MicroRNA-30a promotes extracellular matrix degradation in articular cartilage via downregulation of Sox9

COTE-1 promotes the proliferation and invasion of small cell lung cancer by regulating autophagy activity via the AMPK/mTOR signaling pathway

BACKGROUND

COTE-1 has been found to promote the proliferation and invasion of non-small cell lung cancer. However, the mechanism of COTE-1 in SCLC is still unclear. Exploring the role of COTE-1 in SCLC is expected to provide a potential target for the prognosis and treatment of SCLC.

METHODS

The expression of COTE-1 and ki-67 was detected by immunohistochemical staining. PCR detected COTE-1 expression level. Cell proliferation activity was detected by CCK8 assay. A wound healing test detected cell migrative ability. Transwell invasion assay detected cell invasive ability. The numbers of autophagosomes were observed by transmission electron microscopy. WB detected the expression levels of autophagy-related proteins and AMPK/mTOR pathway-related proteins. The effect of COTE-1 expression level on the proliferation of SCLC tumor tissues was investigated by establishing a mouse SCLC xenograft tumor model.

RESULTS

The expression of COTE-1 in SCLC tissues and cells was higher than that in normal tissues and cells. In SCLC cells with high COTE-1 expression, the expression level of autophagy proteins was notably increased, the number of intracellular autophagosomes increased, and the proliferative activity, migration and invasion abilities were enhanced. COTE-1 promotes autophagy, proliferation, and invasion of SCLC cells under nutrient deprivation by activating the AMPK/mTOR signaling pathway. Activation of autophagy by COTE-1 promotes the proliferation and development of xenograft tumors in a mouse model of SCLC.

CONCLUSION

COTE-1 promotes the proliferation, migration and invasion of small cell lung cancer by mediating autophagy based on the AMPK/mTOR pathway.

Exploring the Feasibility of Circulating miRNAs as Diagnostic and Prognostic Biomarkers in Osteoarthritis: Challenges and Opportunities

Osteoarthritis (OA) is a prevalent degenerative joint disease characterized by progressive cartilage degradation and joint inflammation. As the most common aging-related joint disease, OA is marked by inadequate extracellular matrix synthesis and the breakdown of articular cartilage. However, traditional diagnostic methods for OA, relying on clinical assessments and radiographic imaging, often need to catch up in detecting early-stage disease or i accurately predicting its progression. Consequently, there is a growing interest in identifying reliable biomarkers that can facilitate early diagnosis and prognosis of OA. MicroRNAs (miRNAs) have emerged as potential candidates due to their involvement in various cellular processes, including cartilage homeostasis and inflammation. This review explores the feasibility of circulating miRNAs as diagnostic and prognostic biomarkers in OA, focusing on knee OA while shedding light on the challenges and opportunities associated with their implementation in clinical practice.

MicroRNA Signatures in Cartilage Ageing and Osteoarthritis

Osteoarthritis is the most common degenerative joint disorder. MicroRNAs are gene expression regulators that act post-transcriptionally to control tissue homeostasis. Microarray analysis was undertaken in osteoarthritic intact, lesioned and young intact cartilage. Principal component analysis showed that young intact cartilage samples were clustered together; osteoarthritic samples had a wider distribution; and osteoarthritic intact samples were separated into two subgroups, osteoarthritic-Intact-1 and osteoarthritic-Intact-2. We identified 318 differentially expressed microRNAs between young intact and osteoarthritic lesioned cartilage, 477 between young intact and osteoarthritic-Intact-1 cartilage and 332 between young intact and osteoarthritic-Intact-2 cartilage samples. For a selected list of differentially expressed microRNAs, results were verified in additional cartilage samples using qPCR. Of the validated DE microRNAs, four-miR-107, miR-143-3p, miR-361-5p and miR-379-5p-were selected for further experiments in human primary chondrocytes treated with IL-1β. Expression of these microRNAs decreased in human primary chondrocytes treated with IL-1β. For miR-107 and miR-143-3p, gain- and loss-of-function approaches were undertaken and associated target genes and molecular pathways were investigated using qPCR and mass spectrometry proteomics. Analyses showed that WNT4 and IHH, predicted targets of miR-107, had increased expression in osteoarthritic cartilage compared to young intact cartilage and in primary chondrocytes treated with miR-107 inhibitor, and decreased expression in primary chondrocytes treated with miR-107 mimic, suggesting a role of miR-107 in chondrocyte survival and proliferation. In addition, we identified an association between miR-143-3p and EIF2 signalling and cell survival. Our work supports the role of miR-107 and miR-143-3p in important chondrocyte mechanisms regulating proliferation, hypertrophy and protein translation.

