The Roles of circRNAs in Intervertebral Disc Degeneration: Inflammation, Extracellular Matrix Metabolism, and Apoptosis

Circular RNA KIAA0564 Serves as a Competitive Endogenous RNA for MicroRNA-424-5p, Mediating the Expression of Lysine Demethylase 4a, Thereby Facilitating Intervertebral Disc Degeneration

A growing body of research has confirmed the involvement of circular RNAs (circRNAs) in the regulation of intervertebral disc degeneration (IDD) progression. However, the underlying molecular networks remain largely elusive. This study aimed to explore whether a novel circRNA, named circKIAA0564, affects nucleus pulposus (NP) cell injury and to elucidate its molecular mechanism. Both in vivo and in vitro IDD models were established, and the expression patterns of circKIAA0564/miR-424-5p/lysine demethylase 4a (KDM4A) were evaluated through quantitative reverse transcription PCR and Western blot analysis. Actinomycin D, RNase R, and Northern blotting were utilized to assess the circular structure of circKIAA0564. The Cell Counting Kit-8, flow cytometry, enzyme-linked immunosorbent assay, commercial assay kits, Western blotting, and reactive oxygen species (ROS) probes were employed to assess the inflammatory and oxidative stress status in NP cells and tissues. Hematoxylin and eosin and TUNEL staining were used to evaluate pathological damage in mouse NP tissues. RNA immunoprecipitation and dual-luciferase reporter assays were conducted to assess the direct targeting relationships among circKIAA0564, miR-424-5p, and KDM4A. CircKIAA0564 was found to be abnormally overexpressed in IDD, functioning as a novel circRNA. Knockdown of circKIAA0564 ameliorated interleukin-1 beta (IL-1β)-induced inflammation and oxidative stress in NP cells. The therapeutic effect of circKIAA0564 knockdown on NP cells was reversed by the silencing of miR-424-5p. Overexpression of circKIAA0564 exacerbated IL-1β-induced NP cell injury, a process that was reversed by knockdown of KDM4A. CircKIAA0564 activated the toll-like receptor 4 (TLR4)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)/NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) signaling pathway by regulating the miR-424-5p/KDM4A axis. CircKIAA0564 exacerbates IL-1β-induced inflammation and oxidative stress in NP cells by competitively binding miR-424-5p, thereby mediating KDM4A and activating the TLR4/NF-κB/NLRP3 signaling pathway. These findings provide robust data support for targeted therapy of IDD and the development of future pharmaceuticals.

Exosomal U2AF2 derived from human bone marrow mesenchymal stem cells attenuates the intervertebral disc degeneration through circ_0036763/miR-583/ACAN axis

Intervertebral disc degeneration (IDD) is one of the major leading causes of back pain affecting the patient's quality of life. However, the roles of circular RNA (circRNA) in IDD remains unclear. This study aimed to explore the function and underlying mechanism of circ_0036763 in IDD. In this study, expressions of circ_0036763, U2 small nuclear RNA auxiliary factor 2 (U2AF2), miR-583 and aggrecan (ACAN) in primary human nucleus pulposus cells (HNPCs) derived from IDD patients and healthy controls were detected by quantitative real-time reverse transcription-PCR (qRT-PCR) or Western blot (WB). The relationship between pre-circ_0036763 and U2AF2, circ_0036763 and miR-583, miR-583 and ACAN mRNA was determined by bioinformatic analysis, miRNA pull down or RNA immunoprecipitation (RIP) assay. The expressions of Collagen I and Collagen II were evaluated by WB. Co-culture of bone marrow mesenchymal stem cells (bMSCs) or bMSCs-derived exosomes and HNPCs were performed to identify the effect of U2AF2 on the mature of circ_0036763 and ACAN. Results indicated that circ_0036763, U2AF2 and ACAN were downregulated while miR-583 was upregulated in HNPCs derived from IDD patients compared with that in normal HNPCs. Besides, overexpression of circ_0036763 elevated the expressions of ACAN and Collagen II whereas reduced Collagen I expression in HNPCs. Moreover, U2AF2 promoted the mature of circ_0036763, and circ_0036763 positively regulated ACAN by directly sponging miR-583. Furthermore, exosomal U2AF2 derived from bMSCs could increase U2AF2 levels in HNPCs and subsequently regulate the expression of ACAN by circ_0036763/miR-583 axis. In summary, circ_0036763 modified by exosomal U2AF2 derived from bMSCs alleviated IDD through regulating miR-583/ACAN axis in HNPCs. Thus, this study might provide novel therapeutic targets for IDD.

Bushen Huoxue Formula Inhibits IL-1β-Induced Apoptosis and Extracellular Matrix Degradation in the Nucleus Pulposus Cells and Improves Intervertebral Disc Degeneration in Rats

Background

The method of action of Bushen Formula (BSHXF) in the treatment of intervertebral disc degeneration (IVDD) was uncovered in this work using in vivo and in vitro tests. To clarify the mechanism of action of BSHXF, we validated the rat intervertebral disc degeneration model and the nucleus pulposus cell degeneration model.

