MAP2K4 and myocardial infarction: In the I/R injury model established in rats, the abundant miRNA-455-3p in HBMSCs-exo inhibits the expression of the Mitogen/Extracellular regulatory protein kinase 1(MEKK1)-Mitogen activated protein kinase kinase 4 (MKK4)-JNK signaling pathway, reduces cell apoptosis, and increases myocardial cell vitality, which has a protective effect on myocardial injury by I/R and also provides a new idea for the treatment of myocardial infarction [131].