Engineering exosomes by three-dimensional porous scaffold culture of human umbilical cord mesenchymal stem cells promote osteochondral repair

Improving the poor microenvironment in the joint cavity has potential for treating cartilage injury, and mesenchymal stem cell (MSC)-derived exosomes (MSC-Exos), which can modulate cellular behavior, are becoming a new cell-free therapy for cartilage repair. Here, we used acellular cartilage extracellular matrix (ACECM) to prepare 3D scaffolds and 2D substrates by low-temperature deposition modeling (LDM) and tape casting. We aimed to investigate whether MSC-Exos cultured on scaffolds of different dimensions could improve the poor joint cavity microenvironment caused by cartilage injury and to explore the related mechanisms. In vitro experiments showed that exosomes derived from MSCs cultured on three-dimensional (3D) scaffolds (3D-Exos) had increased efficiency. In short-term animal experiments, compared with exosomes derived from MSCs cultured in a two-dimensional (2D) environment (2D-Exos), 3D-Exos had a stronger ability to regulate the joint cavity microenvironment. Long-term animal studies confirmed the therapeutic efficacy of 3D-Exos over 2D-Exos. Thus, 3D-Exos were applied in the rat knee osteochondral defect model after adsorption in the micropores of the scaffold and combined with subsequent articular cavity injections, and they showed a stronger cartilage repair ability. These findings provide a new strategy for repairing articular cartilage damage. Furthermore, miRNA sequencing indicated that the function of 3D-Exos may be associated with high expression of miRNAs. Thus, our study provides valuable insights for the design of 3D-Exos to promote cartilage regeneration.

Circular RNA from phosphodiesterase 4D can attenuate chondrocyte apoptosis and matrix degradation under OA milieu induced by IL-1β via circPDE4D/miR-4306/SOX9 cascade

BACKGROUND

Phosphodiesterase 4D (PDE4D) is a novel molecular therapeutic agent for human diseases, including Alzheimer's disease, ischemic stroke, asthma and cancers. Circular RNA from PDE4D (circPDE4D; ID hsa_circ_0072568) was one of the most downregulated circRNAs in OA patients. However, its precise role in OA-related chondrocytes was largely unknown.

METHODS

Expressions of circPDE4D, microRNA (miR)-4306 and sex-determining region Y-box 9 (SOX9) were measured by quantitative real-time PCR; protein levels of SOX9 and proteins related to apoptosis and extracellular matrix (ECM) were detected by western blotting. Cell apoptosis was assessed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, 5-ethynyl-2'-deoxyuridine and Annexin V-fluorescein isothiocyanate apoptosis assays. MiR-4306 response elements were predicted by bioinformatics algorithm and identified using dual-luciferase reporter, RNA immunoprecipitation and biotin-coupled miRNA capture assays.

RESULTS

CircPDE4D was markedly downregulated in OA cartilages and interleukin (IL)-1β-stressed human normal chondrocytes (HNC). Ectopic expression of circPDE4D rescued cell viability, proliferation, and expressions of B-cell lymphoma/leukemia-2 (Bcl-2) and Collagen type II α1 in IL-1β-insulted HNC, and meanwhile declined apoptosis rate and levels of Bcl-2-associated X protein, cleaved caspase-3, cleaved poly (ADP-ribose) polymerase-1, matrix metalloproteinase-13, ADAM metallopeptidase with thrombospondin type 1 motif 5, IL-6, and IL-8. CircPDE4D and SOX9 were competing endogenous RNAs (ceRNAs) for miR-4306, and circPDE4D could positively regulate SOX9 expression via miR-4306.

CONCLUSION

CircPDE4D and miR-4306 were important regulators in regulating IL-1β-induced HNC apoptosis and matrix degradation via regulating the key transcription factor SOX9, suggesting a novel circPDE4D/miR-4306/SOX9 ceRNA pathway in OA-related chondrocyte dysfunction.

Crosstalk Among circRNA/lncRNA, miRNA, and mRNA in Osteoarthritis

Osteoarthritis (OA) is a joint disease that is pervasive in life, and the incidence and mortality of OA are increasing, causing many adverse effects on people's life. Therefore, it is very vital to identify new biomarkers and therapeutic targets in the clinical diagnosis and treatment of OA. ncRNA is a nonprotein-coding RNA that does not translate into proteins but participates in protein translation. At the RNA level, it can perform biological functions. Many studies have found that miRNA, lncRNA, and circRNA are closely related to the course of OA and play important regulatory roles in transcription, post-transcription, and post-translation, which can be used as biological targets for the prevention, diagnosis, and treatment of OA. In this review, we summarized and described the various roles of different types of miRNA, lncRNA, and circRNA in OA, the roles of different lncRNA/circRNA-miRNA-mRNA axis in OA, and the possible prospects of these ncRNAs in clinical application.

Sox9-Increased miR-322-5p Facilitates BMP2-Induced Chondrogenic Differentiation by Targeting Smad7 in Mesenchymal Stem Cells

Bone morphogenetic protein 2 (BMP2) induces effective chondrogenesis of mesenchymal stem cells (MSCs) by promoting Sox9 expression. However, BMP2 also induces chondrocyte hypertrophy and endochondral ossification by upregulating Smad7 expression, which leads to the disruption of chondrogenesis. In addition, Smad7 can be inhibited by Sox9. Therefore, the underlying mechanism is not clear. Currently, an increasing number of studies have shown that microRNAs play a pivotal role in chondrogenic and pathophysiological processes of cartilage. The purpose of this study was to determine which microRNA is increased by Sox9 and targets Smad7, thus assisting BMP2 in maintaining stable chondrogenesis. We found that miR-322-5p meets the requirement through next-generation sequencing (NGS) and bioinformatic analysis. The targeting relationship between miR-322-5p and Smad7 was confirmed by dual-luciferase reporter assays, qPCR, and western blotting (WB). The in vitro study indicated that overexpression of miR-322-5p significantly inhibited Smad7 expression, thus causing increased chondrogenic differentiation and decreased hypertrophic differentiation, while silencing of miR-322-5p led to the opposite results. Flow cytometry (FCM) analysis indicated that overexpression of miR-322-5p significantly decreased the rate of early apoptosis in BMP2-stimulated MSCs, while silencing of miR-322-5p increased the rate. A mouse limb explant assay revealed that the expression of miR-322-5p was negatively correlated with the length of the BMP2-stimulated hypertrophic zone of the growth plate. An in vivo study also confirmed that miR-322-5p assisted BMP2 in chondrogenic differentiation. Taken together, our results suggested that Sox9-increased miR-322-5p expression can promote BMP2-induced chondrogenesis by targeting Smad7, which can be exploited for effective tissue engineering of cartilage.

