Long Non-coding RNA MALAT1 Is Depleted With Age in Skeletal Muscle in vivo and MALAT1 Silencing Increases Expression of TGF-β1 in vitro

Ling Ruan,Meghan Mcgee-Lawrence,Sadanand Fulzele,Carlos M Isales,William D Hill,Mark W Hamrick,Emily Parker,Andrew Kent,Bharati Mendhe

doi:10.3389/fphys.2021.742004

Ling Ruan, Meghan Mcgee-Lawrence + Show 7 more

Open Access

https://doi.org/10.3389/fphys.2021.742004

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Abstract

Long non-coding RNAs (lncRNAs) are thought to function as “sponges” for microRNAs, but a role for such competing endogenous RNAs (ceRNAs) in muscle aging is not well understood. We therefore examined in skeletal muscles of young (4–6 months) and aged (22–24) male and female mice the expression of lncRNA MALAT1, which is predicted in silico to bind the senescence-associated microRNA miR-34a-5p. Results indicate a significant decrease in lncRNA MALAT1 expression in mouse skeletal muscle with age that coincides with an age-related increase in miR-34a-5p expression. In vitro studies using mouse C2C12 myoblasts demonstrate that MALAT1 silencing using siRNA increases miR-34a expression, consistent with a role for MALAT1 as an inhibitor of miR-34a-5p activity. Levels of reactive oxygen species (ROS) are known to increase in muscle with age, and so we treated C2C12 cells with hydrogen peroxide (10 and 100 μM) to examine changes in MALAT1 expression. MALAT1 expression decreased significantly with H2O2 treatment, but this effect was attenuated with p53 siRNA. Finally, miR-34a-5p is implicated in tissue fibrosis, and so we assessed the expression of TGF-β1 after MALAT1 silencing. MALAT1 siRNA significantly increased the expression of TGF-β1 in C2C12 cells. These findings suggest that age-related fibrosis and muscle atrophy mediated by ROS may result at least in part from an increase in miR-34a bioavailability resulting from a decline in miR-34a “sponging” due to ceRNA MALAT1 depletion. Crosstalk between MALAT1 and miR-34a may therefore represent a therapeutic target for improving muscle function with aging.

Highlights

The loss of muscle mass with age, or sarcopenia, is a significant clinical concern as declines in muscle mass are associated with frailty and disability among older adults
Cellular senescence and oxidative stress are associated with fibrosis in a number of different organs and tissues, and so we examined effects of MALAT1 silencing on TGF-β1 and expression
In vitro experiments utilizing mouse C2C12 myoblasts transfected with MALAT1 siRNA show that normal myotube maturation and differentiation is impaired with MALAT1

Summary

Introduction

The loss of muscle mass with age, or sarcopenia, is a significant clinical concern as declines in muscle mass are associated with frailty and disability among older adults. Previous research suggests that lncRNAs may play important roles in muscle growth and muscle cell differentiation. The recently identified long non-coding RNA Chronos was found to be upregulated with age, and Chronos inhibition can induce myofiber hypertrophy both in vitro and in vivo (Neppl et al, 2017). Additional lncRNAs such as Neat, Malat, Sra, Meg, and LncMyoD show distinct patterns of expression during myoblast differentiation, suggesting key roles for these non-coding RNAs in muscle fiber development and maturation (Butchart et al, 2016)

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