MMP9 and myocardial infarction: Qiao Xiaoying explored the role of renal cortex matrix metalloproteinase-9 in the clinical treatment of myocardial infarction and believed that renal cortex matrix metalloproteinase-9 is an important factor to promote the recovery of myocardial injury after acute myocardial infarction (Qiao et al., 2022).