Thymosin ß4 Exerts a Cytoprotective Function and Attenuates Liver Injury in Murine Hepatic Sinusoidal Obstruction Syndrome after Hematopoietic Stem Cell Transplantation.

Hepatic sinusoidal obstruction syndrome (HSOS) is a life-threatening complication that may occur after hematopoietic stem cell transplantation (HSCT). Hepatic sinusoidal endothelial cell (HSEC) injury and liver fibrosis are key mechanisms of HSOS. Thymosin ß4 (Tß4) is an active polypeptide that functions in a variety of pathologic and physiologic states, including inflammation regulation, anti-apoptosis, and anti-fibrosis. In this study, we found that Tß4 can stimulate HSEC proliferation, migration, and tube formation in vitro via activation of pro-survival signaling AKT (protein kinase B). In addition, Tß4 resisted γ irradiation-induced HSEC growth arrest and apoptosis in parallel with upregulation of anti-apoptotic protein B cell lymphoma extra-large (Bcl-xL) and B cell lymphoma-2 (Bcl-2), which may be associated with activation of AKT. More importantly, Tß4 significantly inhibited irradiation-induced pro-inflammatory cytokines in parallel with negative regulation of TLR4/MyD88/NF-κB and MAPK p38. Meanwhile, Tß4 reduced intracellular reactive oxygen species production and upregulated antioxidants in HSECs. Additionally, Tß4 inhibited irradiation-induced activation of hepatic stellate cells by downregulating the expression of fibrogenic markers α-SMA, PAI-1, and TGF-ß. In a murine HSOS model, levels of circulating alanine aminotransferase, aspartate aminotransferase, total bilirubin, and pro-inflammatory cytokines IL-6, IL-1ß, and TNF-α were significantly reduced after administration of Tß4 peptide; furthermore, Tß4 treatment successfully ameliorated HSEC injury, inflammatory damage, and fibrosis of the murine liver. Taken together, our findings indicate that Tß4 stimulates proliferation and angiogenesis of HSECs, exerts a cytoprotective effect, and attenuates liver injury in a murine HSOS model, suggesting that its use may be a potential strategy to prevent and treat HSOS after HSCT.

Defibrotide plus best standard of care compared with best standard of care alone for the prevention of sinusoidal obstruction syndrome (HARMONY): a randomised, multicentre, phase 3 trial.

BACKGROUND: Sinusoidal obstruction syndrome, also known as veno-occlusive disease, is a potentially life-threatening complication of haematopoietic stem-cell transplantation (HSCT). We aimed to compare defibrotide prophylaxis plus best supportive care versus best supportive care alone for sinusoidal obstruction syndrome prevention after HSCT. METHODS: This open-label, randomised, multicentre, phase 3 trial was done in 104 centres in 14 countries. Patients who were at least 1 month old, were scheduled to receive allogeneic HSCT (adult [aged >16 years] or paediatric [aged >1 month to ≤16 years] patients) or autologous HSCT (paediatric patients only), and were at high risk or very high risk of developing sinusoidal obstruction syndrome were eligible for inclusion. Patients were randomly assigned (1:1) by an interactive web response system to receive intravenous defibrotide 25 mg/kg per day (four equal doses [6·25 mg/kg per dose]) and best supportive care (determined by individual institutional guidelines; defibrotide prophylaxis group) or best supportive care only (best supportive care group). Randomisation was stratified by sinusoidal obstruction syndrome risk, age, and country. The primary endpoint, sinusoidal obstruction syndrome-free survival at day 30 after HSCT, was assessed by an independent Endpoint Adjudication Committee in the intention-to-treat (ITT) population. Safety was assessed in all patients who received protocol treatment. The trial is registered with ClinicalTrials.gov, NCT02851407. FINDINGS: Between Jan 11, 2017, and Oct 20, 2020, 372 patients (172 [46%] women and 200 [54%] men; median age 14·0 years [IQR 4·0-41·0] were randomly assigned to the defibrotide prophylaxis group (n=190) or best supportive care group (n=182; ITT population). On the basis of recommendations from the Independent Data Monitoring Committee following completion of the planned interim analysis in the first 280 recruited patients on April 29, 2020, enrolment was prematurely stopped for presumed futility. At the final analysis, sinusoidal obstruction syndrome-free survival by day 30 after HSCT was 67% (95% CI 58-74) in the defibrotide prophylaxis group and 73% (62-80) in the best supportive care group (HR 1·27 [95% CI 0·84-1·93]; p=0·85). Treatment-emergent adverse events were similar between groups during the randomised prophylaxis phase; most treatment-emergent adverse events were related to the transplantation rather than to study drug. The most common grade 3 or 4 treatment-emergent adverse events were stomatitis (grade 3, 52 [29%] of 181 patients in the defibrotide prophylaxis group and 56 [32%] of 174 patients in the best supportive care group; grade 4, two [1%] in the defibrotide prophylaxis group and two [1%] in the best supportive care group) and febrile neutropaenia (grade 3, 51 [28%] in the defibrotide prophylaxis group and 52 [30%] in the best supportive care group; grade 4, no patients in the defibrotide prophylaxis group and three [2%] in the best supportive care group). Serious treatment-emergent adverse events occurred in 74 (41%) of 181 patients in the defibrotide prophylaxis group and 61 (35%) of 174 patients in the best supportive care group. In the rescue phase, when patients in both treatment groups received defibrotide as rescue treatment, fatal treatment-related adverse events occurred in one (4%) of 25 patients in the defibrotide prophylaxis group (intracranial haemorrhage) and one (3%) of 31 patients in the best supportive care group (sinusoidal obstruction syndrome). INTERPRETATION: Defibrotide did not show a benefit in the prophylaxis of sinusoidal obstruction syndrome. Additional studies of carefully selected patients at high risk of sinusoidal obstruction syndrome after HSCT are warranted. FUNDING: Jazz Pharmaceuticals.

