Intervertebral disc degeneration and osteoarthritis: a common molecular disease spectrum

Single-cell RNA sequencing-guided engineering of mitochondrial therapies for intervertebral disc degeneration by regulating mtDNA/SPARC-STING signaling

Intervertebral disc degeneration (IVDD) is a leading cause of discogenic low back pain, contributing significantly to global disability and economic burden. Current treatments provide only short-term pain relief without addressing the underlying pathogenesis. Herein we report engineering of biomimetic therapies for IVDD guided by single-cell RNA-sequencing data from human nucleus pulposus tissues, along with validation using animal models. In-depth analyses revealed the critical role of mitochondrial dysfunction in fibrotic phenotype polarization of nucleus pulposus cells (NPCs) during IVDD progression. Consequently, mitochondrial transplantation was proposed as a novel therapeutic strategy. Transplanted exogeneous mitochondria improved mitochondrial quality control in NPCs under pathological conditions, following endocytosis, separate distribution or fusion with endogenous mitochondria, and transfer to neighboring cells by tunneling nanotubes. Correspondingly, intradiscal mitochondrial transplantation significantly delayed puncture-induced IVDD progression in rats, demonstrating efficacy in maintaining mitochondrial homeostasis and alleviating pathological abnormalities. Furthermore, exogenous mitochondria were engineered with a bioactive, mitochondrial-targeting macromolecule to impart anti-oxidative and anti-inflammatory activities. The obtained multi-bioactive biotherapy exhibited significantly enhanced benefits in IVDD treatment, in terms of reversing IVDD progression and restoring structural integrity through the mtDNA/SPARC-STING signaling pathways. Overall, our engineered mitochondrial therapies hold great promise for treating IVDD and other musculoskeletal diseases linked to mitochondrial dysfunction.

The BATF2-ATF3 axis exacerbates intervertebral disc degeneration via inducing mitochondrial dysfunction

Intervertebral disc degeneration (IVDD) is the leading cause of low back pain, spinal instability, disc herniation and spinal stenosis, which is a serious risk to human health, yet its molecular mechanisms remain unknown. The basic leucine zipper ATF-like transcription factor 2 (BATF2) has been reported to play important roles in regulating cell proliferation, apoptosis, and inflammatory responses; however, its specific role in IVDD remains unknown. We firstly demonstrated BATF2 expression was significantly upregulated in degenerated nucleus pulposus (NP) tissues. Functional assays demonstrated that BATF2 overexpression promoted nucleus pulposus cell (NPC) apoptosis and extracellular matrix (ECM) catabolism in vitro and vivo. It is further demonstrated that BATF2 impairs mitochondrial function by disturbing mitochondrial redox homeostasis. Mechanistically, BATF2 stabilizes the activating transcription factor 3 (ATF3) by inhibiting the ubiquitination modification of ATF3. Notably, ATF3 overexpression accelerated NPC apoptosis and ECM degradation. More importantly, ATF3 knockdown reversed the effects of BATF2-induced mitochondrial dysfunction and IVDD progression. These results suggest that BATF2-ATF3 axis disrupts mitochondrial redox homeostasis to impair mitochondrial function, thereby exacerbating the progression of IVDD. Targeting BATF2-ATF3 axis could provide a potential strategy for IVDD treatment.

Selenium nanozyme-crosslinked composite hydrogel for promoting cartilage regeneration in osteoarthritis via an integrated 'outside-in' and 'inside-out' strategy

Osteoarthritis (OA), a degenerative joint disease, is characterized by chondrocyte senescence, extracellular matrix (ECM) degradation, and chronic inflammation, with limited regenerative capacity. Current therapies primarily provide symptom relief, therefore highlighting the need for more effective strategies to address OA's multifactorial pathology. This study introduces an innovative selenium nanozyme-crosslinked injectable composite hydrogel (Se/PRP-OGel), which combines selenium nanoparticles (SeNPs) with platelet-rich plasma (PRP) in a biocompatible oxidized chondroitin sulfate-gelatin scaffold (OGel), to address OA through an integrated "outside-in" and "inside-out" strategy. The "outside-in" strategy utilizes SeNPs to scavenge reactive oxygen species (ROS), alleviate oxidative stress, and restore redox balance, thereby reducing extracellular damage and modulating inflammation in the OA microenvironment. Concurrently, the "inside-out" strategy utilizes PRP's bioactive growth factors (e.g., TGF-β, IGF, FGF) to rejuvenate senescent chondrocytes, stimulate proliferation, and enhance ECM synthesis, creating a regenerative microenvironment. The results showed that Se/PRP-OGel demonstrated excellent biocompatibility, reduced ROS levels, mitigated chondrocyte senescence, and balanced ECM homeostasis. Moreover, it promoted cartilage repair, pain relief, and functional restoration in an OA rat model. This dual approach interrupts OA's degenerative cycle and fosters cartilage regeneration, providing a groundbreaking solution for effective cartilage regeneration and OA treatment.

Impact of asymmetric L4-L5 facet joint degeneration on lumbar spine biomechanics using a finite element approach

This study investigated the effects of asymmetric facet joint degeneration on spinal behavior and adjacent structures using finite element analysis (FEA). Facet joints play a critical role in providing spinal stability and facilitating movement. Degenerative changes in these joints can lead to reduced spinal function and pain. Specifically, asymmetric degeneration occurs when one side deteriorates more rapidly due to alignment issues, subsequently impacting adjacent structures. In this study, facet joint degeneration grades (G00, G40, G42, and G44) were assigned to the L4-L5 segment to simulate spinal behavior during extension, left and right lateral bending, and left and right axial rotations. As degeneration progressed, the range of motion in the affected segment decreased, resulting in altered stress distribution across the intervertebral discs and posterior bone. The analysis showed that the posterior bending angle during extension decreased with increasing degeneration severity. Additionally, during lateral bending, the bending angle in the corresponding direction decreased, while the anterior bending angle increased. Maximum equivalent stress analysis of the intervertebral disc in the affected segment revealed a decreasing trend as degeneration worsened, a pattern also observed during extension, left lateral bending, and right axial rotation. In the G40 model, the maximum equivalent stress in the posterior bone of L4 and L5 exhibited a significant disparity between the left and right sides. These findings provide quantitative insights into the progression of spinal degeneration, enhancing our understanding of how asymmetric facet joint degeneration (FJD) affects spinal motion and adjacent structures.

Injectable hydrogel microspheres promoting inflammation modulation and nucleus pulposus-like differentiation for intervertebral disc regeneration

Local inflammation modulation and stem cell therapy have attracted much attention in the treatment of intervertebral disc degeneration (IDD). However, severe oxidative stress and limited nucleus pulposus (NP)-like differentiation of stem cells largely impair biomaterial implantation's therapeutic efficacy. Due to their excellent performance in injectability and flowability, and minor compression to NP tissue, hydrogel microspheres have become an attractive carrier for IDD treatment. Herein, an injectable hydrogel microsphere consisting of Wnt5a-mimetic peptide Foxy5- and the antioxidative peptide-grafted gelatin methacryloyl matrix (GFA), was developed as a stem cell delivery system for IDD therapy. Being fabricated and encapsulating bone marrow-derived mesenchymal stem cells (BMSCs) using the microfluidic technology, GFA hydrogel microspheres ameliorate IDD by promoting inflammation inhibition, NP-like differentiation and extracellular matrix regeneration. They efficiently eliminated reactive oxygen species, and downregulated the inflammation level through the inhibition of interleukin-17B/nuclear factor-κB signaling pathway. Moreover, the NP-like differentiation of BMSCs was effectively stimulated by Foxy5 via the calcium/calmodulin dependent protein kinase kinase 2/protein kinase A/sex determining region Y box protein 9 signaling pathway, thereby leading to a rebalance between the generation and degradation of NP matrix. In vivo rat IDD model demonstrated that BMSC-loaded GFA hydrogel microspheres mitigated local inflammation, preserved disc height, and promoted intervertebral disc regeneration. In conclusion, this study introduces an BMSC-loaded injectable hydrogel microspheres as a promising therapy for regulating the microenvironment and alleviating the progression of IDD.

Advances in cell therapy for orthopedic diseases: bridging immune modulation and regeneration

Orthopedic diseases pose significant challenges to public health due to their high prevalence, debilitating effects, and limited treatment options. Additionally, orthopedic tumors, such as osteosarcoma, chondrosarcoma, and Ewing sarcoma, further complicate the treatment landscape. Current therapies, including pharmacological treatments and joint replacement, address symptoms but fail to promote true tissue regeneration. Cell-based therapies, which have shown successful clinical results in cancers and other diseases, have emerged as a promising solution to repair damaged tissues and restore function in orthopedic diseases and tumors. This review discusses the advances and potential application of cell therapy for orthopedic diseases, with a particular focus on osteoarthritis, bone fractures, cartilage degeneration, and the treatment of orthopedic tumors. We explore the potential of mesenchymal stromal cells (MSCs), chondrocyte transplantation, engineered immune cells and induced pluripotent stem cells to enhance tissue regeneration by modulating the immune response and addressing inflammation. Ultimately, the integration of cutting-edge cell therapy, immune modulation, and molecular targeting strategies could revolutionize the treatment of orthopedic diseases and tumors, providing hope for patients seeking long-term solutions to debilitating conditions.

Injectable ECM-mimetic dynamic hydrogels abolish ferroptosis-induced post-discectomy herniation through delivering nucleus pulposus progenitor cell-derived exosomes

Discectomy-induced ferroptosis of nucleus pulposus cells (NPCs) contributes to postoperative lumbar disc herniation (LDH) recurrence and intervertebral disc degeneration (IDD). We discover that nucleus pulposus progenitor cells (NPPCs) could imprint ferroptosis resistance into NPCs through exosome-dependent intercellular transmission of miR-221-3p. Based on these findings, we first develop synthetically-tailored NPPC-derived exosomes with enhanced miR-221-3p expression and NPC uptake capacity, which are integrated into an injectable hydrogel based on extracellular matrix (ECM) analogues. The ECM-mimetic hydrogel (HACS) serves as a biomimetic filler for the post-operative care of herniated discs, which could be facilely injected into the discectomy-established nucleus pulposus (NP) cavity for localized treatment. HACS-mediated in-situ exosome release in the NP cavity enables marked ferroptosis inhibition in NPCs that not only prevents LDH recurrence but also reverses the IDD symptoms, leading to robust restoration of NP structure and functions. In summary, this study offers a promising approach for treating disc herniation.

