CircGLCE alleviates intervertebral disc degeneration by regulating apoptosis and matrix degradation through the targeting of miR-587/STAP1

Silencing circATXN1 in Aging Nucleus Pulposus Cell Alleviates Intervertebral Disc Degeneration via Correcting Progerin Mislocalization

Circular RNAs (circRNAs) play a critical regulatory role in degenerative diseases; however, their functions and therapeutic applications in intervertebral disc degeneration (IVDD) have not been explored. Here, we identified that a novel circATXN1 highly accumulates in aging nucleus pulposus cells (NPCs) accountable for IVDD. CircATXN1 accelerates cellular senescence, disrupts extracellular matrix organization, and inhibits mitochondrial respiration. Mechanistically, circATXN1, regulated by heterogeneous nuclear ribonucleoprotein A2B1-mediated splicing circularization, promotes progerin translocation from the cell nucleus to the cytoplasm and inhibits the expression of insulin-like growth factor 1 receptor (IGF-1R). To demonstrate the therapeutic potential of circATXN1, siRNA targeting the backsplice junction of circATNX1 was screened and delivered by tetrahedral framework nucleic acids (tFNAs) due to their unique compositional and tetrahedral structural features. Our siRNA delivery system demonstrates superior abilities to transfect aging cells, clear intracellular ROS, and enhanced biological safety. Using siRNA-tFNAs to silence circATXN1, aging NPCs exhibit reduced mislocalization of progerin in the cytoplasm and up-regulation of IGF-1R, thereby demonstrating a rejuvenated cellular phenotype and improved mitochondrial function. In vivo, administering an aging cell-adapted siRNA nucleic acid framework delivery system to progerin pathologically expressed premature aging mice (zmpste24-/-) can ameliorate the cellular matrix in the nucleus pulposus tissue, effectively delaying IVDD. This study not only identified circATXN1 functioning as a cell senescence promoter in IVDD for the first time, but also successfully demonstrated its therapeutic potential via a tFNA-based siRNA delivery strategy.

Circular RNA and intervertebral disc degeneration: unravelling mechanisms and implications

Low back pain (LBP) is a major public health problem worldwide and a significant health and economic burden. Intervertebral disc degeneration (IDD) is the reason for LBP. However, we have not identified effective therapeutic strategies to address this challenge. With accumulating knowledge on the role of circular RNAs in the pathogenesis of IDD, we realised that circular RNAs (circRNAs) may have tremendous therapeutic potential and clinical application prospects in this field. This review presents an overview of the current understanding of characteristics, classification, biogenesis, and function of circRNAs and summarises the protective and detrimental circRNAs involved in the intervertebral disc that have been studied thus far. This review is aimed to help researchers better understand the regulatory role of circRNAs in the progression of IDD, reveal their clinical therapeutic potential, and provide a theoretical basis for the prevention and targeted treatment of IDD.

Molecular mechanism and therapeutic potential of HDAC9 in intervertebral disc degeneration

BACKGROUND

Intervertebral disc degeneration (IVDD) is the major cause of low-back pain. Histone deacetylase 9 (HDAC9) was dramatically decreased in the degenerative nucleus pulposus (NP) samples of patients with intervertebral disc degeneration (IVDD) according to bioinformatics analysis of Gene Expression Omnibus (GEO) GSE56081 dataset. This study aims to investigate the role of HDAC9 in IVDD progression.

METHODS

The contribution of HDAC9 to the progression of IVDD was assessed using HDAC9 knockout (HDAC9KO) mice and NP-targeted HDAC9-overexpressing mice by IVD injection of adenovirus-mediated HDAC9 under a Col2a1 promoter. Magnetic resonance imaging (MRI) and histological analysis were used to examine the degeneration of IVD. NP cells were isolated from mice to investigate the effects of HDAC9 on apoptosis and viability. mRNA-seq and coimmunoprecipitation/mass spectrometry (co-IP/MS) analysis were used to analyze the HDAC9-regulated factors in the primary cultured NP cells.

