Quantitative and Qualitative Analysis of Platelet GPIb and von Willebrand Factor in Liver Cirrhosis

Reduced platelet activation and platelet aggregation in patients with alcoholic liver cirrhosis

Results from previous studies regarding platelet function in liver cirrhosis are discordant. The aim was to investigate platelet activation and platelet aggregation in patients with alcoholic liver cirrhosis. We included 27 patients with alcoholic liver cirrhosis and 22 healthy individuals. A recently established flow cytometric approach was used to measure platelet activation and platelet aggregation independent of sample platelet count. Platelet aggregation was further investigated using light transmission aggregometry (LTA) (for platelet count >100 × 10⁹/L). Platelet agonists were adenosine diphosphate, thrombin receptor-activating peptide, arachidonic acid, collagen, and collagen-related peptide. Patients had lower median platelet count than healthy individuals, 125 × 10⁹/L (interquartile range [IQR] 90-185) versus 240 × 10⁹ (IQR 204-285), p < 0.001. Platelet activation levels in stimulated samples were lower in patients versus healthy individuals, e.g., after collagen-related peptide stimulation, the median percentage of platelets positive for activated glycoprotein IIb/IIIa was 85% (IQR 70-94) in patients versus 97% (IQR 94-99) in healthy individuals, p < 0.001; lower platelet activation capacity being associated with low platelet count and Child-Pugh class B/C cirrhosis. Flow cytometric platelet aggregation was reduced in patients for collagen-related peptide and for adenosine diphosphate, e.g., platelet aggregation (mean ± standard deviation) was 57% ± 4 in patients versus 70% ± 1 in healthy individuals for collagen-related peptide, p = 0.01. Light LTA showed reduced collagen-induced platelet aggregation in some patients compared with healthy individuals. In conclusion, platelet function was reduced in some patients with alcoholic liver cirrhosis and the severity was associated with platelet count and severity of liver cirrhosis.

von Willebrand factor as a novel noninvasive predictor of portal hypertension and esophageal varices in hepatitis B patients with cirrhosis

OBJECTIVE

At present, there is no perfect noninvasive method to assess portal hypertension and esophageal varices. Early predicting esophageal varices can provide evidence for managing cirrhotic patients. We aimed to further investigate von Willebrand factor (vWF) as a noninvasive predictor of portal hypertension, especially of esophageal varices.

MATERIAL AND METHODS

A total of 60 hepatitis B patients with cirrhosis and 45 healthy subjects were enrolled in this study. Levels of six markers were examined. All patients underwent hepatic venous pressure gradient (HVPG) and esophagogastroduodenoscopy. We evaluated the performance of six factors for diagnosis of portal hypertension and esophageal varices. The vWF levels in liver tissues were observed by immunohistochemistry. Correlations between the level of vWF in liver tissues and HVPG and between levels of vWF in tissues and plasma were examined.

RESULTS

Cutoff values of plasma vWF (1510.5 mU/mL and 1701 mU/mL) showed high positive predictive value (PPV, 90.2% and 87.5%) in predicting clinically significant portal hypertension and severe portal hypertension. Cutoff values of vWF (1414 mU/ml and 1990 mU/mL, PPV 90.3% and 86.3%, respectively) were provided to detect the presence and degree of esophageal varices. Linear correlations were observed between levels of vWF in liver tissues and HVPG (r(2) = 0.552, p < 0.001) and between the level of vWF in liver tissues and in plasma (r(2) = 0.461, p < 0.001).

CONCLUSION

The vWF is a noninvasive predictor of portal hypertension and esophageal varices in hepatitis B patients with cirrhosis. Increased levels of vWF in liver tissues may induce the elevated plasma vWF levels, but molecular mechanism is needed for further study.

Review article: blood platelet number and function in chronic liver disease and cirrhosis

BACKGROUND

The liver plays a central role in coagulation and fibrinolysis but is also closely intertwined with the function and number of blood platelets.

AIM

To describe and integrate all literature concerning blood platelets and liver disease by performing a thorough literature research.

METHODS

A thorough literature research on 'blood platelets' and 'liver disease' was performed.

RESULTS

Thrombocytopenia is a marked feature of chronic liver disease and cirrhosis. Traditionally, this thrombocytopenia was attributed to passive platelet sequestration in the spleen. More recent insights suggest an increased platelet breakdown and to a lesser extent decreased platelet production plays a more important role. Besides the reduction in number, other studies suggest functional platelet defects. This platelet dysfunction is probably both intrinsic to the platelets and secondary to soluble plasma factors. It reflects not only a decrease in aggregability, but also an activation of the intrinsic inhibitory pathways. The net effect, finally, is a decreased platelet function in the various types of chronic liver diseases and cirrhosis. Finally, recent data suggest that platelets are not only affected by but can also contribute to the liver disease process, as for instance, in viral hepatitis and cholestatic liver disease.

