Injectable exosome-functionalized extracellular matrix hydrogel for metabolism balance and pyroptosis regulation in intervertebral disc degeneration

Exosomes derived from MSCs exposed to hypoxic and inflammatory environments slow intervertebral disc degeneration by alleviating the senescence of nucleus pulposus cells through epigenetic modifications

Intervertebral disc degeneration (IDD) is the leading cause of low back pain, which places heavy burdens on society and individuals. Surgical intervention is the conventional therapy for IDD, but patients who undergo surgery face relatively high risks of recurrence and complications. Therefore, a relatively less invasive and efficient treatment for IDD is urgently needed. In this study, we constructed a novel nanobiomaterial, named Hi-Exos, to slow IDD. Hi-Exos are exosomes derived from mesenchymal stem cells exposed to hypoxic and inflammatory environments. Hi-Exos could relieve the senescence of nucleus pulposus cells and slow IDD through an epigenetic modification mechanism by introducing the epigenetic factor miR-221-3p into senescent nucleus pulposus cells to reduce DDIT4 expression and inhibit the activation of NF-κB signalling pathway. This study provided a novel strategy for IDD treatment involving the use of Hi-Exos to deliver miR-221-3p to reduce the senescence of nucleus pulposus cells and repair IDD via epigenetic modifications.

Self-healing injectable multifunctional hydrogels for intervertebral disc disease

Intervertebral disc degeneration (IVDD) is increasingly prevalent in aging societies and poses a significant health challenge. Due to the limited blood supply to the disc, oral medications and systemic treatments are often ineffective. Consequently, localized injection therapies, which deliver therapeutic agents directly to the degenerated disc, have emerged as more efficient. Self-healing injectable hydrogels are particularly promising due to their potential for minimally invasive delivery, precise implantation, and targeted drug release into hard-to-reach tissue sites, including those requiring prolonged healing. Their dynamic viscoelastic properties accurately replicate the mechanical environment of the natural nucleus pulposus, providing cells with an adaptive biomimetic microenvironment. This review will initially discuss the anatomy and pathophysiology of intervertebral discs, current treatments, and their limitations. Subsequently, we conduct bibliometric analysis to explore the research hotspots and trends in applying injectable hydrogel technology to treat IVDD. It will then explore the promising features of injectable hydrogels in biomedical applications such as drug, protein, cells and gene delivery, tissue engineering and regenerative medicine. We discuss the construction mechanisms of injectable hydrogels via physical interactions, chemical and biological crosslinkers, and discuss the selection of biomaterials and fabrication methods for developing novel hydrogels for IVD tissue engineering. The article concludes with future perspectives on the application of injectable hydrogels in this field.

Baicalein-loaded porous silk fibroin microspheres modulate the senescence of nucleus pulposus cells through the NF-κB signaling pathway

Intervertebral disc degeneration (IVDD), an age-associated degenerative condition, significantly contributes to low back pain, thereby adversely affecting individual health and quality of life, while also imposing a substantial societal burden. Baicalein, a natural flavonoid derived from Scutellaria baicalensis Georgi, demonstrates a range of pharmacological activities, including antioxidant, anti-inflammatory, anti-tumor, and antibacterial properties. This positions it as a promising candidate for the treatment of IVDD through intradiscal drug delivery. However, local degenerative processes and the inherently low fluid exchange within the intervertebral disk are likely to affect drug retention. In this study, we developed baicalein-loaded porous silk fibroin microspheres to extend the drug release profile. Baicalein-loaded porous silk fibroin microspheres were prepared by electrostatic spraying. Subsequent characterization and evaluation of their intrinsic properties were conducted using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy(TEM), and fourier transform infrared spectroscopy (FTIR). The findings of our study demonstrated that baicalein-loaded porous silk fibroin microspheres exhibited a sustained drug release profile. Consequently, these microspheres effectively inhibited the senescence of nucleus pulposus cells (NPCs), which induced by Tert-butyl hydroperoxide (TBHP). Mechanistic investigation utilizing transcriptome sequencing revealed that the NF-κB signaling pathway is involved in the effects of baicalein-loaded porous silk fibroin microspheres. Furthermore, our findings demonstrated that the microspheres exhibited excellent biocompatibility in rats subcutaneous implantation model. Collectively, we developed a promising biomaterial for the treatment of IVDD, warranting further systematic preclinical investigation.

SOX4 accelerates intervertebral disc degeneration via EZH2/NRF2 pathway in response to mitochondrial ROS-dependent NLRP3 inflammasome activation in nucleus pulposus cells

OBJECTIVE

The transcription factor SRY-related HMG-box 4 (SOX4) has been implicated in intervertebral disc diseases. This study aimed to investigate the role of SOX4 in intervertebral disc degeneration (IDD) and explore the underlying molecular mechanisms.

METHODS

We established an IDD rat model via surgery and analyzed SOX4 expression using qRT-PCR and Western blotting. Histological evaluation, immunohistochemistry, and Safranin O staining assessed IDD progression. In vitro, an IDD cellular model was constructed using IL-1β-stimulated nucleus pulposus (NP) cells. SOX4 knockdown and overexpression experiments in NP cells examined SOX4 effects on ECM degradation, NLRP3-mediated pyroptosis, and mitochondrial ROS-dependent NLRP3 inflammasome activation. The involvement of the EZH2/NRF2 pathway in SOX4-mediated NLRP3 activation was also examined.

RESULTS

SOX4 expression was significantly increased in IDD rats and promoted IDD progression. Knockdown of SOX4 inhibited ECM degradation and NLRP3-mediated pyroptosis in NP cells. In vitro experiments showed that SOX4 promoted ECM degradation by upregulating MMPs and ADAMTS-5 expression, and suppressed collagen II and aggrecan synthesis. SOX4 knockdown inhibited NLRP3-mediated pyroptosis, while overexpression accelerated it in NP cells. Additionally, SOX4 was found to exacerbate mitochondrial ROS-dependent NLRP3 inflammasome activation in NP cells. Further investigation revealed that SOX4 enhanced NLRP3 inflammasome activation by upregulating EZH2 expression and modulating the EZH2/NRF2 pathway, with EZH2 inhibition attenuating SOX4-induced NLRP3 activation.

CONCLUSION

Our findings suggest that SOX4 accelerates IDD progression by promoting NLRP3 inflammasome activation via modulating the EZH2/NRF2 pathway, leading to NP cell pyroptosis and ECM degradation. Targeting SOX4 may represent a potential therapeutic strategy for treating IDD.

Designing hydrogel for application in spinal surgery

Spinal diseases and injuries are prevalent in clinical settings and impose a substantial burden on healthcare systems. Current treatments for spinal diseases are predominantly limited to surgical interventions, drug injections, and conservative treatments. Generally, these treatment modalities have limited or no long-term benefits. Hydrogel-based treatments have emerged as potentially powerful paradigms for improving therapeutic outcomes and the quality of life of patients. Hydrogels can be injected into target sites, including the epidural, intraspinal, and nucleus pulposus spaces, in a minimally invasive manner and fill defects to provide mechanical support. Hydrogels can be designed for the localized and controlled delivery of pharmacological agents to enhance therapeutic effects and reduce adverse reactions. Hydrogels can act as structural supports for transplanted cells to improve cell survival, proliferation, and differentiation, as well as integration into adjacent host tissues. In this review, we summarize recent advances in the design of hydrogels for the treatment of spinal diseases and injuries commonly found in clinical settings, including intervertebral disc degeneration, spinal cord injury, and dural membrane injury. We introduce the design considerations for different hydrogel systems, including precursor polymers and crosslinking mechanisms. Herein, we discuss the therapeutic outcomes of these hydrogels in terms of providing mechanical support, delivering cells/bioactive agents, regulating local inflammation, and promoting tissue regeneration and functional recovery.

3-D Sustained-Release Culture Carrier Alleviates Rat Intervertebral Disc Degeneration by Targeting STING in Transplanted Skeletal Stem Cells

The hypoxic and high-pressure microenvironment of the intervertebral discs poses a major challenge to the survival and therapeutic efficiency of exogenous stem cells. Therefore, improving the utilization efficiency and therapeutic effect of exogenous stem cells to delay intervertebral disc degeneration (IVDD) is of great importance. Here, hypoxic induction studies are conducted in vivo and in vitro using rat costal cartilage-derived skeletal stem cells (SSCs) and find that hypoxia activates the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)/stimulator of interferon genes (STING) signaling pathway and increased reactive oxygen species (ROS) accumulation, triggering ferroptosis in SSCs through hypoxia-inducible factor-1 alpha-dependent mitophagy. Progressive hypoxia preconditioning reduce STING expression and ROS accumulation, inducing SSCs differentiation into nucleus pulposus-like cells via the Wnt signaling pathway. Considering this, a 3-D sustained-release culture carrier is generated by mixing SSCs with methacrylated hyaluronic acid and polydopamine nanoparticles coated with the STING inhibitor C-176 and evaluated its inhibitory effect on IVDD. This carrier is demonstrated to inhibit the cGAS/STING pathway and prevent ROS accumulation by continuously releasing C-176-coated polydopamine nanoparticles, thereby reducing ferroptosis, promoting differentiation, and ultimately attenuating IVDD, suggesting its potential as a novel treatment strategy.

