The effect of microRNA-21 on proliferation and matrix synthesis of chondrocytes embedded in atelocollagen gel

miRNA induced 3D bioprinted-heterotypic osteochondral interface

The engineering of osteochondral interfaces remains a challenge. MicroRNAs (miRs) have emerged as significant tools to regulate the differentiation and proliferation of osteogenic and chondrogenic formation in the human musculoskeletal system. Here, we describe a novel approach to osteochondral reconstruction based on the three-dimensional (3D) bioprinting of miR-transfected adipose-derived stem cell (ADSC) spheroids to produce a heterotypic interface that addresses the intrinsic limitations of the traditional approach to inducing zonal differentiation via the use of diffusible cytokines. We evaluated the delivery of miR-148b for osteogenic differentiation and the codelivery of miR-140 and miR-21 for the chondrogenic differentiation of ADSC spheroids. Our results demonstrated that miR-transfected ADSC spheroids exhibited upregulated expression of osteogenic and chondrogenic differentiation related gene and protein markers, and enhanced mineralization and cell proliferation compared to spheroids differentiated using a commercially-available differentiation medium. Upon confirmation of the osteogenic and chondrogenic potential of miR-transfected ADSC spheroids, using aspiration-assisted bioprinting, these spheroids were 3D bioprinted into a dual-layer heterotypic osteochondral interface with a stratified arrangement of distinct osteogenic and chondrogenic zones. The proposed approach holds great promise for the biofabrication of stratified tissues, not only for the osteochondral interfaces presented in this work, but also for other composite tissues and tissue interfaces, such as, but not limited to, the bone-tendon-muscle interface and craniofacial tissues.

miR-21-5p protects IL-1β-induced human chondrocytes from degradation

OBJECTIVE

Osteoarthritis (OA) is a prevalent degenerative disease caused by various factors. MicroRNAs are important regulators in OA. MiR-21-5p expression is decreased in OA cartilage, but the effects of modulating miR-21-5p on cartilage regeneration are unknown. Therefore, our aim was to investigate the effects of miR-21-5p on cartilage metabolism of OA chondrocytes.

DESIGN

We used IL-1β (10 ng/ml) to mimic OA chondrocytes. OA chondrocytes were transfected with miR-21-5p, the gene expression of COL2A1, MMP13, and ADAMTS5 was detected by qPCR. At the same time, COL2A1, MMP13, and ADAMTS5 were analyzed at the protein level by Western blot. CCK8 measured the cell's viability and SA-β-gal detected the cell's senescence.

RESULTS

Upregulation of miR-21-5p had increased COL2A1 expression and decreased MM P13 and ADAMTS5 expression, which were in accord with Western blot data. SA-β-gal activity significantly increased, the viability was decreased in OA chondrocytes, and upregulation of miR-21-5p can decrease the SA-β-gal activity and increase cell viability.

CONCLUSION

MiR-21-5p might be a potential disease-modifying compound in OA, as it promotes hyaline cartilage production. These results provided that novel insights into the important function in OA pathological development.

Biomimicking Fiber Scaffold as an Effective In Vitro and In Vivo MicroRNA Screening Platform for Directing Tissue Regeneration

MicroRNAs effectively modulate protein expression and cellular response. Unfortunately, the lack of robust nonviral delivery platforms has limited the therapeutic application of microRNAs. Additionally, there is a shortage of drug-screening platforms that are directly translatable from in vitro to in vivo. Here, a fiber substrate that provides nonviral delivery of microRNAs for in vitro and in vivo microRNA screening is introduced. As a proof of concept, difficult-to-transfect primary neurons are targeted and the efficacy of this system is evaluated in a rat spinal cord injury model. With this platform, enhanced gene-silencing is achieved in neurons as compared to conventional bolus delivery (p < 0.05). Thereafter, four well-recognized microRNAs (miR-21, miR-222, miR-132, and miR-431) and their cocktails are screened systematically. Regardless of age and origin of the neurons, similar trends are observed. Next, this fiber substrate is translated into a 3D system for direct in vivo microRNA screening. Robust nerve ingrowth is observed as early as two weeks after scaffold implantation. Nerve regeneration in response to the microRNA cocktails is similar to in vitro experiments. Altogether, the potential of the fiber platform is demonstrated in providing effective microRNA screening and direct translation into in vivo applications.

