S100A9 and myocardial infarction: The role of S100A9 in the repair period of MI was further confirmed by another experiment in which a reduction in infiltrating monocytes and macrophages in the myocardium with an approximately 50% decrease in the number of reparatory Ly6CloMerTKhi macrophages was detected in S100A9 gene-deficient mice (Marinkovic et al., 2020).