Methods

In an in vivo model of IVDD the study explores the impact of BSHXF on mitochondrial function, pro-inflammatory cytokines, pro-apoptotic factors, and matrix metalloproteinases. Additionally, it evaluates the induced degeneration of nucleus pulposus (NP) cells in an in vitro model stimulated by interleukin-1 β (IL-1β). The study measures the effects of BSHXF on both the inflammatory response and mitochondrial function.

Results

The MRI results showed that BSHXF reduced intervertebral disc volume reduction and degradation of NP tissue. HE, SO-FG and immunofluorescence further confirmed the protective effect of BSHXF on degenerative intervertebral discs. BSHXF reduced the inflammatory levels of IL-6 IL-1β and TNF-α in degenerative intervertebral disc tissue. Meanwhile, JC-1, mPTP and ROS detection revealed that BSHXF can restore mitochondrial function by regulating the expression of antioxidant proteins, playing a protective role in NP cells. Finally, the WB results showed that BSHXF can alleviate IL-1β mediate the degeneration of NP cells. BSHXF can alleviate NP cell apoptosis by inhibiting the expression of bax, cleaved caspase-3, caspase-3, and cyt-c, and increasing the expression of Bcl-2.

Conclusion

This study reveals that BSHXF inhibits the development of inflammatory factors, which may play a significant role in intervertebral disc degeneration. This implies that BSHXF is a suitable herbal medication for future research into inflammatory cytokine treatment.

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.

N6-methyladenosine hypomethylation of circGPATCH2L regulates DNA damage and apoptosis through TRIM28 in intervertebral disc degeneration

Circular RNAs (circRNAs) are a class of noncoding RNAs that have been found to be involved in intervertebral disc degeneration (IVDD) progression, and N6-methyladenosine (m6A) broadly exists in circRNAs. Here, we identified circGPATCH2L with a low m6A methylation level to be upregulated in degenerative nucleus pulposus tissues. Mechanistically, as a protein decoy for tripartite motif containing 28 (TRIM28) within aa 402-452 region, circGPATCH2L abrogates the phosphorylation of TRIM28 and inhibits P53 degradation, which contributes to DNA damage accumulation and cellular apoptosis and leads to IVDD progression. Moreover, m6A-methylated circGPATCH2L is recognised and endoribonucleolytically cleaved by a YTHDF2-RPL10-RNase P/MRP complex to maintain the physiological state of nucleus pulposus cells. Thus, our data show the physiological significance of m6A modification in regulating circRNA abundance and provide a potentially effective therapeutic target for the treatment of IVDD.

Circular RNA hsa_circ_0000690 as a potential biomarker for diagnosis and prognosis of intracranial aneurysm: Closely relating to the volume of hemorrhage

PURPOSE

This study aimed to explore circular RNA (circRNA) hsa_circ_0000690 as a potential biomarker for diagnosis and prognosis of intracranial aneurysm (IA) and its relationship with clinical factors and complications of IA.

MATERIAL/METHODS

216 IA patients admitted to the neurosurgery department of our hospital from January 2019 to December 2020 were selected as the experimental group, and 186 healthy volunteers were selected as the control group. The expression of hsa_circ_0000690 in peripheral blood was detected by quantitative real-time PCR, and its diagnostic value was assessed by receiver operating characteristic curve. Relationship between hsa_circ_0000690 and clinical factors of IA was assessed by chi-square test. Nonparametric test was used in univariate analysis, and regression analysis was used in multivariate analysis. Multivariate Cox proportional hazards regression analysis was used to analyze the survival time.

RESULTS

CircRNA hsa_circ_0000690 of IA patients was relatively lower than that in the control group (p < .001). The AUC of hsa_circ_0000690 was 0.752, the specificity was 0.780, and sensitivity was 0.620, with diagnostic threshold of 0.0449. In addition, hsa_circ_0000690 expression was correlated with Glasgow Coma Scale, the volume of subarachnoid hemorrhage, modified Fisher scale, Hunt-Hess levels and surgical type. For hydrocephalus and delayed cerebral ischemia, hsa_circ_0000690 was significant in univariate analysis, but nonsignificant in multivariate analysis. For prognosis, hsa_circ_0000690 was significantly associated with modified Rankin Scales after surgery for 3 months, but not associated with survival time.

CONCLUSIONS

The expression of hsa_circ_0000690 can act as a diagnostic marker for IA and predict the prognosis of 3 months after operation and is closely related to the volume of hemorrhage.

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.

Targeting Autophagy for Developing New Therapeutic Strategy in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is a prevalent cause of low back pain. IVDD is characterized by abnormal expression of extracellular matrix components such as collagen and aggrecan. In addition, it results in dysfunctional growth, senescence, and death of intervertebral cells. The biological pathways involved in the development and progression of IVDD are not fully understood. Therefore, a better understanding of the molecular mechanisms underlying IVDD could aid in the development of strategies for prevention and treatment. Autophagy is a cellular process that removes damaged proteins and dysfunctional organelles, and its dysfunction is linked to a variety of diseases, including IVDD and osteoarthritis. In this review, we describe recent research findings on the role of autophagy in IVDD pathogenesis and highlight autophagy-targeting molecules which can be exploited to treat IVDD. Many studies exhibit that autophagy protects against and postpones disc degeneration. Further research is needed to determine whether autophagy is required for cell integrity in intervertebral discs and to establish autophagy as a viable therapeutic target for IVDD.