Selective enrichment of microRNAs in extracellular matrix vesicles produced by growth plate chondrocytes

Matrix vesicles (MVs) are membrane organelles found in the extracellular matrix of calcifying cells, which contain matrix processing enzymes and regulate the extracellular environment via action of these enzymes. It is unknown whether MVs are also exosomic mediators of cell-cell communication via transfer of RNA material, and specifically, microRNA (miRNA). We investigated the presence of RNA in MVs isolated from cultures of costochondral growth zone chondrocytes. Our results showed that the average yield of MV RNA was 1.93±0.78ng RNA/10(4) cells, which was approximately 0.1% of the parent cell's total RNA. MV RNA was well-protected from RNase by the lipid membrane and was highly enriched in small RNA molecules compared to cells. Moreover, coding and non-coding small RNAs in MVs were in proportions that differed from parent cells. Enrichment of specific miRNAs was consistently observed in all three miRNA detection platforms that we used, suggesting that miRNAs are selectively packaged into MVs. MV-enriched miRNAs were related to different signaling pathways associated with bone formation. This study suggests a significant role for MVs as "matrisomes" in cell-cell communication in cartilage and bone development via transfer of specific miRNAs.

MicroRNA-21 Promotes Proliferation of Fibroblast-Like Synoviocytes through Mediation of NF-κB Nuclear Translocation in a Rat Model of Collagen-Induced Rheumatoid Arthritis

MicroRNA-21 (miR-21) is overexpressed in patients with rheumatoid arthritis (RA). This study was designed to investigate the effect and mechanism of miR-21 on cell proliferation in fibroblast-like synoviocytes (FLS) of RA. FLS were primary-cultured from a rat RA model. RA-FLS and normal FLS were infected with lentivirus (anti-miR-21 or pro-miR-21) for overexpression or downregulation of miR-21, respectively. The effects of miR-21 overexpression or inhibition on nucleoprotein NF-κB levels and FLS cell proliferation were evaluated by western blotting and MTT assays. The effects of an inhibitor of NF-κB nuclear translocation (BAY 11-7082) were also evaluated. The results showed that the levels of miR-21 and nucleoprotein NF-κB were increased in FLS of RA model rats compared to the control group. Downregulation of miR-21 in RA FLS led to a significant decrease in nucleoprotein NF-κB levels and cell proliferation rates compared to the antinegative control (NC) group. However, miR-21 overexpression in normal FLS resulted in a significant increase of nucleoprotein NF-κB levels and cell proliferation rates compared to the pro-NC group. The effects of miR-21 overexpression were reversed by BAY 11-7082. We concluded that upregulated miR-21 in FLS in RA model rats may promote cell proliferation by facilitating NF-κB nuclear translocation, thus affecting the NF-κB pathway.

The Role of miRNAs in Cartilage Homeostasis

Osteoarthritis (OA) is an age-related disease with poorly understood pathogenesis. Recent studies have demonstrated that miRNA might play a key role in OA initiation and development. We reviewed recent publications and elucidated the connection between miRNA and OA cartilage anabolic and catabolic signals, including four signaling pathways: TGF-β/Smads and BMPs signaling, associated with cartilage anabolism; and MAPK and NF-KB signaling, associated with cartilage catabolism. We also explored the relationships with MMP, ADAMTS and NOS (NitricOxide Synthases) families, as well as with the catabolic cytokines IL-1 and TNF-α. The potential role of miRNAs in biological processes such as cartilage degeneration, chondrocyte proliferation, and differentiation is discussed. Collective evidence indicates that miRNAs play a critical role in cartilage degeneration. These findings will aid in understanding the molecular network that governs articular cartilage homeostasis and in to elucidate the role of miRNA in the pathogenesis of OA.

