Hepatic Microcirculation Research Articles

Hepatic arterial flow becomes the primary supply of sinusoids following partial portal vein ligation in rats

Partial portal vein ligation (PPVL) is a commonly used procedure to induce prehepatic portal hypertension in animal models. The aim of this study was to test the hypothesis that the hepatic arterial flow becomes the primary source feeding the sinusoids in the liver after PPVL. Sprague-Dawley rats underwent either sham operation or partial portal vein ligation (PPVL). The number of vessels in the liver at 2 weeks postoperatively was determined by factor VIII immunolocalization and the gene expression of angiogenic factors was assessed by RT-PCR. The total hepatic arterial supply to the liver was measured using the fluorescent microsphere injection technique. To further test the hypothesis, two additional groups of rats underwent hepatic artery ligation (HAL) or PPVL plus HAL (PPHAL). The integrity of hepatic microcirculation was then evaluated in all four groups by intravital microscopy. At 2 weeks after operation, the number of vessels detected by factor VIII staining was significantly higher in PPVL compared to sham. Densitometric analysis of RT-PCR bands revealed a significant increase of vascular endothelial growth factor gene expression in PPVL compared to sham. Arterial flow to the liver measured by fluorescent microspheres was increased by 190% in PPVL compared to sham. When all four groups were compared, no prominent histological abnormality was observed in sham, HAL, and PPVL groups; however, PPHAL livers showed focal necrosis and inflammatory cell infiltration around the portal triads. Additionally, only the PPHAL livers showed a decreased sinusoidal diameter and significantly lower perfusion index (PPHAL 42.9+/-6.1; sham 85.7+/-7.0, PPVL 80.2+/-6.5, HAL 70.9+/-4.5). These results suggest that the hepatic artery flow becomes the primary source for the blood supply of sinusoids and the compensatory change in the hepatic arterial system plays a critical role in maintaining microcirculatory perfusion following the restriction of the portal vein flow by PPVL.

Nitric oxide and liver microcirculation during autoregulation and haemorrhagic shock in rabbit model

Direct evidence of nitric oxide (NO) involvement in the regulation of hepatic microcirculation is not yet available under physiological conditions nor in haemorrhagic shock. A laser Doppler flowmetry was used to measure liver perfusion index and a specific NO-sensitive electrode was inserted into liver parenchyma of anaesthetized rabbits. Hepatic autoregulation during moderate hypovolaemia {mean arterial pressure at 50 mm Hg without liver perfusion alteration; blood withdrawal 17.7 (4.2) ml [mean (SD)]} or haemorrhagic shock [mean arterial pressure at 20 mm Hg associated with liver perfusion impairment and lactic acidosis; blood withdrawal 56.0 (6.8) ml] were investigated over 60 min and were followed by a rapid infusion of the shed blood. Involvement of NO synthases was evaluated using a non-specific inhibitor, NAPNA (Nomega-nitro-L-arginine P-nitro-anilide). In the autoregulation group, a decrease [30.0 (4.0) mm Hg] of mean arterial pressure did not alter liver perfusion index, whereas the liver NO concentration increased and reached a plateau [125 (10)%; compared with baseline; P<0.05]. This NO concentration was reduced to zero by the administration of NO synthase inhibitor. Haemorrhagic shock led to a rapid decrease in liver perfusion index [60 (7)%; compared with baseline; P<0.05] before an immediate and continuous increase in NO concentration [250 (50)%; compared with baseline; P<0.05]. Infusion of NO inhibitor before haemorrhagic shock reduced the NO concentration to zero and hepatic perfusion by 60 (8)% (P<0.05) of the baseline. Mean arterial pressure increased simultaneously. In these animals, during haemorrhage, a continuous increase in NO concentration still occurred and liver perfusion slightly increased. In all groups but NAPNA+haemorrhagic shock, blood replacement induced recovery of baseline values. NO plays a physiological role in the liver microcirculation during autoregulation. Its production is enzyme-dependent. Conversely, haemorrhagic shock induces a rapid increase in hepatic NO that is at least partially enzyme-independent.