RESULTS

HDAC9 was statistically decreased in the NP tissues in aged mice. HDAC9KO mice spontaneously developed age-related IVDD compared with wild-type (HDAC9WT) mice. In addition, overexpression of HDAC9 in NP cells alleviated IVDD symptoms in a surgically-induced IVDD mouse model. In an in vitro assay, knockdown of HDAC9 inhibited cell viability and promoted cell apoptosis of NP cells, and HDAC9 overexpression had the opposite effects in NP cells isolated from HDAC9KO mice. Results of mRNA-seq and co-IP/MS analysis revealed the possible proteins and signaling pathways regulated by HDAC9 in NP cells. RUNX family transcription factor 3 (RUNX3) was screened out for further study, and RUNX3 was found to be deacetylated and stabilized by HDAC9. Knockdown of RUNX3 restored the effects of HDAC9 silencing on NP cells by inhibiting apoptosis and increasing viability.

CONCLUSION

Our results suggest that HDAC9 plays an important role in the development and progression of IVDD. It might be required to protect NP cells against the loss of cell viability and apoptosis by inhibiting RUNX3 acetylation and expression during IVDD. Together, our findings suggest that HDAC9 may be a potential therapeutic target in IVDD.

The pathological mechanisms of circRNAs in mediating intervertebral disc degeneration

Lower back pain (LBP) is a worldwide health problem associated with significant economic and social burden. Intervertebral disc degeneration (IVDD) is a leading cause of LBP. Several studies show that the death of nucleus pulposus cells (NPCs), abnormal metabolism of the extracellular matrix (ECM), and inflammatory response are the key mechanisms behind the pathogenesis of IVDD. Circular RNAs (circRNAs) are key regulators of gene expression and play a significant role in regulating NPCs death, ECM homeostasis, and inflammatory response by acting as microRNAs (miRNAs) sponges in IVDD. However, the regulatory role of circRNAs in mediating IVDD remains unknown. This review comprehensively describes the normal anatomic structure and function of IVD, the pathogenesis of IVDD, the characteristics, synthesis, mechanisms, and function of circRNAs. Moreover, we highlighted the 23 circRNAs that mediate ECM metabolism, 16 circRNAs that mediate NPCs apoptosis, circ_0004354 and circ_0040039 that mediate NPCs pyroptosis, and 5 circRNAs that mediate inflammatory response in IVDD. In addition, this review presents suggestions for future studies, such as the need for further investigation on ferroptosis-related circRNAs in IVDD. This review could provide novel insights into the pathogenesis and treatment of IVDD.

FOXO3-Activated circFGFBP1 Inhibits Extracellular Matrix Degradation and Nucleus Pulposus Cell Death via miR-9-5p/BMP2 Axis in Intervertebral Disc Degeneration In Vivo and In Vitro

(1) Background: intervertebral disc degeneration (IVDD) defined as the degenerative changes in intervertebral disc is characterized by extracellular matrix (ECM) degradation and death in nucleus pulposus (NP) cells. (2) Methods: The model of IVDD was established in male Sprague Dawley rats using a puncture of a 21-gauge needle at the endplates located in the L4/5 intervertebral disc. Primary NP cells were stimulated by 10 ng/mL IL-1β for 24 h to mimic IVDD impairment in vitro. (3) Results: circFGFBP1 was downregulated in the IVDD samples. circFGFBP1 upregulation inhibited apoptosis and extracellular matrix (ECM) degradation and promoted proliferation in IL-1β-stimulated NP cells. Additionally, circFGFBP1 upregulation mitigated the loss of NP tissue and the destruction of the intervertebral disc structure in vivo during IVDD. FOXO3 could bind to the circFGFBP1 promoter to enhance its expression. circFGFBP1 upregulated BMP2 expression in NP via sponging miR-9-5p. FOXO3 enhanced the protection of circFGFBP1 in IL-1β-stimulated NP cells, whereas a miR-9-5p increase partly reversed the protection. miR-9-5p downregulation contributed to the survival of IL-1β-stimulated NP cells, which was partially reversed by BMP2 silence. (4) Conclusions: FOXO3 could activate the transcription of circFGFBP1 via binding to its promoter, which resulted in the enhancement of BMP2 via sponging miR-9-5p and then inhibited apoptosis and ECM degradation in NP cells during IVDD.

