CEACAM1 and Myocardial fibrosis: We detected myocardial fibrosis using Masson trichrome staining method, and found that the fibrotic infarct length and fibrosis area in the non-infarct zone were significantly smaller in the CEACAM1 KO-MI group than in the WT-MI group (P < 0.05, Fig. 3B,C), suggesting less ventricular expansion in KO mice.