Transplantation of Preconditioned Intestinal Grafts is Associated With Lower Inflammatory Activation and Remote Organ Injury in Rats

Reperfused grafts—particularly the intestine—release free radicals and cytokines into the systemic circulation. The type of discharge, which is greatly dependent on the local injury, may also induce inflammatory activation in distant organs and leading to multiple system and organ failure. It has been suggested that intestinal grafts from tacrolimus (TRL)-pretreated donors show improved morphology and microcirculation. We studied whether transplantation of intestines from TRL-pretreated donors influenced inflammatory response and remote organ injury posttransplantation. Donor Sprague Dawley rats received TRL or saline (controls) intravenously at 6 hours prior to graft harvest. The intestinal grafts were preserved in saline for 3 hours before transplantation. At 6 and 12 hours postreperfusion hepatic and renal cortical microcirculation were assessed using laser-Doppler flowmetry ( n = 8–12 per group). Blood pressure was measured; liver, kidney, and serum samples were obtained. We analyzed hepatic and renal ICAM-1 expression and caspase-3-like activity as well as plasma content of tumor necrosis factor-alpha and interleukin-6. Pretreated graft recipients had higher mean arterial pressure (82 ± 10 vs 51 ± 17 mm Hg, P < .05) and renal perfusion at 6 hours whereas liver perfusion was similar at both 6 and 12 hours. Liver and renal functions were also superior among recipients of pretreated grafts. Both caspase-3-like activity and ICAM-1 expression in liver and kidney were lower in pretreated graft recipients. Plasma IL-6 levels were lower in animals receiving pretreated grafts. Transplantation of intestines from TRL-pretreated donors was followed by a lower systemic inflammatory response, improved organ function and decreased remote injury early posttransplantation compared with animals receiving grafts from untreated donors.

Effect of glutamine pretreatment on rat liver microcirculation during ischemia-reperfusion

Background: Ischemia-reperfusion (I-R) injury plays an important role during liver resection or liver transplantation. Ischemic damage is inevitable in a number of surgical procedures performed on the liver. The clinical outcome as well as the survival of the functioning grafts and the resected liver largely depends on the extent of inflicted damage. The glutamine is essential in the glutathion (GSH) synthesis as it is well-known. The I-R leads to the production of toxic oxygen-derived free radicals which influence the GSH pools. This study investigated the effect of glutamine pretreatment on hepatic microcirculation (HM), assuming the glutamine protective effect against the free radicals.

ACTIVATED PROTEIN C REDUCES HEPATIC ET-1 TRANSCRIPT LEVELS AFTER TRAUMA AND SEPSIS

Introduction: Activated protein C (aPC) confers survival benefit in patients with sepsis; yet its protective mechanisms remain unclear. Recently, we found that aPC ameliorates ET-1 induced alterations in the hepatic microcirculation after femur fracture (FFx) and cecal ligation and puncture (CLP). Here, we hypothesize that the protective effects of aPC are mediated by a reduction in the vasoconstrictor ET-1 and its receptor, ETA. Methods: Male Sprague Dawley rats underwent control, sham, FFx, CLP, or FFx followed 24 hours by CLP. Subsequently, animals received either aPC (1 mg/kg) or saline intravenously, twice daily for four days. Twenty four hours after the final aPC or saline treatment, liver tissue was harvested for RT-PCR. Results: CLP and FFx + CLP resulted in a significant upregulation in ET-1 and ETA receptor transcripts when compared to control and sham. Treatment with aPC resulted in a reduction in ET-1 and ETA receptor mRNA levels after CLP and FFx+CLP (see Figure); no effect was seen in control, sham, and FFx animals.FigureConclusion: Treatment with aPC reduced the vasoconstrictor ET-1 and ETA receptor mRNA levels in CLP and FFx+CLP animals, which plays an important role in the protective effects of aPC on the observed hepatic microcirculation in response to ET-1. Figure: Saline treated vs aPC treated RT-PCR bands for ET-1 and ETA receptor. 1 = CLP and 2 = FFx + CLP

Protective effect of prostaglandine E2 and endothelin-1 receptor antagonist in hepatic microcirculation and oxygenation during acute increased intra-abdominal pressure: experimental study

de Riva, N.; Sanchez-Etayo, G.; Fernandez, B.; Tercero, J.; Garduño, A.; Hurtado, P.; Taura, P. Author Information

Warm Ischemia-induced Alterations in Oxidative and Inflammatory Proteins in Hepatic Kupffer Cells in Rats

