Transforming growth factor β mediates communication of co-cultured human nucleus pulposus cells and mesenchymal stem cells

Preclinical Animal Study and Pilot Clinical Trial of Using Enriched Peripheral Blood-Derived Mononuclear Cells for Intervertebral Disc Degeneration

Low back pain (LBP) is a leading cause of long-term disability globally. Intervertebral disk degeneration (IVDD) is mainly responsible for discogenic pain in LBP-affected young patients. There is no effective therapy to reverse disease severity and IVDD progression. This study investigates the effect of human peripheral blood-derived mononuclear cells (PBMCs) on pain relief and life quality improvement in IVDD patients. The enriched monocytes of the PBMCs could differentiate into CD14 and CD206 double-positive M2 macrophages in vitro. Preclinical evidence in rats showed that the transplanted PBMCs exhibited anti-inflammatory and moderate tissue-repair effects on controlling IVDD progress in the rat model. The PBMCs significantly steered the aggrecan and type II collagen expressions and attenuated the pro-inflammatory cytokines in the affected disk. Based on the animal results, 36 patients with chronic low back pain (CLBP) were included in clinical trials. The control group was conservative care only, and the experimental group was platelet-rich plasma (PRP) and PBMCs intradiscal injections. We first confirmed the single lumbar disk causing the discogenic pain by provocative discography or magnetic resonance imaging (MRI). Discogenic LBP participants received one intradiscal injection of autologous PBMCs and followed for 6 months. Our clinical trial showed that patients' LBP and disability were significantly ameliorated after the PBMCs transplantation rather than PRP. These preclinical and pilot clinical studies indicate that intradiscal injection of the enriched PBMCs might be a feasible and potential cell therapy to control pain and disability in IVDD patients.

Intervertebral Disc Progenitors: Lessons Learned from Single-Cell RNA Sequencing and the Role in Intervertebral Disc Regeneration

The tremendous personal and economic burden worldwide caused by low back pain (LBP) has been surging in recent years. While intervertebral disc degeneration (IVDD) is the leading cause of LBP and vast efforts have been made to develop effective therapies, this problem is far from being resolved, as most treatments, such as painkillers and surgeries, mainly focus on relieving the symptoms rather than reversing the cause of IVDD. However, as stem/progenitor cells possess the potential to regenerate IVD, a deeper understanding of the early development and role of these cells could help to improve the effectiveness of stem/progenitor cell therapy in treating LBP. Single-cell RNA sequencing results provide fresh insights into the heterogeneity and development patterns of IVD progenitors; additionally, we compare mesenchymal stromal cells and IVD progenitors to provide a clearer view of the optimal cell source proposed for IVD regeneration.

Co-regulation of Sox9 and TGFβ1 transcription factors in mesenchymal stem cells regenerated the intervertebral disc degeneration

Background

Intervertebral disc (IVD) shows aging and degenerative changes earlier than any other body connective tissue. Its repair and regeneration provide a considerable challenge in regenerative medicine due to its high degree of infrastructure and mechanical complexity. Mesenchymal stem cells, due to their tissue resurfacing potential, represent many explanatory pathways to regenerate a tissue breakdown.

Methods

This study was undertaken to evaluate the co-regulation of Sox9 and TGFβ1 in differentiating human umbilical cord mesenchymal stem cells (hUC-MSC) into chondrocytes. The combinatorial impact of Sox9 and TGFβ1 on hUC-MSCs was examined in vitro by gene expression and immunocytochemical staining. In in vivo, an animal model of IVD degeneration was established under a fluoroscopic guided system through needle puncture of the caudal disc. Normal and transfected MSCs were transplanted. Oxidative stress, pain, and inflammatory markers were evaluated by qPCR. Disc height index (DHI), water content, and gag content were analyzed. Histological examinations were performed to evaluate the degree of regeneration.

