Satellite cells are skeletal muscle stem cells essential for muscle regeneration. The activation of satellites cells is regulated by a series of transcription factors such as Pax7, Myf5, Myod, Myogenin. These factors regulate the myogenic identity of the cells in both proliferation and differentiation states. Oxidative metabolism and reactive oxygen species (ROS) play an important role in the regulation of the activation and niche maintenance of the stem cells. Increased levels of ROS induce lipid peroxidation and generation of toxic aldehydes, such as the 4-hydroxy-2-nonenal (4-HNE). 4-HNE is the major by-product of lipid peroxidation and highly reactive with macromolecules including protein, lipids and DNA. Intracellular accumulation of 4-HNE adducts has a negative impact on the biology of both somatic and progenitor cells. Therefore, enzymes responsible for the detoxification of 4-HNE that accumulate inside the cell are critical for the maintenance of homeostasis. The mitochondrial enzyme aldehyde dehydrogenase 2 (ALDH2) is one of the main enzymes responsible for removing this toxic aldehydes. Reduction in ALDH2 function and consequent accumulation of 4-HNE is related to the establishment and progression of many diseases. However, the role of 4-HNE metabolism in the biology of satellite cells, as well as its contribution to skeletal muscle regeneration is unclear. In this context, this project aims to characterize the metabolic profile of satellite cells/myoblasts/myotubes from WT and ALDH2 knockin mutant mice (loss of function model), as well as their susceptibility to 4-HNE overload. Our preliminary results demonstrate that exogenous 4-HNE causes a reduction in oxygen consumption and proliferation rate, increased necrosis and apoptosis, as well as cell cycle G2/M arrest in C2C12 myoblasts. Of interest, ALDH2 loss of function has a negative impact on myoblasts proliferation and oxygen consumption (in culture), but does not change the number of satellite cells (in vivo). In the current proposal we plan to analyze the impact of 4-HNE load on the frequency of myoblast fusion and myotubes formation (in culture). To this end, we will use myoblasts in culture isolated from WT and ALDH2 knockin mice. Moreover, we will quantify the number of satellite cells in skeletal muscle from WT and ALDH2 knockin mice. All biological material used in this project (cells and tissue from WT and ALDH2 knockin mice) will be collected in Brazil and shipped to Dr. Wang's lab for further analysis.
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