet been fully elucidated. Here, changes in gene expression due to long-term mechanical stress were analyzed using RNA-seq in a rabbit LF hypertrophy model. In combination with previously reported analysis results, periostin was identified as a molecule whose expression fluctuates due to mechanical stress. The expression and function of periostin were further investigated using human LF tissues and primary LF cell cultures. Periostin was abundantly expressed in human hypertrophied LF tissues, and periostin gene expression was significantly correlated with LF thickness. In vitro, mechanical stress increased gene expressions of periostin, transforming growth factor-β1, α-smooth muscle actin, collagen type 1 alpha 1, and interleukin-6 (IL-6) in LF cells. Periostin blockade suppressed the mechanical stress-induced gene expression of IL-6 while periostin treatment increased IL-6 gene expression. Our results suggest that periostin is upregulated by mechanical stress and promotes inflammation by upregulating IL-6 expression, which leads to LF degeneration and hypertrophy. Periostin may be a pivotal molecule for LF hypertrophy and a promising therapeutic target for lumbar spinal stenosis.

Potential Involvement of Oxidative Stress in Ligamentum Flavum Hypertrophy

Oxidative stress (OS) results in many disorders, of which degenerative musculoskeletal conditions are no exception. However, the interaction between OS and ligamentum flavum (LF) hypertrophy in lumbar spinal canal stenosis is not clearly understood. The first research question was whether OS was involved in LF hypertrophy, and the second was whether the antioxidant N-acetylcysteine (NAC) was effective on LF hypertrophy. In total, 47 LF samples were collected from patients with lumbar spinal disorders. The cross-sectional area of LF was measured on axial magnetic resonance imaging. Immunohistochemistry of 8-OHdG and TNF-α were conducted on human LF samples. A positive association was found between 8-OHdG or TNF-α expression and cross-sectional area of LF. Flow cytometry analysis showed that H₂O₂, buthionine sulfoximine, and TNF-α treatment significantly increased intracellular reactive oxygen species in primary LF cells. NAC inhibited the induction of LF hypertrophy markers by OS or TNF in a real-time reverse transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay. Western blotting analysis indicated that p38, Erk, and p65 phosphorylation were involved in intracellular OS signaling in LF cells. In conclusion, our results indicated that OS could be a therapeutic target for LF hypertrophy. Although this study included no in vivo studies to examine the longitudinal efficacy of NAC on LF hypertrophy, NAC may have potential as a therapeutic agent against lumbar spinal canal stenosis.

Relationship between Severity of Lumbar Spinal Stenosis and Ligamentum Flavum Hypertrophy and Serum Inflammatory Factors

Objective

This study is aimed at investigating the correlation between lumbar spinal stenosis (LSS) severity, ligamentum flavum hypertrophy, and the upregulation of inflammatory markers.

Methods

From March 2019 and May 2022, eighty-five inpatients with LSS were enlisted as the study's research group, while sixty-five patients hospitalized for lumbar intervertebral disc herniation over the same time period served as the study's control group. Moreover, mild, moderate, and severe subgroups of patients were created within the research population based on their LSS severity. The ligamentum flavum thickness and the positive expression rates of TNF-α, TGF-β1, and IL-1α were compared between the study group and the control group. The levels of TNF-α, TGF-β1, and IL-1α that were found to be positively expressed were compared between the mild, moderate, and severe groups. Patients with LSS had their ligamentum flavum thickness and their positive expression rates of TNF-α, TGF-β1, and IL-1α analyzed using Spearman correlation analysis. We evaluated the diagnostic utility of the positive expression rates of IL-α1, TGF-β1, and TNF-α and ligamentum flavum thickness in distinguishing the severity of LSS using a receiver operating characteristic (ROC) curve.

Results

The rates of both lower limb pain (40.00%) and intermittent claudication (80.00%) in the LSS group were higher than those in the lumbar disc herniation group (15.38%, 12.31%), with statistical significance (P < 0.05). However, no substantial disparity was observed in left lower limb pain, right lower limb pain, low back pain, lower limb sensation, muscle strength, and reflex abnormalities between the two groups (P > 0.05). Positive expressions of TGF-β1, TNF-α, and IL-1α and thicker ligamentum flavum were more prevalent in the LSS group than in the lumbar intervertebral disc herniation group. All indexes were significantly (P < 0.05) higher in the moderate stenosis group than in the severe stenosis group. Additionally, the thickness of the ligamentum flavum and the positive expression rates of TNF-α, TGF-β1, and IL-1α were higher in the mild and moderate stenosis groups than in the severe stenosis group. The expression levels of TNF-α, TGF-β1, and IL-1α were favorably linked with ligamentum flavum thickness (P < 0.05). ROC curve analysis showed that the thickness of ligamentum flavum, the expression of IL-1α, the expression of TGF-β1, and the expression of TNF-α could effectively diagnose mild, moderate, and severe LSS (P < 0.05).

Conclusion

Ligamentum flavum hypertrophy and positive expression rates of IL-1α, TGF-β1, and TNF-α are closely linked to LSS, which can effectively identify mild, moderate, and severe LSS.

