Regenerative processes in the liver of pigs following partial hepatectomy

Summary About 1/8 of the liver 9distal portions of the left lateral and central lobes) were removed in 6 young pigs aged 1.5 months. Regenerating liver was investigated on the 3rd, 14th and 63rd postoperative days. As demonstrated, regeneration of the liver at the early periods was accompanied by the rise of mitotic activity of hepatic cells and hypertrophy of hepatic lobules. Mitoses within the lobule were unevenly distributed—their greatest number was localized in the middle and peripheral zones of the lobule. On the 14th–63rd days of regeneration smaller hepatic lobules were revealed at the wound surface; the possibility of their formation anew was considered. Perhaps, however, the small lobules represented the retained and reconstructed areas of old lobules.(Presented by Active Member of the Akad. Med. Nauk SSSR N. A. Kraevskii) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 56, No. 7, pp. 91–96, July, 1963     

Activation of extrathymic T cells in the liver during liver regeneration following partial hepatectomy.

Partial hepatectomy was performed in C57BL/6 mice to investigate whether extrathymic T cells in the liver are activated during liver regeneration. This study is based on the finding that in mice with malignant tumours, extrathymic T cells in the liver are activated and yet the intrathymic pathway is suppressed (i.e. thymic atrophy). Attention was therefore focused on whether a similar phenomenon is induced during benign cell regeneration. Extrathymic T cells were identified using the two-colour immunofluorescence test for CD3 and interleukin-2 receptor beta-chain (IL-2R beta) [or lymphocyte function-associated antigen-1 (LFA-1)] antigens. They were estimated to be intermediate CD3+ [or T-cell receptor (TcR)] cells with high expressions of IL-2R beta and LFA-1. It was demonstrated that the proportion and number of intermediate CD3+ cells increased in the early phase (days 2-4 after partial hepatectomy), and that the thymus was inversely atrophic at the same time. This raised the possibility that extrathymic T cells may also be responsible for regulation of normal cell regeneration.     

Regeneration of liver parenchyma and sinusoidal cells following partial hepatectomy

Partial hepatectomy (30 percent of the liver weight) was performed in 225 female Wistar rats, ages 6 weeks, 6 and 9 months. The animals were sacrificed in intervals between 4 hours and 21 d after the operation. The automated microscopic image analysis after Simon et al. (1984) and histoautoradiography were utilized for evaluation of liver cell regeneration. Despite measurement of more than 1,000 cells per animal we were not able to confirm enlargement of hepatocytes as the first reaction to partial hepatectomy The number of liver cells per unit area increased whereas sinusoidal size remained rather constant, corresponding to a decrease in average cell size and in the standard deviation of cell area. The importance of binucleated hepatocytes in the process is emphasized. Measurement of the nucleoli and of the mean extinction values of liver cell nuclei as a measure of the DNA content did not provide any essentially new perspectives. The investigation did however emphasize the importance of the extent of the hepatic resection and the age of the experimental animals on the intensity and subsequent course of liver cell regeneration. Proliferation of the sinusoidal cells themselves after partial hepatectomy could not definitively be demonstrated to be age-dependent.     

Heparanase expression during normal liver development and following partial hepatectomy

Heparan sulphate proteoglycans are major components of the liver extracellular matrix. Their cleavage by heparanase (endo-beta-glucuronidase) may thus be involved in liver-specific normal and pathological processes. Heparanase mRNA and protein were expressed during liver development but not in the mature healthy liver. A biphasic gain of heparanase expression, detected by immunostaining, western blotting, and real-time RT-PCR, was clearly noted following partial hepatectomy, peaking at 12 and 96-168 h and subsiding 2 weeks post-surgery. Expression of heparan sulphate gradually increased throughout the regeneration process. Unlike heparanase, baseline levels of matrix metalloproteinase-2 (MMP-2) were detected in the intact liver, increasing up to 4 days following partial hepatectomy and subsiding at day 10. Bands matching MMP-9 were absent prior to hepatectomy, but visible 2 h post-hepatectomy. Thioacetamide-induced liver fibrosis was associated with increased levels of MMP-9 and MMP-2, correlating with the severity of the disease. Elevated heparanase levels were noted in the early stages of fibrosis, with no further increase evident in rats exhibiting higher fibrotic grades. Taken together, these data suggest a role for heparanase during liver development and remodelling.     

Prolyl hydroxylase and collagen biosynthesis in rat liver following varying degrees of partial hepatectomy.

Prolyl hydroxylase activity and collagen biosynthesis have been measured at intervals following 2 extents of hepatic resection in rats. Prolyl hydroxylase activity is validated as a measure of collagen biosynthesis. The levels rise to a peak at 72 h and thereafter decline. The implications for the process of liver regeneration are discussed.     

Reactions of pulmonary phagocytes following partial hepatectomy

Zymosan administration into the trachea of rats led to intensified infiltration of the lungs by macrophages which migrated to alveolar and bronchial cavities, and the inflow of these cells was accompanied by their increased chemiluminescence and by elevation in acid phosphatase and cathepsin D activities. After partial hepatectomy, the zymosan-induced inflow of cells into the airways was much less pronounced, and no enzyme activation was observed, but the chemiluminescence of airway cells remained high. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 5, pp. 477–479, May, 1995 Presented by V. P. Kaznacheev, Member of the Russian Academy of Medical Sciences     

Effects of partial hepatectomy on plasma fibronectin concentrations in the rat.