Results

hUC-MSC transfected with Sox9+TGFβ1 showed a noticeable morphological appearance of a chondrocyte, and highly expressed chondrogenic markers (aggrecan, Sox9, TGFβ1, TGFβ2, and type II collagens) after transfection. Histological observation demonstrated that cartilage regeneration, extracellular matrix synthesis, and collagen remodeling were significant upon staining with H&E, Alcian blue, and Masson's trichrome stain on day 14. Additionally, oxidative stress, pain, and inflammatory markers were positively downregulated in the animals transplanted with Sox9 and TGFβ1 transfected MSCs.

Conclusion

These findings indicate that the combinatorial effect of Sox9 and TGFβ1 substantially accelerates the chondrogenesis in hUC-MSCs. Cartilage regeneration and matrix synthesis were significantly enhanced. Therefore, a synergistic effect of Sox9 and TGFβ1 could be an immense therapeutic combination in the tissue engineering of cartilaginous joint bio-prostheses and a novel candidate for cartilage stabilization.

Gene Expression in MC3T3-E1 Cells Treated with Diclofenac and Methylprednisolone

Nonsteroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids (GCs) are often used to treat articular-skeletal disorders. The extended use of NSAIDs and GCs have adverse effects on bone metabolism, reducing bone quality and impairing fracture healing. In the present study, we used mouse pre-osteoblast cells MC3T3-E1 to demonstrate the effects of diclofenac (DF) and methylprednisolone (MP) on cell proliferation and gene expression. Cells were incubated with three doses of DF or MP: 0.5 µM, 5 µM, and 50 µM. MP decreased cell viability even after 24 h, but DF inhibited cell viability after only seven days of treatment. The cells were lysed after one, two, three, and seven days of treatment, and gene expression was analyzed by reverse transcription and quantitative PCR (RT-qPCR) assays. DF did not significantly affect the expression of the osteogenic marker genes. MP modified the expression of Osx, Runx, and Col1a1. We concluded that MP is a more potent inhibitor of mouse pre-osteoblast differentiation and viability than is DF. Our results suggest that prolonged DF treatment could be less harmful to osteoblasts than MP treatment.

Elucidating the Focal Immunomodulatory Clues Influencing Mesenchymal Stem Cells in the Milieu of Intervertebral Disc Degeneration

The intervertebral discs (IVDs) are a relatively mobile joint that interconnects vertebrae of the spine. Intervertebral disc degeneration (IVDD) is one of the leading causes of low back pain, which is most often related to patient morbidity as well as high medical costs. Patients with chronic IVDD often need surgery that may sometimes lead to biomechanical complications as well as augmented degeneration of the adjacent segments. Moreover, treatment modalities like rigid intervertebral fusion, dynamic instrumentation, as well as other surgical interventions are still controversial. Mesenchymal stem cells (MSCs) have exhibited to have immunomodulatory functions and the ability to differentiate into cartilage, making these cells possibly an epitome for IVD regeneration. Transplanted MSCs were able to repair IVDD back to the normal disc milieu via the activation of the generation of extracellular matrix (ECM) proteins such as aggrecan, proteoglycans and collagen types I and II. IVD milieu clues like, periostin, cluster of differentiation, tumor necrosis factor alpha, interleukins, chemokines, transforming growth factor beta, reactive oxygen species, toll-like receptors, tyrosine protein kinase receptor and disialoganglioside, exosomes are capable of influencing the MSCs during treatment of IVDD. ECM microenvironment clues above have potentials as biomarkers as well as accurate molecular targets for therapeutic intervention in IVDD.

