microRNA-seq of cartilage reveals an overabundance of miR-140-3p which contains functional isomiRs

Specific isoforms of the ubiquitin ligase gene WWP2 are targets of osteoarthritis genetic risk via a differentially methylated DNA sequence

BACKGROUND

Transitioning from a genetic association signal to an effector gene and a targetable molecular mechanism requires the application of functional fine-mapping tools such as reporter assays and genome editing. In this report, we undertook such studies on the osteoarthritis (OA) risk that is marked by single nucleotide polymorphism (SNP) rs34195470 (A > G). The OA risk-conferring G allele of this SNP associates with increased DNA methylation (DNAm) at two CpG dinucleotides within WWP2. This gene encodes a ubiquitin ligase and is the host gene of microRNA-140 (miR-140). WWP2 and miR-140 are both regulators of TGFβ signaling.

METHODS

Nucleic acids were extracted from adult OA (arthroplasty) and foetal cartilage. Samples were genotyped and DNAm quantified by pyrosequencing at the two CpGs plus 14 flanking CpGs. CpGs were tested for transcriptional regulatory effects using a chondrocyte cell line and reporter gene assay. DNAm was altered using epigenetic editing, with the impact on gene expression determined using RT-qPCR. In silico analysis complemented laboratory experiments.

RESULTS

rs34195470 genotype associates with differential methylation at 14 of the 16 CpGs in OA cartilage, forming a methylation quantitative trait locus (mQTL). The mQTL is less pronounced in foetal cartilage (5/16 CpGs). The reporter assay revealed that the CpGs reside within a transcriptional regulator. Epigenetic editing to increase their DNAm resulted in altered expression of the full-length and N-terminal transcript isoforms of WWP2. No changes in expression were observed for the C-terminal isoform of WWP2 or for miR-140.

CONCLUSIONS

As far as we are aware, this is the first experimental demonstration of an OA association signal targeting specific transcript isoforms of a gene. The WWP2 isoforms encode proteins with varying substrate specificities for the components of the TGFβ signaling pathway. Future analysis should focus on the substrates regulated by the two WWP2 isoforms that are the targets of this genetic risk.

The role of WWP1 and WWP2 in bone/cartilage development and diseases

Bone and cartilage diseases are often associated with trauma and senescence, manifested as pain and limited mobility. The repair of bone and cartilage lesion by mesenchymal stem cells is regulated by various transcription factors. WW domain-containing protein 1 (WWP1) and WW domain-containing protein 2 (WWP2) are named for WW domain which recognizes PPXY (phono Ser Pro and Pro Arg) motifs of substrate. WWP1and WWP2 are prominent components of the homologous to the E6-AP carboxyl terminus (HECT) subfamily, a group of the ubiquitin ligase. Recently, some studies have found that WWP1 and WWP2 play an important role in the pathogenesis of bone and cartilage diseases and regulate the level and the transactivation of various transcription factors through ubiquitination. Therefore, this review summarizes the distribution and effects of WWP1 and WWP2 in the development of bone and cartilage, discusses the potential mechanism and therapeutic drugs in bone and cartilage diseases such as osteoarthritis, fracture, and osteoporosis.

Versatile RNA: overlooked gems of the transcriptome

The critical role of RNA, its use and targetability concerning different aspects of human health are gaining more attention because our understanding of the versatility of RNA has dramatically evolved over the last decades. We now appreciate that RNA is far more critical than a messenger molecule and possesses many complicated functions. As a multifunctional molecule with its sequence, flexible structures and enzymatic abilities, RNA is genuinely powerful. Mammalian transcriptomes consist of a dynamically regulated plethora of coding and noncoding RNA types. However, some aspects of RNA metabolism remain to be explored. In this Viewpoint, we focus on the transcriptome's unconventional and possibly overlooked aspects to emphasize the importance of RNA in mammalian systems.

