Insights of stem cell-based endogenous repair of intervertebral disc degeneration

The most influential articles on stem cells in intervertebral disc degeneration

BACKGROUND

Stem cell-related studies have been increasingly conducted to facilitate the regeneration of degenerative discs. However, analyses of high-impact articles focused on this topic are rare. This study aimed to determine and summarize the most-cited studies examining stem cells in the context of intervertebral disc degeneration (IDD).

METHODS

We searched the Web of Science (WoS) database for stem cell-related articles in IDD, and the 50 highest-cited papers were summarized. A correlation analysis was conducted to determine the relationship among WoS citations, Altmetric Attention Score (AAS), and Dimensions.

RESULTS

The number of citations of the top 50 manuscripts ranged from 92 to 370. The top three countries were the United States (14), China (10), and Japan (9). Spine (12) was the most prevalent journal, and this was followed by Biomaterials (6). Bone marrow-derived stem cells were the most common subject (38), and they were followed by nucleus pulposus-derived stem cells (4) and annulus fibrosus-derived stem cells (4). Humans were the most studied species (31), and the next most studied were rabbits (9) and rats (7). There was a very high correlation between WoS and Dimension citations (p < 0.001, r = 0.937).

CONCLUSIONS

For the first time, the highest impact articles examining stem cells in the context of IDD were assessed together. The current study provides a deepened understanding of historical studies focused on stem cells in IDD and is beneficial for future studies in this field.

Decellularized nucleus pulposus matrix/chitosan hybrid hydrogel combined with nucleus pulposus stem cells and GDF5-loaded microspheres for intervertebral disc degeneration prevention

BACKGROUND

Intervertebral disc degeneration (IDD) is considered an important pathological basis for spinal degenerative diseases. Tissue engineering is a powerful therapeutic strategy that can effectively restore the normal biological properties of disc units. In this study, hydrogels loaded with growth/differentiation factor 5 (GDF5) and stem cells were combined to provide an effective strategy for nucleus pulposus regeneration.

METHODS

Nucleus pulposus stem cells (NPSCs) were obtained by low-density inoculation and culture, and their stem cell characteristics were verified by flow cytometry and a tri-lineage-induced differentiation experiment. A decellularized nucleus pulposus matrix (DNPM) and chitosan hybrid hydrogel was prepared, and GDF5-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres were incorporated into the hydrogels to obtain a composite hydrogels with GDF5-loaded microspheres. Taking bone marrow mesenchymal stem cells (BMSCs) as a reference, the effect of composite hydrogels with GDF5-loaded microspheres on the chondrogenic differentiation of NPSCs was evaluated. A model of intervertebral disc degeneration induced by acupuncture on the tail of rats was constructed, and the repair effect of composite hydrogels with GDF5-loaded microspheres combined with NPSCs on IDD was observed.

RESULTS

Stem cell phenotype identification, stemness gene expression and tri-lineage-induced differentiation confirmed that NPSCs had characteristics similar to those of BMSCs. The rat DNPM and chitosan hybrid hydrogels had good mechanical properties, and the GDF5-loaded microspheres sustainably released GDF5. NPSCs grew normally in the composite hydrogels and gradually expressed a chondrocyte phenotype. Animal experiments showed that the composite hydrogels with GDF5-loaded microspheres combined with NPSCs effectively promoted nucleus pulposus regeneration and that the effect of the hydrogels on the repair of IDD was significantly better than that of BMSCs.

CONCLUSION

GDF5-loaded microspheres combined with DNPM/chitosan composite hydrogels can effectively promote the differentiation of NPSCs into nucleus pulposus-like cells and effectively preventIDD.

