# Mechanotransduction and the Regulation of Skeletal Muscle Mass

> **NIH NIH R56** · UNIVERSITY OF WISCONSIN-MADISON · 2022 · $270,397

## Abstract

Project Summary / Abstract
Mechanical signals play a major role in the regulation of skeletal muscle mass, and the maintenance of muscle
mass contributes significantly to disease prevention and quality of life. Although the link between mechanical
signals and the regulation of muscle mass has been recognized for decades, the mechanisms that control this
process remain far from defined. For instance, most studies indicate that the mechanically induced growth of
skeletal muscle is driven by an increase in the size of the existing myofibers rather than an increase in the
number of myofibers. Moreover, current models assert that the increase in myofiber size is mediated by an
increase in the balance between the rates of protein synthesis and protein degradation which, in turn, leads to
the accumulation of newly synthesized proteins (NSPs) and the concomitant structural changes that drive the
growth response. For example, numerous studies have shown that an increase in mechanical loading can lead
to microstructural changes such as the radial growth of myofibers (i.e., hypertrophy). Surprisingly, however, the
ultrastructural adaptations that underlie the microstructural changes have not been defined. Indeed, even the
most basic questions such as whether the radial growth of myofibers is mediated by an increase in the size of
the myofibrils and/or an increase in the number of myofibrils have not been answered. Likewise, the location(s)
in which NSPs accumulate during the mechanically induced growth of skeletal muscle (i.e., the sites of growth)
are not known. As such, one of the major goals of this project is to fill these gaps in knowledge. Another major
goal of this project is to develop a better understanding of the signaling mechanisms that control the different
aspects of mechanically induced growth. For instance, our previous work on this project established that
signaling through mTORC1 plays a central role in the process through which mechanical stimuli induce the radial
growth of myofibers. However, our preliminary data indicate that the longitudinal growth of myofibers can also
substantially contribute to the mechanically induced accretion of muscle mass, yet, unlike the radial growth of
myofibers, the longitudinal growth of myofibers does not require signaling through mTORC1. In other words, our
preliminary data suggest that the radial and longitudinal growth of myofibers are regulated by distinct signaling
mechanisms, and the studies proposed in this project will test this and related concepts. Specifically, we will use
two distinct but complementary murine models of mechanical load-induced growth, along with a combination of
traditional and cutting-edge technologies, to: i) comprehensively define the microstructural and ultrastructural
adaptations that occur during the mechanically induced growth of skeletal muscle; ii) identify where NSPs
accumulate during these different types of adaptations; and iii) determine which, if any, of these phe...

## Key facts

- **NIH application ID:** 10695331
- **Project number:** 2R56AR057347-11
- **Recipient organization:** UNIVERSITY OF WISCONSIN-MADISON
- **Principal Investigator:** TROY A HORNBERGER
- **Activity code:** R56 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $270,397
- **Award type:** 2
- **Project period:** 2022-09-19 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10695331

## Citation

> US National Institutes of Health, RePORTER application 10695331, Mechanotransduction and the Regulation of Skeletal Muscle Mass (2R56AR057347-11). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10695331. Licensed CC0.

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