To address the Temozolomide price mechanisms underlying increased fibrosis and aberrant tissue remodeling in c-Met deleted livers, we examined the levels of MMPs, the primary proteolytic enzymes involved in the breakdown of ECM. A time course of MMP9 activation showed that in control mice, the proteolytic activity of MMP9 was progressively increasing, along with the expansion of oval cells, whereas c-Met-deficient mice displayed a decrease in MMP9 (Fig. 7A,B). This was consistent with the results of in situ zymography combined

with A6 staining, which showed a close proximity of MMP9 activity to oval cell reaction (Fig. 7C; Supporting Fig. 3). Levels of MMP9 were reduced in both models of liver- and epithelial-specific c-Met deletion

(Fig. 7D,E). There was no difference in MMP2 activity, regardless of genotype. These data link the aberrant tissue remodeling in c-Met-deficient livers with a reduction in stem cell niche component MMP9. Finally, we determined the cell source of MMP9 in DDC-treated livers. For this, we carried out gelatin zymography on isolated hepatocytes, nonparenchymal cell (NPC) fraction, and FACS-sorted F4/80-positive macrophages. Quantification of the intensity of active MMP9 band showed that the main source of active MMP9 was NPC cells, and that monocytes/macrophages accounted for approximately 80% of this activity (Fig. 8A,B). Confirming the zymography results, screening assay dual immunofluorescence staining for MMP9 and markers for oval (A6), Kupffer (F4/80), and stellate (alpha smooth muscle actin; αSMA) cells revealed colocalization at the interface with Kupffer and oval cells,

but not with stellate cells (Fig. 8C). These data show that macrophage is the primary cell source of active MMP9 in this model. To provide additional evidence that the absence of c-Met creates a defective stem cell microenvironment, we examined the expression of chemokine stromal-cell–derived factor 1 (SDF1), known as a powerful chemoattractant for bone-marrow–derived monocytes. SDF1 protein levels were considerably decreased in both Met mutant models as well as the number of A6+/SDF1+ oval cells (Supporting Fig. 4). The aim of this study was to define the role of c-Met-signaling pathway in different phases MCE公司 of adult hepatic stem cell activation by utilizing mice harboring c-met floxed alleles and Alb-Cre or Mx1-Cre transgenes. Using conditional mouse genetics and a DDC toxic liver injury model, we demonstrate that the lack of c-Met signals impaired both hepatocyte- and stem-cell–mediated liver regeneration, leading to the death of mice. Genetic loss of c-Met function has profound effects on tissue remodeling and overall composition of the HSC niche microenvironment concomitant with a failure of HSCs to expand and differentiate into hepatocytes.