Wharton's Jelly mesenchymal stromal cell-derived extracellular vesicles promote nucleus pulposus cell anabolism in an in vitro 3D alginate-bead culture model

Background

Intradiscal transplantation of mesenchymal stromal cells (MSCs) has emerged as a promising therapy for intervertebral disc degeneration (IDD). However, the hostile microenvironment of the intervertebral disc (IVD) may compromise the survival of implanted cells. Interestingly, studies reported that paracrine factors, such as extracellular vesicles (EVs) released by MSCs, may regenerate the IVD. The aim of this study was to investigate the therapeutic effects of Wharton's Jelly MSC (WJ-MSC)-derived EVs on human nucleus pulposus cells (hNPCs) using an in vitro 3D alginate-bead culture model.

Methods

After EV isolation and characterization, hNPCs isolated from surgical specimens were encapsulated in alginate beads and treated with 10, 50, and 100 μg/mL WJ-MSC-EVs. Cell proliferation and viability were assessed by flow cytometry and live/dead staining. Nitrite and glycosaminoglycan (GAG) content was evaluated through Griess and 1,9-dimethylmethylene blue assays. hNPCs in alginate beads were paraffin-embedded and stained for histological analysis (hematoxylin-eosin and Alcian blue) to assess extracellular matrix (ECM) composition. Gene expression levels of catabolic (MMP1, MMP13, ADAMTS5, IL6, NOS2), anabolic (ACAN), and hNPC marker (SOX9, KRT19) genes were analyzed through qPCR. Collagen type I and type II content was assessed with Western blot analysis.

Results

Treatment with WJ-MSC-EVs resulted in an increase in cell content and a decrease in cell death in degenerated hNPCs. Nitrite production was drastically reduced by EV treatment compared to the control. Furthermore, proteoglycan content was enhanced and confirmed by Alcian blue histological staining. EV stimulation attenuated ECM degradation and inflammation by suppressing catabolic and inflammatory gene expression levels. Additionally, NPC phenotypic marker genes were also maintained by the EV treatment.

Conclusions

WJ-MSC-derived EVs ameliorated hNPC growth and viability, and attenuated ECM degradation and oxidative stress, offering new opportunities for IVD regeneration as an attractive alternative strategy to cell therapy, which may be jeopardized by the harsh microenvironment of the IVD.

Selective cargo sorting in stem cell-derived small extracellular vesicles: impact on therapeutic efficacy for intervertebral disc degeneration

BACKGROUND

Growing evidence has suggested the role of stem cell-derived small extracellular vesicles (sEVs) in intervertebral disc degeneration (IVDD). The cargo sorting of sEVs, particularly miRNAs, may be influenced when the donor cell is subjected to oxidative stress. Here, we discovered that miRNAs containing specific motifs are selectively sorted into intraluminal vesicles within mesenchymal stem cells (MSCs) in response to oxidative stress.

METHODS

Analysis of miRNA cargoes in sEVs derived from normal MSCs (C-sEVs) or stressed MSCs (T-sEVs) was conducted using miRNA sequencing. Differential expressed miRNAs in sEVs and the identification of motifs were evaluated through bioinformatics analysis. Protein binding was assessed using immunofluorescent staining and immunoprecipitation analysis. Additionally, RNA pull down and RNA immunoprecipitation (RIP) immunoprecipitation were employed to determine the binding between miRNAs and proteins. The effects of C-sEVs and T-sEVs on IVDD were compared by detecting the expression levels of phenotypic genes in vitro or histological evaluation in vivo.

RESULTS

The sorting process of miRNAs is mediated by the nucleocytoplasmic transport of heterogeneous nuclear ribonucleoproteins, which in turn facilitates the phosphorylation of SNAP25 and promotes the transport and secretion of sEVs. Additionally, CHMP1B plays a role in membrane repair and protects against cell ferroptosis upon oxidative stress, concurrently affecting the release of sEVs. Notably, stem cell-derived sEVs associated with ferroptosis impair the therapeutic efficacy for IVDD. However, the application of engineered sEVs containing a specific miRNA inhibitor exhibits the potential to reinstate the therapeutic efficacy for IVDD both in vitro and in vivo.