Efficacy and Safety of Recombinant Thrombomodulin for the Prophylaxis of Veno-Occlusive Complication in Allogeneiccit Hematopoietic Stem Cell Transplantation: A Systematic Review and Meta-Analysis.

BACKGROUND: Hepatic veno-occlusive disease (VOD), also termed as sinusoidal obstruction syndrome (SOS), is a lethal complication after hematopoietic stem cell transplantation (HSCT). Various factors put patients undergoing allogeneic HSCT at an increased risk for VOD. Thrombomodulin (TM) is an important factor which has a wide range of effects, including anticoagulant, anti-inflammatory, angiogenic, and protective effect, on endothelial cells. It plays a role in preventing excessive coagulation and thrombosis by binding with thrombin and inhibiting the coagulation cascade. There are a limited number of options for the prevention of this fatal complication. Recombinant thrombomodulin (rTM), an endothelial anticoagulant co-factor, as prophylactic therapy might be able to prevent veno-occlusive complications after stem cell transplantation. METHODS: A literature search was performed on PubMed, Embase, and Web of Science. We used the following Mesh terms and Emtree terms, "Hepatic Veno-Occlusive Diseases" OR "Sinusoidal Obstruction" OR "Stem Cell Transplantations " AND "Thrombomodulin" from the inception of data up to April 1, 2021. The PICO (Patient/Population, Intervention, Comparison and Outcomes) framework was used for the literature search. RESULTS: For the VOD incidence after HSCTstem cell transplantation, the result was in favor of rTM with a risk ratio (RR) of 0.53 (I2 = 0%, 95% confidence interval [CI] = 0.32-0.89). The incidence of transplant-associated thrombotic microangiopathy (TA-TMA) after HSCT was reduced in rTM group. The RR for incidence of TA-TMA was 0.48 (I2 = 62%, 95% CI = 0.20-1.17) favoring rTM. The RR for incidence of graft-versus-host disease (GvHD) was also lower in rTM group, 0.48 (I2 = 64%, 95% CI = 0.32-0.72). CONCLUSION: In our meta-analysis, we evaluate the efficacy and safety of rTM in the prevention of SOS after HSCT. According to our results, rTM use led to a significant reduction in SOS episodes, TA-TMA, and GvHD after HSCT.

A Systematic Review and Meta-Analysis of Studies of Defibrotide Prophylaxis for Veno-Occlusive Disease/Sinusoidal Obstruction Syndrome.

