Nucleus Pulposus Cells from Calcified Discs Promote the Degradation of the Extracellular Matrix through Upregulation of the GATA3 Expression

Objective Disc calcification is strongly associated with disc degeneration;however,the underlying mechanisms driving its pathogenesis are poorly understood.This study aimed to provide a gene expression profile of nucleus pulposus cells(NPCs)from calcified discs,and clarify the potential mechanism in disc degeneration.Methods Primary NPCs were isolated from calcified and control discs(CAL-NPC and CON-NPC),respectively.The proliferation and extracellular matrix(ECM)metabolism capacities of the cells were evaluated using MTT and Western blotting,respectively.RNA sequencing was used to identify differentially expressed genes(DEGs)in the CAL-NPCs.The biological functions of the DEGs were analyzed using the Gene Ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)databases.The transcription factor database and Cytoscape software were used to construct the transcription factor-DEGs regulatory network.The role of the verified transcription factor in NPC proliferation and ECM metabolism was also investigated.Results The CAL-NPCs exhibited a lower proliferation rate and higher ECM degradation capacity than the CON-NPCs.In total,375 DEGs were identified in the CAL-NPCs.The GO and KEGG analyses showed that the DEGs were primarily involved in the regulation of ribonuclease activity and NF-kappa B and p53 signaling pathways.GATA-binding protein 3(GATA3)with the highest verified levels was selected for further studies.Overexpression of GATA3 in the CON-NPCs significantly inhibited their proliferation and promoted their ECM degradation function,while the knockdown of GATA3 in the CAL-NPCs resulted in the opposite phenotypes.Conclusion This study provided a comprehensive gene expression profile of the NPCs from the calcified discs and supported that GATA3 could be a potential target for reversing calcification-associated disc degeneration.

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.

Normal and Degenerated Rabbit Nucleus Pulposus Cells in in vitro Cultures: A Biological Comparison

This study examined the biological characteristics of normal and degenerated rabbit nucleus pulposus （NP） cells in vitro in order to provide seed cells for intervertebral disc （IVD） tissue engineering. A total of 8 adult New Zealand white rabbits underwent annulus puncture to establish models ofintervertebral disc degeneration （IDD）. Four weeks later, normal and degenerated NP cells were obtained. Cell morphology was observed by light and electron microscopy. Cell viability was measured by MTT assay. Cell cycle and expression of extracellular matrix （ECM）-related genes （aggrecan and type II col- lagen） were determined by using flow cytometry and RT-PCR respectively. The growth curve of normal NP cells showed that the cells at passage 4 tended to slowly grow on the fifth day of culture. The density of normal NP cells at passages 5 to 7 was significantly less than that of the first-passage cells 2 or 3 days after seeding （P〈0.05）. The degenerated NP cells at passage 3 showed slow growth at 4th day. After 5 passages, the degenerated NP cells assumed stagnant growth and the growth seemed to stop at passage 7. The MTT assay revealed that for both normal and degenerated NP cells, the absorbance （.4） value at passages 4-7 was obviously decreased as compared with that at passage 1 （P〈0.05）. Cell cycle analysis showed that the proportion of normal NP cells at G1 phase was 65.4%-3.5%, significantly lower than that of degenerated NP cells at the same cell cycle phase With the value being 77.6%-4.8%. The degen- erated NP cells were predominantly arrested at Gt phase and failed to enter S phase. The expression of type II collagen and aggrecan was significantly decreased with passaging. It was concluded that normal NP cells possessed good viability and proliferative capacity by the third passage, and they could secrete large amounts of ECM within this period. The normal NP cells may serve as seed cells for IVD tissue engineering.

Transplantation of gene-modified nucleus pulposus cells reverses rabbit intervertebral disc degeneration

