Bone marrow mesenchymal stem cells combined with ultra-purified alginate gel as a regenerative therapeutic strategy after discectomy for degenerated intervertebral discs

Identification and Validation of Circadian Rhythm-Related Genes Involved in Intervertebral Disc Degeneration and Analysis of Immune Cell Infiltration via Machine Learning

Background

Low back pain is a significant burden worldwide, and intervertebral disc degeneration (IVDD) is identified as the primary cause. Recent research has emphasized the significant role of circadian rhythms (CRs) and immunity in affecting intervertebral discs (IVD). However, the influence of circadian rhythms and immunity on the mechanism of IVDD remains unclear. This study aimed to identify and validate key rhythm-related genes in IVDD and analyze their correlation with immune cell infiltration.

Methods

Two gene expression profiles related to IVDD and rhythm-related genes were obtained from the Gene Expression Omnibus and GeneCards databases to identify differentially expressed rhythm-related genes (DERGs). Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene set enrichment analysis (GSEA) were conducted to explore the biological functions of these genes. LASSO regression and SVM algorithms were employed to identify hub genes. We subsequently investigated the correlation between hub rhythm-related genes and immune cell infiltration. Finally, nucleus pulposus-derived mesenchymal stem cells (NPMSCs) were isolated from normal and degenerative human IVD tissues. Hub rhythm-related genes expression in NPMSCs was confirmed by real-time quantitative PCR (RT-qPCR).

Results

Six hub genes related to CRs (CCND1, FOXO1, FRMD8, NTRK2, PRRT1, and TFPI) were screened out. Immune infiltration analysis revealed that the IVDD group had significantly more M0 macrophages and significantly fewer follicular helper T cells than those of the control group. Specifically, M0 macrophages were significantly associated with FRMD8, PRRT1, and TFPI. T follicular helper cells were significantly associated with FRDM8, FOXO1, and CCND1. We further confirmed that CCND1, FRMD8, NTRK2, and TFPI were dysrhythmic within NPMSCs from degenerated IVD in vitro.

Conclusion

Six genes (CCND1, FOXO1, FRMD8, NTRK2, PRRT1 and TFPI) linked to circadian rhythms associated with IVDD progression, together with immunity. The identification of these DEGs may provide new insights for the diagnosis and treatment of IVDD.

Research progress on intervertebral disc repair strategies and mechanisms based on hydrogel

Intervertebral disc degeneration (IDD) arises from a complex interplay of genetic, environmental, and age-related factors, culminating in a spectrum of low back pain (LBP) disorders that exert significant societal and economic impact. The present therapeutic landscape for IDD poses formidable clinical hurdles, necessitating the exploration of innovative treatment modalities. The hydrogel, as a biomaterial, exhibits superior biocompatibility compared to other biomaterials such as bioceramics and bio-metal materials. It also demonstrates mechanical properties closer to those of natural intervertebral discs (IVDs) and favorable biodegradability conducive to IVD regeneration. Therefore, it has emerged as a promising candidate material in the field of regenerative medicine and tissue engineering for treating IDD. Hydrogels have made significant strides in the field of IDD treatment. Particularly, injectable hydrogels not only provide mechanical support but also enable controlled release of bioactive molecules, playing a crucial role in mitigating inflammation and promoting extracellular matrix (ECM) regeneration. Furthermore, the ability of injectable hydrogels to achieve minimally invasive implantation helps minimize tissue damage. This article initially provides a concise exposition of the structure and function of IVD, the progression of IDD, and delineates extant clinical interventions for IDD. Subsequently, it categorizes hydrogels, encapsulates recent advancements in biomaterials and cellular therapies, and delves into the mechanisms through which hydrogels foster disc regeneration. Ultimately, the article deliberates on the prospects and challenges attendant to hydrogel therapy for IDD.

Targeting prominin-2/BACH1/GLS pathway to inhibit oxidative stress-induced ferroptosis of bone mesenchymal stem cells

Suppressing bone mesenchymal stem cell (BMSC) ferroptosis is expected to optimize BMSCs-based therapy for intervertebral disc degeneration (IVDD). Our previous study revealed that Prominin-2 could protect against ferroptosis by decreasing cellular Fe2+ content and inhibiting transcription regulator protein BACH1 (BACH1) expression. In this study we probed the molecular mechanisms underlying the Prominin-2/BACH1 pathway in BMSC ferroptosis. Using an array of in vitro and in vivo experiments we found that heat shock factor protein 1 (HSF1) activates PROM2 (encoding protein Prominin-2) transcription and elevated Prominin-2 expression. Furthermore, we showed that Prominin-2 attenuates ferroptosis induced by tert-butyl hydroperoxide (TBHP) through promoting BACH1 ubiquitination and degradation. Inhibition of BACH1 expression reversed TBHP-stimulated down expression of glutaminase kidney isoform, mitochondrial (GLS), which plays a crucial role in protecting BMSCs against ferroptosis. Targeting the Prominin-2/BACH1 axis has also been shown to improve BMSC survival post-transplantation and mitigate IVDD progression by inhibiting ferroptosis. Our results support a new mechanistic insight into the regulation of the Prominin-2/BACH1/GLS pathway in BMSC ferroptosis. These finding could lead to potential therapeutic targets to improve the survival of engrafted BMSCs under oxidative stress circumstances.

Three-Dimensional Bioprinting for Intervertebral Disc Regeneration

The rising demand for organ transplants and the need for precise tissue models have positioned the in vitro biomanufacturing of tissues and organs as a pivotal area in regenerative treatment. Considerable development has been achieved in growing tissue-engineered intervertebral disc (IVD) scaffolds, designed to meet stringent mechanical and biological compatibility criteria. Among the cutting-edge approaches, 3D bioprinting stands out due to its unparalleled capacity to organize biomaterials, bioactive molecules, and living cells with high precision. Despite these advancements, polymer-based scaffolds still encounter limitations in replicating the extracellular matrix (ECM)-like environment, which is fundamental for optimal cellular activities. To overcome these challenges, integrating polymers with hydrogels has been recommended as a promising solution. This combination enables the advancement of porous scaffolds that nurture cell adhesion, proliferation, as well as differentiation. Additionally, bioinks derived from the decellularized extracellular matrix (dECM) have exhibited potential in replicating biologically relevant microenvironments, enhancing cell viability, differentiation, and motility. Hydrogels, whether derived from natural sources involving collagen and alginate or synthesized chemically, are highly valued for their ECM-like properties and superior biocompatibility. This review will explore recent advancements in techniques and technologies for IVD regeneration. Emphasis will be placed on identifying research gaps and proposing strategies to bridge them, with the goal of accelerating the translation of IVDs into clinical applications.