Optimizing the clinical adoption of total joint replacement of the lumbar spine through imaging, robotics and artificial intelligence

INTRODUCTION

The objective of this article is to assess the potential of imaging, robotics, and artificial intelligence (AI) to significantly improve spine care, preoperative planning and surgery.

AREAS COVERED

This article describes the development of lumbar total joint replacement (TJR) of the spine (MOTUS, 3Spine, Chattanooga, TN, U.S.A.). We discuss the evolution of intra-operative imaging, robotics, and AI and how these trends can intersect with lumbar TJR to optimize the safety, efficiency, and accessibility of the procedure.

EXPERT OPINION

By preserving natural spinal motion, TJR represents a significant leap forward in the treatment of degenerative spinal conditions by providing an alternative to fusion. This transformation has already occurred and is continuing to evolve in the primary synovial joints such as hip, knee, shoulder and ankle where arthroplasty outcomes are now so superior that fusion is considered a salvage procedure. The convergence of imaging, robotics and AI is poised to reshape spine care by enhancing precision and safety, personalizing treatment pathways, lowering production costs, and accelerating adoption. However, the key challenges include ensuring continued collaboration between surgeons, researchers, manufacturers, and regulatory bodies to optimize the potential of TJR.

LT-α Facilitates the Aerobic Glycolysis and M1 Polarization of Macrophages by Activating the NF-κB Signaling Pathway in Intervertebral Disc Degeneration

Purpose

Injury and inflammatory activate and polarize macrophages in intervertebral disc degeneration (IVDD). Further research needs to be carried to explore the mechanisms that regulate macrophage polarization, providing new insights and targets for IVDD treatment. The aim of our study was to evaluate the influence of LT-α on aerobic glycolysis (AG) and polarization in macrophages.

Methods

M0 macrophages were achieved by stimulating THP-1 cells with PMA. M1 macrophages were obtained by IFN-γ and LPS stimulation in M0 macrophages. Energy metabolomics, AG and apoptosis related protein expression, migration and invasion measurement, proliferation was analyzed. Polarization of macrophages, AG associated genes expression, macrophage recruitment was evaluated. NF-κB signaling was ascertained by laser confocal and Western blotting.

Results

The propanoate metabolism pathway was enriched in LT-α overexpressing M0 macrophages, and various energy metabolites were detected. Glucose absorption, lactic acid production, and levels of AG proteins were strikingly increased in LT-α overexpression macrophages and remarkably repressed in LT-α knockdown macrophages, accompanied by activated and inactivated NF-κB signaling, respectively. Suppressed migration and invasion ability, restrained proliferation, activated AG, and enhanced apoptosis were observed in nucleus pulposus (NP) cells treated by LT-α overexpressed macrophages, accompanied by reduced macrophage recruitment, with opposite results when treated by LT-α knockdown macrophages. The enhanced M1 polarization and activated AG in LT-α overexpression macrophages were abolished by co-culturing with NF-κB inhibitor.

Conclusion

LT-α facilitates the AG and M1 polarization of macrophages via activating the NF-κB signaling pathway.

Bone-brain interaction: mechanisms and potential intervention strategies of biomaterials

Following the discovery of bone as an endocrine organ with systemic influence, bone-brain interaction has emerged as a research hotspot, unveiling complex bidirectional communication between bone and brain. Studies indicate that bone and brain can influence each other's homeostasis via multiple pathways, yet there is a dearth of systematic reviews in this area. This review comprehensively examines interactions across three key areas: the influence of bone-derived factors on brain function, the effects of brain-related diseases or injuries (BRDI) on bone health, and the concept of skeletal interoception. Additionally, the review discusses innovative approaches in biomaterial design inspired by bone-brain interaction mechanisms, aiming to facilitate bone-brain interactions through materiobiological effects to aid in the treatment of neurodegenerative and bone-related diseases. Notably, the integration of artificial intelligence (AI) in biomaterial design is highlighted, showcasing AI's role in expediting the formulation of effective and targeted treatment strategies. In conclusion, this review offers vital insights into the mechanisms of bone-brain interaction and suggests advanced approaches to harness these interactions in clinical practice. These insights offer promising avenues for preventing and treating complex diseases impacting the skeleton and brain, underscoring the potential of interdisciplinary approaches in enhancing human health.

Correlation analysis of spine-pelvis parameters and age with lumbar paravertebral muscle degeneration in middle age and older adults

OBJECTIVE

To analyze the correlation between spine-pelvis parameters, age and lumbar paravertebral muscle degeneration in middle-aged and older adults.

METHOD

This retrospective study involved 143 middle-aged and elderly patients with suspected lumbar paravertebral muscle degeneration treated at The Third Hospital of Hebei Medical University between January 2021 and June 2023. Based on confirmed diagnoses, patients were divided into a degenerative group (57 cases) and a non-degenerative group (86 cases). Clinical data were analyzed to explore the relationship between pelvic parameters, age, and lumbar paravertebral muscle degeneration. Univariate and multivariate logistic regression were used to identify risk factors, and Receiver Operating Characteristic (ROC) analysis was performed to evaluate the predictive value of these factors. Differences in areas under the curve (AUC) for clinical factors were assessed using the DeLong test.

RESULT

No significant differences were found between the two groups in clinical data, except for age (P<0.05). Comparison of spine-pelvis parameters revealed that the pelvic tilt (PT) and pelvic incidence (PI) were significantly higher in the degenerative group than those in the non-degenerative group, while the sacral slope (SS) and lumbar lordosis (LL) were lower (all P<0.05). Additionally, the CSA ratios between the third and fourth lumbar vertebrae (L3/4) and between the fourth and fifth lumbar vertebrae (L4/5) were found to be significantly lower in the degenerative group as opposed to those in the non-degenerative group (all P<0.05). Kendall's analysis showed that age and spine-pelvis parameters (PT, PI) were positively correlated with lumbar paravertebral muscle degeneration (OR=0.733, 0.639, 0.695; P<0.0001). In contrast, spine-pelvic parameters (SS, LL) were negatively correlated with degeneration (OR=-0.695, -0.698; P<0.0001). Pearson's correlation analysis also revealed a positive correlation between age and spine-pelvic parameters (PT, PI) (r=0.826, 0.985, P<0.001), and a negative correlation between age and spine-pelvic parameters (SS, LL) (r=-0.861, -0.942, P<0.001). Additionally, spine-pelvic parameter PT was negatively correlated with CAS ratio of L3/4 disc levels (r=-0.412, P<0.000). Logistic multivariate regression analysis identified age (OR=0.616, P<0.0001), PT (OR=0.827, P<0.0001), SS (OR=1.095, P=0.004), LL (OR=1.148, P=0.019), PI (OR=0.853, P<0.0001), CAS ratio of L3/4 (OR=1.977, P=0.002) and CAS ratio of L4/5 (OR=1.739, P=0.009) levels as independent risk factors for lumbar paravertebral muscle degeneration (all P<0.05). ROC results showed that the AUCs for age, PT, SS, LL, PI, L3/4, and L4/5 in predicting lumbar paravertebral muscle degeneration in middle-aged and elderly people were 0.949, 0.828, 0.642, 0.779, 0.850, 0.683, 0.677, respectively (all P<0.05).

CONCLUSION

Lumbar paravertebral muscle degeneration in middle-aged and elderly individuals is significantly associated with both age and spine-pelvic parameters. These findings suggest that degeneration is not only age-related but also influenced by spine-pelvic configuration, providing a clinical basis for preventing lumbar paravertebral muscle degeneration.

Nucleus pulposus cell-mimicking nanoparticles for cell-specific HIF1A editing to modulate SASP-mediated disc inflammation via autophagy activation

Traditional methods of plasmid delivery, including viral vectors, lipofection, and electroporation, are widely used for gene editing but have limitations, such as cellular toxicity, limited transfection efficiency in primary cells, and nonspecific side effects. Here, we report the development of nucleus pulposus cell (NPC)-mimicking nanoparticles (HIF1A@NNP) with an NPC membrane as the shell and pcDNA3.1+-rHIF1A encapsulated in the core via extrusion. HIF1A@NNP exhibited a protein expression pattern similar to that of the NPC membrane and displayed a typical vesicle profile. Compared to liposomes and lentiviruses, HIF1A@NNP overexpressed HIF1A in NPCs while improving cell viability. HIF1A@NNP was more readily internalized by NPCs than by other cell types, with fewer effects on vascularization, nerve growth, and macrophage polarization than HIF1A overexpression using lipo3000. HIF1A@NNP reduced the apoptotic rate and inhibited the senescent phenotype, as evidenced by reduced DNA damage, lower levels of senescence-related proteins, and fewer SA-β-Gal-positive cells. HIF1A@NNP induced a senescence-associated secretory phenotype (SASP), which enhanced macrophage migration and M1 polarization. Additionally, HIF1A@NNP activated autophagy in NPCs. In summary, HIF1A@NNP demonstrated satisfactory biocompatibility, alleviated the SASP, and inhibited SASP-mediated macrophage recruitment and inflammatory polarization, leading to reduced disc degeneration and providing a promising strategy for combating intervertebral disc degeneration. STATEMENT OF SIGNIFICANCE: Conventional plasmid delivery methods like viral vectors, lipofection, and electroporation struggle with cellular toxicity and inefficiency in primary cells. Non-cell-specific HIF1A activation via these methods may exacerbate inflammation and pain, as HIF1A drives angiogenesis and dendritic ingrowth into the disc. Thus, a cell-specific delivery strategy could circumvent such adverse effects. Our study introduces HIF1A@NNP, a nanoparticle mimicking nucleus pulposus cells (NPCs), with an NPC membrane shell encapsulating pcDNA3.1+-rHIF1A. It preferentially targets NPCs, achieving superior HIF1A overexpression and cell viability compared to liposomes and lentiviruses. This represents a highly promising and potentially transformative approach against intervertebral disc degeneration.

