Exosome-Transported circRNA_0000253 Competitively Adsorbs MicroRNA-141-5p and Increases IDD

MicroRNA-targeting nanomedicines for the treatment of intervertebral disc degeneration

Low back pain stands as a pervasive global health concern, afflicting almost 80% of adults at some point in their lives with nearly 40% attributable to intervertebral disc degeneration (IVDD). As only symptomatic relief can be offered to patients there is a dire need for innovative treatments.Given the accumulating evidence that multiple microRNAs (miRs) are dysregulated during IVDD, they could have a huge potential against this debilitating condition. The way miRs can profoundly modulate signaling pathways and influence several cellular processes at once is particularly exciting to tackle this multifaceted disorder. However, miR delivery encounters extracellular and intracellular biological barriers. A promising technology to address this challenge is the vectorization of miRs within nanoparticles, providing both protection and enhancing their uptake within the scarce target cells of the degenerated IVD. This comprehensive review presents the diverse spectrum of miRs' connection with IVDD and demonstrates their therapeutic potential when vectorized in nanomedicines.

CircEYA3 aggravates intervertebral disc degeneration through the miR-196a-5p/EBF1 axis and NF-κB signaling

Intervertebral disc degeneration (IDD) is a well-established cause of disability, and extensive evidence has identified the important role played by regulatory noncoding RNAs, specifically circular RNAs (circRNAs) and microRNAs (miRNAs), in the progression of IDD. To elucidate the molecular mechanism underlying IDD, we established a circRNA/miRNA/mRNA network in IDD through standardized analyses of all expression matrices. Our studies confirmed the differential expression of the transcription factors early B-cell factor 1 (EBF1), circEYA3, and miR-196a-5p in the nucleus pulposus (NP) tissues of controls and IDD patients. Cell proliferation, apoptosis, and extracellular mechanisms of degradation in NP cells (NPC) are mediated by circEYA3. MiR-196a-5p is a direct target of circEYA3 and EBF1. Functional analysis showed that miR-196a-5p reversed the effects of circEYA3 and EBF1 on ECM degradation, apoptosis, and proliferation in NPCs. EBF1 regulates the nuclear factor kappa beta (NF-кB) signalling pathway by activating the IKKβ promoter region. This study demonstrates that circEYA3 plays an important role in exacerbating the progression of IDD by modulating the NF-κB signalling pathway through regulation of the miR196a-5p/EBF1 axis. Consequently, a novel molecular mechanism underlying IDD development was elucidated, thereby identifying a potential therapeutic target for future exploration.

Sirtuins in intervertebral disc degeneration: current understanding

BACKGROUND

Intervertebral disc degeneration (IVDD) is one of the etiologic factors of degenerative spinal diseases, which can lead to a variety of pathological spinal conditions such as disc herniation, spinal stenosis, and scoliosis. IVDD is a leading cause of lower back pain, the prevalence of which increases with age. Recently, Sirtuins/SIRTs and their related activators have received attention for their activity in the treatment of IVDD. In this paper, a comprehensive systematic review of the literature on the role of SIRTs and their activators on IVDD in recent years is presented. The molecular pathways involved in the regulation of IVDD by SIRTs are summarized, and the effects of SIRTs on senescence, inflammatory responses, oxidative stress, and mitochondrial dysfunction in myeloid cells are discussed with a view to suggesting possible solutions for the current treatment of IVDD.

PURPOSE

This paper focuses on the molecular mechanisms by which SIRTs and their activators act on IVDD.

METHODS

A literature search was conducted in Pubmed and Web of Science databases over a 13-year period from 2011 to 2024 for the terms "SIRT", "Sirtuin", "IVDD", "IDD", "IVD", "NP", "Intervertebral disc degeneration", "Intervertebral disc" and "Nucleus pulposus".

RESULTS

According to the results, SIRTs and a large number of activators showed positive effects against IVDD.SIRTs modulate autophagy, myeloid apoptosis, oxidative stress and extracellular matrix degradation. In addition, they attenuate inflammatory factor-induced disc damage and maintain homeostasis during disc degeneration. Several clinical studies have reported the protective effects of some SIRTs activators (e.g., resveratrol, melatonin, honokiol, and 1,4-dihydropyridine) against IVDD.

CONCLUSION

The fact that SIRTs and their activators play a hundred different roles in IVDD helps to better understand their potential to develop further treatments for IVDD.

NOVELTY

This review summarizes current information on the mechanisms of action of SIRTs in IVDD and the challenges and limitations of translating their basic research into therapy.

The circular RNA expression profile of human auricle cartilage and the role of circCOL1A2 in isolated microtia

Microtia is one of the most common craniofacial birth defects worldwide, and its primary clinical manifestation is auricle deformity. Epigenetic factors are known to contribute to the etiology of microtia, yet the involvement of circular RNAs (circRNAs) in human auricle development and their association with microtia remains poorly understood. In this study, we aimed to analyze differentially expressed circRNAs and explore their functional implications in isolated microtia. By employing circRNA microarray analysis and bioinformatics approaches, we identified 340 differentially expressed circRNAs in auricle cartilage of patients with isolated microtia, comprising 152 upregulated and 188 downregulated circRNAs. A circRNA-mRNA co-expression network was constructed, followed by gene ontology analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Subsequently, we selected four significantly upregulated circRNAs from the co-expression network based on their association with cartilage development and validated their expressions in 30 isolated microtia and 30 control clinical auricle cartilage samples. Among these circRNAs, circCOL1A2, the most significantly upregulated circRNA, was selected as a representative circRNA for investigating its role in isolated microtia. Overexpression of circCOL1A2 significantly inhibited chondrocyte proliferation and chondrogenic differentiation of human mesenchymal stem cells. Additionally, circCOL1A2 upregulated Dermatan Sulfate Epimerase Like (DSEL) expression by sponging miR-637 through the competing endogenous RNA (ceRNA) mechanism. Notably, the downregulation of DSEL attenuated the inhibitory effect of circCOL1A2 overexpression on cell proliferation and chondrogenic differentiation. Collectively, these findings highlight the involvement of circCOL1A2 in the pathogenesis of isolated microtia and emphasize the potential significance of dysregulated circRNAs in disease development.