Regulating pyroptosis by mesenchymal stem cells and extracellular vesicles: A promising strategy to alleviate intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is a main cause of low back pain (LBP), which can lead to disability and thus generate a heavy burden on society. IVDD is characterized by a decrease in nucleus pulposus cells (NPCs) and endogenous mesenchymal stem cells (MSCs), degradation of the extracellular matrix, macrophage infiltration, and blood vessel and nerve ingrowth. To date, the therapeutic approaches regarding IVDD mainly include conservative treatment and surgical intervention. However, both can only relieve symptoms rather than stop or revert the progression of IVDD, since the pathogenesis of IVDD is not yet clear. Pyroptosis, which is characterized by Caspase family dependence and conducted by the Gasdermin family, is a newly discovered mode of programmed cell death. Pyroptosis has been observed in NPCs, annulus fibrosus cells (AFCs), chondrocytes, MSCs, macrophages, vascular endothelial cells and neurons and may contribute to IVDD. MSCs are a kind of pluripotent stem cell that can be found in almost all tissues. MSCs have a strong ability to secrete extracellular vesicles (EVs), which contain exosomes, microvesicles and apoptotic bodies. EVs derived from MSCs play an important role in pyroptosis regulation and could be beneficial for alleviating IVDD. This review focuses on clarifying the regulation of pyroptosis to improve IVDD by MSCs and EVs derived from MSCs.

Discovery of Taurocholic Acid Sodium Hydrate as a Novel Repurposing Drug for Intervertebral Disc Degeneration by Targeting MAPK3

OBJECTIVE

Nowadays, more than 90% of people over 50 years suffer from intervertebral disc degeneration (IDD), but there are exist no ideal drugs. The aim of this study is to identify a new drug for IDD.

METHODS

An approved small molecular drug library including 2040 small molecular compounds was used here. We found that taurocholic acid sodium hydrate (NAT) could induce chondrogenesis and osteogenesis in mesenchymal stem cells (MSCs). Then, an in vivo mouse model of IDD was established and the coccygeal discs transcriptome analysis and surface plasmon resonance analysis (SPR) integrated with liquid chromatography-tandem mass spectrometry assay (LC-MS) were performed in this study to study the therapy effect and target proteins of NAT for IDD. Micro-CT was used to evaluate the cancellous bone. The expression of osteogenic (OCN, RNX2), chondrogenic (COL2A1, SOX9), and the target related (ERK1/2, p-ERK1/2) proteins were detected. The alkaline phosphatase staining was performed to estimate osteogenic differentiation. Blood routine and blood biochemistry indexes were analyzed for the safety of NAT.

RESULTS

The results showed that NAT could induce chondrogenesis and osteogenesis in MSCs. Further experiments confirmed NAT could ameliorate the secondary osteoporosis and delay the development of IDD in mice. Transcriptome analysis identified 128 common genes and eight Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for NAT. SPR-LC-MS assay detected 57 target proteins for NAT, including MAPK3 (mitogen-activated protein kinase 3), also known as ERK1 (extracellular regulated protein kinase 1). Further verification experiment confirmed that NAT significantly reduced the expression of ERK1/2 phosphorylation.

CONCLUSION

NAT would induce chondrogenesis and osteogenesis of MSCs, ameliorate the secondary osteoporosis and delay the progression of IDD in mice by targeting MAPK3.Furthermore, MAPK3, especially the phosphorylation of MAPK3, would be a potential therapeutic target for IDD treatment.

An international analysis of stem cell research in intervertebral disc degeneration

Stem cell therapy has been increasingly investigated as a promising strategy for intervertebral disc degeneration (IDD). However, no international analysis of stem cell research has yet been conducted. This study aimed to analyze the major characteristics of published reports of stem cell use for IDD and to present a global insight into stem cell research. The study period spanned from the inception of the Web of Science database to 2021. A search strategy using specific keywords was implemented to retrieve relevant publications. The numbers of documents, citations, countries, journals, article types, and stem cell types were evaluated. A total of 1170 papers were retrieved. The analysis showed a significant increase in the number of papers over time (p < 0.001). High-income economies accounted for the majority of papers (758, 64.79 %). China produced the most articles (378, 32.31 %), followed by the United States (259, 22.14 %), Switzerland (69, 5.90 %), United Kingdom (54, 4.62 %), and Japan (47, 4.02 %). The United States ranked first in terms of the number of citations (10,346), followed by China (9177) and Japan (3522). Japan ranked first in terms of the number of citations per paper (74.94), followed by United Kingdom (58.54) and Canada (53.74). When standardized by population, Switzerland ranked first, followed by Ireland and Sweden. When gross domestic product was considered, Switzerland ranked first, followed by Portugal and Ireland. The number of papers was positively correlated with gross domestic product (p < 0.001, r = 0.673); however, there was no significant correlation with population (p = 0.062, r = 0.294). Mesenchymal stem cells were the most investigated stem cells, followed by nucleus pulposus-derived stem cells and adipose-derived stem cells. A sharp increase in stem cell research was observed in the field of IDD. China produced the most, although several European countries were more productive relative to their populations and economies.