Reprogramming to restore youthful epigenetics of senescent nucleus pulposus cells for mitigating intervertebral disc degeneration and alleviating low back pain

Aging is a pivotal risk factor for intervertebral disc degeneration (IVDD) and chronic low back pain (LBP). The restoration of aging nucleus pulposus cells (NPCs) to a youthful epigenetic state is crucial for IVDD treatment, but remains a formidable challenge. Here, we proposed a strategy to partially reprogram and reinstate youthful epigenetics of senescent NPCs by delivering a plasmid carrier that expressed pluripotency-associated genes (Oct4, Klf4 and Sox2) in Cavin2-modified exosomes (OKS@M-Exo) for treatment of IVDD and alleviating LBP. The functional OKS@M-Exo efficaciously alleviated senescence markers (p16INK4a, p21CIP1 and p53), reduced DNA damage and H4K20me3 expression, as well as restored proliferation ability and metabolic balance in senescent NPCs, as validated through in vitro experiments. In a rat model of IVDD, OKS@M-Exo maintained intervertebral disc height, nucleus pulposus hydration and tissue structure, effectively ameliorated IVDD via decreasing the senescence markers. Additionally, OKS@M-Exo reduced nociceptive behavior and downregulated nociception markers, indicating its efficiency in alleviating LBP. The transcriptome sequencing analysis also demonstrated that OKS@M-Exo could decrease the expression of age-related pathways and restore cell proliferation. Collectively, reprogramming by the OKS@M-Exo to restore youthful epigenetics of senescent NPCs may hold promise as a therapeutic platform to treat IVDD.

Harnessing Anti-Inflammatory and Regenerative Potential: GelMA Hydrogel Loaded with IL-10 and Kartogenin for Intervertebral Disc Degeneration Therapy

Intervertebral disc degeneration (IVDD) is a major contributor to chronic back pain and disability, with limited effective therapeutic options. Current treatment options, including conservative management and surgical interventions, often fail to effectively halt disease progression and come with notable side effects. IVDD is characterized by the breakdown of the extracellular matrix (ECM) and the infiltration of inflammatory cells, which exacerbate disc degeneration. This study presents a novel therapeutic strategy aimed at addressing the dual challenges of inflammation and ECM degradation in IVDD. We developed a gelatin methacryloyl (GelMA) hydrogel system loaded with interleukin-10 (IL-10), an anti-inflammatory cytokine, and kartogenin (KGN), a small-molecule compound known for its regenerative properties. The KGN + IL-10@GelMA hydrogel was designed to deliver these agents in a controlled manner directly to the degenerated disc, targeting both the inflammatory microenvironment and the promotion of nucleus pulposus (NP) tissue regeneration. In a puncture-induced IVDD model, this hydrogel system effectively delayed the degenerative progression and facilitated NP regeneration. Our findings suggest that the KGN + IL-10@GelMA hydrogel holds significant potential as a nonsurgical treatment option for IVDD, offering a promising approach to mitigate the progression of IVDD and enhance disc repair.

Transcriptome Data Combined With Mendelian Randomization Analysis Identifies Key Genes Associated With Mitochondria and Programmed Cell Death in Intervertebral Disc Degeneration

Background

Intervertebral disc degeneration (IDD) is a major cause of cervical and lumbar diseases, significantly impacting patients' quality of life. Mitochondria and cell death have been implicated in IDD, but the key related genes remain unknown.

Methods

Differentially expressed genes (DEGs) between IDD and control samples were identified using GSE70362. Mitochondria-related genes (MRGs) and programmed cell death-related genes (PCDRGs) were intersected with DEGs to find DE-MRGs and DE-PCDRGs. Weighted gene co-expression network analysis (WGCNA) identified key module genes, and the overlap with DEGs revealed candidate genes. Mendelian randomization (MR) analysis was used to determine genes causally linked to IDD. Machine learning and expression validation further refined key genes, which were then used to build a nomogram to predict IDD risk. Additionally, gene set enrichment analysis (GSEA), immune infiltration, and single-cell analysis were performed.

Results

A total of 515 DEGs were intersected with 224 key module genes, yielding 31 candidate genes. Six genes-BCKDHB, BID, TNFAIP6, VRK1, CAB39L, and TMTC1-showed a causal relationship with IDD. BID, TNFAIP6, and TMTC1 were further identified as key genes through machine learning and validation. A nomogram was developed based on these genes. GSEA revealed BID and TMTC1 were enriched in N-glycan biosynthesis, TNFAIP6 and TMTC1 in aminoacyl tRNA biosynthesis, and BID and TMTC1 in ribosomal pathways. Activated dendritic cells, CD56dim natural killer cells, monocytes, and other immune cells were elevated in IDD, with TNFAIP6 strongly correlating with activated dendritic cells. Key genes were expressed at higher levels in degraded samples.

Conclusion

BID, TMTC1, and TNFAIP6 were identified as key genes linked to mitochondria and cell death in IDD, offering new insights for diagnosis and treatment.

Prediction Model and Risk Factor Analysis of Adjacent Segment Disease After L4-5 Transforaminal Lumbar Interbody Fusion Through Preoperative Radiographic Features

STUDY DESIGN

A retrospective study.

OBJECTIVE

To investigate the risk of adjacent segment disease (ASD) after L4-5 transforaminal lumbar interbody fusion (TLIF) in patients diagnosed with lumbar spinal stenosis (LSS), a prediction model for ASD is established and validated.

METHODS

A retrospective study was carried out on a sample of 290 patients who underwent L4-5 TLIF at Zhongda Hospital, Southeast University, from January 2015 to January 2021. The study collected baseline data and preoperative radiographic features of L3-4 and L5-S1. The determination of the outcome variable was based on X-ray results spanning over 24 months and JOA scores. Multivariate logistic regression was used to identify the risk factors in constructing a nomogram.

RESULTS

Independent risk factors for L3-4 degeneration after TLIF included osteoarthritis of L3-4 facet joints, L3-4 foraminal stenosis, L4 upper endplate osteochondritis, L3-4 local lordosis angle, and L3-4 spinal stenosis. Independent risk factors for L5-S1 degeneration after TLIF included osteoarthritis of L5-S1 facet joints, L5-S1 intervertebral disc degeneration, L5-S1 spinal stenosis, L5-S1 coronal imbalance, and S1 upper endplate osteochondritis. A predictive model was developed. The AUC for the prediction models at L3-4 and L5-S1 were .945 and .956. The calibration curve demonstrated good consistency between the predicted and actual probabilities. The DCA curve indicated the clinical benefit and practical value of this predictive model.

CONCLUSION

This study established nomograms for postoperative degeneration at L3-4 and L5-S1 based on selected preoperative radiographic features. These models provide a valuable auxiliary decision-making system for clinicians and aid in early surgical decisions.

Engineered Cell Membrane-Coated Keratin Nanoparticles Attenuated Intervertebral Disc Degeneration by Remodeling the Disc Microenvironment

Characterized by a cascade of profound changes in nucleus pulposus (NP) cells, extracellular matrix (ECM), and biomechanics, intervertebral disc degeneration is a common multifactorial condition that may lead to various degenerative lumbar disorders. Therapeutic strategies targeting a single factor have shown limited efficacy in treating disc degeneration, and approaches that address multiple pathological ingredients are barely reported. In this study, engineered cell membrane-encapsulated keratin nanoparticles are developed to simultaneously alleviate NP cell senescence and promote ECM remodeling. To achieve this, salivary acid glycoengineered adipose mesenchymal stem cell membranes are used to coat keratin, a core protein for structural support and cellular protection. The synthesized cell membrane-coated keratin nanoparticles (MKNs) effectively protected mitochondrial integrity in NP cells from oxidative stress-induced damage. Moreover, MKNs modulate mitochondrial metabolism and attenuate NP cell senescence. In addition, MKNs activate integrins at the cell membrane and enhance the interactions between NP cells and ECM, resulting in increased ECM anabolism and decreased catabolism. The proposed multi-targeted strategy to block the degenerative cycle inside the disc is efficacious for treating disc degeneration and may have the potential for clinical application.

Correlation between paraspinal muscle fat infiltration and thoracic vertebral degeneration based on phantom-less QCT: a novel insight into thoracic vertebral degeneration

PURPOSE

This study aimed to elucidate the correlation between the degree of fat infiltration (FI) in thoracic paraspinal muscles and thoracic vertebral degeneration (TVD).

METHODS

This cross-sectional study comprised 474 patients who underwent standard thoracic computed tomography (CT) scans. The FI was quantified as the percentage of adipose tissues within the cross-sectional area of thoracic paraspinal muscles. Thoracic vertebra was assessed in terms of osteoporosis, ossification of the anterior longitudinal ligament (OALL), ossification of the posterior longitudinal ligament (OPLL), intervertebral disc calcification, intervertebral disc cavity, and facet joint osteoarthritis (FJO). Logistic regression, linear regression, subgroup, and receiver operating characteristic (ROC) analyses were assessed to evaluate the association between FI and TVD.

RESULTS

Multivariate logistic regression revealed that more severe FI was closely associated with more serious osteoporosis (P < 0.001). Furthermore, after adjusting for only age, higher FI was significantly associated with nastier FJO (P < 0.05). In male patients, severe FI was greatly associated with worse osteoporosis (P < 0.05). In female patients, severe FI maintained close correlations with more severe osteoporosis and FJO (P < 0.05). Furthermore, in patients aged < 60 or ≥ 60 years, higher FI had a strong correlation with more severe osteoporosis (P < 0.001). In patients aged < 60 years, higher FI was associated with worse intervertebral disc calcification, OALL, and FJO (P < 0.05). Meanwhile, in patients aged ≥ 60 years, increased FI was only associated with severe OPLL (P < 0.05). Multivariate linear regression showed that FI negatively correlated with bone mineral density in the general population and different sex and age groups (P < 0.001). ROC analysis indicated that FI could predict the occurrence of TVD (P < 0.05).