BACKGROUND AND OBJECTIVES: Defibrotide is approved to treat severe veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) after haematopoietic cell transplantation in patients aged > 1 month in the European Union and for VOD/SOS with renal/pulmonary dysfunction post-haematopoietic cell transplantation in the United States. This meta-analysis estimated the incidence and risk of VOD/SOS after intravenous defibrotide prophylaxis using the published literature. METHODS: PubMed, Embase and Web of Science were searched through 30 November 2021 for defibrotide studies in VOD/SOS "prevention" or "prophylaxis," excluding phase I studies, case reports, studies with fewer than ten patients and reviews. RESULTS: The search identified 733 records; 24 met inclusion criteria, of which 20 (N = 3005) evaluated intravenous defibrotide for VOD/SOS prophylaxis. Overall VOD/SOS incidence with intravenous defibrotide was 5%, with incidences of 5% in adults and 8% in paediatric patients. In eight studies with data on intravenous defibrotide prophylaxis vs controls (e.g. heparin, no prophylaxis), VOD/SOS incidence in controls was 16%. The risk ratio for developing VOD/SOS with defibrotide prophylaxis vs controls was 0.30 (95% confidence interval 0.12-0.71; p = 0.006). CONCLUSIONS: This analysis suggests a low incidence of VOD/SOS following intravenous defibrotide prophylaxis, regardless of age group, and a lower relative risk for VOD/SOS with defibrotide prophylaxis vs controls in patient populations at high risk of VOD/SOS.

Low-dose unfractionated heparin prophylaxis is a safe strategy for the prevention of hepatic sinusoidal obstruction syndrome after myeloablative adult allogenic stem cell transplant.

Hepatic sinusoidal obstruction syndrome (SOS) is a serious complication after allogeneic stem cell transplantation (allo-HCT). However, there is no uniform consensus on the optimal strategy for SOS prevention. Ursodeoxycholic acid is the most used regimen, even though its administration is challenging in recipients unable to tolerate oral medication. Defibrotide was recently studied in a phase 3 trial, but enrollment was stopped early due to futility. Low-dose unfractionated heparin (UFH) is an alternative strategy. However, its efficacy is reputed but unproven increased risk of bleeding has not been fully established. We evaluated 514 adult allo-HCT recipients who received SOS prophylaxis with low-dose UFH. Bleeding complications occurred in 12 patients 2.3% of patients of which only 2 (0.4%) had significant grade 3 bleeding. Only 14 patients were diagnosed with hepatic SOS. Univariate analysis showed that day 100 SOS was higher in recipients of unmodified grafts when compared to CD34+ selected ex vivo T-cell depleted grafts (p ≤ 0.001), and patients with hepatitis B and/or C exposure pre-HCT (p = 0.028). Overall, UFH was well tolerated and associated with a low incidence of subsequent hepatic SOS. Low-dose UFH prophylaxis can be considered in select patients who cannot tolerate oral ursodiol.

Effectiveness of defibrotide in the prevention of hepatic venooclusive disease among adult patients receiving allogeneic hematopoietic cell transplantation: A retrospective single center experience.

Hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) is one of the most life-threatening early complications following hematopoietic cell transplantation (HCT). Due to the high mortality rate of severe VOD/SOS accompanied with multiorgan failure, there is a great interest in preventive strategies. The efficacy of defibrotide (DF) on the prevention of VOD/SOS has been clearly shown in high-risk pediatric patients, but evidence-based data on adults is scarce. In this report, we aimed to assess the impact of DF on the incidence of VOD/SOS in our center by posttransplant day 30 among patients who were treated with allogeneic HCT (allo-HCT). The study included a total of 56 patiens (28 males, 28 females). The median age of the study cohort was 43 (20-68). The daily dose of DF was 10 mg/kg and 25 mg/kg in 53 (94.6 %) and 3 (5.3 %) patients, respectively. Patients also recieved oral ursodeoxycolic acid (UDCA) 250 mg three-times daily started with conditioning until D + 90. Twenty-three (41.1 %) patients had at least one major EBMT-defined risk factor for development of VOD/SOS. One patient who belonged to a very high-risk group (with at least two major risk factors) developed very-severe VOD/SOS at posttransplant D + 20 and died as a result of multiorgan failure. The cumulative incidence of VOD/SOS at D + 30 was 1.9 %. Our findings indicate that 10 mg/kg daily intravenous DF combined with UDCA is quite effective in prevention of VOD/SOS in patients who underwent first allo-HSCT.

Low Incidence of hepatic sinusoidal obstruction syndrome/veno-occlusive disease in adults undergoing allogenic stem cell transplantation with prophylactic ursodiol and low-dose heparin.

