Delivery of coenzyme Q10 loaded micelle targets mitochondrial ROS and enhances efficiency of mesenchymal stem cell therapy in intervertebral disc degeneration

A ROS-responsive hydrogel incorporated with dental follicle stem cell-derived small extracellular vesicles promotes dental pulp repair by ameliorating oxidative stress

Pulpitis, an inflammatory disease of dental pulp tissues, ultimately results in the loss of pulp defense properties. Existing clinical modalities cannot effectively promote inflamed pulp repair. Oxidative stress is a major obstacle inhibiting pulp repair. Due to their powerful antioxidative capacity, mesenchymal stem cell-derived small extracellular vesicles (MSC-sEVs) exhibit potential for treating oxidative stress-related disorders. However, whether MSC-sEVs shield dental pulp tissues from oxidative damage is largely unknown. Here, we showed that dental follicle stem cell-derived sEVs (DFSC-sEVs) have antioxidative and prohealing effects on a rat LPS-induced pulpitis model by enhancing the survival, proliferation and odontogenesis of H2O2-injured dental pulp stem cells (DPSCs). Additionally, DFSC-sEVs restored the oxidative/antioxidative balance in DPSC mitochondria and had comparable effects on ameliorating mitochondrial dysfunction with the mitochondrion-targeted antioxidant Mito-Tempo. To improve the efficacy of DFSC-sEVs, we fabricated an intelligent and injectable hydrogel to release DFSC-sEVs by combining sodium alginate (SA) and the ROS sensor RhB-AC. The newly formed SA-RhB hydrogel efficiently encapsulates DFSC-sEVs and exhibits controlled release of DFSC-sEVs in a HClO/ClO- concentration-dependent manner, providing a synergistic antioxidant effect with DFSC-sEVs. These results suggest that DFSC-sEVs-loaded SA-RhB is a promising minimally invasive treatment for pulpitis by enhancing tissue repair in the pulp wound microenvironment.

Experimental validation and comprehensive analysis of m6A methylation regulators in intervertebral disc degeneration subpopulation classification

Intervertebral disc degeneration (IVDD) is one of the most prevalent causes of chronic low back pain. The role of m6A methylation modification in disc degeneration (IVDD) remains unclear. We investigated immune-related m6A methylation regulators as IVDD biomarkers through comprehensive analysis and experimental validation of m6A methylation regulators in disc degeneration. The training dataset was downloaded from the GEO database and analysed for differentially expressed m6A methylation regulators and immunological features, the differentially regulators were subsequently validated by a rat IVDD model and RT-qPCR. Further screening of key m6A methylation regulators based on machine learning and LASSO regression analysis. Thereafter, a predictive model based on key m6A methylation regulators was constructed for training sets, which was validated by validation set. IVDD patients were then clustered based on the expression of key m6A regulators, and the expression of key m6A regulators and immune infiltrates between clusters was investigated to determine immune markers in IVDD. Finally, we investigated the potential role of the immune marker in IVDD through enrichment analysis, protein-to-protein network analysis, and molecular prediction. By analysising of the training set, we revealed significant differences in gene expression of five methylation regulators including RBM15, YTHDC1, YTHDF3, HNRNPA2B1 and ALKBH5, while finding characteristic immune infiltration of differentially expressed genes, the result was validated by PCR. We then screen the differential m6A regulators in the training set and identified RBM15 and YTHDC1 as key m6A regulators. We then used RBM15 and YTHDC1 to construct a predictive model for IVDD and successfully validated it in the training set. Next, we clustered IVDD patients based on the expression of RBM15 and YTHDC1 and explored the immune infiltration characteristics between clusters as well as the expression of RBM15 and YTHDC1 in the clusters. YTHDC1 was finally identified as an immune biomarker for IVDD. We finally found that YTHDC1 may influence the immune microenvironment of IVDD through ABL1 and TXK. In summary, our results suggest that YTHDC1 is a potential biomarker for the development of IVDD and may provide new insights for the precise prevention and treatment of IVDD.