CircSPG21 ameliorates oxidative stress-induced senescence in nucleus pulposus-derived mesenchymal stem cells and mitigates intervertebral disc degeneration through the miR-217/SIRT1 axis and mitophagy

BACKGROUND

The microenvironment of intervertebral disc degeneration (IVDD) is characterized by oxidative stress, leading to the senescence of nucleus pulposus-derived mesenchymal stem cells (NPMSCs). The purpose of this study was to investigate the competitive endogenous RNA mechanism involved in the senescence of NPMSCs induced by tert-butyl hydroperoxide (TBHP).

METHODS

Bioinformatic analysis identified differentially expressed circRNAs. Interactions among circSPG21, miR-217, and the NAD-dependent protein deacetylase sirtuin-1 (SIRT1) were validated through dual-luciferase assays, RNA fluorescence in situ hybridization and RNA immune precipitation. β-Gal staining, EdU staining, Western blotting, JC-1 assays, cell cycle analysis, and quantitative reverse transcription PCR (RT‒qPCR) were used to examine the functions of these molecules in TBHP-induced senescent NPMSCs. The therapeutic effects of circSPG21 were evaluated in a rat IVDD model.

RESULTS

CircSPG21 expression was significantly decreased in both human and rat IVDD tissues, whereas miR-217 was upregulated and SIRT1 was downregulated. Overexpression of circSPG21 alleviated NPMSC senescence by reducing P21 and P53 levels and restoring mitophagy through Parkin. The protective effects of circSPG21 were mediated through the miR-217/SIRT1 axis, as SIRT1 knockdown attenuated these benefits. CircSPG21 also ameliorated disc degeneration in the IVDD rat model, highlighting its potential as a therapeutic target.

CONCLUSION

CircSPG21 reduces oxidative stress-induced NPMSC senescence through the miR-217/SIRT1 axis and mitophagy, providing new insights into IVDD and identifying circSPG21 as a potential therapeutic target for disc degeneration.

Polysaccharide-based biomaterials for regenerative therapy in intervertebral disc degeneration

Intervertebral disc (IVD) degeneration represents a significant cause of chronic back pain and disability, with a substantial impact on the quality of life. Conventional therapeutic modalities frequently address the symptoms rather than the underlying etiology, underscoring the necessity for regenerative therapies that restore disc function. Polysaccharide-based materials, such as hyaluronic acid, alginate, chitosan, and chondroitin sulfate, have emerged as promising candidates for intervertebral disc degeneration (IVDD) therapy due to their biocompatibility, biodegradability, and ability to mimic the native extracellular matrix (ECM) of the nucleus pulposus (NP). These materials have demonstrated the capacity to support cell viability, facilitate matrix production, and alleviate inflammation in vitro and in vivo, thus supporting tissue regeneration and restoring disc function in comparison to conventional treatment. Furthermore, polysaccharide-based hydrogels have demonstrated the potential to deliver bioactive molecules, including growth factors, cytokines and anti-inflammatory drugs, directly to the degenerated disc environment, thereby enhancing therapeutic outcomes. Therefore, polysaccharide-based materials provide structural support and facilitate the regeneration of native tissue, representing a versatile and effective approach for the treatment of IVDD. Despite their promise, challenges such as limited long-term stability, potential immunogenicity, and the difficulty in scaling up production for clinical use remain. This review delineates the potential of various polysaccharides during the fabrication of hydrogels and scaffolds for disc regeneration, guiding and inspiring future research to focus on optimizing these materials for clinical translation for IVDD repair and regeneration.

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.

Alginate vs. Hyaluronic Acid as Carriers for Nucleus Pulposus Cells: A Study on Regenerative Outcomes in Disc Degeneration

Intervertebral disc degeneration is a leading cause of chronic low back pain, affecting millions globally. Regenerative medicine, particularly cell-based therapies, presents a promising therapeutic strategy. This study evaluates the comparative efficacy of two biomaterials-hyaluronic acid (HA) and alginate-as carriers for nucleus pulposus (NP) cell transplantation in a beagle model of induced disc degeneration. NP cells were isolated, cultured, and injected with either HA or alginate into degenerated discs, with saline and non-cell-loaded carriers used as controls. Disc height index, T2-weighted MRI, and histological analyses were conducted over a 12-week follow-up period to assess reparative outcomes. Imaging revealed that both carrier and cell-loaded treatments improved outcomes compared to degenerative controls, with cell-loaded carriers consistently outperforming carrier-only treated discs. Histological assessments supported these findings, showing trends toward extracellular matrix restoration in both treatment groups. While both biomaterials demonstrated reparative potential, HA showed greater consistency in supporting NP cells in promoting disc regeneration. These results underscore HA's potential as a superior carrier for NP cell-based therapies in addressing disc degeneration.

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.

