Patrick Henriet

Different collagenase gene products have different roles in degradation of type I collagen

Vertebrate collagenases, matrix metalloproteinases (MMPs), cleave type I collagen at a single helical locus. We show here that rodent interstitial collagenases (MMP-13), but not human fibroblast collagenase (MMP-1), cleave type I collagen at an additional aminotelopeptide locus. Collagenase cDNAs and chimeric constructs in pET-3d, juxtaposing MMP-13 sequences amino-terminal to the active site in the catalytic domain and MMP-1 sequences carboxyl-terminal and vice versa, were expressed in Escherichia coli. Assays utilized collagen from wild type (+/+) mice or mice that carry a targeted mutation (r/r) that encodes substitutions in α1(I) chains that prevent collagenase cleavage at the helical locus. MMP-13 and chimeric molecules that contained the MMP-13 sequences amino-terminal to the active site cleaved (+/+) collagen at the helical locus and cleaved cross-linked (r/r) collagen in the aminotelopeptide (β components converted to α chains). Human MMP-1 and chimeric MMP-1/MMP-13 with MMP-1 sequences amino-terminal to the active site cleaved collagen at the helical locus but not in the aminotelopeptide. All activities were inhibited by TIMP-1, 1,10-phenanthroline, and EDTA. Sequences in the distal two-thirds of the catalytic domain determine the aminotelopeptide-degrading capacity of MMP-13.

Aging enhances liver fibrotic response in mice through hampering extracellular matrix remodeling

Clinical data identify age as a factor for severe liver fibrosis. We evaluate whether and how aging modulates the fibrotic response in a mouse model. Liver fibrosis was induced by CCl4 injections (thrice weekly for 2 weeks) in 7 weeks- and 15 months-old mice (young and old, respectively). Livers were analyzed for fibrosis, inflammation and remodeling 48 and 96 hours after the last injection. Old mice developed more severe fibrosis compared to young ones as evaluated by sirius red morphometry. Expression of pro-fibrogenic genes was equally induced in the two age-groups but enhanced fibrolysis in young mice was demonstrated by a significantly higher Mmp13 induction and collagenase activity. While fibrosis resolution occurred in young mice within 96 hours, no significant fibrosis attenuation was observed in old mice. Although recruitment of monocytes-derived macrophages was similar in young and old livers, young macrophages had globally a remodeling phenotype while old ones, a pro-fibrogenic phenotype. Moreover, we observed a higher proportion of thick fibers and enhanced expression of enzymes involved in collagen maturation in old mice. Conclusion Impaired fibrolysis of a matrix less prone to remodeling associated with a pro-inflammatory phenotype of infiltrated macrophages contribute to a more severe fibrosis in old mice.

Chronic liver injury promotes hepatocarcinoma cell seeding and growth, associated with infiltration by macrophages.

Ninety percent of hepatocarcinoma (HCC) develops in a chronically damaged liver. Interactions between non‐tumor stromal components, especially macrophages, and cancer cells are still incompletely understood. Our aim was to determine whether a chronically injured liver represents a favorable environment for the seeding and growth of HCC cells, and to evaluate the potential roles of macrophages infiltrated within the tumor. HCC cells were injected into the liver in healthy mice (healthy liver group [HL]) and in mice chronically treated with carbon tetrachloride (CCl4) for 7 weeks (CCl4 7w group). Livers were examined for the presence of tumor 2 weeks post‐injection. Tumor and non‐tumor tissues were analyzed for macrophage infiltration, origin (monocytes‐derived vs resident macrophages) and polarization state, and MMP production. Fifty‐three percent of mice developed neoplastic lesion in the HL group whereas a tumor lesion was found in all livers in the CCl4 7w group. Macrophages infiltrated more deeply the tumors of the CCl4 7w group. Evaluation of factors involved in the recruitment of macrophages and of markers of their polarization state was in favor of prominent infiltration of M2 pro‐tumor monocyte‐derived macrophages inside the tumors developing in a chronically injured liver. MMP‐2 and ‐9 production, attributed to M2 pro‐tumor macrophages, was significantly higher in the tumors of the CCl4 7w group. In our model, chronic liver damage promotes cancer development. Our results suggest that an injured background favors the infiltration of M2 pro‐tumor monocyte‐derived macrophages. These secrete MMP‐2 and MMP‐9 that promote tumor progression.