Circular RNAs: typical biomarkers for bone-related diseases

Bone is a connective tissue that has important functions in the human body. Cells and the extracellular matrix (ECM) are key components of bone and are closely related to bone-related diseases. However, the outcomes of conventional treatments for bone-related diseases are not promising, and hence it is necessary to elucidate the exact regulatory mechanisms of bone-related diseases and identify novel biomarkers for diagnosis and therapy. Circular RNAs (circRNAs) are single-stranded RNAs that form closed circular structures without a 5' cap or 3' tail and polycyclic adenylate tails. Due to their high stability, circRNAs have the potential to be typical biomarkers. Accumulating evidence suggests that circRNAs are involved in bone-related diseases, including osteoarthritis, osteoporosis, osteosarcoma, multiple myeloma, intervertebral disc degeneration, and rheumatoid arthritis. Herein, we summarize the recent research progress on the characteristics and functions of circRNAs, and highlight the regulatory mechanism of circRNAs in bone-related diseases.

Regulatory roles of noncoding RNAs in intervertebral disc degeneration as potential therapeutic targets (Review)

Intervertebral disc degeneration (IDD) is the leading cause of lower back pain, which is one of the primary factors that lead to disability and pose a serious economic burden. The key pathological processes involved are extracellular matrix degradation, autophagy, apoptosis, and inflammation of nucleus pulposus cells. Non-coding RNAs (ncRNAs), including microRNAs, long ncRNAs and circular RNAs, are key regulators of the aforementioned processes. ncRNAs are differentially expressed in tissues of the intervertebral disc between healthy individuals and patients and participate in the pathological progression of IDD via a complex pattern of gene regulation. However, the regulatory mechanisms of ncRNAs in IDD remain unclear. The present review summarizes the latest insights into the regulatory role of ncRNAs in IDD and sheds light on potentially novel therapeutic strategies for IDD that may be implemented in the future.

Pharmacological Effects of Resveratrol in Intervertebral Disc Degeneration: A Literature Review

Intervertebral disc degeneration (IDD) is a high incidence disease of musculoskeletal system that often leads to stenosis, instability, pain and even deformity of the spinal segments. IDD is an important cause of discogenic lower back pain and often leads to large economic burden to families and society. Currently, the treatment of IDD is aimed at alleviating symptoms rather than blocking or reversing pathological progression of the damaged intervertebral disc. Resveratrol (RSV) is a polyphenol phytoalexin first extracted from the Veratrum grandiflflorum O. Loes and can be found in various plants and red wine. Owing to the in-depth study of pharmacological mechanisms, the therapeutic potential of RSV in various diseases such as osteoarthritis, neurodegenerative diseases, cardiovascular diseases and diabetes have attracted the attention of many researchers. RSV has anti-apoptotic, anti-senescent, anti-inflammatory, anti-oxidative, and anabolic activities, which can prevent further degeneration of intervertebral disc cells and enhance their regeneration. With high safety and various biological functions, RSV might be a promising candidate for the treatment of IDD. This review summarizes the biological functions of RSV in the treatment of IDD and to facilitate further research.

Circ0007042 alleviates intervertebral disc degeneration by adsorbing miR-369 to upregulate BMP2 and activate the PI3K/AKt pathway

Background

To identify regulatory ncRNA molecules that can cause differential expression of CDH2 in intervertebral disc degeneration (IDD) and explore whether there are other ways to affect the progression of IDD.

