Macrophages infiltrating injured tissue play an important part in fibrogenesis. To shed light on the functional roles of macrophages, we investigated the appearance of macrophage populations in thioacetamide (TAA)-induced rat hepatic lesions, with or without pretreatment with GdCl(3), a chemical capable of inhibiting Kupffer cell functions. In the GdCl(3)+TAA group rats received a single intraperitoneal injection of GdCl(3) (7.5mg/kg body weight) and, after 24h, a single intravenous injection of TAA (300mg/kg body weight). Rats in the TAA group received TAA only. Rats in both groups were examined on post-TAA injection (PTI) days 3, 5, and 7. In the TAA group, on PTI day 3, when TAA-induced hepatocyte injury was particularly prominent, the number of macrophages peaked, subsequently decreasing until PTI day 7. As compared with the TAA group, the GdCl(3)+TAA group showed significantly decreased numbers of ED1-immunolabelled cells (exudate macrophages) and ED2-immunolabelled cells (Kupffer cells) on PTI days 3, 5, and 7, and OX6-immunolabelled cells (antigen-presenting macrophages) on PTI days 3 and 5. Although less strikingly, the numbers of alpha-smooth muscle actin-positive myofibroblasts and fibrotic areas were decreased in the GdCl(3)+TAA group. By RT-PCR, the expression of TGF-beta1 mRNA was suppressed on PTI days 3 and 7 in the GdCl(3)+TAA group, and the suppressed expression was confirmed in vitro by treating rat macrophage-like cells (HS-P) with 1% GdCl(3). The study showed that GdCl(3) treatment decreased the numbers of macrophages appearing in hepatic lesions and inhibited TGF-beta1 mRNA expression in macrophages. Decreased numbers of macrophages may contribute to improvement of hepatic fibrosis.

Alanine Transaminase↗

PubMedDate not supplied

Distribution of cells labelled by a monoclonal antibody (A3) against a cloned cell line derived from a rat malignant fibrous histiocytoma.

To pursue the histogenesis of malignant fibrous histiocytoma (MFH), of which the cell of origin is still debated, a monoclonal antibody (A3) was produced against a rat MFH-derived cloned cell line (MT-8). Antigen recognized by A3 was around 80 kDa in molecular weight and was seen on the cytoplasmic membrane of MT-8 cells by immunoelectron microscopy. A3 reacted specifically with MT-8 cells, with another rat MFH-derived cell line (MT-9) and with their induced tumours in syngeneic rats, but not with other rat tumours such as fibrosarcoma, histiocytic sarcoma, malignant meningioma, uterine leiomyosarcoma, endometrial stromal sarcoma, mononuclear cell leukaemia and malignant schwannoma. These findings indicate that A3 has a high specificity for rat MFH cells. In fetuses on gestation days 15, 18 and 20 and in postnatal rats aged 1, 4 and 8 days, A3 reacted with primitive mesenchymal cells in visceral organs and around arteries and bronchi, as well as in the lamina propria of intestinal mucosa, renal interstitium, meninges and perineurium. There were no A3-positive connective tissue cells in organs or other sites in adult rats more than 10 weeks old. It is therefore likely that MFH cells share antigens with primitive mesenchymal cells, which may be multipotent for mesenchymal differentiation. The present study suggests that MFH consists of a population of primitive, undifferentiated mesenchymal cells. A3 also immunolabelled endothelial cells of arteries, venules and pulmonary capillaries in fetal, postnatal and adult rats; vascular endothelial cells in chemically induced hepatic and renal lesions also reacted strongly with A3. However, the significance of endothelial immunoreactivity with A3 remains to be elucidated.

Animals↗

PubMedDate not supplied

Macrophage-like cell line (HS-P) from a rat histiocytic sarcoma.

With future exploration of macrophage properties in mind, we established a novel cell line (HS-P) from a transplantable histiocytic sarcoma, derived originally from a tumour in an aged F344 rat. HS-P was subjected to 70 serial passages, in which the mean doubling time was 15.7 h. The cells, which were round, oval or polygonal in shape, were arranged in a compact sheet. They reacted to varying degrees for lysosomal enzymes (acid phosphatase and non-specific esterase) and with the following antibodies: ED1/ED2 (rat macrophage/histiocyte-specific), OX6 (rat MHC class II-specific), lysozyme antibody and alpha1-antichymotrypsin antibody. Electron microscopically, HS-P cells showed lysosomes and prominent cell projections. These findings indicated that the cultured cells were macrophage-like. Syngeneic rats inoculated subcutaneously or intraperitoneally with HS-P cells invariably developed sarcomatous tumours consisting of monomorphic mononuclear cells, which exhibited cytochemical properties similar to those of cultured HS-P cells. Bioassay and reverse transcription-polymerase chain reaction methods revealed that tumour necrosis factor-alpha increased on addition of lipopolysaccharide (LPS), indicating that HS-P cells remained LPS-responsive. HS-P cells may prove to be a useful tool for in-vitro studies of macrophage function.

Acid Phosphatase↗