The impact of matrix age on intervertebral disc regeneration

With the lack of effective treatments for low back pain, the use of extracellular matrix (ECM)-based biomaterials have emerged with undeniable promise for IVD regeneration. Decellularized scaffolds can recreate an ideal microenvironment inducing tissue remodeling and repair. In particular, fetal tissues have a superior regenerative capacity given their ECM composition. In line with this, we unraveled age-associated alterations of the nucleus pulposus (NP) matrisome. Thus, the aim of the present work was to evaluate the impact of ECM donor age on IVD de/regeneration. Accordingly, we optimized an SDS (0.1 %, 1 h)-based decellularization protocol that preserves ECM cues in bovine NPs from different ages. After repopulation with adult NP cells, younger matrices showed the highest repopulation efficiency. Most importantly, cells seeded on younger scaffolds produced healthy ECM proteins suggesting an increased capacity to restore a functional IVD microenvironment. In vivo, only fetal matrices decreased neovessel formation, showing an anti-angiogenic potential. Our findings demonstrate that ECM donor age has a strong influence on angiogenesis and ECM de novo synthesis, opening new avenues for novel therapeutic strategies for the IVD. Additionally, more appropriate 3D models to study age-associated IVD pathology were unveiled.

Proteomic study of mesothelial and endothelial cross-talk: key lessons

INTRODUCTION

The peritoneum, pleura, and pericardium are yet understudied multicellular systems where mesothelial cells (MCs) and endothelial cells (ECs) are in close proximity. Crosstalk between these cell types likely plays role in molecular transport, immunological reactions, and metabolic processes in health, disease, and therapeutic intervention.

AREAS COVERED

In this review, we discuss recent proteomic efforts to characterize the crosstalk between MC and EC. We describe the proteomic methods necessary for investigation of crosstalk between MC and EC, as well as the in-vitro models that can be employed. Potential experimental approaches range from conditioned medium, via co-culture on semi-permeable membranes, to 3D cell culture based organoid models. While the biological and clinical relevance of the models may increase with their ability to mimic close cell communication, the practicality of these complex experiments corresponds vice versa, making standardization more difficult and expensive.

EXPERT OPINION

Currently, data and reports on mesothelial-to-endothelial crosstalk are still very scarce. In our opinion, the in-vitro model using semi-permeable cell culture inserts will allow to establish a basic understanding of cellular crosstalk that may occur between those cell types. Later-on, more sophisticated 3D cell cultures may be better able to simulate the transport dynamics within the peritoneal membrane.

Regulating the fate of stem cells for regenerating the intervertebral disc degeneration

Lower back pain is a leading cause of disability and is one of the reasons for the substantial socioeconomic burden. The etiology of intervertebral disc (IVD) degeneration is complicated, and its mechanism is still not completely understood. Factors such as aging, systemic inflammation, biochemical mediators, toxic environmental factors, physical injuries, and genetic factors are involved in the progression of its pathophysiology. Currently, no therapy for restoring degenerated IVD is available except pain management, reduced physical activities, and surgical intervention. Therefore, it is imperative to establish regenerative medicine-based approaches to heal and repair the injured disc, repopulate the cell types to retain water content, synthesize extracellular matrix, and strengthen the disc to restore normal spine flexion. Cellular therapy has gained attention for IVD management as an alternative therapeutic option. In this review, we present an overview of the anatomical and molecular structure and the surrounding pathophysiology of the IVD. Modern therapeutic approaches, including proteins and growth factors, cellular and gene therapy, and cell fate regulators are reviewed. Similarly, small molecules that modulate the fate of stem cells for their differentiation into chondrocytes and notochordal cell types are highlighted.

NF-κB signalling pathways in nucleus pulposus cell function and intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a common clinical degenerative disease of the spine. A series of factors, such as inflammation, oxidative stress and mechanical stress, promote degradation of the extracellular matrix (ECM) of the intervertebral discs (IVD), leading to dysfunction and structural destruction of the IVD. Nuclear factor-κB (NF-κB) transcription factor has long been regarded as a pathogenic factor of IDD. Therefore, NF-κB may be an ideal therapeutic target for IDD. As NF-κB is a multifunctional functional transcription factor with roles in a variety of biological processes, a comprehensive understanding of the function and regulatory mechanism of NF-κB in IDD pathology will be useful for the development of targeted therapeutic strategies for IDD, which can prevent the progression of IDD and reduce potential risks. This review discusses the role of the NF-κB signalling pathway in the nucleus pulposus (NP) in the process of IDD to understand pathological NP degeneration further and provide potential therapeutic targets that may interfere with NF-κB signalling for IDD therapy.