The aim of the study was to investigate the impact of ischemia/reperfusion injury on the proteome of Kupffer cells. Lean Zucker rats (n = 6 each group) were randomized to 75 min of warm ischemia or sham operation. After reperfusion for 8 h, Kupffer cells were isolated by enzymatic perfusion and density gradient centrifugation. Proteins were tryptically digested into peptides and differentially labeled with iTRAQ (isobaric tags for relative and absolute quantitation) reagent. After fractionation by cation exchange chromatography, peptides were identified by mass spectrometry (ESI-LC-MS/MS). Spectra were interrogated against the Swiss-Prot database and quantified using ProteinProspector. The results for heat shock protein 70 and myeloperoxidase were validated by ELISA. Quantitative information for more than 1559 proteins was obtained. In the ischemia group proteins involved in inflammation were significantly up-regulated. The ratio for calgranulin B in the ischemia/sham group was 1.81 +/- 0.97 (p < 0.0001), for complement C3 the ratio was 1.81 +/- 0.49 (p < 0.0001), and for myeloperoxidase the ratio was 1.30 +/- 0.32. Myeloperoxidase was only recently documented in Kupffer cells. The antioxidative proteins Cu,Zn-superoxide dismutase (1.34 +/- 0.19; p < 0.001) and catalase (1.23 +/- 0.43; p < 0.001) were also elevated. In conclusion, ischemia/reperfusion injury induces alterations in the Kupffer cell proteome. Isotope ratio mass spectrometry is a powerful tool to investigate these reactions. The ability to simultaneously monitor several pathways involved in reperfusion stress may result in important mechanistic insight and possibly new treatment options.

200 Derangement of the hepatic microcirculation during the development of liver cirrhosis in the bile duct ligated (BDL) rat

200 Derangement of the hepatic microcirculation during the development of liver cirrhosis in the bile duct ligated (BDL) rat

Advantage of Ischemic Preconditioning for Hepatic Resection in Pigs

Ischemic preconditioning (IP) and intermittent inflow occlusion (IO) have provided beneficial outcomes in hepatic resection. However, comparison of these two procedures against warm hepatic ischemia-reperfusion injury has not been studied enough. Pigs that had undergone 65% hepatectomy were subjected to Control (120 min continuous ischemia, n = 6), IP (10 min ischemia and 10 min reperfusion, followed by 120 min continuous ischemia, n = 6), and IO (120 min ischemia in the form of eight successive periods of 15 min ischemia and 5 min reperfusion, n = 6). We evaluated hepatocyte injury by aspartate aminotransferase, lactate dehydrogenase and hepaplastin test, hepatic microcirculation by hepatic tissue blood flow (HTBF) and endothelin (ET)-1, inflammatory response by tumor necrosis factor-alpha (TNF-alpha), and histopathology after reperfusion. IP prevented hepatocyte injury, HTBF disturbance, and hepatocyte necrosis in histopathology as well as IO. These two groups showed significantly better outcomes than Control. IP produced significantly less ET-1 and TNF-alpha than IO. IP ameliorated hepatic warm ischemia-reperfusion injury. Furthermore, IP gained more advantages in preventing chemokine production such as ET-1 and inflammatory response over IO. IP could take the place of IO for hepatectomy.

The Secretory Leukocyte Protease Inhibitor Is a Type 1 Insulin-Like Growth Factor Receptor–Regulated Protein that Protects against Liver Metastasis by Attenuating the Host Proinflammatory Response

The secretory leukocyte protease inhibitor (SLPI) can attenuate the host proinflammatory response by blocking nuclear factor kappaB (NF-kappaB)-mediated tumor necrosis factor alpha (TNF-alpha) production in macrophages. We have previously shown that highly metastatic human and mouse carcinoma cells, on their entry into the hepatic microcirculation, trigger a rapid host proinflammatory response by inducing TNF-alpha production in resident Kupffer cells. Using GeneChip microarray analysis, we found that in mouse Lewis lung carcinoma subclones, SLPI expression was inversely correlated with tumor cell ability to induce a proinflammatory response and metastasize to the liver and with type 1 insulin-like growth factor receptor expression levels. To establish a causal relationship between SLPI expression and the metastatic phenotype, we generated, by transfection, multiple clones of the highly metastatic subline (H-59) that overexpress SLPI. We show here that the ability of these cells to elicit a host proinflammatory response in the liver was markedly decreased, as evidenced by reduced TNF-alpha production and vascular E-selectin expression, relative to controls. Moreover, these cells formed significantly fewer hepatic metastases (up to 80% reduction) as compared with mock-transfected controls. Our findings show that SLPI can decrease the liver-metastasizing potential of carcinoma cells and that this protective effect correlates with a decrease in the production of hepatic TNF-alpha and E-selectin. They suggest that factors that attenuate the host proinflammatory response may have a therapeutic potential in the prevention of liver metastasis.

