Mesenchymal Stem Cells Reduce Intervertebral Disc Fibrosis and Facilitate Repair

Therapeutic potential of mesenchymal stem cell-derived exosomes in skeletal diseases

Skeletal diseases impose a considerable burden on society. The clinical and tissue-engineering therapies applied to alleviate such diseases frequently result in complications and are inadequately effective. Research has shifted from conventional therapies based on mesenchymal stem cells (MSCs) to exosomes derived from MSCs. Exosomes are natural nanocarriers of endogenous DNA, RNA, proteins, and lipids and have a low immune clearance rate and good barrier penetration and allow targeted delivery of therapeutics. MSC-derived exosomes (MSC-exosomes) have the characteristics of both MSCs and exosomes, and so they can have both immunosuppressive and tissue-regenerative effects. Despite advances in our knowledge of MSC-exosomes, their regulatory mechanisms and functionalities are unclear. Here we review the therapeutic potential of MSC-exosomes for skeletal diseases.

Roles of Chemokines in Intervertebral Disk Degeneration

PURPOSE OF REVIEW

Intervertebral disc degeneration is the primary etiology of low back pain and radicular pain. This review examines the roles of crucial chemokines in different stages of degenerative disc disease, along with interventions targeting chemokine function to mitigate disc degeneration.

RECENT FINDINGS

The release of chemokines from degenerated discs facilitates the infiltration and activation of immune cells, thereby intensifying the inflammatory cascade response. The migration of immune cells into the venous lumen is concomitant with the emergence of microvascular tissue and nerve fibers. Furthermore, the presence of neurogenic factors secreted by disc cells and immune cells stimulates the activation of pain-related cation channels in the dorsal root ganglion, potentially exacerbating discogenic and neurogenic pain and intensifying the degenerative cascade response mediated by chemokines. Gaining a deeper comprehension of the functions of chemokines and immune cells in these processes involving catabolism, angiogenesis, and injury detection could offer novel therapeutic avenues for managing symptomatic disc disease.

Nano wear particles and the periprosthetic microenvironment in aseptic loosening induced osteolysis following joint arthroplasty

Joint arthroplasty is an option for end-stage septic arthritis due to joint infection after effective control of infection. However, complications such as osteolysis and aseptic loosening can arise afterwards due to wear and tear caused by high joint activity after surgery, necessitating joint revision. Some studies on tissue pathology after prosthesis implantation have identified various cell populations involved in the process. However, these studies have often overlooked the complexity of the altered periprosthetic microenvironment, especially the role of nano wear particles in the etiology of osteolysis and aseptic loosening. To address this gap, we propose the concept of the "prosthetic microenvironment". In this perspective, we first summarize the histological changes in the periprosthetic tissue from prosthetic implantation to aseptic loosening, then analyze the cellular components in the periprosthetic microenvironment post prosthetic implantation. We further elucidate the interactions among cells within periprosthetic tissues, and display the impact of wear particles on the disturbed periprosthetic microenvironments. Moreover, we explore the origins of disease states arising from imbalances in the homeostasis of the periprosthetic microenvironment. The aim of this review is to summarize the role of relevant factors in the microenvironment of the periprosthetic tissues, in an attempt to contribute to the development of innovative treatments to manage this common complication of joint replacement surgery.

Physalin A alleviates intervertebral disc degeneration via anti-inflammatory and anti-fibrotic effects

Background

The incidence of intervertebral disc degeneration (IVDD) is a common degenerative disease with inflammation, decreased autophagy, and progression of fibrosis as its possible pathogenesis. Physalin A (PA) is a widely studied anti-inflammatory drug. However, its therapeutic effects on IVDD remain unexplored. Therefore, we aimed to explore the therapeutic potential of PA in IVDD progression.

Materials and methods

In vivo, we investigated PA bioactivity using a puncture-induced IVDD rat model. IVDD signals and height changes were detected using X-ray, micro-CT, and MRI, and structural and molecular lesions using histological staining and immunohistochemistry of intervertebral disc sections. In vivo, interleukin-1 beta (IL-1β) and TGF-β1 were employed to establish inflammation fibrotic nucleus pulposus (NP) cells. The PA effect duration, concentration, influence pathways, and pathological changes in IVDD treatment were elucidated using western blotting, real-time PCR, and immunofluorescence.

Results

PA exerted significant effects on IVDD remission due to anti-inflammation, fibrosis reduction, and autophagy enhancement. In vitro, PA improved inflammation by blocking the NF-κB and MAPK pathways, whereas it promoted autophagy via the PI3K/AKT/mTOR pathway and affected fibrotic progression by regulating the SMAD2/3 pathway. Moreover, PA improved the disc degeneration process in IVDD model.

Conclusions

PA exhibited significant anti-inflammatory and anti-fibrotic effects and improved autophagy in vivo and in vitro IVDD models, thus effectively relieving IVDD progression, indicating it is a promising agent for IVDD treatment.

The translational potential of this article

This study successfully reveals that PA, a natural bioactive withanolide, effectively relieved IVDD progression via inflammation inhibition, fibrosis reduction, and autophagy enhancement, indicating it is a promising agent for IVDD treatment.

The Effect of Tissue Stromal Vascular Fraction as Compared to Cellular Stromal Vascular Fraction to Treat Anal Sphincter Incontinence

BACKGROUND

The long-term prognosis of current treatments for anal sphincter incontinence (ASI) is poor. Here, we explored the efficacy of tissue adipose stromal vascular fraction SVF (tSVF) on ASI and compared it to that of cellular SVF (cSVF). We then investigated possible mechanisms.

METHODS

Rat cSVF and tSVF were isolated and labeled with DIL. One day after modeling, three groups received phosphate-buffered saline (PBS), cSVF, tSVF, respectively. The control group received nil modeling nor any treatments. The effect was assessed by function test for anal pressure and electromyography, and staining for fiber content, proliferation and differentiation at day 5 and day 10.

RESULTS

cSVF injection resulted in faster healing than tSVF. The cSVF group showed significant improvement on anal pressure on day 10. For the electromyography test, cSVF showed significant improvement for the frequencies on day 10, and for the peak values on both time points, while tSVF showed significant improvement for the peak values on day 10. The two SVF both alleviated fibrosis. Immunofluorescence tracing identified differentiation of some injected cells towards myosatellite cells and smooth muscle cells in both SVF groups. For all the tests, the tSVF group tends to have similar or lower effects than the cSVF group with no significant difference.

CONCLUSION

cSVF and tSVF are both safe and effective in treating ASI, while the effect of cSVF is slighter higher than tSVF.

The therapeutic effect of stem cells from human exfoliated deciduous teeth on a rat model of tracheal fistula

Background

Tracheal fistulas (TF) can be dangerous and even fatal in patients. The current treatment is really challenging. Previous studies reported that mesenchymal stem cells (MSCs) could be used to treat respiratory tract fistulas. Stem cells from human exfoliated deciduous teeth (SHED) are considered to be MSC-like cells that may also have the potential to treat the tracheal fistulas. In this study, we investigated the therapeutic effects of SHED in rat tracheal fistula models.

Methods

A total of 80 SD rats were randomly divided into five groups: a sham-operated group, a local PBS group (L-PBS), an intravenous PBS group (I-PBS), a local SHED treatment group (L-SHED), and an intravenous SHED treatment group (I-SHED). The L-SHED and I-SHED groups were given a topical application around the fistula or an intravenous injection of 1*10⁷ SHED via the tail vein, respectively, while the L-PBS and I-PBS groups were given an equivalent volume of PBS through local or intravenous administration. A stereomicroscope was used to observe fistula healing on the 2nd, 3rd, and 5th days following transplantation. On the 7th day, the survival of SHED was observed by immunofluorescence. The pathology of the lungs and fistulas was observed by hematoxylin and eosin (H&E) and Masson staining. The expression levels of the Toll-like receptor 4 (TLR4), interleukin (IL)-1β, IL-33, and IL-4 were measured using immunohistochemistry. The expression levels of TLR4, high mobility group box 1 (HMGB1), and myeloid differentiation factor 88 (MYD88) were studied using western blotting. On day 14, airway responsiveness of rats was detected and analyzed.