Methods

A primary culture of human nucleus pulposus (NP) cells was established and identified by immunofluorescence. An in vitro IDD model was constructed by compressing human NP cells, and the MTT assay was used to measure cell viability. Changes in the ncRNA group were analysed by RNA-seq. The expression levels of hsa_circ_7042, CDH2, and miR-369-3p were detected by qPCR. Cell apoptosis, senescence, and extracellular matrix (ECM) metabolism were detected by flow cytometry, β-galactosidase staining, and Western blotting. hsa_circ_7042, miR-369-3p, and bone morphogenetic protein 2 (BMP2) were verified by luciferase and RNA immunoprecipitation (RIP) analyses. The PI3K/Akt pathway was validated by transfection of BMP2 siRNA. Furthermore, a mouse model of lumbar spine instability was constructed. circ_7042 adenovirus was packaged and injected into the intervertebral discs of mice, and the influence of circ_7042 overexpression on intervertebral disc degeneration was determined.

Results

Western blotting, qPCR, and flow cytometry analyses confirmed that overexpression of circ_7042 could downregulate miR-369-3p and upregulate the expression of CDH2 and BMP2 in IDD cell and animal models. Additionally, the levels of apoptotic and senescent cells decreased, and ECM degradation decreased. The PI3K/Akt pathway was significantly activated after circ_7042 was overexpressed. The injection of circ_7042-overexpressing adenovirus effectively reduced ECM degradation and the level of apoptosis in NP tissue.

Conclusions

circ_7042 could upregulate the expression of CDH2 and BMP2 by absorbing miR-369-3p, and the increased BMP2 activated the PI3K/Akt pathway, thus improving IDD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02895-7.

Interleukin-18 Inhibition Protects Against Intervertebral Disc Degeneration via the Inactivation of Caspase-3/9 Dependent Apoptotic Pathways

BACKGROUND

The present study was designed to identify and understand the potential effectiveness of therapeutic target in intervertebral disc degeneration (IVDD) and its regulation mechanism.

METHODS

The role and mechanism of interleukin-18 (IL-18) in the disease were investigated. The IVDD degenerative nucleus pulposus (NP) tissues from the human and mouse models were used.A total of three groups of Male BALB/c mice were randomly made i.e control, IVDD, and IVDD+Ad-shIL-18 groups. After Ad-shIL-18 transfection, the expression of ECM synthesis related protein Aggrecan (ACAN) and Collagen II, apoptotic effector Caspases (Caspase-3, 8, 9, 12 and Cleaved-Caspase 3, 8, 9, 12), pro-apoptotic gene Bax and anti-apoptotic factors Bcl-2 in NP cells of the human were evaluated.

RESULTS

The results of our study revealed that the mRNA and protein expression levels of IL-18 were notably increased in the NP tissues of IVDD patients and mice models. In the IVDD mice model, Ad-sh-IL-18 treatment reversed the IVDD progression. The levels of Aggrecan and Collagen II, contributing to ECM degradation in NP cells, were also significantly increased. Additionally, Ad-sh-IL-18 could inhibit the NP cell's apoptosis via regulating the caspase-3/9 pathway.

CONCLUSION

The IL-18 knockdown via the caspase-3/9 pathway, might reduce the NP cell's death as well as the imbalance between catabolism and anabolism of ECM in IVDD.

Single Impact Injury of Vertebral Endplates Without Structural Disruption, Initiates Disc Degeneration Through Piezo1 Mediated Inflammation and Metabolism Dysfunction

STUDY DESIGN

In vitro experimental study.

OBJECTIVE

To establish an axial impact injury model of intervertebral disc (IVD) and to investigate if a single impact injury without endplate structural disruption could initiate intervertebral disc degeneration (IDD), and what is the roles of Piezo1 in this process.

SUMMARY OF BACKGROUND DATA

Although IDD process has been confirmed to be associated with structural failures such as endplate fractures, whether a single impact injury of the endplates without structural disruption could initiate IDD remains controversial. Previous studies reported that Piezo1 mediated inflammation participated in the progression of IDD induced by mechanical stretch; however, the roles of Piezo1 in IVD impact injury remain unknown.

