Quercetin ameliorates oxidative stress-induced senescence in rat nucleus pulposus-derived mesenchymal stem cells via the miR-34a-5p/SIRT1 axis

BACKGROUND Intervertebral disc degeneration(IDD)is a main contributor to low back pain.Oxidative stress,which is highly associated with the progression of IDD,increases senescence of nucleus pulposus-derived mesenchymal stem cells(NPMSCs)and weakens the differentiation ability of NPMSCs in degenerated intervertebral discs(IVDs).Quercetin(Que)has been demonstrated to reduce oxidative stress in diverse degenerative diseases.AIM To investigate the role of Que in oxidative stress-induced NPMSC damage and to elucidate the underlying mechanism.METHODS In vitro,NPMSCs were isolated from rat tails.Senescence-associatedβ-galactosidase(SA-β-Gal)staining,cell cycle,reactive oxygen species(ROS),realtime quantitative polymerase chain reaction(RT-qPCR),immunofluorescence,and western blot analyses were used to evaluated the protective effects of Que.Meanwhile the relationship between miR-34a-5p and Sirtuins 1(SIRT1)was evaluated by dual-luciferase reporter assay.To explore whether Que modulates tert-butyl hydroperoxide(TBHP)-induced senescence of NPMSCs via the miR-34a-5p/SIRT1 pathway,we used adenovirus vectors to overexpress and downregulate the expression of miR-34a-5p and used SIRT1 siRNA to knockdown SIRT1 expression.In vivo,a puncture-induced rat IDD model was constructed,and X rays and histological analysis were used to assess whether Que could alleviate IDD in vivo.RESULTS We found that TBHP can cause NPMSCs senescence changes,such as reduced cell proliferation ability,increased SA-β-Gal activity,cell cycle arrest,the accumulation of ROS,and increased expression of senescence-related proteins.While abovementioned senescence indicators were significantly alleviated by Que treatment.Que decreased the expression levels of senescence-related proteins(p16,p21,and p53)and senescence-associated secreted phenotype(SASP),including IL-1β,IL-6,and MMP-13,and it increased the expression of SIRT1.In addition,the protective effects of Que on cell senescence were partially reversed by miR-34a-5p overexpression and SIRT1 knockdown.In vivo,X-ray,and histological analyses indicated that Que alleviated IDD in a punctureinduced rat model.CONCLUSION In summary,the present study provides evidence that Que reduces oxidative stress-induced senescence of NPMSCs via the miR-34a/SIRT1 signaling pathway,suggesting that Que may be a potential agent for the treatment of IDD.

6-gingerol protects nucleus pulposus-derived mesenchymal stem cells from oxidative injury by activating autophagy