The Emerging Roles of Nanocarrier Drug Delivery System in Treatment of Intervertebral Disc Degeneration-Current Knowledge, Hot Spots, Challenges and Future Perspectives

Low back pain (LBP) is a common condition that has substantial consequences on individuals and society, both socially and economically. The primary contributor to LBP is often identified as intervertebral disc degeneration (IVDD), which worsens and leads to significant spinal problems. The conventional treatment approach for IVDD involves physiotherapy, drug therapy for pain management, and, in severe cases, surgery. However, none of these treatments address the underlying cause of the condition, meaning that they cannot fundamentally reverse IVDD or restore the mechanical function of the spine. Nanotechnology and regenerative medicine have made significant advancements in the field of healthcare, particularly in the area of nanodrug delivery systems (NDDSs). These approaches have demonstrated significant potential in enhancing the efficacy of IVDD treatments by providing benefits such as high biocompatibility, biodegradability, precise drug delivery to targeted areas, prolonged drug release, and improved therapeutic results. The advancements in different NDDSs designed for delivering various genes, cells, proteins and therapeutic drugs have opened up new opportunities for effectively addressing IVDD. This comprehensive review provides a consolidated overview of the recent advancements in the use of NDDSs for the treatment of IVDD. It emphasizes the potential of these systems in overcoming the challenges associated with this condition. Meanwhile, the insights and ideas presented in this review aim to contribute to the advancement of precise IVDD treatment using NDDSs.

[Effects of Oxidative Stress on Mitochondrial Functions and Intervertebral Disc Cells]

Intervertebral disc degeneration is widely recognized as one of the main causes of lower back pain. Intervertebral disc cells are the primary cellular components of the discs, responsible for synthesizing and secreting collagen and proteoglycans to maintain the structural and functional stability of the discs. Additionally, intervertebral disc cells are involved in maintaining the nutritional and metabolic balance, as well as exerting antioxidant and anti-inflammatory effects within the intervertebral discs. Consequently, intervertebral disc cells play a crucial role in the process of disc degeneration. When these cells are exposed to oxidative stress, mitochondria can be damaged, which may disrupt normal cellular function and accelerate degenerative changes. Mitochondria serve as the powerhouse of cells, being the primary energy-producing organelles that control a number of vital processes, such as cell death. On the other hand, mitochondrial dysfunction may be associated with various degenerative pathophysiological conditions. Moreover, mitochondria are the key site for oxidation-reduction reactions. Excessive oxidative stress and reactive oxygen species can negatively impact on mitochondrial function, potentially leading to mitochondrial damage and impaired functionality. These factors, in turn, triggers inflammatory responses, mitochondrial DNA damage, and cell apoptosis, playing a significant role in the pathological processes of intervertebral disc cell degeneration. This review is focused on exploring the impact of oxidative stress and reactive oxygen species on mitochondria and the crucial roles played by oxidative stress and reactive oxygen species in the pathological processes of intervertebral disc cells. In addition, we discussed current cutting-edge treatments and introduced the use of mitochondrial antioxidants and protectants as a potential method to slow down oxidative stress in the treatment of disc degeneration.

Rescuing Nucleus Pulposus Cells from ROS Toxic Microenvironment via Mitochondria-Targeted Carbon Dot-Supported Prussian Blue to Alleviate Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is invariably accompanied by excessive accumulation of reactive oxygen species (ROS), resulting in progressive deterioration of mitochondrial function and senescence in nucleus pulposus cells (NPCs). Significantly, the main ROS production site in non-immune cells is mitochondria, suggesting mitochondria is a feasible therapeutic target to reverse IVDD. Triphenylphosphine (TPP), which is known as mitochondrial-tropic ligands, is utilized to modify carbon dot-supported Prussian blue (CD-PB) to scavenge superfluous intro-cellular ROS and maintain NPCs at normal redox levels. CD-PB-TPP can effectively escape from lysosomal phagocytosis, permitting efficient mitochondrial targeting. After strikingly lessening the ROS in mitochondria via exerting antioxidant enzyme-like activities, such as superoxide dismutase, and catalase, CD-PB-TPP rescues damaged mitochondrial function and NPCs from senescence, catabolism, and inflammatory reaction in vitro. Imaging evaluation and tissue morphology assessment in vivo suggest that disc height index, mean grey values of nucleus pulposus tissue, and histological morphology are significantly improved in the IVDD model after CD-PB-TPP is locally performed. In conclusion, this study demonstrates that ROS-induced mitochondrial dysfunction and senescence of NPCs leads to IVDD and the CD-PB-TPP possesses enormous potential to rescue this pathological process through efficient removal of ROS via targeting mitochondria, supplying a neoteric strategy for IVDD treatment.

