MMP9 and atherosclerosis: lncRNA growth arrest-specific 5 (GAS5) regulates atherosclerosis developments via various mechanisms including promoting monocyte migration, interaction with the histone methyltransferase EZH2 (enhancer of zeste homolog 2) PRC-2 subunit, decreasing ABCA-1 expression, cholesterol efflux, and producing of inflammatory cytokines via targeting miR-221 and up-regulating MMP-2 and MMP-9 (86, 87).