METHODS

Rats spinal segments were randomly assigned into Control, Low, and High Impact groups, which were subjected to pure axial impact loading using a custom-made apparatus, and cultured for 14 days. The degenerative process was investigated by using histomorphology, real-time Polymerase Chain Reaction(PCR), western-blot, immunofluorescence, and energy metabolism of IVD cell. The effects of Piezo1 were investigated by using siRNA transfection, real-time PCR, western-blot, and immunofluorescence.

RESULTS

The discs in both of the impact groups presented degenerative changes after 14 days, which showed significant up-regulation of Piezo1, NLRP3 inflammasome, the catabolic (MMP-9, MMP-13), and pro-inflammatory gene (IL-1β) expression than that of the control group (P < 0.05), accompanied by significantly increased release of ATP, lactate, nitric oxide (NO), and glucose consumption of IVD cells at first 7 days. Silencing Piezo1 reduced the activation of NLRP3 inflammasome and IL-1β expression in the nucleus pulposus induced by impact injury.

CONCLUSION

It demonstrated that not only fracture of the endplate but also a single impact injury without structural impairment could also initiate IDD, which might be mediated by activation of Piezo1 induced inflammation and abnormal energy metabolism of IVD cells.Level of Evidence: N/A.

Hsa_circ_0134111 promotes intervertebral disc degeneration via sponging miR-578

Intervertebral disc degeneration (IDD) is a chronic degenerative and age-dependent process characterized by aberrant apoptosis, proliferation, synthesis, and catabolism of the extracellular matrix of the nucleus pulposus (NP) cells. Recently, studies showed that circular RNAs play important roles in the development of many diseases. However, the role of circRNAs in IDD development remains unknown. We showed that circ_0134111 level was overexpressed in IDD tissue samples as compar-ed to control tissues. The upregulation of circ_0134111 was more drastic in the moderate and severe IDD cases than in those with mild IDD. In addition, we showed that interleukin-1β and tumor necrosis factor-α exposure significantly enhanced circ_0134111 expression in NP cells. Furthermore, ectopic expression of circ_0134111 induced proliferation, pro-inflammatory cytokine secretion, and ECM degradation in the NP cells. We also showed that circ_0134111 directly interacted with microRNA (miR)-578 in NP cells where elevated expression of circ_0134111 enhanced the ADAMTS-5 and MMP-9 expression. Moreover, miR-578 expression was significantly decreased in IDD patients and the miR-578 expression was negatively correlated with circ_0134111 expression in the IDD samples. Interleukin-1β and tumor necrosis factor-α exposure significantly decreased miR-578 levels in NP cells, in which ectopic miR-578 expression inhibited cell growth, pro-inflammatory cytokine expression, and ECM degradation. Finally, we showed that circ_0134111 overexpression induced the IDD-related phenotypic changes through inhibiting miR-578. These data suggested that circ_0134111 could promote the progression of IDD through enhancing aberrant NP cell growth, inflammation, and ECM degradation partly via regulating miR-578.

Circular RNAs in Intervertebral Disc Degeneration: An Updated Review

Low back pain, a common medical condition, could result in severe disability and inflict huge economical and public health burden. Its pathogenesis is attributed to multiple etiological factors, including intervertebral disc degeneration (IDD). Emerging evidence suggests that circular RNAs (circRNAs), a major type of regulatory non-coding RNA, play critical roles in cellular processes that are pertinent to IDD development, including nucleus pulposus cell proliferation and apoptosis as well as extracellular matrix deposition. Increasing number of translational studies also indicated that circRNAs could serve as novel biomarkers for the diagnosis of IDD and/or predicting its clinical outcomes. Our review aims to discuss the recent progress in the functions and mechanisms of newly discovered IDD-related circRNAs.

