Synthesis of procoagulant factor VIII, factor VIII related antigen and other coagulation factors by the isolated perfused rat liver

[Rapid diagnosis of acquired hemophilia A with ClotPro viscoelastometry analyser]

Acquired hemophilia A is a rare condition with the capability of bringing about life-threatening bleeding in the perioperative period, posing a significant challenge for the caregiver anesthetist to identify the underlying cause. However, a quick diagnosis might be supported by viscoelastometry by raising the suspicion of severe and isolated deficiency of the intrinsic coagulation pathway, requiring a prompt consultation with a hematology center. Special laboratory tests of hemostasis are helpful in the differential diagnosis of the detected coagulation disorder. Nevertheless, bypassing agents have gained a crucial role in the treatment of major perioperative blood losses by bypassing Factor VIII inactivated by autoantibodies and thus, initiating coagulation. Early goal-directed supplementation of depleted coagulation factors must also be kept in the focus of the therapy. Orv Hetil. 2023; 164(40): 1600-1604.

Factor VIII can be synthesized in hemophilia A mice liver by bone marrow progenitor cell-derived hepatocytes and sinusoidal endothelial cells

Hemophilia A (HA) is caused by mutation in factor VIII (FVIII) gene in humans; it leads to inadequate synthesis of active protein. Liver is the primary site of FVIII synthesis; however, the specific cell types responsible for its synthesis remain controversial. We propose that the severity of the bleeding disorder could be ameliorated by partial replacement of mutated liver cells by healthy cells in HA mice. The aim of this investigation was to study the cellular origin of FVIII by examining bone marrow cell therapy for treatment of HA in mice. Recipient liver was perturbed with either acetaminophen or monocrotaline to facilitate the engraftment and differentiation of lineage-depleted (Lin(-)) enhanced green fluorescent protein-expressing bone marrow cells. Immunohistochemical analysis of liver tissue was conducted to identify the donor-derived cells that expressed FVIII. This identification was confirmed by transmission electron microscopy and quantitative gene expression analysis. The phenotypic correction in HA mice was determined by tail-clip challenge and FVIII level in plasma by Chromogenix and activated partial thromboplastin time assays. Immunohistochemical analysis showed that von Willebrand factor and cytokeratin-18-expressing endothelial cells and hepatocytes, respectively, were obtained from BM-derived cells. Both cell types expressed FVIII light chain mRNA and protein, which was further confirmed by transmission electron microscopy. The transplanted HA mice showed FVIII activity in plasma (P<0.01) and survived tail-clip challenge (P<0.001). Thus, we conclude that BM-derived hepatocytes and endothelial cells can synthesize FVIII in liver and correct bleeding phenotype in HA mice.

The therapeutic effect of bone marrow-derived liver cells in the phenotypic correction of murine hemophilia A

The transdifferentiation of bone marrow cells (BMCs) into hepatocytes has created enormous interest in applying this process to the development of cellular medicine for degenerative and genetic diseases. Because the liver is the primary site of factor VIII (FVIII) synthesis, we hypothesized that the partial replacement of mutated liver cells by healthy cells in hemophilia A mice could manage the severity of the bleeding disorder. We perturbed the host liver with acetaminophen to facilitate the engraftment and hepatic differentiation of lineage-depleted enhanced green fluorescent protein-expressing BMCs. Immunohistochemistry experiments with the liver tissue showed that the donor-derived cells expressed the markers of both hepatocytes (albumin and cytokeratin-18) and endothelial cells (von Willebrand factor). The results of fluorescent in situ hybridization and immunocytochemistry experiments suggested that differentiation was direct in this model. The BMC-recipient mice expressed FVIII protein and survived in a tail clip challenge experiment. Furthermore, a coagulation assay confirmed that the plasma FVIII activity was maintained at 20.4% (+/- 3.6%) of normal pooled plasma activity for more than a year without forming its inhibitor. Overall, this report demonstrated that BMCs rescued the bleeding phenotype in hemophilia A mice, suggesting a potential therapy for this and other related disorders.