Bone Marrow Aspirate Concentrate Combined with Ultra-Purified Alginate Bioresorbable Gel Enhances Intervertebral Disc Repair in a Canine Model: A Preclinical Proof-of-Concept Study

Although discectomy is commonly performed for lumbar intervertebral disc (IVD) herniation, the capacity for tissue repair after surgery is limited, resulting in residual lower back pain, recurrence of IVD herniation, and progression of IVD degeneration. Cell-based therapies, as one-step procedures, are desirable for enhancing IVD repair. This study aimed to investigate the therapeutic efficacy of a combination of newly developed ultra-purified alginate (UPAL) gel and bone marrow aspirate concentrate (BMAC) implantation for IVD repair after discectomy. Prior to an in vivo study, the cell concentration abilities of three commercially available preparation kits for creating the BMAC were compared by measuring the number of bone marrow mesenchymal stem cells harvested from the bone marrow of rabbits. Subsequently, canine-derived BMAC was tested in a canine model using a kit which had the highest concentration rate. At 24 weeks after implantation, we evaluated the changes in the magnetic resonance imaging (MRI) signals as well as histological degeneration grade and immunohistochemical analysis results for type II and type I collagen-positive cells in the treated IVDs. In all quantitative evaluations, such as MRI and histological and immunohistochemical analyses of IVD degeneration, BMAC-UPAL implantation significantly suppressed the progression of IVD degeneration compared to discectomy and UPAL alone. This preclinical proof-of-concept study demonstrated the potential efficacy of BMAC-UPAL gel as a therapeutic strategy for implementation after discectomy, which was superior to UPAL and discectomy alone in terms of tissue repair and regenerative potential.

Menstrual blood-derived mesenchymal stem cells combined with collagen I gel as a regenerative therapeutic strategy for degenerated disc after discectomy in rats

BACKGROUND

Annulus fibrosis (AF) defects have been identified as the primary cause of disc herniation relapse and subsequent disc degeneration following discectomy. Stem cell-based tissue engineering offers a promising approach for structural repair. Menstrual blood-derived mesenchymal stem cells (MenSCs), a type of adult stem cell, have gained attention as an appealing source for clinical applications due to their potential for structure regeneration, with ease of acquisition and regardless of ethical issues.

METHODS

The differential potential of MenSCs cocultured with AF cells was examined by the expression of collagen I, SCX, and CD146 using immunofluorescence. Western blot and ELISA were used to examine the expression of TGF-β and IGF-I in coculture system. An AF defect animal model was established in tail disc of Sprague-Dawley rats (males, 8 weeks old). An injectable gel containing MenSCs (about 1*106/ml) was fabricated and transplanted into the AF defects immediately after the animal model establishment, to evaluate its repairment properties. Disc degeneration was assessed via magnetic resonance (MR) imaging and histological staining. Immunohistochemical analysis was performed to assess the expression of aggrecan, MMP13, TGF-β and IGF-I in discs with different treatments. Apoptosis in the discs was evaluated using TUNEL, caspase3, and caspase 8 immunofluorescence staining.

RESULTS

Coculturing MenSCs with AF cells demonstrated ability to express collagen I and biomarkers of AF cells. Moreover, the coculture system presented upregulation of the growth factors TGF-β and IGF-I. After 12 weeks, discs treated with MenSCs gel exhibited significantly lower Pffirrmann scores (2.29 ± 0.18), compared to discs treated with MenSCs (3.43 ± 0.37, p < 0.05) or gel (3.71 ± 0.29, p < 0.01) alone. There is significant higher MR index in disc treated with MenSCs gel than that treated with MenSCs (0.51 ± 0.05 vs. 0.24 ± 0.04, p < 0.01) or gel (0.51 ± 0.05 vs. 0.26 ± 0.06, p < 0.01) alone. Additionally, MenSCs gel demonstrated preservation of the structure of degenerated discs, as indicated by histological scoring (5.43 ± 0.43 vs. 9.71 ± 1.04 in MenSCs group and 10.86 ± 0.63 in gel group, both p < 0.01), increased aggrecan expression, and decreased MMP13 expression in vivo. Furthermore, the percentage of TUNEL and caspase 3-positive cells in the disc treated with MenSCs Gel was significantly lower than those treated with gel alone and MenSCs alone. The expression of TGF-β and IGF-I was higher in discs treated with MenSCs gel or MenSCs alone than in those treated with gel alone.

CONCLUSION

MenSCs embedded in collagen I gel has the potential to preserve the disc structure and prevent disc degeneration after discectomy, which was probably attributed to the paracrine of growth factors of MenSCs.

A new strategy for intervertebral disc regeneration: The synergistic potential of mesenchymal stem cells and their extracellular vesicles with hydrogel scaffolds

Intervertebral disc degeneration (IDD) is a disease that severely affects spinal health and is prevalent worldwide. Mesenchymal stem cells (MSCs) and their derived extracellular vesicles (EVs) have regenerative potential and have emerged as promising therapeutic tools for treating degenerative discs. However, challenges such as the harsh microenvironment of degenerated intervertebral discs and EVs' limited stability and efficacy have hindered their clinical application. In recent years, hydrogels have attracted much attention in the field of IDD therapy because they can mimic the physiologic microenvironment of the disc and provide a potential solution by providing a suitable growth environment for MSCs and EVs. This review introduced the biological properties of MSCs and their derived EVs, summarized the research on the application of MSCs and EVs in IDD, summarized the current clinical trial studies of MSCs and EVs, and also explored the mechanism of action of MSCs and EVs in intervertebral discs. In addition, plenty of research elaborated on the mechanism of action of different classified hydrogels in tissue engineering, the synergistic effect of MSCs and EVs in promoting intervertebral disc regeneration, and their wide application in treating IDD. Finally, the challenges and problems still faced by hydrogel-loaded MSCs and EVs in the treatment of IDD are summarized, and potential solutions are proposed. This paper outlines the synergistic effects of MSCs and EVs in treating IDD in combination with hydrogels and aims to provide theoretical references for future related studies.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

Current status and development direction of immunomodulatory therapy for intervertebral disk degeneration

Intervertebral disk (IVD) degeneration (IVDD) is a main factor in lower back pain, and immunomodulation plays a vital role in disease progression. The IVD is an immune privileged organ, and immunosuppressive molecules in tissues reduce immune cell (mainly monocytes/macrophages and mast cells) infiltration, and these cells can release proinflammatory cytokines and chemokines, disrupting the IVD microenvironment and leading to disease progression. Improving the inflammatory microenvironment in the IVD through immunomodulation during IVDD may be a promising therapeutic strategy. This article reviews the normal physiology of the IVD and its degenerative mechanisms, focusing on IVDD-related immunomodulation, including innate immune responses involving Toll-like receptors, NOD-like receptors and the complement system and adaptive immune responses that regulate cellular and humoral immunity, as well as IVDD-associated immunomodulatory therapies, which mainly include mesenchymal stem cell therapies, small molecule therapies, growth factor therapies, scaffolds, and gene therapy, to provide new strategies for the treatment of IVDD.

