Expression of hepatic thrombopoietin mRNA in primary cultured hepatocytes and in rats with acute liver injury or bone marrow suppression with or without cirrhosis

Analysis of predictors after partial splenic embolization for thrombocytopenia with liver cirrhosis

Blood transfusion, splenectomy, and partial splenic embolization (PSE) are generally performed for thrombocytopenia in patients with cirrhosis. Recently, thrombopoietin (TPO) agonists have become available, and investigations of patients who would benefit from them are necessary. Therefore, it is important to understand the fluctuations in cytokine levels associated with PSE. Therefore, fluctuations in platelet-associated immunoglobulin G (PAIgG), interleukin 6 (IL-6), and TPO levels with PSE were analyzed in this study. The study included 110 patients with liver cirrhosis and thrombocytopenia, with the aim of improving platelet counts. Fluctuations in PAIgG, IL-6, and TPO levels were investigated. The average splenic embolization ratio was 58.0% in patients with PSE. The platelet count rose significantly from 6.95 [5.40, 8.60] × 104/mL to 14.05 [10.43, 18.05] × 104/mL (P < .01), IL-6 rose significantly from 3.56 [2.53, 7.33] pg/mL to 18.90 [9.17, 32.95] pg/mL (P < .01), TPO rose significantly from 0.82 [0.52, 1.21] fmol/mL to 1.58 [0.97, 2.26] fmol/mL (P < .01), and PAIgG decreased significantly from 64.20 [38.33, 118.75] ng/107 cells to 37.50 [22.25, 70.00] ng/107 cells (P < .01). On multivariate analysis of factors related to the rate of platelet increase with PSE, primary biliary cholangitis (B = 0.475, P < .01), splenic embolization ratio (B = 0.75, P < .01), IL-6 change ratio (B = 0.019, P < .01), and PAIgG change ratio (B = -0.325, P < .01) were significant. When attempting to improve thrombocytopenia with PSE, adequate splenic embolization needs to be obtained together with improvements in IL-6, PAIgG, and TPO levels. With unsatisfactory improvement in thrombocytopenia, TPO agonist administration was considered.

Thrombocytopenia in chronic liver disease: Physiopathology and new therapeutic strategies before invasive procedures

Chronic liver disease is characterized by several hematological derangements resulting in a complex and barely rebalanced haemostatic environment. Thrombocytopenia is the most common abnormality observed in these patients and recent advances have led to researchers focus the attention on the multifactorial origin of thrombocytopenia and on the key role of thrombopoietin (TPO) in its physiopathology. Severe thrombocytopenia (platelet count < 50000/μL) complicates the management of patients with chronic liver disease by increasing the potential risk of bleeding for invasive procedures, which may be therefore delayed or canceled even if lifesaving. In the very last years, the development of new drugs which exceed the limits of the current standard of care (platelet transfusions, either immediately before or during the procedure) paves the way to a new scenario in the management of this population of patients. Novel agents, such as the TPO-receptor agonists avatrombopag and lusutrombopag, have been developed in order to increase platelet production as an alternative to platelet transfusions. These agents have demonstrated a good profile in terms of efficacy and safety and will hopefully allow reducing limitations and risks associated with platelet transfusion, without any delay in scheduled interventions. Altogether, it is expected that patients with chronic liver disease will be able to face invasive procedures with one more string in their bow.

[Splenomegaly and thrombocytopenia in patients with liver cirrhosis]

BACKGROUND/AIM

Splenomegaly is a frequent finding in patients with liver cirrhosis and portal hypertension and may cause hypersplenism. The occurrence of thrombocytopenia in those patients can be considered as an event with multiple etiologies. Two mechanisms may act alone or synergistically with splenic sequestration. One is central which involves either myelosuppression because of hepatitis viruses or the toxic effects of alcohol abuse on the bone marrow. The second one involves the presence of antibodies against platelets. It also depends upon the stage and etiology of liver disease. The aim of the study was to investigate a correlation between the platelet count and spleen size and the risk factors for thrombocytopenia in patients with liver cirrhosis.

