Roles of mitophagy and the mitochondrial permeability transition in remodeling of cultured rat hepatocytes

In primary culture, hepatocytes dedifferentiate, and their cytoplasm undergoes remodeling. Here, our aim was to characterize changes of mitochondria duringremodeling. Hepatocytes were cultured 1 to 5 days in complete serum-containing Waymouth’s medium. In rat hepatocytes loaded with MitoTracker Green (MTG),tetramethylrhodamine methylester (TMRM), and/or LysoTracker Red (LTR), confocal microscopy revealed that mitochondria number and mass decreased by approximately50% between Day 1 and Day 3 of culture. As mitochondria disappeared, lysosomes/autophagosomes proliferated 5-fold. Decreased mitochondrial contentcorrelated with (a) decreased cytochrome c oxidase activity and mitochondrial number observed by electron microscopy and (b) a profound decrease of PGC-1α mRNAexpression. By contrast, mtDNA content per cell remained constant from the first to the third day of culture, although ethidium bromide (de novo mtDNA synthesis inhibitor)caused mtDNA to decrease by half from the first to the third culture day. As...