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.

Hypoxic Bone Mesenchymal Stem Cell-Derived Exosomes Direct Schwann Cells Proliferation, Migration, and Paracrine to Accelerate Facial Nerve Regeneration via circRNA_Nkd2/miR-214-3p/MED19 Axis

Background

Facial nerves have the potential for regeneration following injury, but this process is often challenging and slow. Schwann cells (SCs) are pivotal in this process. Bone mesenchymal stem cells (BMSC)-derived exosomes promote tissue repair through paracrine action, with hypoxic preconditioning enhancing their effects. The main purpose of this study was to determine whether hypoxia-preconditioned BMSC-derived exosomes (Hypo-Exos) exhibit a greater therapeutic effect on facial nerve repair/regeneration and reveal the mechanism.

Methods

CCK-8, EdU, Transwell, and ELISA assays were used to evaluate the functions of Hypo-Exos in SCs. Histological analysis and Vibrissae Movements (VMs) recovery were used to evaluate the therapeutic effects of Hypo-Exos in rat model. circRNA array was used to identify the significantly differentially expressed exosomal circRNAs between normoxia-preconditioned BMSC-derived exosomes (Nor-Exos) and Hypo-Exos. miRDB, TargetScan, double luciferase assay, qRT-PCR and WB were used to predict and identify potential exosomal cirRNA_Nkd2-complementary miRNAs and its target gene. The function of exosomal circRNA_Nkd2 in facial nerve repair/regeneration was evaluated by cell and animal experiments.

Results

This study confirmed that Hypo-Exos more effectively promote SCs proliferation, migration, and paracrine function, accelerating facial nerve repair following facial nerve injury (FNI) compared with Nor-Exos. Furthermore, circRNA analysis identified significant enrichment of circRNA_Nkd2 in Hypo-Exos compared with Nor-Exos. Exosomal circRNA_Nkd2 positively regulates mediator complex subunit 19 (MED19) expression by sponging rno-miR-214-3p.

Conclusion

Our results demonstrated a mechanism by which Hypo-Exos enhanced SCs proliferation, migration, and paracrine function and facial nerve repair and regeneration following FNI through the circRNA_Nkd2/miR-214-3p/Med19 axis. Hypoxic preconditioning is an effective and promising method for optimizing the therapeutic action of BMSC-derived exosomes in FNI.

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.

Hsa_circ_0001946 Ameliorates Mechanical Stress-induced Intervertebral Disk Degeneration Via Targeting miR-432-5p and SOX9

STUDY DESIGN

Experimental analysis of circular RNA in intervertebral disk degeneration (IDD).

OBJECTIVE

This study aimed to explore the roles of hsa_circ_0001946 (circ-CDR1as) in mechanical stress-induced nucleus pulposus cell injury in IDD.

SUMMARY OF BACKGROUND DATA

Mechanical stress is an important pathogenic factor for IDD. Excessive compression stress leads to nucleus pulposus (NP) cell apoptosis and extracellular matrix (ECM) degradation and accelerated IDD. Circ-CDR1as is associated with various degenerative conditions, but its role in IDD is not clear. Herein, we explored the roles and mechanisms of circ-CDR1as in IDD in vitro.

MATERIALS AND METHODS

An in vitro model of IDD was constructed by treating NP cells with 1.0 MPa compression stress. Quantitative real-time polymerase chain reaction assay was used for detecting the expression of circ-CDR1as and miR-432-5p. Immunofluorescent analysis was performed for MMP13 detection. Western blot assay was performed for detecting apoptosis and ECM-related protein expression. Flow cytometry analysis was used for cell apoptosis analysis. The dual-luciferase reporter was used to analyze the interaction between miR-432-5p and circ-CDR1as or SOX9. Differences in means between groups were evaluated using the Student t test or one-way analysis of variance.

RESULTS

In compression-treated human NP cells, we found that circ-CDR1as was significantly downregulated. Functional experiments showed that circ-CDR1as overexpression reduced the compression-induced apoptosis and ECM degradation in NP cells. Further research indicated that circ-CDR1as could act as a molecular sponge for miR-432-5p, a miRNA that enhanced compression-induced damage of NP cells by inhibiting the expression of SOX9. The luciferase reporter experiments also showed that the mutual dialogue between circ-CDR1as and miR-432-5p regulated the expression of SOX9.

CONCLUSIONS

Circ-CDR1as binds to miR-432-5p and plays a protective role in mitigating compression-induced NP cell apoptosis and ECM degradation by targeting SOX9. Circ-CDR1as may provide a novel therapeutic target for the clinical management of IDD in the future.

Can extracellular vesicles be considered as a potential frontier in the treatment of intervertebral disc disease?

As a global public health problem, low back pain (LBP) caused by intervertebral disc degeneration (IDD) seriously affects patients' quality of life. In addition, the prevalence of IDD tends to be younger, which brings a huge burden to individuals and society economically. Current treatments do not delay or reverse the progression of IDD. The emergence of biologic therapies has brought new hope for the treatment of IDD. Among them, extracellular vesicles (EVs), as nanoscale bioactive substances that mediate cellular communication, have now produced many surprising results in the research of the treatment of IDD. This article reviews the mechanisms and roles of EVs in delaying IDD and describes the prospects and challenges of EVs.

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.

MSC-Derived Exosomes Ameliorate Intervertebral Disc Degeneration By Regulating the Keap1/Nrf2 Axis

Bone marrow mesenchymal stem cell derived exosomes (BMSC-exos) are a crucial means of intercellular communication and can regulate a range of biological processes by reducing inflammation, decreasing apoptosis and promoting tissue repair. The process of intervertebral disc degeneration (IVDD) is accompanied by increased reactive oxygen species (ROS) because of a decrease in the expression of Nrf2, a critical transcription factor that resists excessive ROS. Our study demonstrated that BMSC-exos decreased ROS production by inhibiting Keap1 and promoting Nrf2 expression, attenuating the apoptosis, inflammation, and degeneration of nucelus pulposus (NP) cells. BMSC-exos promoted an increase in Nrf2 and nuclear translocation, while NF-κB expression was downregulated during this process. Additionally, the expression of antioxidative proteins was elevated after treatment with BMSC-exos. In vivo, we found more NP tissue retention in the BMSC-exos-treated group, along with more expression of Nrf2 and antioxidant-related proteins. Our findings demonstrated for the first time that BMSC-exos could restore the down-regulated antioxidant response system in degenerating NP cells by modulating the Keap1/Nrf2 axis. BMSC-exos could be used as an immediate ROS modulator in the treatment of intervertebral disc degeneration. When BMSC-exos were uptaken by NPCs, the expression of Keap1 decreased and this led to increased expression of Nrf2. Nuclear translocation of Nrf2 then promoted the synthesis of antioxidants against ROS and inhibited NF-kB signalling. Cellular inflammation, apoptosis, and ECM-related indicators were further reduced. Together, the process of IVDD was alleviated.