BACKGROUND To date,there has been no effective treatment for intervertebral disc degeneration(IDD).Nucleus pulposus-derived mesenchymal stem cells(NPMSCs)showed encouraging results in IDD treatment,but the overexpression of reactive oxygen species(ROS)impaired the endogenous repair abilities of NPMSCs.6-gingerol(6-GIN)is an antioxidant and anti-inflammatory reagent that might protect NPMSCs from injury.AIM To investigate the effect of 6-GIN on NPMSCs under oxidative conditions and the potential mechanism.METHODS The cholecystokinin-8 assay was used to evaluate the cytotoxicity of hydrogen peroxide and the protective effects of 6-GIN.ROS levels were measured by 2´7´-dichlorofluorescin diacetate analysis.Matrix metalloproteinase(MMP)was detected by the tetraethylbenzimidazolylcarbocyanine iodide assay.TUNEL assay and Annexin V/PI double-staining were used to determine the apoptosis rate.Additionally,autophagy-related proteins(Beclin-1,LC-3,and p62),apoptosisassociated proteins(Bcl-2,Bax,and caspase-3),and PI3K/Akt signaling pathwayrelated proteins(PI3K and Akt)were evaluated by Western blot analysis.Autophagosomes were detected by transmission electron microscopy in NPMSCs.LC-3 was also detected by immunofluorescence.The mRNA expression of collagen II and aggrecan was evaluated by real-time polymerase chain reaction(RT-PCR),and the changes in collagen II and MMP-13 expression were verified through an immunofluorescence assay.RESULTS 6-GIN exhibited protective effects against hydrogen peroxide-induced injury in NPMSCs,decreased hydrogen peroxide-induced intracellular ROS levels,and inhibited cell apoptosis.6-GIN could increase Bcl-2 expression and decrease Bax and caspase-3 expression.The MMP,Annexin V-FITC/PI flow cytometry and TUNEL assay results further confirmed that 6-GIN treatment significantly inhibited NPMSC apoptosis induced by hydrogen peroxide.6-GIN treatment promoted extracellular matrix(ECM)expression by reducing the oxidative stress injury-induced increase in MMP-13 expression.6-GIN activated autophagy by increasing the expression of autophagy-related markers(Beclin-1 and LC-3)and decreasing the expression of p62.Autophagosomes were visualized by transmission electron microscopy.Pretreatment with 3-MA and BAF further confirmed that 6-GIN-mediated stimulation of autophagy did not reduce autophagosome turnover but increased autophagic flux.The PI3K/Akt pathway was also found to be activated by 6-GIN.6-GIN inhibited NPMSC apoptosis and ECM degeneration,in which autophagy and the PI3K/Akt pathway were involved.CONCLUSION 6-GIN efficiently decreases ROS levels,attenuates hydrogen peroxide-induced NPMSCs apoptosis,and protects the ECM from degeneration.6-GIN is a promising candidate for treating IDD.

Urolithin a alleviates oxidative stress-induced senescence in nucleus pulposus-derived mesenchymal stem cells through SIRT1/PGC-1α pathway

BACKGROUND In degenerative intervertebral disc(IVD),an unfavorable IVD environment leads to increased senescence of nucleus pulposus(NP)-derived mesenchymal stem cells(NPMSCs)and the inability to complete the differentiation from NPMSCs to NP cells,leading to further aggravation of IVD degeneration(IDD).Urolithin A(UA)has been proven to have obvious effects in delaying cell senescence and resisting oxidative stress.AIM To explore whether UA can alleviate NPMSCs senescence and to elucidate the underlying mechanism.METHODS In vitro,we harvested NPMSCs from rat tails,and divided NPMSCs into four groups:the control group,H2O2 group,H2O2+UA group,and H2O2+UA+SR-18292 group.Senescence-associatedβ-Galactosidase(SA-β-Gal)activity,cell cycle,cell proliferation ability,and the expression of senescence-related and silent information regulator of transcription 1/PPAR gamma coactivator-1α(SIRT1/PGC-1α)pathway-related proteins and mRNA were used to evaluate the protective effects of UA.In vivo,an animal model of IDD was constructed,and Xrays,magnetic resonance imaging,and histological analysis were used to assess whether UA could alleviate IDD in vivo.RESULTS We found that H2O2 can cause NPMSCs senescence changes,such as cell cycle arrest,reduced cell proliferation ability,increased SA-β-Gal activity,and increased expression of senescence-related proteins and mRNA.After UA pretreatment,the abovementioned senescence indicators were significantly alleviated.To further demonstrate the mechanism of UA,we evaluated the mitochondrial membrane potential and the SIRT1/PGC-1αpathway that regulates mitochondrial function.UA protected mitochondrial function and delayed NPMSCs senescence by activating the SIRT1/PGC-1αpathway.In vivo,we found that UA treatment alleviated an animal model of IDD by assessing the disc height index,Pfirrmann grade and the histological score.CONCLUSION In summary,UA could activate the SIRT1/PGC-1αsignaling pathway to protect mitochondrial function and alleviate cell senescence and IDD in vivo and vitro.