Retracted: Fat-Derived Hormone Adiponectin Combined with FTY720 Significantly Improves Small-for-Size Fatty Liver Graft Survival

Owing to the discrepancy between organ donation and the demand for liver transplantation, expanding the liver donor pool is of vital importance. However, marginal liver grafts, such as small-for-size and/or fatty grafts, were associated with primary graft nonfunction or poor function. Therefore, novel combination therapies to rescue small-for-size fatty liver grafts should be investigated. In this study, we applied a combination therapy using a fat-derived hormone adiponectin (anti-steatosis) plus immunomodulator FTY720 (anti-inflammatory) in a rat liver transplantation model using small-for-size fatty liver grafts, and investigated the underlying protective mechanism such as anti-steatosis, intra-graft energy metabolism, hepatic microcirculatory changes, cell signaling cascades for survival, apoptosis and inflammation. The current study demonstrated that even a single treatment of adiponectin or FTY720 improved the 7-day graft survival from 0% to 62.5% (p = 0.001). The combination therapy significantly increased the 7-day graft survival rate to 100% by remarkable attenuation of graft steatosis and acute phase inflammatory response, significant activation of cell survival Akt pathway and maintenance of intra-graft adenosine triphosphate metabolism and improvement of hepatic microcirculation. In conclusion, the fat-derived hormone adiponectin combined with FTY720 might be a novel combination drug therapy for prevention of small-for-size fatty liver graft injury.

Hepatic Stellate Cells in Biopsies From Liver Allografts With Acute Rejection

Backround Hepatic stellate cells (HSCs) are nonparenchymal elements that play a major role in fibrogenesis due to various pathologies. HSCs are easily activated by certain injuries, which produce contraction and relaxation of HSCs, resulting in hepatic microcirculatory disturbances. The present study sought to analyze the expression of alpha-smooth muscle actin (alpha-SMA) positive HSCs in liver allografts during acute rejection episodes (ARE), determining whether it was related to the pathogenesis of this immune response. Materials and Methods Using immunohistochemistry and a semiquantitative scoring system, the expression of alpha-SMA in HSCs was analyzed in liver allografts with ARE (group 1, n = 64) or without ARE (group 2, n = 20). Normal liver tissue from transplant donors (group 3, n = 53) served as the control materials. Results Significantly more alpha-SMA positive HSCs were found in group 2 than in the other two groups ( P < .05). The minimal difference observed between groups 1 and 3 was not statistically significant. As well, no statistical association was found between expression of alpha-SMA and the clinical parameters of age, gender, etiology of liver failure, donor type (partial or whole), posttransplantation period, and liver function tests. Conclusions While these results represent preliminary findings, it may be possible that HSC expression is a protective mechanism during ARE in hepatic allograft patients. If this is true, enhanced expression of this protein may mitigate ARE in liver allograft patients.

Comprehensive Analysis of the Regenerating Mouse Liver: An In Vivo Fluorescence Microscopic and Immunohistological Study

