Mesenchymal stem cell for prevention and management of intervertebral disc degeneration

The regulatory mechanism of cyclic GMP-AMP synthase on inflammatory senescence of nucleus pulposus cell

BACKGROUND

Cellular senescence features irreversible growth arrest and secretion of multiple proinflammatory cytokines. Cyclic GMP-AMP synthase (cGAS) detects DNA damage and activates the DNA-sensing pathway, resulting in the upregulation of inflammatory genes and induction of cellular senescence. This study aimed to investigate the effect of cGAS in regulating senescence of nucleus pulposus (NP) cells under inflammatory microenvironment.

METHODS

The expression of cGAS was evaluated by immunohistochemical staining in rat intervertebral disc (IVD) degeneration model induced by annulus stabbing. NP cells were harvested from rat lumbar IVD and cultured with 10ng/ml IL-1β for 48 h to induce premature senescence. cGAS was silenced by cGAS specific siRNA in NP cells and cultured with IL-1β. Cellular senescence was evaluated by senescence-associated beta-galactosidase (SA-β-gal) staining and flow cytometry. The expression of senescence-associated secretory phenotype including IL-6, IL-8, and TNF-a was evaluated by ELISA and western blotting.

RESULTS

cGAS was detected in rat NP cells in cytoplasm and the expression was significantly increased in degenerated IVD. Culturing in 10ng/ml IL-1β for 48 h induced cellular senescence in NP cells with attenuation of G1-S phase transition. In senescent NP cells the expression of cGAS, p53, p16, NF-kB, IL-6, IL-8, TNF-α was significantly increased while aggrecan and collagen type II was reduced than in normal NP cells. In NP cells with silenced cGAS, the expression of p53, p16, NF-kB, IL-6, IL-8, and TNF-α was reduced in inflammatory culturing with IL-1β.

CONCLUSION

cGAS was increased by NP cells in degenerated IVD promoting cellular senescence and senescent inflammatory phenotypes. Targeting cGAS may alleviate IVD degeneration by reducing NP cell senescence.

Ginsenoside Rg1 inhibits nucleus pulposus cell apoptosis, inflammation and extracellular matrix degradation via the YAP1/TAZ pathway in rats with intervertebral disc degeneration

PURPOSE

Intervertebral disc degeneration (IDD) is one of the main causes of low back pain, which not only affects patients' life quality, but also places a great burden on the public health system. Recently, ginsenoside Rg1 has been found to act in IDD; however, the mechanism is still unclear. The purpose of this study is to explore the function of ginsenoside Rg1 and its molecular mechanism in IDD.

METHODS

The rat model of IDD and nucleus pulposus (NP) experimental groups treated with ginsenoside Rg1 was constructed for investing the role of ginsenoside Rg1 in IDD rats. In the in vitro and in vivo study, the histological morphological changes, motor threshold (MT), inflammatory factors, oxidative stress, apoptosis and expression of the YAP1/TAZ signaling pathway-related proteins of the intervertebral discs (IVD) were measured by histological staining, mechanical and thermal stimulation, ELISA, qRT-PCR, flow cytometry, and western blot, respectively.

RESULTS

Ginsenoside Rg1 significantly increased the threshold for mechanical and thermal stimulation and alleviated histological changes in IDD rats. Ginsenoside Rg1 had a significant inhibitory effect on the secretion level of inflammatory factors, redox activity, extracellular matrix (ECM) degradation in IVD tissue and NP cells, and apoptosis in NP cells. Further investigation revealed that ginsenoside Rg1 significantly inhibited the expression of YAP1/TAZ signaling pathway-related proteins. Additionally, the above inhibitory effect of ginsenoside Rg1 on IDD progression was concentration-dependent, that is, the highest concentration of ginsenoside Rg1 was most effective.

CONCLUSION

Ginsenoside Rg1 inhibits IDD progression by suppressing the activation of YAP1/TAZ signaling pathway. This means that ginsenoside Rg1 has the potential to treat IDD.

Mesenchymal Stem Cells May Alleviate the Intervertebral Disc Degeneration by Reducing the Oxidative Stress in Nucleus Pulposus Cells

Background

Stem cell therapy is a promising therapeutic modality for intervertebral disc degeneration (IDD). Oxidative stress is a vital contributor to the IDD; however, the definite role of oxidative stress in stem cell therapy for IDD remains obscure. The aim of this study was to determine the vital role of oxidative stress-related differentially expressed genes (OSRDEGs) in degenerative NPCs cocultured with mesenchymal stem cells (MSCs).

Methods

A series of bioinformatic methods were used to calculate the oxidative stress score and autophagy score, identify the OSRDEGs, conduct the function enrichment analysis and protein-protein interaction (PPI) analysis, build the relevant competing endogenous RNA (ceRNA) regulatory networks, and explore the potential association between oxidative stress and autophagy in degenerative NPCs cocultured with MSCs.

Results

There was a significantly different oxidative stress score between NPC/MSC samples and NPC samples (p < 0.05). Forty-one OSRDEGs were selected for the function enrichment and PPI analyses. Ten hub OSRDEGs were obtained according to the PPI score, including JUN, CAT, PTGS2, TLR4, FOS, APOE, EDN1, TXNRD1, LRRK2, and KLF2. The ceRNA regulatory network, which contained 17 DElncRNAs, 240 miRNAs, and 10 hub OSRDEGs, was constructed. Moreover, a significant relationship between the oxidative stress score and autophagy score was observed (p < 0.05), and 125 significantly related gene pairs were obtained (|r| > 0.90, p < 0.05).