How to enhance the ability of mesenchymal stem cells to alleviate intervertebral disc degeneration

Intervertebral disc(ID)degeneration(IDD)is one of the main causes of chronic low back pain,and degenerative lesions are usually caused by an imbalance between catabolic and anabolic processes in the ID.The environment in which the ID is located is harsh,with almost no vascular distribution within the disc,and the nutrient supply relies mainly on the diffusion of oxygen and nutrients from the blood vessels located under the endplate.The stability of its internal environment also plays an important role in preventing IDD.The main feature of disc degeneration is a decrease in the number of cells.Mesenchymal stem cells have been used in the treatment of disc lesions due to their ability to differentiate into nucleus pulposus cells in a nonspecific anti-inflammatory manner.The main purpose is to promote their regeneration.The current aim of stem cell therapy is to replace the aged and metamorphosed cells in the ID and to increase the content of the extracellular matrix.The treatment of disc degeneration with stem cells has achieved good efficacy,and the current challenge is how to improve this efficacy.Here,we reviewed current treatments for disc degeneration and summarize studies on stem cell vesicles,enhancement of therapeutic effects when stem cells are mixed with related substances,and improvements in the efficacy of stem cell therapy by adjuvants under adverse conditions.We reviewed the new approaches and ideas for stem cell treatment of disc degeneration in order to contribute to the development of new therapeutic approaches to meet current challenges.

Differentiation of Mesenchymal Stem Cells into Nucleus Pulposus Cells In Vitro

To find a new source of seed cells for constructing tissue-engineered intervertebral disc, nucleus pulposus （NP） cells and mesenchymal stem cells （MSCs） were isolated from New Zealand white rabbits. The nucleus pulposus cells population was fluorescence-ladled and co-cultured with MSCs with or without direct contact. Morphological changes were observed every 12 h. Semi-quantitaive reverse transcriptase-polymerase chain reaction was performed to assess the expression levels of Sox-9, aggreacan and type Ⅱ collagen every 24 h after the co-culture. MSCs treated with direct contact rounded up and presented a ring-like appearance. The expression of marker genes was significantly increased when cells were co-cultured with direct contact for 24 h. No significant change was found after coculture without direct contact. Co-culture of NP cells and MSCs with direct contact is a reliable method for generating large amount of NP cells used for cell-based tissue engineering therapy.

Evaluation of CD24 as a marker to rapidly define the mesenchymal stem cell phenotype and its differentiation in human nucleus pulposus

Background Recent studies have indicated that human nucleus pulposus contain mesenchymal stem cells （NP-MSCs）. However, the immunophenotypic variation of NP-MSCs in vitro was unclear. The present study was conducted to address the immunophenotypic variation of mesenchymal stem cells in nucleus pulposus under continuous proliferation in vitro and show the difference between mesenchymal stem cells and nucleus pulposus cell. Methods Tissue samples were obtained from thoracolumbar burst fracture patients and degenerative disc disease patients who underwent discectomy and fusion procedures. Flow cytometric and laser scanning confocal microscope （LSCM） were used to detect the variation of mesenchymal stem cells in nucleus pulposus which were expressing CD105 and CD24 in condition with or without transforming growth factor [31 （TGF-131）. Results More than 90% of the analyzed primary cells of mesenchymal stem cells in nucleus pulposus fulfilled the general immunophenotyping criteria for MSCs, such as CD44, CD105 and CD29, but the marker of mature NP cells characterized as CD24 was negative. In continuous cultures, the proportion of mesenchymal stem cells which were expressing CD44, CD105 and CD29 in nucleus pulposus gradually decreased. The mesenchymal stem cells in nucleus pulposus cells were positive for CD105 and CD29, with slight positivity for CD44. The CD24 expression gradually increased in proliferation. Bi- parametric flow cytometry and laser scanning confocal microscopy confirmed the presence of cells which were expressing CD105 and CD24 independently, and only a small part of cells expressed both CD105 and CD24 simultaneously. TGF-{31 could stimulate mesenchymal stem cells in nucleus pulposus to express CD24. Conclusions Non-degenerative and degenerative NP contains mesechymal stem cells. The variation of CD24 can be used as a marker to identify the NP-MSCs differentiation into NP-like cells.