Inclination of the small laminar slope angle leads to lumbar spinal stenosis due to hypertrophy of the ligamentum flavum

TCF7/SNAI2/miR-4306 feedback loop promotes hypertrophy of ligamentum flavum

Background

Hypertrophy of ligamentum flavum (HLF) is the mainly cause of lumbar spinal stenosis (LSS), but the precise mechanism of HLF formation has not been fully elucidated. Emerging evidence indicates that transcription factor 7 (TCF7) is the key downstream functional molecule of Wnt/β-catenin signaling, which participated in regulating multiple biological processes. However, the role and underlying mechanism of TCF7 in HLF is still unclear.

Methods

We used mRNAs sequencing analysis of human LF and subsequent confirmation with RT-qPCR, western blot and immunohistochemistry to identified the TCF7 in HLF tissues and cells. Then effect of TCF7 on HLF progression was investigated both in vitro and in vivo. Mechanically, chromatin immunoprecipitation, dual-luciferase reporter assays, and rescue experiments were used to validate the regulation of TCF7/SNAI2/miR-4306 feedback loop.

Results

Our results identified for first time that the TCF7 expression was obviously elevated in HLF tissues and cells compared with control, and also found that TCF7 expression had significant positive correlation with LF thickness and fibrosis score. Notably, TCF7 inhibition suppressed the hyper-proliferation and fibrosis phenotype of HLF cells in vitro and ameliorated progression of HLF in mice in vivo, whereas TCF7 overexpression promoted hyper-proliferation and fibrosis phenotype of HLF cells in vitro. Our data further revealed that TCF7 interacted with SNAI2 promoter to transactivated the SNAI2 expression, thereby promoting hyper-proliferation and fibrosis phenotype of HLF cells in vitro. Furthermore, miR-4036 negatively regulated by SNAI2 could negatively feedback regulate TCF7 expression by directly binding to TCF7 mRNA 3’-UTR, thus inhibiting the hyper-proliferation and fibrosis phenotype of HLF cells in vitro.

Conclusions

Our study demonstrated that TCF7 inhibition could suppress HLF formation by modulating TCF7/SNAI2/miR-4306 feedback loop, which might be considered as a novel potential therapeutic target for HLF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03677-0.

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.

The Role of Vertebral Morphometry in the Pathogenesis of Degenerative Lumbar Spinal Stenosis

The aim of the current study was to establish whether the vertebral morphometry (e.g., vertebral body width and spinal canal diameters) is associated with degenerative lumbar spinal stenosis (DLSS). A retrospective computerized tomography (CT) study from L1 to L5 for two sample populations was used. The first included 165 participants with symptomatic DLSS (sex ratio 80 M/85F), and the second had 180 individuals from the general population (sex ratio: 90 M/90F). Vertebral body length (VL) and width (VW) were significantly greater in the stenosis males and females compared to their counterparts in the control. The mean VL in the stenosis males was 31.3 mm at L1, 32.6 mm at L2, 34 mm at L3, 34.1 mm at L4, and 34.5 at L5 compared to 29.9 mm, 31.3 mm, 32.6 mm, 32.8 mm, and 32.9, respectively, in the control group (P ≤ 0.003). Additionally, the bony anterior-posterior (AP) canal diameters and cross-sectional area (CSA) were significantly smaller in the stenosis group compared to the control. The mean AP canal values in the stenosis males were 17.8 mm at L1, 16.6 mm at L2, 15.4 mm at L3, 15.6 mm at L4, and 16.1 at L5 compared to 18.7, 17.8, 16.9, 17.6, and 18.8, respectively, in the control group. Vertebral length (OR-1.273 to 1.473; P ≤ 0.002), AP canal diameter (OR-0.474 to 0.664; P ≤ 0.007), and laminar inclination (OR-0.901 to 0.856; P ≤ 0.025) were significantly associated with DLSS. Our study revealed that vertebral morphometry has a role in DLSS development.