METHODS

We studied 40 patients with decompensated liver cirrhosis who were hospitalized in the Department of Gastroenterohepatology. The liver function was graded according to Child Pugh score. Spleen size was defined ultrasonografically on the basis of craniocaudal length. Suspicion of portal hypertension was present when longitudinal spleen length was more than 11 cm. Thrombocytopenia was determined by platelet count under 150,000/mL.

RESULTS

We did not find any significant correlation between hepatic dysfunction and spleen size (p = 0.9), and between hepatic dysfunction and thrombocytopenia (p = 0.17). Our study did not find any significant correlation between spleen size and peripheral platelet count (p = 0.5), but we found a significant correlation between thrombocytopenia and etiology of cirrhosis - decreased platelet count was more common among patients with cirrhosis of alcoholic etiology than in other etiologies of cirrhosis (p = 0.001).

CONCLUSION

According to our study, liver cirrhosis, portal hypertension and thrombocytopenia could be present even in the absence of enlarged spleen suggesting the involvement of other mechanisms of decreasing platelet account.

Hepatocyte growth factor accelerates thrombopoiesis in transgenic mice

Hepatocyte growth factor (HGF) is one of the potent growth factors for liver regeneration and has a strong effect on epithelial and nonepithelial cells. As one of the pleiotropic functions, HGF acts as a hematopoietic regulator in the proliferation and differentiation of hematopoietic progenitors. However, the effect of HGF on the thrombopoietic function remains unclear. The correlation between HGF and thrombopoiesis was investigated in transgenic (TG) mice overexpressing murine HGF controlled by the murine HGF by the metallothionein promoter. Furthermore, the mechanism of thrombocytosis induced by HGF in vitro was analyzed in hepatoma cell line HepG2. Both the platelet count and the serum thrombopoietin (TPO) concentration were significantly higher in TG than in the wild type (WT) control mice. In the liver and spleen, the expression of TPOmRNA in TG was higher than that in WT by real-time polymerase chain reaction. The expressions of transcriptional factor of TPO, GABP-alpha/beta were more increased in TG liver compared to WT. In an in vitro study, HGF induced TPO and GABP-alpha/beta expression and enhanced TPO promoter activity. Therefore, HGF induced thrombopoiesis accompanied with the overexpression of TPO through GABP stimulation.

Review article: thrombocytopenia in chronic liver disease and pharmacologic treatment options

In patients with liver disease, thrombocytopenia is a clinical feature that may represent an obstacle to invasive diagnostic or therapeutic procedures, chemotherapy, and anti-viral treatment. Stimulation of the bone marrow is the most promising therapeutic intervention for thrombocytopenia in patients with chronic liver disease. The description of thrombopoietin and its (de)regulation in patients with chronic liver disease have disclosed new treatment opportunities. Indeed, pharmacologic treatment options for thrombocytopenia can be divided into treatments targeted at the thrombopoietin receptor (synthetic thrombopoietins and thrombopoietin-mimetic agents), and use of cytokines with general thrombopoietic potential. Unfortunately, use of synthetic thrombopoietin was hampered by the development of neutralizing antibodies, and thrombopoietin mimetic agents have not yet entered clinical studies. Interleukin-11 proved to be useful in increasing platelet count in patients with chronic liver disease, although its use is limited by side-effects. Erythropoietin has shown promising results in improving thrombocytopenia in cirrhotic patients. In patients with chronic liver disease, safe and well-tolerated treatments aimed at improving thrombocytopenia are still lacking. Larger studies are needed to evaluate and better characterize the thrombopoietic potential of erythropoietin. Human studies with thrombopoietin-mimetic agents are eagerly awaited in order to assess both effectiveness and safety of these drugs.