LINC00473 exacerbates osteoarthritis development by promoting chondrocyte apoptosis and proinflammatory cytokine production through the miR-424-5p/LY6E axis

Osteoarthritis (OA) is a common degenerative joint disease that has been identified as one of the major health burdens in aging individuals. Long non-coding RNAs (lncRNAs) participate in the development of diverse diseases, including OA. Among them, lncRNA long intergenic non-protein coding RNA 473 (LINC00473) is one of the few upregulated lncRNAs. The present study aimed to explore the role of LINC00473 and its regulatory mechanism in OA development. Flow cytometry analyses and ELISA were carried out to detect chondrocyte apoptosis and the concentration of proinflammatory cytokines, respectively. The results suggested that LINC00473 knockdown significantly reduced chondrocyte apoptosis and the production of proinflammatory cytokines in IL-1β-stimulated C28/I2 cells compared with transfection with small interfering RNA-negative control (si-NC). Western blot analyses were performed to examine protein levels of apoptotic markers (caspase-3, Bax and Bcl-2) in C28/I2 cells. Subsequently, an OA rat model was established to explore the role of LINC00473 in vivo. The results indicated that, compared with the OA + adeno-associated virus si-NC group, LINC00473 knockdown significantly suppressed the degradation of chondrocyte extracellular matrix and the production of proinflammatory cytokines in OA model rats. Furthermore, bioinformatics analysis, luciferase reporter and RNA immunoprecipitation assays indicated that LINC00473 served as a microRNA (miR)-424-5p sponge in C28/I2 cells, and that lymphocyte antigen 6 locus E (LY6E) was the downstream target. In addition, the inhibitory effects of LINC00473 knockdown on chondrocyte apoptosis and the inflammatory response could be reversed by LY6E overexpression in IL-1β-stimulated C28/I2 cells. In summary, the findings indicated that LINC00473 contributed to OA progression by modulating the miR-424-5p/LY6E axis, which may serve as a potential therapeutic strategy for patients with OA.

LINC00115 promotes stemness and inhibits apoptosis of ovarian cancer stem cells by upregulating SOX9 and inhibiting the Wnt/β-catenin pathway through competitively binding to microRNA-30a

OBJECTIVE

Long non-coding RNAs (lncRNAs) and microRNAs (miRs) are differentially expressed in ovarian cancer (OC) cells and influence OC progression. This study intended to explore the underlying roles of LINC00115 and miR-30a in OC.

METHODS

Gene Expression Omnibus database was used to find OC microarray datasets and bioinformatics analysis predicted the potential molecular mechanism of OC. OC stem cells (OCSCs) surface marker was isolated from human OC cell line and identified. CD133⁺ OCSCs were transfected with LINC00115, miR-30a and SOX9 alone or together to detect sphere-forming ability and apoptosis of OCSCs. Caspase-3 activity and DNA damage in cell supernatant were detected. The levels of CD44, NANOG, POU5F1, LINC00115, CD133, miR-30a and SOX9 were measured. Then sh-LNC00115-treated OCSCs were added with Wnt/β-catenin activator SKL2001 to observe the changes of cell stemness and activity. Finally, animal models were established to evaluate the effect of LINC00115 on OCSC in vivo.

RESULTS

LINC00115 and SOX9 were highly expressed in OC, while miR-30a was lowly expressed. After silencing LINC00115 or overexpressing miR-30a, the sphere-forming rate of CD133⁺ OCSC and levels of CD133, CD44, NANOG and POU5F1 decreased, while apoptotic rate, Caspase-3 activity and histone-related DNA damage increased. SOX9 reversed these trends. Additionally, LINC00115 could bind to miR-30a and miR-30a could target SOX9. SKL2001 partially reversed cell stemness and activity in sh-LNC00115-treated OCSCs. Finally, silencing LINC00115 could inhibit OCSCs growth in vivo.

CONCLUSION

LINC00115 promoted stemness and inhibited apoptosis of OCSCs by upregulating SOX9 and in activating the Wnt/β-catenin pathway through competitively binding to miR-30a.