Results

Fistula healing in the L-SHED and I-SHED groups was faster than that in their respective PBS groups after transplantation. The fistula diameters in the L-SHED and I-SHED groups were significantly smaller than those in the L-PBS and I-PBS groups on the 3rd day. Moreover, the phenomenon of fibroblast proliferation and new blood vessel growth around the fistula seemed more pronounced in the L-SHED and I-SHED groups. Although no discernible difference was found in airway responsiveness after SHED treatment, the degree of inflammation in the lungs was reduced by intravenous SHED treatment. However, there was no significant reduction in lung inflammation by local SHED treatment. The expression levels of IL-1β and IL-33 were decreased in the I-SHED group, while IL-4 was elevated compared with the I-PBS group. Interestingly, intravenous SHED treatment inhibited the activation of HMGB1/TLR4/MYD88 in the lung tissues of TF rats.

Conclusions

SHED transplantation accelerated the rate of fistula healing in rats. Intravenous SHED treatment reduced lung inflammation. Thus, SHED may have potential in the treatment of tracheal fistula, providing hope for future therapeutic development for TF.

The Effect of Mesenchymal Stem Cells, Adipose Tissue Derived Stem Cells, and Cellular Stromal Vascular Fraction on the Repair of Acute Anal Sphincter Injury in Rats

Background: Anal sphincter incontinence (ASI) can cause a serious decline in the quality of life and can cause a socioeconomic burden. Studies have shown that bone marrow mesenchymal stem cells (MSC) have significant therapeutic effects on ASI, but the cost and risk of MSC harvest limit their further application. In contrast, adipose tissue derived stem cells (ADSC) and cellular stromal vascular fraction (CSVF) as stem cell sources have multipotency and the advantage of easy harvest. Objective: Here we aim to investigate the effects of ADSC and CSVF on treating ASI and compare them to that of bone marrow MSC. Methods: Bone marrow MSC, ADSC, and CSVF were obtained and labeled with green fluorescent protein (GFP), and CSVF was labeled with DIL. Sprague Dawley (SD) rats were divided into 5 groups. Four groups were injected with 0.2 mL phosphate buffer saline (PBS), 1 × 107/0.2 mL of MSC, ADSC, or CSVF, respectively, after model establishment. The control group received no treatment. The repair was assessed by anal functional tests and immunostaining on day 5 and day 10 after injection. Results: MSC, ADSC, and CSVF significantly promoted tissue repair and the recovery of muscle contraction and electromyographic activity in ASI. The generation of myosatellite cells by injected MSC, ADSC, and CSVF was found in the wounded area. On day 5, CSVF showed highest therapeutic effect, while on day 10, MSC and ADSC showed higher therapeutic effects than CSVF. When comparing the effects of MSC and ADSC, ADSC was slightly better than MSC in the indexes of anal pressure, etc. Conclusion: ADSC and CVSF are alternative stem cell sources for ASI repair.

Current Perspectives on Nucleus Pulposus Fibrosis in Disc Degeneration and Repair

A growing body of evidence in humans and animal models indicates an association between intervertebral disc degeneration (IDD) and increased fibrotic elements in the nucleus pulposus (NP). These include enhanced matrix turnover along with the abnormal deposition of collagens and other fibrous matrices, the emergence of fibrosis effector cells, such as macrophages and active fibroblasts, and the upregulation of the fibroinflammatory factors TGF-β1 and IL-1/-13. Studies have suggested a role for NP cells in fibroblastic differentiation through the TGF-βR1-Smad2/3 pathway, inflammatory activation and mechanosensing machineries. Moreover, NP fibrosis is linked to abnormal MMP activity, consistent with the role of matrix proteases in regulating tissue fibrosis. MMP-2 and MMP-12 are the two main profibrogenic markers of myofibroblastic NP cells. This review revisits studies in the literature relevant to NP fibrosis in an attempt to stratify its biochemical features and the molecular identity of fibroblastic cells in the context of IDD. Given the role of fibrosis in tissue healing and diseases, the perspective may provide new insights into the pathomechanism of IDD and its management.

Low-dose mesenchymal stem cell therapy for discogenic pain: safety and efficacy results from a 1-year feasibility study

Aim: To evaluate safety and efficacy of low dose autologous adipose-derived mesenchymal stem cells (ADMSCs) for treatment of disc degeneration resulting in low back pain (LBP). Methods: Nine participants with chronic LBP originating from single-level lumbar disc disease underwent intradiscal injection of 10 million ADMSCs with optional repetition after 6 months. Results: No unexpected or serious adverse events were recorded. Seven (78%) of participants reported reductions in pain 12 months after treatment. Five (56%) reported increased work capacity. Three (33%) reduced analgesic medication. Improvements in EQ-5D and Oswestry disability index results were observed. MRI demonstrated no further disc degeneration and improvements to annular fissures and disc protrusions. Conclusion: This study provides initial evidence of safety and efficacy of ADMSCs for discogenic LBP.

Impact of Microenvironmental Changes during Degeneration on Intervertebral Disc Progenitor Cells: A Comparison with Mesenchymal Stem Cells

Intervertebral disc (IVD) degeneration occurs with natural ageing and is linked to low back pain, a common disease. As an avascular tissue, the microenvironment inside the IVD is harsh. During degeneration, the condition becomes even more compromised, presenting a significant challenge to the survival and function of the resident cells, as well as to any regeneration attempts using cell implantation. Mesenchymal stem cells (MSCs) have been proposed as a candidate stem cell tool for IVD regeneration. Recently, endogenous IVD progenitor cells have been identified inside the IVD, highlighting their potential for self-repair. IVD progenitor cells have properties similar to MSCs, with minor differences in potency and surface marker expression. Currently, it is unclear how IVD progenitor cells react to microenvironmental factors and in what ways they possibly behave differently to MSCs. Here, we first summarized the microenvironmental factors presented in the IVD and their changes during degeneration. Then, we analyzed the available studies on the responses of IVD progenitor cells and MSCs to these factors, and made comparisons between these two types of cells, when possible, in an attempt to achieve a clear understanding of the characteristics of IVD progenitor cells when compared to MSCs; as well as, to provide possible clues to cell fate after implantation, which may facilitate future manipulation and design of IVD regeneration studies.

Mesenchymal stromal/stem cells and their exosomes application in the treatment of intervertebral disc disease: A promising frontier

Today, the application of mesenchymal stromal/stem cells (MSCs) and their exosomes to treat degenerative diseases has received attention. Due to the characteristics of these cells, such as self-renewability, differentiative and immunomodulatory effects, their use in laboratory and clinical studies shows promising results. However, the allogeneic transplantation problems of MSCs limit the use of these cells in the clinic. Scientists propose the application of exosomes to use from the therapeutic effect of MSCs and overcome their defects. These vesicles change the target cell behaviour and transcription profile by transferring various cargo such as proteins, mi-RNAs, and lipids. One of the degenerative tissue diseases in which MSCs and their exosomes are used in their treatment is intervertebral disc disease (IDD). Different factors such as genetics, nutrition, ageing, and environmental factors play a significant role in the onset and progression of this disease. These factors affect the cellular and molecular properties of the disc, leading to tissue destruction. Nucleus pulposus cells (NPCs) are among the most important cells involved in the pathogenesis of disc degeneration. MSCs exert their therapeutic effects by differentiating, reducing apoptosis, increasing proliferation, and decreasing senescence in NPCs. In addition, the use of MSCs and their exosomes also affects the annulus fibrosus and cartilaginous endplate cells in disc tissue and prevents disc degeneration progression.

Development, Pathogenesis, and Regeneration of the Intervertebral Disc: Current and Future Insights Spanning Traditional to Omics Methods

The intervertebral disc (IVD) is the fibrocartilaginous joint located between each vertebral body that confers flexibility and weight bearing capabilities to the spine. The IVD plays an important role in absorbing shock and stress applied to the spine, which helps to protect not only the vertebral bones, but also the brain and the rest of the central nervous system. Degeneration of the IVD is correlated with back pain, which can be debilitating and severely affects quality of life. Indeed, back pain results in substantial socioeconomic losses and healthcare costs globally each year, with about 85% of the world population experiencing back pain at some point in their lifetimes. Currently, therapeutic strategies for treating IVD degeneration are limited, and as such, there is great interest in advancing treatments for back pain. Ideally, treatments for back pain would restore native structure and thereby function to the degenerated IVD. However, the complex developmental origin and tissue composition of the IVD along with the avascular nature of the mature disc makes regeneration of the IVD a uniquely challenging task. Investigators across the field of IVD research have been working to elucidate the mechanisms behind the formation of this multifaceted structure, which may identify new therapeutic targets and inform development of novel regenerative strategies. This review summarizes current knowledge base on IVD development, degeneration, and regenerative strategies taken from traditional genetic approaches and omics studies and discusses the future landscape of investigations in IVD research and advancement of clinical therapies.