Thrombopoietin production in wild-type and interleukin-6 knockout mice with acute inflammation

Clinical and laboratory studies indicate that thrombopoietin (TPO) gene expression increases during inflammation. To clarify the role of interleukin 6 (IL-6) in this process, blood cell counts, plasma TPO concentrations, and hepatic and renal TPO mRNA levels were investigated in wild-type and IL-6 knockout mice, with sterile abscesses produced by subcutaneous injection of turpentine oil. Treatment did not cause a change in blood cell counts during the 72 h period of observation. The numbers of thrombocytes and erythrocytes were slightly lower in the IL-6 knockout mice than in the wild-type littermates under all conditions. Plasma IL-6 and TPO concentrations increased on turpentine injection only in the wild-type mice. In addition, turpentine treatment of these caused an increase in hepatic TPO mRNA levels as assessed by competitive polymerase chain reaction (RT-PCR) and real-time PCR, whereas renal TPO mRNA levels were unaltered. TPO mRNA levels did not increase in the livers of IL-6 knockout mice on turpentine treatment. These results support the concept that TPO behaves like an acute-phase protein in that its synthesis is induced by IL-6 in the liver.

Thrombopoietin production in human hepatic cell cultures (HepG2) is resistant to IFN-alpha, IFN-beta, and IFN-gamma treatment

Thrombocytopenia is an important complication of interferon (IFN) therapy for chronic viral hepatitis. To study whether IFN interferes with hepatic thrombopoietin (TPO) synthesis, we used the human hepatoma cell line HepG2. Our results show that IFN-alpha, IFN-beta, or IFN-gamma did not impair TPO mRNA expression, as determined by quantitative RT-PCR, even when high IFN doses (up to 5000 U/ml) or long-term incubations (up to 14 days) were applied. Neither was the rate of secretion of immunoreactive TPO reduced on IFN treatment. These findings support the concept that IFNs primarily mediate effects on megakaryocytic cells and platelets rather than on TPO-producing hepatocytes.

Role of blood platelets in infection and inflammation

Blood platelets are here presented as active players in antimicrobial host defense and the induction of inflammation and tissue repair in addition to their participation in hemostasis. Megakaryopoiesis is inhibited after acute infection with viruses or bacteria. In contrast, chronic inflammation is often associated with reactive thrombocytosis. Platelets can bind and internalize pathogens and release microbicidal proteins that kill certain bacteria and fungi. By making cell-cell contacts with leukocytes and endothelial cells, platelets assist white blood cells in rolling, arrest and transmigration. On stimulation by bacteria or thrombin, platelets release the content of their alpha-granules, which include an arsenal of bioactive peptides, such as CC-chemokines and CXC-chemokines and growth factors for endothelial cells, smooth muscle cells and fibroblasts. Thus, integral to innate immunity, the tiny little platelets may become bombshells when irritated by pathogens.

Quantification of hepatic thrombopoietin mRNA transcripts in patients with chronic liver diseases shows maintained gene expression in different etiologies of liver cirrhosis

BACKGROUND/AIMS

Platelet production is regulated by thrombopoietin (TPO), which is primarily synthesized in the liver. The TPO in patients with liver diseases could possibly be owing to impaired hepatic TPO production. As we reported previously, TPO serum levels are not decreased in patients with liver diseases compared with healthy controls and do not depend on the stage of cirrhosis or platelet count, but are highly elevated in patients with chronic virus hepatitis.

METHODS

To study possible mechanisms, we measured hepatic TPO mRNA levels in liver tissue samples from 31 liver cirrhosis patients by quantitative TaqMan real-time RT-PCR and corresponding serum TPO concentrations by ELISA.

RESULTS

Median TPO serum levels were elevated in patients with viral hepatitis (n = 12) compared with patients with a biliary (n = 10), alcoholic (n = 6) or other (n = 3) disease etiology, while hepatic TPO mRNA levels did not differ. The TPO mRNA levels in patients with chronic liver diseases were not different from normal liver tissue sample. The TPO mRNA and TPO serum level did not correlate.

CONCLUSIONS

We conclude that hepatic TPO gene expression appears to be maintained on a constitutive transcriptional level in patients with liver diseases and does not change dependent on disease etiology.