The Fibroblast-Like Synoviocyte Derived Exosomal Long Non-coding RNA H19 Alleviates Osteoarthritis Progression Through the miR-106b-5p/TIMP2 Axis

Osteoarthritis (OA) is a common degenerative joint disease that affects people worldwide. The interaction between fibroblast-like synoviocytes (FLSs) and chondrocytes may play a vital role in OA disease pathology. However, the underlying mechanisms by which FLSs exert regulatory effects on chondrocytes still need to be elucidated. Exosomes, small membrane vesicles secreted from living cells, are known to play a variety of roles in mediating cell-to-cell communication through the transferring of biological components such as non-coding RNAs and proteins. Here, we investigate the cellular processes of chondrocytes regulated by FLS-derived exosomes and the mechanisms of action underlying the functions of exosomes in OA pathogenesis. We observed that exosome-mediated cartilage repair was characterized by increased cell viability and migration as well as alleviated matrix degradation. Using chondrocyte cultures, the enhanced cellular proliferation and migration during exosome-mediated cartilage repair was linked to the exosomal lncRNA H19-mediated regulation of the miR-106b-5p/TIMP2 axis. Transfection of miR-106-5p mimics in chondrocytes significantly decreased cell proliferation and migration, promoted matrix degradation characterized by elevated MMP13 and ADAMTS5 expression, and reduced the expression of COL2A1 and ACAN in chondrocytes. Furthermore, we found that TIMP2 was directly regulated by miR-106-5p. Co-transfections of miR-106-5p mimics and TIMP2 resulted in higher levels of COL2A1 and ACAN, but lower levels of MMP13 and ADAMTS5. Together, these observations demonstrated that the lncRNA H19 may promote chondrocyte proliferation and migration and inhibit matrix degradation in OA possibly by targeting the miR-106b-5p/TIMP2 axis. In the future, H19 may serve as a potential therapeutic target for the treatment of OA.

Non-coding RNAs modulate function of extracellular matrix proteins

The extracellular matrix (ECM) creates a multifaceted system for the interaction of diverse structural proteins, matricellular molecules, proteoglycans, hyaluronan, and various glycoproteins that collaborate and bind with each other to produce a bioactive polymer. Alterations in the composition and configuration of ECM elements influence the cellular phenotype, thus participating in the pathogenesis of several human disorders. Recent studies indicate the crucial roles of non-coding RNAs in the modulation of ECM. Several miRNAs such as miR-21, miR-26, miR-19, miR-140, miR-29, miR-30, miR-133 have been dysregulated in disorders that are associated with disruption or breakdown of the ECM. Moreover, expression of MALAT1, PVT1, SRA1, n379519, RMRP, PFL, TUG1, TM1P3, FAS-AS1, PART1, XIST, and expression of other lncRNAs is altered in disorders associated with the modification of ECM components. In the current review, we discuss the role of lncRNAs and miRNAs in the modification of ECM and their relevance with the pathophysiology of human disorders such as cardiac/ lung fibrosis, cardiomyopathy, heart failure, asthma, osteoarthritis, and cancers.

Interplay between C-type lectin receptors and microRNAs in cellular homeostasis and immune response

C-type lectin receptors (CLRs) belong to the family of pattern recognition receptors (PRRs). They have a critical role to play in the regulation of a range of physiological functions including development, respiration, angiogenesis, inflammation, and immunity. CLRs can recognize distinct and conserved exogenous pathogen-associated as well as endogenous damage-associated molecular patterns. These interactions set off downstream signaling cascades, leading to the production of inflammatory mediators, activation of effector immune cells as well as regulation of the developmental and physiological homeostasis. CLR signaling must be tightly controlled to circumvent the excessive inflammatory burden and to maintain the cellular homeostasis. Recently, MicroRNAs (miRNAs) have been shown to be important regulators of expression of CLRs and their downstream signaling. The delicate balance between miRNAs and CLRs seems crucial in almost all aspects of multicellular life. Any dysregulations in the miRNA-CLR axes may lead to tumorigenesis or inflammatory diseases. Here, we present an overview of the current understanding of the central role of miRNAs in the regulation of CLR expression, profoundly impacting upon homeostasis and immunity, and thus, development of therapeutics against immune disorders.

Extracellular matrix mechanics regulate transfection and SOX9-directed differentiation of mesenchymal stem cells

Gene delivery within hydrogel matrices can potentially direct mesenchymal stem cells (MSCs) towards a chondrogenic fate to promote regeneration of cartilage. Here, we investigated whether the mechanical properties of the hydrogel containing the gene delivery systems could enhance transfection and chondrogenic programming of primary human bone marrow-derived MSCs. We developed collagen-I-alginate interpenetrating polymer network hydrogels with tunable stiffness and adhesion properties. The hydrogels were activated with nanocomplexed SOX9 polynucleotides to direct chondrogenic differentiation of MSCs. MSCs transfected within the hydrogels showed higher expression of chondrogenic markers compared to MSCs transfected in 2D prior to encapsulation. The nanocomplex uptake and resulting expression of transfected SOX9 were jointly enhanced by increased stiffness and cell-adhesion ligand density in the hydrogels. Further, transfection of SOX9 effectively induced MSCs chondrogenesis and reduced markers of hypertrophy compared to control matrices. These findings highlight the importance of matrix stiffness and adhesion as design parameters in gene-activated matrices for regenerative medicine. STATEMENT OF SIGNIFICANCE: Gene-activated matrices (GAMs) are biodegradable polymer networks integrating gene therapies, and they are promising technologies for supporting tissue regeneration. Despite this interest, there is still limited information on how to rationally design these systems. Here, we provide a systematic study of the effect of matrix stiffness and cell adhesion ligands on gene transfer efficiency. We show that high stiffness and the presence of cell-binding sites promote transfection efficiency and that this result is related to more efficient internalization and trafficking of the gene therapies. GAMs with optimized mechanical properties can induce cartilage formation and result in tissues with better characteristics for articular cartilage tissue engineering as compared to previously described standard methods.