Electroacupuncture attenuates intervertebral disc degeneration by upregulating aquaporins via the cAMP/PKA pathway

BACKGROUND

Intervertebral disc degeneration (IVDD) is characterized by a decrease in extracellular matrix (ECM) and water loss, which is a major cause of low back pain (LBP). Electroacupuncture (EA) has long been used to relieve LBP in IVDD. To investigate whether EA can upregulate aquaporins (AQPs) in IVDD via the cAMP/PKA pathway in a rabbit model of disc degeneration.

METHODS

A homemade loading device was adapted to trigger a disc degeneration model. After 28 days, EA treatment was performed. Magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI), and diffusion tensor imaging (DTI) were performed to evaluate AQP content and water diffusion. AQP protein expression in the slices was observed by Western blot and immunofluorescence (IF) staining. The pathology of the intervertebral discs was determined by staining. cAMP and PKA levels were examined using ELISA, and the expression of AQP genes as well as the cAMP/PKA pathway and its related molecules were examined using quantitative reverse transcription-PCR (qRT-PCR) and Western blot analysis.

RESULTS

The EA intervention reduced MRI Pfirrmann scores, fractional anisotropy (FA), and apparent diffusion coefficient (ADC) values. EA can upregulate the expression of AQP1 and AQP3, thereby improving the pathological morphology of the nucleus pulposus (NP) and the cartilage endplate of the intervertebral disc. cAMP and PKA levels were significantly increased after EA intervention in rabbits with IVDD. EA intervention can partially improve the expression of related molecules in the cAMP/PKA pathway, but H-89 reverses the effect of EA.

CONCLUSION

EA can attenuate intervertebral disc degeneration by regulating AQP expression, a process that may be mediated by the cAMP/PKA pathway.

Senescent cartilage endplate stem cells-derived exosomes induce oxidative stress injury in nucleus pulposus cells and aggravate intervertebral disc degeneration by regulating FOXO3

Intervertebral disc degeneration (IVDD) is the leading cause of low back pain and associated disability worldwide. The cartilage endplate (CEP) is a critical structure in maintaining the homeostasis of the intervertebral disc, by exosomes (Exos)-mediated intracellular communication between cartilage endplate stem cells (CESCs) and nucleus pulposus cells (NPCs). However, whether the senescence of CESCs influences the functionality of CESCs-derived Exos (CESCs-Exos) and participates in the progress of IVDD remains unclear. In this study, we explored the role and mechanism of the Exos-based intracellular communication between senescent CESCs and NPCs in IVDD. CESCs isolated from aged individuals (S-CESCs) exhibited high levels of senescence compared with CESCs isolated from young individuals (Y-CESCs). Exos from Y-CESCs (Y-Exos) and from S-CESCs (S-Exos) were extracted and identified. Surprisingly, we found that S-Exos lost the therapeutic effects as the Y-Exos exhibited in mitigating IVDD, and even aggravated IVDD by inducing oxidative stress injury in NPCs. MicroRNA-sequencing revealed significant upregulation of miR-29b-3p expression in S-Exos. Through microRNA target prediction, dual luciferase assays, RNA-sequencing, lentivirus-mediated overexpression and suppression, we demonstrated that miR-29b-3p regulates the expression of FOXO3 and downstream antioxidant enzymes to induce oxidative stress injury in NPCs. In vivo experiments further verified that countering miR-29b-3p by antagomir reversed the detrimental effects of S-Exos in exacerbating IVDD. This work elucidates the role and mechanism of senescent CESCs in disrupting redox homeostasis in the nucleus pulposus and exacerbating IVDD by Exos-mediated intracellular communication and offers an experimental foundation for the selection of proper CESCs-Exos to obtain better therapeutic effects in IVDD.

Extracellular Vesicles for Disease Treatment

Traditional drug therapies suffer from problems such as easy drug degradation, side effects, and treatment resistance. Traditional disease diagnosis also suffers from high error rates and late diagnosis. Extracellular vesicles (EVs) are nanoscale spherical lipid bilayer vesicles secreted by cells that carry various biologically active components and are integral to intercellular communication. EVs can be found in different body fluids and may reflect the state of the parental cells, making them ideal noninvasive biomarkers for disease-specific diagnosis. The multifaceted characteristics of EVs render them optimal candidates for drug delivery vehicles, with evidence suggesting their efficacy in the treatment of various ailments. However, poor stability and easy degradation of natural EVs have affected their applications. To solve the problems of poor stability and easy degradation of natural EVs, they can be engineered and modified to obtain more stable and multifunctional EVs. In this study, we review the shortcomings of traditional drug delivery methods and describe how to modify EVs to form engineered EVs to improve their utilization. An innovative stimulus-responsive drug delivery system for EVs has also been proposed. We also summarize the current applications and research status of EVs in the diagnosis and treatment of different systemic diseases, and look forward to future research directions, providing research ideas for scholars.

Human Umbilical Cord Mesenchymal Stem Cells-Derived Exosomes Attenuates Experimental Periodontitis in Mice Partly by Delivering miRNAs

Introduction

Periodontitis is the most common non-communicable disease in humans. The main challenge in the treatment of periodontitis is to effectively control periodontal inflammation and promote tissue repair. Human umbilical cord mesenchymal stem cells-derived exosomes (hucMSCs-exo) have been reported to modulate inflammatory responses and promote tissue repairment mainly through miRNAs in several diseases. However, the effect of hucMSCs-exo on periodontitis remains unknown. In this study, we hypothesized that hucMSCs-exo could inhibit bone destruction in periodontitis mice.

Methods

In this study, we constructed and characterized the exo@H drug delivery platform. Lipopolysaccharide was used to construct an inflammatory microenvironment in vitro to detect MC3T3-E1 cells proliferation and bone regeneration capacity. Ligation induced to construct an experimental periodontitis mouse model. The distance of the cement-enamel junction (CEJ) to the alveolar bone crest (ABC) was measured for bone resorption evaluation. Hematoxylin-eosin (H&E) staining and Tartrate resistant acid phosphatase (TRAP) staining were used to observe periodontal tissue changes. MicroRNA (miRNA) sequencing was used to detect differential genes and for bioinformatics analysis. Real-time quantitative polymerase chain reaction (qRT-PCR). WB assay and dual luciferase assay were used to further validate the screened differentially expressed miRNAs and the targeted binding relationship with the corresponding target genes.

Results

We found that lyophilized hucMSCs-exo promoted the proliferation and osteogenic differentiation of MC3T3-E1 cells, and showed more significant proliferative and osteogenic differentiation abilities in combination with the hydrogel (P < 0.05). Using periodontitis mice, bone resorption evaluation revealed a significant reduction in alveolar bone resorption in the exo@H group compared to the hydrogel group (P < 0.01), and exo@H was able to reduce the inflammatory response of periodontal tissues and the number of osteoclasts on the surface of the alveolar bone compared to the hydrogel group. Moreover, 59 miRNAs were upregulated, such as let-7f-5p and miR-203-3p, which positively targeted IL-13 and Nit2, respectively.

Discussion

These results suggest that exo@H provides protection against periodontitis partly by delivering miRNAs to periodontal tissue. Our results confirm the feasibility of the exo@H delivery platform we constructed and the effectiveness of its use for periodontitis treatment, and this study provides a promising approach for the treatment of periodontitis via miRNA.

End Plate Chondrocyte-Derived Exosomal miR-133a-3p Alleviates Intervertebral Disc Degeneration by Targeting the NF-κB Signaling Pathway through the miR-133a-3p/MAML1 Axis

Chondrocyte-derived exosomes have shown efficacy in differentiating osteoarthritis-affected cartilage. Intervertebral disc degeneration (IVDD) and osteoarthritis often affect facet joints of the spine and show common epidemiological and pathophysiological characteristics. However, the potential of chondrocyte-derived exosomes for treating IVDD remains unclear. The present study aimed to confirm the effect of end plate chondrocyte-derived exosomes (EPC-Exo) on IVDD and elucidate the underlying mechanism. EPC-Exos were isolated and identified by ultracentrifugation, Western blotting, electron microscopy, and nanoparticle tracking analysis. In the in vitro, EPC-Exo uptake by nucleus pulposus (NP) cells reduced cell death by blocking the nuclear factor-κB (NF-κB) signaling pathway. In the in vivo study, EPC-Exos injected into rat intervertebral discs mitigated lipopolysaccharide-induced IVDD, as revealed by a decreased loss of disc height and improved magnetic resonance imaging findings and histological scores. Bioinformatics and sequencing analyses indicated that EPC-Exos alleviated IVDD through the miR-133a-3p/MAML1 axis. The present study suggests that EPC-Exos reduced IVDD incidence via the miR-133a-3p/MAML1 axis-mediated suppression of NF-κB signaling, which prevented the pyroptosis of NP cells.