MicroRNAs: modulators of cell identity, and their applications in tissue engineering

MicroRNAs post-transcriptionally regulate the expression of approximately 60% of the mammalian genes, and have an important role in maintaining the differentiated state of somatic cells through the expression of unique tissue-specific microRNA sets. Likewise, the stemness of pluripotent cells is also sustained by embryonic stem cell-enriched microRNAs, which regulate genes involved in cell cycle, cell signaling and epigenetics, among others. Thus, microRNAs work as modulator molecules that ensure the appropriate expression profile of each cell type. Manipulation of microRNA expression might determine the cell fate. Indeed, microRNA-mediated reprogramming can change the differentiated status of somatic cells towards stemness or, conversely, microRNAs can also transform stem- into differentiated-cells both in vitro and in vivo. In this Review, we outline what is currently known in this field, focusing on the applications of microRNA in tissue engineering.

MicroRNAs in cartilage development, homeostasis, and disease

microRNAs (miRNAs) regulate gene expression mainly at the posttranscriptional level. Many different miRNAs are expressed in chondrocytes, and each individual miRNA can regulate hundreds of target genes, creating a complex gene regulatory network. Experimental evidence suggests that miRNAs play significant roles in various aspects of cartilage development, homeostasis, and pathology. The possibility that miRNAs can be novel therapeutic targets for cartilage diseases led to vigorous investigations to understand the role of individual miRNAs in skeletal tissues. Here, we summarize our current understanding of miRNAs in chondrocytes and cartilage. In the first part, we discuss roles of miRNAs in growth plate development and chondrocyte differentiation. In the second part, we put a particular focus on articular cartilage and discuss the significance of variety of findings in the context of osteoarthritis, the most common degenerative joint disease.

Gene modification of mesenchymal stem cells and articular chondrocytes to enhance chondrogenesis

Current cell based treatment for articular cartilage and osteochondral defects are hampered by issues such as cellular dedifferentiation and hypertrophy of the resident or transplanted cells. The reduced expression of chondrogenic signalling molecules and transcription factors is a major contributing factor to changes in cell phenotype. Gene modification of chondrocytes may be one approach to redirect cells to their primary phenotype and recent advances in nonviral and viral gene delivery technologies have enabled the expression of these lost factors at high efficiency and specificity to regain chondrocyte function. This review focuses on the various candidate genes that encode signalling molecules and transcription factors that are specific for the enhancement of the chondrogenic phenotype and also how epigenetic regulators of chondrogenesis in the form of microRNA may also play an important role.

miR-21 promotes human nucleus pulposus cell proliferation through PTEN/AKT signaling

The precise role of nucleus pulposus cell proliferation in the pathogenesis of intervertebral disc degeneration remains to be elucidated. Recent findings have revealed that microRNAs, a class of small noncoding RNAs, may regulate cell proliferation in many pathological conditions. Here, we showed that miR-21 was significantly upregulated in degenerative nucleus pulposus tissues when compared with nucleus pulposus tissues that were isolated from patients with idiopathic scoliosis and that miR-10b levels were associated with disc degeneration grade. Moreover, bioinformatics target prediction identified PTEN as a putative target of miR-21. miR-21 inhibited PTEN expression by directly targeting the 3′UTR, and this inhibition was abolished through miR-21 binding site mutations. miR-21 overexpression stimulated cell proliferation and AKT signaling pathway activation, which led to cyclin D1 translation. Additionally, the increase in proliferation and cyclin D1 expression induced by miR-21 overexpression was almost completely blocked by Ly294002, an AKT inhibitor. Taken together, aberrant miR-21 upregulation in intervertebral disc degeneration could target PTEN, which would contribute to abnormal nucleus pulposus cell proliferation through derepressing the Akt pathway. Our study also underscores the potential of miR-21 and the PTEN/Akt pathway as novel therapeutic targets in intervertebral disc degeneration.

