Expression Profiles Analysis and Functional Characterization of MicroRNA-660 in Skeletal Muscle Differentiation

Effect of resistance training on satellite cells in old mice - a transcriptome study : implications for sarcopenia

Aims

The decrease in the number of satellite cells (SCs), contributing to myofibre formation and reconstitution, and their proliferative capacity, leads to muscle loss, a condition known as sarcopenia. Resistance training can prevent muscle loss; however, the underlying mechanisms of resistance training effects on SCs are not well understood. We therefore conducted a comprehensive transcriptome analysis of SCs in a mouse model.

Methods

We compared the differentially expressed genes of SCs in young mice (eight weeks old), middle-aged (48-week-old) mice with resistance training intervention (MID+ T), and mice without exercise (MID) using next-generation sequencing and bioinformatics.

Results

After the bioinformatic analysis, the PI3K-Akt signalling pathway and the regulation of actin cytoskeleton in particular were highlighted among the top ten pathways with the most differentially expressed genes involved in the young/MID and MID+ T/MID groups. The expression of Gng5, Atf2, and Rtor in the PI3K-Akt signalling pathway was higher in the young and MID+ T groups compared with the MID group. Similarly, Limk1, Arhgef12, and Araf in the regulation of the actin cytoskeleton pathway had a similar bias. Moreover, the protein expression profiles of Atf2, Rptor, and Ccnd3 in each group were paralleled with the results of NGS.

Conclusion

Our results revealed that age-induced muscle loss might result from age-influenced genes that contribute to muscle development in SCs. After resistance training, age-impaired genes were reactivated, and age-induced genes were depressed. The change fold in these genes in the young/MID mice resembled those in the MID + T/MID group, suggesting that resistance training can rejuvenate the self-renewing ability of SCs by recovering age-influenced genes to prevent sarcopenia.

Cite this article: Bone Joint Res 2022;11(2):121–133.

MicroRNAs and the HIF/VEGF axis in ocular neovascular diseases

Ocular neovascular diseases, such as proliferative diabetic retinopathy, retinopathy of prematurity and neovascular age-related macular degeneration, are the leading causes of visual impairment worldwide. The hypoxia-inducible factors and vascular endothelial growth factors are key molecular promoters of ocular neovascularization. Moreover, the role of microRNAs as regulators of angiogenesis has been expanding, particularly hypoxia-associated microRNA; hypoxamiRs. This review provides a summary of hypoxamiRs that directly and specifically target HIF1A and VEGF mRNAs, thus critically involved in the regulation of ocular neovascular pathologies. The discussed microRNAs highlight putative diagnostic markers and therapeutic agents in choroidal and retinal angiogenic diseases, including proliferative diabetic retinopathy, retinopathy of prematurity and neovascular age-related macular degeneration.

Circulating skeletal muscle related microRNAs profile in Piedmontese cattle during different age

Piedmontese cattle is known for double-muscle phenotype. MicroRNAs (miRNAs) play important role as regulators in skeletal muscle physiological processes, and we hypothesize that plasma miRNAs expression profiles could be affected by skeletal muscle growth status related to age. Plasma samples of cattle were collected during four different ages from first week of life until the time of commercial end of the fattening period before slaughter. Small-RNA sequencing data analysis revealed the presence of 40% of muscle-related miRNAs among the top 25 highly expressed miRNAs and, 19 miRNAs showed differential expression too. Using qRT-PCR, we validated in a larger bovine population, miRNAs involved in skeletal muscle physiology pathways. Comparing new-born with the other age groups, miR-10b, miR-126-5p, miR-143 and miR-146b were significantly up-regulated, whereas miR-21-5p, miR-221, miR-223 and miR-30b-5p were significantly down-regulated. High expression levels of miR-23a in all the groups were found. Myostatin, a negative regulator of skeletal muscle hypertrophy, was predicted as the target gene for miR-23a and miR-126-5p and we demonstrated their direct binding. Correlation analysis revealed association between miRNAs expression profiles and animals’ weights along the age. Circulating miRNAs could be promising for future studies on their biomarker potentialities to beef cattle selection.

MiR-452 Regulates C2C12 Myoblast Proliferation and Differentiation via Targeting ANGPT1

microRNAs are a kind of endogenous, non-coding, single-strand small RNA. They have been reported as an important regulatory factor in skeletal myogenesis. In this study, miR-452 was selected from RNA high-throughput sequencing data to explore its regulatory role in myogenesis. Functionally, miR-452 overexpression could promote C2C12 myoblast proliferation while inhibiting myogenic differentiation. On the contrary, inhibition of miR-452 could suppress C2C12 myoblast proliferation but accelerate myogenic differentiation. Bioinformatics analysis and dual luciferase report assays showed that Angiopoietin 1 (ANGPT1), RB1, and CACNB4 were the potential target genes of miR-452. To further confirm the target relationship between ANGPT1, RB1, and CACNB4 with miR-452, the mRNA level and protein level of these genes were detected by using RT-qPCR and Western blot, respectively. Result analysis indicated that ANGPT1 was a target gene of miR-452. In addition, knockdown of ANGPT1 could obviously promote C2C12 myoblast proliferation but block their differentiation. In summary, these results demonstrated that miR-452 promoted C2C12 myoblast proliferation and inhibited their differentiation via targeting ANGPT1.