CONCLUSION

Higher FI is associated with more severe TVD. Studies on TVD are currently limited; therefore, this study enriches the related research on TVD, and our findings would facilitate the early prediction and diagnosis of TVD in clinical practice. Furthermore, our findings indicate that thoracic spine pain (TSP) caused by TVD can be prevented, potentially improving the prognosis of patients with TSP.

Epidemiological trends and characteristics of osteoarthritis in China during 1990-2021

Background

This study aimed to comprehensively analyze the incidence, prevalence, and disability-adjusted life years (DALYs) of osteoarthritis (OA) in China from 1990 to 2021 by age, sex, joint sites, high body mass index (BMI) and sociodemographic index (SDI).

Methods

Data and methodologies from the Global Burden of Diseases (GBD) Study 2021 were obtained to evaluate the burden of OA in China. This assessment was conducted by estimating the number of incident cases, prevalent cases, DALYs, and corresponding age-standardized rates (ASRs). The estimated annual percentage change was employed to delineate the trends over time.

Results

In China, the number of OA incidence cases, prevalence cases, and DALYs increased to 11.65 million, 152.85 million and 5.33 million in 2021, respectively, exhibiting a consistent upward trend over the years. The ASRs of OA incidence, prevalence, and DALYs rose 13.86 %, 14.34 %, and 16.23 % from 1990 to 2021, respectively, with knee OA most affected. In 2021, OA incidence, prevalence, and DALYs were higher in women than in men, and increased with age for both sexes, peaking at ages 50-54 for incidence and 55-59 for prevalence and DALYs. DALYs of OA attributed to high BMI increased rapidly, and high BMI contributed to 21.64 % of the total age-standardized DALYs rate of OA in China. Positive correlations were observed between ASRs and China's SDI from 1990 to 2021.

Conclusion

OA constitutes a significant public health challenge in China, with a persistently high disease burden. There is a pressing need to enhance public understanding of the risk factors associated with OA and to promote preventive strategies to mitigate the future burden of this disorder.The translational potential of this article China has the largest elderly population and the highest prevalence of OA globally. Updating and analyzing epidemiological data of OA in China will offer the public, healthcare professionals, and policymakers the most current, comprehensive, and comparable information, which holds significant translational potential.

The anti-oxidation related bioactive materials for intervertebral disc degeneration regeneration and repair

Intervertebral disc degeneration (IVDD) is a prevalent chronic spinal condition characterized by the deterioration of the intervertebral discs (IVD), leading to structural damage and associated pain. This degenerative process is closely linked to oxidative stress injury, which plays a pivotal role in its onset and progression. Oxidative stress in IVDD results from the excessive production of reactive oxygen species (ROS) and impaired ROS clearance mechanisms, disrupting the redox balance within the intervertebral disc. Consequently, oxidative stress contributes to the degradation of the extracellular matrix (ECM), promotes cell apoptosis, and exacerbates disc tissue damage. Current treatment options for IVDD face significant challenges in effectively alleviating the oxidative stress-induced damage and facilitating disc tissue repair. However, recent advancements in biomaterials have opened new avenues of hope for IVDD treatment by addressing oxidative stress. In this review, we first provide an overview of the pathophysiological process of IVDD and explore the mechanisms and pathways associated with oxidative stress injury. Then, we delve into the current research on antioxidant biomaterials employed in the treatment of IVDD, and outline the advantages and limitations of hydrogel, nanomaterials, polyphenol and inorganic materials. Finally, we propose the future research direction of antioxidant biomaterials in IVDD treatment. The main idea of this review is shown in Scheme 1.

Integrated bulk and single-cell RNA sequencing to identify potential biomarkers in intervertebral disc degeneration

BACKGROUND

Nucleus pulposus (NP) deterioration plays a significant role in the development of intervertebral disc degeneration (IVDD) and low back pain (LBP). This paper aims to identify potential genes within degenerated NP tissue and elucidate the pathogenesis of IVDD through bioinformatics analysis.

METHODS

We conducted a transcriptomic analysis of patient's degenerative NP tissue employing advanced bioinformatics techniques and machine learning algorithms. Utilizing hdWGCNA, we successfully acquired WGCNA single-cell sequencing data and pinpointed crucial genes implicated in IVDD. Subsequently, we employed the Monocle3 package to perform pseudotime sequence analysis, enabling the identification of genes associated with the differentiation and developmental processes of NP tissue. Following this, normalized and logarithmically transformed the bulk sequencing data. Subsequently, we conducted preliminary screening using single-factor logistic regression on the genes derived from single-cell sequencing. Next, we applied two machine learning techniques, namely, SVM-RFE and random forest, to discern pivotal pathogenic genes. Finally, we used validation sets to verify trends and qualitativeness and performed in vitro and in vivo validation analyses of normal and degenerative NP tissues.

RESULTS

909 genes associated with IVDD were identified through hdWGCNA, while pseudotime sequence analysis uncovered 1964 genes related to differentiation and developmental processes. The two had 208 genes in common. Subsequently, we conducted an initial screening of single-cell genes by integrating the bulk database with single logistic regression. Next, we utilized machine learning techniques to identify the IVDD genes CDH, DPH5, and SELENOF. PCR analysis confirmed that the expression of CDH and DPH5 in degraded nucleus pulposus cells (NPCs) was decreased by 31% and 28% in vivo, and 36% and 29% in vitro, respectively, while SELENOF showed the opposite trend. Furthermore, IVDD was validated through imaging and histological staining.

CONCLUSION

As pathogenic genes in IVDD, our findings indicate that CTH, DPH5, and SELENOF are important players and might be promising therapeutic targets for IVDD treatment.

SPP1-ITGα5/β1 Accelerates Calcification of Nucleus Pulposus Cells by Inhibiting Mitophagy via Ubiquitin-Dependent PINK1/PARKIN Pathway Blockade

Low back pain (LBP) caused by nucleus pulposus degeneration and calcification leads to great economic and social burden worldwide. Unexpectedly, no previous studies have demonstrated the association and the underlying mechanism between nucleus pulposus tissue degeneration and calcification formation. Secreted Phosphoprotein 1 (SPP1) exerts crucial functions in bone matrix mineralization and calcium deposition. Here, a novel function of SPP1 is reported, namely that it can aggravate nucleus pulposus cells (NPs) degeneration by negatively regulating extracellular matrix homeostasis. The degenerated NPs have a higher mineralization potential, which is achieved by SPP1. Mechanistically, SPP1 can accelerate the degeneration of nucleus pulposus cells by activating integrin α5β1 (ITGα5/β1), aggravating mitochondrial damage and inhibiting mitophagy. SPP1-ITGα5/β1 axis inhibits mitophagy by PINK1/PARKIN pathway blockade. In conclusion, SPP1 activates ITGα5/β1 to inhibit mitophagy, accelerates NPs degeneration, and induces calcification, thereby leading to intervertebral disc degeneration (IVDD) and calcification, identifying the potentially unknown mechanism and relationship between IVDD and calcification. Important insights are provided into the role of SPP1 in nucleus pulposus calcification in IVDD by inducing nucleus pulposus cell senescence through inhibition of mitophagy and may help develop potential new strategies for IVDD treatment.

Human molecular mechanisms of discogenic low back pain: A scoping review

The limited understanding of the mechanisms underlying human discogenic low back pain (DLBP) has hampered the development of effective treatments. While there is much research on disc degeneration, the association between degeneration and pain is weak. Therefore, there is an urgent need to identify pain-inducing molecular mechanism to facilitate the development of mechanism-specific therapeutics. This scoping review aims to determine the current knowledge of molecular mechanisms associated with human DLBP. A systematic search on CENTRAL, CINAHL, Citation searching, ClinicalTrials.gov, Embase, Google Scholar, MEDLINE, PsycINFO, PubMed, Scopus, Web of Science, and World Health Organization was performed. Studies with human DLBP as diagnosed by discography or imaging that analyzed human disc tissues and reported pain-related outcomes were included, and those on predominant radicular pain were excluded. The search returned 6012 studies. Most studies did not collect pain-related outcomes. Those that included pain assessment relied on self-report of pain intensity and disability. Six studies qualified for data extraction and synthesis. The main molecular mechanisms associated with DLBP were the expressions of nociceptive neuropeptides and cytokines, particularly TNF-αdue to its strong association with pain outcomes. Activation of NF-κB signaling pathway, alterations in adrenoceptor expressions, and increase in reactive oxygen species (ROS) were also associated with DLBP through regulation of pro-inflammatory factors and pain-related neuropeptides. Current evidence converges to TNF-α, NF-κB signaling, and ROS-induced pro-inflammation. Major weaknesses in the current literature are the focus on degeneration without pain phenotyping, and lack of association of molecular findings with pain outcomes. PERSPECTIVE: This scoping review identified TNF-α, NF-κB signaling, and ROS-induced pro-inflammation as relevant mechanisms of human discogenic low back pain. Major weaknesses in the current literature are the focus on degeneration without pain phenotyping, and lack of association of molecular findings with pain outcomes.

Sleep characteristics and intervertebral disc degeneration risk: an observational and Mendelian randomization study

OBJECTIVES

Sleep disorders are considered a risk factor for aging and skeletal degeneration, but their impact on intervertebral disc degeneration (IDD) remains unclear. The aim of this study was to assess associations between sleep characteristics and IDD, and to identify potential causal relationships.

METHODS

Exposure factors included six unhealthy sleep characteristics: insomnia, short sleep duration (< 7 h), long sleep duration (≥ 9 h), evening chronotype, daytime sleepiness, and snoring. The primary outcomes included cervical disc degeneration (CDD) and lumbar disc degeneration (LDD). Firstly, we examined the associations between sleep characteristics and IDD risk in 368,348 participants from the UK Biobank using Cox proportional hazards model. Two-sample Mendelian randomization (MR) analyses were conducted to validate associations found in observational analyses, using genome-wide association data from the UK Biobank and FinnGen consortia.