The involvement of immune system in intervertebral disc herniation and degeneration

Intervertebral disc (IVD) herniation and degeneration contributes significantly to low back pain (LBP), of which the molecular pathogenesis is not fully understood. Disc herniation may cause LBP and radicular pain, but not all LBP patients have disc herniation. Degenerated discs could be the source of pain, but not all degenerated discs are symptomatic. We previously found that disc degeneration and herniation accompanied by inflammation. We further found that anti‐inflammatory molecules blocked immune responses, alleviated IVD degeneration and pain. Based on our recent findings and the work of others, we hypothesize that immune system may play a prominent role in the production of disc herniation or disc degeneration associated pain. While the nucleus pulposus (NP) is an immune‐privileged organ, the damage of the physical barrier between NP and systemic circulation, or the innervation and vascularization of the degenerated NP, on one hand exposes NP as a foreign antigen to immune system, and on the other hand presents compression on the nerve root or dorsal root ganglion (DRG), which both elicit immune responses induced by immune cells and their mediators. The inflammation can remain for a long time at remote distance, with various types of cytokines and immune cells involved in this pain‐inducing process. In this review, we aim to revisit the autoimmunity of the NP, immune cell infiltration after break of physical barrier, the inflammatory activities in the DRG and the generation of pain. We also summarize the involvement of immune system, including immune cells and cytokines, in degenerated or herniated IVDs and affected DRG.

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.

Fibrotic alterations in human annulus fibrosus correlate with progression of intervertebral disc herniation

BACKGROUND

Intervertebral disc (IVD) herniation is characterized by annulus fibrosus failure (AF) in containing the nucleus pulposus (NP). IVD herniation involves cellular and extracellular matrix (ECM) alterations that have been associated with tissue fibrosis, although still poorly investigated.

METHODS

Here, fibrotic alterations in human AF were evaluated, by characterizing the herniated ECM. Human AF samples (herniated lumbar IVD (n = 39, age 24-83) and scoliosis controls (n = 6, age 15-21)) were processed for transmission electron microscopy and histological/immunohistochemical analysis of fibrotic markers. Correlations between the fibrotic markers in AF ECM and the degree of NP containment (protused, contained and uncontained) and patients' age were conducted.

RESULTS

Our results demonstrate that with herniation progression, i.e. loss of NP containment, human AF presents less stained area of sulphated glycosaminoglycans and collagen I, being collagen I fibres thinner and disorganized. On the other hand, fibronectin stained area and percentage of α-smooth muscle actin+ cells increase in human AF, while matrix metalloproteinase-12 (MMP12) production and percentage of macrophages (CD68+ cells) remain constant. These structural and biochemical fibrotic alterations observed in human AF with herniation progression occur independently of the age.

CONCLUSIONS

The characterization of human AF here conducted evidence the presence of fibrosis in degenerated IVD, while highlighting the importance of considering the herniation progression stage, despite the patients' age, for a better understanding of the mechanisms behind AF failure and IVD herniation.

Intervertebral disc degeneration in warmblood horses: Histological and biochemical characterization

Gross morphology of healthy and degenerated intervertebral discs (IVDs) is largely similar in horses as in dogs and humans. For further comparison, the biochemical composition and the histological and biochemical changes with age and degeneration were analyzed in 41 warmblood horses. From 33 horses, 139 discs and 2 fetal vertebral columns were evaluated and scored histologically. From 13 horses, 73 IVDs were assessed for hydration, DNA, glycosaminoglycans, total collagen, hydroxyl-lysyl-pyridinoline, hydroxylysine, and advanced glycation end-product (AGE) content. From 7 horses, 20 discs were assessed for aggrecan, fibronectin, and collagen type 1 and 2 content. Histologically, tearing of the nucleus pulposus (NP) and cervical annulus fibrosus (AF), and total histological score (tearing and vascular proliferation of the AF, and chondroid metaplasia, chondrocyte-like cell proliferation, presence of notochordal cells, matrix staining, and tearing of the NP) correlated with gross degeneration. Notochordal cells were not seen in IVDs of horses. Age and gross degeneration were positively correlated with AGEs and a fibrotic phenotype, explaining gross degenerative changes. In contrast to dogs and humans, there was no consistent difference in glycosaminoglycan content and hydration between AF and NP, nor decrease of these variables with age or degeneration. Hydroxylysine decrease and collagen 1 and AGEs increase were most prominent in the NP, suggesting degeneration started in the AP. In caudal cervical NPs, AGE deposition was significantly increased in grossly normal IVDs and total collagen significantly increased with age, suggesting increased biomechanical stress and likelihood for spinal disease in this part of the vertebral column.

The Potential Use of Mesenchymal Stem Cells and Their Derived Exosomes for Orthopedic Diseases Treatment

Musculoskeletal disorders (MSDs) are conditions that can affect muscles, bones, and joints. These disorders are very painful and severely limit patients' mobility and are more common in the elderly. MSCs are multipotent stem cells isolated from embryonic (such as the umbilical cord) and mature sources (such as adipose tissue and bone marrow). These cells can differentiate into various cells such as osteoblasts, adipocytes, chondrocytes, NP-like cells, Etc. Due to MSC characteristics such as immunomodulatory properties, ability to migrate to the site of injury, recruitment of cells involved in repair, production of growth factors, and large amount production of extracellular vesicles, these cells have been used in many regenerative-related medicine studies. Also, MSCs produce different types of EVs, such as exosomes, to the extracellular environment. Exosomes reflect MSCs' characteristics and do not have cell therapy-associated problems because they are cell-free. These vesicles carry proteins, nucleic acids, and lipids to the host cell and change their function. This review focuses on MSCs and MSCs exosomes' role in repairing dense connective tissues such as tendons, cartilage, invertebrate disc, bone fracture, and osteoporosis treatment.

Innovative Biological Treatment Methods for Degenerative Disc Disease

Low back pain is the leading cause of work absences and years lived with disability, and it is often associated with degenerative disc disease. In recent years, biological treatment approaches such as the use of growth factors, cell injections, annulus fibrosus (AF) repair, nucleus pulposus replacement, and tissue-engineered discs have been explored as means for preventing or reversing degenerative disc disease. Both animal and clinical studies have shown promising results for cell-based therapy on the grounds of its regenerative potential. Clinical data also indicate that stem cell injection is safe when appropriately performed, albeit its long-term safety and efficacy are yet to be explored. Numerous challenges also remain to be overcome, such as isolating, differentiating, and preconditioning the disc cells, as well as managing the nutrient-deficient and oxygen-deficient micromilieu of the intervertebral disc (IVD). AF repair methods including devices used in clinical trials have shown success in decreasing reherniation rates and improving overall clinical outcomes. In addition, recent studies that combined AF repair and nucleus pulposus replacement have shown improved biomechanical stability in IVDs after the combined treatment. Tissue-engineered IVDs for total disc replacement are still being developed, and future studies are necessary to overcome the challenges in their delivery, efficacy, and safety.

The Upregulation of COX2 in Human Degenerated Nucleus Pulposus: The Association of Inflammation with Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is an important risk factor of low back pain. We previously found upregulated markers of fibrosis, the late stage of chronic inflammation, in degenerated IVD with a small number of clinical specimens. Here, we aimed to study on a larger scale the association of cyclooxygenase 2 (COX2), an inflammation and/or pain marker, with IVDD. This study involved 107 LBP participants. The IVD degeneration level was graded on a 1–5 scale according to the Pfirrmann classification system. Discs at grades 1-3 were further grouped as white discs with grades 4-5 as black discs. We recorded baseline information about age, gender, body mass index (BMI), diabetes history, smoking history, and magnetic resonance imaging (MRI). Their association with IVDD was statistically analyzed. The expression level of COX2 was investigated by immunohistochemistry. The total integrated COX2 optical density (IOD), number of COX2-positive cells, and total cell number of each image were counted and analyzed by Image-Pro Plus software. The IOD and number of COX2-positive cells were divided by the total cell number to obtain COX2 expression density (IOD/cell) and COX2 positivity (cell+/cell). As a result, among the baseline information investigated, only age was found to have a significant association with IVDD. The IOD/cell was found to be significantly increased from grade 2 to grade 5, as well as in black discs compared to white discs. The cell+/cell displayed the same trend that it increased in highly degenerative discs compared to their counterparts. In conclusion, the expression of COX2 is associated with IVDD, which highlights COX2 as a biomarker for IVD degeneration and indicates the involvement of inflammation and pain signaling in IVDD.

