Dynamic mitophagy trajectories hallmark brain aging.

Studies using mitophagy reporter mice have established steady-state landscapes of mitochondrial destruction in mammalian tissues, sparking intense interest in basal mitophagy. Yet how basal mitophagy is modified by healthy aging in diverse brain cell types has remained a mystery. We present a comprehensive spatiotemporal analysis of mitophagy and macroautophagy dynamics in the aging mammalian brain, reporting critical region- and cell-specific turnover trajectories in a longitudinal study. We demonstrate that the physiological regulation of mitophagy in the mammalian brain is cell-specific, dynamic and complex. Mitophagy increases significantly in the cerebellum and hippocampus during midlife, while remaining unchanged in the prefrontal cortex (PFC). Conversely, macroautophagy decreases in the hippocampus and PFC, but remains stable in the cerebellum. We also describe emergent lysosomal heterogeneity, with subsets of differential acidified lysosomes accumulating in the aging brain. We further establish midlife as a critical inflection point for autophagy regulation, which may be important for region-specific vulnerability and resilience to aging. By mapping in vivo autophagy dynamics at the single cell level within projection neurons, interneurons and microglia, to astrocytes and secretory cells, we provide a new framework for understanding brain aging and offer potential targets and timepoints for further study and intervention in neurodegenerative diseases.