Regeneration of tissue is a fundamental parameter of the liver's response to injury and is essential for post-operative recovery from hepatic resection. An adequate microvascular supply of both remnant tissue and newly formed cell clusters is necessary for the accurate restoration of the organ. However, a comprehensive analysis of hepatic architecture and microcirculation during liver regeneration is missing. Using intravital high resolution multifluorescence microscopy and histological techniques we analyzed the regenerating liver of mice at days 3, 5, and 8 after 68% hepatectomy. Within the 8-day course of regeneration, liver weight restored to approximately 90% of its original mass. During the 8-day period of observation density of hepatocytes and Ito cells was constantly found reduced from 4,200 and 800 cells/mm(2) in non-hepatectomized control livers to approximately 2,500 and approximately 500 cells/mm(2). A transient decline of sinusoidal density was partly compensated by recruiting all sinusoids for perfusion with a final perfusion index of 79, 89, and 98% at days 3, 5, and 8 after resection. Increase of sinusoidal diameters preserved functional vessel area after resection, guaranteeing an adequate tissue oxygenation, as verified by low parenchymal NADH autofluorescence. The number of PCNA expressing hepatocytes rose 11-, 4-, and 2-fold at days 3, 5, and 8 after resection, followed by a maximum proliferation of sinusoidal lining cells at day 5. Cell apoptosis slightly increased, most probably in response to the restoration and to eliminate redundant cells. Liver regeneration was not associated with enhanced leukocyte-endothelial cell interaction, disproving inflammation as a relevant trigger for the regeneration. The present data contribute to a better understanding of the complex vascular and cellular mechanisms during liver regeneration to develop strategies fighting against impeded liver growth.

Effects of the platelet-activating factor receptor antagonist WEB 2086 on hepatic microcirculation following hemorrhagic hypotension

BACKGROUND: Perfusion failure in the microcirculation, known as "no-reflow phenomenon", due to ischemia-/reperfusion injury might cause severe problems following resuscitation from shock or sepsis. This situation often develops within a few days after the initial injury. The implication of the Platelet Activating Factor (PAF) in the development of microcirculatory disturbances after various conditions of shock, sepsis and ischemia-reperfusion incidents was shown in a variety of studies. We evaluated the role of PAF in the hepatic microcirculation using an intra-vital microscopy (IVM) rat-model of hemorrhagic shock. METHODS: The animals were randomly assigned to shock groups with microscopy after two or five days or corresponding control-groups without shock. After pressure controlled hemorrhagic hypotension of 90 minutes, shock rats were treated with WEB 2086 (1 mg/kg) or saline in a randomized and blinded manner followed by three hours of resuscitation with Ringers. Intravital microscopy of the liver was performed two or five days after shock. RESULTS: Two days after shock the sinusoidal leukocyte flow was significantly improved by WEB 2086. However, after five days no difference was seen between all groups. After two days, but not after five days, the perfusion-index, indicating the proportion of perfused sinusoids to all investigated sinusoids, was significantly increased by WEB 2086 in comparison to the saline treated animals. Hemorrhagic shock induced a long-lasting narrowing of the sinusoids up to five days. The mean sinusoidal diameters were significantly increased by WEB 2086 compared with the Shock group at day two and five. CONCLUSIONS: The results suggest a positive effect of WEB 2086 on the shock-induced microcirculatory dysfunction.

Roles of anandamide in the hepatic microcirculation in cirrhotic rats

Cannabinoids have been reported to participate in the pathogenesis of peripheral vasodilatation in cirrhosis. However, their roles in increased intrahepatic resistance (IHR) in cirrhotic livers are unknown. We aimed to investigate the effects of cannabinoids in the hepatic microcirculation of cirrhotic rats produced by bile duct ligation. In isolated liver perfusion, portal perfusion pressure (PPP) and the production of eicosanoids in the perfusate were measured. In addition, various hepatic protein levels [cyclooxygenase (COX) isoform and 5-lipoxygenase (5-LOX)] were also determined. Finally, concentration-response curves for PPP and the corresponding production of eicosanoids in response to anandamide (1.44 x 10(-10)-1.44 x 10(-3) M) after indomethacin (COX inhibitor), piriprost (5-LOX inhibitor), or furegrelate (thromboxane A(2) synthase inhibitor) preincubation were obtained. The study showed that cirrhotic livers had significantly higher levels of PPP, COX-2 and 5-LOX protein expression, and production of thromboxane B(2) (TXB(2)) and cysteinyl leukotrienes (Cys-LTs) than normal livers. Anandamide induced a dose-dependent increase in PPP in both normal and cirrhotic livers. The anandamide-induced increase in PPP was found concomitantly with a significant increase in TXB(2) and Cys-LT production in the perfusate. In response to anandamide administration, cirrhotic livers exhibited a significantly greater increase in IHR and production of TXB(2) and Cys-LTs than normal livers. Indomethacin and furegrelate, but not piriprost, significantly ameliorated the anandamide-induced increase in IHR in cirrhotic livers. In conclusion, anandamide plays, in part, an important role in increased IHR of cirrhotic livers. The anandamide-induced increase in IHR in cirrhotic livers may be mediated by increased COX-derived eicosanoid (mainly thromboxane A(2)) production.

