To further investigate why the protective effect of HMGB1 ineffective in TLR9-deficient mice, We found that the expression levels of α-SMA and collagen I in immunofluorescence staining of rhHMGB1-treated TLR9KO mice heart did not increase as in rhHMGB1-treated WT mice at day 7 after MI, conversely, as low as PBS-treated KO mice (Fig. 7a). Here, TLR9 is linked to myocardial infarction.