Regulation and function of SOX9 during cartilage development and regeneration

Chondrogenesis is a highly coordinated event in embryo development, adult homeostasis, and repair of the vertebrate cartilage. Fate decisions and differentiation of chondrocytes accompany differential expression of genes critical for each step of chondrogenesis. SOX9 is a master transcription factor that participates in sequential events in chondrogenesis by regulating a series of downstream factors in a stage-specific manner. SOX9 either works alone or in combination with downstream SOX transcription factors, SOX5 and SOX6 as chondrogenic SOX Trio. SOX9 is reduced in the articular cartilage of patients with osteoarthritis while highly maintained during tumorigenesis of cartilage and bone. Gene therapy using viral and non-viral vectors accompanied by tissue engineering (scaffolds) is a promising tool to regenerate impaired cartilage. Delivery of SOX9 or chondrogenic SOX Trio into cells produces efficient therapeutic effects on chondrogenesis and this event is facilitated by scaffolds. Non-viral vector-guided delivery systems encapsulated or loaded in mechanically stable solid scaffolds are useful for the regeneration of articular cartilage. Here we review major milestones and most recent studies focusing on regulation and function of chondrogenic SOX Trio, during chondrogenesis and cartilage regeneration, and on the development of advanced technologies in gene delivery with tissue engineering to improve efficiency of cartilage repair process.

MicroRNA-30a regulates chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells through targeting Sox9

Cartilage injury is difficult to repair since the cartilage tissue lacks self-restoration ability. Improved formation of chondrocytes differentiated from the mesenchymal stem cells (MSC) by genetic regulation is a potentially promising therapeutic option. SOX9 is a critical transcription factor for mesenchymal condensation prior to chondrogenesis. Previous studies demonstrated that several microRNAs (miRNAs or miRs) play a critical role in the chondrogenic differentiation of MSCs. However, the interactional relations between miR-30a and SOX9 during chondrogenic differentiation of MSCs need to be further elucidated. In the present study, human bone marrow-derived mesenchymal stem cells have been isolated and induced into chondrogenic differentiation to imitate the cartilage formation in vitro. Additionally, the expression levels of several miRNAs that were reported to interact with the SOX9 3′untranslated region (UTR) were examined by using reverse transcription-quantitative PCR. The interactional relations between candidate miRNAs and SOX9 were verified with the transfection of a miRNA mimic or inhibitor and a luciferase reporter gene assay. The results indicate that miR-30a and miR-195 were consistently increased during MSC chondrogenic differentiation. Additionally, the binding of miR-30a to the SOX9 3UTR was verified. Then, the authors upregulated the expression of miR-30a and found that MSC chondrogenic differentiation was inhibited. Taken together, the results of the present study demonstrate that miR-30a has a negative regulatory effect on MSC chondrogenic differentiation by targeting SOX9. Advances in epigenetic regulating methods will likely be the future of systemic treatment of cartilage injury.

Decreased expression of microRNA-145 promotes the biological functions of fibroblasts in hypertrophic scar tissues by upregulating the expression of transcription factor SOX-9

The present study aimed to determine the expression of microRNA (miRNA or miR)-145 in hypertrophic scars at the tissue and cellular levels, and to investigate its biological functions and mechanism of action. A total of 36 patients who were diagnosed with hypertrophic scar were included in the present study. Reverse transcription-quantitative polymerase chain reaction was used to determine the expression of miR-145 in tissues and fibroblasts. Primary fibroblasts were transfected with negative control miRNA, miR-145 mimics or inhibitor. A Cell Counting Kit-8 assay was performed to determine the level of proliferation of fibroblasts. Flow cytometry was employed for cell cycles determination and apoptosis in fibroblasts. A Matrigel assay was used to evaluate the invasion ability of fibroblasts. Western blotting was used to determine the expression of the transcription factor SOX-9 (SOX-9) protein in fibroblasts. Rescue experiments were performed to examine the effect of SOX-9 on the regulation of fibroblasts by miR-145. The dual luciferase reporter assay was performed to identify the direct interaction between SOX-9 and miR-145. The expression of miR-145 was reduced in hypertrophic tissues and fibroblasts. Overexpression of miR-145 inhibited the proliferation, G1/S phase transition and invasion of fibroblasts, and promoted the apoptosis of fibroblasts. In addition, overexpression of miR-145 inhibited SOX-9 protein expression. By contrast, the expression of SOX-9 reversed the effects of miR-145 on the proliferation, cell cycle, apoptosis and invasion of fibroblasts. The miR-145 seed region was able to bind with the 3′-untranslated region of the SOX-9 mRNA to regulate its expression. The present study demonstrated that miR-145 expression is reduced in hypertrophic scar tissues and negatively associated with SOX-9 expression. In addition, miR-145 inhibits the proliferation, cell cycle and invasion, and promotes the apoptosis of fibroblasts by down-regulating the expression of SOX-9. The current study provides a potential target for the clinical diagnosis and treatment of hypertrophic scars.

