MMP13 and Hepatic fibrosis: Compared with DDR2+/+ livers, chronic CCl4 treatment increases DDR2-/- liver fibrosis and ECM remodeling. The expression of DDR2 in HSCs is enhanced after CCl4 treatment. Collagen type I, MMP-2, and MMP-13 mRNA expression are reduced significantly in HSCs from chronic CCl4-injured DDR2-/- livers. The migration and proliferation of HSCs from chronically injured DDR2-/- livers were enhanced, and the matrix degradation was reduced. Macrophages from fibrotic DDR2-/- livers show stronger chemoattractive activity toward DDR2-/- HSCs