Inhibition of ERK1/2 mediated activation of Drp1 alleviates intervertebral disc degeneration via suppressing pyroptosis and apoptosis in nucleus pulposus cells

Objective

Dynamin-related protein 1 (Drp1) plays a crucial role in various inflammatory and degenerative diseases, yet its involvement in intervertebral disc degeneration (IVDD) remains poorly understood. This study aims to elucidate the mechanism by which Drp1 contributes to IVDD and to identify the efficacy of the Drp1 inhibitor Mdivi-1 on IVDD.

Methods

Tert-butyl hydroperoxide (TBHP) is utilized to induce an oxidative stress microenvironment in vitro. In vivo, IVDD model is constructed in 8-week old rats through puncture operation. The therapeutic effect of Mdivi-1 is evaluated through X-ray, MRI and histological analysis. A comprehensive set of experiments, including single-cell sequencing analysis, western blot, flow cytometry and immunofluorescence staining, are conducted to investigate the role and underlying mechanisms of Drp1 in vitro.

Results

Our study demonstrates that the expression of Drp1 and phosphorylated Drp1 (p-Drp1) are up-regulated in degenerative nucleus pulposus cells (NPCs), which are accompanied with increased pyroptosis and apoptosis. In vivo, both si-Drp1-mediated Drp1 knockdown and the pharmacological inhibitor Mdivi-1 alleviate puncture-induced IVDD in rats. In vitro, si-Drp1 or Mdivi-1 inhibits mitochondria-dependent apoptosis and pyroptosis triggered by TBHP. Mechanistically, Mdivi-1 reduces p-Drp1 levels, inhibits excessive mitochondrial fission, and mitigates mitochondrial dysfunction. Drp1 phosphorylation-based Drp1 mitochondrial translocation and subsequent apoptosis and pyroptosis are regulated by ERK1/2 phosphorylation in NPCs under oxidative stress condition.

Conclusion

This study highlights the involvement of Drp1 in the pathological progression of degenerative NPCs in IVDD, which is regulated by ERK1/2. Pharmacological inhibition of Drp1 with Mdivi-1 protects NPCs by promoting mitochondrial function and attenuating apoptosis and pyroptosis. These findings suggest that Mdivi-1 is a promising therapeutic candidate for IVDD treatment.

Translational Potential

By offering experimental evidence on the role and mechanism of Drp1 in IVDD, this study underscores the potential of Mdivi-1 as a therapeutic strategy for IVDD.

Adipose Tissue-Derived Exosome Maintains Metabolic Balance of Extracellular Matrix in Rat Nucleus Pulposus Cells

Purpose

This study aimed to investigate the protective effect of adipose tissue-derived exosomes (AT-Exo) on rat nucleus pulposus cells (NPCs).

Methods

Ultracentrifugation was used to extract exosomes from rat adipose tissue. Transmission electron microscopy (TEM), Western blot, and nanoparticle tracking analysis (NTA) were used to characterize the exosomes. Tert-butyl hydrogen peroxide (TBHP) was used to induce apoptosis of rat NPCs. Cell viability was determined by CCK-8 assay. AT-Exo was administered to investigate its effect on rat NPCs using Western blot and immunofluorescence staining.

Results

AT-Exo was successfully extracted and characterized by NTA, TEM, and Western blots. Uptake assay showed that AT-Exo can be taken up by the NPCs. TBHP (60 μM) resulted in decreased cell viability and increased apoptosis of NPCs. Interestingly, AT-Exo protected NPCs against TBHP, indicated by increased cell viability, decreased apoptosis, upregulated Aggrecan and type II collagen deposition, and downregulated matrix metalloproteinase 3/13.

Conclusion

In summary, rat adipose tissue-derived exosomes can increase the levels of Aggrecan, type II collagen, and Bcl2, and decrease the levels of matrix metalloproteinase 3/13, cleaved caspase3, and Bax. Therefore, rat adipose tissue-derived exosomes can maintain metabolic balance of extracellular matrix and protect against apoptosis in rat nucleus pulposus cells.

Targeting skeletal interoception: a novel mechanistic insight into intervertebral disc degeneration and pain management

Despite being a leading cause of chronic pain and disability, the underlying mechanisms of intervertebral disc (IVD) degeneration (IVDD) remain unclear. Emerging evidence suggests that mechanosensation (the ability of the skeletal system to perceive mechanical and biochemical signals) mediated by abnormal mechanical loading plays a critical role in the regulation of IVD health. This review examines the complex interactions amongIVDs, intraosseous sensory mechanisms, and the central nervous system (CNS), with a particular focus on the roles of pathways such as PGE2/EP4, Wnt/β-catenin, and NF-κB. This review elucidates the manner in which mechanical stress and aberrant signaling disrupt the homeostasis of the nucleus pulposus (NP), cartilaginous endplate (CEP) and annulus fibrosus (AF), thereby driving degeneration and exacerbating pain. Furthermore, targeted therapeutic strategies, including the modulation of skeletal interoception and dynamic mechanical loading, present novel avenues for reversing IVDD progression. By integrating skeletal biology with spinal pathology, this work offers a novel perspective on the pathogenesis of IVDD and identifies promising strategies for clinical intervention. These findings highlight the potential of targeting skeletal interoception to mitigate IVDD and associated pain, paving the way for innovative, mechanism-driven therapies.

Pyroptosis: candidate key targets for mesenchymal stem cell-derived exosomes for the treatment of bone-related diseases

Bone-related diseases impact a large portion of the global population and, due to their high disability rates and limited treatment options, pose significant medical and economic challenges. Mesenchymal stem cells (MSCs) can differentiate into multiple cell types and offer strong regenerative potential, making them promising for treating various diseases. However, issues with the immune response and cell survival limit the effectiveness of cell transplantation. This has led to increased interest in cell-free stem cell therapy, particularly the use of exosomes, which is the most studied form of this approach. Exosomes are extracellular vesicles that contain proteins, lipids, and nucleic acids and play a key role in cell communication and material exchange. Pyroptosis, a form of cell death involved in innate immunity, is also associated with many diseases. Studies have shown that MSC-derived exosomes have therapeutic potential for treating a range of conditions by regulating inflammation and pyroptosis. This study explored the role of MSC-derived exosomes in modulating pyroptosis to improve the treatment of bone-related diseases.

Challenges in Application: Gelation Strategies of DAT-Based Hydrogel Scaffolds

Decellularized adipose tissue (DAT) has great clinical applicability, owing to its abundant source material, natural extracellular matrix microenvironment, and nonimmunogenic attributes, rendering it a versatile resource in the realm of tissue engineering. However, practical implementations are confronted with multifarious limitations. Among these, the selection of an appropriate gelation strategy serves as the foundation for adapting to diverse clinical contexts. The cross-linking strategies under varying physical or chemical conditions exert profound influences on the ultimate morphology and therapeutic efficacy of DAT. This review sums up the processes of DAT decellularization and subsequent gelation, with a specific emphasis on the diverse gelation strategies employed in recent experimental applications of DAT. The review expounds upon methodologies, underlying principles, and clinical implications of different gelation strategies, aiming to offer insights and inspiration for the application of DAT in tissue engineering and advance research for tissue engineering scaffold development.

Bioactive Hydrogel Supplemented with Stromal Cell-Derived Extracellular Vesicles Enhance Wound Healing

Background/Objectives: Skin regeneration is a rapidly advancing field with significant implications for regenerative medicine, particularly in treating wounds and burns. This study explores the potential of hydrogels functionalized with fibroblast-derived extracellular vesicles (EVs) to enhance skin regeneration in vivo. Being immunoprivileged, EVs minimize immune rejection, offering an attractive alternative to whole-cell therapies by replicating fibroblasts' key roles in tissue repair. Methods: To promote EVs' versatility and effective application across different conditions, a lyophilization method with lyoprotectants was optimized. Then, EVs were used to functionalize a hydrogel to perform experiments on murine cutaneous wound models. Results: Gelatin methacrylate (GelMA) was selected as the polymeric hydrogel due to its biocompatibility, tunable mechanical properties, and ability to support wound healing. Mechanical tests confirmed GelMA's strength and elasticity for this application. Fibroblast-derived EVs were characterized using Western blot, Transmission Electron Microscopy, and NanoSight analysis, proving their integrity, size distribution, and stability. miRNome profiling identified enriched biological pathways related to cell migration, differentiation, and angiogenesis, emphasizing the critical role of EV cargo in promoting wound repair. In a murine model, hydrogels loaded with fibroblast-derived EVs significantly accelerated wound healing compared to controls (mean wound area 0.62 mm2 and 4.4 mm2, respectively), with faster closure, enhanced epithelialization, increased vascularization, and reduced fibrosis. Notably, the lyoprotectants successfully preserved the EVs' structure and bioactivity during freeze-drying, reducing EVs loss by 35% compared to the control group and underscoring the feasibility of this approach for long-term storage and clinical application. Conclusions: This study introduces a novel scalable and adaptable strategy for regenerative medicine by combining fibroblast-derived EVs with GelMA, optimizing EVs' stability and functionality for enhanced wound healing in clinical settings, even in challenging contexts such as combat zones or large-scale natural disasters.