Extracellular Vesicle-Conjugated Functional Matrix Hydrogels Prevent Senescence by Exosomal miR-3594-5p-Targeted HIPK2/p53 Pathway for Disc Regeneration

Nucleus pulposus stem cells (NPSCs) senescence plays a critical role in the progression of intervertebral disc degeneration (IDD). Stem cell-derived extracellular vesicles (EV) alleviate cellular senescence. Whereas, the underlying mechanism remains unclear. Low stability largely limited the administration of EV in vivo. RGD, an arginine-glycine-aspartic acid tripeptide, strongly binds integrins expressed on the EV membranes, allowing RGD to anchor EV and prolong their bioavailability. An RGD-complexed nucleus pulposus matrix hydrogel (RGD-DNP) is developed to enhance the therapeutic effects of small EV (sEV). RGD-DNP prolonged sEV retention in vitro and ex vivo. sEV-RGD-DNP promoted NPSCs migration, decreased the number of SA-β-gal-positive cells, alleviated cell cycle arrest, and reduced p16, p21, and p53 activation. Small RNA-seq showed that miR-3594-5p is enriched in sEV, and targets the homeodomain-interacting protein kinase 2 (HIPK2)/p53 pathway. The HIPK2 knockdown rescues the impaired therapeutic effects of sEV with downregulated miR-3594-5p. RGD-DNP conjugate with lower amounts of sEV achieved similar disc regeneration with free sEV of higher concentrations in DNP. In conclusion, sEV-RGD-DNP increases sEV bioavailability and relieves NPSCs senescence by targeting the HIPK2/p53 pathway, thereby alleviating IDD. This work achieves better regenerative effects with fewer sEV and consolidates the theoretical basis for sEV application for IDD treatment.

Intervertebral disc degeneration-Current therapeutic options and challenges

Degeneration of the intervertebral disc (IVD) is a normal part of aging. Due to the spine's declining function and the development of pain, it may affect one's physical health, mental health, and socioeconomic status. Most of the intervertebral disc degeneration (IVDD) therapies today focus on the symptoms of low back pain rather than the underlying etiology or mechanical function of the disc. The deteriorated disc is typically not restored by conservative or surgical therapies that largely focus on correcting symptoms and structural abnormalities. To enhance the clinical outcome and the quality of life of a patient, several therapeutic modalities have been created. In this review, we discuss genetic and environmental causes of IVDD and describe promising modern endogenous and exogenous therapeutic approaches including their applicability and relevance to the degeneration process.

EIF4A3-Induced Exosomal circLRRC8A Alleviates Granulosa Cells Senescence Via the miR-125a-3p/NFE2L1 axis

Premature ovarian failure (POF) is an important cause of female infertility and seriously impacts the physical and psychological health of patients. Mesenchymal stromal cells-derived exosomes (MSCs-Exos) have an essential role in the treatment of reproductive disorders, particularly POF. However, the biological function and therapeutic mechanism of MSCs exosomal circRNAs in POF remain to be determined. Here, with bioinformatics analysis and functional assays, circLRRC8A was found to be downregulated in senescent granulosa cells (GCs) and acted as a crucial factor in MSCs-Exos for oxidative damage protection and anti-senescence of GCs in vitro and in vivo. Mechanistic investigations revealed that circLRRC8A served as an endogenous miR-125a-3p sponge to downregulate NFE2L1 expression. Moreover, eukaryotic initiation factor 4A3 (EIF4A3), acting as a pre-mRNA splicing factor, promoted circLRRC8A cyclization and expression by directly binding to the LRRC8A mRNA transcript. Notably, EIF4A3 silencing reduced circLRRC8A expression and attenuated the therapeutic effect of MSCs-Exos on oxidatively damaged GCs. This study demonstrates a new therapeutic pathway for cellular senescence protection against oxidative damage by delivering circLRRC8A-enriched exosomes through the circLRRC8A/miR-125a-3p/NFE2L1 axis and paves the way for the establishment of a cell-free therapeutic approach for POF. CircLRRC8A may be a promising circulating biomarker for diagnosis and prognosis and an exceptional candidate for further therapeutic exploration.

Intervertebral disc degeneration and osteoarthritis: a common molecular disease spectrum

Intervertebral disc degeneration (IDD) and osteoarthritis (OA) affecting the facet joint of the spine are biomechanically interdependent, typically occur in tandem, and have considerable epidemiological and pathophysiological overlap. Historically, the distinctions between these degenerative diseases have been emphasized. Therefore, research in the two fields often occurs independently without adequate consideration of the co-dependence of the two sites, which reside within the same functional spinal unit. Emerging evidence from animal models of spine degeneration highlight the interdependence of IDD and facet joint OA, warranting a review of the parallels between these two degenerative phenomena for the benefit of both clinicians and research scientists. This Review discusses the pathophysiological aspects of IDD and OA, with an emphasis on tissue, cellular and molecular pathways of degeneration. Although the intervertebral disc and synovial facet joint are biologically distinct structures that are amenable to reductive scientific consideration, substantial overlap exists between the molecular pathways and processes of degeneration (including cartilage destruction, extracellular matrix degeneration and osteophyte formation) that occur at these sites. Thus, researchers, clinicians, advocates and policy-makers should consider viewing the burden and management of spinal degeneration holistically as part of the OA disease continuum.