RESULTS

During a median follow-up time of 13.8 years, a total of 1,637 cases of CDD and 7,654 cases of LDD were identified. Observational analyses found that almost all unhealthy sleep characteristics were associated with an elevated risk of IDD, except snoring. Conversely, the risk of IDD decreased linearly with an increasing number of healthy sleep characteristics. MR analyses supported a causal association between genetically determined insomnia and increased risk of LDD (OR 1.25 [1.07-1.47]), and between short sleep duration and increased risk of both IDD phenotypes (OR 5.41 [1.95-15.01] for CDD; OR 3.48 [1.76-6.89] for LDD). However, long sleep duration was causally associated with a reduced risk of LDD (OR 0.13 [0.03-0.53]), which contrasts with the observational findings.

CONCLUSION

We found associations between multiple sleep characteristics and IDD risk and confirmed that insomnia and short sleep duration increased IDD risk. Although more research is needed to confirm the underlying mechanisms, prioritizing interventions to improve sleep quality and ensure adequate sleep could help mitigate IDD.

Role of neurogenic inflammation in intervertebral disc degeneration

In healthy intervertebral discs (IVDs), nerves and blood vessels are present only in the outer annulus fibrosus, while in degenerative IVDs, a large amount of nerve and blood vessel tissue grows inward. Evidence supports that neurogenic inflammation produced by neuropeptides such as substance P and calcitonin gene related peptide released by the nociceptive nerve fibers innervating the IVDs plays a crucial role in the process of IVD degeneration. Recently, non-neuronal cells, including IVD cells and infiltrating immune cells, have emerged as important players in neurogenic inflammation. IVD cells and infiltrating immune cells express functional receptors for neuropeptides through which they receive signals from the nervous system. In return, IVD cells and immune cells produce neuropeptides and nerve growth factor, which stimulate nerve fibers. This communication generates a positive bidirectional feedback loop that can enhance the inflammatory response of the IVD. Recently emerging transient receptor potential channels have been recognized as contributors to neurogenic inflammation in the degenerative IVDs. These findings suggest that neurogenic inflammation involves complex pathophysiological interactions between sensory nerves and multiple cell types in the degenerative IVDs. Clarifying the mechanism of neurogenic inflammation in IVD degeneration may provide in-depth understanding of the pathology of discogenic low back pain.

Tree shrew as a new animal model for musculoskeletal disorders and aging

Intervertebral disc degeneration (IDD), osteoarthritis (OA), and osteoporosis (OP) are common musculoskeletal disorders (MSDs) with similar age-related risk factors, representing the leading causes of disability. However, successful therapeutic development and translation have been hampered by the lack of clinically-relevant animal models. In this study, we investigated the potential suitability of the tree shrew, a small mammal with a close genetic relationship to primates, as a new animal model for MSDs. Age-related spontaneous IDD in parallel with a gradual disappearance of notochordal cells were commonly observed in tree shrews upon skeletal maturity with no sex differences, while age-related osteoporotic changes including bone loss in the metaphyses were primarily presented in aged females, similar to observations in humans. Moreover, in the osteochondral defect model, tree shrew cartilage exhibited behavior similar to that of humans, characterized by a more restricted self-healing capacity compared to the rapid spontaneous healing of joint surfaces observed in rats. The induced OA model in tree shrews was highly efficient and reproducible, characterized by gradual deterioration of articular cartilage, recapitulating the human OA phenotype to some degree. Surgery-induced IDD models were successfully established in tree shrews, in which the lumbar spine instability model developed slow progressive disc degeneration with more similarity to the clinical state, whereas the needle puncture model led to the rapid development of IDD with more severe symptoms. Taken together, our findings pave the way for the development of the tree shrew as a new animal model for the study of MSDs and aging.

Combined single-cell RNA sequencing and mendelian randomization to identify biomarkers associated with necrotic apoptosis in intervertebral disc degeneration

BACKGROUND

Intervertebral disc degeneration (IDD) is associated with back pain; back pain is a world-wide contributor to poor quality of life, while necroptosis has the characteristics of necroptosis and apoptosis, however, its role in IDD is still unclear. Therefore, the aim of this study was to identify biomarkers associated with necroptosis in IDD.

PURPOSE

To explore biomarkers associated with necroptosis in IDD, reveal the pathogenesis of IDD, as well as provide new directions for the diagnosis and treatment of this disease.

STUDY DESIGN/SETTINGS

Retrospective cohort study. Our study employs scRNA-seq coupled with MR analysis to investigate the causal relationship between necroptosis and IDD, laying a foundational groundwork for unveiling the intricate pathogenic mechanisms of this condition.

METHODS

Data quality control and normalisation was executed in single-cell dataset, GSE205535. Then, different cell types were obtained by cell annotation through marker genes. Subsequently, chi-square test was employed to assess the distribution difference of different cell types between IDD and control to screen key cells. AUCell was applied to calculate necroptosis-related genes (NRGs) scores of all cell types, further key cells were divided into high and low NRGs groups according to the median AUC scores of different cell types. Afterwards, the differentially expressed genes (DEGs) within the 2 score groups were screened. Then, the genes that had causal relationship with IDD were selected as biomarkers by univariate and multivariate Mendelian randomization (MR) analysis. Finally, the expression of biomarkers in different cell types and pseudo-time analysis was analyzed separately.

RESULTS

In GSE205535, 16 different cell populations identified by UMAP cluster analysis were further annotated to 8 cell types using maker genes. Afterwards, 53 DEGs were screened between the high and low NRGs groups. In addition, 9 genes with causal relationship with IDD were obtained by univariate MR analysis, further multivariate MR analysis proved that NT5E and TMEM158 had a direct causal relationship with IDD, which were used as biomarkers in this study. This study not only found that the expression levels of NT5E and TMEM158 were higher in IDD group, but also found that fibrochondrocytes and inflammatory chondrocytes were the key cells of NT5E and TMEM158, respectively. In the end, the biomarkers had the same expression trend in the quasi-time series, and both of them from high to low and then increased.

CONCLUSIONS

NT5E and TMEM158, as biomarkers of necroptotic apoptotic IDD, were causally associated with IDD.

CLINICAL SIGNIFICANCE

The understanding of chondrocytes as key cells provides new perspectives for deeper elucidation of the pathogenesis of IDD, improved diagnostic methods, and the development of more effective treatments. These findings are expected to provide a more accurate and personalised approach to clinical diagnosis and treatment, thereby improving the prognosis and quality of life of patients with IDD.

Innovating intervertebral disc degeneration therapy: Harnessing the power of extracellular vesicles

Intervertebral disc degeneration is the leading cause of low back pain, imposing significant burdens on patients, societies, and economies. Advancements in regenerative medicine have spotlighted extracellular vesicles as promising nanoparticles for intervertebral disc degeneration treatment. Extracellular vesicles retain the potential of cell therapy and serve as carriers to deliver their cargo to target cells, thereby regulating cell activity. This review summarizes the biogenesis and molecular composition of extracellular vesicles and explores their therapeutic roles in intervertebral disc degeneration treatment through various mechanisms. These mechanisms include mitigating cell loss and senescence, delaying extracellular matrix degeneration, and modulating the inflammatory microenvironment. Additionally, it highlights recent efforts in engineering extracellular vesicles to enhance their targeting and therapeutic efficacy. The integration of extracellular vesicle-based acellular therapy is anticipated to drive significant advancements in disc regenerative medicine.

The translational potential of this article

Existing clinical treatment strategies often fail to effectively address the challenges associated with regenerating degenerated intervertebral discs. As a new regenerative medicine strategy, the extracellular vesicle strategy avoids the risks associated with cell transplantation and shows great promise in treating intervertebral disc degeneration by carrying therapeutic cargo. This review comprehensively examines the latest research, underlying mechanisms, and therapeutic potential of extracellular vesicles, offering a promising new strategy for intervertebral disc degeneration treatment.

Senolytics cocktail dasatinib and quercetin alleviate chondrocyte senescence and facet joint osteoarthritis in mice

BACKGROUND CONTEXT

Low back pain (LBP) is a pervasive issue, causing substantial economic burden and physical distress worldwide. Facet joint osteoarthritis (FJ OA) is believed to be a significant contributor to this problem. However, the precise role of chondrocyte senescence in FJ OA remains unclear, as does whether the clearance of chondrocyte senescence can alleviate the progression of FJ OA.

PURPOSE

The goal of this study was to understand the potential of Dasatinib (D) and Quercetin (Q) as a treatment to clear chondrocyte senescence during the progression of FJ OA.

STUDY DESIGN

We used a preclinical bipedal standing mice model with the administration of Dasatinib (D) (5 mg/kg) and Quercetin (Q) (50 mg/kg) after 10 weeks of bipedal standing.

MATERIALS AND METHODS

Human degenerative lumbar facet joint (LFJ) samples were obtained to investigate the relationship between chondrocyte cellular senescence and LFJ osteoarthritis (OA). Subsequently, we established an in vitro model of excessive mechanical stress on chondrocytes and an in vivo bipedal standing mice model to induce LFJ OA. IHC (immunohistochemistry) staining in vivo and SA-β-gal staining, qRT-PCR and Western blot analysis were applied to test the senolytic effect of the combination of Dasatinib (D) and Quercetin (Q). IHC staining and X-ray microscope were also performed to examine the contribution of D+Q to the anabolism in cartilage and subchondral bone recoupling. Immunofluorescence and Western blot analysis in vitro and IHC staining in vivo were conducted to assess the impact of D+Q on the regulation of the NF-κB pathway activation during chondrocyte senescence.

RESULTS

We observed that facet joint cartilage degeneration is associated with chondrocyte cellular senescence in both human and mouse degenerative samples. Following treatment with D+Q in vitro, cellular senescence was significantly reduced. Upon oral gavage administration of D+Q in the bipedal standing mice model, decreased cellular senescence and reversed chondrocyte anabolism were observed. Furthermore, administration of D+Q maintained subchondral bone remodeling homeostasis and potentially reversed the activation of the NF-κB pathway in chondrocytes of the lumbar facet joint.