Expression of factor X in both the rat brain and cells of the central nervous system

Prothrombin is expressed in the central and peripheral nervous systems. However, the mechanism responsible for the activation of prothrombin to thrombin by the activated form of factor X in the central and peripheral nervous systems remains to be explored. Here, we investigated the expression of factor X mRNA in the brain and some cell lines derived from the central nervous system. Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated the expression of mRNA encoding factor X in the rat brain, A172 (human glioblastoma) and GOTO (human neuroblastoma) cells. The sequences of PCR-derived fragments were identical to those reported for rat and human factor X. These results indicated the synthesis of factor X in the cells of the central nervous system.

Immunohistochemical studies of human tissues with antibody to factor Xa

Factor Xa is a serine proteinase which functions principally at coagulation cascades. Factor Xa-like immunoreactivity has been examined in several human organs. Antibodies to the Factor stained macrophages in some tissues examined, including microglia in the brain white matter. They also stained epithelial cells in the nose, bronchus and duodenum. Some brainstem neurons, such as those in the oculomotor nucleus, substantia nigra and pontine nucleus, were also positive for the Factor. As reported by others, these results suggest that factor Xa may have pleiotrophic functions. Furthermore, the prefential localization to epithelium in the nose and bronchus is interesting in view of the previous notion that several viruses targeting the respiratory tract require factor Xa-like cellular proteinases for their replication and spread.

Secretion of coagulant factor VIII activity and antigen by in vitro cultivated rat liver sinusoidal endothelial cells

Different types of liver cells and a few extrahepatic cell types were analysed for the presence and production of factor VIII activity (VIII:C). Only freshly prepared suspensions of rat liver sinusoidal cells and pure monolayer cultures of rat liver endothelial cells (LEC) were found to contain and secrete detectable amounts of the coagulation factor. Secretion of VIII:C by cultured LEC was inhibited by cycloheximide and by monensin. Constant levels of VIII:C were produced for at least 48 h suggesting continuous synthesis rather than a burst release of stored material. VIII:C, as measured spectro-photometrically by conversion of X to Xa, was inhibited by anti-human VIII:C antiserum. Indirect immunocytochemistry using this antiserum gave positive staining only with LEC. Immunoprecipitation of metabolically labelled proteins in conditioned rat LEC medium with the anti human VIII:C antiserum revealed the presence of proteins of similar sizes to those reported for human VIII:C. These results indicate that rat LEC are an important site for production and secretion of procoagulant factor VIII and are not only a site for storage and release of the factor. The established conditions for synthesis of VIII:C in in vitro cultivated rat LEC should provide the means to study the regulation of VIII:C synthesis.

Molecular pathology and immunology of factor VIII (hemophilia A and factor VIII inhibitors)

Factor VIII is a large procoagulant glycoprotein that circulates in plasma in a noncovalent complex with von Willebrand factor. It is essential for the efficient cleavage of coagulation factor X by factor IXa, and its absence causes a severe bleeding disorder. Plasma factor VIII is reduced from the normal range of approximately 100 to 200 ng/ml in patients with the hereditary coagulation defect, hemophilia A, as well as in patients who develop autoantibodies that inactivate factor VIII. The understanding of factor VIII structure has been enhanced by recent studies that have characterized the X chromosome gene responsible for its synthesis, and preliminary information is now available about specific genetic defects. The basis for antibody formation in approximately 15 per cent of repeatedly transfused hemophilic patients is less clear at this time, however, for these individuals appear to have a variety of genetic defects that are not characteristically different from the patients who do not develop inhibitors. Although the antibodies cause a serious problem for affected individuals, they have been very useful in characterizing normal factor VIII and nonfunctional factor VIII-like protein that is found in the plasmas of 10 per cent of patients with mild hemophilia. Moreover, they are very useful reagents that can be used for immunoassay of factor VIII that has been modified in ways that have destroyed its procoagulant function.