Reassessment of miRNA variant (isomiRs) composition by small RNA sequencing

IsomiRs, sequence variants of mature microRNAs, are usually detected and quantified using high-throughput sequencing. Many examples of their biological relevance have been reported, but sequencing artifacts identified as artificial variants might bias biological inference and therefore need to be ideally avoided. We conducted a comprehensive evaluation of 10 different small RNA sequencing protocols, exploring both a theoretically isomiR-free pool of synthetic miRNAs and HEK293T cells. We calculated that, with the exception of two protocols, less than 5% of miRNA reads can be attributed to library preparation artifacts. Randomized-end adapter protocols showed superior accuracy, with 40% of true biological isomiRs. Nevertheless, we demonstrate concordance across protocols for selected miRNAs in non-templated uridyl additions. Notably, NTA-U calling and isomiR target prediction can be inaccurate when using protocols with poor single-nucleotide resolution. Our results highlight the relevance of protocol choice for biological isomiRs detection and annotation, which has key potential implications for biomedical applications.

Transcription analyses of differentially expressed mRNAs, lncRNAs, circRNAs, and miRNAs in the growth plate of rats with glucocorticoid-induced growth retardation

Background

Glucocorticoids (GCs) are commonly used to treat autoimmune diseases and malignancies in children and adolescents. Growth retardation is a common adverse effect of GC treatment in pediatric patients. Accumulating evidence indicates that non-coding RNAs (ncRNAs) are involved in the pathogenesis of glucocorticoid-induced growth retardation (GIGR), but the roles of specific ncRNAs in growth remain largely unknown.

Methods

In this study, 2-week-old male Sprague-Dawley rats had been treated with 2 mg/kg/d of dexamethasone for 7 or 14 days, after which the growth plate tissues were collected for high-throughput RNA sequencing to identify differentially expressed mRNAs, lncRNAs, circRNAs, and miRNAs in GIGR rats.

Results

Transcriptomic analysis identified 1,718 mRNAs, 896 lncRNAs, 60 circRNAs, and 72 miRNAs with different expression levels in the 7d group. In the 14d group, 1,515 mRNAs, 880 lncRNAs, 46 circRNAs, and 55 miRNAs with differential expression were identified. Four mRNAs and four miRNAs that may be closely associated with the development of GIGR were further validated by real-time quantitative fluorescence PCR. Function enrichment analysis indicated that the PI3K-Akt signaling pathway, NF-kappa B signaling pathway, and TGF-β signaling pathway participated in the development of the GIGR. Moreover, the constructed ceRNA networks suggested that several miRNAs (including miR-140-3p and miR-127-3p) might play an important role in the pathogenesis of GIGR.

Conclusions

These results provide new insights and important clues for exploring the molecular mechanisms underlying GIGR.

miR-140-5p and miR-140-3p: Key Actors in Aging-Related Diseases?

microRNAs (miRNAs) are small single strand non-coding RNAs and powerful gene expression regulators. They mainly bind to the 3′UTR sequence of targeted mRNA, leading to their degradation or translation inhibition. miR-140 gene encodes the pre-miR-140 that generates the two mature miRNAs miR-140-5p and miR-140-3p. miR-140-5p/-3p have been associated with the development and progression of cancers, but also non-neoplastic diseases. In aging-related diseases, miR-140-5p and miR-140-3p expressions are modulated. The seric levels of these two miRNAs are used as circulating biomarkers and may represent predictive tools. They are also considered key actors in the pathophysiology of aging-related diseases. miR-140-5p/-3p repress targets regulating cell proliferation, apoptosis, senescence, and inflammation. This work focuses on the roles of miR-140-3p and miR-140-5p in aging-related diseases, details their regulation (i.e., by long non-coding RNA), and reviews the molecular targets of theses miRNAs involved in aging pathophysiology.

Reversing the miRNA -5p/-3p stoichiometry reveals physiological roles and targets of miR-140 miRNAs

