Serum collagenase activity in chronic liver diseases

Elastomeric and pH-responsive hydrogels based on direct crosslinking of the poly(glycerol sebacate) pre-polymer and gelatin

The synthesis and biomedical applications of novel elastomeric, pH-responsive, biocompatible and biodegradable copolymer hydrogels based on poly(glycerol sebacate) and gelatin.

Hepatocytes express nerve growth factor during liver injury: evidence for paracrine regulation of hepatic stellate cell apoptosis

A key feature of recovery from liver fibrosis is hepatic stellate cell (HSC) apoptosis, which serves the dual function of removing the major source of neomatrix and tissue inhibitors of metalloproteinases thereby facilitating matrix degradation. The mechanisms regulating HSC apoptosis remain undefined but may include the interaction of nerve growth factor (NGF) with its receptor, p75, on HSC. In this study, by TaqMan polymerase chain reaction in situ hybridization and immunohistochemistry, we demonstrate that NGF is expressed by hepatocytes during fibrotic injury. Peak hepatocyte expression of NGF (48 hours after CCl(4) injection) coincides with maximal rate of apoptosis of HSC by terminal dUTP nick-end labeling staining. Addition of recombinant NGF to HSC in tissue culture causes a dose-dependent increase in apoptosis. NGF regulates nuclear factor (NF)-kappaB activity, reducing p50/p65 binding detected by electromobility shift assay and reduced NF-kappaB CAT reporter activities from both basal unstimulated levels and after NF-kappaB induction by tumor necrosis factor. In each case, a relative reduction in NF-kappaB binding was associated with a significant increase in caspase 3 activity. These data provide evidence that NGF is expressed during fibrotic liver injury and may regulate number of activated HSCs via induction of apoptosis.

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Expression of exogenous rat collagenase in vitro and in a rat model of liver fibrosis

AIM: The present study was conducted to test the hypothesis that the introduction of the collagenase gene into tissue culture cells and into a rat model of liver fibrosis would result in the expression of enzymatically active product.

METHODS: FLAG-tagged full-length rat collagenase cDNA was PCR amplified and cloned into a mammalian expression vector. NIH3T3 cells were then transiently transfected with this construct. Expression of exogenous collagenase mRNA was assessed by RT-PCR, and the exogenous collagenase detected by Western blotting using anti-FLAG monoclonal antibody. Enzymatic activity was detected by gelatin zymography. To determine the effects of exogenous collagenase production in vivo, the construct was bound to glycosyl-poly-L-lysine and then transduced into rats that had developed liver fibrosis as a result of CCl₄ plus ethanol treatment. The hepatic expression of the construct and its effect on the formation of liver fibrosis were demonstrated using RT-PCR and immunohistochemistry.

RESULTS: It was found that exogenously expressed rat collagenase mRNA could be detected in NIH3T3 cells following transfection. Enzymatically active collagenase could also be detected in the culture medium. The recombinant plasmid was also expressed in rat liver after in vivo gene transfer. Expression of exogenous rat collagenase correlated with decreased deposition of collagen types I and III in the livers of rats with experimentally induced liver fibrosis.

CONCLUSION: The expression of active exogenous rat collagenase could be achieved in vitro and in vivo. It was suggested that in vivo expression of active exogenous collagenase may have therapeutic effects on the formation of liver fibrosis.

Serum matrix metalloproteinase-1 in patients with chronic viral hepatitis

BACKGROUND AND AIMS

Previously we found that serum matrix metalloproteinase (MMP)-1 activity decreased with progression of chronic liver disease. Our objectives in the present study were to observe the change in the serum MMP-1 protein concentration using recently developed specific enzyme immunoassays for MMP-1 and MMP-1 complexed with tissue inhibitor of metalloproteinases (TIMP)-1 and to elucidate the clinical usefulness of the serum MMP-1 test in chronic viral hepatitis. We measured the serum concentrations of MMP-1 and MMP-1/TIMP-1 complex using these immunoassays in 64 patients with histologically characterized chronic viral hepatitis.

RESULTS

Serum MMP-1 concentration was inversely related to the histological severity of chronic hepatitis (P< 0.0001). It was closely associated with the histological degree of periportal necrosis (P< 0.0001), intralobular necrosis (P< 0.005), portal inflammation (P<0.0001) and liver fibrosis (P< 0.05). The serum concentration of MMP-1/TIMP-1 complex was also related to the histological severity of chronic hepatitis (P< 0.0001). It was associated with the degree of portal inflammation (P< 0.05), but not with the degree of periportal necrosis, intralobular necrosis or liver fibrosis. As serum MMP-1 level was closely associated with the histological degree of necroinflammation, we examined the ability of the serum MMP-1 test to differentiate active and inactive forms of hepatitis with a receiver operating curve. The results were compared with those of serum procollagen type III N-peptide (PIIINP) test. We found that the serum MMP-1 test was superior to the serum PIIINP test in assessing liver necroinflammation.

CONCLUSIONS

In addition to the previously reported changes in enzyme activity, MMP-1 proteins in serum decreased during histological progression of chronic hepatitis. The serum MMP-1 test may be useful clinically to differentiate active and inactive types of hepatitis in patients with chronic viral hepatitis.