Comparative analysis of milk microRNA in the therian lineage highlights the evolution of lactation

Milk is a complex secretion that has an important role in mammalian reproduction. It is only recently that sequencing technologies have allowed the identification and quantification of microRNA (miRNA) in milk of a growing number of mammalian species. This provides a novel window on the study of the evolution and functionality of milk through the comparative analysis of milk miRNA content. Here, milk miRNA sequencing data from five species (one marsupial (tammar wallaby) and four eutherians (human, mouse, cow and pig)) have been retrieved from public depositories and integrated in order to perform a comparison of milk miRNA profiles. The study shows that milk miRNA composition varies widely between species, except for a few miRNAs that are ubiquitously expressed in the milk of all mammals and indicates that milk miRNA secretion has broadly evolved during mammalian evolution. The putative functions of the most abundant milk miRNAs are also discussed.

MicroRNA-15a-5p Regulates the Development of Osteoarthritis by Targeting PTHrP in Chondrocytes

BACKGROUND AND AIMS

A growing body of research has demonstrated that the degeneration of chondrocytes is the primary cause of osteoarthritis (OA). Parathyroid hormone-related protein (PTHrP) can alleviate the degeneration of chondrocytes via promotion of chondrocyte proliferation and inhibition of terminal differentiation, but the underlying mechanism remains unknown. This study aimed to identify the microRNAs (miRNAs) that may target PTHrP and regulate the proliferation and terminal differentiation of chondrocytes.

METHODS

Bioinformatic analysis was used to predict which miRNAs target PTHrP. We collected human knee cartilage specimens to acquire the primary chondrocytes, which we then used to test the expression and function of the targeted miRNAs. To explore the effects of miR-15a-5p on the putative binding sites, specific mimics or inhibitors were transfected into the chondrocytes. Furthermore, a dual-luciferase reporter gene assay and chondrocyte degeneration-related factors were used to verify the possible mechanism.

RESULTS

The expression of PTHrP was upregulated in the OA chondrocytes, whilst miR-15a-5p was downregulated in the OA chondrocytes. A negative correlation was observed between PTHrP and miR-15a-5p. The knockdown of miR-15a-5p promoted the growth of chondrocytes and inhibited calcium deposition, whilst overexpression of miR-15a-5p reversed this trend. The effect of miR-15a-5p overexpression was neutralised by PTHrP. Dual-luciferase reporter assays revealed that PTHrP can be used as a novel targeting molecule for miR-15a-5p.

CONCLUSIONS

miR-15a-5p promotes the degeneration of chondrocytes by targeting PTHrP and, in addition to helping us understand the development of OA, may be a potential biomarker of OA.

Targeting anti-chondrogenic factors for the stimulation of chondrogenesis: A new paradigm in cartilage repair

Trauma and age-related cartilage disorders represent a major global cause of morbidity, resulting in chronic pain and disability in patients. A lack of effective therapies, together with a rapidly aging population, creates an impressive clinical and economic burden on healthcare systems. In this scenario, experimental therapies based on transplantation or in situ stimulation of skeletal Mesenchymal Stem/progenitor Cells (MSCs) have raised great interest for cartilage repair. Nevertheless, the challenge of guiding MSC differentiation and preventing cartilage hypertrophy and calcification still needs to be overcome. While research has mostly focused on the stimulation of cartilage anabolism using growth factors, several issues remain unresolved prompting the field to search for novel solutions. Recently, inhibition of anti-chondrogenic regulators has emerged as an intriguing opportunity. Anti-chondrogenic regulators include extracellular proteins as well as intracellular transcription factors and microRNAs that act as potent inhibitors of pro-chondrogenic signals. Suppression of these inhibitors can enhance MSC chondrogenesis and production of cartilage matrix. We here review the current knowledge concerning different types of anti-chondrogenic regulators. We aim to highlight novel therapeutic targets for cartilage repair and discuss suitable tools for suppressing their anti-chondrogenic functions. Further effort is needed to unveil the therapeutic perspectives of this approach and pave the way for effective treatment of cartilage injuries in patients. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Onset and Progression of Human Osteoarthritis-Can Growth Factors, Inflammatory Cytokines, or Differential miRNA Expression Concomitantly Induce Proliferation, ECM Degradation, and Inflammation in Articular Cartilage?

Osteoarthritis (OA) is a degenerative whole joint disease, for which no preventative or therapeutic biological interventions are available. This is likely due to the fact that OA pathogenesis includes several signaling pathways, whose interactions remain unclear, especially at disease onset. Early OA is characterized by three key events: a rarely considered early phase of proliferation of cartilage-resident cells, in contrast to well-established increased synthesis, and degradation of extracellular matrix components and inflammation, associated with OA progression. We focused on the question, which of these key events are regulated by growth factors, inflammatory cytokines, and/or miRNA abundance. Collectively, we elucidated a specific sequence of the OA key events that are described best as a very early phase of proliferation of human articular cartilage (AC) cells and concomitant anabolic/catabolic effects that are accompanied by incipient pro-inflammatory effects. Many of the reviewed factors appeared able to induce one or two key events. Only one factor, fibroblast growth factor 2 (FGF2), is capable of concomitantly inducing all key events. Moreover, AC cell proliferation cannot be induced and, in fact, is suppressed by inflammatory signaling, suggesting that inflammatory signaling cannot be the sole inductor of all early OA key events, especially at disease onset.

