Insights into IVDD pathogenesis in 2024
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Role of macrophage in intervertebral disc degeneration
Intervertebral disc degeneration is a degenerative disease where inflammation and immune responses play significant roles. Macrophages, as key immune cells, critically regulate inflammation through polarization into different phenotypes. In recent years, the role of macrophages in inflammation-related degenerative diseases, such as intervertebral disc degeneration, has been increasingly recognized. Macrophages construct the inflammatory microenvironment of the intervertebral disc and are involved in regulating intervertebral disc cell activities, extracellular matrix metabolism, intervertebral disc vascularization, and innervation, profoundly influencing the progression of disc degeneration. To gain a deeper understanding of the inflammatory microenvironment of intervertebral disc degeneration, this review will summarize the role of macrophages in the pathological process of intervertebral disc degeneration, analyze the regulatory mechanisms involving macrophages, and review therapeutic strategies targeting macrophage modulation for the treatment of intervertebral disc degeneration. These insights will be valuable for the treatment and research directions of intervertebral disc degeneration.
KMT2A regulates the autophagy-GATA4 axis through METTL3-mediated m6A modification of ATG4a to promote NPCs senescence and IVDD progression
Intervertebral disc degeneration (IVDD), a disease associated with ageing, is characterised by a notable increase in senescent nucleus pulposus cells (NPCs) as IVDD progresses. However, the specific mechanisms that regulate the senescence of NPCs remain unknown. In this study, we observed impaired autophagy in IVDD-NPCs, which contributed to the upregulation of NPCs senescence and the senescence-associated secretory phenotype (SASP). The dysregulated SASP disrupted NPCs viability and initiated extracellular matrix degradation. Conversely, the restoration of autophagy reversed the senescence phenotype by inhibiting GATA binding protein 4 (GATA4). Moreover, we made the novel observation that a cross-talk between histone H3 lysine 4 trimethylation (H3K4me3) modification and N6-methyladenosine(m6A)-methylated modification regulates autophagy in IVDD-NPCs. Mechanistically, lysine methyltransferase 2A (KMT2A) promoted the expression of methyltransferase-like 3 (METTL3) through H3K4me3 modification, whereas METTL3-mediated m6A modification reduced the expression of autophagy-associated 4a (ATG4a) by attenuating its RNA stability, leading to autophagy damage in NPCs. Silencing KMT2A and METTL3 enhanced autophagic flux and suppressed SASP expression in IVDD-NPCs. Therefore, targeting the H3K4me3-regulated METTL3/ATG4a/GATA4 axis may represent a promising new therapeutic strategy for IVDD.
Matrix stiffness regulates nucleus pulposus cell glycolysis by MRTF-A-dependent mechanotransduction
Increased matrix stiffness of nucleus pulposus (NP) tissue is a main feature of intervertebral disc degeneration (IVDD) and affects various functions of nucleus pulposus cells (NPCs). Glycolysis is the main energy source for NPC survival, but the effects and underlying mechanisms of increased extracellular matrix (ECM) stiffness on NPC glycolysis remain unknown. In this study, hydrogels with different stiffness were established to mimic the mechanical environment of NPCs. Notably, increased matrix stiffness in degenerated NP tissues from IVDD patients was accompanied with impaired glycolysis, and NPCs cultured on rigid substrates exhibited a reduction in glycolysis. Meanwhile, RNA sequencing analysis showed altered cytoskeleton-related gene expression in NPCs on rigid substrates. Myocardin-related transcription factor A (MRTF-A) is a transcriptional coactivator in mechanotransduction mainly responding to cytoskeleton remodeling, which was activated and translocated to the nucleus under rigid substrate and was upregulated during IVDD progression. Furthermore, gas chromatography-mass spectrometry (GC-MS) analysis revealed that MRTF-A overexpression reduced NPC glycolytic metabolite abundance and identified a correlation with AMPK pathway. Mechanistically, rigid substrates and MRTF-A overexpression inhibited Kidins220 expression and AMPK phosphorylation in NPCs, whereas MRTF-A inhibition, treated with the MRTF-A inhibitor CCG, partially rescued NP tissue degeneration and glycolytic enzyme expression. Our data demonstrate that MRTF-A is a critical regulator that responds to increased matrix stiffness in IVDD, and MRTF-A activation reduces NPC glycolysis by down-regulating Kidins220 and inhibiting AMPK phosphorylation.
The risk effects of corporate digitalization: exacerbate or mitigate?
This study elaborates on the risk effects of corporate digital transformation (CDT). Using the ratio of added value of digital assets to total intangible assets as a measure of CDT, this study overall reveals an inverse relationship between CDT and revenue volatility, even after employing a range of technical techniques to address potential endogeneity. Heterogeneity analysis highlights that the firms with small size, high capital intensity, and high agency costs benefit more from CDT. It also reveals that advancing information infrastructure, intellectual property protection, and digital taxation enhances the effectiveness of CDT. Mechanism analysis uncovers that CDT not only enhances financial advantages such as bolstering core business and mitigating non-business risks but also fosters non-financial advantages like improving corporate governance and ESG performance. Further inquiries into the side effects of CDT and the dynamics of revenue volatility indicate that CDT might compromise cash flow availability. Excessive digital investments exacerbate operating risks. Importantly, the reduction in operating risk associated with CDT does not sacrifice the potential for enhanced company performance; rather, it appears to augment the value of real options.
Why do travelers discontinue using integrated ride-hailing platforms? The role of perceived value and perceived risk
Despite integrated ride-hailing platforms have provided many benefits to travelers, there are also various potential risks. This study aims to examine travelers’ discontinuance behavioral intention toward integrated ride-hailing platforms. The research framework was established by extending the theory of planned behavior (TPB) with perceived value and perceived risk. Perceived value was classified into utilitarian, hedonic, and social values, while perceived risk was classified into privacy, performance, security, and financial risks. Additionally, the factors of switch cost and personal innovativeness were included. An empirical analysis was carried out using partial least-squares structural equation modeling (PLS-SEM) based on a survey conducted in Nanjing, China. Furthermore, a multi-group analysis (MGA) was performed to examine behavioral differences across demographic variables. The findings suggest that discontinuous behavioral intention is influenced by subjective norms, perceived behavioral control, and attitude. Among them, perceived behavioral control shows the strongest impact (−0.190). Perceived value, including utilitarian, hedonic, and social dimensions, negatively influences discontinuance intention, whereas the four variables of risk perception positively affect discontinuance intention. Notably, social value, performance risk, and privacy risk act higher total effects on discontinuance intention. Switch cost is negatively associated with attitude (−0.222), and positively affects discontinuance intention (0.189). Personal innovativeness has positive and stronger effects on perceived value (0.237), negative effects on perceived risk (−0.174), and negative effects on discontinuance intention. Regarding MGA results, older travelers demonstrate a stronger impact of social value on perceived value, higher-income groups exhibit greater sensitivity to security risks, and frequent travelers prioritize utilitarian value.
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