Mast cells are known to be present in human liver but their distribution and density in normal livers and in chronic liver diseases have not previously been examined. In this study, we quantified mast cell numbers and examined their distribution in percutaneous biopsy specimens from normal livers (n = 8) and in two chronic progressive liver diseases: primary biliary cirrhosis (PBC) (n = 40) and alcoholic liver disease (n = 33). We compared differences in mast cell density between these two forms of chronic liver disease because it had been suggested that mast cells may play a role in the development of liver fibrosis, particularly in patients with chronic cholestatic liver disease who frequently have increased plasma histamine levels. Mast cells were identified by immunohistochemistry using a specific monoclonal antibody (AA1) raised against mast cell tryptase after an initial study showed this to be more sensitive for the detection of mast cells than the conventional histochemical stain, toluidine blue. Our results showed that small numbers of mast cells (3.9 ± 3.3/mm2) are present within the portal tracts and sinusoids of normal livers. In progressive chronic liver disease, increased numbers of mast cells were present, which correlated with the increasing amounts of liver fibrosis present. We found significantly more mast cells in the PBC group compared with the alcoholic group for a given amount of fibrosis. Our findings suggest that mast cells and their mediators may play a role in liver fibrogenesis. (HEPATOLOGY 1995; 22:1175–1181.).
Perisinusoidal cells (PSCs) are currently regarded as the major source of extracellular matrix proteins during hepatic fibrogenesis in response to liver injury. However, the cellular mechanisms underlying their response to injury are not fully understood. One hypothesis is that the PSCs are stimulated by peptide growth factors produced by hepatic macrophages (Kupffer cells) in response to parenchymal cell damage. In this study we have investigated the kinetics of the PSC and macrophage populations in acute carbon tetrachloride-induced hepatic injury in rats. PSCs were identified immunohistochemically by detection of cytoplasmic desmin; monocytes and macrophages were detected using the monoclonal antibodies ED1 and ED2; cells in S phase were identified by immunohistochemical detection of nuclear-incorporated bromodeoxyuridine. The results showed an expansion of the desmin-positive PSC population, predominantly within the damaged perivenular zones, which reached a peak on days 3 and 4 following administration of carbon tetrachloride; this was contributed to by local PSC proliferation. The PSC response was preceded by an expansion of the macrophage population resulting from both local macrophage proliferation and influx of blood monocytes. These results are in keeping with the hypothesis that the PSC response to acute liver injury is mediated, at least in part, by hepatic macrophages.
We have studied changes in the pattern of intrinsic hepatic innervation in sequential liver biopsies from 16 patients who underwent orthotopic liver transplantation. Seventy-one needle biopsies were used, including specimens obtained at the time of transplantation (time zero) and up to 4 years post-transplantation; five transplant hepatectomy tissue blocks removed 3-32 months after transplantation were also assessed. Paraffin sections were immunostained with anti-PGP 9.5 and anti-S-100 to identify nerve fibres. All 'time zero' biopsies contained portal nerves and all but two showed staining of parenchymal fibres. After 1 week, no subsequent biopsies contained parenchymal fibres. The disappearance of portal fibres was less rapid and showed greater variability between patients, but they had all disappeared by 6 weeks and there was no positive staining between 6 and 60 weeks. Thereafter, a minority of biopsies showed innervation of a few small portal tracts. Samples from the porta hepatis, hepatectomy specimens, and needle biopsies containing large tracts showed persistence of major nerve trunks at all stages. Abnormally large nerve bundles were seen in some of these areas. The pattern of nerve staining showed no obvious relationship to the intensity of rejection changes. Our results suggest that there is a limited, delayed capacity for regeneration of portal, but not parenchymal, fibres in the transplanted human liver. The physiological significance of this long-term parenchymal denervation in transplanted livers remains to be determined.
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