Circular RNA circ-4099 is induced by TNF-α and regulates ECM synthesis by blocking miR-616-5p inhibition of Sox9 in intervertebral disc degeneration

Circular RNAs (circRNAs) play important roles in the initiation and development of different diseases. Here, we detected their role in intervertebral disc (IVD) degeneration. An Arraystar human circular RNA microarray assay was used to detect circRNAs in normal and degenerated human IVD nucleus pulposus (NP) tissues. The role of circ-4099 in IVDD and its mechanism were evaluated by qRT-PCR and gain-of-function/loss-of-function studies. Interaction networks for competing endogenous RNAs (ceRNAs), miRNAs, and miRNA target gene were detected by bioinformatics analysis, RNA immunoprecipitation and luciferase assay. Expression of seventy-two circRNAs were increased by more than twofold in degenerated NP tissues. qRT-PCR showed that the expression of circ-4099 in NP tissues was consistent with that of the array screening. Over-expression of circ-4099 increased the expression of Collagen II and Aggrecan and decreased the secretion of the pro-inflammatory factors IL-1β, TNF-α, and PGE2. TNF-α treatment increased circ-4099 expression in NP cells. NF-κB/MAPK inhibitors or shRNAs abolished the inductive effects of TNF-α on circ-4099 expression. We further demonstrated that circ-4099 was able to function as a “sponge” by competitively binding miR-616-5p, which reversed the suppression of Sox9 by miR-616-5p. We used DNA pull-down and spectrometry experiments to show that TNF-α can promote circ-4099 transcription through upregulation of GRP78. We provide the first evidence that shows circRNAs are differentially expressed in degenerated and normal NP tissues. Circ-4099 may play a role in a protective mechanism and be part of a compensatory response that maintains the synthesis and secretion of the extracellular matrix in NP cells and might be a protective factor in IVD degeneration as well as restore NP cell function.

A circular RNA molecule helps protect against degenerative disc disease. Hua Wang and coworkers from Sun Yat-Sen University in Guangzhou, China, examined whether circular RNAs, regulatory molecules that take the form of closed RNA loops, contribute to intervertebral disc degeneration, a condition in which connective tissue in the spine breaks down over time, causing back pain and weakness. They found 72 circular RNAs that were either significantly over- or under-expressed in the inner core tissue of intervertebral discs from patients with this condition. They showed that one of these circular RNAs, circ-4099, increased the production of key cartilage proteins. This RNA also blocked the activity of another non-circular regulatory RNA that normally inhibits a molecular pathway needed for proper cartilage formation. Enhancing the activity of this protective molecule could help treat degenerative disc disease.

Extracellular genomic biomarkers of osteoarthritis

INTRODUCTION

Osteoarthritis (OA), a chronic, debilitating and degenerative disease of the joints, is the most common form of arthritis. The seriousness of this prevalent and chronic disease is often overlooked. Disease modifying OA drug development is hindered by the lack of soluble biomarkers to detect OA early. The objective of OA biomarker research is to identify early OA prior to the appearance of radiographic signs and the development of pain. Areas covered: This review has focused on extracellular genomic material that could serve as biomarkers of OA. Recent studies have examined the expression of extracellular genomic material such as miRNA, lncRNA, snoRNA, mRNA and cell-free DNA, which are aberrantly expressed in the body fluids of OA patients. Changes in genomic content of peripheral blood mononuclear cells in OA could also function as biomarkers of OA. Expert commentary: There is an unmet need for soluble biomarkers for detecting and then monitoring OA disease progression. Extracellular genomic material research may also reveal more about the underlying pathophysiology of OA. Minimally-invasive liquid biopsies such as synovial fluid and blood sampling of genomic material may be more sensitive over radiography in the detection, diagnosis and monitoring of OA in the future.

Emerging potential of gene silencing approaches targeting anti-chondrogenic factors for cell-based cartilage repair

The field of cartilage repair has exponentially been growing over the past decade. Here, we discuss the possibility to achieve satisfactory regeneration of articular cartilage by means of human mesenchymal stem cells (hMSCs) depleted of anti-chondrogenic factors and implanted in the site of injury. Different types of molecules including transcription factors, transcriptional co-regulators, secreted proteins, and microRNAs have recently been identified as negative modulators of chondroprogenitor differentiation and chondrocyte function. We review the current knowledge about these molecules as potential targets for gene knockdown strategies using RNA interference (RNAi) tools that allow the specific suppression of gene function. The critical issues regarding the optimization of the gene silencing approach as well as the delivery strategies are discussed. We anticipate that further development of these techniques will lead to the generation of implantable hMSCs with enhanced potential to regenerate articular cartilage damaged by injury, disease, or aging.

The PI3K/Akt pathway: a critical player in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is thought to be the primary cause of low back pain, a severe public health problem worldwide. Current therapy for IDD aims to alleviate the symptoms and does not target the underlying pathological alternations within the disc. Activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway protects against IDD, which is attributed to increase of ECM content, prevention of cell apoptosis, facilitation of cell proliferation, induction or prevention of cell autophagy, alleviation of oxidative damage, and adaptation of hypoxic microenvironment. In the current review, we summarize recent progression on activation and negative regulation of the PI3K/Akt signaling pathway, and highlight its impact on IDD. Targeting this pathway could become an attractive therapeutic strategy for IDD in the near future.