Conclusion

Stem cell therapy might repair the degenerative IVD via reducing the oxidative stress through the ceRNA regulatory work and restoration of autophagy in degenerative NPCs. This research could provide new insights into the mechanism research of stem cell therapy for IDD and potential therapeutic targets in the IDD treatment.

Transcription regulators differentiate mesenchymal stem cells into chondroprogenitors, and their in vivo implantation regenerated the intervertebral disc degeneration

BACKGROUND

Intervertebral disc degeneration (IVDD) is the leading cause of lower back pain. Disc degeneration is characterized by reduced cellularity and decreased production of extracellular matrix (ECM). Mesenchymal stem cells (MSCs) have been envisioned as a promising treatment for degenerative illnesses. Cell-based therapy using ECM-producing chondrogenic derivatives of MSCs has the potential to restore the functionality of the intervertebral disc (IVD).

AIM

To investigate the potential of chondrogenic transcription factors to promote differentiation of human umbilical cord MSCs into chondrocytes, and to assess their therapeutic potential in IVD regeneration.

METHODS

MSCs were isolated and characterized morphologically and immunologically by the expression of specific markers. MSCs were then transfected with Sox-9 and Six-1 transcription factors to direct differentiation and were assessed for chondrogenic lineage based on the expression of specific markers. These differentiated MSCs were implanted in the rat model of IVDD. The regenerative potential of transplanted cells was investigated using histochemical and molecular analyses of IVDs.

RESULTS

Isolated cells showed fibroblast-like morphology and expressed CD105, CD90, CD73, CD29, and Vimentin but not CD45 antigens. Overexpression of Sox-9 and Six-1 greatly enhanced the gene expression of transforming growth factor beta-1 gene, BMP, Sox-9, Six-1, and Aggrecan, and protein expression of Sox-9 and Six-1. The implanted cells integrated, survived, and homed in the degenerated intervertebral disc. Histological grading showed that the transfected MSCs regenerated the IVD and restored normal architecture.

CONCLUSION

Genetically modified MSCs accelerate cartilage regeneration, providing a unique opportunity and impetus for stem cell-based therapeutic approach for degenerative disc diseases.

Association between polymorphisms of collagen genes and susceptibility to intervertebral disc degeneration: a meta-analysis

Background

Collagens are important structural components of intervertebral disc. A number of studies have been performed for association between polymorphisms of collagen genes and risk of intervertebral disc degeneration (IVDD) but yielded inconsistent results. Here, we performed a meta-analysis to investigate the association of collagen IX alpha 2 (COL9A2) Trp2, collagen IX alpha 3 (COL9A3) Trp3, collagen I alpha 1 (COL1A1) Sp1 and collagen XI alpha 1 (COL11A1) C4603T polymorphisms with susceptibility to IVDD.

Method

Eligible studies were retrieved by searching MEDLINE, EMBASE, Web of Science prior to 31 March, 2021. Odds ratio (OR) and corresponding 95% confidence interval (CI) were calculated for association strength.

Results

A total of 28 eligible studies (31 datasets comprising 5497 cases and 5335 controls) were included. COL9A2 Trp2 carriers had an increased risk of IVDD than non-carriers in overall population (OR = 1.43, 95% CI 0.99–2.06, P = 0.058), which did not reach statistical significance. However, Trp2 carriers had 2.62-fold (95% CI 1.15–6.01, P = 0.022) risk than non-carriers in Caucasians. COL9A3 Trp3 was not associated with IVDD risk (OR = 1.28, 95% CI 0.81–2.02, P = 0.299). T allele and TT genotype of COL1A1 Sp1 (+ 1245G > T) were correlated with increased risk of IVDD. Significant associations were found between COL11A1 C4603T and IVDD risk under allelic (OR = 1.33, 95% CI 1.20–1.48), dominant (OR = 1.45, 95% CI 1.26–1.67), recessive (OR = 1.55, 95% CI 1.21–1.98) and homozygote model (OR = 1.81, 95% CI 1.40–2.34).

Conclusions

COL1A1 Sp1 and COL11A1 C4603T polymorphism are associated with IVDD risk while the predictive roles of collagen IX gene Trp2/3 need verification in more large-scale studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02724-8.

Case Report: Successful Therapy of Spontaneously Occurring Canine Degenerative Lumbosacral Stenosis Using Autologous Adipose Tissue-Derived Mesenchymal Stem Cells

The management of degenerative lumbosacral stenosis (DLSS) in dogs usually requires aggressive, costly surgical treatments that may themselves present complications, while do not fully resolve the symptoms of the disease. In this study, the dog diagnosed with severe DLSS, with hind limb paresis, was treated using a new and least invasive treatment. Cultured autologous adipose tissue-derived mesenchymal stem cells (AT-MSCs) were injected bilaterally at the level of L7-S1, in the vicinity of the external aperture of the intervertebral foramen of DLSS patient. In the previously described treatments of spontaneous intervertebral disc degeneration in dogs, intradiscal injections of MSCs did not lead to positive effects. Here, we report a marked improvement in clinical outcome measures related to the ability of a dog to walk and trot, which were expressed by a numeric rating scale based on a veterinary assessment questionnaire. The improved status persisted throughout the observed time course of 4.5 years after the AT-MSC transplantation. To the best of our knowledge, this is the first case of successful therapy, with long-term positive effect, of spontaneously occurring canine DLSS using presented treatment that, we believe, represents a contribution to current knowledge in this field and may shape both animal and human DLSS treatment options.