[Advances in the role of extracellular vesicles in intervertebral disc degeneration]

Objective

To review the mechanism of extracellular vesicles (EVs) in treating intervertebral disc degeneration (IVDD).

Methods

The literature about EVs was reviewed and the biological characteristics and mechanism of EVs in the treatment of IVDD were summarized.

Results

EVs are a kind of nano-sized vesicles with a double-layered lipid membrane structure secreted by many types of cells. EVs contain many bioactive molecules and participate in the exchange of information between cells, thus they play important roles in inflammation, oxidative stress, senescence, apoptosis, and autophagy. Moreover, EVs are found to slow down the process of IVDD by delaying the pathological progression of the nucleus pulposus, cartilage endplates, and annulus fibrosus.

Conclusion

EVs is expected to become a new strategy for the treatment of IVDD, but the specific mechanism remains to be further studied.

Sulforaphane Delays Intervertebral Disc Degeneration by Alleviating Endoplasmic Reticulum Stress in Nucleus Pulposus Cells via Activating Nrf-2/HO-1

Intervertebral disc degeneration (IVDD) is one of the main causes of low back pain, which brings heavy burdens to individuals and society. The mechanism of IVDD is complex and diverse. One of the important reasons is that the abnormal accumulation of reactive oxygen species (ROS) in nucleus pulposus cells (NPCs) leads to endoplasmic reticulum stress (ERS), which causes increased apoptosis of NPCs. Nuclear factor E2-related factor 2 (Nrf-2) and its downstream antioxidant proteins are key molecular switches for sensing oxidative stress and regulating antioxidant responses in cells. Sulforaphane (SFN), a natural compound derived from Brassicaceae plants, is a Nrf-2 agonist that displays potent antioxidant potential in vitro and in vivo. Here, we used advanced glycation end products (AGEs) to construct an in vitro degeneration model of NPCs, and we found that AGEs elevated ROS level in NPCs and caused severe ERS and apoptosis. While SFN can promote the entry of Nrf-2 into the nucleus and increase the expression level of heme oxygenase 1 (HO-1) in vitro, thus clearing the accumulated ROS in cells and alleviating ERS and cell apoptosis. Moreover, the protection of SFN on NPCs was greatly attenuated after HO-1 was inhibited. We also used AGEs to construct a rat IVDD model. Consistent with the in vitro experiments, SFN could attenuate ERS in NPCs in vivo and delay disc degeneration in rats. This study found that SFN can be used as a new and promising agent for the treatment of IVDD.

Exosome-derived circTFDP2 promotes prostate cancer progression by preventing PARP1 from caspase-3-dependent cleavage

BACKGROUND

Circular RNAs (circRNAs) have been reported to play a significant role in tumorigenesis. However, the detailed function of circRNA in prostate cancer (PCa) is still largely unknown.

METHODS

We quantified circTFDP2 expression in PCa tissues and adjacent normal tissues using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Colony formation, Cell Counting Kit-8 (CCK-8), flow cytometry, transwell, and in vivo progression and metastasis assays were applied to reveal the proliferation and metastatic abilities of circTFDP2 in PCa cells. Mass spectrometry, RNA pulldown, RNA-immunoprecipitation (RIP), western blotting and immunofluorescence were used for the mechanistic studies. qRT-PCR and RIP assays were used to explore the regulatory role of eIF4A3 in the biogenesis of circTFDP2. Finally, functional assays showed the effect of circTFDP2-containing exosomes on PCa cell progression.

RESULTS

circTFDP2 was upregulated in PCa tissues compared with adjacent normal tissues. Furthermore, high circTFDP2 expression was positively correlated with the Gleason score. Functionally, circTFDP2 promoted PCa cell proliferation and metastasis both in vivo and in vitro. Mechanistically, circTFDP2 interacted with poly(ADP-ribose) polymerase 1 (PARP1) protein in its DNA-binding domain to prevent it from active caspase-3-dependent cleavage, and finally relieved PCa cells from DNA damage. In addition, RNA-binding protein eIF4A3 can interact with the flanking region of circTFDP2 and promote the biogenesis of circTFDP2. Moreover, exosome-derived circTFDP2 promoted PCa cell progression.

CONCLUSIONS

In general, our study demonstrated that circTFDP2 promoted PCa cell progression through the PARP1/DNA damage axis, which may be a promising therapeutic target for PCa.

Bone Marrow Mesenchymal Stem Cell-Derived Extracellular Vesicles Carrying circ_0050205 Attenuate Intervertebral Disc Degeneration

Objective

It has been reported that bone marrow mesenchymal stem cells (BMSCs) are a potential source of autologous stem cells to support the nucleus pulposus (NP) regeneration in intervertebral disc degeneration (IDD). Herein, we aim to study the mechanism underlying the effects of BMSC-derived extracellular vesicles (BMSC-EVs) on nucleus pulposus cells (NPCs) in IDD.

Methods

EVs were isolated from BMSCs. An IDD model was surgically established in C57BL/6J mice. NPCs were exposed to tBHP to establish an IDD cell model. RNA sequencing was performed to identify differentially expressed circRNAs in NP tissues harvested from mice with IDD. Interactions among circ_0050205, miR-665, and GPX4 were validated, and different interventions were used to study the roles of these molecules in NPC biological functions.

Results

BMSC-EVs promoted NPC survival and inhibited NPC apoptosis and extracellular matrix (ECM) degradation. circ_0050205 expression was downregulated in the NP tissues of IDD mice, and BMSC-EVs facilitated NPC survival and suppressed ECM degradation in NPCs by transferring circ_0050205. circ_0050205 sponged miR-665 and upregulated GPX4 expression. BMSC-EVs expressing circ_0050205 promoted NPC survival-inhibited ECM degradation in NPCs and alleviated IDD in mice via the miR-665/GPX4 axis.