Influence of extracellular nanovesicles derived from adipose-derived stem cells on nucleus pulposus cell from patients with intervertebral disc degeneration

An increasing number of individuals are suffering from lower back and neck pain caused by intervertebral disc degeneration each year. Although the application of mesenchymal stem cells (MSCs) has provided desirable results in the treatment of intervertebral disc degeneration, there are multiple risks associated with the directed application of MSCs. An increasing number of studies have suggested that stem cells, through the release of extracellular nanovesicles, have vital functions in tissue regeneration and repair with low risk. The present study investigated the effect of extracellular nanovesicles derived from adipose-derived stem cells (ADSCs) on nucleus pulposus (NP) cells from patients with intervertebral disc degeneration. Human NP cells were obtained from patients with intervertebral disc degeneration undergoing surgical procedures in addition to ADSCs from liposuction patients. ADSC-derived extracellular nanovesicles were isolated and characterized. The differentiation and biological activity of NP cells cultured with or without ADSC-derived extracellular nanovesicles were assessed and inflammatory factors and intervertebral disc degeneration-associated markers were also measured. The results indicated that extracellular nanovesicles derived from ADSCs increased the migration and proliferation of NP cells and inhibited inflammatory activity, suggesting their utility for the treatment of intervertebral disc degeneration.

The Cellular Composition of Bovine Coccygeal Intervertebral Discs: A Comprehensive Single-Cell RNAseq Analysis

Intervertebral disc (IVD) degeneration and its medical consequences is still one of the leading causes of morbidity worldwide. To support potential regenerative treatments for degenerated IVDs, we sought to deconvolute the cell composition of the nucleus pulposus (NP) and the annulus fibrosus (AF) of bovine intervertebral discs. Bovine calf tails have been extensively used in intervertebral disc research as a readily available source of NP and AF material from healthy and young IVDs. We used single-cell RNA sequencing (scRNAseq) coupled to bulk RNA sequencing (RNAseq) to unravel the cell populations in these two structures and analyze developmental changes across the rostrocaudal axis. By integrating the scRNAseq data with the bulk RNAseq data to stabilize the clustering results of our study, we identified 27 NP structure/tissue specific genes and 24 AF structure/tissue specific genes. From our scRNAseq results, we could deconvolute the heterogeneous cell populations in both the NP and the AF. In the NP, we detected a notochordal-like cell cluster and a progenitor stem cell cluster. In the AF, we detected a stem cell-like cluster, a cluster with a predominantly fibroblast-like phenotype and a potential endothelial progenitor cluster. Taken together, our results illustrate the cell phenotypic complexity of the AF and NP in the young bovine IVDs.

The Cellular Composition of Bovine Coccygeal Intervertebral Discs: A Comprehensive Single-Cell RNAseq Analysis

Intervertebral disc (IVD) degeneration and its medical consequences is still one of the leading causes of morbidity worldwide. To support potential regenerative treatments for degenerated IVDs, we sought to deconvolute the cell composition of the nucleus pulposus (NP) and the annulus fibrosus (AF) of bovine intervertebral discs. Bovine calf tails have been extensively used in intervertebral disc research as a readily available source of NP and AF material from healthy and young IVDs. We used single-cell RNA sequencing (scRNAseq) coupled to bulk RNA sequencing (RNAseq) to unravel the cell populations in these two structures and analyze developmental changes across the rostrocaudal axis. By integrating the scRNAseq data with the bulk RNAseq data to stabilize the clustering results of our study, we identified 27 NP structure/tissue specific genes and 24 AF structure/tissue specific genes. From our scRNAseq results, we could deconvolute the heterogeneous cell populations in both the NP and the AF. In the NP, we detected a notochordal-like cell cluster and a progenitor stem cell cluster. In the AF, we detected a stem cell-like cluster, a cluster with a predominantly fibroblast-like phenotype and a potential endothelial progenitor cluster. Taken together, our results illustrate the cell phenotypic complexity of the AF and NP in the young bovine IVDs.

Directed Differentiation of Notochord-like and Nucleus Pulposus-like Cells Using Human Pluripotent Stem Cells

Intervertebral disc degeneration might be amenable to stem cell therapy, but the required cells are scarce. Here, we report the development of a protocol for directed in vitro differentiation of human pluripotent stem cells (hPSCs) into notochord-like and nucleus pulposus (NP)-like cells of the disc. The first step combines enhancement of ACTIVIN/NODAL and WNT and inhibition of BMP pathways. By day 5 of differentiation, hPSC-derived cells express notochordal cell characteristic genes. After activating the TGF-β pathway for an additional 15 days, qPCR, immunostaining, and transcriptome data show that a wide array of NP markers are expressed. Transcriptomically, the in vitro-derived cells become more like in vivo adolescent human NP cells, driven by a set of influential genes enriched with motifs bound by BRACHYURY and FOXA2, consistent with an NP cell-like identity. Transplantation of these NP-like cells attenuates fibrotic changes in a rat disc injury model of disc degeneration.

Elucidating the role of cell-mediated inflammatory cytokines on allogeneic mouse-derived nucleus pulposus mesenchymal stem cells

In this present study, our aim was to evaluate the cell-mediated specific anti-donor antibody and its associated inflammatory cytokine secretion along with its succeeding effects on Nucleus pulposus-derived mesenchymal stem cells (NPMSCs). Tissue from the NP compartment of 12 normal mice was isolated, expanded in cell culture, and the cell phenotypes were confirmed by flow cytometry. Multipotent differentiation and its specific gene expression analysis were confirmed by reverse transcriptase PCR. T and B cells were monitored for both donor and recipient mouse and further analysis of anti-donor antibody secretion was confirmed by lymphocyte crossmatch. In conjunction with anti-donor-specific antibody analysis, the associated inflammatory cytokine expression was analyzed by ELISA. In co-culture, cell-mediated antibody secretion was elevated in T and B cells positive mouse group, when compared to control mouse group. Allogeneic-derived donor NPMSCs were found to be stimulated the secretion of pro-inflammatory cytokines and the level of pro-inflammatory cytokines showed reduced expression in control mouse serum. In co-culture group the concentration of the cell-mediated pro- and anti-inflammatory cytokines found to be increased. PRACTICAL APPLICATIONS: Mesenchymal stem cell exhibit good regeneration capacity for many types of disease, and the mechanism belongs to regeneration is not clear. In intervertebral disc, the nucleus pulposus-derived mesenchymal stem cells showed a better regeneration capacity. On the contrary, the NP cells-based therapy, the Mesenchymal stem cells showed expanded anabolic and reduced catabolic activity together with induced anti-inflammatory effect. In this study, the T & B cells were used to evaluate the anti-donor antibody secretion and also to study how it stimulates the production of anti-donor antibodies against the donor cells. Finally, it was found that T & B cells lead the synthesis of inflammatory cytokines are IL-1, IL-6, and TNF-α. From this study, the results proved that the cell-mediated pro- and anti-inflammatory cytokines to be monitored in allogeneic stem cells-based therapy of intervertebral disc degeneration.

Comparison of the application value of two commonly used minimally invasive spinal surgery in the treatment of lumbar disc herniation

The aim of the study was to compare the application value of percutaneous transforaminal endoscopic discectomy (PTED) and microendoscopic discectomy (MED) in the treatment of lumbar disc herniation (LDH). From January 2017 to July 2018, 108 LDH patients undergoing surgical treatment in our hospital were collected and divided into PTED group (treated with PTED, n=50) and MED group (treated with MED, n=58). The operation parameter index level, complications, recurrence and pain score (VAS), Oswestry disability index (ODI) and Japanese Orthopaedic Association Scale (JOA) were compared between the two groups. VAS, ODI and JOA scores of the two groups were significantly decreased after operation (P<0.05), but there was no significant difference between the two groups (P>0.05). Complications and recurrence of the two groups were similar (P>0.05). MED was superior to PTED in the number of intraoperative fluoroscopy and operation time, while PTED was superior to MED in intraoperative blood loss, incision length, length of hospital stay and bed rest time (P<0.05). Both PTED and MED can effectively treat LDH. Referring to clinical data, PTED may be the first choice for LDH treatment.