Background Intervertebral disc degeneration is the main cause of low back pain. The purpose of this study was to explore potential methods for reversing the degeneration of lumbar intervertebral discs by transplantation of gene-modified nucleus pulposus cells into rabbit degenerative lumbar intervertebral discs after transfecting rabbit nucleus pulposus cells with adeno-associated virus 2 （AAV2）-mediated connective tissue growth factor （CTGF） and tissue inhibitor of metalloproteinases 1 （TIMP1） genes in vitro. Methods Computer tomography （CT）-guided percutaneous annulus fibrosus injury was performed to build degenerative lumbar intervertebral disc models in 60 New Zealand white rabbits, rAAV2-CTGF-IRES-TIMPI-transfected rabbit nucleus pulposus cells were transplanted into degenerative lumbar intervertebral discs （transplantation group）, phosphate-buffered saline （PBS） was injected into degenerative lumbar intervertebral discs （degeneration control group） and normal lumbar intervertebral discs served as a blank control group. After 6, 10 and 14 weeks, the disc height index （DHI） and signal intensity in intervertebral discs were observed by X-ray and magnetic resonance imaging （MRI） analysis The expression of CTGF and TIMP1 in nucleus pulposus tissue was determined by Western blotting analysis, the synthesis efficiency of proteoglycan was determined by a 35S-sulfate incorporation assay, and the mRNA expression of type II collagen and proteoglycan was detected by RT-PCR. Results MRI confirmed that degenerative intervertebral discs appeared two weeks after percutaneous puncture. Transgenic nucleus pulposus cell transplantation could retard the rapid deterioration of the DHI. MRI indicated that degenerative intervertebral discs were relieved in the transplantation group compared with the degeneration control group. The expression of collagen II mRNA and proteoglycan mRNA was significantly higher in the transplantation group and the blank control group compared with the degeneration control group （P 〈0.05）. Conclusions CT-guided percutaneous puncture can successfully build rabbit degenerative intervertebral disc models. Both CTGF and TIMPl-transfected cell transplantation helps to maintain disc height, and promotes the biosynthesis of tvDe II collaQen and proteoalvcan in intervertebral discs, reversinq the de（：ieneration of intervertebral discs.

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.

An esterase-responsive ibuprofen nano-micelle pre-modified embryo derived nucleus pulposus progenitor cells promote the regeneration of intervertebral disc degeneration

Stem cell-based transplantation is a promising therapeutic approach for intervertebral disc degeneration(IDD).Current limitations of stem cells include with their insufficient cell source,poor proliferation capacity,low nucleus pulposus(NP)-specific differentiation potential,and inability to avoid pyroptosis caused by the acidic IDD microenvironment after transplantation.To address these challenges,embryo-derived long-term expandable nucleus pulposus progenitor cells(NPPCs)and esterase-responsive ibuprofen nano-micelles(PEG-PIB)were prepared for synergistic transplantation.In this study,we propose a biomaterial pre-modification cell strategy;the PEG-PIB were endocytosed to pre-modify the NPPCs with adaptability in harsh IDD microenvironment through inhibiting pyroptosis.The results indicated that the PEG-PIB pre-modified NPPCs exhibited inhibition of pyroptosis in vitro;their further synergistic transplantation yielded effective functional recovery,histological regeneration,and inhibition of pyroptosis during IDD regeneration.Herein,we offer a novel biomaterial pre-modification cell strategy for synergistic transplantation with promising therapeutic effects in IDD regeneration.

Specific Inhibitory Protein Dkk-1 Blocking Wnt/β-catenin Signaling Pathway Improve Protectives Effect on the Extracellular Matrix

The present study examined the role of Wnt/β-catenin signaling pathway in the degeneration of nucleus pulposus cells and the protective effect of DKK1 on nucleus pulposus cells. The model of nucleus pulposus cell degeneration was induced by intra-disc injection of TNF-α, and the expression of β-catenin protein was detected by Western blotting. The cultured rabbit nucleus pulposus cells were divided into 4 groups. In group A, the cells were cultured with normal medium and served as control group. In group B, the cells were cultured with TNF-α and acted as degeneration group. In group C, the cells were cultured with TNF-α and transfected with Adv-eGFP and was used as fluorescence control group. In group D, the cells were cultured with TNF-α and transfected with Adv-hDKK1-eGFP, serving as intervention group. The expression of typeⅡcollagen, proteoglycan, β-catenin, and MMP-13 in each group was detected by immunocytochemistry and RT-PCR. The result showed that TNF-α increased the expression of β-catenin and MMP-13, and significantly inhibited the synthesis of type Ⅱ collagen and proteoglycan, which resulted in the degeneration of nucleus pulposus cells. This effect could be obviously reversed by DKK1. We are led to concluded that TNF-α could activate the Wnt/β-catenin signaling pathway, and increase the expression of MMP-13, thereby resulting in disc degeneration. Specifically blocking Wnt/β-catenin signaling pathway by DKK-1 could protect the normal metabolism of intervertebral disc tissue. The Wnt pathway plays an important role in the progression of the intervertebral disc degeneration.