Conclusion

In conclusion, BMSC-EVs promoted NPC survival-inhibited ECM degradation in NPCs and attenuated IDD progression via the circ_0050205/miR-665/GPX4 axis.

circ_0072464 Shuttled by Bone Mesenchymal Stem Cell-Secreted Extracellular Vesicles Inhibits Nucleus Pulposus Cell Ferroptosis to Relieve Intervertebral Disc Degeneration

Ferroptosis, as an iron-dependent form of necrotic cell death, has been reported to affect activities of nucleus pulposus cells (NPCs). However, its role in the pathogenesis of intervertebral disc degeneration (IDD) is largely unknown. Notably, our bioinformatics analysis predicted that circ_0072464 was downregulated in nucleus pulposus of IDD mice. Therefore, this study is aimed at clarifying the mechanisms of extracellular vesicle- (EV-) encapsulated circ_0072464 derived from bone marrow mesenchymal stem cells (BMSCs) in NPC ferroptosis in IDD. EVs were extracted from mouse BMSCs (BMSC-EVs) and then cocultured with IL-1β-induced NPCs, followed by detection of matrix synthesis, proliferation, and ferroptosis of NPCs based on gain- or loss-of-function experiments. It was found that the uptake of BMSC-EVs by NPCs alleviated IDD. circ_0072464 and NRF2 were downregulated, and miR-431 was upregulated in IDD. Mechanistically, circ_0072464 competitively bound to miR-431, which targeted and inhibited NRF2 expression. BMSC-derived EVs carrying circ_0072464 inhibited NPC ferroptosis to promote matrix synthesis and proliferation of NPCs by inhibiting miR-431 and upregulating NRF2. Besides, in vivo experiments also confirmed that BMSC-EVs alleviated intervertebral disc lesions in mice with IDD through the circ_0072464/miR-431/NRF2 axis. Collectively, BMSC-EV-loaded circ_0072464 inhibited NPC ferroptosis to relieve IDD via upregulation of miR-431-mediated NRF2, therefore providing a potential therapeutic target against IDD.

Platelet-rich plasma-derived exosomes attenuate intervertebral disc degeneration by promoting NLRP3 autophagic degradation in macrophages

Intervertebral disc degeneration (IDD) is a common orthopedic multifactorial disease associated with spine-related disorders, such as low back pain. Recent studies have shown that both platelet-rich plasma (PRP) and exosomes could be used to treat IDD, but the effects and mechanism of PRP-derived exosomes in the treatment of IDD are still unclear. This study showed that PRP-derived exosomes inhibited the polarization of M1 macrophages by regulating the NF-κB and MAPK pathways and affected the polarization of M2 macrophages by regulating STAT6 phosphorylation. Additionally, PRP-derived exosomes promoted the autophagic degradation of NLRP3 by increasing NLRP3 ubiquitination and reducing IL-1β and Caspase-1 production. Moreover, PRP-derived exosomes could reduce IL-1β-induced apoptosis of nucleus pulposus cells. Lastly, in vivo experiments confirmed that PRP-derived exosomes reduced the expression of inflammatory mediators and apoptotic factors, which could thereby alleviate the progression of IDD. Taken together, these data showed that PRP-derived exosomes could alleviate the IDD-associated inflammation by regulating the ubiquitination and autophagic degradation of NLRP3 inflammasome, providing new insights into the treatment of IDD.

CircCDK14 ameliorates interleukin-1β-induced chondrocyte damage by the miR-1183/KLF5 pathway in osteoarthritis

BACKGROUND

The pathogenesis of osteoarthritis (OA), an endemic and debilitating disease, remains unclear. The study aimed to reveal the role of circular RNA cyclin dependent kinase 14 (circCDK14) in OA development and the underlying mechanism.

METHODS

Human chondrocytes were stimulated by 10 ng/mL interleukin-1β (IL-1β) to mimic OA cell model. The RNA expression of circCDK14, microRNA-1183 (miR-1183) and kruppel like factor 5 (KLF5) was checked through quantitative real-time polymerase chain reaction. Western blot was employed to detect protein expression. Cell viability, proliferation and apoptosis were investigated by cell counting kit-8, 5-Ethynyl-29-deoxyuridine and flow cytometry analysis, respectively. Starbase online database was performed to identify the interaction between miR-1183 and circCDK14 or KLF5. Exosomes were isolated by differential centrifugation and identified by transmission electron microscopy, nanoparticle tracking analysis and western blot analysis.

RESULTS

CircCDK14 and KLF5 expression were significantly decreased, while miR-1183 was increased in OA cartilage tissues and IL-1β-treated chondrocytes in comparison with controls. CircCDK14 overexpression attenuated the inhibitory effect of IL-1β treatment on cell proliferation and the promoting effects on cell apoptosis and extracellular matrix degradation. Additionally, miR-1183 was targeted by circCDK14, and miR-1183 mimics reversed circCDK14-mediated actions in IL-1β-treated chondrocytes. The knockdown of KLF5, a target mRNA of miR-1183, also rescued the effects of miR-1183 inhibitors in IL-1β-induced chondrocytes. Moreover, circCDK14 could induce KLF5 expression by interacting with miR-1183. Further, exosomal circCDK14 had a high diagnostic value in OA.

CONCLUSION

CircCDK14 reintroduction assuaged IL-1β-caused chondrocyte damage by the miR-1183/KLF5 pathway, providing a diagnostic biomarker for OA.

CircSLC8A1 Exacerbates Hypoxia-Induced Myocardial Injury via Interacting with MiR-214-5p to Upregulate TEAD1 Expression

Circular RNAs (circRNAs) act as important regulators in myocardial infarction (MI). This study aimed to explore the regulatory mechanism of circRNA solute carrier family 8 member A1 antisense RNA 1 (circSLC8A1) in hypoxia-induced myocardial injury.Exosomes were isolated by ultracentrifugation and identified by microscopic observation or protein detection. Protein levels were examined by Western blot. CircSLC8A1, microRNA-214-5p (miR-214-5p), and TEA domain transcription factor 1 (TEAD1) levels were determined via quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability and apoptosis were analyzed by 3-(4,5-dimethylthiazol-2-y1)-2,5-diphenyl tetrazolium bromide (MTT) and flow cytometry, respectively. Inflammatory cytokines were measured using enzyme-linked immunosorbent assay (ELISA). Oxidative stress was assessed by reactive oxygen species (ROS) production, malondialdehyde (MDA) level, and superoxide dismutase (SOD) activity through the corresponding detection kits. Target analysis was performed by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, and pull-down assay.Exosomes released circSLC8A1 from hypoxic cardiomyocytes. Exosomal circSLC8A1 exacerbated hypoxia-induced repression of cell viability but promotion of cell apoptosis, inflammation, and oxidative stress. Knockdown of circSLC8A1 ameliorated hypoxia-mediated cell injury. CircSLC8A1 directly targeted miR-214-5p and miR-214-5p downregulation reverted the effects of si-circSLC8A1 on hypoxia-treated cardiomyocytes. TEAD1 was a target of miR-214-5p and circSLC8A1 upregulated TEAD1 level via targeting miR-214-5p. In addition, miR-214-5p inhibited hypoxia-caused cell injury by downregulating the expression of TEAD1.These results suggested that circSLC8A1 aggravated cell damages in hypoxia-treated cardiomyocytes by the regulation of TEAD1 via sponging miR-214-5p.