CONCLUSION

Platelet research in liver disease is a growing area of investigation and could provide new pathophysiological insights.

Elevated levels of von Willebrand Factor in cirrhosis support platelet adhesion despite reduced functional capacity

Cirrhosis of the liver is frequently accompanied by complex alterations in the hemostatic system, resulting in a bleeding tendency. Although many hemostatic changes in liver disease promote bleeding, compensatory mechanisms also are found, including high levels of the platelet adhesive protein von Willebrand Factor (VWF). However, conflicting reports on the functional properties of VWF in cirrhosis have appeared in literature. We have measured a panel of VWF parameters in plasma from patients with cirrhosis of varying severity and causes. Furthermore, we assessed the contribution of VWF to platelet adhesion, by measuring the ability of plasma from patients with cirrhosis to support adhesion of normal or patient platelets under flow conditions. VWF antigen levels were strongly increased in patients with cirrhosis. In contrast, the relative collagen binding activity, as well as the relative ristocetin cofactor activity, was significantly lower in patients as compared with controls, indicating loss of function. Accordingly, patients had a reduced fraction of high-molecular-weight VWF multimers. Both strongly elevated and reduced activity and antigen levels of the VWF cleaving protease ADAMTS13 were found in individual patients. Adhesion of either normal or patient platelets to a collagen surface was substantially increased when these platelets were resuspended in plasma of patients with cirrhosis, as compared with control plasma. In conclusion, highly elevated levels of VWF in patients with cirrhosis contribute to the induction of primary hemostasis despite reduced functional properties of the molecule. This phenomenon might compensate for defects in platelet number and function in patients with cirrhosis.

Recipient levels and function of von Willebrand factor prior to liver transplantation and its consumption in the course of grafting correlate with hepatocellular damage and outcome*

Von Willebrand factor (vWF) is a major platelet adhesion molecule at sites of vascular injury, such as observed in ischemia/reperfusion injury following orthotopic liver transplantation (OLT). Thirty-three OLT patients were divided into groups with elevated or low markers of hepatocellular damage (high and low-HD). Whole-blood aggregometry was performed to evaluate platelet function. Multimeric analysis was utilized to evaluate functional vWF levels in the course of OLT. Donor and recipient demographics were comparable among groups. Low-HD patients demonstrated better preserved coagulation parameters on POD 1-6 if contrasted to high-HD patients. One year graft survival for the high-HD group was lower than low-HD patients (P = 0.037). Preoperative vWF-dependent platelet aggregation and functional vWF plasma levels correlated directly with alanine transaminase levels early after OLT as did the decrease of functional vWF to reperfusion. In summary, these data suggest that vWF may serve as a significant mediator of platelet recruitment and hepatocellular injury in the graft following reperfusion.

Short- and long-term effects of therapy with interferon-alpha and pegylated interferon-alpha/ribavirin on platelet plug formation and von Willebrand factor release in patients with chronic hepatitis C

BACKGROUND

A pegylated interferon-alpha-induced decrease in platelet counts may become a limiting factor for continuation of therapy.

AIM

To evaluate the effect of pegylated interferon-alpha administration on platelet plug formation and von Willebrand factor antigen release in patients with chronic hepatitis C.

METHODS

Thirty patients with chronic hepatitis C (genotype 1; fibrosis 1-3: n = 16, cirrhosis: n = 14) received a single dose of 9 MU interferon-alpha2a, followed by weekly administration of 180 mug of pegylated interferon-alpha2a/ribavirin for 48 weeks. Platelet counts, platelet function (collagen-epinephrine-induced closure time) and von Willebrand factor antigen were measured.

RESULTS

Platelet counts and collagen-epinephrine-induced closure time decreased by 13% and 16%, respectively, 24 h after the first dose of interferon-alpha2a, and von Willebrand factor antigen levels increased by 31% (P < 0.01) compared with baseline. During a 48-week observation period, platelet counts decreased by a maximum of 33% (P < 0.001), von Willebrand factor antigen levels increased by 69% (P < 0.001) whereas collagen-epinephrine-induced closure time did not change. In noncirrhotic patients, the increase of von Willebrand factor antigen levels was maintained throughout therapy without a change in collagen-epinephrine-induced closure time. In contrast, in cirrhotics, von Willebrand factor antigen levels did not increase, while collagen-epinephrine-induced closure time was prolonged.

CONCLUSION

Single-dose interferon-alpha decreases platelet counts but improves platelet function, possibly by the release of von Willebrand factor antigen. Accordingly, long-term antiviral treatment had no effect on collagen-epinephrine-induced closure time, despite the decrease in platelet count in noncirrhotic patients. Such a compensation of decreased platelet counts by increased von Willebrand factor antigen level did not occur in cirrhotics.