Studies on alterations in blood coagulative and fibrinolytic activities after single and multiple administrations of carbon tetrachloride in mice

The time course of alterations in coagulative and fiblinolytic activities was studied in CCl4-induced liver disease in mice. Liver disease was induced by administration of 20% CCl4 in olive oil (p.o.). After single administration of CCl4, significant prolongation of r and k values and decrease in the ma value of thromboelastogram and apparent prolongation of PT and PTT were seen at 24 hr. Fibrinogen content decreased from 12 to 72 hr after single administration, while a mild but significant decrease in fibrinogen was observed after multiple administrations. The activity of factor XIII increased from 5 to 12 hr and then decreased from 24 to 168 hr after single administration. The activity of the hepaplastintest and Antithrombin III decreased apparently after single and multiple administrations. The plasminogen content and the activity of alpha 2-plasmin inhibitor decreased severely after single and multiple administrations. These results indicate that the coagulative and fibrinolytic activities were decreased to the most lowest value at 24 or 48 hr after single administration of CCl4, and the severe suppression of fibrinolysis and the mild decrease in coagulative activity were observed after multiple administrations of CCl4. The reason for the different effects between single and multiple administrations on coagulative and fibrinolytic systems was discussed.

Rat coagulation factor V purification and production of the monospecific antiserum

An original method was applied to purify rat factor V. The final preparation had a sp. act. of 45 U/ml for a 2500-fold purification with a yield of 43%. The final product is partially activated since it is 4.7-fold activable by RVV-VAE vs 6.3 in plasma. It can explain the presence of some of the four slightly stained additional bands found in SDS-electrophoresis. Finally, results of the purification suggest that rat factor V is a 338,000 single chain glycoprotein with a strong molecular asymmetry. A factor V deficient fraction was produced and used to adsorb an anti-factor V antiserum. This adsorbed antiserum was found monospecific against purified rat factor V.

The effect of liver disease on factors V, VIII and protein C

The components of the factor VIII complex were estimated by immuno- and bioassays in 85 patients with liver disease. The plasma concentrations of the antigens were elevated in 65% (VIII:CAg) and in 76% (VIIIR:Ag) of patients while the biological activities were elevated in only 14% (VIII:C) and 15% (VIII:RiCof). There was no correlation with C-reactive protein, used as a measure of an acute phase reaction (X2 = 0.7; P = 0.1); or with severity of liver disease as judged by prothrombin ratio (P = 1.0) but highest values were observed in patients with cholestatic liver disease. Following parenteral vitamin K there was a significant fall in both the biological activity of VIIIC (36%) and of VIII:CAg (38%) in 13 vitamin K deficient patients (P less than 0.001) but no change in 23 vitamin K replete patients or in the VIIIR:Ag levels in either group. Factor V levels were lower in patients with parenchymal liver disease (0.54 +/- 0.1 units/ml, mean +/- SEM, n = 12; normal range 0.5-1.5 units/ml) than in patients with extrahepatic cholestasis who were vitamin K deficient (1.2 +/- 0.1 units/ml, P less than 0.0001). The levels of protein C antigen, the vitamin K dependent protease which inactivates factors VIII:C and V, was at the lower end of the range in both groups (0.7 +/- 0.1, mean +/- SEM, n = 18, normal range 0.74-1.4 units/ml). There was no significant change in either protein C antigen or factor V following vitamin K. The discrepancy between the biological activity of factor VIII and the antigen levels could represent accumulation of partially degraded factor VIII or production of a hypoactive form. There is no evidence that the reduction in VIIIC and VIII:CAg following vitamin K was mediated by protein C.