Ultrasound‑targeted microbubble destruction‑mediated Galectin‑7‑siRNA promotes the homing of bone marrow mesenchymal stem cells to alleviate acute myocardial infarction in rats

Bone marrow mesenchymal stem cells (BMSCs) are accepted as a form of cellular therapy to improve cardiac function following acute myocardial infarction (AMI). The present study was performed to investigate the synergistic effect of ultrasound-targeted microbubble destruction (UTMD)-mediated Galectin-7-small interfering (si)RNA with the homing of BMSCs for AMI. The rat model of AMI was established, followed by identification of BMSCs. Rats with AMI received BMSC transplantation, BMSC transplantation + UTMD + siRNA negative control, or BMSC transplantation + UTMD + Galectin-7-siRNA. The cardiac function, hemodynamics indexes, degree of myocardial fiber injury and expression of apoptosis-related proteins in myocardial tissues of rats were detected. The homing of BMSCs was observed, and the indexes of myocardial microenvironment and the TGF-β/Smads pathway-related proteins in myocardial tissues were determined. AMI rats treated with UTMD-mediated Galectin-7-siRNA exhibited improved cardiac function and hemodynamics-related indices, decreased myocardial fiber injury and apoptotic cells, as well as enhanced homing ability of BMSCs, improved myocardial microenvironment, and suppressed TGF-β1/Smads pathway activation. In conclusion, the present study demonstrated that UTMD-mediated Galectin-7-siRNA treatment could enhance the homing ability of BMSCs, thus alleviating AMI in rats.

Exosomes Derived from Human Urine-Derived Stem Cells Inhibit Intervertebral Disc Degeneration by Ameliorating Endoplasmic Reticulum Stress

Objective

This study is aimed at determining the effects of human urine-derived stem cell-derived exosomes (USCs-exos) on pressure-induced nucleus pulposus cell (NPC) apoptosis and intervertebral disc degeneration (IDD) and on the ERK and AKT signaling pathways.

Methods

The NPCs were obtained from patients with herniated lumbar discs. Western blot analysis (WB) and quantitative real-time polymerase chain reaction (qRT-PCR) were used to determine endoplasmic reticulum (ER) stress levels of NPCs under stress. Human USCs were identified using an inverted microscope, three-line differentiation experiments, and flow cytometry. A transmission microscope, nanoparticle size analysis, and WB procedures were used to identify the extracted exosomes and observe NPC uptake. A control group, a 48 h group, and a USCs-exos group were established. The control group was untreated, and the 48 h group was pressure-trained for 48 h, while the USCs-exos group was pressure-trained for 48 h and treated with USCs-exos. WB, qRT-PCR, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis were used to determine the ER stress levels in stress conditions and after exosomal treatment. The AKT and ERK pathways were partially detected. Magnetic Resonance Imaging (MRI) and computed tomography (CT) were used to evaluate cell degeneration while exosomal effects on the intervertebral disc (IVD) tissue were determined by hematoxylin and eosin (HE) staining, Safranin O-fast green staining, immunohistochemical staining (IHC), nuclear magnetic resonance (NMR), spectrometric detection, and total correlation spectroscopy (TOCSY). IVD metabolites were also identified and quantified.

Results

After pressure culture, ER stress markers (GRP78 and C/EBP homologous protein (CHOP)) in the NPCs were significantly elevated with time (p < 0.05). Human USCs are short and spindle-shaped. They can successfully undergo osteogenic, adipogenic, and chondrogenic differentiation. In this study, these stem cells were found to be positive for CD29, CD44, and CD73. The exosomes were centrally located with a diameter of 50-100 nm. CD63 and Tsg101 were highly expressed while the expression of Calnexin was suppressed. The exosomes can be ingested by NPCs. USCs-exos significantly improved ER stress responses and inhibited excessive activation of the unfolded protein response (UPR) as well as cell apoptosis and disc degeneration through the AKT and ERK signaling pathways (p < 0.05).

Conclusion

Through the AKT and ERK signaling pathways, USCs-exos significantly inhibit ER stress-induced cell apoptosis and IDD under pressure conditions. It is, therefore, a viable therapeutic strategy.

Transformation of resident notochord-descendent nucleus pulposus cells in mouse injury-induced fibrotic intervertebral discs

Intervertebral disc degeneration (IDD), a major cause of low back pain, occurs with ageing. The core of the intervertebral disc, the nucleus pulposus (NP), embedded in a proteoglycan‐rich and gelatinous matrix, is derived from the embryonic notochord. With IDD, the NP becomes fibrous, containing fewer cells, which are fibroblastic and of unknown origin. Here, we used a lineage tracing strategy to investigate the origin of cells in the NP in injury‐induced mouse IDD. We established a Foxa2 notochord‐specific enhancer‐driven Cre transgenic mouse model (Foxa2mNE‐Cre) that acts only in the embryonic to foetal period up to E14.5, to genetically label notochord cells with enhanced green fluorescent protein (EGFP). When this mouse is crossed to one carrying a Cre recombinase reporter, Z/EG, EGFP‐labelled NP cells are present even at 2 years of age, consistent with their notochordal origin. We induced tail IDD in Foxa2mNE‐Cre; Z/EG mice by annulus puncture and observed the degenerative changes for 12 weeks. Soon after puncture, EGFP‐labelled NP cells showed strong Col2a1+ expression unlike uninjured control NP. Later, accompanying fibrotic changes, EGFP‐positive NP cells expressed fibroblastic and myofibroblastic markers such as Col1a1, ASMA, FAPA and FSP‐1. The number of EGFP+ cells co‐expressing the fibroblastic markers increased with time after puncture. Our findings suggest resident NP cells initially upregulate Col2a1+ and later transform into fibroblast‐like cells during injury‐mediated disc degeneration and remodelling. This important discovery concerning the cellular origin of fibrotic pathology in injury‐induced IDD has implications for management in disease and ageing.

Exosome-Transported circRNA_0000253 Competitively Adsorbs MicroRNA-141-5p and Increases IDD

The pathogenesis of intervertebral disc degeneration (IDD) is complex, and a better understanding of IDD pathogenesis may provide a better method for the treatment of IDD. Exosomes are 40-100 nm nanosized vesicles that are released from many cell types into the extracellular space. We speculated that exosome-transported circular RNAs (circRNAs) could regulate IDD. Exosomes from different degenerative grades were isolated and added to nucleus pulposus cells (NPCs), and indicators of proliferation and apoptosis were detected. Based on the previous circRNA microarray results, the top 10 circRNAs were selected. PCR was performed to determine the circRNA with the maximum upregulation. Competing endogenous RNA (ceRNA) analysis was carried out, and the sponged microRNA (miRNA) was identified. Further functional verification of the selected circRNA was carried out in vivo and in vitro. NPCs of different degenerative grades secreted exosomes, which could regulate IDD. circRNA_0000253 was selected as having the maximum upregulation in degenerative NPC exosomes. ceRNA analysis showed that circRNA_0000253 could adsorb miRNA-141-5p to downregulate SIRT1. circRNA_0000253 was confirmed to increase IDD by adsorbing miRNA-141-5p and downregulating SIRT1 in vivo and in vitro. Exosomal circRNA_0000253 owns the maximum upregulation in degenerative NPC exosomes and could promote IDD by adsorbing miRNA-141-5p and downregulating SIRT1.

Understanding embryonic development for cell-based therapies of intervertebral disc degeneration: Toward an effort to treat disc degeneration subphenotypes

Chronic low back and neck pain are associated with intervertebral disc degeneration and are major contributors to the global burden of disability. New evidence now suggests that disc degeneration comprises a spectrum of subphenotypes influenced by genetic background, age, and environmental factors, which may be contributing to the mixed outcomes seen in clinical trials of cell-based therapies that aim to treat disc degeneration. This problem is further compounded by the fact that disc degeneration and aging coincide with an exhaustion of endogenous progenitor cells, imposing limitations on the regenerative capacity of the disc. At the bench-side, current work is focused on applying our knowledge of embryonic disc development to direct and refine differentiation of adult and human-induced pluripotent stem cells into notochord-like and nucleus pulposus-like cells for use in novel cell-based therapies. Accordingly, this review presents the salient features of intervertebral disc development, post-natal maintenance, and regeneration, with emphasis on recent advancements. We also discuss how a stratified approach can be undertaken for the development of future cell-based therapies to bring emerging subphenotypes into consideration.