microRNA-140 targets RALA and regulates chondrogenic differentiation of human mesenchymal stem cells by translational enhancement of SOX9 and ACAN

Lesions of articular cartilage do not heal spontaneously. One treatment strategy would be to make cartilage in the laboratory by directed chondrogenic differentiation of mesenchymal stem cells (MSCs). To promote our understanding of the molecular control of chondrogenesis, we have compared the changes in microRNAs (miRNAs) during in vitro chondrogenesis of MSCs with those observed in uncultured and dedifferentiated articular chondrocytes (ACs). Several miRNAs showed a reciprocal relationship during the differentiation of MSCs and dedifferentiation of ACs. miR-140-5p and miR-140-3p changed the most during in vitro chondrogenesis, they were the miRNAs most highly expressed in tissue-engineered chondrocytes, and they were also among the miRNAs most highly expressed in uncultured ACs. There was a 57% overlap for the 100 most highly expressed miRNAs in differentiated MSCs and uncultured ACs, but for other miRNAs, the expression pattern was quite different. We transiently and stably inhibited and overexpressed miR-140-5p and miR-140-3p in differentiating MSCs and dedifferentiating ACs, respectively, to describe global effects and identify and validate new targets. Surprisingly, SOX9 and aggrecan proteins were found to be downregulated in anti-miR-140 transduced differentiating MSCs despite unchanged mRNA levels. This suggests that miR-140 stimulates in vitro chondrogenesis by the upregulation of these molecules at the protein level. RALA, a small GTPase, was identified as a miR-140 target and knockdown experiments showed that RALA regulated SOX9 at the protein level. These observations shed new light on the effect of miR-140 for chondrogenesis in vitro and in vivo.

Characterization of microRNA expression profiles in patients with intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is associated with lower back pain and is a global burden with severe healthcare and socioeconomic consequences. However, the underlying mechanisms of IDD remain largely unelucidated. Accumulating evidence has indicasted that newly defined gene regulators, microRNAs (miRNAs), play a vital role in neurodegenerative, pathophysiological and certain reproductive disorders. To characterize the differential miRNA expression profiles between IDD and spinal cord injury, specimens from 3 patients with IDD and 3 with spinal cord injury were selected for microarray analysis. Total RNA from these 6 specimens was extracted and subjected to global miRNA expression analysis using the Exiqon miRCURY™ LNA Array (v.16.0). The microarray data were then validated by quantitative reverse transcription polymerase chain reaction (qRT-PCR). In addition, bioinformatics analysis was performed to investigate the dysregulated miRNA target genes and signaling pathways involved. Among the miRNAs analyzed, 25 miRNAs were found to be upregulated and 26 were found to be downregulated in the IDD group compared with the spinal cord injury group. The qRT-PCR results validated the microarray data. Bioinformatics analysis indicated that the signaling pathways most likely to be controlled by these miRNAs were the phosphoinositide 3-kinase (PI3K)-Akt, mitogen-activated protein kinase (MAPK), epidermal growth factor receptor (EGFR; ErbB) and Wnt pathways. Our results demonstrated that the miRNA expression in patients with IDD differed significantly from that in patients who sustained injury to the intervertebral disc. Our data indicate that the dysregulated miRNAs control the signaling pathways important for the maintenance of IDD. Further studies on miRNA target gene identification and biological functions may address the specific regulatory mechanisms of miRNAs in IDD, and may provide valuable insight into the diagnosis and treatment of IDD.