MicroRNA-140-3p alleviates intervertebral disc degeneration via KLF5/N-cadherin/MDM2/Slug axis

MicroRNAs (miRNAs) are associated with healing or deteriorating degenerated intervertebral disc (IVD) tissues in spinal cord diseases, including intervertebral disc degeneration (IDD). IDD represents a chronic process of extracellular matrix destruction, but the relevant molecular mechanisms implicated in the regenerative effects of miRNAs are unclear. Here, we investigated the regenerative effects of microRNA-140 (miR-140-3p) in an IDD model induced by annulus needle puncture. Bioinformatics analysis was conducted to identify regulatory factors (KLF5/N-cadherin/MDM2/Slug) linked to miR-140-3p effects in IDD. Mesenchymal stem cells (MSCs) were extracted from degenerated IVD nucleus pulposus (NP), and the expression of miR-140-3p/KLF5/N-cadherin/MDM2/Slug was manipulated to explore their effects on cell proliferation, migration, apoptosis and differentiation. The results showed that miR-140-3p was under-expressed in the degenerated IVD NP, whereas its overexpression alleviated IDD. Mechanistic studies suggested that miR-140-3p targeted KLF5 expression, and high KLF5 expression impeded the migration and differentiation of MSCs. In degenerated IVD NP-derived MSCs, MiR-140-3p-mediated KLF5 downregulation simultaneously elevated N-cadherin expression and transcriptionally inhibited MDM2, thus upregulating Slug expression. The experimental data indicated that miR-140-3p enhanced the proliferation, migration and differentiation of degenerated IVD NP-derived MSCs and repressed their apoptosis. The in vivo validation experiment also demonstrated that miR-140-3p inhibited IDD by modulating the KLF5/N-cadherin/MDM2/Slug axis. Collectively, our results uncovered the regenerative role of miR-140-3p in IDD via regulation of the KLF5/N-cadherin/MDM2/Slug axis, which could be a potential therapeutic target for IDD.

The application of decellularized nucleus pulposus matrix/chitosan with transforming growth factor β3 for nucleus pulposus tissue engineering

Low back pain caused by intervertebral disc degeneration has become a global problem that seriously affects public health. The application of nucleus pulposus tissue engineering to disc degeneration has attracted increasing attention. A scaffold is important for nucleus pulposus tissue engineering, which provides a three-dimensional growth space with an appropriate biomechanical and biochemical microenvironment for seed cell differentiation and proliferation. In this study, a decellularized nucleus pulposus matrix/chitosan (DNPM/chitosan) hydrogel scaffold was prepared with crosslinker genipin. Nucleus pulposus stem cells (NPSCs) were cultured in hybrid hydrogels with or without transforming growth factor-β3 (TGF-β3) and then cell morphology, proliferation, and nucleus pulposus-related gene expression were analyzed. TGF-β3 was successfully incorporated into the DNPM/chitosan hydrogel and NPSCs grew well on both kinds of hydrogel. Moreover, gene expression of collagen-I, collagen-II, and aggrecan was enhanced in the DNPM/chitosan hydrogel with TGF-β3. These results indicate that the DNPM/chitosan hybrid hydrogel is a promising candidate scaffold for nucleus pulposus tissue engineering.

