MMP2 and alcohol dependence: Acetaldehyde increases the protein level of DDR2 and MMP2 in vitro and in vivo. The silencing of DDR2 reduces MMP2 level, HSC proliferation, the synthesis of collagen I and TIMP-1 mRNA, and enhances necrosis rate and apoptosis of HSC, while also alleviating liver injury and collagen deposition in the alcohol-induced model