Hepatic sinusoidal obstruction syndrome (SOS)/veno-occlusive disease (VOD) is a complication after allogenic hematopoietic stem-cell transplantation (allo-HSCT) with high mortality. The purpose of this study was to assess the incidence and outcome of SOS in patients after allo-HSCT with the impact of ursodeoxycholic acid (UDCA) and low-dose heparin as SOS prophylaxis. Out of 1016 patients, 23 developed SOS, with a cumulative incidence of 2.3% (95% CI 1.3-3.3) 6 months after HSCT. Approximately one quarter of these patients (26.1%) had late-onset SOS. A high proportion were very severe SOS cases (74%), and 83% of the patients were treated with defibrotide (DF). In multivariate analysis, advanced disease (p = 0.003), previous HSCT (p = 0.025) and graft versus host disease (GvHD) prophylaxis by post-transplant cyclophosphamide (PTCy) (p = 0.055) were associated with the development of SOS. The 1-year overall survival (OS) was significantly lower in the SOS group compared to patients without SOS (13% versus 70%, p = 0.0001). In conclusion, we found a low incidence of SOS in patients receiving low-dose heparin and UDCA prophylactically, but among SOS patients, a high mortality. Low-dose heparin and UDCA might be a prophylactic approach for SOS.

The Prophylaxis of Hepatic Veno-Occlusive Disease/Sinusoidal Obstruction Syndrome With Defibrotide After Hematopoietic Stem Cell Transplantation in Children: Single Center Experience.

Hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) is one of the most severe and life-threatening complications after hematopoietic stem cell transplantation (HSCT). Defibrotide (DF) is approved for adult and pediatric patients with VOD/SOS with renal or pulmonary dysfunction after HSCT in the United States, and for severe VOD/SOS post-HSCT in patients above 1 month of age in the European Union. Several studies have examined whether DF prophylaxis can reduce the incidence of VOD/SOS in high-risk patients. A total of 334 pediatric allogeneic HSCT were included in this study. All patients received DF at the dose of 25 mg/kg/d, from the first day of the conditioning regimen to the 30th day after transplantation for VOD/SOS prophylaxis. Seventeen patients (5.08%) developed VOD/SOS; 4 of these had moderate, while 13 had mild VOD/SOS. None of the patients were developed severe or very severe VOD/SOS. In conclusion, we showed that prophylactic intervention with DF lowered the incidence of VOD/SOS in high-risk pediatric patients.

The importance of endothelial protection: the emerging role of defibrotide in reversing endothelial injury and its sequelae.

Hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS), a potentially life-threatening complication of hematopoietic cell transplantation (HCT), results from prolonged sinusoidal endothelial cell activation and profound endothelial cell damage, with sequelae. Defibrotide, the only drug approved in the United States and Europe for treating VOD/SOS post-HCT, has European Commission orphan drug designation for preventing graft-versus-host disease (GvHD), associated with endothelial dysfunction. This endothelial cell protector and stabilizing agent restores thrombo-fibrinolytic balance and preserves endothelial homeostasis through antithrombotic, fibrinolytic, anti-inflammatory, anti-oxidative, and anti-adhesive activity. Defibrotide also preserves endothelial cell structure by inhibiting heparanase activity. Evidence suggests that downregulating p38 mitogen-activated protein kinase (MAPK) and histone deacetylases (HDACs) is key to defibrotide's endothelial protective effects; phosphatidylinositol 3-kinase/Akt (PI3K/AKT) potentially links defibrotide interaction with the endothelial cell membrane and downstream effects. Despite defibrotide's being most extensively studied in VOD/SOS, emerging preclinical and clinical data support defibrotide for treating or preventing other conditions driven by endothelial cell activation, dysfunction, and/or damage, such as GvHD, transplant-associated thrombotic microangiopathy, or chimeric antigen receptor T-cell (CAR-T) therapy-associated neurotoxicity, underpinned by cytokine release syndrome and endotheliitis. Further preclinical and clinical studies will explore defibrotide's potential utility in a broader range of disorders resulting from endothelial cell activation and dysfunction.

Role of glutathione S-transferase P1 polymorphism in early transplant complications in patients undergoing allogeneic stem cell transplantation.