Role of MicroRNA in Osteoarthritis

Although the potential effect of aberrant expression of catabolic and anabolic genes on the development of osteoarthritis (OA) is well-documented, the regulatory mechanism for the expression of these genes in articular chondrocytes remains to be elucidated. The recent advances in epigenetic studies have identified microRNA (miRNA) as one of the epigenetic mechanisms for the regulation of gene expression. This mini review highlights the role of miRNA in the regulation of gene expression in articular chondrocytes and its significance in the pathogenesis of OA, with a discussion on the potential of miRNA as a new biomarker and therapeutic target for OA. Further investigations are required to determine the specificity, sensitivity, and efficacy of miRNA for clinical applications.

Adipose-Derived Stem Cells Cocultured with Chondrocytes Promote the Proliferation of Chondrocytes

Articular cartilage injury and defect caused by trauma and chronic osteoarthritis vascularity are very common, while the repair of injured cartilage remains a great challenge due to its limited healing capacity. Stem cell-based tissue engineering provides a promising treatment option for injured articular cartilage because of the cells potential for multiple differentiations. However, its application has been largely limited by stem cell type, number, source, proliferation, and differentiation. We hypothesized that (1) adipose-derived stem cells are ideal seed cells for articular cartilage repair because of their accessibility and abundance and (2) the microenvironment of articular cartilage could induce adipose-derived stem cells (ADSCs) to differentiate into chondrocytes. In order to test our hypotheses, we isolated stem cells from rabbit adipose tissues and cocultured these ADSCs with rabbit articular cartilage chondrocytes. We found that when ADSCs were cocultured with chondrocytes, the proliferation of articular cartilage chondrocytes was promoted, the apoptosis of chondrocytes was inhibited, and the osteogenic and chondrogenic differentiation of ADSCs was enhanced. The study on the mechanism of this coculture system indicated that the role of this coculture system is similar to the function of TGF-β1 in the promotion of chondrocytes.

PCL-PEG-PCL film promotes cartilage regeneration in vivo

OBJECTIVE

Management of chondral defects has long been a challenge due to poor self-healing capacity of articular cartilage. Many approaches, ranging from symptomatic treatment to structural cartilage regeneration, have obtained very limited satisfactory results. Cartilage tissue engineering, which involves optimized combination of novel scaffolds, cell sources and growth factors, has emerged as a promising strategy for cartilage regeneration and repair. In this study, the aim was to investigate the role of poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL, PCEC) PCEC scaffold in cartilage repair.

MATERIALS AND METHODS

First, PCEC film was fabricated, and its characteristics were tested using SEM and AFM. Cell (rASC - rat adipose-derived stem cells, and mASCs - green fluorescent mouse adipose-derived stem cells) morphologies on PCEC film were observed using SEM and fluorescence microscopy, after cell seeding. Tests of cell viability on PCEC film were conducted using the CCK-8 assay. Furthermore, full cartilage defects in rats were created, and PCEC films were implanted, to evaluate their healing effects, over 8 weeks.

RESULTS

It was found that PCEC film, as a biomaterial implant, possessed good in vitro properties for cell adhesion, migration and proliferation. Importantly, in the in vivo experiment, PCEC film exhibited desirable healing outcomes.

CONCLUSIONS

These results demonstrated that PCEC film was a good scaffold for cartilage tissue engineering for improving cell proliferation and adhesion and could lead to excellent repair of cartilage defects.

miR-30 Family Controls Proliferation and Differentiation of Intestinal Epithelial Cell Models by Directing a Broad Gene Expression Program That Includes SOX9 and the Ubiquitin Ligase Pathway

Proliferation and differentiation of intestinal epithelial cells (IECs) occur in part through precise regulation of key transcription factors, such as SOX9. MicroRNAs (miRNAs) have emerged as prominent fine-tuners of transcription factor expression and activity. We hypothesized that miRNAs, in part through the regulation of SOX9, may mediate IEC homeostasis. Bioinformatic analyses of the SOX9 3'-UTR revealed highly conserved target sites for nine different miRNAs. Of these, only the miR-30 family members were both robustly and variably expressed across functionally distinct cell types of the murine jejunal epithelium. Inhibition of miR-30 using complementary locked nucleic acids (LNA30bcd) in both human IECs and human colorectal adenocarcinoma-derived Caco-2 cells resulted in significant up-regulation of SOX9 mRNA but, interestingly, significant down-regulation of SOX9 protein. To gain mechanistic insight into this non-intuitive finding, we performed RNA sequencing on LNA30bcd-treated human IECs and found 2440 significantly increased genes and 2651 significantly decreased genes across three time points. The up-regulated genes are highly enriched for both predicted miR-30 targets, as well as genes in the ubiquitin-proteasome pathway. Chemical suppression of the proteasome rescued the effect of LNA30bcd on SOX9 protein levels, indicating that the regulation of SOX9 protein by miR-30 is largely indirect through the proteasome pathway. Inhibition of the miR-30 family led to significantly reduced IEC proliferation and a dramatic increase in markers of enterocyte differentiation. This in-depth analysis of a complex miRNA regulatory program in intestinal epithelial cell models provides novel evidence that the miR-30 family likely plays an important role in IEC homeostasis.