Metabolic response to contraction in a 3D engineered muscle tissue model of aging

Title: Metabolic response to contraction in a 3D engineered muscle tissue model of aging Decreased skeletal muscle mass, specific force, increased overall fatty infiltration in the skeletal muscle, frailty and depressed energy maintenance are all associated with increased oxidative stress decline in mitochondrial

function and the development of sarcopenia with age. Mitochondrial response to exercise has been shown to be partially mediated through signaling control following muscle contraction. We have previously developed protocols to test mitochondrial function following high-intensity interval (HII) and low-intensity steady state (LISS)

muscle contraction in vivo. Following HII, young skeletal muscle mitochondria increased fatty acid oxidation compared to non-stimulated control muscle; however, aged muscle mitochondria decreased fatty acid oxidation. In contrast, following LISS, young skeletal muscle decreased fatty acid oxidation, whereas aged muscle

increased fatty acid oxidation. We also found that HII inhibits oxidation of glutamate in both stimulated and non- stimulated aged muscle, suggesting HII stimulates circulation of a factor capable of altering metabolism systemically. While longitudinal studies of skeletal muscle function in humans provide invaluable information on

the complex biology of aging and the impact on metabolism, muscle force, and fatiguability, they are often limiting for mechanistic tests. We have partnered with the Study of Muscle, Mobility and Aging (R01 AG059416) to obtain primary human myoblasts from well phenotyped older adults to develop a three-dimensional tissue model of

skeletal muscle aging. Developments in tissue engineering using primary cells purified directly from patients offer some of the best opportunities yet to link specific mechanistic tests of metabolic and muscle function to patient data. We will adapt our in vivo contraction protocols for in vitro use to test the hypothesis that aging impairs

metabolic response following contraction in human three-dimensional engineered muscle tissue (3D-EMT). We will test this hypothesis with two specific aims: 1) Examine the mitochondrial mechanisms of decreased metabolic response to muscle contraction in aged human 3D-EMT and 2) we will characterize the effect of aging on

adaptation to longitudinal contractile training of 3D-EMT in vitro. This proposal will capitalize on the stellar environment for aging and muscle research at University of Washington (UW). The UW houses a Nathan Shock Center of Excellence in the Basic Biology of Aging, the Center for Translational Muscle Research, Northwest

Metabolomics Research Center, and the Institute for Stem Cells and Regenerative Medicine. The research team comprises experts in the fields of muscle mechanics, mitochondrial function, metabolism, and tissue engineering and uniquely places them in a position to implement the development of this in vitro model and to successfully

test muscle and mitochondrial function.