Melatonin alleviates oxidative stress-induced injury to nucleus pulposus-derived mesenchymal stem cells through activating PI3K/Akt pathway

BACKGROUND

The changes in the microenvironment of degenerative intervertebral discs cause oxidative stress injury and excessive apoptosis of intervertebral disc endogenous stem cells. The purpose of this study was to explore the possible mechanism of the protective effect of melatonin on oxidative stress injury in NPMSCs induced by H2O2.

METHODS

The Cell Counting Kit-8 assay was used to evaluate the cytotoxicity of hydrogen peroxide and the protective effects of melatonin. ROS content was detected by 2'7'-dichlorofluorescin diacetate (DCFH-DA). Mitochondrial membrane potential (MMP) was detected by the JC-1assay. Transferase mediated d-UTP Nick end labeling (TUNEL) and Annexin V/PI double staining were used to determine the apoptosis rate. Additionally, apoptosis-associated proteins and PI3K/Akt signaling pathway-related proteins were evaluated by immunofluorescence, immunoblotting and PCR. ECMs were evaluated by RT‒PCR and immunofluorescence. In vivo, X-ray, Magnetic resonance imaging (MRI) and Histological analyses were used to evaluate the protective effect of melatonin.

RESULTS

Melatonin had an obvious protective effect on NPMSCs treated with 0-10 μM melatonin for 24 h. In addition, melatonin also had obvious protective effects on mitochondrial dysfunction, decreased membrane potential and cell senescence induced by H2O2. More importantly, melatonin could significantly reduce the apoptosis of nucleus pulposus mesenchymal stem cells induced by H2O2 by regulating the expression of apoptosis-related proteins and decreasing the rate of apoptosis. After treatment with melatonin, the PI3K/Akt pathway was significantly activated in nucleus pulposus mesenchymal stem cells, while the protective effect was significantly weakened after PI3K-IN-1 treatment. In vivo, the results of X-ray, MRI and histological analyses showed that therapy with melatonin could partially reduce the degree of intervertebral disc degeneration.

CONCLUSION

Our research demonstrated that melatonin can effectively alleviate the excessive apoptosis and mitochondrial dysfunction of nucleus pulposus mesenchymal stem cells induced by oxidative stress via the PI3K/Akt pathway, which provides a novel idea for the therapy of intervertebral disc degeneration.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

This study indicates that melatonin can effectively alleviate the excessive apoptosis and mitochondrial dysfunction of NPMSCs through activating the PI3K/Akt pathway. Melatonin might serve as a promising candidate for the prevention and treatment of Intervertebral disc degeneration disease (IVDD) in the future.

Silk-hydrogel functionalized with human decellularized Wharton's jelly extracellular matrix as a minimally invasive injectable hydrogel system for potential nucleus pulposus tissue replacement therapy

Intervertebral disc degeneration is a primary cause for chronic low back pain, a common health problem with high incidence and the leading cause of disability globally. The early stages of disc degeneration in terms of functional and anatomical abnormalities start from the central nucleus pulposus tissue of the intervertebral disc; hence its regeneration has become a prime concern. A plethora of hydrogel systems have been investigated as nucleus pulposus tissue substitute over the years, with limited clinical translation. In the present study, we formulated a minimally invasive injectable cross-linker-free bioactive silk-based hybrid hydrogel system functionalized with decellularized human Wharton's jelly extracellular matrix as an ampule of bioactive cues. The centrifugation based decellularization method removed >92 % of cellular components and preserved >83 % of extracellular matrix composition. The hydrogels were investigated for secondary structure and surface properties through infrared spectroscopy and electron micrographs, respectively. Notably, the developed hydrogels were found to mimic the rheological and mechanical properties of native nucleus pulposus tissue when decellularized Wharton's jelly extracellular matrix content was 0.5 % (w/v) in the base silk hydrogel. Finally, the hydrogels were found to support cell viability, proliferation, and tissue maturation offering great potential for future applications related to nucleus pulposus tissue engineering.

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.

Alginate hydrogels: A potential tissue engineering intervention for intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a major cause of low back pain and disability, affecting millions of people worldwide. Current treatments for IVD degeneration are limited to invasive surgery or pain management. Recently, there has been increasing interest in the use of biomaterials, such as alginate hydrogels, for the treatment of IVD degeneration. Alginate hydrogels are an example of such a biomaterial that is biocompatible and can be tailored to mimic the native extracellular matrix of the IVD. Derived from alginate, a naturally derived polysaccharide from brown seaweed that can be transformed into a gelatinous solution, alginate hydrogels are emerging in the field of tissue engineering. They can be used to deliver therapeutic agents, such as growth factors or cells, to the site of injury, providing a localized and sustained release that may enhance treatment outcomes. This paper provides an overview on the use of alginate hydrogels for the treatment of IVD degeneration. We discuss the properties of alginate hydrogels and their potential applications for IVD regeneration, including the mechanism against IVD degeneration. We also highlight the research outcomes to date along with the challenges and limitations of using alginate hydrogels for IVD regeneration, including their mechanical properties, biocompatibility, and surgical compatibility. Overall, this review paper aims to provide a comprehensive overview of the current research on alginate hydrogels for IVD degeneration and to identify future directions for research in this area.