Rats were subjected to 60% partial hepatectomy. In the immediate postoperative period, there was a small decline in plasma fibronectin concentrations, which was normalized already 12 h post-operatively. Metabolic labelling of fibronectin with 35S-methionine showed that the rate of incorporation of label was unchanged after partial hepatectomy. However, when the abdominal viscera were excluded from the circulation, no incorporation of label was found. These results show that the rate of fibronectin biosynthesis has the rapid regulation characteristics of an acute phase reactant. Peripheral tissues do not contribute significantly to the plasma fibronectin concentration. Intra- or retro-peritoneal viscera, most likely the liver, are responsible for the synthesis of rat plasma fibronectin.     

Effects of partial hepatectomy on the immune responses in mice

Experiments were performed to investigate the immune responses occurring as a result of partial hepatectomy (HEP) in mice. On Day 12 mice subjected to HEP showed a twofold rise in serum levels of IgG when compared with sham-operated (ShO) controls. The effects of HEP on specific antibody production following a single immunization with sheep red blood cells (SRBCs) were investigated. An early appearance of direct (IgM) splenic plaque-forming cells (PFCs) and significantly elevated indirect (IgG) PFCs were found in HEP mice. Elevated, early-appearing mercaptoethanol-resistant (IgG) hemagglutinating antibodies were also demonstrated in the sera of HEP mice. In addition to these findings our study showed that humoral and cell-mediated responses are affected by HEP in opposing fashion. Partial hepatectomy performed immediately after skin grafting suppressed a first set allograft rejection in mice. Furthermore, inhibited delayed-type hypersensitivity (DTH) response against SRBCs, as evaluated by a footpad weight assay, was demonstrated in HEP mice compared with the ShO controls. When SRBC-primed mice were partially hepatectomized 15 days later, they responded in a manner typical of the secondary immune response, showing an increased production of indirect (IgG) splenic PFCs. A similar anamnestic response was observed in mice sensitized with leptospiral antigen 50 days prior to HEP or exposed to carbon tetrachloride (CCl4) hepatotoxin. The mice responded by elevated serum IgG-specific antibodies as measured by solid-phase enzyme-linked immunosorbent assay (ELISA). Since HEP induced in mice immunological disturbances similar to those associated with liver disease, it is suggested that partial hepatectomy creating liver deficiency followed by regeneration may be a useful experimental model to study the immune status of various forms of hepatic damage.     

Type 1 plasminogen activator inhibitor gene expression following partial hepatectomy.

A murine model of partial hepatectomy (PH) was employed to investigate type 1 plasminogen activator inhibitor (PAI-1) gene expression in regenerating liver. Mice were anesthetized, and a portion of the left lobe of the liver was ligated and resected distal to the ligature, and at various times thereafter, total liver RNA was prepared and analyzed by Northern blotting. PH caused a transient increase in PAI-1 messenger (m)RNA that was apparent within 1 to 2 hours after surgery, was maximal at 8 hours (ninefold increase over sham-operated controls), and then slowly declined. Analysis of discrete liver segments demonstrated much greater induction of PAI-1 mRNA in the region adjacent to PH than in more distal regions. Further analysis of the adjacent tissue by in situ hybridization revealed that PAI-1 mRNA was induced primarily in hepatocytes in the transition zone created by the occluding hemostatic ligature between viable and necrotic tissue. Expression of PAI-1 mRNA could also be detected in this transition zone in capsular mesothelial cells, subcapsular hepatocytes, and venous endothelial cells bordering the area. A much weaker signal was evident in hepatocytes dispersed throughout the remaining intact lobes of PH mice, and no signal was detected in the livers of sham-operated mice. These observations suggest that PAI-1 may be of importance in local tissue remodeling events accompanying liver regeneration.     

大鼠肝部分切除后血清氨基酸的代谢变化

本实验研究了大鼠肝部分切除后72小时血清氨基酸的代谢变化。实验分三纰:正常对照组、假手术组和肝部分切除组。用氨基酸自动分析仪测定了主动脉、下腔脉静,门静脉和肝静脉血清20种氨基酸浓度。结果表明大鼠肝部分切除后72小时,上述血管血清氨基酸浓度均显著升高。肝摄取氨基酸总量显著增加,门静脉区内脏释放氨基酸总量占肝摄取量的87%。二者呈正相关。外周血管血清必需与非必需氨基酸比值和支链与芳香族氨基酸比值均显著下降。外周组织对支链氨基酸摄取严重抑制,而肝脏摄取则显著增加,这不仅为肝再生提供充分支链氨基酸的供应,而且促进肝蛋白质的合成。门静脉区内脏释放和肝脏摄取丙氨酸的量均显著增加,从而为肝糖原异生提供原料的供应。     

Effects of partial hepatectomy on plasma fibronectin concentrations in the rat

Rats were subjected to 60% partial hepatectomy. In the immediate postoperative period, there was a small decline in plasma fibronectin concentrations, which was normalized already 12 h post-operatively. Metabolic labelling of fibronectin with 35S-methionine showed that the rate of incorporation of label was unchanged after partial hepatectomy. However, when the abdominal viscera were excluded from the circulation, no incorporation of label was found. These results show that the rate of fibronectin biosynthesis has the rapid regulation characteristics of an acute phase reactant. Peripheral tissues do not contribute significantly to the plasma fibronectin concentration. Intra- or retro-peritoneal viscera, most likely the liver, are responsible for the synthesis of rat plasma fibronectin.