Project description:Recent studies suggest that transient premature senescence is essential for tissue remodeling. Myocardial infarction (MI) induces extensive myocardial remodeling through fibroblast-driven extracellular matrix (ECM) production. However, the characteristics and functions of the senescent cells (Sen.) following MI-induced cardiac remodeling remains elusive. In the present study, we observed a gradual increment number of Sen. within the ischemic region over time following MI, peaking at day 7 post-MI, with a subsequent decline in both wild-type mice and p16Ink4a-CreERT2-mT/mG reporter mice within 4 weeks. Using lineage tracing in the p16 reporter mice, we found most of the transient Sen. transitioned to non-senescent state. Then we analyzed our single-nucleus (sn)-multiome and fluorescence-based (SPiDER-β-gal/p16-EGFP) spatial transcriptomics data from the infarcted heart on day 7 post-MI to identify the cellular composition of transient Sen. We also conducted the deconvolution of the Sen. in the integrated dataset using different computational techniques. Additionally, we generated a reference (query dataset) based on SPiDER-βGal/p16-EGFP positivity and mapped it back to the snMultiome dataset. Through all approaches, we found fibroblasts and the subpopulation late myofibroblasts (MF) constituted a major proportion of Sen. In the snMultiome dataset, we explored the features of senescent late MF through differentially expressed genes/peaks and transcriptional binding motif analysis, and found the senescent late MF exhibited enhanced contractile properties and reduced ECM production capability compared with non-senescent late MF. These findings were supported by in vitro experiments showing that ischemia-induced senescent MF exhibited reduced soluble collagen production compared to TGF-β1-induced non-senescent MF. Additionally, in vivo studies revealed worsened cardiac function post-MI following senolytics administration compared to the vehicle group.

Project description:BACKGROUND: Ischemic heart disease remains a leading cause of mortality worldwide, with adverse remodeling post-myocardial infarction (MI) driven by inflammation and cardiomyocyte loss. While cytotoxic lymphocytes exacerbate injury, and p16 marks cellular senescence in diseased hearts, the cell-type-specific roles of P16+ populations remain undefined. METHODS: Using p16-CreER;R26-tdT reporter mice, we mapped P16+ cellular heterogeneity post-MI. Senolytic effects were assessed via combination of dasatinib and quercetin (DQ) administration. Transcriptomic profiling (bulk/scRNA-seq) of sorted P16+ cells identified secreted factors, validated by in silico predictions and qPCR. Intercellular communication was analyzed using CellChat. Functional roles were tested via CCL8 neutralization, genetic Ccl8 ablation in P16+ cells, lymphocyte depletion, and intersectional genetic ablation of P16+ fibroblasts/macrophages using dual-recombinase systems (p16-DreER;Pdgfra-CreER;R26-lr-tdT-DTR and p16-DreER;Cx3cr1-CreER;R26-lr-tdT-DTR). RESULTS: P16 was induced in fibroblasts, macrophages, coronary endothelial cells, and cardiomyocytes post-MI. DQ treatment selectively eliminated P16+ macrophages and fibroblasts, improving cardiac function. Transcriptomics revealed P16+ macrophages and fibroblasts as primary CCL8 sources. CCL8 blockade reduced infiltration of cytotoxic lymphocytes (CD8+ T cells and NK cells), decreased cardiomyocyte apoptosis, and improved repair. Genetic Ccl8 ablation in P16+ cells replicated these benefits. Crucially, intersectional genetic ablation of P16+ fibroblasts, but not macrophages, reduced fibrosis and enhanced function, whereas CD8+ T cell (not NK cell) depletion attenuated remodeling. CONCLUSIONS: P16+ cells orchestrate adverse post-MI remodeling via CCL8-dependent recruitment of cytotoxic lymphocytes, expecially CD8+ T cells, driving cardiomyocyte apoptosis. Precision targeting of P16+ fibroblasts or CCL8 blockade represents a promising therapeutic strategy for ischemic heart disease.

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Transient Senescence Following Myocardial Infarction: Characterization and Functional Implications in Cardiac Remodeling [SpatialTranscriptome]

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