Mesenchymal stem cells-derived exosomes ameliorate nucleus pulposus cells apoptosis via delivering miR-142-3p: therapeutic potential for intervertebral disc degenerative diseases

Intervertebral disc degeneration (IDD) is the main cause of lower back pain (LBP), and puzzles massive individuals worldwide. Mesenchymal stem cells (MSCs) transplantation has been demonstrated to potentially ameliorate IDD progression, while the underlying mechanism has not been fully explained. Interleukin-1β (IL-1β) was used to induce nucleus pulposus cells (NPCs) injury. Bone marrow MSCs-derived exosomes were isolated using the super centrifugation method, and characterized using Transmission electron microscopy (TEM) and western blot. Cell viability was determined by MTT, while apoptosis was measured by Annexin-V staining using flow cytometry. miR-142-3fp and gene expressions were measured by real-time PCR. The protein expressions were determined by western blot. Herein, we found exosomes from bone marrow MSCs are circular vesicles, about 80 nm in diameter, and with robust expression of TSG101 and CD63, but without of Calnexin. MSCs exosomes alleviated NPCs apoptosis by reducing IL-1β-induced inflammatory cytokines secretion and MAPK signaling activation. Additionally, MSCs exosomes inhibited NPCs apoptosis and MAPK signaling by delivering miR-142-3p that targets mixed lineage kinase 3 (MLK3). Overexpression of MLK3 abolished the effects of MSCs exosomes on the inflammatory condition, cell apoptosis, and MAPK signaling activation in NPCs. The results confirmed that bone marrow MSCs-derived exosomes-packaged miR-142-3p alleviates NPCs injury through suppressing MAPK signaling by targeting MLK3. The work highlights the therapeutic effect of MSCs on IDD progression, and bone marrow MSCs exosomes might be apromising therapeutic strategy for IDD.

Optimization of a rat lumbar IVD degeneration model for low back pain

INTRODUCTION

Intervertebral disc (IVD) degeneration is often associated with low back pain and radiating leg pain. The purpose of this study is to develop a reproducible and standardized preclinical model of painful lumbar IVD degeneration by evaluation of structural and behavioral changes in response to IVD injury with increasing needle sizes. This model can be used to develop new therapies for IVD degeneration.

METHODS

Forty-five female Sprague Dawley rats underwent anterior lumbar disc needle puncture at levels L4-5 and L5-6 under fluoroscopic guidance. Animals were randomly assigned to four different experimental groups: needle sizes of 18 Gauge (G), 21G, 23G, and sham control. To monitor the progression of IVD degeneration and pain, the following methods were employed: μMRI, qRT-PCR, histology, and biobehavioral analysis.

RESULTS

T1- and T2-weighted μMRI analysis showed a correlation between the degree of IVD degeneration and needle diameter, with the most severe degeneration in the 18G group. mRNA expression of markers for IVD degeneration markers were dysregulated in the 18G and 21G groups, while pro-nociceptive markers were increased in the 18G group only. Hematoxylin and Eosin (H&E) and Alcian Blue/Picrosirius Red staining confirmed the most pronounced IVD degeneration in the 18G group. Randall-Selitto and von Frey tests showed increased hindpaw sensitivity in the 18G group.

CONCLUSION

Our findings demonstrate that anterior disc injury with an 18G needle creates severe IVD degeneration and mechanical hypersensitivity, while the 21G needle results in moderate degeneration with no increased pain sensitivity. Therefore, needle sizes should be selected depending on the desired phenotype for the pre-clinical model.

Effect of sIL-13Rα2-Fc on the progression of rat tail intervertebral disc degeneration

BACKGROUND

The incidence of degenerative disc disease caused by intervertebral disc injury is increasing annually, seriously affecting the quality of life of patients and increasing the disease burden on society. The mechanisms of intervertebral disc degeneration include changes in extracellular matrix (ECM) deposition and tissue fibrosis. sIL-13Rα2-Fc potently inhibits interleukin (IL)-13, as well as blocks related cell signaling pathways and inhibits fibrosis in certain tissues. However, it is unknown whether sIL-13Rα2-Fc inhibits fibrosis in injured intervertebral discs and slows the process of degeneration. We hypothesized that sIL-13Rα2-Fc delays the progression of intervertebral disc degeneration by inhibiting intervertebral disc fibrosis and improving ECM deposition.

METHODS

A rat tail intervertebral disc degeneration model was established. Pathological changes in rat intervertebral disc tissue were observed by hematoxylin and eosin staining and Masson staining. Glycosaminoglycan (GAG), chondroitin sulfate (CS), keratan sulfate (KS), and hyaluronic acid (HA) contents were quantitatively analyzed by enzyme-linked immunosorbent assay. Type I and type II collagen expression levels were analyzed by reverse transcription-PCR and western blotting.

RESULTS

Hematoxylin and eosin staining and Masson staining revealed annulus fibrosus rupture, disordered arrangement, decreased nucleus pulposus tissue, and decreased collagen fiber in the rat intervertebral disc tissue. Following treatment with sIL-13Rα2-Fc, pathological changes in the rat intervertebral disc were reduced. Rat intervertebral disc tissue showed decreased GAG, CS-KS, and (HA) contents, increased type I collagen levels, and decreased type II collagen levels in degenerated intervertebral discs. sIL-13Rα2-Fc intervention increased the contents of GAG, CS, KS, and HA; inhibited the expression of type I collagen; and promoted the expression of type II collagen.

CONCLUSION

These results demonstrate that intervertebral disc degeneration is associated with tissue fibrosis. sIL-13Rα2-Fc can regulate type I and type II collagen expression levels by increasing GAG, CS, KS, and HA contents, thereby slowing the progression of intervertebral disc degeneration.

Bone marrow-derived mesenchymal stem cells in three-dimensional co-culture attenuate degeneration of nucleus pulposus cells

Intervertebral disc degeneration (IDD) is an irreversible aging-associated clinical condition of unclear etiology. Mesenchymal stem cells (MSCs) have the potential to delay IDD, but the mechanisms by which MSCs attenuate senescence-related degeneration of nucleus pulposus cells (NPCs) remain uncertain. The present study employed a three-dimensional (3D) co-culture system to explore the influence of MSCs on NPC degeneration induced by TNF-α in rat cells. We found that co-culture with bone marrow-derived MSCs (BMSCs) reduced senescence-associated β-galactosidase expression, increased cell proliferation, decreased matrix metalloproteinase 9, increased Coll-IIa production, and reduced TGFβ/NF-κB signaling in senescent NPCs. In addition, expression of zinc metallopeptidase STE24 (ZMPSTE24), whose dysfunction is related to premature cell senescence and aging, was decreased in senescent NPCs but restored upon BMSC co-culture. Accordingly, ZMPSTE24 overexpression in NPCs inhibited the pro-senescence effects of TGFβ/NF-κB activation upon TNF-α stimulation, while both CRISPR/Cas9-mediated silencing and pharmacological ZMPSTE24 inhibition prevented those effects. Ex-vivo experiments on NP explants provided supporting evidence for the protective effect of MSCs against NPC senescence and IDD. Although further molecular studies are necessary, our results suggest that MSCs may attenuate or prevent NP fibrosis and restore the viability and functional status of NPCs through upregulation of ZMPSTE24.

Intervertebral disc regeneration: From cell therapy to the development of novel bioinspired endogenous repair strategies

Low back pain (LBP), frequently associated with intervertebral disc (IVD) degeneration, is a major public health concern. LBP is currently managed by pharmacological treatments and, if unsuccessful, by invasive surgical procedures, which do not counteract the degenerative process. Considering that IVD cell depletion is critical in the degenerative process, the supplementation of IVD with reparative cells, associated or not with biomaterials, has been contemplated. Recently, the discovery of reparative stem/progenitor cells in the IVD has led to increased interest in the potential of endogenous repair strategies. Recruitment of these cells by specific signals might constitute an alternative strategy to cell transplantation. Here, we review the status of cell-based therapies for treating IVD degeneration and emphasize the current concept of endogenous repair as well as future perspectives. This review also highlights the challenges of the mobilization/differentiation of reparative progenitor cells through the delivery of biologics factors to stimulate IVD regeneration.

