miR-21 was found significantly elevated in the serum of ischemic stroke patients [93, 94], and upregulation of miR-21 expression by mimics significantly reduced ischemic stroke-induced infarct volume, edema, BBB disruption by decreasing the levels of p38, mitogen-activated protein kinase kinase 3 (MAP2k3), inducible nitric oxide synthase (iNOS), and MMP-9 [73]. Here, MMP9 is linked to ischemic stroke.