Functionalized Periosteum-Derived Microsphere-Hydrogel with Sequential Release of E7 Short Peptide/miR217 for Large Bone Defect Repairing

Large bone defects are still a persistent challenge in orthopedics. The availability limitations and associated complications of autologous and allogeneic bone have prompted an increasing reliance on tissue engineering and regenerative medicine. In this study, we developed an injectable scaffold combining an acellular extracellular periosteal matrix hydrogel with poly(d,l-lactate-co-glycol-acetate) microspheres loaded with the E7 peptide and miR217 (miR217/E7@MP-GEL). Characterization of the composites included morphological analysis by scanning electron microscopy, degradation and swelling tests, in vitro and in vivo biological evaluation, and the biological activity evaluation of mesenchymal stem cells (MSCs) through their effects on cell recruitment, proliferation, and osteogenic differentiation. The designed hydrogels demonstrated good physical and chemical properties that are cytocompatible and suitable for cell recruitment. In vitro studies confirmed the high biological activity of the release agent, which markedly enhanced the proliferation and osteogenic differentiation of MSCs. In vivo application to a rat model of a femur defect exhibited a significant increase in bone volume and density over 7 weeks, resulting in enhanced bone regeneration. Acellular periosteum-based hydrogels combined with the E7 peptide and miR217-loaded poly(d,l-lactate-co-glycol-acetate) microspheres can promote effective bone regeneration through the recruitment, proliferation, and osteogenic differentiation of MSCs, which provides a promising approach for the treatment of large bone defects.

Cartilage Endplate-Targeted Engineered Exosome Releasing and Acid Neutralizing Hydrogel Reverses Intervertebral Disc Degeneration

Cartilage endplate cell (CEPC) and nucleus pulposus cell (NPC) inflammation are critical factors that contribute to intervertebral disc degeneration (IVDD). Recent evidence indicated that iron ion influx, reactive oxygen species (ROS), and the cGAS-STING pathway are involved in CEPC inflammatory degeneration. Moreover, cytokines produced by degenerating CEPCs and lactic acid accumulation within the microenvironment significantly contribute to NPC inflammation. Consequently, simultaneous alleviation of CEPC inflammation and correction of the acidic microenvironment are anticipated to reverse IVDD. Herein, CEPC-targeted engineered exosomes loaded with salvianolic acid A are incorporated into a CaCO3/chitosan hydrogel, forming a composite gel, CAP-sEXOs@Gel. Notably, CAP-sEXOs@Gel shows long local retention, realizes the slow release of CAP-sEXOs and specific uptake by CEPCs. After uptake by CEPCs, CAP-sEXOs reduce intracellular iron ion and ROS by inhibiting hypoxia-inducible factor-2α (HIF-2α)/TfR1 expression. Iron ion influx and ROS inhibition contribute to the maintenance of normal mitochondrial function and reduced mtDNA leakage, suppresing the cGAS-STING pathway. Additionally, the CaCO3 component of CAP-sEXOs@Gel neutralizes H+, thereby alleviating NPC inflammation. Collectively, this novel composite hydrogel demonstrates the ability to concurrently inhibit CEPC and NPC inflammation, thereby presenting a promising therapeutic approach for IVDD.

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.

Bone aging and extracellular vesicles

Bone aging, a major global health concern, is the natural decline in bone mass and strength. Concurrently, extracellular vesicles (EVs), tiny membrane-bound particles produced by cells, have gained recognition for their roles in various physiological processes and age-related diseases. The interaction between EVs and bone aging is of growing interest, particularly their effects on bone metabolism, which become increasingly critical with advancing age. In this review, we explored the biology, types, and functions of EVs and emphasized their regulatory roles in bone aging. We examined the effects of EVs on bone metabolism and highlighted their potential as biomarkers for monitoring bone aging progression. Furthermore, we discussed the therapeutic applications of EVs, including targeted drug delivery and bone regeneration, and addressed the challenges associated with EV-based therapies, including the technical complexities and regulatory issues. We summarized the current research and clinical trials investigating the role of EVs in bone aging and suggested future research directions. These include the potential for personalized medicine using EVs and the integration of EV research with advanced technologies to enhance the management of age-related bone health. This analysis emphasized the transformative potential of EVs in understanding and managing bone aging, thereby marking a significant advancement in skeletal health research.

Adipose Mesenchymal Stem Cell-Derived Exosomes as Nanocarriers for Treating Musculoskeletal Disorders

Musculoskeletal disorders are a series of diseases involving bone, muscle, cartilage, and tendon, mainly caused by chronic strain, degenerative changes, and structural damage due to trauma. The disorders limit the function of patients due to pain and significantly reduce their quality of life. In recent years, adipose-derived mesenchymal stem cells have been extensively applied in regeneration medicine research due to their particular abilities of self-renewal, differentiation, and targeted homing and are more easily accessed compared with other sources. The paracrine effect of ADSCs plays a crucial role in intercellular communication by releasing mass mediators, including cytokines and growth factors, particularly the exosomes they secrete. Not only do these exosomes possess low immunogenicity, low toxicity, and an enhanced ability to penetrate a bio-barrier, but they also inherit their parent cells' characteristics and carry various bioactive molecules to release to targeted cells, modulating their biological process. Meanwhile, these characteristics also make exosomes a natural nanocarrier capable of targeted drug delivery to specific sites, enhancing the bioavailability of drugs within the body and achieving precision therapy with fewer toxic side effects. Furthermore, the integration of exosomes with tissue engineering and chemical modification strategies can also significantly enhance their efficacy in facilitating tissue repair. However, the current research on ADSC-Exos for improving MSDs remains at an early stage and needs further exploration. Therefore, this review summarized the ADSC-Exo as a nanodrug carrier characteristics and mechanism in the treatment of fracture, osteoporosis, osteoarthritis, intervertebral disc degeneration, and tendon injury, which push forward the research progress of ADSC-Exo therapy for MSDs.

Identification of pyroptosis-associated miRNAs in the immunoscape and prognosis of hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma is one of the most prevalent types of liver malignancy and poses a severe threat to global health. Despite recent improvements in therapeutic approaches, treatment options for patients with advanced or recurrent HCC are still limited.

MATERIALS AND METHODS

Our study analyzed miRNA differential expression using data from hepatocellular carcinoma patients in the Cancer Genome Atlas. Pyroptosis-related genes were identified from gene cards. Differential expression of miRNAs was analyzed using DESeq2 and visualized using ggplot2 and pheatmap. A prognostic risk model for pyroptosis-associated miRNAs was constructed using LASSO regression and validated by principal component analysis, Kaplan-Meier survival and ROC curve analysis. We also performed gene and pathway enrichment analysis. Immune cell infiltration and function in HCC were assessed using single-sample genomic enrichment analysis, and correlations with immune cells and function were explored. Also, CCK-8 assay as well as migration and invasion assays were performed after knockdown of miR-6844.

RESULTS

We have established and validated a prognostic risk model based on ten DEmiRNAs, which is important for the survival of HCC patients. Significant changes in immune cell infiltration and immune function were also found in high-risk patients. It also demonstrated that knockdown of miR-6844 inhibited HCC cell proliferation, migration and invasion, highlighting its role in HCC progression.

CONCLUSION

Our study reveals the implications of pyroptosis-associated differential miRNAs on the prognosis of patients with hepatocellular carcinoma and provides a foundation for novel HCC therapies, especially immunotherapy.