Use of Allogeneic Hypoxic Mesenchymal Stem Cells For Treating Disc Degeneration in Rabbits

Intervertebral discs (IVDs) are important biomechanical components of the spine. Once degenerated, mesenchymal stem cell (MSC)-based therapies may aid in the repair of these discs. Although hypoxic preconditioning enhances the chondrogenic potential of MSCs, it is unknown whether bone marrow MSCs expanded under hypoxic conditions (1% O₂ , here referred to as hypoxic MSCs) are better than bone marrow MSCs expanded under normoxic conditions (air, here referred to as normoxic MSCs) with regards to disc regeneration capacity. The purpose of this study was to compare the therapeutic effects of hypoxic and normoxic MSCs in a rabbit needle puncture degenerated disc model after intra-disc injection. Six weeks after needle puncture, MSCs were injected into the IVD. A vehicle-treated group and an un-punctured sham-control group were included as controls. The tissues were analyzed by histological and immunohistochemical methods 6 and 12 weeks post-injection. At 6 and 12 weeks, less disc space narrowing was evident in the hypoxic MSC-treated group compared to the normoxic MSC-treated group. Significantly better histological scores were observed in the hypoxic MSC group. Discs treated with hypoxic MSCs also demonstrated significantly better extracellular matrix deposition in type II and XI collagen. Increased CD105 and BMP-7 expression were also observed upon injection of hypoxic MSCs. In conclusion, hypoxic MSC injection was more effective than normoxic MSC injection for reducing IVD degeneration progression in vivo. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1440-1450, 2019.

Exosomes from mesenchymal stem cells modulate endoplasmic reticulum stress to protect against nucleus pulposus cell death and ameliorate intervertebral disc degeneration in vivo

Objectives: Intervertebral disc degeneration (IDD) is widely accepted as a cause of low back pain and related degenerative musculoskeletal disorders. Nucleus pulposus (NP) cell apoptosis which is related to excessive endoplasmic reticulum (ER) stress in the intervertebral disc (IVD) could aggravate IDD progression. Many studies have shown the therapeutic potential of exosomes derived from bone marrow mesenchymal stem cells (MSC-exos) in degenerative diseases. We hypothesized that the delivery of MSC-exos could modulate ER stress and inhibit excessive NP cell apoptosis during IDD.

Methods: The ER stress levels were measured in normal or degenerative NP tissues for contrast. The effects of MSC-exos were testified in advanced glycation end products (AGEs) -induced ER stress in human NP cells. The mechanism involving AKT and ERK signaling pathways was investigated using RNA interference or signaling inhibitors. Histological or immunohistochemical analysis and TUNEL staining were used for evaluating MSC-exos therapeutic effects in vivo.

Results: The ER stress level and apoptotic rate was elevated in degenerative IVD tissues. MSC-exos could attenuate ER stress-induced apoptosis by activating AKT and ERK signaling. Moreover, delivery of MSC-exos in vivo modulated ER stress-related apoptosis and retarded IDD progression in a rat tail model.

Conclusions: These results highlight the therapeutic effects of exosomes in preventing IDD progression. Our work is the first to demonstrate that MSC-exos could modulate ER stress-induced apoptosis during AGEs-associated IVD degeneration.

Efficacy of administered mesenchymal stem cells in the initiation and co-ordination of repair processes by resident disc cells in an ovine (Ovis aries) large destabilizing lesion model of experimental disc degeneration

BACKGROUND

Forty percent of low back pain cases are due to intervertebral disc degeneration (IVDD), with mesenchymal stem cells (MSCs) a reported treatment. We utilized an ovine IVDD model and intradiscal heterologous MSCs to determine therapeutic efficacy at different stages of IVDD.

METHODOLOGY

Three nonoperated control (NOC) sheep were used for MSC isolation. In 36 sheep, 6 × 20 mm annular lesions were made at three spinal levels using customized blades/scalpel handles, and IVDD was allowed to develop for 4 weeks in the Early (EA) and late Acute (LA) groups, or 12 weeks in the chronic (EST) group. Lesion IVDs received injections of 10 × 106 MSCs or PBS, and after 8 (EA), 22 (LA) or 14 (EST) weeks recuperation the sheep were sacrificed. Longitudinal lateral radiographs were used to determine disc heights. IVD glycosaminoglycan (GAG) and hydroxyproline contents were quantified using established methods. An Instron materials testing machine and customized jigs analyzed IVD (range of motion, neutral zone [NZ] and stiffness) in flexion/extension, lateral bending and axial rotation. qRTPCR gene profiles of key anabolic and catabolic matrix molecules were undertaken. Toluidine blue and hematoxylin and eosin stained IVD sections were histopathologically scoring by two blinded observers.

RESULTS

IVDD significantly reduced disc heights. MSC treatment restored 95% to 100% of disc height, maximally improved NZ and stiffness in flexion/extension and lateral bending in the EST group, restoring GAG levels. With IVDD qRTPCR demonstrated elevated catabolic gene expression (MMP2/3/9/13, ADAMTS4/5) in the PBS IVDs and expession normalization in MSC-treated IVDs. Histopathology degeneracy scores were close to levels of NOC IVDs in MSC IVDs but IVDD developed in PBS injected IVDs.

DISCUSSION

Administered MSCs produced recovery in degenerate IVDs, restored disc height, composition, biomechanical properties, down regulated MMPs and fibrosis, strongly supporting the efficacy of MSCs for disc repair.

Autogenic mesenchymal stem cells for intervertebral disc regeneration

PURPOSE

A systematic review of the literature was conducted to clarify the outcomes of autologous mesenchymal stem cells (MSC) injections for the regeneration of the intervertebral disc (IVD).

METHODS

The following databases were accessed: PubMed, Medline, CINAHL, Cochrane, Embase and Google Scholar bibliographic databases. Articles including previous or planned surgical interventions were excluded. Only articles reporting percutaneous autologous MSC injection to regenerate IVD in humans were included. We referred to the Coleman Methodology Score for the methodological quality assessment. The statistical analysis was performed using Review Manager Software 5.3.

RESULTS

After the databases search and cross-references of the bibliographies, seven studies were included in the present work. The funnel plot detected low risk of publication bias. The Coleman Methodology Score reported a good result, scoring 61.07 points. A total of 98 patients were enrolled, with 122 treated levels. All the patients underwent conservative therapies prior to injection. A remarkable improvement in the quality of life were reported after the treatment. The average Oswestry Disability Index (ODI) improved from "severe disability" to "minimal disability" at one year follow-up. The visual analogue scale (VAS) showed an improvement of ca. 30% at one year follow-up. Only one case of herniated nucleus pulposus was reported. No other adverse events at the aspiration or injection site were observed.

CONCLUSIONS

This systematic review of the literature proved MSC injection to be a safe and feasible option for intervertebral disc regeneration in the early-degeneration stage patients. Irrespective of the source of the MSCs, an overall clinical and radiological improvement of the patients has been evidenced, as indeed a very low complication rate during the follow-up.

Sustained and Bioresponsive Two-Stage Delivery of Therapeutic miRNA via Polyplex Micelle-Loaded Injectable Hydrogels for Inhibition of Intervertebral Disc Fibrosis

Intervertebral disc degeneration (IDD) is frequently caused by gradual pathological changes inside intervertebral discs (IVDs) and progressive fibrosis. MicroRNA-29 (miR-29) family possesses potent fibrosis suppression capability, but their application for treatment of chronic IDD is limited due to lack of suitable local delivery systems. In this report, given various overexpressed matrix metalloproteinases (MMPs) during IDD, injectable MMP-degradable hydrogels encapsulating MMP-responsive polyplex micelles are developed for sustained and bioresponsive delivery of miR-29a into nucleus pulposus cells via a two-stage process. Cationic block copolymers are designed to complex miR-29a, and subsequently mixed with the poly(ethylene glycol) (PEG) gelation precursors and MMP-cleavable peptide cross-linkers for in situ formation of polyplex micelle-encapsulated hydrogels in the diseased IVDs. In the presence of MMPs, the polyplex micelles are first released by MMP cleavage of the hydrogels, and subsequently, MMPs-responsive detachment of PEG shells from polyplex micelles contributes to efficient cellular uptake and endosomal escape. MiR-29a is demonstrated to effectively silence the expression of MMP-2, inhibit the fibrosis process, and reverse IDD in animal models through blocking the β-catenin translocation pathway from the cytoplasm to the nucleus. This two-stage bioresponsive local miRNA delivery system represents a novel and promising strategy for the treatment of chronic IDD.