ASIC1a activation induces calcium-dependent apoptosis of BMSCs under conditions that mimic the acidic microenvironment of the degenerated intervertebral disc

Purpose: In the degenerated intervertebral disc (IVD), matrix acidity challenges transplanted bone marrow mesenchymal stem cells (BMSCs). The Ca²⁺-permeable acid-sensing ion channel 1a (ASIC1a) is responsible for acidosis-mediated tissue injury. The aim of our study was to confirm whether ASIC1a activation induces BMSC apoptosis under conditions that mimic the acidic microenvironment of the degenerated IVD.

Methods: ASIC1a expression in rat BMSCs was investigated by real time-PCR, Western blot (WB) and immunofluorescence. The proliferation and apoptosis of BMSCs under acidic conditions were analyzed by MTT and TUNEL assays. Ca²⁺-imaging was used to assess the acid-induced increase in the intracellular Ca²⁺ concentration ([Ca²⁺]i). The activation of calpain and calcineurin was analyzed using specific kits, and WB analysis was performed to detect apoptosis-related proteins. Ultrastructural changes in BMSCs were observed using transmission electron microscopy (TEM).

Results: Acid exposure led to the activation of ASIC1a and increased BMSC apoptosis. The Ca²⁺ imaging assay showed a significant increase in the [Ca²⁺]i in response to a solution at pH 6.0. However, BMSC apoptosis and [Ca²⁺]i elevation were alleviated in the presence of an ASIC1a inhibitor. Moreover, ASIC1a mediated the Ca²⁺ influx-induced activation of calpain and calcineurin in BMSCs. WB analysis and TEM revealed mitochondrial apoptosis, which was inhibited by an ASIC1a inhibitor, in BMSCs under acidic conditions.

Conclusions: The mimical acidic microenvironment of the degenerated IVD can induce BMSC apoptosis by activating Ca²⁺-permeable ASIC1a. An acid-induced elevation of [Ca²⁺]i in BMSCs leads to the subsequent activation of calpain and calcineurin, further resulting in increased mitochondrial permeability and mitochondrial-mediated apoptosis.

Efficacy of matrilin-3-primed adipose-derived mesenchymal stem cell spheroids in a rabbit model of disc degeneration

BACKGROUND

Chronic low back pain is a prevalent disability, often caused by intervertebral disc (IVD) degeneration. Mesenchymal stem cell (MSC) therapy could be a safe and feasible option for repairing the degenerated disc. However, for successful translation to the clinic, various challenges need to be overcome including unwanted adverse effects due to acidic pH, hypoxia, and limited nutrition. Matrilin-3 is an essential extracellular matrix (ECM) component during cartilage development and ossification and exerts chondrocyte protective effects.

METHODS

This study evaluated the effects of matrilin-3-primed adipose-derived MSCs (Ad-MSCs) on the repair of the degenerated disc in vitro and in vivo. We determined the optimal priming concentration and duration and developed an optimal protocol for Ad-MSC spheroid generation.

RESULTS

Priming with 10 ng/ml matrilin-3 for 5 days resulted in the highest mRNA expression of type 2 collagen and aggrecan in vitro. Furthermore, Ad-MSC spheroids with a density of 250 cells/microwell showed the increased secretion of favorable growth factors such as transforming growth factor beta (TGF-β1), TGF-β2, interleukin-10 (IL-10), granulocyte colony-stimulating factor (G-CSF), and matrix metalloproteinase 1 (MMP1) and decreased secretion of hypertrophic ECM components. In addition, matrilin-3-primed Ad-MSC spheroid implantation was associated with optimal repair in a rabbit model.

CONCLUSION

Our results suggest that priming MSCs with matrilin-3 and spheroid formation could be an effective strategy to overcome the challenges associated with the use of MSCs for the treatment of IVD degeneration.

Effects of type 1 diabetes mellitus on lumbar disc degeneration: a retrospective study of 118 patients

BACKGROUND

The study aimed to investigate the correlation between type 1 diabetes (T1D) and lumbar disc degeneration (LDD).

METHODS

A retrospective analysis of 118 patients with T1D recruited from January 2014 to March 2019 was performed, and multivariate logistic regression was used to analyse the incidence of T1D; the age, sex, and body mass index (BMI) of the patients; the disease duration and the glycosylated haemoglobin and venous blood glucose levels. All patients who suffered low back pain were assessed by MRI using the Pfirrmann grading system.

RESULTS

A total of 118 patients with an average age of 36.99 ± 17.01 (8-85 years) were reviewed. The mean hospitalization duration, venous glucose fluctuation range, glycated haemoglobin level, highest venous glucose level, venous glucose level, and disease course duration were 13.98 ± 10.16 days, 14.99 ± 5.87 mmol/L, 9.85 ± 2.52 mmol/L, 25.29 ± 7.92 mmol/L, 13.03 ± 5.75 mmol/L and 7.30 ± 8.41 years. The average Pfirrmann scores of the different discs were 2.20 ± 0.62 (L1-2), 2.35 ± 0.67 (L2-3), 2.90 ± 0.45 (L3-4), 4.20 ± 0.52 (L4-5) and 4.10 ± 0.72 (L5-S1). The patients with T1D showed severe disc degeneration. The male sex, glycosylated haemoglobin, venous glucose and venous glucose fluctuations were significantly associated with LDD (P < 0.05).

CONCLUSIONS

Glycosylated haemoglobin, the male, venous glucose and the venous glucose fluctuation range were risk factors for LDD.

