MMP9 and chronic obstructive pulmonary disease: An antagomir of miR-34a, which blocks its action, restores SIRT1/6 in senescent small airway epithelial cells from patients with COPD, reduces markers of cellular senescence (p16, p21, p53), reduces SASP mediators (TNF-α, IL-1β, IL-6, CCL2, CXCL8, MMP9), and increases proliferation of senescent epithelial cells by reversing cell cycle arrest (Baker et al, 2016b).