Bone mesenchymal stem cell-derived extracellular vesicles promote the repair of intervertebral disc degeneration by transferring microRNA-199a

Extracellular vesicles (EVs) secreted by bone marrow mesenchymal stem cells (BMSCs) protect intervertebral disc degeneration (IDD) by regulating nucleus pulposus cell (NPC) apoptosis. But the mechanism of BMSCs-EVs-microRNA (miR)-199a in IDD remains unclear. In this study, after the acquisition and identification of BMSCs and BMSCs-EVs, IDD mouse model was established and treated with BMSCs-EVs. The pathological changes of NPCs, positive expression of MMP-2, MMP-6 and TIMP1, and the senescence and apoptosis of NPCs were evaluated. Microarray analysis was employed to analyze the differentially expressed miRs and genes after EV treatment. NPCs were treated with EVs/miR-199a/TGF-β agonist SRI-011381. The positive expression of col II and Aggrecan was assessed. The target gene and downstream pathway of miR-199a were analyzed. In vivo experiment, after BMSCs-EV treatment, MMP-2, MMP-6, TIMP1 and TUNEL-positive cells in IDD mice were decreased, and miR-199a was increased. In vitro experiments, the expression of col Ⅱ and Aggrecan, SA-β gal positive cells and apoptosis rate of NPCs were decreased after EV intervention. The protective effect of BMSCs-EVs on NPCs was impaired by reducing miR-199a carried by EVs. miR-199a could target GREM1 to inactivate the TGF-β pathway. miR-199a carried by BMSCs-EVs promotes IDD repair by targeting GREM1 and downregulating the TGF-β pathway. Our work confers a promising therapeutic strategy for IDD.

Analysis of key genes and pathways associated with the pathogenesis of intervertebral disc degeneration

BACKGROUND

Intervertebral disc degeneration (IDD) is widely known as the main contributor to low back pain which has a negative socioeconomic impact worldwide. However, the underlying mechanism remains unclear. This study aims to analyze the dataset GSE23130 using bioinformatics methods to identify the pivotal genes and pathways associated with IDD.

MATERIAL/METHODS

The gene expression data of GSE23130 was downloaded, and differentially expressed genes (DEGs) were extracted from 8 samples and 15 controls. GO and KEGG pathway enrichment analyses were performed. Also, protein-protein interaction (PPI) network was constructed and visualized, followed by identification of hub genes and key module.

RESULTS

A total of 30 downregulated and 79 upregulated genes were identified. The DEGs were mainly enriched in the regulation of protein catabolic process, extracellular matrix organization, collagen fibril organization, and extracellular structure organization. Meanwhile, we found that most DEGs were primarily enriched in the PI3K-Akt signaling pathway. The top 10 hub genes were FN1, COL1A2, SPARC, COL3A1, CTGF, LUM, TIMP1, THBS2, COL5A2, and TGFB1.

CONCLUSIONS

In summary, key candidate genes and pathways were identified by using integrated bioinformatics analysis, which may provide insights into the underlying mechanisms and offer potential target genes for the treatment of IDD.

Screening identifies small molecules that enhance the maturation of human pluripotent stem cell-derived myotubes

Targeted differentiation of pluripotent stem (PS) cells into myotubes enables in vitro disease modeling of skeletal muscle diseases. Although various protocols achieve myogenic differentiation in vitro, resulting myotubes typically display an embryonic identity. This is a major hurdle for accurately recapitulating disease phenotypes in vitro, as disease commonly manifests at later stages of development. To address this problem, we identified four factors from a small molecule screen whose combinatorial treatment resulted in myotubes with enhanced maturation, as shown by the expression profile of myosin heavy chain isoforms, as well as the upregulation of genes related with muscle contractile function. These molecular changes were confirmed by global chromatin accessibility and transcriptome studies. Importantly, we also observed this maturation in three-dimensional muscle constructs, which displayed improved in vitro contractile force generation in response to electrical stimulus. Thus, we established a model for in vitro muscle maturation from PS cells.

TGF-β signaling in intervertebral disc health and disease

OBJECTIVE

This paper aims to provide a comprehensive review of the changing role of transforming growth factor-β (TGF-β) signaling in intervertebral disc (IVD) health and disease.

METHODS

A comprehensive literature search was performed using PubMed terms 'TGF-β' and 'IVD'.

