Fig. 6. B2M is secreted by stressed cardiomyocytes to activate fibroblasts.

a Western blot on mice plasma at different time points post IR or 1 day post sham (n = 3 animals). Equal loading of plasma proteins was confirmed by Coomassie staining (Supplementary Fig. 9). b Quantification of immunoblots in (a); *P < 0.05 compared to sham, Kruskal–Wallis test with Dunnett’s multiple comparison post-hoc test. c Cognate receptor expression of selected ligands in NIH/3T3 fibroblasts is shown by RT-qPCR. d Upregulation of two myofibroblast (Acta2 and Vim) markers in NIH/3T3 cells after treatment with B2M, TGF-β served as positive control (n = 9 from 3 independent experiments). e Increased wound healing of NIH/3T3 cells after treatment with B2M, assessed by scratch assay. Images show representative pictures for each condition. Dashed lines indicate gap size. f Quantification of wound healing assay relative to corresponding control (n = 6 from 2 independent experiments). Scale bars, 200 μm. g Immunohistochemistry images of heart slices after IR or sham surgery. White arrows indicate cardiomyocytes (larger cells with diminished CTNT staining) within the infarct zone that show B2M expression. CTNT cardiac troponin T. Scale bars, 100 μm (left and middle panels) and 20 μm (right panels). Data are presented as mean ± SEM. *P < 0.05, ***P < 0.001. One-way ANOVA with multiple comparison vs control and Dunnett’s adjustment for multiple hypothesis testing.