Exosomes Derived from Bone Marrow Mesenchymal Stem Cells Prevent Acidic pH-Induced Damage in Human Nucleus Pulposus Cells

Background

The exosomes (Exo) derived from mesenchymal stem cells (MSCs) are capable of attenuating the apoptosis of nucleus pulposus cells (NPCs) elicited by proinflammatory cytokines. However, it remains unknown whether MSC-derived Exo also exert a protective effect on NPCs in the pathological acid environment.

Material/Methods

NPCs were divided into 3 groups: Group A, pH 7.1–7.3; Group B, pH 6.5–6.7 and Group C, pH 5.9–6.1. The NPCs were cultured in the above-defined acidic medium, and 3 different amounts of Exo were added into the media. Finally, the expression of the caspase-3, aggrecan, collagen II, and MMP-13 was analyzed and compared among the different groups.

Results

Compared with cells cultured at pH 7.1–7.3 (Group A), proliferation activity of NPCs cultured at pH 5.9–6.7 (Group B and C) decreased significantly. Collagen II and aggrecan expression was also obviously reduced with the decrease of cell proliferation.

Conversely, the expression of caspase-3 and MMP-13 significantly increased. Further experiments showed that proliferation activity was significantly attenuated in NPCs cultured at pH 5.9–6.1 without Exo treatment (Group E) compared with those cultured at pH 7.1–7.3 without Exo treatment (Group D).

Conclusions

In the pathological acid environment, MSC-derived Exo promotes the expression of chondrocyte extracellular matrix, collagen II, and aggrecan, and reduces matrix degradation by downregulating matrix-degrading enzymes, protecting NPCs from acidic pH-induced apoptosis. This study reveals a promising strategy for treatment of IVD degeneration.

Effect of Lidocaine on Viability and Gene Expression of Human Adipose-derived Mesenchymal Stem Cells: An in vitro Study

OBJECTIVE

To assess the biologic effects of lidocaine on the viability, proliferation, and function of human adipose tissue-derived mesenchymal stromal/stem cells (MSCs) in vitro.

METHODS

Adipose-derived MSCs from three donors were exposed to lidocaine at various dilutions (2 mg/mL to 8 mg/mL) and exposure times (0.5 to 4 hours). Cell number and viability, mitochondrial activity, and real-time reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR) were analyzed at 0 (immediate effects) or 24 and 48 hours (recovery effects) after treatment with lidocaine.

RESULTS

Trypan blue staining showed that increasing concentrations of lidocaine decreased the number of observable viable cells. 3-[4,5,dimethylthiazol-2-yl]-5-[3-carboxymethoxy-phenyl]-2-[4-sulfophenyl]-2H-tetrazolium (MTS) assays revealed a concentration- and time- dependent decline of mitochondrial activity and proliferative ability. Gene expression analysis by RT-qPCR revealed that adipose-derived MSCs exposed to lidocaine express robust levels of stress response/cytoprotective genes. However, higher concentrations of lidocaine caused a significant downregulation of these genes. No significant differences were observed in expression of extracellular matrix (ECM) markers COL1A1 and DCN except for COL3A1 (P < .05). Levels of messenger RNA (mRNA) for proliferation markers (CCNB2, HIST2H4A, P < .001) and MKI67 (P < .001) increased at 24 and 48 hours. Expression levels of several transcription factors- including SP1, PRRX1, and ATF1-were modulated in the same manner. MSC surface markers CD44 and CD105 demonstrated decreased expression immediately after treatment, but at 24 and 48 hours postexposure, the MSC markers showed no significant difference among groups.

CONCLUSION

Lidocaine is toxic to MSCs in a dose- and time- dependent manner. MSC exposure to high (4-8 mg/mL) concentrations of lidocaine for prolonged periods can affect their biologic functions. Although the exposure time in vivo is short, it is essential to choose safe concentrations when applying lidocaine along with MSCs to avoid compromising the viability and potency of the stem cell therapy.

Intervertebral disc tissue engineering: A brief review

Intervertebral disc (IVD) degeneration (IDD) is associated with low back pain and significantly affects the patient's quality of life. Degeneration of the IVD alters disk height and the mechanics of the spine, leading to chronic segmental spinal instability. The pathophysiology of IVD disease is still not well understood. Current therapies for IDD include conservative and invasive approaches, but none of those treatments are able to restore the disc structure and function. Recently, tissue engineering techniques emerged as a possible approach to treat IDD, by replacing a damaged IVD with scaffolds and appropriate cells. Advances in manufacturing techniques, material processing and development, surface functionalization, drug delivery systems and cell incorporation furthered the development of tissue engineering therapies. In this review, biomaterial scaffolds and cell-based therapies for IVD regeneration are briefly discussed.

Dental pulp stem cell-derived chondrogenic cells demonstrate differential cell motility in type I and type II collagen hydrogels

BACKGROUND CONTEXT

Advances in the development of biomaterials and stem cell therapy provide a promising approach to regenerating degenerated discs. The normal nucleus pulposus (NP) cells exhibit similar phenotype to chondrocytes. Because dental pulp stem cells (DPSCs) can be differentiated into chondrogenic cells, the DPSCs and DPSCs-derived chondrogenic cells encapsulated in type I and type II collagen hydrogels can potentially be transplanted into degenerated NP to repair damaged tissue. The motility of transplanted cells is critical because the cells need to migrate away from the hydrogels containing the cells of high density and disperse through the NP tissue after implantation.

PURPOSE

The purpose of this study was to determine the motility of DPSC and DPSC-derived chondrogenic cells in type I and type II collagen hydrogels.

