Rhenium‐Based β‐Galactosidase Probe Allows Senescence Profiling by Mass Cytometry

ABSTRACT Mass cytometry is an attractive analytical technique for the study of cellular senescence due to its ability to simultaneously interrogate the multiple biomarkers necessary to define senescent phenotypes. However, measuring senescence‐associated β‐Galactosidase (SA‐β‐Gal) activity, the gold standard biomarker for detection of senescent cells, requires a functional mass cytometry detectable probe compatible with an antibody‐based panel. Herein, we report a small‐molecule mass cytometry probe for SA‐β‐Gal, ReGal, that uses a piano‐stool rhenium complex as a mass tag. We demonstrate that the probe measures β‐Gal activity in vitro and in cellulo with minimal background signal. We further show that the probe improves the discrimination of senescence‐induced mouse embryonic fibroblasts (MEFs) against untreated cells compared to using only antibody‐based mass cytometry reagents. Finally, we demonstrate that the probe reveals a putatively senescent sub‐population of mouse peripheral blood mononuclear cells (PBMCs), which is enriched in old vs. young mice, that could not be segmented by antibody‐based reagents alone.