The pathogenesis and targeted therapies of intervertebral disc degeneration induced by cartilage endplate inflammation

Intervertebral disc degeneration (IVDD) is the leading cause of low back pain, where degeneration and death of nucleus pulposus cells within the intervertebral disc (IVD) can be obviously revealed. This degeneration can result in an imbalance in the extracellular matrix due to the loss of proteoglycans and water content, which can further lead to catabolic and anabolic dysfunction of the IVD. Recently, the dysfunction of cartilage endplate (CEP) during aging has drawn large attention due to its essential functions in contributing nutrient exchange and maintaining IVD homeostasis. Furthermore, the inflammation and disturbed homeostasis of CEP not only accelerate the degradation of nucleus pulposus extracellular matrix, but also exacerbate IVDD by causing nucleus pulposus cell death through other pathological factors. Here in this review, we summarized the possible pathological factors and the underlying mechanisms of the CEP inflammation-induced IVDD, including exosomes degeneration, CEP calcification, ferroptosis, mechanical changes, and cell senescence. Besides, changes of miRNAs, pain-related neural reflex arc and pathways associated with CEP inflammation-induced IVDD are also reviewed. In addition, new strategies specifically designed for CEP inflammation-induced IVDD are also discussed in the last section. We hope this paper can not only offer some new insights for advancing novel strategies for treating IVDD, but also serve as a valuable reference for researchers in this field.

Progress in the Application of Hydrogels in Intervertebral Disc Repair: A Comprehensive Review

PURPOSE OF REVIEW

Intervertebral disc degeneration (IVDD) is a common orthopaedic disease and an important cause of lower back pain, which seriously affects the work and life of patients and causes a large economic burden to society. The traditional treatment of IVDD mainly involves early pain relief and late surgical intervention, but it cannot reverse the pathological course of IVDD. Current studies suggest that IVDD is related to the imbalance between the anabolic and catabolic functions of the extracellular matrix (ECM). Anti-inflammatory drugs, bioactive substances, and stem cells have all been shown to improve ECM, but traditional injection methods face short half-life and leakage problems.

RECENT FINDINGS

The good biocompatibility and slow-release function of polymer hydrogels are being noticed and explored to combine with drugs or bioactive substances to treat IVDD. This paper introduces the pathophysiological mechanism of IVDD, and discusses the advantages, disadvantages and development prospects of hydrogels for the treatment of IVDD, so as to provide guidance for future breakthroughs in the treatment of IVDD.

Targeting nucleus pulposus cell death in the treatment of intervertebral disc degeneration

Background

Intervertebral disc degeneration (IDD) is a progressive age-related disorder characterized by the reduction in the number of nucleus pulposus cells (NPCs) and degradation of extracellular matrix (ECM), thereby leading to chronic pain and disability. The pathogenesis of IDD is multifaceted, and current therapeutic strategies remain limited. The nucleus pulposus (NP), primarily composed of NPCs, proteoglycans, and type II collagen, constitutes essential components for maintaining intervertebral disc (IVD) function and spinal motion. The disturbed homeostasis of NPCs is closely associated with IDD. Accumulating evidence increasingly suggests the crucial role of programmed cell death (PCD) in regulating the homeostasis of NPCs.

Aims

This review aimed to elucidate various forms of PCD and their respective roles in IDD, and investigate diverse strategies targeting the cell death of NPCs for IDD treatment.

Materials & Methods

We collected the relevant literature regarding PCD and their roles in the development of IDD. Subsequently, we comprehensively summarized the intricate association between PCD and IDD, and also explored the potential and application of cell therapy and traditional Chinese medicine (TCM) in the prevention and treatment of IDD.

Results

Current literature indicated that the PCD of NPCs was closely associated with the pathogenesis of IDD. Additionally, the development of targeted pharmaceuticals based on the mechanisms of PCD could effectively impede the loss of NPCs.

Conclusion

This review demonstrated that targeting the PCD of NPCs may be a promising strategy for the treatment of IDD.

Exosomes Reshape the Osteoarthritic Defect: Emerging Potential in Regenerative Medicine-A Review

Osteoarthritis (OA) is a joint disorder caused by wear and tear of the cartilage that cushions the joints. It is a progressive condition that can cause significant pain and disability. Currently, there is no cure for OA, though there are treatments available to manage symptoms and slow the progression of the disease. A chondral defect is a common and devastating lesion that is challenging to treat due to its avascular and aneural nature. However, there are conventional therapies available, ranging from microfracture to cell-based therapy. Anyhow, its efficiency in cartilage defects is limited due to unclear cell viability. Exosomes have emerged as a potent therapeutic tool for chondral defects because they are a complicated complex containing cargo of proteins, DNA, and RNA as well as the ability to target cells due to their phospholipidic composition and the altering exosomal contents that boost regeneration potential. Exosomes are used in a variety of applications, including tissue healing and anti-inflammatory therapy. As in recent years, biomaterials-based bio fabrication has gained popularity among the many printable polymer-based hydrogels, tissue-specific decellularized extracellular matrix might boost the effects rather than an extracellular matrix imitating environment, a short note has been discussed. Exosomes are believed to be the greatest alternative option for current cell-based therapy, and future progress in exosome-based therapy could have a greater influence in the field of orthopaedics. The review focuses extensively on the insights of exosome use and scientific breakthroughs centered OA.

Diacetoxy-6-gingerdiol protects the extracellular matrix of nucleus pulposus cells and ameliorates intervertebral disc degeneration by inhibiting the IL-1β-mediated NLRP3 pathway

Intervertebral disc degeneration (IDD) is a common cause of low back pain, causing a huge emotional and economic burden on patients and society. Reduction of nucleus pulposus cells (NPC) and extracellular matrix (ECM) is the main feature of IDD, and NPC is the main source of ECM. Thermal apoptosis is a newly discovered form of cell death in recent years that differs significantly from apoptosis in terms of molecular mechanisms and cellular morphological changes. Diacetoxy-6-gingerdiol(D-6-G), a type of gingerol, has anti-inflammatory and antioxidant effects, but whether it has an inhibitory effect on cellular pyroptosis is not clear. Therefore, in the present study, we investigated the effect of D-6-G on the ECM of the nucleus pulposus oblongata under IL-1β treatment, as well as the mechanism of its effect on NLRP3 inflammasome and cellular focal death. In vitro cellular experiments demonstrated that D-6-G could bind to and inhibit the activity of NLRP3 inflammasome, and interestingly, D-6-G could also inhibit cellular pyroptosis and protect the nucleus pulposusry cellular microenvironment by activating the Nrf2/HO-1 axis. In conclusion, we found that D-6-G could inhibit NLRP3 inflammatory vesicle activity as well as cellular pyroptosis in NPCs and protect the ECM, suggesting the potential of D-6-G to delay IDD.

Role of oxidative stress in mitochondrial dysfunction and their implications in intervertebral disc degeneration: Mechanisms and therapeutic strategies

Background

Intervertebral disc degeneration (IVDD) is widely recognized as one of the leading causes of low back pain. Intervertebral disc cells are the main components of the intervertebral disc (IVD), and their functions include synthesizing and secreting collagen and proteoglycans to maintain the structural and functional stability of the IVD. In addition, IVD cells are involved in several physiological processes. They help maintain nutrient metabolism balance in the IVD. They also have antioxidant and anti-inflammatory effects. Because of these roles, IVD cells are crucial in IVDD. When IVD cells are subjected to oxidative stress, mitochondria may become damaged, affecting normal cell function and accelerating degenerative changes. Mitochondria are the energy source of the cell and regulate important intracellular processes. As a key site for redox reactions, excessive oxidative stress and reactive oxygen species can damage mitochondria, leading to inflammation, DNA damage, and apoptosis, thus accelerating disc degeneration.

Aim of review

Describes the core knowledge of IVDD and oxidative stress. Comprehensively examines the complex relationship and potential mechanistic pathways between oxidative stress, mitochondrial dysfunction and IVDD. Highlights potential therapeutic targets and frontier therapeutic concepts. Draws researchers' attention and discussion on the future research of all three.

Key scientific concepts of review

Origin, development and consequences of IVDD, molecular mechanisms of oxidative stress acting on mitochondria, mechanisms of oxidative stress damage to IVD cells, therapeutic potential of targeting mitochondria to alleviate oxidative stress in IVDD.

The translational potential of this article

Targeted therapeutic strategies for oxidative stress and mitochondrial dysfunction are particularly critical in the treatment of IVDD. Using antioxidants and specific mitochondrial therapeutic agents can help reduce symptoms and pain. This approach is expected to significantly improve the quality of life for patients. Individualized therapeutic approaches, on the other hand, are based on an in-depth assessment of the patient's degree of oxidative stress and mitochondrial functional status to develop a targeted treatment plan for more precise and effective IVDD management. Additionally, we suggest preventive measures like customized lifestyle changes and medications. These are based on understanding how IVDD develops. The aim is to slow down the disease and reduce the chances of it coming back. Actively promoting clinical trials and evaluating the safety and efficacy of new therapies helps translate cutting-edge treatment concepts into clinical practice. These measures not only improve patient outcomes and quality of life but also reduce the consumption of healthcare resources and the socio-economic burden, thus having a positive impact on the advancement of the IVDD treatment field.

