Expression patterns of regulatory lncRNAs and miRNAs in muscular atrophy models induced by starvation in vitro and in vivo

The Functional Role of Long Non-Coding RNA in Myogenesis and Skeletal Muscle Atrophy

Skeletal muscle is a pivotal organ in humans that maintains locomotion and homeostasis. Muscle atrophy caused by sarcopenia and cachexia, which results in reduced muscle mass and impaired skeletal muscle function, is a serious health condition that decreases life longevity in humans. Recent studies have revealed the molecular mechanisms by which long non-coding RNAs (lncRNAs) regulate skeletal muscle mass and function through transcriptional regulation, fiber-type switching, and skeletal muscle cell proliferation. In addition, lncRNAs function as natural inhibitors of microRNAs and induce muscle hypertrophy or atrophy. Intriguingly, muscle atrophy modifies the expression of thousands of lncRNAs. Therefore, although their exact functions have not yet been fully elucidated, various novel lncRNAs associated with muscle atrophy have been identified. Here, we comprehensively review recent knowledge on the regulatory roles of lncRNAs in skeletal muscle atrophy. In addition, we discuss the issues and possibilities of targeting lncRNAs as a treatment for skeletal muscle atrophy and muscle wasting disorders in humans.

TNF-α Induced Myotube Atrophy in C2C12 Cell Line Uncovers Putative Inflammatory-Related lncRNAs Mediating Muscle Wasting

Background: Muscle atrophy is a complex catabolic condition developing under different inflammatory-related systemic diseases resulting in wasting of muscle tissue. While the knowledge of the molecular background of muscle atrophy has developed in recent years, how the atrophic conditions affect the long non-coding RNA (lncRNAs) machinery and the exact participation of the latter in the mediation of muscle loss are still unknown. The purpose of the study was to assess how inflammatory condition developing under the tumor necrosis factor alpha (TNF-α) treatment affects the lncRNAs’ expression in a mouse skeletal muscle cell line. Materials and method: A C2C12 mouse myoblast cell line was treated with TNF-α to develop atrophy, and inflammatory-related lncRNAs mediating muscle loss were identified. Bioinformatics was used to validate and analyze the discovered lncRNAs. The differences in their expression under different TNF-α concentrations and treatment times were investigated. Results: Five lncRNAs were identified in a discovery set as atrophy related and then validated. Three lncRNAs, Gm4117, Ccdc41os1, and 5830418P13Rik, were selected as being significant for inflammatory-related myotube atrophy. Dynamics changes in the expression of lncRNAs depended on both TNF-α concentration and treatment time. Bioinformatics analysis revealed the mRNA and miRNA target for selected lncRNAs and their putative involvement in the molecular processes related to muscle atrophy. Conclusions: The inflammatory condition developing in the myotube under the TNF-α treatment affects the alteration of lncRNAs’ expression pattern. Experimental and bioinformatics testing suggested the prospective role of lncRNAs in the mediation of muscle loss under an inflammatory state.

Non-coding RNA basis of muscle atrophy

Muscle atrophy is a common complication of many chronic diseases including heart failure, cancer cachexia, aging, etc. Unhealthy habits and usage of hormones such as dexamethasone can also lead to muscle atrophy. However, the underlying mechanisms of muscle atrophy are not completely understood. Non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long ncRNAs (lncRNAs), and circular RNAs (circRNAs), play vital roles in muscle atrophy. This review mainly discusses the regulation of ncRNAs in muscle atrophy induced by various factors such as heart failure, cancer cachexia, aging, chronic obstructive pulmonary disease (COPD), peripheral nerve injury (PNI), chronic kidney disease (CKD), unhealthy habits, and usage of hormones; highlights the findings of ncRNAs as common regulators in multiple types of muscle atrophy; and summarizes current therapies and underlying mechanisms for muscle atrophy. This review will deepen the understanding of skeletal muscle biology and provide new strategies and insights into gene therapy for muscle atrophy.

Mitochondria and metabolic transitions in cardiomyocytes: lessons from development for stem cell-derived cardiomyocytes

Current methods to differentiate cardiomyocytes from human pluripotent stem cells (PSCs) inadequately recapitulate complete development and result in PSC-derived cardiomyocytes (PSC-CMs) with an immature or fetal-like phenotype. Embryonic and fetal development are highly dynamic periods during which the developing embryo or fetus is exposed to changing nutrient, oxygen, and hormone levels until birth. It is becoming increasingly apparent that these metabolic changes initiate developmental processes to mature cardiomyocytes. Mitochondria are central to these changes, responding to these metabolic changes and transitioning from small, fragmented mitochondria to large organelles capable of producing enough ATP to support the contractile function of the heart. These changes in mitochondria may not simply be a response to cardiomyocyte maturation; the metabolic signals that occur throughout development may actually be central to the maturation process in cardiomyocytes. Here, we review methods to enhance maturation of PSC-CMs and highlight evidence from development indicating the key roles that mitochondria play during cardiomyocyte maturation. We evaluate metabolic transitions that occur during development and how these affect molecular nutrient sensors, discuss how regulation of nutrient sensing pathways affect mitochondrial dynamics and function, and explore how changes in mitochondrial function can affect metabolite production, the cell cycle, and epigenetics to influence maturation of cardiomyocytes.