Engeletin Alleviates the Inflammation and Apoptosis in Intervertebral Disc Degeneration via Inhibiting the NF-κB and MAPK Pathways

Purpose

Low back pain (LBP) induced by intervertebral disc degeneration (IDD) brings progressively painful status and impairs the normal daily living. Engeletin is a plant-derived medicine with anti-inflammation and antioxidant functions. Therefore, we aim to confirm its protective effects against the intervertebral disc degeneration in vivo and in vitro.

Methods

The cytotoxicity of engeletin was validated by CCK-8 tests. Using the TNF-α to simulate the inflammation status in vitro, the expression of inflammatory mediators and MMP families were determined by qPCR, Western blotting and confocal microscopy. Cell apoptosis was analyzed by flow cytometry and TUNEL assay. The expression of apoptosis-related proteins was tested by Western blotting. The activation of NF-κB and MAPK pathways was evaluated by Western blotting and confocal microscopy. In vivo, percutaneous needle puncture was used to establish the IDD model in rat, and engeletin was administrated via intradiscal injection. The therapeutic effects of engeletin were detected through imaging and histology analysis.

Results

Cell viability tests demonstrated there was little cytotoxicity of engeletin toward NP cells. Pretreatment with engeletin effectively ameliorate the TNF-α-induced up-regulation of inflammatory mediators and MMP families, promoting the anabolism of ECM meanwhile. Cell apoptosis was also attenuated with the addition of engeletin. We found that the activation of MAPK and NF-κB signaling pathways and the nuclear translocation of phosphorylated p65 and p38 were inhibited prominently with the treatment of engeletin which may be the potential molecular mechanism for its anti-inflammation effects. Finally, the IDD induced by percutaneous needle puncture was partially alleviated with the injection of engeletin in vivo.

Conclusion

As a natural compound with little cytotoxicity, engeletin possesses the outstanding anti-inflammation and anti-apoptosis effects in the process of IDD in vitro and in vivo, which may be a promising medicine for the prevention and treatment of IDD-related low back pain.

The Thermosensitive Injectable Celecoxib-Loaded Chitosan Hydrogel for Repairing Postoperative Intervertebral Disc Defect

Percutaneous endoscopic lumbar discectomy has been widely used in clinical practice for lumbar spine diseases. But the postoperative disc re-herniation and inflammation are the main reason for pain recurrence after surgery. The postoperative local defect of the intervertebral disc will lead to the instability of the spine, further aggravating the process of intervertebral disc degeneration. In this work, we successfully synthesized the thermosensitive injectable celecoxib-loaded chitosan hydrogel and investigated its material properties, repair effect, biocompatibility, and histocompatibility in in vitro and in vivo study. In vitro and in vivo, the hydrogel has low toxicity, biodegradability, and good biocompatibility. In an animal experiment, this composite hydrogel can effectively fill local tissue defects to maintain the stability of the spine and delay the process of intervertebral disc degeneration after surgery. These results indicated that this composite hydrogel will be a promising way to treat postoperative intervertebral disc disease in future clinical applications.

Intervertebral Disc Degeneration Models for Pathophysiology and Regenerative Therapy -Benefits and Limitations

Aim:This review summarized the recent intervertebral disc degeneration (IDD) models and described their advantages and potential disadvantages, aiming to provide an overview for the current condition of IDD model establishment and new ideas for new strategies development of the treatment and prevention of IDD.Methods:The database of PubMed was searched up to May 2021 with the following search terms: nucleus pulposus, annulus fibrosus, cartilage endplate, intervertebral disc(IVD), intervertebral disc degeneration, animal model, organ culture, bioreactor, inflammatory reaction, mechanical stress, pathophysiology, epidemiology. Any IDD model-related articles were collected and summarized.Results:The best IDD model should have the features of repeatability, measurability and controllability. There are a lot of aspects to be considered in the selection of animals. Mice, rats and rabbits are low-cost and easy to access. However, their IVD size and shape are more different from human anatomy than pigs, cattle, sheep and goats. Organ culture models and animal models are two options in model establishment for IDD. The IVD organ culture model can put the studying variables into the controllable system for transitional research. Unlike the animal model, the organ culture model can only be used to evaluate the short-term effects and it is not applicable in simulating the complex process of IDD. Similarly, the animal models induced by different methods also have their advantages and disadvantages. For studying the mechanism of IDD and the corresponding treatment and prevention strategies, the selection of model should be individualized based on the purpose of each study.Conclusions:Various models have different characteristics and scope of application due to their different rationales and methods of construction. Currently, there is no experimental model that can perfectly mimic the degenerative process of human IVD. Personalized selection of appropriate model based on study purpose and experimental designing can enhance the possibility to obtain reliable and real results.