Bone Mesenchymal Stem Cells Inhibit Oxidative Stress-Induced Pyroptosis in Annulus Fibrosus Cells to Alleviate Intervertebral Disc Degeneration Based on Matric Hydrogels

Intervertebral disc degeneration (IVDD) is the primary cause of low back pain. Stem cell transplantation may be a possible approach to promote IVDD. This study was aimed to investigate the role of bone mesenchymal stem cells (BMSCs) in IVDD and the molecular mechanism. Annulus fibrosus cells (AFCs) were treated with tert-butyl hydroperoxide (TBHP) to induce oxidative stress injury. AFC biological functions were analyzed using a lactate dehydrogenase kit, enzyme-linked immunosorbent assay, flow cytometry, and western blot. The molecular mechanisms of BMSC functions were assessed using quantitative real-time PCR, western blot, immunoprecipitation (IP), co-IP, GST pull-down, and cycloheximide treatment. Furthermore, the impacts of BMSCs in IVDD progression in vivo were evaluated by magnetic resonance imaging (MRI) and H&E analysis. BMSCs inhibited TBHP-induced inflammation and pyroptosis in AFCs. Knockdown of SIRT1 reversed the effects on inflammation and pyroptosis of BMSCs. Moreover, SIRT1 promoted the deacetylation of ASC rather than NLRP3. SIRT1 interacted with ASC to reduce its protein stability, thereby negatively regulating ASC protein levels. In addition, BMSCs alleviated LPS-induced IVDD based on matrix hydrogels. BMSCs inhibited oxidative stress-induced pyroptosis and inflammation in AFCs, thereby alleviating IVDD, suggesting that BMSCs may contribute to treating intervertebral disc generation.

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.

TNF-α-licensed exosome-integrated titaniumaccelerated T2D osseointegration by promoting autophagy-regulated M2 macrophage polarization

Type 2 diabetes (T2D) is on a notable rise worldwide, which leads to unfavorable outcomes during implant treatments. Surface modification of implants and exosome treatment have been utilized to enhance osseointegration. However, there has been insufficient approach to improve adverse osseointegration in T2D conditions. In this study, we successfully loaded TNF-α-treated mesenchymal stem cell (MSC)-derived exosomes onto micro/nano-network titanium (Ti) surfaces. TNF-α-licensed exosome-integrated titanium (TNF-exo-Ti) effectively enhanced M2 macrophage polarization in hyperglycemic conditions, with increased secretion of anti-inflammatory cytokines and decreased secretion of pro-inflammatory cytokines. In addition, TNF-exo-Ti pretreated macrophage further enhanced angiogenesis and osteogenesis of endothelial cells and bone marrow MSCs. More importantly, TNF-exo-Ti markedly promoted osseointegration in T2D mice. Mechanistically, TNF-exo-Ti activated macrophage autophagy to promote M2 polarization through inhibition of the PI3K/AKT/mTOR pathway, which could be abolished by PI3K agonist. Thus, this study established TNF-α-licensed exosome-immobilized titanium surfaces that could rectify macrophage immune states and accelerate osseointegration in T2D conditions.

Application trends and strategies of hydrogel delivery systems in intervertebral disc degeneration: A bibliometric review

Hydrogels are widely used to explore emerging minimally invasive strategies for intervertebral disc degeneration (IVDD) due to their suitability as drug and cell delivery vehicles. There has been no review of the latest research trends and strategies of hydrogel delivery systems in IVDD for the last decade. In this study, we identify the application trends and strategies in this field through bibliometric analysis, including aspects such as publication years, countries and institutions, authors and publications, and co-occurrence of keywords. The results reveal that the literature in this field has been receiving increasing attention with a trend of growth annually. Subsequently, the hotspots of hydrogels in this field were described and discussed in detail, and we proposed the "four core factors", hydrogels, cells, cell stimulators, and microenvironmental regulation, required for a multifunctional hydrogel for IVDD. Finally, we discuss the popular and emerging mechanistic strategies of hydrogel therapy for IVDD in terms of five aspects: fundamental pathologic changes in IVDD, counteracting cellular senescence, counteracting cell death, improving organelle function, and replenishing exogenous cells. This study provides a reference and a new perspective for future research in this urgently needed field.

Paravertebrally-Injected Multifunctional Hydrogel for Sustained Anti-Inflammation and Pain Relief in Lumbar Disc Herniation

Pain caused by lumbar disc herniation (LDH) severely compromises patients' quality of life. The combination of steroid and local anesthetics is routinely employed in clinics to alleviate LDH-induced pain. However, the approach only mediates transient efficacy and requires repeated and invasive lumbar epidural injections. Here a paravertebrally-injected multifunctional hydrogel that can efficiently co-load and controlled release glucocorticoid betamethasone and anesthetics ropivacaine for sustained anti-inflammation, reactive oxygen species (ROS)-removal and pain relief in LDH is presented. Betamethasone is conjugated to hyaluronic acid (HA) via ROS-responsive crosslinker to form amphiphilic polymer that self-assemble into particles with ropivacaine loaded into the core. Solution of drug-loaded particles and thermo-sensitive polymer rapidly forms therapeutic hydrogel in situ upon injection next to the herniated disc, thus avoiding invasive epidural injection. In a rat model of LDH, multifunctional hydrogel maintains the local drug concentration 72 times longer than free drugs and more effectively inhibits the expression of pro-inflammatory cytokines and pain-related molecules including cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2). Therapeutic hydrogel suppresses the LDH-induced pain in rats for 12 days while the equivalent dose of free drugs is only effective for 3 days. This platform is also applicable to ameliorate pain caused by other spine-related diseases.

Mapping knowledge structure and themes trends of non-surgical treatment in intervertebral disc degeneration

Background

Intervertebral disc degeneration (IDD) is a chronic disabling disease caused by degeneration of nucleus pulposus cells, decreased activity and the number of nucleus pulposus cells, decreased extracellular matrix, and infiltration of inflammatory factors, resulting in low back and leg pain. Recent studies have shown that non-surgical treatment is of great significance in reversing the progression of degenerative disc disease, and there are more relevant literature reports. However, there is no bibliometric analysis in this area. This study aimed to describe the knowledge structure and thematic trends of non-surgical treatment methods for IDD through bibliometrics.

Methods

Articles and reviews on non-surgical treatment of disc degeneration from 1998 to 2022 were collected on the Web of Science. VOSviewer 1.6.18, CiteSpace 6.1.R3, R package "bibliometrix" and two online analysis platforms were used for bibliometric and visual literature analysis.

Results

961 articles were screened for inclusion, including 821 articles and 140 reviews. The analysis of our study shows that publications in the non-surgical treatment of disc degeneration are increasing annually, with publications coming mainly from North America and Asia, with China and the United States dominating. Huazhong Univ Sci & Technol and Wang K are the most prolific institutions and authors, respectively, and Le Maitre CL is the most co-cited author. However, there is less collaboration between institutions in different countries. Spine is both the most published and the most cited journal. According to the co-citation and co-occurrence analysis results, "mesenchymal stem cells," "exosomes," "medication," and "tissue engineering" are the current research hotspots in this field.

Conclusions

This study employs bibliometric analysis to explore the knowledge structure and trends of non-surgical treatments for IDD from 2013 to 2022. Key research hotspots include mesenchymal stem cells, exosomes, medication, and tissue engineering. The number of publications, especially from China and the USA, has increased significantly, though international collaboration needs improvement. Influential contributors include Wang K and the journal Spine. These findings provide a comprehensive overview and highlight important future directions for the field.

The role of extracellular vesicles in pyroptosis-mediated infectious and non-infectious diseases

Pyroptosis, a lytic and pro-inflammatory cell death, is important in various pathophysiological processes. Host- and bacteria-derived extracellular vesicles (EVs), as natural nanocarriers messengers, are versatile mediators of intercellular communication between different types of cells. Recently, emerging research has suggested that EVs exhibit multifaceted roles in disease progression by manipulating pyroptosis. This review focuses on new findings concerning how EVs shape disease progression in infectious and non-infectious diseases by regulating pyroptosis. Understanding the characteristics and activity of EVs-mediated pyroptotic death may conducive to the discovery of novel mechanisms and more efficient therapeutic targets in infectious and non-infectious diseases.

