Xuewen Kang

Introduction: To characterize duration-dependent responses of Nucleus Pulposus Cells (NPCs) to Fluid Shear Stress (FSS) and identify candidate pathways associated with autophagy- and ferroptosis-related changes relevant to Intervertebral Disc Degeneration (IVDD). Methods: Primary NPCs isolated from male Sprague-Dawley rats were exposed to 12 dyn/cm² FSS for 0, 30, 60, 90, or 120 minutes. Cellular morphology, proliferation, apoptosis, mitochondrial function, autophagy-related structures, and protein expression were assessed. Chloroquine, erastin, and ferrostatin-1 were used in pharmacological comparisons. Network pharmacology, Mendelian randomization, transcriptomic analyses, machine learning, human single-cell analysis, molecular docking, and molecular dynamics simulations supported candidate prioritization. Results: Among the conditions tested, 60 min of FSS produced the most favorable cellular response, with improved proliferation and reduced apoptosis. This response was accompanied by increased autophagy-related structures, increased abundance of GPX4 and SLC7A11, and decreased abundance of ACSL4. A longer exposure of 120 minutes produced an adverse response. Network analysis identified 12 candidate hub genes, and integrated transcriptomic screening identified eight IVDD-associated candidates: ACSL1, KDM6B, MAPK14, TLR4, ALOX5, ATG7, PHF21A, and SIRT1. Human single-cell analysis provided their cellular expression context. SIRT1 was the only panel member assessed experimentally by Western blotting under FSS. Its abundance increased, and mTOR phosphorylation decreased after 60 min, with the opposite pattern after 120 minutes. Docking and simulations characterized predicted ligand–protein interactions involving SIRT1/mTOR. Discussion: The cellular and computational findings support SIRT1/mTOR signaling as a candidate pathway linking the observed responses, while functional dependence and autophagy– ferroptosis coupling require validation. Conclusion: FSS elicited duration-dependent responses in NPCs, providing a basis for targeted mechanistic investigation and future phenotype-based screening relevant to IVDD.

Introduction: Postmenopausal metabolic dysfunction is increasingly recognized as a multisystem disorder associated with estrogen deficiency, yet how gut microbial, metabolic, and tissue-level alterations co-occur across organs remains incompletely characterized. Methods: Here, we used an ovariectomy (OVX) mouse model and an integrated multiomics strategy to characterize systemic alterations in gut microbiota, metabolites in colonic contents and circulation, and tissue-level molecular profiles across the colon, liver, skeletal muscle, and bone. Results: OVX mice showed higher body weights at multiple postoperative time points, lower serum estradiol concentrations, differences in selected inflammatory and bone-turnover markers, representative histological differences across multiple tissues, and OVX–Sham differences in femoral microarchitecture. Shotgun metagenomic profiling showed significant differences in gut microbial composition, with lower evenness-sensitive diversity and differences in dominant taxa. Metabolomic profiling of colonic contents demonstrated global differences in the luminal metabolic profile, including lower relative abundances of major short-chain fatty acids, differences in bile acid composition, and prominent tryptophan-related features. At the host interface, colonic transcriptomic analysis identified annotations related to epithelial membrane polarity, vesicle trafficking, endoplasmic reticulum protein processing, and bile acid- and energy-sensing pathways. Among the 19 differential circulating bile acids and short-chain fatty acids, most were lower in OVX mice. Feature-level analyses identified multiple hepatic metabolite and bile acid differences, whereas the hepatic transcriptome did not show significant global separation; differential-expression and gene-set enrichment analyses nonetheless identified selected differences related to lipid metabolism, energy metabolism, and molecular transport. Distal tissues also displayed molecular differences, including a significant global transcriptomic difference in skeletal muscle and a significant global metabolomic difference in bone; differential bone metabolites were annotated to energy-, amino-acid-, lipid-, and cyclic guanosine monophosphate–protein kinase G (cGMP–PKG)-related pathways. Discussion: Collectively, these findings define a gut-associated, multiorgan pattern of OVX-related remodeling characterized by concurrent microbial, metabolite, and tissue-level differences. This descriptive, associative, and hypothesis-generating dataset provides a reference for future studies testing the relevance of these OVX-associated patterns to menopause-associated metabolic dysfunction.