CONCLUSIONS

Taken together, our findings shed light on the mechanism of miRNAs sorting into sEVs and offer new insights for the optimization of sEV-based treatments during intervertebral disc regeneration. regeneration.

Enhanced Intervertebral Disc Repair via Genetically Engineered Mesenchymal Stem Cells with Tetracycline Regulatory System

The therapeutic potential of Mesenchymal stem cells (MSCs) for the treatment of Intervertebral disc (IVD) degeneration can be enhanced by amplifying specific cytokines and proteins. This study aimed to investigate the therapeutic potential of tetracycline-off system-engineered tonsil-derived mesenchymal stem cells (ToMSC-Tetoff-TGFβ1-IGF1-BMP7) for treating intervertebral disc (IVD) degeneration. ToMSCs were isolated from a tonsillectomy patient and genetically modified with four distinct plasmids via CRISPR/Cas9-mediated knock-in gene editing. Transgene expression was confirmed through immunofluorescence, western blots, and an enzyme-linked immunosorbent assay for transforming growth factor beta 1 (TGFβ1) protein secretion, and the effect of MSC-TetOff-TGFβ1-IGF1-BMP7 on disc injury was assessed in a rat model. The ToMSC-Tetoff-TGFβ1-IGF1-BMP7 treatment exhibited superior therapeutic effects compared to ToMSC-TGFβ1, and ToMSC-SDF1α implantation groups, stimulating the regeneration of nucleus pulposus (NP) cells crucial for IVD. The treatment showed potential to restore the structural integrity of the extracellular matrix (ECM) by upregulating key molecules such as aggrecan and type II collagen. It also exhibited anti-inflammatory properties and reduced pain-inducing neuropeptides. ToMSC-Tetoff-TGFβ1-IGF1-BMP7 holds promise as a novel treatment for IVD degeneration. It appears to promote NP cell regeneration, restore ECM structure, suppress inflammation, and reduce pain. However, more research and clinical trials are required to confirm its therapeutic potential.

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

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

Direct Reprogramming and Induction of Human Dermal Fibroblasts to Differentiate into iPS-Derived Nucleus Pulposus-like Cells in 3D Culture

Intervertebral disc (IVD) diseases are common spinal disorders that cause neck or back pain in the presence or absence of an underlying neurological disorder. IVD diseases develop on the basis of degeneration, and there are no established treatments for degeneration. IVD diseases may therefore represent a candidate for the application of regenerative medicine, potentially employing normal human dermal fibroblasts (NHDFs) induced to differentiate into nucleus pulposus (NP) cells. Here, we used a three-dimensional culture system to demonstrate that ectopic expression of MYC, KLF4, NOTO, SOX5, SOX6, and SOX9 in NHDFs generated NP-like cells, detected using Safranin-O staining. Quantitative PCR, microarray analysis, and fluorescence-activated cell sorting revealed that the induced NP cells exhibited a fully differentiated phenotype. These findings may significantly contribute to the development of effective strategies for treating IVD diseases.

Development of a standardized histopathology scoring system for intervertebral disc degeneration and regeneration in rabbit models-An initiative of the ORSspine section

BACKGROUND

The rabbit lumbar spine is a commonly utilized model for studying intervertebral disc degeneration and for the pre-clinical evaluation of regenerative therapies. Histopathology is the foundation for which alterations to disc morphology and cellularity with degeneration, or following repair or treatment are assessed. Despite this, no standardized histology grading scale has yet been established for the spine field for any of the frequently utilized animal models.

AIMS

The purpose of this study was to establish a new standardized scoring system to assess disc degeneration and regeneration in the rabbit model.