Distribution of factor VIII mRNA and antigen in human liver and other tissues

The cellular site of synthesis of factor VIII (FVIII:C; anti-haemophilic factor) has long been sought. Previous studies suggested the liver as a major site of synthesis, but extrahepatic sources such as spleen and lung have been implicated. Using an immunoradiometric assay (IRMA), we recently localized factor VIII antigen (FVIII:Ag, formerly FVIII:CAg), to whole perfused guinea pig liver and spleen, and to isolated hepatocytes, with lesser or trace amounts in other tissues. Using an immunohistological technique, Stel et al. detected FVIII:Ag in normal human liver sinusoidal endothelial cells, while Exner et al. detected FVIII:Ag by IRMA in extracts of human lymph nodes, lung, liver and spleen. The localization of antigen in tissues does not, however, distinguish sites of factor VIII synthesis from those of storage, and such experiments are subject to misinterpretation due to entrapment of plasma factor VIII in tissues. The recent cloning of the human factor VIII gene provides hybridization probes for the detection of factor VIII messenger RNA in cells, thus directly determining sites of synthesis. During complementary DNA cloning, we detected factor VIII mRNA in liver, and it has been localized by others in liver and placenta and in liver and kidney. In the present study, we detected factor VIII mRNA in isolated human hepatocytes, in spleen and in numerous tissues including lymph nodes and kidney, but not in white blood cells or cultured endothelial cells. We also found that the factor VIII, factor VII, factor IX and protein C antigens in liver are predominantly localized in hepatocytes, while very little von Willebrand factor antigen (vWF:Ag, formerly FVIIIR Ag) is detectable in this organ.

Experimental DMNA induced hepatic necrosis: early course of haemostatic disorders in the rat

The course of haemostasis defects was investigated in dimethylnitrosamine (DMNA) acute liver necrosis. Before 18 hr there was no evidence of disseminated intravascular coagulation (DIC) nor of abnormal fibrinolysis. At 12 hr the level of the vitamin-K-dependent factors (factors II, VII, IX and X) was reduced to 25-63% of control. Factors V and VIII:C levels decreased to about 10 and 20% by 12 hr. Factor V was the only molecule which decreased significantly by 6 hr. The rapid decrease of these proteins might be related to an early parenchymal functional impairment attested by early structural lesions observed in the endoplasmic reticulum and nucleus. The isolated decrease of factor V in the absence of any significant change in serum transaminase (SGOT and SGPT) levels is proposed, at least in the rat, as an early criterion of hepatic failure.

Localization of factor VIIIC: antigen in guinea-pig tissues and isolated liver cell fractions

Factor VIIIC:antigen (VIII:CAg) was estimated in guinea-pig tissues by an immunoradiometric assay using a human inhibitor antibody. In homogenized guinea-pig tissues, VIII:CAg was shown to be stable and to be predominantly located in the liver (9 +/- 1.2 units; mean +/- SEM, n = 8). Lesser amounts were detected in spleen (1.3 +/- 0.02 units), lung (0.6 +/- 0.07) and kidney (0.4 +/- 0.06). In isolated liver cell fractions separated by centrifugal elutriation VIII:CAg was mainly detected in the hepatocyte fraction (0.3 +/- 0.07 units/10(8) cells;mean +/- SEM, n = 5) and in lesser amounts in the endothelial (0.02 +/- 0.01 units/10(8) cells) and the Kupffer cell fractions (0.05 +/- 0.02 units/10(8) cells). The liver concentration of VIII:CAg was (0.17 +/- 0.02 units/g) which was 20% of the plasma concentration (0.96 +/- 0.01 units/ml, n = 8) suggesting that VIII:CAg may not be stored in the liver but is rapidly exported following synthesis.