Effects of cell culture time and cytokines on migration of dental pulp stem cell-derived chondrogenic cells in collagen hydrogels

The transplantation of collagen hydrogels encapsulating human dental pulp stem cell (DPSC)-derived chondrogenic cells is potentially a novel approach for the regeneration of degenerated nucleus pulposus (NP) and cartilage. Grafted cell migration allows cells to disperse in the hydrogels and the treated tissue from the grafted location. We previously reported the cell migration in type I and type II hydrogels. It is important to explore further how cell culture time affect the cell motility. In this study, we observed the decreased motility of DPSC-derived chondrogenic cells after culturing for 2 weeks compared with cells cultured for 2 days in these gels. The Alamarblue assay showed the cell proliferation during the two-week cell culture period. The findings suggest that the transitions of cell motility and proliferation during the longer culture time. The result indicates that the early culture stage is an optimal time for cell transplantation. In a degenerated disc, the expression of IL-1β and TNFα increased significantly compared with healthy tissue and therefore may affect grafted cell migration. The incorporation of IL-1β and TNFα into the collagen hydrogels decreased cell motility. The study indicates that the control of IL-1β and TNFα production may help to maintain cell motility after transplantation.

Exploration of the mode of death and potential death mechanisms of nucleus pulposus cells

Intervertebral disc degeneration (IVDD) is a common chronic orthopaedic disease in orthopaedics that imposes a heavy economic burden on people and society. Although it is well established that IVDD is associated with genetic susceptibility, ageing and obesity, its pathogenesis remains incompletely understood. Previously, IVDD was thought to occur because of excessive mechanical loading leading to destruction of nucleus pulposus cells (NPCs), but studies have shown that IVDD is a much more complex process associated with inflammation, metabolic factors and NPCs death and can involve all parts of the disc, characterized by causing NPCs death and extracellular matrix (ECM) degradation. The damage pattern of NPCs in IVDD is like that of some programmed cell death, suggesting that IVDD is associated with programmed cell death. Although apoptosis and pyroptosis of NPCs have been studied in IVDD, the pathogenesis of intervertebral disc degeneration can still not be fully elucidated by using only traditional cell death modalities. With increasing research, some new modes of cell death, PANoptosis, ferroptosis and senescence have been found to be closely related to intervertebral disc degeneration. Among these, PANoptosis combines essential elements of pyroptosis, apoptosis and necroptosis to form a highly coordinated and dynamically balanced programmed inflammatory cell death process. Furthermore, we believe that PANoptosis may also crosstalk with pyroptosis and senescence. Therefore, we review the progress of research on multiple deaths of NPCs in IVDD to provide guidance for clinical treatment.

Pyroptosis in Skeleton Diseases: A Potential Therapeutic Target Based on Inflammatory Cell Death

Skeletal disorders, including fractures, osteoporosis, osteoarthritis, rheumatoid arthritis, and spinal degenerative conditions, along with associated spinal cord injuries, significantly impair daily life and impose a substantial burden. Many of these conditions are notably linked to inflammation, with some classified as inflammatory diseases. Pyroptosis, a newly recognized form of inflammatory cell death, is primarily triggered by inflammasomes and executed by caspases, leading to inflammation and cell death through gasdermin proteins. Emerging research underscores the pivotal role of pyroptosis in skeletal disorders. This review explores the pyroptosis signaling pathways and their involvement in skeletal diseases, the modulation of pyroptosis by other signals in these conditions, and the current evidence supporting the therapeutic potential of targeting pyroptosis in treating skeletal disorders, aiming to offer novel insights for their management.

Exploring the relationship between pyroptosis and inflammatory bone loss: Evidence from a cigarette smoke-induced osteoporosis mouse model

Smoking is by far one of the greatest public health threats and is recognized as an important predisposing factor for osteoporosis. Exposure to cigarette smoke (CS) has been reported to be associated with inflammation-associated diseases through the induction of pyroptosis. Nevertheless, the correlation between pyroptosis and bone loss induced by CS remains uninvestigated. Here, a mouse model of mainstream smoke exposure-induced osteoporosis was established. μCT, biomechanical testing, and immunohistochemical staining of bone tissue were used to assess the deleterious effects of CS on bone metabolism. In vitro, the effects of cigarette smoke extracts (CSE) on mouse primary bone marrow-derived mesenchymal stem cells (BMSCs) were tested by cell viability assays, gene and protein expression assays, and alizarin red staining. The utilization of the pyroptosis inhibitor MCC950 served to confirm the critical role of BMSCs pyroptosis in CS-induced osteoporosis. Our results indicated that exposure to mainstream smoke led to a notable decrease in the quantity of osteoblasts and hindered the process of osteogenic differentiation in mice. Additionally, there was a significant increase in the expression of pyroptosis-related proteins in the bone marrow. The inhibitory effects of CSE on cell viability and osteogenic differentiation of BMSCs were found to be dose-dependent in vitro. However, the presence of the pyroptosis inhibitor MCC950 significantly improved the impaired osteogenic differentiation and bone mineralization caused by CSE. These results highlight the crucial involvement of BMSCs pyroptosis in the development of bone loss induced by CS. In summary, the findings of this study provide novel evidence that CS exerts a detrimental effect on the process of osteogenesis in BMSCs through the induction of pyroptosis, ultimately leading to bone loss. Inhibition of pyroptosis effectively attenuated the toxicological effects of CS on BMSCs, providing a new target for preventing inflammatory osteoporosis.

Unveiling the Therapeutic Potential of hUCMSC-Derived EVs in Intervertebral Disc Degeneration through MALAT1/miR-138-5p/SLC7A11 Coexpression Regulation

Intervertebral disc degeneration (IVDD) is a prevalent chronic condition causing spinal pain and functional impairment. This study investigates the role of extracellular vesicles (EVs) derived from human umbilical cord mesenchymal stem cells (hUCMSCs) in regulating IVDD. Using RNA-seq, we analyzed differential expressions of lncRNA and miRNA in nucleus pulposus tissues from various mouse groups. We identified key regulatory molecules, MALAT1 and miRNA-138-5p, which contribute to IVDD. Further experiments demonstrated that MALAT1 can up-regulate SLC7A11 expression by competitively binding to miR-138-5p, forming a MALAT1/miR-138-5p/SLC7A11 coexpression regulatory network. This study elucidates the molecular mechanism by which hUCMSC-derived EVs regulate IVDD and could help develop novel therapeutic strategies for treating this condition. Our findings demonstrate that hUCMSCs-EVs inhibit ferroptosis in nucleus pulposus cells, thereby improving IVDD. These results highlight the therapeutic potential of hUCMSCs-EVs in ameliorating the development of IVDD, offering significant scientific and clinical implications for new treatments.

Injectable Hydrogel Based on Enzymatic Initiation of Keratin Methacrylate for Controlled Exosome Release in Intervertebral Disc Degeneration Therapy

The treatment of intervertebral disc degeneration (IVDD) using bone marrow mesenchymal stem cell‐derived exosomes has shown success in alleviating inflammation and restoring the extracellular matrix (ECM), however, challenges persist due to the deficiency in mechanical support and controlled release. Herein, a carbon‐carbon double bond modified keratin (KeMA) is synthesized by 2‐isocyanatoethyl modification for exosomes wrapping. This injectable KeMA hydrogel, initiated by a biocompatible glucose/ glucose oxidase/ horse radish peroxidase enzymatic cascade reaction with acetylacetone and N‐vinylpyrrolidone, displayed rapid gelation, resembling nucleus pulposus (NP) elasticity, and excellent cytocompatibility. In vitro studies showcased that the exosomes‐loaded KeMA hydrogel (Exo@KeMA) enhanced exosome release kinetics, suppressed inflammation, fostered extracellular matrix (ECM) regeneration, and reinstated NP biomechanics. RNA‐seq analysis indicated Exo@KeMA's effects involved PI3K‐Akt signaling for matrix regeneration and NF‐κB signaling inhibition for anti‐inflammation. In vivo IVDD rat models demonstrated Exo@KeMA attenuated inflammation, maintained NP water content, preserved disc height, and promoted structural regeneration. This research introduces an injectable KeMA hydrogel as a promising therapy for IVDD, by facilitating biomechanics restoration, anti‐inflammatory response, and ECM regeneration.

Extracellular matrix hydrogels with fibroblast growth factor 2 containing exosomes for reconstructing skin microstructures

Decellularized extracellular matrix hydrogel (ECM hydrogel), a natural material derived from normal tissue with unique biocompatibility properties, is widely used for tissue repair. However, there are still problems such as poor biological activity and insufficient antimicrobial property. To overcome these drawbacks, fibroblast growth factor 2 (FGF 2) containing exosome (exoFGF 2) was prepared to increase the biological activity. Furthermore, the antimicrobial capacity of ECM hydrogel was optimised by using copper ions as a ligand-bonded cross-linking agent. The decellularized extracellular matrix hydrogel, intricately cross-linked with copper ions through ligand bonds and loaded with FGF 2 containing exosome (exoFGF 2@ECM/Cu2+ hydrogel), has demonstrated exceptional biocompatibility and antimicrobial properties. In vitro, exoFGF 2@ECM/Cu2+ hydrogel effectively promoted cell proliferation, migration, antioxidant and inhibited bacterial growth. In vivo, the wound area of rat treated with exoFGF 2@ECM/Cu2+ hydrogels were significantly smaller than that of other groups at Day 5 (45.24% ± 3.15%), Day 10 (92.20% ± 2.31%) and Day 15 (95.22% ± 1.28%). Histological examination showed that exoFGF 2@ECM/Cu2+ hydrogels promoted angiogenesis and collagen deposition. Overall, this hydrogel has the potential to inhibit bacterial growth and effectively promote wound healing in a variety of clinical applications.