Circular RNAs and Their Role in Exosomes

As a novel class of endogenous non-coding RNAs discovered in recent years, circular RNAs (circRNAs) are highly conserved and stable covalently closed ring structures with no 5'-end cap or 3'-end poly(A) tail. CircRNAs are formed by reverse splicing, mainly by means of a noose structure or intron complementary pairing. Exosomes are tiny discoid vesicles with a diameter of 40-100 nm that are secreted by cells under physiological and pathological conditions. Exosomes play an important role in cell-cell communication by carrying DNA, microRNAs, mRNAs, proteins and circRNAs. In this review, we summarize the biological functions of circRNAs and exosomes, and further reveal the potential roles of exosomal circRNAs in different diseases, providing a scientific basis for the diagnosis, treatment, and prognosis of a wide variety of diseases.

Extracellular Vesicles as an Emerging Treatment Option for Intervertebral Disc Degeneration: Therapeutic Potential, Translational Pathways, and Regulatory Considerations

Emergent approaches in regenerative medicine look toward the use of extracellular vesicles (EVs) as a next-generation treatment strategy for intervertebral disc (IVD) degeneration (IVDD) because of their ability to attenuate chronic inflammation, reduce apoptosis, and stimulate proliferation in a number of tissue systems. Yet, there are no Food and Drug Administration (FDA)-approved EV therapeutics in the market with an indication for IVDD, which motivates this article to review the current state of the field and provide an IVD-specific framework to assess its efficacy. In this systematic review, 29 preclinical studies that investigate EVs in relation to the IVD are identified, and additionally, the regulatory approval process is reviewed in an effort to accelerate emerging EV-based therapeutics toward FDA submission and timeline-to-market. The majority of studies focus on nucleus pulposus responses to EV treatment, where the main findings show that stem cell-derived EVs can decelerate the progression of IVDD on the molecular, cellular, and organ level. The findings also highlight the importance of the EV parent cell's pathophysiological and differentiation state, which affects downstream treatment responses and therapeutic outcomes. This systematic review substantiates the use of EVs as a promising cell-free strategy to treat IVDD and enhance endogenous repair.

Extracellular Circular RNAs Act as Novel First Messengers Mediating Cell Cross-Talk in Ischemic Cardiac Injury and Myocardial Remodeling

Myocardial infarction (MI) causes most of the mortality worldwide. Coronary obstruction-caused myocardial ischemic injury leads to permanent loss of the myocardium. Subsequent compensatory myocardial remodeling and heart failure would result in arrhythmia and even sudden death. The molecular mechanisms of these pathological processes remain to be thoroughly revealed. Circular RNAs (circRNAs) are special types of non-coding RNAs which can durably regulate gene expression and modulate cell fate. They had been reported to mediate ischemic myocardial injury and myocardial remodeling. circRNAs can be loaded into extracellular vesicles and released into extracellular space. More recently, it was uncovered that the extracellular circRNAs can regulate intercellular communications, similar to "first messengers." The cross-talk mediated by extracellular circRNAs had been demonstrated to play important roles in pathological processes. Here, we would like to review the modulation of extracellular circRNAs in ischemic myocardial injury and myocardial remodeling. We believe the extracellular circRNAs can bring new strategies of MI treatment.

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

Low back pain (LBP) is seriously harmful to human health and produces heavy economic burden. And most scholars hold that intervertebral disc degeneration (IDD) is the primary cause of LBP. With the study of IDD, aberrant expression of gene has become an important pathogenic factor of IDD. Circular RNAs (circRNAs), as a kind of noncoding RNA (ncRNA), participate in the regulation of genetic transcription and translation and further affect the expression of inflammatory cytokine, metabolism of extracellular matrix (ECM), the proliferation and apoptosis of cells, etc. Therefore, maybe it will become a new therapeutic target for IDD. At present, our understanding of the mechanism of circRNAs in IDD is limited. The purpose of this review is to summarize the mechanism and related signaling pathways of circRNAs in IDD reported in the past. Particularly, the roles of circRNAs in inflammation, ECM metabolism, and apoptosis are emphasized.

Exosomes Immunity Strategy: A Novel Approach for Ameliorating Intervertebral Disc Degeneration

Low back pain (LBP), which is one of the most severe medical and social problems globally, has affected nearly 80% of the population worldwide, and intervertebral disc degeneration (IDD) is a common musculoskeletal disorder that happens to be the primary trigger of LBP. The pathology of IDD is based on the impaired homeostasis of catabolism and anabolism in the extracellular matrix (ECM), uncontrolled activation of immunologic cascades, dysfunction, and loss of nucleus pulposus (NP) cells in addition to dynamic cellular and biochemical alterations in the microenvironment of intervertebral disc (IVD). Currently, the main therapeutic approach regarding IDD is surgical intervention, but it could not considerably cure IDD. Exosomes, extracellular vesicles with a diameter of 30–150 nm, are secreted by various kinds of cell types like stem cells, tumor cells, immune cells, and endothelial cells; the lipid bilayer of the exosomes protects them from ribonuclease degradation and helps improve their biological efficiency in recipient cells. Increasing lines of evidence have reported the promising applications of exosomes in immunological diseases, and regarded exosomes as a potential therapeutic source for IDD. This review focuses on clarifying novel therapies based on exosomes derived from different cell sources and the essential roles of exosomes in regulating IDD, especially the immunologic strategy.