Disc cell therapy with bone-marrow-derived autologous mesenchymal stromal cells in a large porcine disc degeneration model

PURPOSE

Disc regeneration through matrix-assisted autologous mesenchymal stromal cell therapy seems promising against disc degeneration with convincing results in small animal models. Whether these positive results can be transferred to larger animal models or humans is unclear.

METHODS

Fibrin matrix-assisted autologous bone-marrow-derived mesenchymal stromal cell therapy was compared to acellular fibrin matrix therapy in a porcine in vivo model. First, disc degeneration was induced by annular puncture and partial nucleotomy with a large 16G-needle, and 12 weeks later, disc therapy was performed in a second surgery with a thinner 26G needle. Seventy-two lumbar discs from 12 aged adult pigs were evaluated by histology, micro-CT, and gene expression analysis 13 and 24 weeks after nucleotomy and 1 and 12 weeks after treatment, respectively.

RESULTS

Radiologic disc height was not significantly different in both treatment groups. In the semi-quantitative histologic degeneration score, significant disc degeneration was still evident 1 week after treatment both in the mesenchymal stromal cell group and in the acellular fibrin matrix group. 12 weeks after treatment, degeneration was, however, not further increased and mesenchymal-stromal-cell-treated discs showed significantly less disc degeneration in the annulus fibrosus (p = 0.02), whereas reduction in the nucleus pulposus did not reach statistical significance. Cell treatment compared to matrix alone found less Col1 gene expression as a marker for fibrosis and more expression of the trophic factor BMP2 in the nucleus pulposus, whereas the inflammation marker IL1ß was reduced in the annulus fibrosus.

CONCLUSIONS

Disc treatment with fibrin matrix-assisted autologous mesenchymal stromal cells reduced degenerative findings compared to acellular fibrin matrix alone. Regenerative changes, however, were not significant for all parameters showing limitations in a large biomechanically demanding model with aged discs. These slides can be retrieved under Electronic Supplementary Material.

Stromal cell-derived factor-1α-encapsulated albumin/heparin nanoparticles for induced stem cell migration and intervertebral disc regeneration in vivo

Intervertebral disc (IVD) degeneration may cause many diseases and pain. Stem cell migration toward the site of IVD degeneration is a key factor for IVD regeneration. In the current study, we prepared albumin/heparin nanoparticles (BHNPs) as injectable carriers of stromal cell-derived factor-1α (SDF-1α, also known as C-X-C motif chemokine 12), a powerful chemoattractant for the homing of bone marrow resident mesenchymal stem cells (MSCs), for protection of the molecule against degradation for a sustained release. The NPs have relatively uniform small size, with a diameter of about 110 nm. The NPs possess a high loading capacity of SDF-1α with a sustained release profile. The bioactivity of the obtained BHNPs/SDF was then studied in vitro and in vivo. The BHNPs/SDF can induce migration of MSCs in a dose-dependent manner in vitro. After injected into the damaged disc, BHNPs/SDF induce much better regeneration of annulus fibrosus and nucleus pulposus, compared to SDF-1α and BHNPs alone, evidenced with better histological grade scores and higher expression of SOX9, Aggrecan, and Collagen type II at the level of both mRNA and protein. This study provides a simple nanoplatform to load SDF-1α and protect it against degradation, with potential application in inductive tissue regeneration in vivo.

STATEMENT OF SIGNIFICANCE

Stem cell migration toward the site of IVD degeneration is a key event to promote IVD regeneration. In the current study, we prepared albumin/heparin nanoparticles (BHNPs) as injectable carriers to protect SDF-1α against degradation and for the sustained release of the molecule. After injected into the damaged disc, BHNPs/SDF induced much better regeneration of IVD, compared to SDF-1α and BHNPs alone. This study provides a simple nanoplatform to load SDF-1α and protect it from degradation, with potential application in inductive tissue regeneration in vivo.

Mesenchymal progenitor cells primed with pentosan polysulfate promote lumbar intervertebral disc regeneration in an ovine model of microdiscectomy

BACKGROUND CONTEXT

Neural compression associated with lumbar disc herniation is usually managed surgically by microdiscectomy. However, 10%-20% of patients re-present with debilitating back pain, and approximately 15% require further surgery.

PURPOSE

Using an ovine model of microdiscectomy, the present study investigated the relative potential of pentosan polysulfate-primed mesenchymal progenitor cells (pMPCs) or MPC alone implanted into the lesion site to facilitate disc recovery.

STUDY DESIGN

An ovine model of lumbar microdiscectomy was used to compare the relative outcomes of administering MPCs or pMPCs to the injury site postsurgery.

METHODS

At baseline 3T magnetic resonance imaging (MRI) of 18 adult ewes was undertaken followed by annular microdiscectomy at two lumbar disc levels. Sheep were randomized into three groups (n=6). The injured controls received no further treatment. Defects of the treated groups were implanted with a collagen sponge and MPC (5×10⁵ cells) or pMPC (5×10⁵ cells). After 6 months, 3T MRI and standard radiography were performed. Spinal columns were dissected, individual lumbar discs were sectioned horizontally, and nucleus pulposus (NP) and annulus fibrosus (AF) regions were assessed morphologically and histologically. The NP and AF tissues were dissected into six regions and analyzed biochemically for their proteoglycans (PGs), collagen, and DNA content.

RESULTS

Both the MPC- and pMPC-injected groups exhibited less reduction in disc height (p<.05) and lower Pfirrmann grades (p≤.001) compared with the untreated injury controls, but morphologic scores for the pMPC-injected discs were lower (p<.05). The PG content of the AF injury site region (AF1) of pMPC discs was higher than MPC and injury control AF1 (p<.05). At the AF1 and contralateral AF2 regions, the DNA content of pMPC discs was significantly lower than injured control discs and MPC-injected discs. Histologic and birefringent microscopy revealed increased structural organization and reduced degeneration in pMPC discs compared with MPC and the injured controls.

CONCLUSIONS

In an ovine model 6 months after administration of pMPCs to the injury site disc PG content and matrix organization were improved relative to controls, suggesting pMPCs' potential as a postsurgical adjunct for limiting progression of disc degeneration after microdiscectomy.

Transplantation of Hypoxic-Preconditioned Bone Mesenchymal Stem Cells Retards Intervertebral Disc Degeneration via Enhancing Implanted Cell Survival and Migration in Rats

Objective

Special hypoxic and hypertonic microenvironment in intervertebral discs (IVDs) decreases the treatment effect of cell transplantation. We investigated the hypothesis that hypoxic preconditioning (HP) could improve the therapeutic effect of bone mesenchymal stem cells (BMSCs) to IVD degeneration.

Methods

BMSCs from green fluorescent protein-transgenic rats were pretreated with cobalt chloride (CoCl₂, 100 μM, 24 h) for hypoxic conditions in vitro. Apoptosis (related pathways of caspase-3 and bcl-2) and migration (related pathways of HIF-1α and CXCR4) were detected in BMSCs. In vivo, BMSCs and HP BMSCs (H-BMSCs) were injected into the rat model of IVD degeneration. The IVD height, survival, migration, and differentiation of transplanted BMSCs and matrix protein expression (collagen II, aggrecan, and MMP-13) were tested.

Results

H-BMSCs could extensively decrease IVD degeneration by increasing IVD height and collagen II and aggrecan expressions when compared with BMSCs. Significantly, more GFP-positive BMSCs were observed in the nucleus pulposus and annulus fibrosus regions of IVD. HP could significantly decrease BMSC apoptosis (activating bcl-2 and inhibiting caspase-3) and improve BMSC migration (increasing HIF-1α and CXCR4) in vitro.

Conclusion

HP could significantly enhance the capacity of BMSCs to repair DDD by increasing the survival and migration of implanted cells and increasing matrix protein expression.