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Figure title: "Mitochondrial membrane potential collapse and dispersion with age"

Subtitle: Per-cell TMRM fluorescence in fibroblasts across four age groups and two tissues

#MitochondrialBioenergetics #TMRM #MembranePotential #SingleCellFunction #mtDNAheteroplasmy #Mitophagy
Figure title: "Mitochondrial membrane potential collapse and dispersion with age" Subtitle: Per-cell TMRM fluorescence in fibroblasts across four age groups and two tissues I am sharing a figure exploring how mitochondrial membrane potential (ΔΨm) distributions shift with donor age at single-cell resolution. The visualization uses a faceted half-violin raincloud design: each facet pairs the smoothed density (the "cloud") of per-cell TMRM fluorescence with jittered raw observations (the "rain"), facilitating simultaneous inspection of central tendency, distributional shape, and the tails that population-averaged assays obscure. Facets are arranged across four age groups and two tissue sources (dermal and pulmonary fibroblasts). A methodological caveat before interpretation: the data are simulated. They are parameterized to reproduce trends reported in the literature rather than to present novel empirical measurements, and are intended to illustrate the analytical framework and expected effect structure. Two features are salient. First, a progressive downward shift in median TMRM signal with age, consistent with age-associated ΔΨm depolarization attributable to declining electron transport chain flux and proton-motive force. Second, and arguably more informative, a marked increase in interquartile spread and bimodality in the older cohorts. This dispersion reflects mitochondrial heterogeneity — the coexistence of polarized and depolarized subpopulations within isogenic cultures — that likely arises from clonal expansion of mtDNA deletions, stochastic mitophagy insufficiency, and asymmetric organelle partitioning across mitotic divisions. I would emphasize that variance itself is a phenotype here. Reporting only mean ΔΨm collapses precisely the signal of interest. The raincloud geometry makes this explicit and, I would argue, should be standard for single-cell functional readouts.
September 8, 2026 at 6:21 PM