Enhancing neovascularization post-myocardial infarction through injectable hydrogel functionalized with endothelial-derived EVs

Over the past three decades, cell therapy development has fallen short of expectations, with many cellular sources demonstrating a 'Janus effect' and raising safety concerns. Extracellular vesicles (EVs), supported by advanced technologies, present a promising avenue in regenerative medicine, offering benefits such as immune tolerance and avoidance of negative aspects associated with cell transplants. Our previous research showcased enhanced and organized subcutaneous vascularization using three-dimensional bioprinted patches containing HUVEC-derived EVs in immunodeficient animal models. In this context, stress conditions on the cells of origin further boosted the EVs' neoangiogenic potential. Since neovascularization is the first regenerative target requiring restoration, the present study aims to complement our previous work by employing an injectable gelatin methacrylate (GelMA) hydrogel functionalized with HUVEC-derived EVs in a pathological condition of acute myocardial infarction. This bioactive hydrogel resulted in reduced fibrosis, improved contractility, and promoted angiogenesis, showing promise in countering tissue deterioration and addressing vascular deficits. Moreover, the molecular characterization of EVs through miRNome and proteomic analyses further supports their potential as bio-additives for hydrogel functionalization. This cell-free approach mitigates immune rejection and oncogenic risks, offering innovative therapeutic advantages.

Exosome-loaded hydrogels for craniofacial bone tissue regeneration

It is common for maladies and trauma to cause significant bone deterioration in the craniofacial bone, which can cause patients to experience complications with their appearance and their ability to function. Regarding grafting procedures' complications and disadvantages, the newly emerging field of tissue regeneration has shown promise. Tissue -engineered technologies and their applications in the craniofacial region are increasingly gaining prominence with limited postoperative risk and cost. MSCs-derived exosomes are widely applied in bone tissue engineering to provide cell-free therapies since they not only do not cause immunological rejection in the same way that cells do, but they can also perform a cell-like role. Additionally, the hydrogel system is a family of multipurpose platforms made of cross-linked polymers with considerable water content, outstanding biocompatibility, and tunable physiochemical properties for the efficient delivery of commodities. Therefore, the promising exosome-loaded hydrogels can be designed for craniofacial bone regeneration. This review lists the packaging techniques for exosomes and hydrogel and discusses the development of a biocompatible hydrogel system and its potential for exosome continuous delivery for craniofacial bone healing.

Magnetic Polysaccharide Mesenchymal Stem Cells Exosomes Delivery Microcarriers for Synergistic Therapy of Osteoarthritis

Osteoarthritis (OA) is a prevalent degenerative disease that afflicts more than 250 million people worldwide, impairing their mobility and quality of life. However, conventional drug therapy is palliative. Exosomes (Exo), although with the potential to fundamentally repair cartilage, face challenges in their efficient enrichment and delivery. In this study, we developed magnetic polysaccharide hydrogel particles as microcarriers for synergistic therapy of OA. The microcarriers were composed of modified natural polysaccharides, hyaluronic acid (HAMA), and chondroitin sulfate (CSMA), and were generated from microfluidic electrospray in combination with a cryogelation process. Magnetic nanoparticles with spiny structures capable of capturing stem cell Exo were encapsulated within the microcarriers together with an anti-inflammatory drug diclofenac sodium (DS). The released DS and Exo from the microcarriers had a synergistic effect in alleviating the OA symptoms and promoting cartilage repair. The in vitro and in vivo results demonstrated the excellent performance of the microcarrier for OA treatment. We believe this work has potential for Exo therapy of OA and other related diseases.

M2 Macrophage-Derived Small Extracellular Vesicles Ameliorate Pyroptosis and Intervertebral Disc Degeneration

Intervertebral discs (IVDs) have a limited self-regenerative capacity and current strategies for IVD regeneration are unsatisfactory. Recent studies showed that small extracellular vesicles derived from M2 macrophage cells (M2-sEVs) inhibited inflammation by delivery of various bioactive molecules to recipient cells, which indicated that M2-sEVs may offer a therapeutic strategy for the repair of IVDs. Herein, we investigated the roles and mechanisms of M2-sEVs on IVD regeneration. The in vitro results demonstrated that M2-sEVs inhibited pyroptosis, preserved cellular viability, and promoted migration of nucleus pulposus cells (NPCs). Bioinformatics analysis and verification experiments of microRNA (miR) expression showed that miR-221-3p was highly expressed in M2-sEVs. The mechanism of action was explored and indicated that M2-sEVs inhibited pyroptosis of NPCs through transfer of miR-221-3p, which suppressed the expression levels of phosphatase and tensin homolog and NOD-, LRR-, and pyrin domain-containing protein 3. Moreover, we fabricated decellularized ECM-hydrogel (dECM) for sustained release of M2-sEVs, which exhibited biocompatibility and controlled release properties. The in vivo results revealed that dECM-hydrogel containing M2-sEVs (dECM/M2-sEVs) delayed the degeneration of intervertebral disc degeneration (IDD) models. In addition to demonstrating a promising therapeutic for IDD, this study provided valuable data for furthering the understanding of the roles and mechanisms of M2-sEVs in IVD regeneration.

A novel exosome-based multifunctional nanocomposite platform driven by photothermal-controlled release system for repair of skin injury

Currently, exosomes showed appropriate potential in the repair of skin injury. However, the functions of the exosomes could be compromised rapidly due to their short half-life and high clearance rate in vivo. In addition, the controlled release of effective concentrations of exosomes could increase the utilization efficiency of exosomes in wound healing. Accordingly, the design of an effective system for the controlled delivery of exosomes during the wound treatment period was necessary. In this contribution, we designed a novel exosome-based multifunctional nanocomposite platform with photothermal-controlled release performance for the repair of skin injury. Based on the agarose hydrogel, two-dimensional Ti3C2 (Ti3C2 MXene) and human umbilical cord mesenchymal stem cell (hucMSC)-derived exosomes, the as-prepared platform (i.e., hucMSC-derived exosome/Ti3C2 MXene hydrogel) was synthesized for the first time. Apart from possessing injectability, the hucMSC-derived exosome/Ti3C2 MXene hydrogel utilized the excellent photothermal effect of Ti3C2 MXene and proper phase transition performance of agarose hydrogel to provide a photothermal-controlled release system for the hucMSC-derived exosomes, which was beneficial for the personalized on-demand drug delivery. Importantly, the hucMSC-derived exosomes maintained their inherent structure and activity after being released from the Ti3C2 MXene hydrogel. Additionally, the as-prepared hydrogel with multifunctional performance also presented remarkable biocompatibility and photothermal-antibacterial property, and could efficiently accelerate wound healing by promoting cell proliferation, angiogenesis, collagen deposition, and reducing the level of inflammation at the wound site. The results suggested that the exosome-based multifunctional nanocomposite platform with great potential for wound healing would make significant advances in the revolution of traditional treatment methods in skin injury.

Thread-structural microneedles loaded with engineered exosomes for annulus fibrosus repair by regulating mitophagy recovery and extracellular matrix homeostasis

Low back pain is among the most grave public health concerns worldwide and the major clinical manifestation of intervertebral disc degeneration (IVDD). The destruction of annulus fibrosus (AF) is the primary cause of IVDD. A sustainable and stable treatment system for IVDD is lacking because of the special organizational structure and low nutrient supply of AF. We here found that IVDD results in the impaired mitochondrial function of AF tissue, and mitochondrial autophagy (mitophagy) plays a protective role in this process. We therefore reported a thread-structural microneedle (T-MN) matching the ring structure of AF. Based on the adsorption effect of laminin, our T-MN could load with bone marrow mesenchymal stem cell-derived exosomes to envelope the regulating mitophagy microRNA (miRNA 378), named as T-MN@EXO@miR-378. In general, we offered in situ locking in the defect site of AF to prevent nucleus pulposus leakage and promoted AF repair. The design of the thread structure was aimed at bionically matching the layered AF structure, thereby providing stronger adhesion. The T-MN@EXO@miR-378 effectively attached to AF and slowly released therapeutic engineered exosomes, and prevented IVDD progression by restoring mitophagy, promoting AF cell proliferation and migration, and inhibiting the pathological remodeling of the extracellular matrix. This functional system can be used as an excellent tool for sustained drug release and has a certain prospect in substituting the conventional treatment of IVDD.