Sequential behaviour of extracellular matrix glycoproteins in an experimental model of hepatic fibrosis.

The behaviour of extracellular matrix glycoproteins (fibronectin, laminin, basement membrane heparan-sulphate proteoglycan, type III, IV and V collagens) has been investigated in a sequential model of experimental hepatic fibrosis, using an immunofluorescence technique. The presence of some basement membrane macromolecules (such as type IV and V collagens, laminin and basement membrane heparan-sulphate proteoglycan) is detectable only in the early stages of septa formation, while type III collagen and fibronectin persist in late septa. These data suggest that hepatic fibroplasia proceeds through different steps in which stromal glycoproteins are preferentially engaged, as happens during organogenesis.

Steroid treatment lowers hepatic fibroplasia, as explored by serum aminoterminal procollagen III peptide, in chronic liver disease.

Serum aminoterminal type III procollagen peptide (sPIIIP) has been proposed as an index of hepatic fibroplasia. sPIIIP was retrospectively evaluated in 34 treated and five untreated patients affected by chronic active hepatitis with or without cirrhosis by an RIA test. Serum samples taken before and after 6 months of treatment were tested in all cases. In 15 of the treated and all untreated patients, 6-20 (median 13) sera, corresponding to a median follow-up of 43 months were studied. Before treatment, the sPIIIP median value was 18.6 ng/ml; after 6 months of treatment, it decreased to 13.6 ng/ml (p less than 0.005). Follow-up sPIIIP levels were significantly lower in treated than in untreated patients (p less than 0.05), at each interval considered, except for the last control (39 months). In seven patients, treatment was discontinued: sPIIIP rose rapidly in six; four of them were retreated and this was followed by a new decrease. In four patients, sPIIIP was tested weekly from the onset of the treatment: it reverted to normal values within the first week in all cases, while GOT decreased later. sPIIIP is significantly and rapidly reduced by steroids. Steroid withdrawal is generally followed by a rebound, with a new decrease when treatment is restarted. Since sPIIIP is more rapidly lowered than GOT levels, the above data support the hypothesis that steroids can directly affect collagen metabolism.

Basement membrane production by hepatocytes in chronic liver disease.

The immunohistologic distribution of fibronectin, laminin, type IV collagen and whole basement membrane was evaluated in liver biopsies from patients with chronic active liver disease. Fibronectin was consistently increased in the areas of piecemeal necrosis, portal tracts and fibrous septa. Laminin was not detected in normal liver parenchyma. In contrast, laminin positive linear basement membrane structures were prevalent in portal tracts, fibrous septa and the peripheral sinusoids of cirrhotic nodules. In areas of piecemeal necrosis, the hepatocytes, single or assembled in "rosettes", were frequently underlined by linear deposits of laminin and type IV collagen. This immunoreactivity was often polarized, being confined to the stromal side of liver cells, while the parenchymal side was negative for both proteins. Electron microscopy revealed a typical basement membrane in corresponding areas. Hepatocytes normally do not produce a basement membrane, but do so following chronic injury. We suggest that the polarized basement membrane accumulation by hepatocytes is a hallmark of hepatocyte regeneration following damage.

Correlation between Ito cells and fibrogenesis in an experimental model of hepatic fibrosis. A sequential stereological study.

The relationship between Ito cells and hepatic fibrogenesis has been investigated in an experimental model: intraperitoneal injection of heterologous serum in rats leads to the appearance of fibrous septa within 5 weeks. Groups of rats were sacrificed at various intervals (from 2.5 to 20 weeks), saline-injected rats being used as controls. Liver fragments were prepared for light and electron microscopy and determination of hydroxyproline. Ito cells were identified by defined morphological criteria on 1 micron sections. The volume density (VD) of Ito cells and fibrous septa, and the Ito cell index were determined. Ito cells represent a very relevant component of early septa. In later stages, the VD of cells with morphological features of Ito cells falls to very low values. This might be related to modulation of Ito cells to fibroblasts. The increase of tissue hydroxyproline is delayed with respect to the peak VD of septal Ito cells, actually corresponding to the fall in the VD of septal Ito cells. The striking increase in the VD of total Ito cells cannot be related to a theoretically possible increase in the volume of single Ito cells, as VD always parallels the Ito cell index. These data suggest a hyperplastic reaction, possibly associated with a cellular migration from the lobules to early septa.