MATERIALS AND METHODS

The scoring system was formulated following a review of the literature and a survey of spine researchers. Validation of the scoring system was carried out using images provided by 4 independent laboratories, which were graded by 12 independent graders of varying experience levels. Reliability testing was performed via the computation of intra-class correlation coefficients (ICC) for each category and the total score. The scoring system was then further refined based on the results of the ICC analysis and discussions amongst the authors.

RESULTS

The final general scoring system involves scoring 7 features (nucleus pulposus shape, area, cellularity and matrix condensation, annulus fibrosus/nucleus pulposus border appearance, annulus fibrosus morphology, and endplate sclerosis/thickening) on a 0 (healthy) to 2 (severe degeneration) scale. ICCs demonstrated overall moderate to good agreement across graders. An addendum to the main scoring system is also included for use in studies evaluating regenerative therapeutics, which involves scoring cell cloning and morphology within the nucleus pulposus and inner annulus fibrosus.

DISCUSSION

Overall, this new scoring system provides an avenue to improve standardization, allow a more accurate comparison between labs and more robust evaluation of pathophysiology and regenerative treatments across the field.

CONCLUSION

This study developed a histopathology scoring system for degeneration and regeneration in the rabbit model based on reported practice in the literature, a survey of spine researchers, and validation testing.

Development of a standardized histopathology scoring system for intervertebral disc degeneration in rat models: An initiative of the ORS spine section

BACKGROUND

Rats are a widely accepted preclinical model for evaluating intervertebral disc (IVD) degeneration and regeneration. IVD morphology is commonly assessed using histology, which forms the foundation for quantifying the state of IVD degeneration. IVD degeneration severity is evaluated using different grading systems that focus on distinct degenerative features. A standard grading system would facilitate more accurate comparison across laboratories and more robust comparisons of different models and interventions.

AIMS

This study aimed to develop a histology grading system to quantify IVD degeneration for different rat models.

MATERIALS & METHODS

This study involved a literature review, a survey of experts in the field, and a validation study using 25 slides that were scored by 15 graders from different international institutes to determine inter- and intra-rater reliability.

RESULTS

A new IVD degeneration grading system was established and it consists of eight significant degenerative features, including nucleus pulposus (NP) shape, NP area, NP cell number, NP cell morphology, annulus fibrosus (AF) lamellar organization, AF tears/fissures/disruptions, NP-AF border appearance, as well as endplate disruptions/microfractures and osteophyte/ossification. The validation study indicated this system was easily adopted, and able to discern different severities of degenerative changes from different rat IVD degeneration models with high reproducibility for both experienced and inexperienced graders. In addition, a widely-accepted protocol for histological preparation of rat IVD samples based on the survey findings include paraffin embedding, sagittal orientation, section thickness < 10 μm, and staining using H&E and/or SO/FG to facilitate comparison across laboratories.

CONCLUSION

The proposed histological preparation protocol and grading system provide a platform for more precise comparisons and more robust evaluation of rat IVD degeneration models and interventions across laboratories.

Intervertebral Disc Regeneration Injection of a Cell-Loaded Collagen Hydrogel in a Sheep Model

Degenerated intervertebral discs (IVDs) were treated with autologous adipose-derived stem cells (ASC) loaded into an injectable collagen scaffold in a sheep model to investigate the implant's therapeutic potential regarding the progression of degeneration of previously damaged discs. In this study, 18 merino sheep were subjected to a 3-step minimally invasive injury and treatment model, which consisted of surgically induced disc degeneration, treatment of IVDs with an ASC-loaded collagen hydrogel 6 weeks post-operatively, and assessment of the implant's influence on degenerative tissue changes after 6 and 12 months of grazing. Autologous ASCs were extracted from subcutaneous adipose tissue and cultivated in vitro. At the end of the experiment, disc heights were determined by µ-CT measurements and morphological tissue changes were histologically examined.Histological investigations show that, after treatment with the ASC-loaded collagen hydrogel implant, degeneration-specific features were observed less frequently. Quantitative studies of the degree of degeneration did not demonstrate a significant influence on potential tissue regeneration with treatment. Regarding disc height analysis, at both 6 and 12 months after treatment with the ASC-loaded collagen hydrogel implant a stabilization of the disc height can be seen. A complete restoration of the intervertebral disc heights however could not be achieved.The reported injection procedure describes in a preclinical model a translational therapeutic approach for degenerative disc diseases based on adipose-derived stem cells in a collagen hydrogel scaffold. Further investigations are planned with the use of a different injectable scaffold material using the same test model.