Mechanisms of spontaneous resolution of rat liver fibrosis. Hepatic stellate cell apoptosis and reduced hepatic expression of metalloproteinase inhibitors

Liver fibrosis results from the excessive secretion of matrix proteins by hepatic stellate cells (HSC), which proliferate during fibrotic liver injury. We have studied a model of spontaneous recovery from liver fibrosis to determine the biological mechanisms mediating resolution. Livers were harvested from rats at 0, 3, 7, and 28 d of spontaneous recovery from liver fibrosis induced by 4 wk of twice weekly intraperitoneal injections with CCl4. Hydroxyproline analysis and histology of liver sections indicated that the advanced septal fibrosis observed at time 0 (peak fibrosis) was remodeled over 28 d of recovery to levels close to control (untreated liver). alpha-Smooth muscle actin staining of liver sections demonstrated a 12-fold reduction in the number of activated HSC over the same time period with evidence of HSC apoptosis. Ribonuclease protection analysis of liver RNA extracted at each recovery time point demonstrated a rapid decrease in expression of the collagenase inhibitors TIMP-1 and TIMP-2, whereas collagenase mRNA expression remained at levels comparable to peak fibrosis. Collagenase activity in liver homogenates increased through recovery. We suggest that apoptosis of activated HSC may vitally contribute to resolution of fibrosis by acting as a mechanism for removing the cell population responsible for both producing fibrotic neomatrix and protecting this matrix from degradation via their production of TIMPs.

Time dependent alterations of serum matrix metalloproteinase-1 and metalloproteinase-1 tissue inhibitor after successful reperfusion of acute myocardial infarction

OBJECTIVE

To test the hypothesis that changes in serum matrix metalloproteinase-1 (MMP-1) and tissue inhibitors of metalloproteinase-1 (TIMP-1) after acute myocardial infarction reflect extracellular matrix remodelling and the infarct healing process.

PATIENTS

13 consecutive patients with their first acute myocardial infarction who underwent successful reperfusion.

METHODS

Blood was sampled on the day of admission, and on days 2, 3, 4, 5, 7, 14, and 28. Serum MMP-1 and TIMP-1 were measured by one step sandwich enzyme immunoassay. Left ventricular volume indices were determined by left ventriculography performed four weeks after the infarct.

RESULTS

Serum concentrations of both MMP-1 and TIMP-1 changed over time. The average serum MMP-1 was more than 1 SD below the mean control values during the initial four days, increased thereafter, reaching a peak concentration around day 14, and then returned to the middle control range. Negative correlations with left ventricular end systolic volume index and positive correlations with left ventricular ejection fraction were obtained for serum MMP-1 on day 5, when it began to rise, and for the magnitude of rise in MMP-1 on day 5 compared to admission. Serum TIMP-1 at admission was more than 1 SD below the mean control value, and increased gradually thereafter, reaching a peak on around day 14. Negative correlations with left ventricular end systolic volume index and positive correlations with left ventricular ejection fraction were obtained for serum TIMP-1 on days 5 and 7, and for the magnitude of rise in TIMP-1 on days 5 and 7 compared to admission.

CONCLUSIONS

Both MMP-1 and TIMP-1 showed significant time dependent alteration after acute myocardial infarction. Thus MMP-1 and TIMP-1 may provide useful information in evaluating the healing process as it affects left ventricular remodelling after acute myocardial infarction.

TIMP expression in toxic and cholestatic liver injury in rat

BACKGROUND/AIMS

Hepatic fibrosis is a dynamic pathological process with a net accumulation of extracellular matrix proteins. Recent evidence suggests that besides their increased synthesis, inhibition of matrix degradation plays a significant role. ECM degradation occurs via metalloproteinases which are inhibited in situ by specific tissue inhibitors of metalloproteinases (TIMPs). The aim of our studies was to determine the expression of TIMPs during toxic liver injury and cholestatic liver injury leading to fibrosis.

METHODS

We examined the expression of TIMP-1, -2 and -3 in two different rat models for liver injury (intraperitoneal CCl4 injection and bile duct ligation) by Northern blot analysis and in situ hybridization. For comparison, the mRNA expression of the acute phase protein haptoglobin was measured.

RESULTS

TIMP-1 was increased during the early phase of toxic liver injury and in cholestasis. Its expression occurred predominantly in areas of inflammation, in hepatocytes, and in mesenchymal and endothelial cells. There was a slight upregulation of TIMP-2 expression during cholestasis. TIMP-3 was not detected at all.

CONCLUSIONS

Our results emphasize an involvement of TIMP-1 in matrix homeostasis, indicating its possible participation in liver fibrosis.

Tissue inhibitors of metalloproteinases in liver fibrosis

Liver fibrosis and its end stage sequelae cirrhosis represent a major worldwide health problem. By definition progressive fibrosis occurs when the rate of matrix synthesis exceeds matrix degradation. Considerable evidence suggests that the hepatic stellate cell is central to the fibrotic process. During liver injury these cells transform from a quiescent retinoid filled phenotype to a proliferative myofibroblast like cell. In this 'activated' phenotype the HSC is the major source of the interstitial collagens, which characterize fibrosis. Recent work suggests that the HSCs are also a source of matrix degrading metalloproteinase (MMPs), indicating that, together with other cells, hepatic stellate cells (HSC) could participate in matrix remodelling. However, HSC activation in tissue culture models and in vivo is also associated with expression of the powerful MMP inhibitors: tissue inhibitors of metalloproteinases 1 and 2 (TIMP-1 and TIMP-2). TIMP expression has also been demonstrated in fibrotic human liver disease and animal models of liver fibrosis. TIMPs 1 and 2 may therefore promote progression of hepatic fibrosis through inhibition of matrix degradation.