The chondrocyte-specific miR-140 miRNAs are necessary for normal endochondral bone growth in mice. miR-140 deficiency causes dwarfism and craniofacial deformity. However, the physiologically important targets of miR-140 miRNAs are still unclear. The miR-140 gene (Mir140) encodes three chondrocyte-specific microRNAs, miR-140-5p, derived from the 5' strand of primary miR-140, and miR140-3p.1 and -3p.2, derived from the 3' strand of primary miR-140. miR-140-3p miRNAs are 10 times more abundant than miR-140-5p likely due to the nonpreferential loading of miR-140-5p to Argonaute proteins. To differentiate the role of miR-140-5p and -3p miRNAs in endochondral bone development, two distinct mouse models, miR140-C > T, in which the first nucleotide of miR-140-5p was altered from cytosine to uridine, and miR140-CG, where the first two nucleotides of miR-140-3p were changed to cytosine and guanine, were created. These changes are expected to alter Argonaute protein loading preference of -5p and -3p to increase -5p loading and decrease -3p loading without changing the function of miR140-5p. These models presented a mild delay in epiphyseal development with delayed chondrocyte maturation. Using RNA-sequencing analysis of the two models, direct targets of miR140-5p, including Wnt11, were identified. Disruption of the predicted miR140-5p binding site in the 3' untranslated region of Wnt11 was shown to increase Wnt11 mRNA expression and caused a modest acceleration of epiphyseal development. These results show that the relative abundance of miRNA-5p and -3p can be altered by changing the first nucleotide of miRNAs in vivo, and this method can be useful to identify physiologically important miRNA targets.

CircSCAPER contributes to IL-1β-induced osteoarthritis in vitro via miR-140-3p/EZH2 axis

Aims

Circular RNA (circRNA) S-phase cyclin A-associated protein in the endoplasmic reticulum (ER) (circSCAPER, ID: hsa_circ_0104595) has been found to be highly expressed in osteoarthritis (OA) patients and has been associated with the severity of OA. Hence, the role and mechanisms underlying circSCAPER in OA were investigated in this study.

Methods

In vitro cultured human normal chondrocyte C28/I2 was exposed to interleukin (IL)-1β to mimic the microenvironment of OA. The expression of circSCAPER, microRNA (miR)-140-3p, and enhancer of zeste homolog 2 (EZH2) was detected using quantitative real-time polymerase chain reaction and Western blot assays. The extracellular matrix (ECM) degradation, proliferation, and apoptosis of chondrocytes were determined using Western blot, cell counting kit-8, and flow cytometry assays. Targeted relationships were predicted by bioinformatic analysis and verified using dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. The levels of phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway-related protein were detected using Western blot assays.

Results

CircSCAPER was highly expressed in OA cartilage tissues and IL-1β-induced chondrocytes. Knockdown of circSCAPER reduced IL-1β-evoked ECM degradation, proliferation arrest, and apoptosis enhancement in chondrocytes. Mechanistically, circSCAPER directly bound to miR-140-3p, and miR-140-3p inhibition reversed the effects of circSCAPER knockdown on IL-1β-induced chondrocytes. miR-140-3p was verified to target EZH2, and overexpression of miR-140-3p protected chondrocytes against IL-1β-induced dysfunction via targeting EZH2. Additionally, we confirmed that circSCAPER could regulate EZH2 through sponging miR-140-3p, and the circSCAPER/miR-140-3p/EZH2 axis could activate the PI3K/AKT pathway.

Conclusion

CircSCAPER promoted IL-1β-evoked ECM degradation, proliferation arrest, and apoptosis enhancement in chondrocytes via regulating miR-140-3p/EZH2 axis, which gained a new insight into the pathogenesis of OA.

Cite this article: Bone Joint Res 2022;11(2):61–72.

Osteoarthritis year in review: genetics, genomics, epigenetics

OBJECTIVE

In this review, we have highlighted the advances over the past year in genetics, genomics and epigenetics in the field of osteoarthritis (OA).

METHODS

A literature search of PubMed was performed using the criteria: "osteoarthritis" and one of the following terms "genetic(s), genomic(s), epigenetic(s), polymorphism, noncoding ribonucleic acid (RNA), microRNA, long noncoding RNA, lncRNA, circular RNA, RNA sequencing (RNA-seq), single cell sequencing, transcriptomics, or deoxyribonucleic acid (DNA) methylation between April 01, 2020 and April 30, 2021.

RESULTS

In total we identified 765 unique publications, which eventually reduced to 380 of relevance to the field as judged by two assessors. Many of these studies included multiple search terms. We summarised advances relating to genetics, functional genetics, genomics and epigenetics, focusing on our personal key papers during the year.