Kartogenin-loaded hydrogel promotes intervertebral disc repair via protecting MSCs against reactive oxygen species microenvironment by Nrf2/TXNIP/NLRP3 axis

Intervertebral disc (IVD) degeneration (IDD) and the consequent low back pain present a major medical challenge. Stem cell-based tissue engineering is promising for the treatment of IDD. However, stem cell-based treatment is severely impaired by the increased generation of reactive oxygen species (ROS) in degenerative disc, which can lead to a high level of cell dysfunction and even death. In this study, a kartogenin (KGN)@PLGA-GelMA/PRP composite hydrogel was designed and used as a carrier of ADSCs-based therapies in disc repair. Injectable composite hydrogel act as a carrier for controlled release of KGN and deliver ADSCs to the degenerative disc. The released KGN can stimulate the differentiation of ADSCs into a nucleus pulposus (NP) -like phenotype and boost antioxidant capacity of ADSCs via activating Nrf2/TXNIP/NLRP3 axis. Furthermore, the composite hydrogel combined with ADSCs attenuated the in vivo degeneration of rat IVDs, maintained IVD tissue integrity and accelerated the synthesis of NP-like extracellular matrix. Therefore, the KGN@PLGA-GelMA/PRP composite hydrogel is a promising strategy for stem cell-based therapies of IDD.

Injection of Ultra-Purified Stem Cells with Sodium Alginate Reduces Discogenic Pain in a Rat Model

Intervertebral disc (IVD) degeneration is a major cause of low back pain. However, treatments directly approaching the etiology of IVD degeneration and discogenic pain are not yet established. We previously demonstrated that intradiscal implantation of cell-free bioresorbable ultra-purified alginate (UPAL) gel promotes tissue repair and reduces discogenic pain, and a combination of ultra-purified, Good Manufacturing Practice (GMP)-compliant, human bone marrow mesenchymal stem cells (rapidly expanding clones; RECs), and the UPAL gel increasingly enhanced IVD regeneration in animal models. This study investigated the therapeutic efficacy of injecting a mixture of REC and UPAL non-gelling solution for discogenic pain and IVD regeneration in a rat caudal nucleus pulposus punch model. REC and UPAL mixture and UPAL alone suppressed not only the expression of TNF-α, IL-6, and TrkA (p < 0.01, respectively), but also IVD degeneration and nociceptive behavior compared to punching alone (p < 0.01, respectively). Furthermore, REC and UPAL mixture suppressed these expression levels and nociceptive behavior compared to UPAL alone (p < 0.01, respectively). These results suggest that this minimally invasive treatment strategy with a single injection may be applied to treat discogenic pain and as a regenerative therapy.

Protocol for treating lumbar spinal canal stenosis with a combination of ultrapurified, allogenic bone marrow-derived mesenchymal stem cells and in situ-forming gel: a multicentre, prospective, double-blind randomised controlled trial

INTRODUCTION

In patients with combined lumbar spinal canal stenosis (LSCS), a herniated intervertebral disc (IVD) that compresses the dura mater and nerve roots is surgically treated with discectomy after laminoplasty. However, defects in the IVD after discectomy may lead to inadequate tissue healing and predispose patients to the development of IVD degeneration. Ultrapurified stem cells (rapidly expanding clones (RECs)), combined with an in situ-forming bioresorbable gel (dMD-001), have been developed to fill IVD defects and prevent IVD degeneration after discectomy. We aim to investigate the safety and efficacy of a new treatment method in which a combination of REC and dMD-001 is implanted into the IVD of patients with combined LSCS.

METHODS AND ANALYSIS

This is a multicentre, prospective, double-blind randomised controlled trial. Forty-five participants aged 20-75 years diagnosed with combined LSCS will be assessed for eligibility. After performing laminoplasty and discectomy, participants will be randomised 1:1:1 into the combination of REC and dMD-001 (REC-dMD-001) group, the dMD-001 group or the laminoplasty and discectomy alone (control) group. The primary outcomes of the trial will be the safety and effectiveness of the procedure. The effectiveness will be assessed using visual analogue scale scores of back pain and leg pain as well as MRI-based estimations of morphological and compositional quality of the IVD tissue. Secondary outcomes will include self-assessed clinical scores and other MRI-based estimations of compositional quality of the IVD tissue. All evaluations will be performed at baseline and at 1, 4, 12, 24 and 48 weeks after surgery.

ETHICS AND DISSEMINATION

This study was approved by the ethics committees of the institutions involved. We plan to conduct dissemination of the outcome data by presenting our data at national and international conferences, as well as through formal publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

jRCT2013210076.

Application of stem cells combined with biomaterial in the treatment of intervertebral disc degeneration

As the world population is aging, intervertebral disc degeneration (IDD) is becoming a global health issue of increasing concern. A variety of disc degeneration diseases (DDDs) have been proven to be associated with IDD, and these illnesses have significant adverse effects on both individuals and society. The application of stem cells in regenerative medicine, such as blood and circulation, has been demonstrated by numerous studies. Similarly, stem cells have made exciting progress in the treatment of IDD. However, due to complex anatomical structures and functional requirements, traditional stem cell injection makes it difficult to meet people's expectations. With the continuous development of tissue engineering and biomaterials, stem cell combined with biomaterials has far more prospects than before. This review aims to objectively and comprehensively summarize the development of stem cells combined with contemporary biomaterials and the difficulties that need to be overcome.

New strategies for the treatment of intervertebral disc degeneration: cell, exosome, gene, and tissue engineering

Low back pain (LBP) caused by intervertebral disc (IVD) generation (IVDD) has always been an important problem that cannot be ignored. Traditional therapies have many deep-rooted and intractable complications that promote their treatment mode transfer to new therapies. This article mainly summarizes the shortcomings of traditional treatment methods and analyzes the research status and future development direction of IVDD treatment. We outlined the most promising IVDD therapies, including cell, exosome, gene, and tissue engineering therapy, especially tissue engineering therapy, which runs through the whole process of other therapies. In addition, the article focuses on the cellular, animal, and preclinical challenges faced by each therapeutic approach, as well as their respective advantages and disadvantages, to provide better ideas for relieving the IVDD patients' pain through new treatment methods.