STUDY DESIGN/SETTING

The time lapse imaging that recorded cell migration was analyzed to quantify the cell migration velocity and distance.

METHODS

The cell viability of DPSCs in native or poly(ethylene glycol) ether tetrasuccinimidyl glutarate (4S-StarPEG)-crosslinked type I and type II collagen hydrogels was determined using LIVE/DEAD cell viability assay and AlamarBlue assay. DPSCs were differentiated into chondrogenic cells. The migration of DPSCs and DPSC-derived chondrogenic cells in these hydrogels was recorded using a time lapse imaging system. This study was funded by the Regional Institute on Aging and Wichita Medical Research and Education Foundation, and the authors declare no competing interest.

RESULT

DPSCs showed high cell viability in non-crosslinked and crosslinked collagen hydrogels. DPSCs migrated in collagen hydrogels, and the cell migration speed was not significantly different in either type I collagen or type II collagen hydrogels. The migration speed of DPSC-derived chondrogenic cells was higher in type I collagen hydrogel than in type II collagen hydrogel. Crosslinking of type I collagen with 4S-StarPEG significantly reduced the cell migration speed of DPSC-derived chondrogenic cells.

CONCLUSIONS

After implantation of collagen hydrogels encapsulating DPSCs or DPSC-derived chondrogenic cells, the cells can potentially migrate from the hydrogels and migrate into the NP tissue. This study also explored the differential cell motility of DPSCs and DPSC-derived chondrogenic cells in these collagen hydrogels.

Differentiation of human induced pluripotent stem cells into nucleus pulposus-like cells

Background

Intervertebral disc (IVD) degeneration is characterized by an early decrease in cellularity of the nucleus pulposus (NP) region, and associated extracellular matrix changes, reduced hydration, and progressive degeneration. Cell-based IVD therapy has emerged as an area of great interest, with studies reporting regenerative potential for many cell sources, including autologous or allogeneic chondrocytes, primary IVD cells, and stem cells. Few approaches, however, have clear strategies to promote the NP phenotype, in part due to a limited knowledge of the defined markers and differentiation protocols for this lineage. Here, we developed a new protocol for the efficient differentiation of human induced pluripotent stem cells (hiPSCs) into NP-like cells in vitro. This differentiation strategy derives from our knowledge of the embryonic notochordal lineage of NP cells as well as strategies used to support healthy NP cell phenotypes for primary cells in vitro.

Methods

An NP-genic phenotype of hiPSCs was promoted in undifferentiated hiPSCs using a stepwise, directed differentiation toward mesodermal, and subsequently notochordal, lineages via chemically defined medium and growth factor supplementation. Fluorescent cell imaging was used to test for pluripotency markers in undifferentiated cells. RT-PCR was used to test for potential cell lineages at the early stage of differentiation. Cells were checked for NP differentiation using immunohistochemistry and histological staining at the end of differentiation. To enrich notochordal progenitor cells, hiPSCs were transduced using lentivirus containing reporter constructs for transcription factor brachyury (T) promoter and green fluorescent protein (GFP) fluorescence, and then sorted on T expression based on GFP intensity by flow cytometry.

Results

Periods of pellet culture following initial induction were shown to promote the vacuolated NP cell morphology and NP surface marker expression, including CD24, LMα5, and Basp1. Enrichment of brachyury (T) positive cells using fluorescence-activated cell sorting was shown to further enhance the differentiation efficiency of NP-like cells.

Conclusions

The ability to efficiently differentiate human iPSCs toward NP-like cells may provide insights into the processes of NP cell differentiation and provide a cell source for the development of new therapies for IVD diseases.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0797-1) contains supplementary material, which is available to authorized users.

Mesenchymal Stem Cells Protect Nucleus Pulposus Cells from Compression-Induced Apoptosis by Inhibiting the Mitochondrial Pathway

Objective

Excessive apoptosis of nucleus pulposus cells (NPCs) induced by various stresses, including compression, contributes to the development of intervertebral disc degeneration (IVDD). Mesenchymal stem cells (MSCs) can benefit the regeneration of NPCs and delay IVDD, but the underlying molecular mechanism is poorly understood. This study aimed to evaluate the antiapoptosis effects of bone marrow-derived MSC (BMSC) on rat NPCs exposed to compression and investigate whether the mitochondrial pathway was involved.

Methods

BMSCs and NPCs were cocultured in the compression apparatus at 1.0 MPa for 36 h. Cell viability, apoptosis, mitochondrial function, and the expression of apoptosis-related proteins were evaluated.

Results

The results showed that coculturing with BMSCs increased the cell viability and reduced apoptosis of NPCs exposed to compression. Meanwhile, BMSCs could relieve the compression-induced mitochondrial damage of NPCs by decreasing reactive oxygen species level and maintaining mitochondrial membrane potential as well as mitochondrial integrity. Furthermore, coculturing with BMSCs suppressed the activated caspase-3 and activated caspase-9, decreased the expressions of cytosolic cytochrome c and Bax, and increased the expression of Bcl-2.

Conclusions

Our results suggest that BMSCs can protect against compression-induced apoptosis of NPCs by inhibiting the mitochondrial pathway and thus enhance our understanding on the MSC-based therapy for IVDD.