Objective: This study aimed to investigate the role of the STAT3/POSTN/GSTP1/JNK axis in ferroptosis and extracellular matrix (ECM) metabolic imbalance in nucleus pulposus cells (NPCs) during intervertebral disc degeneration (IDD) and to explore therapeutic strategies targeting this axis.Methods: Using integrated multiomics sequencing, transcriptional regulation assays (chromatin immunoprecipitation, dual‑luciferase reporter), protein interaction analysis (CoIP), and other molecular biology approaches, we systematically elucidated the regulatory role of the STAT3/POSTN/GSTP1/JNK axis in ferroptosis of NPCs during IDD. Functional validation was performed in POSTN‑edited cell and rat models as well as in a needle‑puncture‑induced rat IDD model. A small‑molecule candidate targeting this axis was identified through virtual screening, molecular docking, and molecular dynamics simulations.Results: Periostin (POSTN) expression increased during ferroptosis and induced ferroptosis and ECM metabolic imbalance in NPCs in a concentration- and time-dependent manner. STAT3 was identified as a transcriptional regulator of POSTN and functionally coupled with POSTN to form a self-amplifying positive feedback loop, accelerating ferroptosis progression. Furthermore, POSTN impaired the binding of the GSTP1/JNK complex, leading to the depletion of cellular glutathione. Chemical screening identified pristimerin (PN) as a potential GSTP1-targeting compound, targeting the STAT3/POSTN/GSTP1/JNK axis and delaying IDD progression.Conclusion: This study identified the important role of the STAT3/POSTN/GSTP1/JNK axis in regulating ferroptosis and ECM metabolism in NPCs and highlighted PN as a promising candidate therapeutic agent for IDD. These findings provide new insights into the molecular mechanisms underlying IDD and offer new targeted therapeutic avenues for IDD.

Intervertebral disc degeneration is a major pathological contributor to low back pain and functional impairment, yet its complex molecular mechanisms have not been fully elucidated. Heat shock proteins, as important molecular chaperones and core regulators of cellular stress responses, exhibit dual protective and pathogenic roles in the process of intervertebral disc degeneration. This review summarizes the expression changes and related regulatory networks of heat shock protein family members such as HSP70, HSP90, HSP27 and GRP78 in nucleus pulposus and annulus fibrosus cells, comprehensively discussing their involvement in the molecular mechanisms of intervertebral disc degeneration by influencing key processes such as cellular homeostasis, inflammatory responses, apoptosis, autophagy, and the synthesis and degradation of the extracellular matrix. Furthermore, this review highlights HSP-centered proteostasis regulation as an emerging therapeutic framework for IVDD and discusses how HSP modulation may be integrated with biomaterials, physical stimulation, and regenerative strategies. However, direct IVDD-specific evidence for certain HSP members remains limited, and this review also highlights current knowledge gaps and future research directions for HSP-centered proteostasis regulation.

Intercellular mitochondrial transfer has recently emerged as an important concept in bone biology, providing a new framework for understanding immune–metabolic cross-talk within the bone microenvironment. This microenvironment is a dynamic system that is both metabolically active and immunologically complex, and its homeostasis relies on finely tuned communication among multiple cellular populations. Increasing evidence suggests that mitochondrial transfer is a key mechanism integrating these diverse signaling networks. In this review, we systematically summarize recent advances in mitochondrial transfer among osteolineage cells, immune cells, and vascular-associated cells, and we further discuss its multiple roles in bone remodeling, tissue repair, and the pathogenesis of osseous diseases. At the mechanistic level, special emphasis is placed on the Mitochondrial Rho GTPase 1 (MIRO1)-mediated mitochondrial transport pathway, through which mitochondria are transferred from osteolineage cells to myeloid cells, thereby driving metabolic reprogramming and modulating susceptibility to ferroptosis, ultimately helping to suppress excessive osteoclastogenesis. From a pathological perspective, dysregulated mitochondrial transfer is increasingly recognized as a common feature across a range of skeletal disorders. In glucocorticoid-induced osteoporosis (GIOP), impairment of MIRO1-dependent mitochondrial transport promotes ferroptosis resistance in osteoclast precursors. In osteoarthritis, aberrant mitochondria accelerate cartilage degeneration by disrupting coenzyme A (CoA) metabolism through Nudix Hydrolase 8 (NUDT8) and subsequently activating the cGAS–STING signaling pathway. In bone metastasis, inflammatory signals triggered by mitochondrial deoxyribonucleic acid (mtDNA) release exhibit both pro-tumorigenic and anti-tumorigenic regulatory effects. Based on these mechanisms, this manuscript also critically evaluates the translational potential of several therapeutic strategies, including mesenchymal stem cell-derived mitochondrial transplantation, nanocarrier delivery systems, and the modulation of tunneling nanotubes. Overall, targeting intercellular mitochondrial transport may offer new therapeutic opportunities for metabolic intervention and immunomodulation in bone diseases.

