Modeling the direct effects of TNFα upon drug-induced toxicity with in human, tissue-engineered myobundles.
A number of significant muscle diseases, such as cachexia, sarcopenia, systemic chronic inflammation, along with inflammatory myopathies share TNFα-mediated inflammation in their pathogenesis. TNFα-based inflammatory stress may directly sensitize skeletal muscle to drug-induced toxicity. The two main difficulties when assessing the role of TNFα on skeletal muscle drug toxicity using in vitro methodology are first creating an experimental model that recapitulates the basal functional responses of human skeletal muscle and second validating that the experimental model accurately represents human skeletal muscle response to TNFα. The aim of this research is to resolve these two difficulties.
We first assayed the bioenergetic profile of engineered three-dimensional human skeletal muscle myobundles to probe mitochondrial health and compared its result to muscle fatigue. Then engineered a perfusion system to measure respiration under basal conditions and electrical stimulation. Finally, to assess the effect of TNFα-induced inflammation on drug responses, we engineered 3D, human skeletal myobundles, chronically exposed them the TNFα during maturation, and measured the combined response of TNFα and the chemotherapeutic, doxorubicin, on muscle function. We concluded that the human myobundles reproduce normal muscle metabolism under both basal and maximal energy demand conditions enabling the detection of drug-induced mitochondrial toxicity. The bioenergetic health index, which is a measure of normal oxidative mitochondrial function, was inversely correlated with the extent of fatigue. The relationship between mitochondrial function and physiological muscle function suggests that the mitochondrial dysfunction produced the fatigue. The custom perfusion chamber was validated to accurately measure oxygen uptake during basal and electrical stimulation conditions. This in vitro non-invasive tool enables the investigation of human muscle physiology during exercise. Utilizing the myobundle platform, a synergistic effect of the combination of TNFα and 10nM doxorubicin was found on contractile force production. Overall, we demonstrated the feasibility of the in vitro 3D, human muscle inflammatory system to act as a drug-toxicity testing platform and validated assays to quantify drug-induced decrements in mitochondrial function.
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