CXCR4 and myocardial infarction: Several studies suggested that, by gene overexpression strategy, exosomes derived from MSCs modified with protein kinase B (Akt) mRNA or C-X-C chemokine receptor type 4 (CXCR-4) mRNA could regulate the angiogenesis in myocardial infarction and exerted better therapeutic effects compared with exosomes derived from unmodified MSCs [29, 30].