Cell-based approaches for augmentation of tendon repair

Cell-based approaches are among the principal interventions in orthobiologics to improve tendon and ligament healing and to combat degenerative processes. The number of options available for investigation are expanding rapidly and investigators have an increasing number of cell types to choose from for research purposes. However, in part due to the current regulatory environment, the list of available cells at clinicians' disposal for therapeutic purposes is still rather limited. In this review, we present an overview of the main cellular categories in current use. Notable recent developments in cell-based approaches include the introduction of diverse sources of mesenchymal stem cells, pluripotent cells of extra-embryonic origin, and the emerging popularity of fully differentiated cells such as tenocytes and endothelial cells. Delivery strategies are discussed and a succinct discussion of the current regulatory environment in the United States is presented.

A Histopathological Scheme for the Quantitative Scoring of Intervertebral Disc Degeneration and the Therapeutic Utility of Adult Mesenchymal Stem Cells for Intervertebral Disc Regeneration

The purpose of this study was to develop a quantitative histopathological scoring scheme to evaluate disc degeneration and regeneration using an ovine annular lesion model of experimental disc degeneration. Toluidine blue and Haematoxylin and Eosin (H&E) staining were used to evaluate cellular morphology: (i) disc structure/lesion morphology; (ii) proteoglycan depletion; (iii) cellular morphology; (iv) blood vessel in-growth; (v) cell influx into lesion; and (vi) cystic degeneration/chondroid metaplasia. Three study groups were examined: 5 × 5 mm lesion; 6 × 20 mm lesion; and 6 × 20 mm lesion plus mesenchymal stem cell (MSC) treatment. Lumbar intervertebral discs (IVDs) were scored under categories (i-vi) to provide a cumulative score, which underwent statistical analysis using STATA software. Focal proteoglycan depletion was associated with 5 × 5 mm annular rim lesions, bifurcations, annular delamellation, concentric and radial annular tears and an early influx of blood vessels and cells around remodeling lesions but the inner lesion did not heal. Similar features in 6 × 20 mm lesions occurred over a 3-6-month post operative period. MSCs induced a strong recovery in discal pathology with a reduction in cumulative histopathology degeneracy score from 15.2 to 2.7 (p = 0.001) over a three-month recovery period but no recovery in carrier injected discs.

What is the clinical evidence on regenerative medicine in intervertebral disc degeneration?

PURPOSE

This review aims to explore and summarize the current clinical evidence about the use of regenerative medicine such as mesenchymal stem cells or platelet-rich plasma in intervertebral disc regeneration, in order to clarify the state of art of these novel approaches.

MATERIALS AND METHODS

We performed a research of the available literature about regenerative medicine strategies aiming to prevent intervertebral disc degeneration. All preclinical trials and in vitro studies were excluded. Only clinical trials were critically analysed.

RESULTS

The manuscript selection produced a total of 7 articles concerning the use of regenerative therapies in intervertebral disc degeneration, covering the period between 2010 and 2016. Articles selected were 4 about the injection of mesenchymal stem cells-related results and 3 using platelet-rich plasma. The total population of patients treated with regenerative medicine strategies were 104 patients.

CONCLUSIONS

Regenerative medicine, such as the use of mesenchymal stem cells or platelet-rich plasma, in intradiscal disc degeneration has shown preclinical and clinical positive results. Randomized clinical trials studying the potential of MSCs intradiscal injection have not been conducted, and PRP effect has been studied only preliminarily. Additional more powered high-quality studies are needed to really appreciate the long-term safety and efficacy of regenerative medicine approaches in IDD.

Isolation and identification of stem cells from degenerated human intervertebral discs and their migration characteristics

Mesenchymal stem cells (MSCs) have been isolated and identified separately from the three components of intervertebral disc, i.e. annulus fibrosus (AF), nucleus pulposus (NP), and cartilage endplate (CEP). However, few studies have been carried out to compare the properties of these three kinds of stem cells, especially their migration ability which is essential for their potential clinical application. In this study, MSCs were isolated from AF, NP, and CEP, respectively, of human degenerated discs and identified by surface markers and multilineage differentiation assay at passage 3. These three types of stem cells were named as AF-MSCs, NP-MSCs, and CEP-MSCs. Then, their biological characteristics were compared in terms of proliferation, passage, colony formation, migration, and invasion capacity. Results showed that all the three types of cells were identified as MSCs and had similar characteristics in proliferation, passage, and colony formation capacity. CEP-MSCs showed the highest migration and invasion potency, while NP-MSCs showed the lowest migration ability and almost no invasion potency, suggesting that CEP-MSCs had the most powerful properties of migration and invasion when compared with AF-MSCs and NP-MSCs. It was also found that the expression of CXCR4 was higher in CEP-MSCs than in the other two, suggesting that SDF-1/CXCR4 axis may play significant roles in the migration of these cells.

Multipotent Mesenchymal Stem Cell Treatment for Discogenic Low Back Pain and Disc Degeneration

Low back pain with resultant loss of function, decreased productivity, and high economic costs is burdensome for both the individual and the society. Evidence suggests that intervertebral disc pathology is a major contributor to spine-related pain and degeneration. When commonly used conservative therapies fail, traditional percutaneous or surgical options may be beneficial for pain relief but are suboptimal because of their inability to alter disc microenvironment catabolism, restore disc tissue, and/or preserve native spine biomechanics. Percutaneously injected Multipotent Mesenchymal Stem Cell (MSC) therapy has recently gained clinical interest for its potential to revolutionarily treat disc-generated (discogenic) pain and associated disc degeneration. Unlike previous therapies to date, MSCs may uniquely offer the ability to improve discogenic pain and provide more sustained improvement by reducing disc microenvironment catabolism and regenerating disc tissue. Consistent treatment success has the potential to create a paradigm shift with regards to the treatment of discogenic pain and disc degeneration.