The potential mechanisms and application prospects of non-coding RNAs in intervertebral disc degeneration

Low back pain (LBP) is one of the most common musculoskeletal symptoms and severely affects patient quality of life. The majority of people may suffer from LBP during their life-span, which leading to huge economic burdens to family and society. According to the series of the previous studies, intervertebral disc degeneration (IDD) is considered as the major contributor resulting in LBP. Furthermore, non-coding RNAs (ncRNAs), mainly including microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), can regulate diverse cellular processes, which have been found to play pivotal roles in the development of IDD. However, the potential mechanisms of action for ncRNAs in the processes of IDD are still completely unrevealed. Therefore, it is challenging to consider ncRNAs to be used as the potential therapeutic targets for IDD. In this paper, we reviewed the current research progress and findings on ncRNAs in IDD: i). ncRNAs mainly participate in the process of IDD through regulating apoptosis of nucleus pulposus (NP) cells, metabolism of extracellular matrix (ECM) and inflammatory response; ii). the roles of miRNAs/lncRNAs/circRNAs are cross-talk in IDD development, which is similar to the network and can modulate each other; iii). ncRNAs have been attempted to combat the degenerative processes and may be promising as an efficient bio-therapeutic strategy in the future. Hence, this review systematically summarizes the principal pathomechanisms of IDD and shed light on the therapeutic potentials of ncRNAs in IDD.

Roles of circular RNAs in the pathogenesis of intervertebral disc degeneration (Review)

Lower back pain (LBP) is an extremely common symptom and is recognized as a leading contributor to disability and disease burden globally. Intervertebral disc degeneration (IDD) represents a major cause of LBP. However, the molecular mechanisms involved in the pathogenesis of IDD remain unclear, and currently available treatments, including conservative and surgical options, fail to effectively delay, stop or reverse the progression of IDD. Circular RNAs (circRNAs) are a newly discovered group of covalently closed, single-stranded and endogenous non-coding RNAs. A growing body of research has revealed that a number of circRNAs are widely and aberrantly expressed in IDD tissues. Furthermore, they play important roles in the pathogenesis of IDD, including proliferation, apoptosis, senescence, mitophagy, inflammation and extracellular matrix metabolism, mainly by acting as sponges for microRNAs. The present review aims to summarize the current understanding on the mechanisms of circRNA-mediated regulation in IDD.

LncRNA H19 Aggravates Intervertebral Disc Degeneration by Promoting the Autophagy and Apoptosis of Nucleus Pulposus Cells Through the miR-139/CXCR4/NF-κB Axis

The etiology of lumbocrural pain is closely related to intervertebral disc degeneration (IDD). Long noncoding RNAs (lncRNAs) serve crucial roles in IDD progression. This study investigated the effect of lncRNA H19 on autophagy and apoptosis of nucleus pulposus cells (NPCs) in IDD. The rat model of IDD was established. Normal NPCs and degenerative NPCs (DNPCs) were cultured in vitro. H19 expression in IDD rat was detected. DNPCs were treated with si-H19 to evaluate autophagy and apoptosis of DNPCs. The binding relationships between H19 and miR-139-3p, and miR-139-3p and CXCR4 were verified. DNPCs were co-transfected si-H19 and miR-139-3p inhibitor. The phosphorylation of NF-κB pathway-related p65 in DNPCs was detected. LncRNA H19 was upregulated in IDD rats. Downregulation of H19 inhibited autophagy and apoptosis of DNPCs. LncRNA H19 sponged miR-139-3p to inhibit CXCR4 expression. si-H19 and miR-139-3p inhibitor co-treatment induced autophagy and apoptosis, and enhanced CXCR4 expression. si-H19 decreased p-p65 phosphorylation, while si-H19 and miR-139-3p inhibitor co-treatment partially elevated p-p65 phosphorylation. In conclusion, lncRNA H19 facilitated the autophagy and apoptosis of DNPCs by the miR-139-3p/CXCR4/NF-κB axis, thereby aggravating IDD. This study may offer new insights for the management of IDD.

Role of PI3K/AKT Signaling Pathway in Nucleus Pulposus Cells

OBJECTIVE

To investigate the role of PI3K/AKT signaling pathway in nucleus pulposus (NP) cells.