Network Analysis of Local Gene Regulators in Arabidopsis thaliana under Spaceflight Stress

Spaceflight microgravity affects normal plant growth in several ways. The transcriptional dataset of the plant model organism Arabidopsis thaliana grown in the international space station is mined using graph-theoretic network analysis approaches to identify significant gene transcriptions in microgravity essential for the plant’s survival and growth in altered environments. The photosynthesis process is critical for the survival of the plants in spaceflight under different environmentally stressful conditions such as lower levels of gravity, lesser oxygen availability, low atmospheric pressure, and the presence of cosmic radiation. Lasso regression method is used for gene regulatory network inferencing from gene expressions of four different ecotypes of Arabidopsis in spaceflight microgravity related to the photosynthetic process. The individual behavior of hub-genes and stress response genes in the photosynthetic process and their impact on the whole network is analyzed. Logistic regression on centrality measures computed from the networks, including average shortest path, betweenness centrality, closeness centrality, and eccentricity, and the HITS algorithm is used to rank genes and identify interactor or target genes from the networks. Through the hub and authority gene interactions, several biological processes associated with photosynthesis and carbon fixation genes are identified. The altered conditions in spaceflight have made all the ecotypes of Arabidopsis sensitive to dehydration-and-salt stress. The oxidative and heat-shock stress-response genes regulate the photosynthesis genes that are involved in the oxidation-reduction process in spaceflight microgravity, enabling the plant to adapt successfully to the spaceflight environment.

Role of miRNAs and lncRNAs in dexamethasone-induced myotube atrophy in vitro

Skeletal muscle atrophy is a well-known adverse effect of long-term glucocorticoid (GC) therapy. MicroRNAs (miRNAs or miRs) and long non-coding RNAs (lncRNAs) are important regulators in a number of physiological and pathological processes. However, the role of miRNAs and lncRNAs in the regulation of GC-treated muscle atrophy remains poorly understood. In the current study, muscular atrophy was induced and the results indicated that C2C12 myotubes were thinner than normal, while the expression of muscle ring finger protein 1 and Atrogin-1 was increased. The expression of nine miRNAs and seven lncRNAs associated with proliferation and differentiation were analyzed in a dexamethasone (DEX)-induced muscle atrophy cell model. In addition, the mRNA expression of the downstream targets of lncRNAs that were differentially expressed between DEX-treated and control cells were determined. The results indicated that the expression of miR-133a, miR-133b, miR-206 and five lncRNAs (increased Atrolnc-1, Dum, MAR1, linc-MD1 and decreased Myolinc) were significantly different between the DEX and the control group. Furthermore, the relative mRNA expression of Wnt5a and MyoD was significantly different between the two groups. The results of the current study indicated that some important miRNAs and lncRNAs are associated with DEX-induced muscle atrophy and have the potential to be further developed as a diagnostic tool for this condition.

Regulation of Skeletal Muscle Atrophy in Cachexia by MicroRNAs and Long Non-coding RNAs

Skeletal muscle atrophy is a common complication of cachexia, characterized by progressive bodyweight loss and decreased muscle strength, and it significantly increases the risks of morbidity and mortality in the population with atrophy. Numerous complications associated with decreased muscle function can activate catabolism, reduce anabolism, and impair muscle regeneration, leading to muscle wasting. microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), types of non-coding RNAs, are important for regulation of skeletal muscle development. Few studies have specifically identified the roles of miRNAs and lncRNAs in cellular or animal models of muscular atrophy during cachexia, and the pathogenesis of skeletal muscle wasting in cachexia is not entirely understood. To develop potential approaches to improve skeletal muscle mass, strength, and function, a more comprehensive understanding of the known key pathophysiological processes leading to muscular atrophy is needed. In this review, we summarize the known miRNAs, lncRNAs, and corresponding signaling pathways involved in regulating skeletal muscle atrophy in cachexia and other diseases. A comprehensive understanding of the functions and mechanisms of miRNAs and lncRNAs during skeletal muscle wasting in cachexia and other diseases will, therefore, promote therapeutic treatments for muscle atrophy.