Management of cervical fractures in ankylosing spondylitis: anterior, posterior or combined approach?

INTRODUCTION

Ankylosing spondylitis (AS) can lead to an increased risk of cervical fractures.

SOURCES OF DATA

A systematic review was undertaken using the keywords 'ankylosing spondylitis', 'spine fractures', 'cervical fractures', 'surgery' and 'postoperative outcomes' on Medline, Pubmed, Google Scholar, Ovid and Embase, and the quality of the studies included was evaluated according to the Coleman Methodology Score.

AREAS OF AGREEMENT

Surgery ameliorates neurological function in patients with unstable AS-related cervical fractures. The combined anterior/posterior and the posterior approaches are more effective than the anterior approach.

AREAS OF CONTROVERSY

The optimal approach, anterior, posterior or combined anterior/posterior, for the management of AS related cervical fractures has not been defined.

GROWING POINTS

Open reduction and internal fixation allows avoiding worsening and enhances neurological function in AS patients with cervical fractures.

AREAS TIMELY FOR DEVELOPING RESEARCH

Adequately powered randomized trials with appropriate subjective and objective outcome measures are necessary to reach definitive conclusions.

The presence of stem cells in potential stem cell niches of the intervertebral disc region: an in vitro study on rats

PURPOSE

The potential of stem cell niches (SCNs) in the intervertebral disc (IVD) region, which may be of great significance in the regeneration process, was recently proposed. To the best of our knowledge, no previous in vitro study has examined the characteristics of stem cells derived from the potential SCN of IVD (ISN). Therefore, increasing knowledge on ISN-derived stem cells (ISN-SCs) may provide a greater understanding of IVD degeneration and regeneration processes. We aimed to demonstrate the existence of ISN-SCs and to compare their characteristics with bone marrow mesenchymal stem cells (BMSCs) in vitro.

METHODS

Sprague-Dawley rats (male, 10-week-old) were used in this study. ISN tissues were separated by ophthalmic surgical instruments under a dissecting microscope according to the anatomical areas. BMSCs and cells isolated from the ISN tissues were cultured and expanded in vitro. Passage 4 populations were used for further analysis with respect to colony-forming ability, cellular immunophenotype, cell cycle, stem cell-related gene expression, and proliferation and multipotential differentiation capacities.

RESULTS

In general, both of ISN-SCs and mesenchymal stromal cells (MSCs) met the minimal criteria for the definition of multipotent mesenchymal stromal cells, including adherence to plastic, specific surface antigen expression, and multipotent differentiation potential. Especially, ISN-SCs even showed greater potential of osteogenesis and chondrogenesis. The ISN-SCs also expressed stem cell-related genes that were comparable to those of BMSCs, and had colony-forming and self-renewal abilities.

CONCLUSIONS

To the best of our knowledge, this is the first in vitro study aimed towards determining the existence and characteristics of ISN-SCs, which belong to the MSC family and with greater osteogenic and chondrogenic abilities than BMSCs according to our data. This finding may be of great significance for additional studies that investigate the migration of ISN-SCs into the IVD, and may provide a new perspective on different biological approaches for IVD self-regeneration.

Molecular basis of intervertebral disc degeneration and herniations: what are the important translational questions?

BACKGROUND

Intervertebral disc degeneration is a common condition with few inexpensive and effective modes of treatment, but current investigations seek to clarify the underlying process and offer new treatment options. It will be important for physicians to understand the molecular basis for the pathology and how it translates to developing clinical treatments for disc degeneration. In this review, we sought to summarize for clinicians what is known about the molecular processes that causes disc degeneration.

RESULTS

A healthy disc requires maintenance of a homeostatic environment, and when disrupted, a catabolic cascade of events occurs on a molecular level resulting in upregulation of proinflammatory cytokines, increased degradative enzymes, and a loss of matrix proteins. This promotes degenerative changes and occasional neurovascular ingrowth potentially contributing to the development of pain. Research demonstrates the molecular changes underlying the harmful effects of aging, smoking, and obesity seen clinically while demonstrating the variable influence of exercise. Finally, oral medications, supplements, biologic treatments, gene therapy, and stem cells hold great promise but require cautious application until their safety profiles are better outlined.

CONCLUSIONS

Intervertebral disc degeneration occurs where there is a loss of homeostatic balance with a predominantly catabolic metabolic profile. A basic understanding of the molecular changes occurring in the degenerating disc is important for practicing clinicians because it may help them to inform patients to alter lifestyle choices, identify beneficial or harmful supplements, or offer new biologic, genetic, or stem cell therapies.

Evaluation of intervertebral disc regeneration with implantation of bone marrow mesenchymal stem cells (BMSCs) using quantitative T2 mapping: a study in rabbits

PURPOSE

The aim of the study was to investigate the curative effects of transplantation of bone marrow mesenchymal stem cells (BMSCs) on intervertebral disc regeneration and to investigate the feasibility of the quantitative T2 mapping method for evaluating repair of the nucleus pulposus after implantation of BMSCs.

METHODS

Forty-eight New Zealand white rabbits were used to establish the lumber disc degenerative model by stabbing the annulus fibrosus and then randomly divided into four groups, i.e. two weeks afterwards, BMSCs or phosphate-buffered saline (PBS) were transplanted into degenerative discs (BMSCs group and PBS group), while the operated rabbits without implantation of BMSCs or PBS served as the sham group and the rabbits without operation were used as the control group. At weeks two, six and ten after operation, the T2 values and disc height indices (DHI) were calculated by magnetic resonance imaging (MRI 3.0 T), and the gene expressions of type II collagen (COL2) and aggrecan (ACAN) in degenerative discs were evaluated by real-time reverse transcription polymerase chain reaction (RT-PCR). T2 values for the nucleus pulposus were correlated with ACAN or COL2 expression by regression analysis.