Therapeutic factors and biomaterial-based delivery tools for degenerative intervertebral disc repair

Intervertebral disc degeneration (IDD) is the main cause of low back pain (LBP), which significantly impacts global wellbeing and contributes to global productivity declines. Conventional treatment approaches, encompassing conservative and surgical interventions, merely serve to postpone the advancement of IDD without offering a fundamental reversal. Consequently, there is an urgent demand for an effective approach to prevent the progression of IDD. Recent investigations focusing on the treatment of IDD utilizing diverse bioactive substances integrated within various biomaterials have exhibited promising outcomes. Various bioactive substances, encompassing conventional small molecule drugs, small molecule nucleic acids, and cell therapies, exhibit distinct capacities for repairing IDD. Additionally, various biological material delivery systems, such as nano micelles, microspheres, and hydrogels, possess diverse biological and release characteristics. Consequently, these diverse materials and drugs hold promise for advancing the treatment of IDD. This article aims to provide a concise overview of the IDD process and investigate the research advancements in biomaterials and bioactive substances for IDD treatment, delving into their mechanisms.

SEPHS1 attenuates intervertebral disc degeneration by delaying nucleus pulposus cell senescence through the Hippo-Yap/Taz pathway

Nucleus pulposus cell (NPC) senescence is a major cause of intervertebral disc degeneration (IVDD). Oxidative stress and reactive oxygen species (ROS) play critical roles in regulating cell senescence. Selenophosphate synthetase 1 (SEPHS1) was reported to play an important role in mitigating oxidative stress in an osteoarthritis (OA) model by reducing the production of ROS, thereby, delaying the occurrence and development of osteoarthritis. In this study, we explored the, hitherto unknown, role of SEPHS1 in IVDD in vitro and in vivo using an interleukin-1β (IL-1β)-induced NPC senescence model and a rat needle puncture IVDD model, respectively. SEPHS1 delayed NPC senescence in vitro by reducing ROS production. Age-related dysfunction was also ameliorated by the overexpression of SEPHS1 and inhibition of the Hippo-Yap/Taz signaling pathway. In vivo experiments revealed that the overexpression of SEPHS1 and inhibition of Hippo-Yap/Taz alleviated IVDD in rats. Moreover, a selenium (Se)-deficient diet and lack of SEPHS1 synergistically aggravated IVDD progression. Taken together, our results demonstrate that SEPHS1 plays a significant role in NPC senescence. Overexpression of SEPHS1 and inhibition of Hippo-Yap/Taz can delay NPC senescence, restore the balance of extracellular matrix metabolism, and attenuate IVDD. SEPHS1 could be a promising therapeutic target for IVDD.NEW & NOTEWORTHY Selenophosphate synthetase 1 (SEPHS1) deficiency leads to an increase in reactive oxygen species levels and in the subsequent activation of the Hippo-Yap/Taz signaling pathway. In the rat model of intervertebral disc degeneration (IVDD), overexpression of SEPHS1 and inhibition of Hippo-YAP/Taz mitigated the progression of disc degeneration indicating the involvement of SEPHS1 in IVDD. SEPHS1 is a promising therapeutic target for IVDD.