Excessive mechanical stress is a main cause of intervertebral disc degeneration (IDD). However, the specific mechanism remains unclear. We established in vivo and in vitro models to investigate the role of cytoskeletal proteins in excessive mechanical stress-induced NP cell pyroptosis and IDD. The expression level of Vimentin was decreased in degenerated NP cells induced by excessive mechanical stress. Knockdown of Vimentin promoted NP cell pyroptosis and IDD in rats, whereas Vimentin overexpression significantly alleviated excessive mechanical stress-induced NP cell pyroptosis and degeneration. Further mechanistic studies revealed that Vimentin ameliorated mitochondrial dysfunction triggered by excessive mechanical stress through PINK1-Parkin-dependent mitophagy, thereby attenuating NP cell pyroptosis and degeneration. Co-immunoprecipitation-mass spectrometry analysis suggested an interaction between Itgb1 and Vimentin, which was validated by Co-immunoprecipitation assays. Itgb1 enhanced Vimentin protein stability via the ubiquitin-proteasome pathway and inhibited mechanical stress-mediated Vimentin degradation. Subsequent experiments confirmed that Itgb1 reduced Vimentin ubiquitination and degradation by blocking the binding of MNAT1 to Vimentin. Itgb1 ameliorated excessive mechanical stress-induced NP cell pyroptosis and degeneration via Vimentin. Restoring Vimentin function through gene overexpression effectively inhibited NP cell pyroptosis and delayed the progression of IDD in rats. In summary, this study reveals a mechanotransduction pathway from mechanical stress sensing to cellular functional regulation in IDD, providing novel insights into the pathological mechanisms underlying IDD. Moreover, this study demonstrates that Vimentin exerts a significant protective effect against excessive mechanical stress-induced NP cell pyroptosis and IDD, offering a potential therapeutic target for the clinical management of IDD.

Background: Polyamide 6 microplastics (PA6-MPs), as emerging environmental pollutants, have attracted increasing attention due to their potential health risks. Their accumulation in human intervertebral disc tissue (86.4 particles/g) suggests a possible role in intervertebral disc degeneration (IVDD). However, direct evidence and mechanistic understanding remain limited. This study aimed to investigate the association between PA6-MPs exposure and IVDD, based on the hypothesis that PA6-MPs promote IVDD progression by targeting key regulatory molecules and disrupting cellular homeostasis. Methods: Potential PA6-related targets were predicted using multiple public databases, and IVDD-related differentially expressed genes were obtained from the GEO database. Overlapping targets were identified and analyzed through protein–protein interaction (PPI) network construction, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses to screen core targets and pathways. Molecular docking was performed to evaluate PA6–protein binding. In vitro validation was conducted using primary human nucleus pulposus cells exposed to PA6-MPs, with cell viability, proliferation, and phenotypic changes assessed by CCK-8, EdU, live/dead staining, and immunofluorescence (IF). Results: A total of 222 PA6-related targets and 1035 IVDD-associated genes were identified, yielding 10 overlapping targets. Four core targets, including NR3C1 and HDAC1, were selected. Molecular docking and experiments demonstrated stable binding and concentration-dependent inhibition of cell viability and proliferation. Conclusion: PA6-MPs may accelerate IVDD progression in a concentration-dependent manner by targeting key molecules and perturbing inflammatory homeostasis. These findings link environmental exposure to IVDD and provide a basis for future risk assessment and targeted intervention strategies.

Intervertebral disc degeneration (IDD) is a major contributor to chronic low back pain, with its pathological mechanisms closely linked to an imbalance in macrophage polarization within the immune microenvironment. Macrophages are broadly categorized into two phenotypes: pro-inflammatory M1 and anti-inflammatory/restorative M2. The dynamic equilibrium between these subsets profoundly influences IDD progression. M1 macrophages exacerbate disc degeneration by secreting pro-inflammatory cytokines (e.g., TNF-α, IL-1β) and activating NF-κB and MAPK signaling pathways, thereby amplifying inflammatory responses, apoptosis, matrix degradation, and oxidative stress. Conversely, M2 macrophages promote tissue repair and extracellular matrix (ECM) remodeling through anti-inflammatory mediators such as IL-10 and TGF-β. Emerging therapeutic strategies, including pharmacological interventions (e.g., ROS scavengers, COX-2 inhibitors), biomaterials (e.g., smart hydrogels, engineered exosomes), and multimodal therapies (e.g., gene editing combined with immune-metabolic modulation), demonstrate significant translational potential. However, challenges persist, including the impact of the disc-specific microenvironment (hypoxia, nutrient deprivation, mechanical stress) on polarization efficiency, drug delivery limitations, and fibrosis risks. Future research should focus on resolving macrophage subpopulation heterogeneity, achieving precise polarization regulation, and optimizing clinical translation to advance immunometabolic therapies for IDD.