CONCLUSIONS

In summary, our investigation unveiled a significant correlation between chondrocyte senescence and LFJOA. Treatment with the senolytic combination of D+Q in FJ OA yielded a notable reduction in chondrocyte senescence, along with a decrease in the release of SASP factors. Additionally, it facilitated the promotion of cartilage anabolism, maintenance of subchondral bone coupling, and amelioration of NF-κB pathway activation.

CLINICAL SIGNIFICANCE

Our outcomes revealed that D+Q, the renowned combination used for senolytic treatment, alleviate the progression of LFJ OA. The utilization of D+Q as a senolytic demonstrates a novel and promising alternative for LFJ OA treatment.

Cellular and molecular mechanisms underlying obesity in degenerative spine and joint diseases

Degenerative spine and joint diseases, including intervertebral disc degeneration (IDD), ossification of the spinal ligaments (OSL), and osteoarthritis (OA), are common musculoskeletal diseases that cause pain or disability to the patients. However, the pathogenesis of these musculoskeletal disorders is complex and has not been elucidated clearly to date. As a matter of fact, the spine and joints are not independent of other organs and tissues. Recently, accumulating evidence demonstrates the association between obesity and degenerative musculoskeletal diseases. Obesity is a common metabolic disease characterized by excessive adipose tissue or abnormal adipose distribution in the body. Excessive mechanical stress is regarded as a critical risk factor for obesity-related pathology. Additionally, obesity-related factors, mainly including lipid metabolism disorder, dysregulated pro-inflammatory adipokines and cytokines, are reported as plausible links between obesity and various human diseases. Importantly, these obesity-related factors are deeply involved in the regulation of cell phenotypes and cell fates, extracellular matrix (ECM) metabolism, and inflammation in the pathophysiological processes of degenerative spine and joint diseases. In this study, we systematically discuss the potential cellular and molecular mechanisms underlying obesity in these degenerative musculoskeletal diseases, and hope to provide novel insights for developing targeted therapeutic strategies.

Elevating Postinjection Stability in Silk Nanofibril Hydrogels to Prevent Intervertebral Disc Degeneration

Injectable hydrogels offer a minimally invasive approach to treating intervertebral disc degeneration, a prevalent condition that affects 90% of individuals and often leads to significant pain and disability. Despite being a critical yet often overlooked issue that could lead to suboptimal therapeutic outcomes, the mechanical integrity of these gels frequently diminishes postinjection due to the injection process itself. To address this challenge, our research developed a silk-nanofibril-based hydrogel enhanced through simple in situ polymerization of dopamine. The resulting hydrogel not only effectively preserved its modulus at over 1000 Pa postinjection, matching the mechanical properties of the nucleus pulposus, but also significantly enhanced its antioxidative properties to four times that of the original silk nanofibril-based hydrogel. Furthermore, both cell-based and animal studies substantiated that such a silk nanofibril-based hydrogel integrated with polydopamine exhibited significant therapeutic efficacy in the injectable treatment of intervertebral disc degeneration. Therefore, this work introduced a new perspective on the design of injectable hydrogels that could effectively address both the mechanical and biochemical challenges of degenerative disc diseases, providing a platform for subsequent therapeutic interventions.

Drug retention after intradiscal administration

Intradiscal drug delivery is a promising strategy for treating intervertebral disk degeneration (IVDD). Local degenerative processes and intrinsically low fluid exchange are likely to influence drug retention. Understanding their connection will enable the optimization of IVDD therapeutics. Release and retention of an inactive hydrophilic fluorine-19 labeled peptide (19F-P) as model for regenerative peptides was studied in a whole IVD culture model by measuring the 19F-NMR (nuclear magnetic resonance) signal in culture media and IVD tissue extracts. In another set-up, noninvasive near-infrared imaging was used to visualize IR-780, as hydrophobic small molecular drug model, retention upon injection into healthy and degenerative caudal IVDs in a rat model of disk degeneration. Furthermore, IR-780-loaded degradable polyester amide microspheres (PEAM) were injected into healthy and needle pricked degenerative IVDs, subcutaneously, and in knee joints with and without surgically-induced osteoarthritis (OA). Most 19F-P was released from the IVD after 7 days. IR-780 signal intensity declined over a 14-week period after bolus injection, without a difference between healthy and degenerative disks. IR-780 signal declined faster in the skin and knee joints compared to the IVDs. IR-780 delivery by PEAMs enhanced disk retention beyond 16 weeks. Moreover, in degenerated IVDs the IR-780 signal was higher over time than in healthy IVDs while no difference between OA and healthy joints was noted. We conclude that the clearance of peptides and hydrophobic small molecules from the IVD is relatively fast. These results illustrate that development of controlled release formulations should take into account the target anatomical location and local (patho)biology.

Association of vertebral fractures with worsening degenerative changes of the spine: a longitudinal study

Vertebral compression fractures (VFs) and spinal degeneration are both common causes of back pain, particularly in older adults. Previous cross-sectional studies have shown a potential association between these entities, but there is limited evidence on the role of VFs in spinal degeneration. In this longitudinal study, we evaluated the association between prevalent VFs and the subsequent progression of facet joint osteoarthritis (FJOA) and intervertebral disc height narrowing (DHN), using data from the Framingham Heart Study Offspring and Third Generation Multi-Detector Computed Tomography study. Summary indices representing the total burden of each spinal parameter (VFs, DHN, and FJOA) were calculated for each individual. We hypothesized that prevalent VFs are associated with worsening spinal degeneration. Three hundred and seventy (31%) of 1197 participants had a baseline (prevalent) VF. The change in summary index of DHN over the follow-up period was significantly higher in those with vs without prevalent VF (difference in change in DHN 0.38, 95% CI 0.18 to 0.59, p<.001), but the change in summary index of FJOA was similar between those with and without prevalent VF. However, once adjusted for age, sex, cohort, smoking status, BMI, and baseline DHN, the change in summary index of DHN did not differ by prevalent VF status. There was a modestly higher change in the FJOA summary index in those with prevalent VFs compared to those without in the fully adjusted model (difference in change in FJOA 0.62, 95% CI -0.01 to 1.24, p = .054), driven primarily by those with severe (grade 3) VF (difference in change in FJOA 4.48, 95% CI 1.99-6.97). Moreover, there was greater change in the summary index of FJOA with increasing severity of prevalent VF (linear trend p = .005). Beyond the established morbidity and mortality associated with VFs, our study suggests that VFs may also lead to worsening spine osteoarthritis.

The association of limited or painful spinal range of motion with lumbar disc degeneration: the back complaints in older adults (BACE) study

BACKGROUND

We currently lack clear definitions for structural and symptomatic spinal osteoarthritis (OA). To define spinal OA and create diagnostic criteria for this condition, it is necessary to determine the relationship between clinical signs and symptoms of back pain and radiographic features of OA. Notably, recent studies suggest a defining sign of spinal OA could be a limited or painful spinal range of motion (ROM). Therefore, our objective was to assess the association between restricted or painful active spinal ROM, and multilevel structural features of lumbar disc degeneration (LDD) (i.e., disc space narrowing, osteophytes) on radiographs.

METHODS

We used the baseline data from the'Back Complaints in Older Adults' (BACE) study. The association between a limited or painful active spinal ROM, and multilevel disc space narrowing or osteophytes was assessed using multivariable logistic regression adjusted for age, mean pain intensity in the previous week, sex, BMI, and the Fear Avoidance Belief Questionnaire score. Primary analyses were performed on imputed datasets.

RESULTS

We included 675 patients with a mean age of 66.52 years (SD 7.69). Limited latero-flexion (fingertip that at best reached halfway up the upper leg) was associated with increased odds of having multilevel osteophytes (OR 1.85; 95% CI: 1.13 to 3.01). However, a limited or painful ROM in other directions (i.e., rotation, ante-flexion) was not associated with multilevel osteophytes, and a limited or painful active ROM in any direction was found to have no association with multilevel disc space narrowing.

CONCLUSIONS

Our study indicates that a restricted ROM in latero-flexion could potentially be a defining sign in future definitions of symptomatic spinal OA. However, since our results partially differ from previous studies, further research is needed to explore the association between active ROM and LDD.

Single-cell sequencing reveals cellular heterogeneity of nucleus pulposus in intervertebral disc degeneration

The nucleus pulposus (NP) plays a vital role in intervertebral disc degeneration (IVDD). Previous studies have revealed cellular heterogeneity in NP tissue during IVDD progression. However, the cellular and molecular alterations of diverse cell clusters during IVDD remain to be fully elucidated. NP tissues were isolated from patients with different grades of IVDD undergoing discectomy, and then subjected to single-cell RNA sequencing (scRNA-seq). Cell subsets were identified based on unbiased clustering of gene expression profiles. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to determine the molecular features of diverse cell clusters. Monocle analysis was used to illustrate the differentiation trajectories of chondrocytes. Additionally, CellPhoneDB analysis revealed potential interactions between chondrocytes and other cells during IVDD. Based on the expression profiles of 47,610 individual cells, eight putative clusters including chondrocytes, endothelial cells, fibroblasts, macrophages, mural cells, osteoclasts, proliferating stromal cells and T cells were identified. The chondrocyte cluster was classified into three subsets, C1-C3, which were associated with stress-resistance, fibrosis and inflammatory responses, respectively. Pseudo-time trajectories suggested that chondrocytes gradually differentiated into fibroblasts during IVDD. Immune cells including cDC2s, macrophages and monocytes were identified. Further analysis showed that chondrocytes might communicate with immune cells via the MIF, TNFSF9, SPP1 and CCL4L2 signaling pathways. In addition, we found that invading endothelial cells might interact with chondrocytes through the COL4A1, CXCL12, VEGFA and SEMA3E signaling pathways. Our results reveal the cellular complexity and phenotypic characteristics of NP tissues at single-cell resolution, which will contribute to the in-depth investigation of preventative and regenerative strategies for IVDD.