Fibronectin and factor VIII-related antigen in liver cirrhosis and acute liver failure

The liver is involved in the turnover of fibronectin in two different ways: hepatic synthesis contributes substantially to the plasma fibronectin pool, while Kupffer-cells, performing an important role of the reticuloendothelial system, remove fibronectin opsonized material from the circulation. In 45 patients with histologically confirmed liver cirrhosis and six patients with acute liver failure due to intoxication we determined fibronectin concentration in plasma by electroimmunoassay and additionally measured factor VIII-related antigen, which is a large glycoprotein not synthesized in the liver. Fibronectin levels in plasma were decreased in liver cirrhosis. This decrease was correlated with the extent of porto-caval collateral circulation. Very low levels were found in patients with acute liver failure. Factor VIII-related antigen levels were greatly increased as a function of the hepatic insufficiency. Between both parameters there was a significant inverse correlation. It is concluded that the simultaneous determination of both proteins provides reliable information about the remaining liver function.

Detection of factor VIII/coagulant antigen in human liver tissue

Factor VIII, a high molecular weight glycoprotein complex which has an important role in haemostasis, consists of two immunologically as well as functionally discernible moieties that can be isolated separately. These are factor VIII/von Willebrand factor (FVIII/vWF) which is associated with the factor VIII-related antigen (FVIIIRAg), and the factor VIII/procoagulant activity (FVIII/C) which is associated with the factor VIII/procoagulant antigen (FVIII/CAg). The FVIII/C activity is decreased or absent in patients with haemophilia A (for a review of the structure and function of the factor VIII complex, see refs 1 and 2). Immunological techniques, combined with cell culture, have demonstrated that FVIIIRAg is present in and synthesized by endothelial cells and megakaryocytes. However, the organ and/or cell type responsible for the production of FVIII/C has not been established. Indirect evidence derived from organ transplantation in experimental animals suggests that the liver is the most likely organ for FVIII/C production. Here we have used a monoclonal antibody against FVIII/CAg in combination with a sensitive immunostaining technique to demonstrate the presence of FVIII/CAg in hepatic sinusoidal endothelial cells.

Multivariate analysis of clinical and biological data in cirrhotic patients: application to prognosis

One hundred and thirty-one patients underwent clinical and biological investigation with the following determinations performed on the same day; presence or absence of ascites, icterus and/or encephalopathy, coagulation study, biochemical determinations including albumin, transferrin and immunoglobulins immunoassays. The principal component analysis of biological data showed two sets of highly representative and inversely correlated data; one included coagulation tests, albumin and transferrin, and the other included immunoglobulin A/transferrin ratio, immunoglobulin A and total bilirubin. Clinical and biological data were computed using discriminant analysis between dead and survivors. Six parameters were then selected (total bilirubin, encephalopathy, factor V, AST, antithrombin III and transferrin) giving a correct prognosis in 81.6% (31/38) of cases in a test sample. Neither ascites nor immunoglobulins were useful for the estimation of the prognosis.

Synthesis and release of factor VIII by cultured human endothelial cells

Endothelial cells (ECs) derived from human umbilical veins were cultured in order to study the physiological control of factor VIII synthesis and release. The culture media were studied from multiple replicate cultures at confluence. Factor VIII related antigen (VIIIR:Ag) and factor VIII coagulant antigen (VIII:CAg) were measured by sensitive immunoradiometric assays. De novo synthesis of factor VIII related protein (VIII:R) was quantitated by incorporation of labelled amino acids into specific protein subunits. The following agents were added to the culture medium in a range of concentrations from physiological to pharmacological: adrenaline, 5 hydroxytryptamine, 2,3-DPG, cyclic AMP, thyroxine, hydrocortisone, and human growth hormone. None of them had any effect at any concentration on the rate of accumulation of VIIIR:Ag in the culture medium. Addition of exogenous factor VIII had no effect on do novo synthesis of VIII:R. VIII:CAg was found to be stable under the conditions of culture but none was released from the ECs. Long-term monocyte cultures also failed to release VIII:CAg. It appears that VIII:R is a constitutive gene product of umbilical vein endothelial cells and that VIII:CAg is not made by these cells.