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.

Circ_0022382 ameliorated intervertebral disc degeneration by regulating TGF-β3 expression through sponge adsorption of miR-4726-5p

Circular RNAs (circRNAs) participate in the progression of many diseases, but knowledge on the role of circRNAs in intervertebral disc degeneration (IDD) is limited. In this study, we discovered the characteristics of a new circRNA (circ_0022382) in human endplate chondrocytes. Currently, real-time quantitative polymerase chain reaction (RT-qPCR) showed that the relative expression level of circ_0022382 was significantly lower under intermittent cyclic tension stimulation than in the control group. circ_0022382, miR-4726-5p and Transforming growth factor 3 (TGF-β3) were evaluated by RT-qPCR, Western Blot and immunofluorescence assay. Additionally, the role and mechanism of circ_0022382 in vivo were also consistent in the rat model. Furthermore, Intermittent cyclic mechanical tension can cause degeneration of endplate chondrocytes. The tension-sensitive circRNA_0022382 was decreased, and we found that circRNA_0022382 promoted morphology of endplate chondrocytes by sponge-binding miR-4726-5p down-regulation of target gene the TGF-β3 expression, thereby alleviating IDD. In a rat model of acupuncture, intervertebral disc injection of circ_0022382 relieved the progression of IDD in vivo. In conclusion, the circ_0022382/miR-4726-5p/TGF-β3 axis plays a key role in the anabolism and catabolism of the endplate chondrocyte extracellular matrix (ECM). It is suggested that circ_0022382 may provide a new approach for the prevention and treatment of IDD.

Ferroptosis: A potential target for the intervention of intervertebral disc degeneration

Ferroptosis, an iron-dependent form of programmed cell death marked by phospholipid peroxidation, is regulated by complex cellular metabolic pathways including lipid metabolism, iron balance, redox homeostasis, and mitochondrial activity. Initial research regarding the mechanism of ferroptosis mainly focused on the solute carrier family 7 member 11/glutathione/glutathione peroxidase 4 (GPX4) signal pathway. Recently, novel mechanisms of ferroptosis, independent of GPX4, have been discovered. Numerous pathologies associated with extensive lipid peroxidation, such as drug-resistant cancers, ischemic organ injuries, and neurodegenerative diseases, are driven by ferroptosis. Ferroptosis is a new therapeutic target for the intervention of IVDD. The role of ferroptosis in the modulation of intervertebral disc degeneration (IVDD) is a significant topic of interest. This is a novel research topic, and research on the mechanisms of IVDD and ferroptosis is ongoing. Herein, we aim to review and discuss the literature to explore the mechanisms of ferroptosis, the relationship between IVDD and ferroptosis, and the regulatory networks in the cells of the nucleus pulposus, annulus fibrosus, and cartilage endplate to provide references for future basic research and clinical translation for IVDD treatment.

Exosomal circRNAs: Emerging Players in Tumor Metastasis

Metastasis is an important feature of malignant tumors, and is the primary cause of poor prognosis and treatment failure, in addition to representing a potentially fatal challenge for cancer patients. Exosomes are small extracellular vesicles 30–150 nm in diameter that transmit cargo, such as DNA, RNA, and proteins, as a means of intercellular communication. Exosomes play crucial roles in a range of human diseases, especially malignant tumors. A growing number of studies have verified that circRNAs can be enveloped in exosomes and transferred from secretory cells to recipient cells, thereby regulating tumor progression, especially tumor metastasis. Exosomal circRNAs regulate tumor cell metastasis not only by regulating the signaling pathways, but also by affecting the tumor microenvironment. Moreover, exosomal circRNAs have the potential to serve as valuable diagnostic biomarkers and novel therapeutic targets in cancer patients. In this review, we summarize the mechanism by which exosomal circRNAs modulate metastatic phenomena in various types of tumors, and put forward the prospects of clinical applications of exosomal circRNAs in tumor therapy.

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.

Construction of a Potentially Functional circRNA-miRNA-mRNA Network in Intervertebral Disc Degeneration by Bioinformatics Analysis

Background

The competing endogenous RNA- (ceRNA-) mediated regulatory mechanisms are known to play a pivotal role in intervertebral disc degeneration (IDD). Our research intended to establish a ceRNA regulatory network related to IDD through bioinformatics analyses.

Methods

The expression profiles of circRNA, miRNA, and mRNA were obtained from the public Gene Expression Omnibus (GEO) datasets. Then, we use sequence-based bioinformatics methods to select differentially expressed mRNAs (DEmRNAs), microRNAs (DEmiRNAs), or circRNAs (DEcircRNAs) related to IDD. We used ChEA3 to verify the targets of transcription factors (TFs). Then, we used DAVID to annotate the DEmRNAs. Finally, we constructed a potentially circRNA-miRNA-mRNA network related to IDD by predicting in the database (ENCORI, TargetScan, miRecords, miRmap, and circBank).

Results

We identified 31 common DEmRNAs by Venn analysis, of which MMP2 was regarded as the key hub genes. Simultaneously, miR-423-5p and miR-185-5p were predicted as the upstream molecules of MMP2. Furthermore, a total of six DEcircRNAs were predicted as the upstream circRNAs of miR-423-5p and miR-185-5p. Then, a potential circRNA-miRNA-mRNA network related to IDD was constructed by bioinformatics analysis.

Conclusion

A comprehensive ceRNA regulatory network was constructed, which was found to be significant in IDD progression.

Intervertebral Disk Degeneration: The Microenvironment and Tissue Engineering Strategies

Intervertebral disk degeneration (IVDD) is a leading cause of disability. The degeneration is inevitable, and the mechanisms are complex. Current therapeutic strategies mainly focus on the relief of symptoms, not the intrinsic regeneration of the intervertebral disk (IVD). Tissue engineering is a promising strategy for IVDD due to its ability to restore a healthy microenvironment and promote IVD regeneration. This review briefly summarizes the IVD anatomy and composition and then sets out elements of the microenvironment and the interactions. We rationalized different scaffolds based on tissue engineering strategies used recently. To fulfill the complete restoration of a healthy IVD microenvironment, we propose that various tissue engineering strategies should be combined and customized to create personalized therapeutic strategies for each individual.