METHODS

Nucleus pulposus (NP) cells were isolated from SD rat, and thereafter, passage three (P3) NP cells were divided into the following experimental groups: control, PI3K/AKT agonist IGF-1 (25 ng/ml, 50 ng/ml, and 100 ng/ml), and PI3K/AKT inhibitor LY294002 (5 μM, 10 μM, and 20 μM). Flow cytometry and BrdU cell proliferation assays were performed to assess apoptosis and the proliferation rate of NP cells. Western blot analysis was performed to examine the protein expression level of Col II, Col X, Aggrecan, and MMP13.

RESULTS

PI3K/AKT inhibitor LY294002 increased the rate of apoptosis in NP cells when compared to the control and decreased the proliferation rate when compared to control. Moreover, LY294002 decreased the protein expression level of Col-II and Aggrecan in NP cells. At the same time, LY294002 increased the protein expression level of MMP13 and Col-X in NP cells. Through activating PI3K/AKT, IGF-1 increased the proliferation rate when compared to control and decreased the rate of apoptosis when compared to control. Additionally, IGF-1 decreased the protein expression level of MMP13 and Col-X and increased Col-II and Aggrecan in NP cells.

CONCLUSION

The inhibition of PI3K/AKT signaling pathway accelerated the apoptosis of NP cells and facilitated the extracellular matrix degradation. However, the activation of PI3K/AKT pathway partly prevented the NP cell from apoptosis and promoted their proliferation. Meanwhile, its activation also delayed the loss of extracellular matrix.

Proper animal experimental designs for preclinical research of biomaterials for intervertebral disc regeneration

Low back pain is a vital musculoskeletal disease that impairs life quality, leads to disability and imposes heavy economic burden on the society, while it is greatly attributed to intervertebral disc degeneration (IDD). However, the existing treatments, such as medicines, chiropractic adjustments and surgery, cannot achieve ideal disc regeneration. Therefore, advanced bioactive therapies are implemented, including stem cells delivery, bioreagents administration, and implantation of biomaterials etc. Among these researches, few reported unsatisfying regenerative outcomes. However, these advanced therapies have barely achieved successful clinical translation. The main reason for the inconsistency between satisfying preclinical results and poor clinical translation may largely rely on the animal models that cannot actually simulate the human disc degeneration. The inappropriate animal model also leads to difficulties in comparing the efficacies among biomaterials in different reaches. Therefore, animal models that better simulate the clinical charateristics of human IDD should be acknowledged. In addition, in vivo regenerative outcomes should be carefully evaluated to obtain robust results. Nevertheless, many researches neglect certain critical characteristics, such as adhesive properties for biomaterials blocking annulus fibrosus defects and hyperalgesia that is closely related to the clinical manifestations, e.g., low back pain. Herein, in this review, we summarized the animal models established for IDD, and highlighted the proper models and parameters that may result in acknowledged IDD models. Then, we discussed the existing biomaterials for disc regeneration and the characteristics that should be considered for regenerating different parts of discs. Finally, well-established assays and parameters for in vivo disc regeneration are explored.

Fabrication of a Polylactide-Glycolide/Poly-ε-Caprolactone/Dextran/Plastrum Testudinis Extract Composite Anti-Inflammation Nanofiber Membrane via Electrospinning for Annulus Fibrosus Regeneration

Tissue engineering is a promising approach for the treatment of chronic lower back pain (LBP) caused by intervertebral disc degeneration (IDD) resulting from degeneration and inflammation of annulus fibrosus (AF) tissue. However, scaffold with an anti-inflammatory effect on AF cells has not been reported. In this study, we fabricated a polylactide-glycolide (PLGA)/poly-ε-caprolactone (PCL)Zdextran (DEX) composite membrane loaded with plastrum testudinis extract (PTE), a Traditional Chinese Medicine herbal extract, via electrospinning. The membranes were characterized by mechanical measurements and scanning electron microscopy (SEM). Using an in vitro inflammation model induced by interleukin (IL)-1β, the cytocompatibility and anti-inflammatory effects of the composites were investigated by CCK-8 assay and flow cytometry. Potential regulatory mechanisms were examined by RT-qPCR and Western blotting. The results showed that the P10P8D2 (PLGA 10 g, PCL 8 g, DEX 2 g) composite nanofiber membrane exhibited the most uniform diameter distribution, best mechanical properties, a moderate degradation rate, and the best cytocompatibility characteristics. The optimal concentration of PTE was 120 µg/mL. Importantly, P10P8D2 combined with PTE exhibited anti-inflammatory and cell proliferation promotion effects. Moreover, the NF-κBB/NLRP3/IL-β signaling pathway was inactivated. Our findings suggested that the nanofiber membrane composed of P10P8D2 and PTE has anti-inflammatory and pro-proliferation effects on AF cells. It may provide an effective strategy for AF tissue regeneration.