Von Willebrand factor in plasma and in liver tissue after partial hepatectomy in the rat

BACKGROUND/AIMS

Von Willebrand factor (vWf) is found in high levels in plasma of patients with acute and chronic liver disease. The role of vWf in liver injury and repair is unknown. We studied the effect of liver mass and remodeling on plasma and tissue vWf after partial hepatectomy.

METHODS

Rats were sacrificed postoperatively at intervals ranging from 60 min to 5 days, and vWf plasma levels were measured by enzyme-linked immunosorbent assay, using rabbit anti-human vWf, and by immunoperoxidase on cryosections, using rabbit anti-vWf/factor VIII. Northern blot hybridization was prepared with a complementary DNA specific to human vWf.

RESULTS

vWf plasma levels increased early after sham operation and after 70% partial hepatectomy. The highest levels were reached at 24 h, remaining high for 5 days. Immunostaining showed intense staining of sinusoidal lining cells 4 h after partial hepatectomy, remaining so for 5 days. Non-significant changes in overall liver messenger RNA expression of vWf were seen over 5 days in sham operation and partial hepatectomy.

CONCLUSIONS

After partial hepatectomy, plasma vWf is increased, probably due to both acute-phase reaction and decreased degradation. An increase in sinusoidal vWf immunostaining may suggest a role for this factor in tissue remodeling.

Von Willebrand factor could be an index of endothelial dysfunction in patients with cirrhosis: relationship to degree of liver failure and nitric oxide levels

BACKGROUND/AIMS

The aim of this study was to evaluate the relationship between plasma levels of von Willebrand factor (vWF), a marker of endothelial cell activation, and nitric oxide, a powerful vasodilator synthesized by endothelial cells, in 27 patients with cirrhosis at different stages of the disease. These results were compared with those of age-matched normal, healthy subjects (n=10).

METHODS

vWF:antigen was measured by electro-immunodiffusion test and serum nitrite and nitrate levels, the stable end products of nitric oxide metabolism, were determined by an enzymatic procedure.

RESULTS

vWF:antigen and nitrite/nitrate levels were significantly higher in cirrhotic patients (367+/-185% and 29.3+/-10.8 micromol/l) than in healthy subjects (92+/-20% and 19.2+/-8.3 micromol/l, p<0.05, respectively). Higher levels of vWF:antigen and nitrites/nitrates were observed in patients with more advanced degrees of liver failure, as reflected by quantitative Child-Pugh's score (516+/-154% and 38.3+/-7.8 micromol/l in Child-Pugh > or = 9 vs 227+/-61% and 21.0+/-6.1 micromol/l in Child-Pugh <9, p<0.001, respectively). Moreover, both endothelial-related factors were higher in patients with ascites than those without ascites (543+/-158% and 37.8+/-8.9 micromol/l vs 262+/-103% and 24.4+/-8.8 micromol/l, p<0.001, respectively). In the overall series, a highly significant linear correlation between nitrites/nitrates and vWF:antigen levels was observed in patients with cirrhosis (r=0.79, p<0.001).

CONCLUSIONS

These results support a cirrhosis-related endothelial dysfunction and suggest that plasma vWF measurement could be useful as a marker of endothelial disturbance in patients with cirrhosis.

Existence of a platelet-adhesion defect in patients with cirrhosis independent of hematocrit: studies under flow conditions

A defect in hemostasis has been repeatedly reported in patients with cirrhosis. However, the nature of this defect has not been fully characterized. We explored adhesive and cohesive functions of platelets from cirrhotic patients at different stages of disease development. The response of platelets to standard activating agents was tested by aggregometric procedures. The interaction of platelets with subendothelial components was explored in a perfusion system in which blood was exposed (shear rate, 800/s; 10 minutes) to denuded segments of rabbit aorta. Platelet interactions in these perfusions were analyzed morphometrically. Results were always compared with those obtained in similar studies using blood obtained from healthy subjects. Aggregation studies showed abnormal responses for single or several agonists. Abnormalities in aggregation were more evident in patients with severe disease (Child-Pugh class C), although they occasionally were abnormal for single agonists (ADP or U46619) in patients with less severe disease (Child-Pugh classes A or B). All the patient classes showed impaired platelet-subendothelial interactions (P < .01 vs. healthy subjects) that were not justified by the relative thrombocytopenia present in the more severely affected patients. Experimental increases in hematocrit in patients at stages B and C did not improve platelet-subendothelial interactions. Platelets from cirrhotic patients interact defectively with subendothelial components under flow conditions. The adhesion defect is more evident and consistent than the aggregation defects and may already be present in patients with mild liver failure. This adhesion defect may contribute to the defective hemostasis observed in cirrhotic patients.

von Willebrand's disease in the dog and cat

Von Willebrand's disease (vWD) is a bleeding disorder that is recognized commonly in dogs but rarely in cats. This article presents the pathophysiology and clinical features of vWD, including a discussion of inherited and acquired types of vWD. Laboratory evaluation and treatment of vWD are reviewed.