Targeting Ferroptosis Holds Potential for Intervertebral Disc Degeneration Therapy

Intervertebral disc degeneration (IVDD) is a common pathological condition responsible for lower back pain, which can significantly increase economic and social burdens. Although considerable efforts have been made to identify potential mechanisms of disc degeneration, the treatment of IVDD is not satisfactory. Ferroptosis, a recently reported form of regulated cell death (RCD), is characterized by iron-dependent lipid peroxidation and has been demonstrated to be responsible for a variety of degenerative diseases. Accumulating evidence suggests that ferroptosis is implicated in IVDD by decreasing viability and increasing extracellular matrix degradation of nucleus pulposus cells, annulus fibrosus cells, or endplate chondrocytes. In this review, we summarize the literature regarding ferroptosis of intervertebral disc cells and discuss its molecular pathways and biomarkers for treating IVDD. Importantly, ferroptosis is verified as a promising therapeutic target for IVDD.

Targeting Autophagy for Developing New Therapeutic Strategy in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is a prevalent cause of low back pain. IVDD is characterized by abnormal expression of extracellular matrix components such as collagen and aggrecan. In addition, it results in dysfunctional growth, senescence, and death of intervertebral cells. The biological pathways involved in the development and progression of IVDD are not fully understood. Therefore, a better understanding of the molecular mechanisms underlying IVDD could aid in the development of strategies for prevention and treatment. Autophagy is a cellular process that removes damaged proteins and dysfunctional organelles, and its dysfunction is linked to a variety of diseases, including IVDD and osteoarthritis. In this review, we describe recent research findings on the role of autophagy in IVDD pathogenesis and highlight autophagy-targeting molecules which can be exploited to treat IVDD. Many studies exhibit that autophagy protects against and postpones disc degeneration. Further research is needed to determine whether autophagy is required for cell integrity in intervertebral discs and to establish autophagy as a viable therapeutic target for IVDD.

Bone Marrow Mesenchymal Stem Cell-Derived Extracellular Vesicles Carrying circ_0050205 Attenuate Intervertebral Disc Degeneration

Objective

It has been reported that bone marrow mesenchymal stem cells (BMSCs) are a potential source of autologous stem cells to support the nucleus pulposus (NP) regeneration in intervertebral disc degeneration (IDD). Herein, we aim to study the mechanism underlying the effects of BMSC-derived extracellular vesicles (BMSC-EVs) on nucleus pulposus cells (NPCs) in IDD.

Methods

EVs were isolated from BMSCs. An IDD model was surgically established in C57BL/6J mice. NPCs were exposed to tBHP to establish an IDD cell model. RNA sequencing was performed to identify differentially expressed circRNAs in NP tissues harvested from mice with IDD. Interactions among circ_0050205, miR-665, and GPX4 were validated, and different interventions were used to study the roles of these molecules in NPC biological functions.

Results

BMSC-EVs promoted NPC survival and inhibited NPC apoptosis and extracellular matrix (ECM) degradation. circ_0050205 expression was downregulated in the NP tissues of IDD mice, and BMSC-EVs facilitated NPC survival and suppressed ECM degradation in NPCs by transferring circ_0050205. circ_0050205 sponged miR-665 and upregulated GPX4 expression. BMSC-EVs expressing circ_0050205 promoted NPC survival-inhibited ECM degradation in NPCs and alleviated IDD in mice via the miR-665/GPX4 axis.

Conclusion

In conclusion, BMSC-EVs promoted NPC survival-inhibited ECM degradation in NPCs and attenuated IDD progression via the circ_0050205/miR-665/GPX4 axis.

Hybrid Stents Based on Magnetic Hydrogels for Biomedical Applications

Tremendous attention has been given to hydrogels due to their mechanical and physical properties. Hydrogels are promising biomaterials due to their high biocompatibility. Magnetic hydrogels, which are based on hydrogel incorporated magnetic nanoparticles, have been proposed in biomedical applications. The advantages of magnetic hydrogels are that they can easily respond to externally applied magnetic fields and prevent the leakage of magnetic nanoparticles in the surrounding area. Herein, a prototype hybrid stent of magnetic hydrogel was fabricated, characterized, and evaluated for magnetic hyperthermia treatment. First, magnetic hydrogel was produced by a solution of alginate with magnetic nanoparticles in a bath of calcium chloride (5-15 mg mL^-1) in order to achieve the external gelation and optimize the heating rate. The increased concentration (1-8 mg mL^-1) of magnetic nanoparticles inside the hydrogel resulted in almost zero leakage of iron oxide nanoparticles after 15 days, guaranteeing that they can be used safely in biomedical applications. Thus, magnetic hybrid stents, which are based on the magnetic hydrogels, were developed in a simple way and were evaluated both in an agarose phantom model and in an ex vivo tissue sample at 30 mT and 765 kHz magnetic hyperthermia conditions to examine the heating efficiency. In both cases, hyperthermia results indicate excellent heat generation from the hybrid stent and facile temperature control via tuning magnetic nanoparticle concentration (2-8 mg mL^-1). This study can be a promising method that promotes spatially thermal distribution in cancer treatment or restenosis treatment of hollow organs.

1,25(OH)2D3 Mitigates Oxidative Stress-Induced Damage to Nucleus Pulposus-Derived Mesenchymal Stem Cells through PI3K/Akt Pathway

Intervertebral disc degeneration (IVDD) is one of the main causes of low back pain. The local environment of the degenerated intervertebral disc (IVD) increases oxidative stress and apoptosis of endogenous nucleus pulposus-derived mesenchymal stem cells (NPMSCs) and weakens its ability of endogenous repair ability in degenerated IVDs. A suitable concentration of 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) has been certified to reduce oxidative stress and cell apoptosis. The current study investigated the protective effect and potential mechanism of 1,25(OH)₂D₃ against oxidative stress-induced damage to NPMSCs. The present results showed that 1,25(OH)₂D₃ showed a significant protective effect on NPMSCs at a concentration of 10⁻¹⁰ M for 24 h. Protective effects of 1,25(OH)₂D₃ were also exhibited against H₂O₂-induced NPMSC senescence, mitochondrial dysfunction, and reduced mitochondrial membrane potential. The Annexin V/PI apoptosis detection assay, TUNEL assay, immunofluorescence, western blot, and real-time quantitative polymerase chain reaction assay showed that pretreatment with 1,25(OH)₂D₃ could alleviate H₂O₂-induced NPMSC apoptosis, including the apoptosis rate and the expression of proapoptotic-related (Caspase-3 and Bax) and antiapoptotic-related (Bcl-2) proteins. The intracellular expression of p-Akt increased after pretreatment with 1,25(OH)₂D₃. However, these protective effects of 1,25(OH)₂D₃ were significantly decreased after the PI3K/Akt pathway was inhibited by the LY294002 treatment. In vivo, X-ray, MRI, and histological analyses showed that 1,25(OH)₂D₃ treatment relieved the degree of IVDD in Sprague–Dawley rat disc puncture models. In summary, 1,25(OH)₂D₃ efficiently attenuated oxidative stress-induced NPMSC apoptosis and mitochondrial dysfunction via PI3K/Akt pathway and is a promising candidate treatment for the repair of IVDD.