Supramolecular self-assembly of EGCG-selenomethionine nanodrug for treating osteoarthritis

Osteoarthritis (OA) has emerged as a significant health concern among the elderly population, with increasing attention paid to ferroptosis-induced OA in recent years. However, the prolonged use of nonsteroidal anti-inflammatory drugs or corticosteroids can lead to a series of side effects and limited therapeutic efficacy. This study aimed to employ the Mannich condensation reaction between epigallocatechin-3-gallate (EGCG) and selenomethionine (SeMet) to efficiently synthesize polyphenol-based nanodrugs in aqueous media for treating OA. Molecular biology experiments demonstrated that EGCG-based nanodrugs (ES NDs) could effectively reduce glutathione peroxidase 4 (GPX4) inactivation, abnormal Fe2+ accumulation, and lipid peroxidation induced by oxidative stress, which ameliorated the metabolic disorder of chondrocytes and other multiple pathological processes triggered by ferroptosis. Moreover, imaging and histopathological analysis of the destabilization of the medial meniscus model in mice confirmed that ES NDs exhibiting significant therapeutic effects in relieving OA. The intra-articular delivery of ES NDs represents a promising approach for treating OA and other joint inflammatory diseases.

How to enhance the ability of mesenchymal stem cells to alleviate intervertebral disc degeneration

Intervertebral disc (ID) degeneration (IDD) is one of the main causes of chronic low back pain, and degenerative lesions are usually caused by an imbalance between catabolic and anabolic processes in the ID. The environment in which the ID is located is harsh, with almost no vascular distribution within the disc, and the nutrient supply relies mainly on the diffusion of oxygen and nutrients from the blood vessels located under the endplate. The stability of its internal environment also plays an important role in preventing IDD. The main feature of disc degeneration is a decrease in the number of cells. Mesenchymal stem cells have been used in the treatment of disc lesions due to their ability to differentiate into nucleus pulposus cells in a nonspecific anti-inflammatory manner. The main purpose is to promote their regeneration. The current aim of stem cell therapy is to replace the aged and metamorphosed cells in the ID and to increase the content of the extracellular matrix. The treatment of disc degeneration with stem cells has achieved good efficacy, and the current challenge is how to improve this efficacy. Here, we reviewed current treatments for disc degeneration and summarize studies on stem cell vesicles, enhancement of therapeutic effects when stem cells are mixed with related substances, and improvements in the efficacy of stem cell therapy by adjuvants under adverse conditions. We reviewed the new approaches and ideas for stem cell treatment of disc degeneration in order to contribute to the development of new therapeutic approaches to meet current challenges.

Enhanced Mitochondrial Targeting and Inhibition of Pyroptosis with Multifunctional Metallopolyphenol Nanoparticles in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is a significant contributor to low back pain, characterized by excessive reactive oxygen species generation and inflammation-induced pyroptosis. Unfortunately, there are currently no specific molecules or materials available to effectively delay IVDD. This study develops a multifunctional full name of PG@Cu nanoparticle network (PG@Cu). A designed pentapeptide, bonded on PG@Cu nanoparticles via a Schiff base bond, imparts multifunctionality to the metal polyphenol particles (PG@Cu-FP). PG@Cu-FP exhibits enhanced escape from lysosomal capture, enabling efficient targeting of mitochondria to scavenge excess reactive oxygen species. The scavenging activity against reactive oxygen species originates from the polyphenol-based structures within the nanoparticles. Furthermore, Pyroptosis is effectively blocked by inhibiting Gasdermin mediated pore formation and membrane rupture. PG@Cu-FP successfully reduces the activation of the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 inflammasome by inhibiting Gasdermin protein family (Gasdermin D, GSDMD) oligomerization, leading to reduced expression of Nod-like receptors. This multifaceted approach demonstrates higher efficiency in inhibiting Pyroptosis. Experimental results confirm that PG@Cu-FP preserves disc height, retains water content, and preserves tissue structure. These findings highlight the potential of PG@Cu-FP in improving IVDD and provide novel insights for future research in IVDD treatments.