INTRODUCTION: Complications in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) cause serious morbidity and mortality. Predicting patients at risk in advance and changing the symptomatic care and/or preparation regimen according to this risk assessment have been emphasized recently. Several single-nucleotide polymorphisms have been studied, and some were found to be responsible for early complications. Glutathione S-transferase P1 (GSTP1) is an enzyme involved in the detoxification process that reduces oxidative stress by reducing the number of free oxygen radicals. AIM: This study aimed to investigate the relationship between GSTP1 polymorphism and early complications of allo-HSCT, iron parameters, overall survival (OS), and transplantation-related mortality (TRM). MATERIALS AND METHODS: A total of 50 patients diagnosed with acute myeloid leukemia (n = 23) or acute lymphoblastic leukemia (n = 27) who underwent allo-HSCT between May 2008 and February 2011 at Gazi University Faculty of Medicine, Stem Cell Transplantation Unit, were included. RESULTS: Of the 50 patients, 24 (48%) were women and 26 (52%) were men. The median age of the patients was 26 (16-74) years. GSTP1 polymorphism was detected in 23 (46%) patients, and 27 (54%) had no polymorphism (wild type). The two groups were compared in terms of early toxicity after transplantation, according to the preparation regimen. The group with GSTP1 polymorphism was found to have a high transferrin saturation index (P < 0.05). Patients with no GSTP1 polymorphism showed a high grade III-IV anemia ratio (P < 0.05). The presence of sinusoidal obstruction syndrome and graft-versus-host disease was similar in both groups (P > 0.05). OS and TRM were higher in the GSTP1 polymorphism group, but no statistical difference was found between the two groups (P > 0.05). CONCLUSIONS: TSI was higher in the GSTP1 polymorphism group. GSTP1 polymorphism had no effect on early transplantation complications. Although the OS and TRM ratios were higher in the GSTP1 polymorphism group, no statistically significant difference was found between the groups. Further studies with larger sample size are needed.

Hepatic sinusoidal obstruction syndrome and short-term application of 6-thioguanine in pediatric acute lymphoblastic leukemia.

Long-term treatment with 6-thioguanine (6-TG) for pediatric acute lymphoblastic leukemia (ALL) is associated with high rates of hepatic sinusoidal obstruction syndrome (SOS). Nevertheless, current treatment continues to use short-term applications of 6-TG with only sparse information on toxicity. 6-TG is metabolized by thiopurine methyltransferase (TPMT) which underlies clinically relevant genetic polymorphism. We analyzed the association between hepatic SOS reported as a serious adverse event (SAE) and short-term 6-TG application in 3983 pediatric ALL patients treated on trial AIEOP-BFM ALL 2000 (derivation cohort) and defined the role of TPMT genotype in this relationship. We identified 17 patients (0.43%) with hepatic SOS, 13 of which with short-term exposure to 6-TG (P < 0.0001). Eight of the 13 patients were heterozygous for low-activity TPMT variants, resulting in a 22.4-fold (95% confidence interval 7.1-70.7; P ≤ 0.0001) increased risk of hepatic SOS for heterozygotes in comparison to TPMT wild-type patients. Results were supported by independent replication analysis. All patients with hepatic SOS after short-term 6-TG recovered and did not demonstrate residual symptoms. Thus, hepatic SOS is associated with short-term exposure to 6-TG during treatment of pediatric ALL and SOS risk is increased for patients with low-activity TPMT genotypes.

Incidence and risk factors of hepatic veno-occlusive disease/sinusoidal obstruction syndrome after allogeneic hematopoietic cell transplantation in adults with prophylactic ursodiol and intravenous heparin or prostaglandin E1.

We attempted to identify the incidence and survival outcome of hepatic sinusoidal obstruction syndrome/veno-occlusive disease (VOD/SOS) after hematopoietic cell transplantation (HCT) under strategy of prophylactic ursodiol and intravenous heparin or prostaglandin E1 (PGE1). From 2009 to 2018, 2572 consecutive allogeneic-HCT cases were reviewed. We used oral ursodiol for all transplants, and most were administered low-dose heparin, while PGE1 in selected cases with low platelet count at the time of preconditioning. Diagnosis and severity grades were reassessed by revised EBMT criteria. The overall incidence of hepatic VOD/SOS was 3.4% (Mild 0.9%, Moderate 0.6%, Severe 0.7%, Very severe 1.2%) after allogeneic-HCT under strategy of intravenous prophylaxis. The 1-year overall survival of VOD/SOS was 41.4% which was divided into 73.9% for mild, 66.7% for moderate, 38.9% for severe, and 6.5% for very severe grade. Very high disease risk index, male gender, donor other than matched sibling donor, and busulfex > 9 mg/kg were affecting factors for development of VOD/SOS. For severe to very severe VOD/SOS, history of pre-HCT liver dysfunction was an additionally affecting factor. Allogeneic-HCT using ursodiol and intravenous prophylaxis was considered safe without significant bleeding complications and should be evaluated in future clinical trials. For those with high-risk of VOD/SOS, early intervention and management is important.