Biomaterials and Cell-Based Regenerative Therapies for Intervertebral Disc Degeneration with a Focus on Biological and Biomechanical Functional Repair: Targeting Treatments for Disc Herniation

Intervertebral disc (IVD) degeneration is a common cause of low back pain and most spinal disorders. As IVD degeneration is a major obstacle to the healthy life of so many individuals, it is a major issue that needs to be overcome. Currently, there is no clinical treatment for the regeneration of degenerated IVDs. However, recent advances in regenerative medicine and tissue engineering suggest the potential of cell-based and/or biomaterial-based IVD regeneration therapies. These treatments may be indicated for patients with IVDs in the intermediate degenerative stage, a point where the number of viable cells decreases, and the structural integrity of the disc begins to collapse. However, there are many biological, biomechanical, and clinical challenges that must be overcome before the clinical application of these IVD regeneration therapies can be realized. This review summarizes the basic research and clinical trials literature on cell-based and biomaterial-based IVD regenerative therapies and outlines the important role of these strategies in regenerative treatment for IVD degenerative diseases, especially disc herniation.

The Proteolysis of ECM in Intervertebral Disc Degeneration

Intervertebral disc (IVD) degeneration (IDD) is a pathological process that commonly occurs throughout the human life span and is a major cause of lower back pain. Better elucidation of the molecular mechanisms involved in disc degeneration could provide a theoretical basis for the development of lumbar disc intervention strategies. In recent years, extracellular matrix (ECM) homeostasis has received much attention due to its relevance to the mechanical properties of IVDs. ECM proteolysis mediated by a variety of proteases is involved in the pathological process of disc degeneration. Here, we discuss in detail the relationship between the IVD as well as the ECM and the role of ECM proteolysis in the degenerative process of the IVD. Targeting ECM proteolysis-associated proteases may be an effective means of intervention in IDD.

Combination of ultra-purified stem cells with an in situ-forming bioresorbable gel enhances intervertebral disc regeneration

Background

Lumbar intervertebral disc (IVD) herniations are associated with significant disability. Discectomy is the conventional treatment option for IVD herniations but causes a defect in the IVD, which has low self-repair ability, thereby representing a risk of further IVD degeneration. An acellular, bioresorbable, and good manufacturing practice (GMP)-compliant in situ-forming gel, which corrects discectomy-associated IVD defects and prevents further IVD degeneration had been developed. However, this acellular matrix-based strategy has certain limitations, particularly in elderly patients, whose tissues have low self-repair ability. The aim of this study was to investigate the therapeutic efficacy of using a combination of newly-developed, ultra-purified, GMP-compliant, human bone marrow mesenchymal stem cells (rapidly expanding clones; RECs) and the gel for IVD regeneration after discectomy in a sheep model of severe IVD degeneration.

Methods

RECs and nucleus pulposus cells (NPCs) were co-cultured in the gel. In addition, RECs combined with the gel were implanted into IVDs following discectomy in sheep with degenerated IVDs.

Findings

Gene expression of NPC markers, growth factors, and extracellular matrix increased significantly in the co-culture compared to that in each mono-culture. The REC and gel combination enhanced IVD regeneration after discectomy (up to 24 weeks) in the severe IVD degeneration sheep model.

Interpretation

These findings demonstrate the translational potential of the combination of RECs with an in situ-forming gel for the treatment of herniations in degenerative human IVDs.

Funding

Ministry of Education, Culture, Sports, Science, and Technology of Japan, Japan Agency for Medical Research and Development, and the Mochida Pharmaceutical Co., Ltd.

Causes of and Molecular Targets for the Treatment of Intervertebral Disc Degeneration: A Review

Intervertebral disc degeneration (IVDD) is a pathological condition that can lead to intractable back pain or secondary neurological deficits. There is no fundamental cure for this condition, and current treatments focus on alleviating symptoms indirectly. Numerous studies have been performed to date, and the major strategy for all treatments of IVDD is to prevent cell loss due to programmed or regulated cell death. Accumulating evidence suggests that several types of cell death other than apoptosis, including necroptosis, pyroptosis, and ferroptosis, are also involved in IVDD. In this study, we discuss the molecular pathway of each type of cell death and review the literature that has identified their role in IVDD. We also summarize the recent advances in targeted therapy at the RNA level, including RNA modulations through RNA interference and regulation of non-coding RNAs, for preventing cell death and subsequent IVDD. Therefore, we review the causes and possible therapeutic targets for RNA intervention and discuss the future direction of this research field.