The Application of Mesenchymal Stromal Cells and Their Homing Capabilities to Regenerate the Intervertebral Disc

Chronic low back pain (LBP) remains a challenging condition to treat, and especially to cure. If conservative treatment approaches fail, the current “gold standard” for intervertebral disc degeneration (IDD)-provoked back pain is spinal fusion. However, due to its invasive and destructive nature, the focus of orthopedic research related to the intervertebral disc (IVD) has shifted more towards cell-based therapeutic approaches. They aim to reduce or even reverse the degenerative cascade by mimicking the human body’s physiological healing system. The implementation of progenitor and/or stem cells and, in particular, the delivery of mesenchymal stromal cells (MSCs) has revealed significant potential to cure the degenerated/injured IVD. Over the past decade, many research groups have invested efforts to find ways to utilize these cells as efficiently and sustainably as possible. This narrative literature review presents a summary of achievements made with the application of MSCs for the regeneration of the IVD in recent years, including their preclinical and clinical applications. Moreover, this review presents state-of-the-art strategies on how the homing capabilities of MSCs can be utilized to repair damaged or degenerated IVDs, as well as their current limitations and future perspectives.

NOTO Transcription Factor Directs Human Induced Pluripotent Stem Cell-Derived Mesendoderm Progenitors to a Notochordal Fate

The founder cells of the Nucleus pulposus, the centre of the intervertebral disc, originate in the embryonic notochord. After birth, mature notochordal cells (NC) are identified as key regulators of disc homeostasis. Better understanding of their biology has great potential in delaying the onset of disc degeneration or as a regenerative-cell source for disc repair. Using human pluripotent stem cells, we developed a two-step method to generate a stable NC-like population with a distinct molecular signature. Time-course analysis of lineage-specific markers shows that WNT pathway activation and transfection of the notochord-related transcription factor NOTO are sufficient to induce high levels of mesendoderm progenitors and favour their commitment toward the notochordal lineage instead of paraxial and lateral mesodermal or endodermal lineages. This study results in the identification of NOTO-regulated genes including some that are found expressed in human healthy disc tissue and highlights NOTO function in coordinating the gene network to human notochord differentiation.

Evaluation of intervertebral disc regeneration with injection of mesenchymal stem cells encapsulated in PEGDA-microcryogel delivery system using quantitative T2 mapping: a study in canines

Intervertebral disc degeneration (IDD), the primary cause of low back pain, is still a great challenge to spinal surgeons and clinicians. T2 mapping, a biochemical magnetic resonance imaging (MRI) technique to calculate relaxation time, has the potential to offer a quantitative assessment of IDD. The aim of the study was to evaluate the regenerative effects of adipose-derived mesenchymal stem cells (MSCs) encapsulated in PEGDA-microcryogels (PMs) reinforced alginate hydrogel (AH) on the degenerative intervertebral disc (IVD) in a canine model using T2 mapping. Four degeneration-induced IVDs (L3-L4 to L6-L7) of 12 adult beagle dogs were injected with phosphate-buffered saline (PBS), MSCs, AH-PMs, and MSCs-laden AH-PMs, respectively. The intact IVD L7-S1 served as the normal control. IVD height change on plain radiograph, Pfirrmann grade and T2 relaxation time on MRI, histological change, and extracellular matrix (ECM)-associated proteins were evaluated during the 24-week follow-up period. Injection of MSCs-laden AH-PMs had the most satisfactory effects, having less decrease of IVD height, lower Pfirrmann grade, milder histological change, and longer T2 relaxation time (P < 0.05). T2 relaxation time was positively correlated with ECM content (proteoglycan: r = 0.85, P < 0.001; collagen II: r = 0.79, P < 0.001) and IVD height (r = 0.81, P < 0.001), but negatively correlated with Pfirrmann grade and histological grade (rho = -0.86, P < 0.001; rho = -0.95, P < 0.001). These results suggest that T2 mapping has the potential to quantitatively evaluate the repairing effects of cell-based engineering treatments on IDD for a long-term follow-up.