Genome-wide meta-analysis conducted in three large biobanks expands the genetic landscape of lumbar disc herniations

Given that lumbar disc herniation (LDH) is a prevalent spinal condition that causes significant individual suffering and societal costs, the genetic basis of LDH has received relatively little research. Our aim is to increase understanding of the genetic factors influencing LDH. We perform a genome-wide association analysis (GWAS) of LDH in the FinnGen project and in Estonian and UK biobanks, followed by a genome-wide meta-analysis to combine the results. In the meta-analysis, we identify 41 loci that have not been associated with LDH in prior studies on top of the 23 known risk loci. We detect LDH-associated loci in the vicinity of genes related to inflammation, disc-related structures, and synaptic transmission. Overall, our research contributes to a deeper understanding of the genetic factors behind LDH, potentially paving the way for the development of new therapeutics, prevention methods, and treatments for symptomatic LDH in the future.

The Role of the Bone Morphogenetic Protein Antagonist Noggin in Nucleus Pulposus Intervertebral Disc Cells

Low back pain (LBP) is a significant global health issue, contributing to disability and socioeconomic burdens worldwide. The degeneration of the human intervertebral disc (IVD) is a critical factor in the pathogenesis of LBP. Recent studies have emphasized the significance of a specific set of genes and extracellular matrix (ECM) in IVD health. In particular, Noggin has emerged as a critical gene due to its high expression levels in healthy nucleus pulposus cells (NPCs) observed in our previous research. In this study, it was hypothesized that decreased Noggin expression in NPCs is associated with IVD degeneration and contributes to LBP development. A lentivirus-mediated RNAi was applied to knock down Noggin expression in primary NPCs from six human donors. The NPCs after transduction were evaluated through cell viability analysis, XTT assay, and cell apoptosis analyses. After two weeks, a colony formation assay was used to examine the anchor-independent growth ability of transduced cells. At the transcript level, anabolic and catabolic markers were quantified using RT-qPCR. The results demonstrated that lentivirus-mediated downregulation of Noggin significantly inhibited cell proliferation, reduced cell viability, and suppressed colony formation, while inducing apoptosis in human NPCs in vitro. Notably, it disrupted cellular anabolic processes and promoted catabolic activity in human NPCs post-transduction. Our findings indicated that the degeneration of human IVD is possibly related to decreased Noggin expression in NPCs. This research provides valuable insights into the role of Noggin in IVD homeostasis and its implications in LBP treatment.

Serine protease inhibitor E2 protects against cartilage tissue destruction and inflammation in osteoarthritis by targeting NF-κB signalling

OBJECTIVE

OA is a chronic disease characterized by cartilage degeneration and inflammation, with no approved disease-modifying drugs. This study aimed to identify pathogenic genes and elucidate their mechanism in OA.

METHODS

We systematically identified pathogenic genes combined sing-cell and bulk transcriptome profiles of cartilage tissues in OA. Adenovirus carrying the serpin peptidase inhibitor clade E member 2 (serpinE2) or exogenous serpinE2 was injected into monosodium iodoacetate (MIA)-induced OA-model rats. Histological analysis, immunohistochemistry and Alcian blue staining were performed. In vitro, immunofluorescence, quantitative real-time PCR (RT-qPCR), ELISA and western blot assays were performed.

RESULTS

serpinE2 exhibited elevated expression and hypomethylation, showing a positive association with collagen pathway activities in patients with OA. Silencing serpinE2 aggravated MIA-induced knee cartilage degeneration in OA-model rats. Conversely, the intra-articular injection of exogenous serpinE2 ameliorated articular cartilage degeneration, reduced pain-related behavioural responses and relieve synovitis in MIA-induced OA-model rats. Exogenous serpinE2 not only attenuated the elevation of NLRP3, IL-1β and caspase1 expression levels but also restored the reduction in cell viability induced by lipopolysaccharide (LPS) in chondrocytes. Mechanistically, we found that exogenous serpinE2 inhibited LPS-induced reactive oxygen species (ROS) release and NF-κB signalling activation.

CONCLUSIONS

serpinE2 plays a protective role in cartilage and synovium tissues, suggesting that serpinE2 gene transfer or molecules that upregulate serpinE2 expression could be therapeutic candidates for OA.

A Novel Superparamagnetic-Responsive Hydrogel Facilitates Disc Regeneration by Orchestrating Cell Recruitment, Proliferation, and Differentiation within Hostile Inflammatory Niche

In situ disc regeneration is a meticulously orchestrated process, which involves cell recruitment, proliferation and differentiation within a local inflammatory niche. Thus far, it remains a challenge to establish a multi-staged regulatory framework for coordinating these cellular events, therefore leading to unsatisfactory outcome. This study constructs a super paramagnetically-responsive cellular gel, incorporating superparamagnetic iron oxide nanoparticles (SPIONs) and aptamer-modified palladium-hydrogen nanozymes (PdH-Apt) into a double-network polyacrylamide/hyaluronic acid (PAAm/HA) hydrogel. The Aptamer DB67 within magnetic hydrogel (Mag-gel) showed a high affinity for disialoganglioside (GD2), a specific membrane ligand of nucleus pulposus stem cells (NPSCs), to precisely recruit them to the injury site. The Mag-gel exhibits remarkable sensitivity to a magnetic field (MF), which exerts tunable micro/nano-scale forces on recruited NPSCs and triggers cytoskeletal remodeling, consequently boosting cell expansion in the early stage. By altering the parameters of MF, the mechanical cues within the hydrogel facilitates differentiation of NPSCs into nucleus pulposus cells to restore disc structure in the later stage. Furthermore, the PdH nanozymes within the Mag-gel mitigate the harsh inflammatory microenvironment, favoring cell survival and disc regeneration. This study presents a remote and multi-staged strategy for chronologically regulating endogenous stem cell fate, supporting disc regeneration without invasive procedures.

PRDM1 promotes nucleus pulposus cell pyroptosis leading to intervertebral disc degeneration via activating CASP1 transcription

Intervertebral disc degeneration (IVDD) is a primary contributor to low back pain and poses a considerable burden to society. However, the molecular mechanisms underlying IVDD remain to be elucidated. PR/SET domain 1 (PRDM1) regulates cell proliferation, apoptosis, and inflammatory responses in various diseases. Despite these regulatory functions, the mechanism of action of PRDM1 in IVDD remains unexplored. In this study, we investigated the role and underlying mechanisms of action of PRDM1 in IVDD progression. The expression of PRDM1 in nucleus pulposus (NP) tissues and NP cells (NPCs) was assessed using western blotting, immunohistochemistry, and immunofluorescence. The effects of PRDM1 on IVDD progression were investigated in vitro and in vivo. Mechanistically, mRNA sequencing, chromatin immunoprecipitation, and dual-luciferase reporter assays were performed to confirm that PRDM1 triggered CASP1 transcription. Our study demonstrated for the first time that PRDM1 expression was substantially upregulated in degenerated NP tissues and NPCs. PRDM1 overexpression promoted NPCs pyroptosis by inhibiting mitophagy and exacerbating IVDD progression, whereas PRDM1 silencing exerted the opposite effect. Furthermore, PRDM1 activated CASP1 transcription, thereby promoting NPCs pyroptosis in vitro. Notably, CASP1 silencing reversed the effects of PRDM1 on the NPCs. To the best of our knowledge, this study is the first to demonstrate that PRDM1 silencing inhibits NPCs pyroptosis by repressing CASP1 transcription, which may be a promising new therapeutic target for IVDD.

The role of micronutrients and serum metabolites in intervertebral disk degeneration: insights from a Mendelian randomization study and mediation analysis

Background

Intervertebral disk degeneration (IVDD) is a complex degenerative skeletal condition, potentially influenced by micronutrients and serum metabolites in its etiology. However, the exact causal relationship between these factors and IVDD remains ambiguous.

Methods

The research employed a Two-Sample Mendelian Randomization (2SMR) analysis to thoroughly evaluate the causal relationship between 15 micronutrients (consisting of 7 minerals and 8 vitamins) as exposure variables, 1,091 blood metabolites, and 309 metabolite ratios as intermediary factors, and IVDD as the outcome. Additionally, reverse MR analysis and mediation analysis were carried out to validate the reliability of the results and explore the underlying mechanism by which micronutrients influence the risk of IVDD by regulating metabolites.

Results

Among the micronutrients examined, vitamin B12 exhibited a noteworthy negative correlation with the incidence of IVDD (OR: 0.752, 95% [CI]: 0.573-0.987, p = 0.040), indicating a potential reduction in IVDD risk with increased vitamin B12 consumption. Of the 1,091 blood metabolites and 309 metabolite ratios analyzed, 52 metabolites displayed significant associations with IVDD, primarily linked to amino acid, fatty acid, nucleotide, and sphingolipid metabolic pathways. Mediation analysis identified 4-acetaminophen sulfate as a potential mediator in the protective effect of vitamin B12 against IVDD.

Conclusion

This study has shown that vitamin B12 may reduce the risk of IVDD and has identified 52 serum metabolites that are associated with IVDD. Furthermore, it proposes that 4-acetaminophen sulfate could serve as a potential mechanism by which vitamin B12 exerts its inhibitory effects on IVDD.

Angiogenesis unveiled: Insights into its role and mechanisms in cartilage injury

Osteoarthritis (OA) commonly results in compromised mobility and disability, thereby imposing a significant burden on healthcare systems. Cartilage injury is a prevalent pathological manifestation in OA and constitutes a central focus for the development of treatment strategies. Despite the considerable number of studies aimed at delaying this degenerative process, their outcomes remain unvalidated in preclinical settings. Recently, therapeutic strategies focused on angiogenesis have attracted the growing interest from researchers. Thus, we conducted a comprehensive literature review to elucidate the current progress in research and pinpoint research gaps in this domain. Additionally, it provides theoretical guidance for future research endeavors and the development of treatment strategies.