Efficacy of low dose and short duration defibrotide prophylaxis for hepatic veno-occlusive disease after autologous haematopoietic stem cell transplantation.

Hepatic veno-occlusive disease (VOD) is a serious systemic endothelial complication after stem cell transplantation. Defibrotide is under investigation as a prophylactic agent for VOD; however, high costs limit its utility. We evaluated the prophylactic efficacy of a low-dose defibrotide regimen for VOD. We retrospectively enrolled 147 paediatric patients who underwent autologous haematopoietic stem cell transplantation (HSCT; 69 with defibrotide prophylaxis and 78 historical controls) at the Yonsei Cancer Center in Seoul, Korea, between March 2013 and Feb 2020. Low-dose defibrotide (12.5 mg/kg/day) was administered from D-3 to D+10 after HSCT. The most common diagnosis in the cohort was brain tumour (N = 86). VOD developed in 10 (12.8%) and 3 (4.3%) patients in the control and prophylaxis groups, respectively (P = 0.071). In the second HSCT group, VOD incidence was significantly lower in the prophylaxis group [2.9% (1/35)] than in the control group (28.6%, 6/21, P = 0.005). VOD severity was significantly higher in the control group than in the prophylaxis group (P = 0.006). Three VOD-related mortalities occurred in the control group, whereas no VOD-related mortality occurred in the prophylaxis group. In conclusion, low-dose defibrotide prophylaxis is a promising and economical strategy for preventing VOD, especially in second-round HSCT.

Prevention, recognition, and management of adverse events associated with gemtuzumab ozogamicin use in acute myeloid leukemia.

Gemtuzumab ozogamicin (GO), a humanized anti-CD33 monoclonal antibody conjugated to the cytotoxic antibiotic agent calicheamicin, is approved for the treatment of newly-diagnosed CD33 + AML in adults and children ≥ 1 month old, and relapsed or refractory CD33 + AML in adults and children ≥ 2 years old. GO treatment has been associated with an increased risk of hepatotoxicity and hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS), especially following hematopoietic stem cell transplantation. Other non-specific serious adverse events (SAEs) associated with GO treatment are myelosuppression, bleeding/thrombocytopenia, infusion-related reaction, and tumor lysis syndrome. This report summarizes an expert panel of physicians' recommendations for the evaluation and management of SAEs following GO, emphasizing the prevention and management of VOD/SOS.

Platelets prevent the development of monocrotaline-induced liver injury in mice.

Destruction of liver sinusoidal endothelial cells (LSECs) is an initial event in sinusoidal obstruction syndrome (SOS) that leads to accumulation of platelets in the liver. Herein, we explored the role of platelets during progression of experimental SOS induced by monocrotaline (MCT) in mice. Depletion of platelets using an anti-CD41 antibody or anti-thrombocyte serum exacerbated MCT-induced liver injury in C57BL/6 mice, as indicated by an increase in the alanine transaminase (ALT) level, which was associated with hemorrhagic necrosis. Thrombocytosis induced by thrombopoietin (TPO) or the TPO receptor agonist romiplostim (ROM) attenuated MCT-induced liver injury, as evidenced by lower levels of ALT and mRNA encoding matrix metalloproteinase (MMP) 9, and higher levels of mRNA encoding vascular endothelial growth factor receptor (VEGFR) 2 and VEGFR3. The level of activated hepatic platelets was higher in TPO- and ROM-treated mice than in saline-treated mice. Co-culture with a high number of platelets increased the viability of LSECs and their mRNA levels of CD31, VEGFR2, and VEGFR3, and decreased their mRNA level of MMP9. The level of VEGF-A was increased in the culture medium of LSECs co-cultured with platelets. These results indicate that platelets attenuate MCT-induced liver injury by minimizing damage to LSECs.