Intervertebral Disc Degeneration Models for Pathophysiology and Regenerative Therapy -Benefits and Limitations

Aim:This review summarized the recent intervertebral disc degeneration (IDD) models and described their advantages and potential disadvantages, aiming to provide an overview for the current condition of IDD model establishment and new ideas for new strategies development of the treatment and prevention of IDD.Methods:The database of PubMed was searched up to May 2021 with the following search terms: nucleus pulposus, annulus fibrosus, cartilage endplate, intervertebral disc(IVD), intervertebral disc degeneration, animal model, organ culture, bioreactor, inflammatory reaction, mechanical stress, pathophysiology, epidemiology. Any IDD model-related articles were collected and summarized.Results:The best IDD model should have the features of repeatability, measurability and controllability. There are a lot of aspects to be considered in the selection of animals. Mice, rats and rabbits are low-cost and easy to access. However, their IVD size and shape are more different from human anatomy than pigs, cattle, sheep and goats. Organ culture models and animal models are two options in model establishment for IDD. The IVD organ culture model can put the studying variables into the controllable system for transitional research. Unlike the animal model, the organ culture model can only be used to evaluate the short-term effects and it is not applicable in simulating the complex process of IDD. Similarly, the animal models induced by different methods also have their advantages and disadvantages. For studying the mechanism of IDD and the corresponding treatment and prevention strategies, the selection of model should be individualized based on the purpose of each study.Conclusions:Various models have different characteristics and scope of application due to their different rationales and methods of construction. Currently, there is no experimental model that can perfectly mimic the degenerative process of human IVD. Personalized selection of appropriate model based on study purpose and experimental designing can enhance the possibility to obtain reliable and real results.

Proper animal experimental designs for preclinical research of biomaterials for intervertebral disc regeneration

Low back pain is a vital musculoskeletal disease that impairs life quality, leads to disability and imposes heavy economic burden on the society, while it is greatly attributed to intervertebral disc degeneration (IDD). However, the existing treatments, such as medicines, chiropractic adjustments and surgery, cannot achieve ideal disc regeneration. Therefore, advanced bioactive therapies are implemented, including stem cells delivery, bioreagents administration, and implantation of biomaterials etc. Among these researches, few reported unsatisfying regenerative outcomes. However, these advanced therapies have barely achieved successful clinical translation. The main reason for the inconsistency between satisfying preclinical results and poor clinical translation may largely rely on the animal models that cannot actually simulate the human disc degeneration. The inappropriate animal model also leads to difficulties in comparing the efficacies among biomaterials in different reaches. Therefore, animal models that better simulate the clinical charateristics of human IDD should be acknowledged. In addition, in vivo regenerative outcomes should be carefully evaluated to obtain robust results. Nevertheless, many researches neglect certain critical characteristics, such as adhesive properties for biomaterials blocking annulus fibrosus defects and hyperalgesia that is closely related to the clinical manifestations, e.g., low back pain. Herein, in this review, we summarized the animal models established for IDD, and highlighted the proper models and parameters that may result in acknowledged IDD models. Then, we discussed the existing biomaterials for disc regeneration and the characteristics that should be considered for regenerating different parts of discs. Finally, well-established assays and parameters for in vivo disc regeneration are explored.

Bone Marrow Aspirate Concentrate Combined with in Situ Forming Bioresorbable Gel Enhances Intervertebral Disc Regeneration in Rabbits

BACKGROUND

The current surgical procedure of choice for intervertebral disc (IVD) herniation is discectomy, which induces postoperative IVD degeneration. Thus, cell-based therapies, as a 1-step simple procedure, are desired because of the poor capacity of IVDs for self-repair. The aim of this study was to investigate the repair efficacy of ultra-purified alginate (UPAL) gels containing bone marrow aspirate concentrate (BMAC) for the treatment of discectomy-associated IVD degeneration in rabbits.

METHODS

The mechanical properties of 3 types of gels-UPAL, UPAL containing bone marrow-derived mesenchymal stem cells (BMSCs), and UPAL containing BMAC-were evaluated. Forty rabbits were assigned to 5 groups: intact control, discectomy (to make the cavity), UPAL (implantation of the UPAL gel after discectomy), BMSCs-UPAL (implantation of a combination of autogenic BMSCs and UPAL gel after discectomy), and BMAC-UPAL (implantation of a combination of BMAC and UPAL gel after discectomy). The gels were implanted at 4 weeks after induction of IVD degeneration. At 4 and 12 weeks, magnetic resonance imaging (MRI) as well as histological and immunohistochemical analyses were performed to analyze IVD degeneration qualitatively and the viability of the implanted cells.

RESULTS

There was no significant difference among the 3 types of gels in terms of the results of unconfined compression tests. The implanted cells survived for 12 weeks. The histological grades of the BMSCs-UPAL (mean and standard deviation, 2.50 ± 0.53; p < 0.001) and BMAC-UPAL (2.75 ± 0.64, p = 0.001) showed them to be more effective in preventing degeneration than UPAL gel alone (3.63 ± 0.52). The effectiveness of BMAC-UPAL was not significantly different from that of BMSCs-UPAL, except with respect to type-II collagen synthesis.

CONCLUSIONS

BMAC-UPAL significantly enhanced the repair of IVD defects created by discectomy. This approach could be an effective therapeutic strategy owing to its simplicity and cost-effectiveness compared with cell therapy using culture-expanded BMSCs.

CLINICAL RELEVANCE

Local administration of the BMAC combined with UPAL gel could be an effective therapeutic strategy to enhance IVD repair after discectomy.

Multiple local therapeutics based on nano-hydrogel composites in breast cancer treatment

The locoregional recurrence of breast cancer after tumor resection represents several clinical challenges, and conventional post-surgical adjuvant therapeutics always bring about significant systemic side effects. Thus, the local therapy strategy has received considerable interest in breast cancer treatment, and hydrogels can function as ideal platforms due to their remarkable properties such as good biocompatibility, biodegradability, flexibility, and multifunctionality. The nano-hydrogel composites can further incorporate the advantages of nanomaterials into the hydrogel system, to fabricate hierarchical structures for stimulating controlled multi-stage release of different therapeutic agents and improving the synergistic effects of combination therapy. In this review, the problems of clinical treatments of breast cancer and properties of hydrogels in current biomedical applications are briefly overviewed. The focus is on recent advances in local therapy based on nano-hydrogel composites for both monotherapy (chemotherapy, photothermal and photodynamic therapy) and combination therapy (dual chemotherapy, photothermal chemotherapy, photothermal immunotherapy, radio-chemotherapy). Moreover, the challenges and perspectives in the development of advanced nano-hydrogel systems are also discussed.