RESULTS

Cell clusters, disorganised fibres, interlamellar glycosaminoglycan (GAG) matrix and vascularisation were observed in lumber degenerative discs. BMSCs could be found to survive in intervertebral discs and differentiate into nucleus pulposus-like cells expressing COL2 and ACAN. The gene expression of COL2 and ACAN increased during ten weeks after transplantation as well as the T2 signal intensity and T2 value. The DHI in the BMSCs group decreased more slowly than that in PBS and sham groups. The T2 value correlated significantly with the gene expression of ACAN and COL2 in the nucleus pulposus.

CONCLUSIONS

Transplantation of BMSCs was able to promote the regeneration of degenerative discs. Quantitative and non-invasive T2 mapping could be used to evaluate the regeneration of the nucleus pulposus with good sensitivity.

Delivering mesenchymal stem cells in collagen microsphere carriers to rabbit degenerative disc: reduced risk of osteophyte formation

Mesenchymal stem cells (MSCs) have the potential to treat early intervertebral disc (IVD) degeneration. However, during intradiscal injection, the vast majority of cells leaked out even in the presence of hydrogel carrier. Recent evidence suggests that annulus puncture is associated with cell leakage and contributes to osteophyte formation, an undesirable side effect. This suggests the significance of developing appropriate carriers for intradiscal delivery of MSCs. We previously developed a collagen microencapsulation platform, which entraps MSCs in a solid microsphere consisting of collagen nanofiber meshwork. These solid yet porous microspheres support MSC attachment, survival, proliferation, migration, differentiation, and matrix remodeling. Here we hypothesize that intradiscal injection of MSCs in collagen microspheres will outperform that of MSCs in saline in terms of better functional outcomes and reduced side effects. Specifically, we induced disc degeneration in rabbits and then intradiscally injected autologous MSCs, either packaged within collagen microspheres or directly suspended in saline, into different disc levels. Functional outcomes including hydration index and disc height were monitored regularly until 6 months. Upon sacrifice, the involved discs were harvested for histological, biochemical, and biomechanical evaluations. MSCs in collagen microspheres showed advantage over MSCs in saline in better maintaining the dynamic mechanical behavior but similar performance in hydration and disc height maintenance and matrix composition. More importantly, upon examination of gross appearance, radiograph, and histology of IVD, delivering MSCs in collagen microspheres significantly reduced the risk of osteophyte formation as compared to that in saline. This work demonstrates the significance of using cell carriers during intradiscal injection of MSCs in treating disc degeneration.

Differentiation of mouse induced pluripotent stem cells (iPSCs) into nucleus pulposus-like cells in vitro

A large percentage of the population may be expected to experience painful symptoms or disability associated with intervertebral disc (IVD) degeneration - a condition characterized by diminished integrity of tissue components. Great interest exists in the use of autologous or allogeneic cells delivered to the degenerated IVD to promote matrix regeneration. Induced pluripotent stem cells (iPSCs), derived from a patient's own somatic cells, have demonstrated their capacity to differentiate into various cell types although their potential to differentiate into an IVD cell has not yet been demonstrated. The overall objective of this study was to assess the possibility of generating iPSC-derived nucleus pulposus (NP) cells in a mouse model, a cell population that is entirely derived from notochord. This study employed magnetic activated cell sorting (MACS) to isolate a CD24(+) iPSC subpopulation. Notochordal cell-related gene expression was analyzed in this CD24(+) cell fraction via real time RT-PCR. CD24(+) iPSCs were then cultured in a laminin-rich culture system for up to 28 days, and the mouse NP phenotype was assessed by immunostaining. This study also focused on producing a more conducive environment for NP differentiation of mouse iPSCs with addition of low oxygen tension and notochordal cell conditioned medium (NCCM) to the culture platform. iPSCs were evaluated for an ability to adopt an NP-like phenotype through a combination of immunostaining and biochemical assays. Results demonstrated that a CD24(+) fraction of mouse iPSCs could be retrieved and differentiated into a population that could synthesize matrix components similar to that in native NP. Likewise, the addition of a hypoxic environment and NCCM induced a similar phenotypic result. In conclusion, this study suggests that mouse iPSCs have the potential to differentiate into NP-like cells and suggests the possibility that they may be used as a novel cell source for cellular therapy in the IVD.

Growth factors and stem cells for the management of anterior cruciate ligament tears

The anterior cruciate ligament (ACL) is fundamental for the knee joint stability. ACL tears are frequent, especially during sport activities, occurring mainly in young and active patients. Nowadays, the gold standard for the management of ACL tears remains the surgical reconstruction with autografts or allografts. New strategies are being developed to resolve the problems of ligament grafting and promote a physiological healing process of ligamentous tissue without requiring surgical reconstruction. Moreover, these strategies can be applicable in association surgical reconstruction and may be useful to promote and accelerate the healing process. The use of growth factors and stem cells seems to offer a new and fascinating solution for the management of ACL tears. The injection of stem cell and/or growth factors in the site of ligamentous injury can potentially enhance the repair process of the physiological tissue. These procedures are still at their infancy, and more in vivo and in vitro studies are required to clarify the molecular pathways and effectiveness of growth factors and stem cells therapy for the management of ACL tears. This review aims to summarize the current knowledge in the field of growth factors and stem cells for the management of ACL tears.