CONCLUSIONS

This year few studies have identified new genetic variants contributing to OA susceptibility, but a focus has been on refining risk loci or their functional validation. The use of new technologies together with investigating the cross-talk between multiple tissue types, greater sample sizes and/or better patient classification (OA subtypes) will continue to increase our knowledge of disease mechanisms and progress towards understanding and treating OA.

microRNA-140-3p modulates invasiveness, motility, and extracellular matrix adhesion of breast cancer cells by targeting syndecan-4

Syndecan-4, a predicted target of the microRNA miR-140-3p, plays an important role in multiple steps of tumor progression and is the second most abundant heparan sulfate proteoglycan produced by breast carcinoma cell lines. To investigate the potential functional relationship of miR-140-3p and syndecan-4, MDA-MB-231, SKBR3, and MCF-7 breast cancer (BC) cells were transiently transfected with pre-miR-140-3p, syndecan-4 small interfering RNAJ, or control reagents, respectively. Altered cell behavior was monitored by adhesion, migration, and invasion chamber assays. Moreover, the prognostic value of syndecan-4 was assessed by Kaplan-Maier Plotter analysis of gene expression data from tumor samples of 4929 patients. High expression of syndecan-4 was associated with better relapse-free survival in the whole collective of BC patients, but correlated with a worse survival in the subgroup of estrogen receptor negative and estrogen/progesterone-receptor negative patients. miR-140-3p expression was associated with improved survival irrespective of hormone receptor status. miR-140-3p overexpression induced posttranscriptional downregulation of syndecan-4, as demonstrated by quantitative real-time PCR (qPCR), flow cytometry, and luciferase assays, resulting in decreased BC cell migration and matrigel invasiveness. Furthermore, miR-140-3p overexpression and syndecan-4 silencing increased the adhesion of BC to fibronectin and laminin. qPCR analysis demonstrated that syndecan-4 silencing leads to altered gene expression of adhesion-related molecules, such as fibronectin and focal adhesion kinase, as well as in the gene expression of the proinvasive factors matrix metalloproteinase 2 and heparanase (also known as HPSE). We conclude that syndecan-4 is a novel target of miR-140-3p that regulates BC cell invasiveness and cell-matrix interactions in the tumor microenvironment.

Overview of host miRNA properties and their association with epigenetics, long non-coding RNAs, and Xeno-infectious factors

MicroRNA-derived structures play impressive roles in various biological processes. So dysregulation of miRNAs can lead to different human diseases. Recent studies have extended our comprehension of the control of miRNA function and features. Here, we overview some remarkable miRNA properties that have potential implications for the miRNA functions, including different variants of a miRNA called isomiRs, miRNA arm selection/arm switching, and the effect of these factors on miRNA target selection. Besides, we review some aspects of miRNA interactions such as the interaction between epigenetics and miRNA (different miRNAs and their related processing enzymes are epigenetically regulated by multiple DNA methylation enzymes. moreover, DNA methylation could be controlled by diverse mechanisms related to miRNAs), direct and indirect crosstalk between miRNA and lnc (Long Non-Coding) RNAs as a further approach to conduct intercellular regulation called "competing endogenous RNA" (ceRNA) that is involved in the pathogenesis of different diseases, and the interaction of miRNA activities and some Xeno-infectious (virus/bacteria/parasite) factors, which result in modulation of the pathogenesis of infections. This review provides some related studies to a better understanding of miRNA involvement mechanisms and overcoming the complexity of related diseases that may be applicable and useful to prognostic, diagnostic, therapeutic purposes and personalized medicine in the future.

Recent progress on the role of miR-140 in cartilage matrix remodelling and its implications for osteoarthritis treatment

Cartilage matrix remodelling homeostasis is a crucial factor in maintaining cartilage integrity. Loss of cartilage integrity is a typical characteristic of osteoarthritis (OA). Strategies aimed at maintaining cartilage integrity have attracted considerable attention in the OA research field. Recently, a series of studies have suggested dual functions of microRNA-140 (miR-140) in cartilage matrix remodelling. Here, we discuss the significance of miR-140 in promoting cartilage formation and inhibiting degeneration. Additionally, we focused on the role of miR-140 in the chondrogenesis of mesenchymal stem cells (MSCs). Of note, we carefully reviewed recent advances in MSC exosomes for miRNA delivery in OA treatment.