Chromatin accessibility is associated with the changed expression of miRNAs that target members of the Hippo pathway during myoblast differentiation

miRNAs reportedly participate in various biological processes, such as skeletal muscle proliferation and differentiation. However, the regulation of differentially expressed (DE) miRNAs and their function in myogenesis remain unclear. Herein, miRNA expression profiles and regulation during C2C12 differentiation were analyzed in relation to chromatin states by RNA-seq, ATAC-seq, and ChIP-seq. We identified 19 known and nine novel differentially expressed miRNAs at days 0, 1, 2, and 4. The expression of the differentially expressed miRNAs was related to the chromatin states of the 113 surrounding open chromatin regions defined by ATAC-seq peaks. Of these open chromatin regions, 44.25% were colocalized with MyoD/MyoG binding sites. The remainder of the above open chromatin regions were enriched with motifs of the myoblast-expressed AP-1 family, Ctcf, and Bach2 transcription factors (TFs). Additionally, the target genes of the above differentially expressed miRNAs were enriched primarily in muscle growth and development pathways, especially the Hippo signaling pathway. Moreover, via combining a loss-of-function assay with Q-PCR, western blotting, and immunofluorescence, we confirmed that the Hippo signaling pathway was responsible for C2C12 myoblast differentiation. Thus, our results showed that these differentially expressed miRNAs were regulated by chromatin states and affected muscle differentiation through the Hippo signaling pathway. Our findings provide new insights into the function of these differentially expressed miRNAs and the regulation of their expression during myoblast differentiation.

Characterization of lncRNA-miRNA-mRNA Network to Reveal Potential Functional ceRNAs in Bovine Skeletal Muscle

There is growing evidence that non-coding RNAs are emerging as critical regulators of skeletal muscle development. In order to reveal their functional roles and regulatory mechanisms, we constructed a lncRNA–miRNA–mRNA network according to the ceRNA (competitive endogenous RNA) theory, using our high-throughput sequencing data. Subsequently, the network analysis, GO (Gene Ontology) analysis, and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis were performed for functional annotation and exploration of lncRNA ceRNAs. The results uncovered a scale-free characteristics network which exhibited high functional specificity for bovine skeletal muscle development: co-expression lncRNAs were significantly enriched in muscle development related biological processes and the Wnt signaling pathway. Furthermore, GSEA (Gene Set Enrichment Analysis) indicated that the risk score has a tendency to associate with myogenesis, and differentially expressed RNAs were validated by qPCR, further confirming the credibility of our network. In summary, this study provides insights into lncRNA-mediated ceRNA function and mechanisms in bovine skeletal muscle development and will expand our understanding of lncRNA biology in mammals.

miR-27b regulates myogenic proliferation and differentiation by targeting Pax3 in goat

This study found that miR-27 is expressed in muscle and regulates muscle proliferation and differentiation. We explored the function and regulatory mechanism of miR-27b in goat muscle proliferation and differentiation. Compared with the Boer goat, higher expression of miR-27b was observed in all of the collected muscle tissues of Anhuai goat, excluding the kidney, whereas the opposite expression pattern was observed for Pax3, which showed lower expression in Anhuai goat. Expression of miR-27b decreased gradually during the proliferation of skeletal muscle satellite cells in Anhuai goat and increased during differentiation; however, the expression pattern of Pax3 was opposite. The regulatory activity of miR-27b demonstrated that miR-27b inhibited the proliferation of skeletal muscle satellite cells, but promoted their differentiation. Moreover, function research demonstrated that Pax3 negatively regulated myogenic differentiation of goat skeletal muscle satellite cells, but accelerated their proliferation. The results of a dual-luciferase reporter analysis showed that miR-27b directly targeted the 3’-untranslated regions of Pax3 mRNA, and western blot and immunofluorescence staining analyses showed that miR-27b inhibited expression of the Pax3 protein. In goats, miR-27b can regulate myogenic proliferation and differentiation by targeting Pax3.

Decoding Noncoding RNAs: Role of MicroRNAs and Long Noncoding RNAs in Ocular Neovascularization

Ocular neovascularization is a pathological sequel of multiple eye diseases. Based on the anatomical site into which the abnormal neovessels grow, ocular neovascularization can be categorized into corneal neovascularization, choroidal neovascularization, and retinal neovascularization. Each category is intractable, and may lead to blindness if not appropriately treated. However, the current therapeutic modalities, including laser photocoagulation, vitrectomy surgery, and anti-VEGF drugs, raise concerns due to limited efficacy, damage on retinal parenchyma and vasculature, and the patients' unresponsiveness to the treatments. Therefore, the in-depth study on pathogenesis of and the search for novel therapeutic targets to the ocular neovascularization are needed. During the last 10 years or so, a large number of literatures have emerged indicating a critical role of noncoding RNAs, particularly microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), in the pathogenesis and regulation of the ocular neovascularization. This review summarizes the current understanding of the biosynthesis and functions of the miRNAs and lncRNAs, the regulation of the miRNAs and lncRNAs in neovascular eye diseases, as well as the roles of these noncoding RNAs in the disease models of ocular neovascularization, in the hope that it could provide clues for the pathogenesis of and molecular targets to the ocular neovascularization.