Tert-butyl hydroperoxide induces ferroptosis of bone mesenchymal stem cells by repressing the prominin2/BACH1/ROS axis

Ferroptosis has been proven critical for survival following bone marrow mesenchymal stem cells (BMSCs) explantation. Suppression of ferroptosis in BMSCs will be a valid tactic to elevate the therapeutic potential of engrafted BMSCs. Prominin2 is a pentaspanin protein involved in mediating iron efflux and thus modulates resistance to ferroptosis, but its role in tert-butyl hydroperoxide (TBHP)-induced BMSCs ferroptosis remains elusive. We examined the biological effect of prominin2 in vitro and in vivo by using cell proliferation assay, iron assay, reactive oxygen species (ROS) examination, malondialdehyde assay, glutathione (GSH) examination, Western blot, quantitative reverse transcription-PCR, immunofluorescence staining assay, gene expression inhibition and activation, co-immunoprecipitation (CO-IP) assay, radiographic analysis, and histopathological analysis. Our study demonstrated that prominin2 activity was impaired in TBHP-induced BMSCs ferroptosis. We found that PROM2 (encoding the protein prominin2) activation delayed the onset of ferroptosis and PROM2 knockdown deteriorated the course of ferroptosis. CO-IP, Western blot, and immunofluorescence demonstrated that prominin2 exerts antiferroptosis effects by inhibiting BTB and CNC homology 1 (BACH1) that promotes ROS generation, and thus exerts potent antioxidant effects in oxidative stress (OS)-induced BMSCs ferroptosis, including elevating BMSCs' survival rate and enhancing GSH contents. BMSCs with PROM2 overexpression also partially delayed the progression of intervertebral disk degeneration in vivo, as illustrated by less loss of disk height and lower histological scores. Our findings revealed a mechanism that the prominin2/BACH1/ROS axis participates in BMSCs ferroptosis and the strengthening of this axis is promising to maintain BMSCs' survival after explantation.NEW & NOTEWORTHY We found that prominin2 might be a potential biomarker and is expected to be utilized to augment engrafted bone marrow mesenchymal stem cells (BMSCs) survival rate. The prominin2/BTB and CNC homology 1 (BACH1)/reactive oxygen species (ROS) axis, which participates in the regulation of BMSCs ferroptosis induced by tert-butyl hydroperoxide (TBHP), is uncovered in our study. The therapeutic targeting of the prominin2/BACH1/ROS axis components is promising to elevate the survival of transplanted BMSCs in clinical practice.

A Review: Methodologies to Promote the Differentiation of Mesenchymal Stem Cells for the Regeneration of Intervertebral Disc Cells Following Intervertebral Disc Degeneration

Intervertebral disc (IVD) degeneration (IDD), a highly prevalent pathological condition worldwide, is widely associated with back pain. Treatments available compensate for the impaired function of the degenerated IVD but typically have incomplete resolutions because of their adverse complications. Therefore, fundamental regenerative treatments need exploration. Mesenchymal stem cell (MSC) therapy has been recognized as a mainstream research objective by the World Health Organization and was consequently studied by various research groups. Implanted MSCs exert anti-inflammatory, anti-apoptotic, and anti-pyroptotic effects and promote extracellular component production, as well as differentiation into IVD cells themselves. Hence, the ultimate goal of MSC therapy is to recover IVD cells and consequently regenerate the extracellular matrix of degenerated IVDs. Notably, in addition to MSC implantation, healthy nucleus pulposus (NP) cells (NPCs) have been implanted to regenerate NP, which is currently undergoing clinical trials. NPC-derived exosomes have been investigated for their ability to differentiate MSCs from NPC-like phenotypes. A stable and economical source of IVD cells may include allogeneic MSCs from the cell bank for differentiation into IVD cells. Therefore, multiple alternative therapeutic options should be considered if a refined protocol for the differentiation of MSCs into IVD cells is established. In this study, we comprehensively reviewed the molecules, scaffolds, and environmental factors that facilitate the differentiation of MSCs into IVD cells for regenerative therapies for IDD.