RESULTS

TGF-β signaling is necessary for the development and growth of IVD, and can play a protective role in the restoration of IVD tissues by stimulating matrix synthesis, inhibiting matrix catabolism, inflammatory response and cell loss. However, excessive activation of TGF-β signaling is detrimental to the IVD, and inhibition of the aberrant TGF-β signaling can delay IVD degeneration.

CONCLUSIONS

Activation of TGF-β signaling has a promising treatment prospect for IVD degeneration, while excessive activation of TGF-β signaling may contribute to the progression of IVD degeneration. Studies aimed at elucidating the changing role of TGF-β signaling in IVD at different pathophysiological stages and its specific molecular mechanisms are needed, and these studies will contribute to safe and effective TGF-β signaling-based treatments for IVD degeneration.

Stem Cell Therapies for Treatment of Discogenic Low Back Pain: a Comprehensive Review

PURPOSE OF REVIEW

Discogenic low back pain (DLBP) stems from pathology in one or more intervertebral discs identified as the root cause of the pain. It is the most common type of chronic low back pain (LBP), representing 26-42% of attributable cases.

RECENT FINDINGS

The clinical presentation of DLBP includes increased pain when sitting, coughing, or sneezing, and experiencing relief when standing or ambulating. Dermatomal radiation of pain to the lower extremity and neurological symptoms including numbness, motor weakness, and urinary or fecal incontinence are signs of advanced disease with disc prolapse, nerve root compression, or spinal stenosis. Degenerative disc disease is caused by both a decrease in disc nutrient supply causing decreased oxygen, lowered pH, and lessened ability of the intervertebral disc (IVD) to respond to increased load or injury; moreover, changes in the extracellular matrix composition cause weakening of the tissue and skewing the extracellular matrix's (ECM) harmonious balance between catabolic and anabolic factors for cell turnover in favor of catabolism. Thus, the degeneration of the disc causes a shift from type II to type I collagen expression by NP cells and a decrease in aggrecan synthesis leads to dehydrated matrix cells ultimately with loss of swelling pressure needed for mechanical support. Cell-based therapies such as autologous nucleus pulposus cell re-implantation have in animal models and human trials shown improvements in LBP score, retention of hydration in IVD, and increased disc height. Percutaneously delivered multipotent mesenchymal stem cell (MSC) therapy has been proposed as a potential means to uniquely ameliorate discogenic LBP holistically through three mechanisms: mitigation of primary nociceptive disc pain, slow or reversal of the catabolic metabolism, and restoration of disc tissue. Embryonic stem cells (ESCs) can differentiate into cells of all three germ layers in vitro, but their use is hindered related to ethical concerns, potential for immune rejection after transplantation, disease, and teratoma formation. Another similar approach to treating back pain is transplantation of the nucleus pulposus, which, like stem cell therapy, seeks to address the underlying cause of intervertebral disc degeneration by aiming to reverse the destructive inflammatory process and regenerate the proteoglycans and collagen found in healthy disc tissue. Preliminary animal models and clinical studies have shown mesenchymal stem cell implantation as a potential therapy for IVD regeneration and ECM restoration via a shift towards favorable anabolic balance and reduction of pain.

Curcumin Can Improve Spinal Cord Injury by Inhibiting TGF-β-SOX9 Signaling Pathway

Spinal cord injury (SCI) is a severe nervous system disease with high morbidity and disability rate. Signaling pathways play a key role in the neuronal restorative mechanism following SCI. SRY-related high mobility group (HMG)-box gene 9 (SOX9) affects glial scar formation via Transforming growth factor beta (TGF-β) signaling pathway. Activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is transferred into nucleus to upregulate TGF-β-SOX9. Curcumin exhibits potent anti-inflammatory and anti-oxidant properties. Curcumin can play an important role in SCI recovery by inhibiting the expression of NF-κB and TGF-β-SOX9. Herein, we review the potential mechanism of curcumin-inhibiting SOX9 signaling pathway in SCI treatment. The inhibition of NF-κB and SOX9 signaling pathway by curcumin has the potentiality of serving as neuronal regenerative mechanism following SCI.