Evaluation of regenerative processes in the pig model of intervertebral disc degeneration after transplantation of bone marrow-derived mesenchymal stem cells. Folia Neuropathol. 2018;56:124-132. [PMID: 30509032 DOI: 10.5114/fn.2018.76616]

INTRODUCTION

The pathophysiology of degenerative disc disease (DDD) is complex and not fully understood. While surgical treatment and appropriate rehabilitation offer relief of acute symptoms, there is a need to find tissue engineering strategies for intervertebral disc repair to restore healthy higher and histological structure. The purpose of this study was to estimate the survival rate of transplanted cells and their post-delivery integration level at the damage site.

MATERIAL AND METHODS

We used an <i>in vivo</i> porcine model to investigate autogenic bone marrow-derived mesenchymal stem cell (BM-MSC) transplantation for intervertebral disc repair. In our experiment we used a large animal model of DDD induced by percutaneous laser light deliveries. The percutaneous approach has also been used for delivery of BM-MSCs into the intervertebral disc space.

RESULTS

After MSC transplantation, we observed a deceleration of the degenerative process in the intervertebral disc, relative to degenerative discs without MSC transplantation.

CONCLUSIONS

By using a large animal model that mimicked the development of intervertebral degenerative disc disease, the present results are indicative of the clinical feasibility of this procedure.

Role of Sonic Hedgehog Signaling Pathway in Intervertebral Disc Formation and Maintenance

a Purpose of Review

The intervertebral discs (IVD) are an essential component of the spine. Degeneration of the discs, commonly due to age or injury, is a leading cause of chronic lower back pain. Despite its high prevalence, there is no effective treatment for disc disease due to limited understanding of disc at the cellular and molecular level.

b Recent Findings

Recent research has demonstrated the importance of the intracellular developmental pathway sonic hedgehog (Shh) during the formation and postnatal maintenance of the IVD. Recent studies corroborate that the down-regulation of SHH expression is associated with pathological changes in the IVDs and demonstrate the reactivation of the hedgehog pathway as a promising avenue for rescuing health disc structure and function.

c Summary

Understanding the role of developmental signaling pathways that regulate disc formation and maintenance may help develop strategies to recapitulate the same mechanism for disc treatment and hence improve the quality and longevity of patient lives.

The feasibility of the CD271+ and CD271- mesenchymal stromal cell enrichment toward nucleus pulposus-like cells

INTRODUCTION

Factors promoting nerve cell ingrowth are considered responsible for chronic back pain resulting from the intervertebral disc degeneration (IDD). One of the recent exploratory IDD treatments is stem cell transplantation therapy. The CD271 (low-affinity nerve growth factor receptor) has been identified as a mark-er of the most homogeneous mesenchymal stem cell (MSC) subset. It is capable of promoting differentiation along adipogenic, osteogenic and chondrogenic lineages and producing significantly higher levels of cytokines as compared to the total population of plastic adherence-mesenchymal stem cells (PA-MSCs). We investigated the ability of CD271+ MSCs to differentiate into chondrocyte-like cells of the nucleus pulposus (NP) of intervertebral disc. We also examined CD271- MSCs, using PA-MSCs as a control cell population.