Unveiling the future: Bibliometric analysis on the application of nanomaterials in osteoarthritis (2006-2023)

Background

As the population ages, the socio-economic impact of osteoarthritis (OA) is becoming increasingly significant. In recent years, there has been a growing focus on the design and development of nanomaterials for diagnosing and treating OA. This study aims to comprehensively evaluate the current status and trends in the application of nanomaterials in OA through bibliometric analysis and provide a review.

Methods

Studies on nanomaterials and OA were sourced from the Web of Science Core Collection (WoSCC) database, with relevant articles selected based on predefined inclusion criteria. Quantitative and visual analyses of the included publications were conducted using tools such as VOSviewer, and GraphPad Prism 9.5.0.

Results

A total of 532 publications were included in this study. The number of annual publications has increased steadily from 2006 to 2023. China, the United States, and South Korea are the leading countries in this field. Shanghai Jiao Tong University and Li Zheng are recognized as the most influential institutions and authors, respectively. Biomaterials is the most frequently published and cited journal. Current research primarily focuses on drug delivery and the anti-inflammatory and antioxidant properties of nanomaterials. Recent research hotspots include mesoporous silica nanoparticles, electrostatic interaction, and injectable hydrogels.

Conclusion

In this study, we summarised the annual publication trends and identified the most influential countries, institutions, authors, journals, and current research and development trends in the application of nanomaterials for OA.

A novel spherical GelMA-HAMA hydrogel encapsulating APET×2 polypeptide and CFIm25-targeting sgRNA for immune microenvironment modulation and nucleus pulposus regeneration in intervertebral discs

METHODS

Single-cell transcriptomics and high-throughput transcriptomics were used to screen factors significantly correlated with intervertebral disc degeneration (IDD). Expression changes of CFIm25 were determined via RT-qPCR and Western blot. NP cells were isolated from mouse intervertebral discs and induced to degrade with TNF-α and IL-1β. CFIm25 was knocked out using CRISPR-Cas9, and CFIm25 knockout and overexpressing nucleus pulposus (NP) cell lines were generated through lentiviral transfection. Proteoglycan expression, protein expression, inflammatory factor expression, cell viability, proliferation, migration, gene expression, and protein expression were analyzed using various assays (alcian blue staining, immunofluorescence, ELISA, CCK-8, EDU labeling, transwell migration, scratch assay, RT-qPCR, Western blot). The GelMA-HAMA hydrogel loaded with APET×2 polypeptide and sgRNA was designed, and its effects on NP regeneration were assessed through in vitro and mouse model experiments. The progression of IDD in mice was evaluated using X-ray, H&E staining, and Safranin O-Fast Green staining. Immunohistochemistry was performed to determine protein expression in NP tissue. Proteomic analysis combined with in vitro and in vivo experiments was conducted to elucidate the mechanisms of hydrogel action.

RESULTS

CFIm25 was upregulated in IDD NP tissue and significantly correlated with disease progression. Inhibition of CFIm25 improved NP cell degeneration, enhanced cell proliferation, and migration. The hydrogel effectively knocked down CFIm25 expression, improved NP cell degeneration, promoted cell proliferation and migration, and mitigated IDD progression in a mouse model. The hydrogel inhibited inflammatory factor expression (IL-6, iNOS, IL-1β, TNF-α) by targeting the p38/NF-κB signaling pathway, increased collagen COLII and proteoglycan Aggrecan expression, and suppressed NP degeneration-related factors (COX-2, MMP-3).

CONCLUSION

The study highlighted the crucial role of CFIm25 in IDD and introduced a promising therapeutic strategy using a porous spherical GelMA-HAMA hydrogel loaded with APET×2 polypeptide and sgRNA. This innovative approach offers new possibilities for treating degenerated intervertebral discs.

Diagnostic models to predict structural spinal osteoarthritis on lumbar radiographs in older adults with back pain: Development and internal validation

Objective

It is difficult for health care providers to diagnose structural spinal osteoarthritis (OA), because current guidelines recommend against imaging in patients with back pain. Therefore, the aim of this study was to develop and internally validate multivariable diagnostic prediction models based on a set of clinical and demographic features to be used for the diagnosis of structural spinal OA on lumbar radiographs in older patients with back pain.

Design

Three diagnostic prediction models, for structural spinal OA on lumbar radiographs (i.e. multilevel osteophytes, multilevel disc space narrowing (DSN), and both combined), were developed and internally validated in the 'Back Complaints in Older Adults' (BACE) cohort (N ​= ​669). Model performance (i.e. overall performance, discrimination and calibration) and clinical utility (i.e. decision curve analysis) were assessed. Internal validation was performed by bootstrapping.

Results

Mean age of the cohort was 66.9 years (±7.6 years) and 59% were female. All three models included age, gender, back pain duration and duration of spinal morning stiffness as predictors. The combined model additionally included restricted lateral flexion and spinal morning stiffness severity, and exhibited the best model performance (optimism adjusted c-statistic 0.661; good calibration with intercept -0.030 and slope of 0.886) and acceptable clinical utility. The other models showed suboptimal discrimination, good calibration and acceptable decision curves.

Conclusion

All three models for structural spinal OA displayed lesuboptimal discrimination and need improvement. However, these internally validated models have potential to inform primary care clinicians about a patient with risk of having structural spinal OA on lumbar radiographs. External validation before implementation in clinical care is recommended.

The role of sirtuins in intervertebral disc degeneration: Mechanisms and therapeutic potential

Intervertebral disc degeneration (IDD) is one of the main causes of low back pain, which affects the patients' quality of life and health and imposes a significant socioeconomic burden. Despite great efforts made by researchers to understand the pathogenesis of IDD, effective strategies for preventing and treating this disease remain very limited. Sirtuins are a highly conserved family of (NAD+)-dependent deacetylases in mammals that are involved in a variety of metabolic processes in vivo. In recent years, sirtuins have attracted much attention owing to their regulatory roles in IDD on physiological activities such as inflammation, apoptosis, autophagy, aging, oxidative stress, and mitochondrial function. At the same time, many studies have explored the therapeutic effects of sirtuins-targeting activators or micro-RNA in IDD. This review summarizes the molecular pathways of sirtuins involved in IDD, and summarizes the therapeutic role of activators or micro-RNA targeting Sirtuins in IDD, as well as the current limitations and challenges, with a view to provide possible solutions for the treatment of IDD.

Dedifferentiation-like reprogramming of degenerative nucleus pulposus cells into notochordal-like cells by defined factors

The extensive degeneration of functional somatic cells and the depletion of endogenous stem/progenitor populations present significant challenges to tissue regeneration in degenerative diseases. Currently, a cellular reprogramming approach enabling directly generating corresponding progenitor populations from degenerative somatic cells remains elusive. The present study focused on intervertebral disc degeneration (IVDD) and identified a three-factor combination (OCT4, FOXA2, TBXT [OFT]) that could induce the dedifferentiation-like reprogramming of degenerative nucleus pulposus cells (dNPCs) toward induced notochordal-like cells (iNCs). Single-cell transcriptomics dissected the transitions of cell identity during reprogramming. Further, OCT4 was found to directly interact with bromodomain PHD-finger transcription factor to remodel the chromatin during the early phases, which was crucial for initiating this dedifferentiation-like reprogramming. In rat models, intradiscal injection of adeno-associated virus carrying OFT generated iNCs from in situ dNPCs and reversed IVDD. These results collectively present a proof-of-concept for dedifferentiation-like reprogramming of degenerated somatic cells into corresponding progenitors through the development of a factor-based strategy, providing a promising approach for regeneration in degenerative disc diseases.

Exploration of the correlation between facet joints cross-sectional area asymmetry and cervical disc herniation

PURPOSE

To evaluate the association between facet joints cross-sectional area asymmetry (FCAA) and cervical intervertebral disc herniation (CDH).

METHODS

Overall, we retrospectively recruited 390 consecutive patients with CDH who underwent surgical treatment at our institution and 50 normal participants. Clinical variables and radiological findings related to CDH were collected.

RESULTS

Patients with CDH were more likely to have a higher absolute value of the facet asymmetry factor (FAF) (p  < .001), in which the FAF value of the left group was significantly higher than the other groups (p  < .001) and the right group was lower than the central group (p  < .001). 9.62% (C3/4), 12.19% (C4/5), 8.70% (C5/6), and 8.14% (C6/7) were determined as cutoff values for each variable that maximized sensitivity and specificity. Furthermore, multivariate analysis showed that cross-sectional area asymmetry of the facet joint (FCAA) was an independent risk factor for the occurrence of CDH. Also, the Chi-square test showed a significant difference in the distribution of the degeneration classification of the disc between the facet-degenerated group and the nondegenerated group at C5/6 (p = 0.026) and C6/7 (p = 0.005) in the facet asymmetry (FA) group.

CONCLUSIONS

FCAA is evaluated as an independent risk factor for CDH and associated with the orientation of disc herniation. And facet joint orientation may also play a role in cervical spine degeneration rather than facet joint tropism.

Homoplantaginin alleviates intervertebral disc degeneration by blocking the NF-κB/MAPK pathways via binding to TAK1

Intervertebral disc degeneration (IVDD) is a common degenerative disease which is closely related to low back pain (LBP) and brings huge economic and social burdens. In this study, we explored the therapeutic effects of Homoplantaginin (Hom) for IVDD due to its convincing anti-inflammatory and antioxidant functions. TNF-α was used to simulate the inflammatory environment for nucleus pulposus (NP) cells in vitro. We verified that Hom could alleviate the TNF-α-induced inflammation and disturbance of ECM homeostasis through blocking the NF-κB/MAPK signaling pathways. Subsequently, we screened the binding targets of Hom and confirmed that Hom could directly bind to TAK1 and inhibit its phosphorylation to down-regulate the inflammation-related pathways. The therapeutic effects of Hom on IVDD were further validated through a needle puncture rat model in vivo. Overall, Hom was a promising small molecule for IVDD early intervention, possessing huge clinical translational value.