Major Advisor: Elizabeth Vargis
In Vitro Modeling of Microgravity-Induced Muscle Atrophy and Spaceflight Radiation
Charles Harding, Jon Takemoto, Elizabeth Vargis
Muscular atrophy, defined as the loss of muscle tissue, is a serious issue for immobilized patients on Earth and in human spaceflight, where microgravity prevents normal muscle loading. A major factor in muscular atrophy is oxidative stress, which is amplified not only by muscle disuse but also by the increased levels of ionizing radiation in spaceflight. Additionally, elevated radiation exposure can damage DNA, increasing cancer risk.
To model oxidative stress and DNA damage generated by conditions on the International Space Station, murine C2C12 myoblasts were cultured in a rotary cell culture system irradiated by cesium-137. Changes due to the spaceflight model were characterized with fluorescent imaging for viability and DNA damage, amino acid analysis for cell metabolism, and enzyme-linked immunosorbent assay for heme oxygenase 1, a marker of oxidative stress.
Hydrogel encapsulation was compared against microcarrier beads as a substrate for C2C12 muscle cells. Microcarrier beads are commonly used for suspension culture of adherent cell lines. However, the irregular monolayer that forms on the surface of clustered microcarriers may not accurately model solid muscle tissue. In contrast, encapsulation of muscle cells in an alginate hydrogel creates a three-dimensional tissue model of consistent size and cell density.
Preliminary results indicate minor DNA damage in cells exposed to 20 μCi cesium-137 for 15 days with no significant differences in viability. Exposure to radiation and simulated microgravity is expected to induce a stress response from reactive oxygen species, increasing intracellular heme oxygenase 1. Metabolic processes that result in the release of alanine are expected to decrease in the presence of radiation and simulated microgravity. We anticipate that radiation will exacerbate the atrophic effects of microgravity on muscle cells. Simulation of microgravity and spaceflight radiation will provide a valuable platform for drug discovery and an understanding of the progression of normal to a disease state.