Activated protein C protects hepatic microcirculation and preserves hepatocellular function after trauma and sepsis

Activated protein C protects hepatic microcirculation and preserves hepatocellular function after trauma and sepsis

Hepatic microcirculatory failure

Liver ischemia has been considered a frequent problem in medical practice, and can be associated to a number of surgical and clinical situations, such as massive hepatic resections, sepsis, liver trauma, circulatory shock and liver transplantation. After restoring blood flow, the liver is further subjected to an additional injury more severe than that induced by ischemia. On account of the complexity of mechanisms related to pathophysiology of ischemia and reperfusion (I/R) injury, this review deals with I/R effects on sinusoidal microcirculation, especially when steatosis is present. Alterations in hepatic microcirculation are pointed as a main factor to explain lower tolerance of fatty liver to ischemia-reperfusion insult. The employment of therapeutic strategies that interfere directly with vasoactive mediators (nitric oxide and endothelins) acting on the sinusoidal perfusion seem to be determinant for the protection of the liver parenchyma against I/R. These approaches could be very suitable to take advantage of marginal specimens as fatty livers, in which the microcirculatory disarrangements hamper its employment in liver transplantation.

Heme oxygenase 1 expression in postischemic reperfusion liver damage: effect of L‐Arginine

Ischemia/reperfusion (I/R) injury is a multifactorial process that affects liver function after transplantation and resectional surgery. Alterations in hepatic microcirculation and decreased hepatic flow can cause local hypoxia and consequently liver damage, which is worsened by reperfusion. The aim of this study was to evaluate if treatment with L-arginine improved hepatic function in rats with I/R injury. Animals were treated with L-arginine, ischemized for 30 min, and reperfused for 3 h. Plasmatic levels of GOT, GPT, lipid hydroperoxides (LOOH), and total thiol groups (RSH) were evaluated. In addition, we analyzed hepatic LOOH and RSH levels, DNA fragmentation, heme oxygenase 1 (HO-1) expression, and histological modifications. Our results demonstrate a significant improvement in hepatic function of I/R rats compared to the control group. Treatment with L-arginine increased the expression of HO-1. These data suggest that L-arginine could be useful in preventing oxidative damage during hepatic surgery.

Adult liver transplantation using live ABO-incompatible grafts in western countries