Bromodomain-containing protein 7 regulates matrix metabolism and apoptosis in human nucleus pulposus cells through the BRD7-PI3K-YAP1 signaling axis

Intervertebral disc degeneration (IDD) results from dysregulated metabolism of the extracellular matrix of the nucleus pulposus (NP) and involves the participation of inflammatory factors such as TNF-α. Bromodomain-containing protein 7 (BRD7) shows considerable potential for anti-inflammatory applications. Herein, we investigated the role of BRD7 in IDD. The immunohistochemistry results demonstrated decreased BRD7 expression in severely degenerated human NP tissues compared to those showing mild degeneration. Lentiviruses and adenoviruses were used to knock down or overexpress BRD7 and YAP1, respectively. Our results revealed that BRD7 knockdown promoted matrix degradation and suppressed PI3K and YAP1 expression, while BRD7 overexpression alleviated matrix degradation and promoted YAP1 and PI3K expression. In addition, PI3K inhibition augmented matrix degradation, enhanced apoptosis, and reduced YAP1 expression, whereas YAP1 overexpression promoted matrix synthesis, suppressed apoptosis and promoted PI3K expression. Besides, BRD7 overexpression reversed the reductions in sulfated glycosaminoglycan levels induced by TNF-α, but this effect was blocked by PI3K or YAP1 inhibitors. Moreover, YAP1 and PI3K were shown to interact through coimmunoprecipitation analysis. In summary, our results demonstrate that BRD7 can regulate matrix metabolism and apoptosis in human NP cells through the BRD7-PI3K-YAP1 signaling axis. This study might provide new insights into the prevention and treatment of IDD.

Identification of Differentially Expressed circRNAs, miRNAs, and Genes in Patients Associated with Cartilaginous Endplate Degeneration

Background

Intervertebral disc degeneration (IDD) disease is a global challenge because of its predominant pathogenic factor in triggering low back pain, whereas cartilaginous endplate degeneration (CEPD) is the main cause of IDD. Accumulating evidence have indicated that the differentially expressed microRNAs (DEMs) and differentially expressed genes (DEGs) have been determined to be involved in multiple biological processes to mediate CEPD progression. However, the differentially expressed circular RNAs (DECs) and their potential biofunctions in CEPD have not been identified.

Methods

GSE153761 dataset was analyzed using R software to predict DECs, DEMs, and DEGs. Pathway enrichment analysis of DEGs and host genes of DECs and protein-protein interaction network of DEGs were conducted to explore their potential biofunctions. Furthermore, we explore the potential relationship between DEGs and DECs.

Results

There were 74 DECs, 17 DEMs, and 68 DEGs upregulated whereas 50 DECs, 16 DEMs, and 67 DEGs downregulated in CEPD group. Pathway analysis unveiled that these RNAs might regulate CEPD via mediating inflammatory response, ECM metabolism, chondrocytes apoptosis, and chondrocytes growth. A total of 17 overlapping genes were predicted between the host genes of DEGs and DECs, such as SDC1 and MAOA. Moreover, 6 upregulated DECs, of which hsa_circ_0052830 was the most upregulated circRNA in CEPD, were derived from the host genes SDC1, whereas 8 downregulated DECs were derived from the host genes MAOA.

Conclusion

This will provide novel clues for future experimental studies to elucidate the pathomechanism of CEPD and therapeutic targets for CEPD-related diseases.