Transcriptomic signatures in cartilage ageing

Introduction

Age is an important factor in the development of osteoarthritis. Microarray studies provide insight into cartilage aging but do not reveal the full transcriptomic phenotype of chondrocytes such as small noncoding RNAs, pseudogenes, and microRNAs. RNA-Seq is a powerful technique for the interrogation of large numbers of transcripts including nonprotein coding RNAs. The aim of the study was to characterise molecular mechanisms associated with age-related changes in gene signatures.

Methods

RNA for gene expression analysis using RNA-Seq and real-time PCR analysis was isolated from macroscopically normal cartilage of the metacarpophalangeal joints of eight horses; four young donors (4 years old) and four old donors (>15 years old). RNA sequence libraries were prepared following ribosomal RNA depletion and sequencing was undertaken using the Illumina HiSeq 2000 platform. Differentially expressed genes were defined using Benjamini-Hochberg false discovery rate correction with a generalised linear model likelihood ratio test (P < 0.05, expression ratios ± 1.4 log₂ fold-change). Ingenuity pathway analysis enabled networks, functional analyses and canonical pathways from differentially expressed genes to be determined.

Results

In total, the expression of 396 transcribed elements including mRNAs, small noncoding RNAs, pseudogenes, and a single microRNA was significantly different in old compared with young cartilage (± 1.4 log₂ fold-change, P < 0.05). Of these, 93 were at higher levels in the older cartilage and 303 were at lower levels in the older cartilage. There was an over-representation of genes with reduced expression relating to extracellular matrix, degradative proteases, matrix synthetic enzymes, cytokines and growth factors in cartilage derived from older donors compared with young donors. In addition, there was a reduction in Wnt signalling in ageing cartilage.

Conclusion

There was an age-related dysregulation of matrix, anabolic and catabolic cartilage factors. This study has increased our knowledge of transcriptional networks in cartilage ageing by providing a global view of the transcriptome.

MicroRNA-199a-3p, microRNA-193b, and microRNA-320c are correlated to aging and regulate human cartilage metabolism

MicroRNAs (miRNAs) are small RNAs of ∼22 base pairs that regulate gene expression. We harvested cartilage tissue from patients with polydactylism, anterior cruciate ligament injury, and osteoarthritis undergoing total knee arthroplasty and used microarrays to identify miRNAs whose expression is upregulated or downregulated with age. The results were assessed by real-time PCR and MTT assay in a mimic group, in which synthetic double-stranded RNA from the isolated miRNA was transfected to upregulate expression, and in an inhibitor group, in which the miRNA was bound specifically to downregulate expression. The expression of two miRNAs (miR-199a-3p and miR-193b) was upregulated with age and that of one miRNA (miR-320c) was downregulated with age. A real-time PCR assay showed that type 2 collagen, aggrecan, and SOX9 expression were downregulated in the miR-199a-3p mimic group but was upregulated in the inhibitor group. Similar results were observed for miR-193b. By contrast, ADAMTS5 expression was downregulated in the miR-320c mimic group and upregulated in the inhibitor group. Cell proliferative activity was upregulated significantly in the miR-193b inhibitor group compared with the control group. We believe that miR-199a-3p and miR-193b are involved in the senescence of chondrocytes, and miR-320c is involved in the juvenile properties of chondrocytes.

MicroRNAs regulate osteogenesis and chondrogenesis

MicroRNAs (miRNAs) are a class of small molecules and non-coding single strand RNAs that regulate gene expression at the post-transcriptional level by binding to specific sequences within target genes. miRNAs have been recognized as important regulatory factors in organism development and disease expression. Some miRNAs regulate the proliferation and differentiation of osteoblasts, osteoclasts and chondrocytes, eventually influencing metabolism and bone formation. miRNAs are expected to provide potential gene therapy targets for the clinical treatment of metabolic bone diseases and bone injuries. Here, we review the recent research progress on the regulation of miRNAs in bone biology, with a particular focus on the miRNA-mediated control mechanisms of bone and cartilage formation.