Clin Res Cardiol (2022).

Deep phenotyping of heart-specific T-cells activated in the context of myocardial infarction
M. Delgobo1, E. Weiß1, A.-E. Saliba2, B. Ludewig3, S. Frantz4, U. Hofmann4, G. Ramos1
1Deutsches Zentrum für Herzinsuffizienz, Universitätsklinikum Würzburg, Würzburg; 2Helmholtz-Institut für RNA-basierte Infektionsforschung, Würzburg; 3Kantonsspital St. Gallen, St. Gallen, CH; 4Medizinische Klinik und Poliklinik I, Universitätsklinikum Würzburg, Würzburg;
CD4+ T-cell mediated responses have been shown to directly affect tissue repair in a wide range of animals and tissues, including the post-myocardial healing. In a previous study, we reported that myosin-specific T helper cells (TCR-M) infiltrate the infarcted myocardium, acquire FOXP3 expression, and regulate tissue repair. FOXP3-expressing regulatory T-cells can exhibit a broad phenotypic plasticity, though, and the mechanisms by which they influence myocardial repair have not been fully elucidated. Herein, we performed a deep-phenotyping of the TCR-M cells that engage the post-MI responses and sought to uncover how their interplay with other cardiac cell populations in the healing myocardium.

Myocardial infarction (MI) was induced in BALB/C mice after permanent ligation of the left coronary artery. Heart and lymph nodes were collected for FACS analysis at 5 and 7 days after MI surgery. CD4+ T-cells were sorted from heart and mediastinal lymph nodes of MI and sham operated mice at 5 and 7 days after surgery, stained with hashtag  and cite-seq antibodies and combined as an unique sample for single cell RNA sequencing (scRNAseq) analysis.

Flow cytometry analyses confirmed that adoptively transferred TCR-M cells accumulated in the infarcted heart and acquired FOXP3 expression, produced high levels of TGF-β, and blocked interleukin-17 production by endogenous CD4+ T-cells 7d after MI. ScRNAseq) analysis of TCR-M and endogenous CD4+ T-cells revealed that the myosin-specific T helper cells exhibited an “induced Treg” transcriptomic signature and showed no signs of pro-inflammatory signature. Moreover, the TCR-M cells present in the infarcted hearts showed a phenotype skeweing towards “effector” or “suppressor” cell states. Effector TCR-M cells were characterized by upregulated expression of transcripts related to T-cell receptor activation, expressed the cytokines Tgfb1 and Mif, and were enriched in infarcted myocardium at day 5. Suppressor TCR-M cells were marked by the expression of co-inhibitory receptors (Pdcd1, Tigit), expressed pro-angiogenic and myeloid supporting transcripts (e.g. Angptl2, Csf1) and peaked at day 7. Nichenet analysis indicated that TCR-M cells supported myocardium macrophage survival and favored pro-fibrotic healing responses (e.g. Col3a1, Col5a1).

Our study uncovers distinct phenotypic states of regulatory TCR-M cells implicated in post-MI repair.