MATERIAL AND METHODS

Bone marrow derived PA-MSCs and its two subsets, CD271- MSCs and CD271+ MSCs, were seeded in collagen scaffolds. After two weeks of growth in NP-differentiation medium, RNA was isolated from cells-scaffold constructs and was analyzed by q-PCR for expression of NP markers. Glycosaminoglycans were analyzed biochemically directly in cells-scaffold constructs.

RESULTS

Expression of NP markers - extracellular matrix components such as aggrecan, collagen type II and glycosaminoglycans on both RNA and the protein levels - was significantly higher in CD271- MSCs compared to the CD271+ MSCs and PA-MSCs cell populations.

CONCLUSIONS

CD271- MSCs may be superior candidates for NP restorative treatment compared to CD271+ MSCs and PA-MSCs due to their ability of expressing NP-supporting extracellular matrix components at levels higher than the other two studied MSC subsets.

Molecular and genetic advances in the regeneration of the intervertebral disc

Background:

Owing to the debilitating nature of degenerative disc disease (DDD) and other spine pathologies, significant research has been performed with the goal of healing or regenerating the intervertebral disc (IVD). Structural complexity, coupled with low vascularity and cellularity, make IVD regeneration an extremely challenging task.

Methods:

Tissue engineering-based strategies utilize three components to enhance tissue regeneration; scaffold materials to guide cell growth, biomolecules to enhance cell migration and differentiation, and cells (autologous, or allogeneic) to initiate the process of tissue formation. Significant advances in IVD regeneration have been made utilizing these tissue engineering strategies.

Results:

The current literature demonstrates that members of the transforming growth factor beta (TGF-β) superfamily are efficacious in the regeneration of an anabolic response in the IVD and to facilitate chondrogenic differentiation. Gene therapy, though thwarted by safety concerns and the risk of ectopic transfection, has significant potential for a targeted and sustained regenerative response. Stem cells in combination with injectable, biocompatible, and biodegradable scaffolds in the form of hydrogels can differentiate into de novo IVD tissue and facilitate regeneration of the existing matrix. Therapies that address both anabolism and the inherent catabolic state of the IVD using either direct inhibitors or broad-spectrum inhibitors show extensive promise.

Conclusion:

This review article summarizes the genetic and molecular advances that promise to play an integral role in the development of new strategies to combat DDD and promote healing of injured discs.

Regeneration of nucleus pulposus tissue in an ovine intervertebral disc degeneration model by cell-free resorbable polymer scaffolds

Degeneration of intervertebral discs (IVDs) occurs frequently and is often associated with lower back pain. Recent treatment options are limited and treat the symptoms rather than regenerate the degenerated disc. Cell-free, freeze-dried resorbable polyglycolic acid (PGA)-hyaluronan implants were used in an ovine IVD degeneration model. The nucleus pulposus of the IVD was partially removed, endoscopically. PGA-hyaluronan implants were immersed in autologous sheep serum and implanted into the disc defect. Animals with nucleotomy only served as controls. The T2-weighted/fat suppression sequence signal intensity index of the operated discs, as assessed by magnetic resonance imaging (MRI), showed that implantation of the PGA-hyaluronan implant improved (p = 0.0066) the MRI signal compared to controls at 6 months after surgery. Histological analysis by haematoxylin and eosin and safranin O staining showed the ingrowth of cells with typical chondrocytic morphology, even cell distribution, and extracellular matrix rich in proteoglycan. Histomorphometric analyses confirmed that the implantation of the PGA-hyaluronan scaffolds improved (p = 0.027) the formation of regenerated tissue after nucleotomy. Disc heights remained stable in discs with nucleotomy only as well as after implantation of the implant. In conclusion, implantation of cell-free polymer-based implants after nucleotomy induces nucleus pulposus tissue regeneration and improves disc water content in the ovine model.