Unilateral Biportal Endoscopic Discectomy versus Microendoscopic Discectomy for the Treatment of Lumbar Spinal Stenosis: A Systematic Review and Meta-Analysis

Objective

In minimally invasive spinal surgery, the treatment of lumbar spinal stenosis with microendoscopic discectomy (MED) or unilateral biportal endoscopic discectomy (UBED) shows effective results, but which is more effective is controversial. Our study aimed to evaluate the efficacy and safety of UBED versus MED in the treatment of lumbar spinal stenosis by a systematic review and meta-analysis, so as to provide reference for the promotion of UBED in clinical practice.

Methods

The multiple databases like PubMed, EMBASE, Web of Science, Cochrane Library, Chinese National Knowledge Databases, Chinese BioMedical Database, and Wanfang Database were used to search for the relevant studies. Review Manager 5.4 was adopted to estimate the effects of the results among selected articles. Odds ratio (OR) and mean difference (MD) with 95% confidence intervals (CIs) were used to estimate the overall pooled effect. Subgroup analysis, forest plots, funnel plots and Egger's test for the articles included were also conducted.

Results

Three randomized clinical trials and seven cohort studies were finally retrieved, these studies included 685 and 829 patients in the UBED and MED groups, respectively. There were no differences in terms of operation time (MD = -0.92, P =0.72), estimated blood loss (MD = -26.31, P =0.08), complications (MD =0.81, P =0.38) and Oswestry Disability Index (ODI) score (P >0.05 in four subgroup) between the two groups. The visual analog scale (VAS) score of back pain in the UBED group was better than MED group only at 6 months (MD = -0.23, P =0.006) after operation, the VAS score of leg pain in the UBED group was better than that of MED group at 3 mouths (MD = -0.22, P =0.002) and 6 months (MD = -0.24, P =0.006) after operation, the UBED group had a less postoperative length of stay than the MED group (MD = -1.85, P <0.001). The bias analysis showed that there was no potential publication bias in the included literature.

Conclusion

This study showed that compared with MED, UBED has the advantages of short hospital stay and good short-term curative effect, but there is no significant difference in long-term efficacy and safety, they can be replaced by each other in clinical application.

Myofibroblasts are increased in the dorsal layer of the hypertrophic ligamentum flavum in lumbar spinal canal stenosis

BACKGROUND CONTEXT

Hypertrophy of the ligamentum flavum (LF) is a major contributor to the development of lumbar spinal canal stenosis (LSS). Although previous studies have identified some factors related to hypertrophy of the LF, the etiology remains unclear. It is well known that myofibroblasts have a key role in the pathology of fibrosis in other tissues, including the skin, liver, kidney, and lung. We hypothesized that myofibroblasts were also important players in the pathology of fibrosis in the LF.

PURPOSE

To elucidate the distribution and role of myofibroblasts in the hypertrophic LF.

STUDY DESIGN

A histological, immunohistochemical, and gene expression analysis of the LF in the human lumbar spine.

PATIENT SAMPLE

Hypertrophic LF tissue samples were collected from patients with LSS.

OUTCOME MEASURES

Histology, immunohistochemistry, microarray, reverse transcription-quantitative polymerase chain reaction, western blotting, and enzyme-linked immunosorbent assay.

METHODS

The degree of fibrosis in the dural and dorsal layers of the LF was evaluated by Masson's trichrome tissue staining. Collagen gene expression was evaluated by quantitative reverse transcription polymerase chain reaction. Immunostaining of αSMA was performed to evaluate localization of myofibroblasts in LF tissue. The association between gene expression of alpha-smooth muscle actin (αSMA) and that of several types of collagen was investigated. The signal activated on the dorsal side of LF was examined by gene set enrichment analysis using microarray data. Expression levels of αSMA and several types of collagen in LF fibroblasts were investigated under hypoxic conditions.

RESULTS

In the histological study using Masson's trichrome staining, the fibrosis score was significantly higher in the dorsal layer than in the dural layer. Gene expression levels for several types of collagen (COL1A1, COL1A2, COL3A1, COL5A1, COL6A1, and COL11A1) and heat shock protein 47 (a collagen-specific chaperone) were significantly higher in the dorsal layer. Furthermore, immunohistochemistry revealed a significantly greater number of αSMA-stained cells in the dorsal layer. There was a strong correlation of αSMA mRNA expression with COL1A-1 in LF fibroblasts. Gene set enrichment analysis showed that the set of fibrosis-related gene signals, including those for epithelial-mesenchymal transition, hypoxia, and inflammation, were significantly upregulated in the dorsal layer compared with the dural layer. Under hypoxic stimulation, expression of αSMA and several types of collagen was increased in LF fibroblasts.

CONCLUSIONS

This study is the first to reveal that myofibroblast expression levels are higher in the dorsal layer of the LF than in the dural layer. We confirmed that hypertrophy of the LF in LSS is associated with increased expression of myofibroblasts in the dorsal layer. Hypoxia could be a cause of expression of myofibroblasts leading to fibrosis and finally to hypertrophy of the LF.

CLINICAL SIGNIFICANCE

The results of this study partially elucidate the molecular mechanisms of LF hypertrophy and suggest that myofibroblasts may be involved in age-related degeneration of the LF.