In Western countries, the indication for liver transplantation using ABO-incompatible (ABO-I) donors remains controversial. The risks of ABO-I transplantation include antibody-mediated hyperacute rejection, a higher incidence of severe acute rejection, hepatic artery thrombosis, and biliary complications.1-3 Subsequently, the results of adult deceased donor liver transplantation using ABO-I grafts are poor, with an approximately 20% chance of 5-year graft survival.4 Histologically, the liver grafts are complicated by widespread hemorrhagic necrosis with intraorgan thrombosis and prominent arterial deposition of antibody and complement. Demetris et al.3 termed this syndrome “single-organ disseminated intravascular coagulation.” Prophylactic antilymphocyte globulin, plasmapheresis, splenectomy, soluble antigen, and ABO immunoadsorbents have been used with varying degrees of success but might be associated with a higher incidence of sepsis and do not improve the outcome for adult patients.5, 6 It has been concluded, therefore, that the use of ABO-I liver grafts is justified only in limited situations, such as in emergencies. ABO-I, ABO-incompatible; LDLT, living donor liver transplantation. It is another story, however, in Eastern countries, where the availability of deceased donor organs falls short of the population need and living donor liver transplantation (LDLT) is almost the only procedure that offers hope to patients with end-stage liver disease. All donors must be related to the patients; most of them are within three degrees of consanguinity or a spouse. If the patients have no ABO-identical or -compatible donors, ABO-I donors are the only available option. According to the Japanese Registry of Living Donor Liver Transplantation across ABO Blood Type Barrier, 97 ABO-I LDLTs were performed in Japan before March 2005; this corresponds to approximately 5% of the total adult (≥16 years of age) LDLTs performed. The 5-year survival rate of the patients was 38% before 2001 and improved to 63% among patients who underwent ABO-I after 2002. Some Japanese transplant surgeons7, 8 commented that the improvement was provided by innovative postoperative portal vein infusion therapy. The main purpose of this therapy is to control any local disseminated intravascular coagulation arising in ABO-I grafts. Three agents, methylprednisolone, prostaglandin E1, and gabexate mesylate, are infused continuously for 3 weeks after transplantation through a catheter placed in the portal vein during surgery. Prostaglandin E1 improves hepatic blood flow and microcirculation through its vasodilating effects and inhibits platelet/leukocyte adhesion. Gabexate mesylate is a serine protease inhibitor that inhibits thrombin, Xa, and platelet aggregation. These agents are logical choices for controlling local disseminated intravascular coagulation and immune responses. Systemic anti-rejection therapy basically follows the kidney protocol: pre- and postoperative plasmapheresis, splenectomy, and triple-immune prophylaxis, including steroids, tacrolimus, and antiproliferative agents. Recent advances in immunomodulatory therapy for ABO-I grafts include the use of anti-CD20 monoclonal antibody or soluble complement receptor9 as an alternative to splenectomy for B-cell depletion. More recently, the Kyoto group10 began infusing the two agents (methylprednisolone and prostaglandin E1) through a hepatic artery instead of the portal vein. They emphasized better graft survival with a reduced risk of portal vein thrombosis. The protocol described by Troisi et al.11 for an ABO-I barrier in this issue of Liver Transplantation is partly new but not entirely unexpected. Immunoadsorption with immobilized blood antigen A or B is used for ABO-I living donor kidney transplantation.12 The use of daclizumab instead of cyclophosphamide has been tried in ABO-I deceased donor liver transplantation.13 Of note is that this article11 is the first report from a Western country on ABO-I LDLT for an adult patient series. The report is very encouraging although the number is small and the follow-up period is short. We agree with the conclusions of the authors that the protocol deserves further application with immunologic studies. ABO-I liver grafting in adults may no longer be considered experimental but should be considered as a reasonable clinical option when no blood group–compatible liver is available for a critically ill patient. At the same time, however, liver transplantation using live ABO-I grafts should be a rare event. In LDLT, the physical and psychologic sacrifice by the donor is significant and is associated with high expectations of a good outcome for themselves and the recipient.14 The precise indication requires further debate in the Western countries where cadaveric organ is available, as the authors commented in the Discussion. The authors thank Dr. Hiroto Egawa (Kyoto University) for ABO-I LDLT data in Japan and Dr. Sumihito Tamura (University of Tokyo) for critical review of the article.

CD4+ T cells contribute to postischemic liver injury in mice by interacting with sinusoidal endothelium and platelets

The mechanisms by which T cells contribute to the hepatic inflammation during antigen-independent ischemia/reperfusion (I/R) are not fully understood. We analyzed the recruitment of T cells in the postischemic hepatic microcirculation in vivo and tested the hypothesis that T cells interact with platelets and activate sinusoidal endothelial cells, resulting in microvascular dysfunction followed by tissue injury. Using intravital videofluorescence microscopy, we show in mice that warm hepatic I/R (90/30-140 min) induces accumulation and transendothelial migration of CD4+, but not CD8+ T cells in sinusoids during early reperfusion. Simultaneous visualization of fluorescence-labeled CD4+ T cells and platelets showed that approximately 30% of all accumulated CD4+ T cells were colocalized with platelets, suggesting an interaction between both cell types. Although interactions of CD4+/CD40L-/- T cells with CD40L-/- platelets in wild-type mice were slightly reduced, they were almost absent if CD4+ T cells and platelets were from CD62P-/- mice. CD4 deficiency as well as CD40-CD40L and CD28-B7 disruption attenuated postischemic platelet adherence in the same manner as platelet inactivation with a glycoprotein IIb/IIIa antagonist and reduced neutrophil transmigration, sinusoidal perfusion failure, and transaminase activities. Treatment with an MHC class II antibody, however, did not affect I/R injury. In conclusion, we describe the type, kinetic, and microvascular localization of T cell recruitment in the postischemic liver. CD4+ T cells interact with platelets in postischemic sinusoids, and this interaction is mediated by platelet CD62P. CD4+ T cells activate endothelium, increase I/R-induced platelet adherence and neutrophil migration via CD40-CD40L and CD28-B7-dependent pathways, and aggravate microvascular/hepatocellular injury.