Acacetin Alleviates Inflammation and Matrix Degradation in Nucleus Pulposus Cells and Ameliorates Intervertebral Disc Degeneration in vivo

Purpose

Intervertebral disc degeneration (IDD) is one of the most prevalent musculoskeletal disorders. The nucleus pulposus is the major component of the intervertebral disc, and nucleus pulposus cells (NPCs) play a significant role in the normal functioning of the intervertebral disc. Reactive oxygen species (ROS) generation, inflammation and extracellular matrix degradation in NPCs contribute to the degeneration of intervertebral discs. Acacetin is a drug that exerts antioxidant and anti-inflammatory effects on many types of cells. However, whether acacetin can relieve the degeneration of NPCs remains unknown.

Methods

NPCs were extracted from rat intervertebral discs. The NPCs were treated with tert-butyl peroxide (TBHP) to simulate a high-ROS environment, and acacetin was subsequently added. The contents of ROS, inflammatory mediators (COX-2, iNOS) and extracellular matrix components (aggrecan, collagen II, MMP13, MMP9, MMP3) were measured. Components of related signaling pathways (Nrf2, MAPK) were also evaluated. To determine the effect of acacetin in vivo, we simulated disc degeneration via needle puncture. Acacetin was then applied intraperitoneally, and the degenerative status was evaluated using MRI and histopathological analysis.

Results

In vitro, acacetin alleviated TBHP-induced ROS generation and upregulated the expression of antioxidant proteins, including HO-1, NQO1, and SOD. In addition, acacetin relieved the TBHP-induced generation of inflammatory mediators (COX-2, iNOS) and degradation of the extracellular matrix (aggrecan, collagen II, MMP13, MMP9, and MMP3). Acacetin exerted its effect by activating the Nrf2 pathway and inhibiting p38, JNK and ERK1/2 phosphorylation. In vivo, acacetin ameliorated puncture-induced disc degeneration in a rat tail model, which was evaluated using MRI and histopathological analysis.

Conclusion

Acacetin alleviated IDD in vitro and in vivo and may have the potential to be developed as an effective treatment for IDD.

MSC-Derived Exosomes Protect Vertebral Endplate Chondrocytes against Apoptosis and Calcification via the miR-31-5p/ATF6 Axis

Apoptosis and calcification of endplate chondrocytes (EPCs) can exacerbate intervertebral disc degeneration (IVDD). Mesenchymal stem cell-derived exosomes (MSC-exosomes) are reported to have the therapeutic potential in IVDD. However, the effects and related mechanisms of MSC-exosomes on EPCs are still unclear. We aimed to investigate the role of MSC-exosomes on EPCs with a tert-butyl hydroperoxide (TBHP)-induced oxidative stress cell model and IVDD rat model. First, our study revealed that TBHP could result in apoptosis and calcification of EPCs, and MSC-exosomes could inhibit the detrimental effects. We also found that these protective effects were inhibited after miroRNA (miR)-31-5p levels were downregulated in MSC-exosomes. The target relationship between miR-31-5p and ATF6 was tested. miR-31-5p negatively regulated ATF6-related endoplasmic reticulum (ER) stress and inhibited apoptosis and calcification in EPCs. Our in vivo experiments indicated that sub-endplate injection of MSC-exosomes can ameliorate IVDD; however, after miR-31-5p levels were downregulated in MSC-exosomes, these protective effects were inhibited. In conclusion, MSC-exosomes reduced apoptosis and calcification in EPCs, and the underlying mechanism may be related to miR-31-5p/ATF6/ER stress pathway regulation.