Exosome-transported circRNA_0001236 enhances chondrogenesis and suppress cartilage degradation via the miR-3677-3p/Sox9 axis

Objectives

Aberrations in exosomal circular RNA (circRNA) expression have been identified in various human diseases. In this study, we investigated whether exosomal circRNAs could act as competing endogenous RNAs (ceRNAs) to regulate the pathological process of osteoarthritis (OA). This study aimed to elucidate the specific MSC-derived exosomal circRNAs responsible for MSC-mediated chondrogenic differentiation using human bone marrow-derived MSCs (hMSCs) and a destabilization of the medial meniscus (DMM) mouse model of OA.

Methods

Exosomal circRNA deep sequencing was performed to evaluate the expression of circRNAs in human bone marrow-derived MSCs (hMSCs) induced to undergo chondrogenesis from day 0 to day 21. The regulatory and functional roles of exosomal circRNA_0001236 were examined on day 21 after inducing chondrogenesis in hMSCs and were validated in vitro and in vivo. The downstream target of circRNA_0001236 was also explored in vitro and in vivo using bioinformatics analyses. A luciferase reporter assay was used to evaluate the interaction between circRNA_0001236 and miR-3677-3p as well as the target gene sex-determining region Y-box 9 (Sox9). The function and mechanism of exosomal circRNA_0001236 in OA were explored in the DMM mouse model.

Results

Upregulation of exosomal circRNA_0001236 enhanced the expression of Col2a1 and Sox9 but inhibited that of MMP13 in hMSCs induced to undergo chondrogenesis. Moreover, circRNA_0001236 acted as an miR-3677-3p sponge and functioned in human chondrocytes via targeting miR-3677-3p and Sox9. Intra-articular injection of exosomal circRNA_0001236 attenuated OA in the DMM mouse model.

Conclusions

Our results reveal an important role for a novel exosomal circRNA_0001236 in chondrogenic differentiation. Overexpression of exosomal circRNA_0001236 promoted cartilage-specific gene and protein expression through the miR-3677-3p/Sox9 axis. Thus, circRNA_0001236-overexpressing exosomes may alleviate cartilage degradation, suppressing OA progression and enhancing cartilage repair. Our findings provide a potentially effective therapeutic strategy for treating OA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02431-5.

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.

Circular RNAs and Cardiovascular Regeneration

circular RNAs (circRNAs) are a type of non-coding RNAs that are widely present in eukaryotic cells. They have the characteristics of stable structure, high abundance, and cell or tissue specific expression. circRNAs are single-stranded RNAs that are covalently back spliced to form closed circular loops. They may participate in gene expression and regulation through a variety of action modes. circRNAs can encode proteins or function by acting as miRNA sponges for protein translation. Since 2016, a growing number of research studies have shown that circRNAs play important role in the pathogenesis of cardiovascular disease. With the construction of circRNA database, the differential expression of circRNAs in the heart tissue samples from different species and the gradual elucidation of its mode of action in disease may become an ideal diagnosis biomarker and an effective therapeutic target. What can be expected surely has a broader application prospect. In this review, we summarize recent publications on circRNA biogenesis, expression profiles, functions, and the most recent studies of circRNAs in the field of cardiovascular diseases with special emphasis on cardiac regeneration.

Power and promise of exosomes as clinical biomarkers and therapeutic vectors for liquid biopsy and cancer control

Exosomes, microvesicles derived from the nuclear endosome and plasma membrane, can be released into the extracellular environment to act as mediators between the cell membrane and cytoplasmic proteins, lipids, or RNA. Exosomes are considered effective carriers of intercellular signals in prokaryotes and eukaryotes, because of their ability to efficiently transfer proteins, lipids, and nucleic acids between cellular compartments. Since the 2007 discovery that exosomes carry bioactive substances, exosomes have been intensively researched. In various physiological and pathological processes, exosomes play important biological roles by specifically combining with receptor cells and transmitting information. Their stable biological characteristics, diversity of contents, non-invasiveness path for introducing signaling molecules, and ability for rapid detection make exosomes a promising clinical diagnostic marker for potentially many pathological conditions, including cancers. Exosomes are not only considered biomarkers and prognostic disease factors, but also have potential as gene carriers and drug delivery vectors, and have important clinical significance and application potential in the fields of cancer diagnosis, prognosis, and treatment.

Cyclic RNA Circ_0000735 sponges miR-502-5p to promote bladder cancer cell proliferation and invasion and inhibit apoptosis

OBJECTIVE

The objective of this study was to investigate the effect on the proliferation, invasion, and apoptosis of bladder cancer cells through miR-502-5p of the Circ_0000735 circular RNA.

METHODS

Circ_0000735 and miR-502-5p expression of bladder cancer patients in malignant and paracancerous tissues was identified using qRT-PCR. Nucleoplasm isolation assay and RNase R enzymatic assay were used to classify Circ_0000735 subcellular origin and stability. Dual luciferase reporter assay and RIP assay were used to confirm Circ_0000735 and miR-502-5p targeting relationships. Cell proliferation, apoptosis, and invasion capacity were identified using CCK8, flow cytometry, and transwell assays. To confirm the effect of Circ_0000735 on tumorigenesis in nude mice, in vivo experiments were conducted.

RESULTS

Circ_0000735 expression was increased in bladder cancer tissues and cells compared with paraneoplastic tissues and normal cells, and miR-502-5p expression was reduced (both P<0.05). In the cytoplasm, Circ_0000735 was largely clustered and could not be digested by the RNase R enzyme, and ceRNA may play a role in bladder cancer cells. Circ_0000735 silencing prevented cell proliferation and invasion and facilitated apoptosis (all P<0.05). The incorporation of miR-502-5p inhibitor rescued the effect on bladder cancer cells of Circ_0000735 silencing. In vitro experiments showed that inhibition of Circ_0000735 expression was beneficial in suppressing tumorigenic ability in nude mice.

CONCLUSION

Circ_0000735 can adsorb miR-502-5p to promote bladder cancer cell proliferation and invasion and inhibit apoptosis. Circ_0000735 may be an effective molecular target for bladder cancer therapy.