Effect of Age and Postoperative Time on Cytochrome P450 Enzyme Activity Following Liver Transplantation

This study evaluates the changes in cytochrome P450 (CYP) enzyme activity in orthotopic liver transplant (OLTx) patients in relation to recipient age and postoperative time. Thirty-eight stable OLTx patients, separated into younger and older age groups, and 21 healthy subjects were given a 5-drug cocktail including chlorzoxazone (CYP2E1), caffeine (CYP1A2), dapsone (CYP3A4), mephenytoin (CYP2C19), and debrisoquin (CYP2D6). The phenotypic indexes were determined for each associated enzyme. Compared to young healthy subjects, the CYP2E1 capacity was significantly increased in younger and older OLTx patients (P < .001), while the CYP2C19 capacity was decreased significantly in younger and older OLTx patients within 30 days postoperatively (P < .01). The CYP2D6 capacity was significantly lower after 30 days postoperatively in older OLTx patients (P < .05). The authors conclude that within 30 days postoperatively, CYP2E1 capacity was markedly elevated in OLTx patients, while 2C19 function was significantly reduced. CYP2D6 capacity was impaired after 30 days postoperatively. Younger and older OLTx patients experienced similar changes in major CYP450 enzyme capacity following liver transplantation.

Predicting the discharge status after liver transplantation at a single center: a new approach for a new era

The aim of this study was to develop a tool for preoperatively predicting the need of a patient to attend an extended care facility after orthotopic liver transplantation (OLT). A multidisciplinary group, which included 2 transplant surgeons, 2 transplant nurses, 1 nurse manager, 2 physical therapists, 1 case manager, 1 home health care professional, 1 rehabilitation physician, and 1 statistician, met to identify preoperative factors relevant to discharge planning. The parameters that were examined as potential predictors of the discharge status were as follows: age, sex, language, Karnofsky score, OLT alone (versus a combined procedure), creatinine, bilirubin, international normalized ratio (INR), albumin, body mass index (BMI), Child-Turcotte-Pugh score, chemical Model for End-Stage Liver Disease score, renal dialysis, location before transplantation, comorbidities (encephalopathy, ascites, hydrothorax, and hepatopulmonary syndrome), diabetes mellitus (DM), cardiac ejection fraction and right ventricular systolic pressure, sex and availability of the primary caregiver, donor risk index, and donor characteristics. Between January 2004 and April 2010, 730 of 777 patients (94%) underwent only liver transplantation, and 47 patients (6%) underwent combined procedures. Five hundred nineteen patients (67%) were discharged home, 215 (28%) were discharged to a facility, and 43 (6%) died early after OLT. A multivariate logistic regression analysis identified the following parameters as significantly influencing the discharge status: a low Karnofsky score, an older age, female sex, an INR of 2.0, a creatinine level of 2.0 mg/dL, DM, a high bilirubin level, a low albumin level, a low or high BMI, and renal dialysis before OLT. The nomogram was prospectively validated with a population of 126 OLT recipients with a concordance index of 0.813. In conclusion, a new approach to improving the efficiency of hospital care is essential. We believe that this tool will aid in reducing lengths of stay and improving the experience of patients by facilitating early discharge planning.

Progressive primary sclerosing cholangitis requiring liver transplantation is associated with reduced need for colectomy in patients with ulcerative colitis

BACKGROUND & AIMS

We investigated the association between the severity of primary sclerosing cholangitis (PSC) and clinical outcomes of patients with ulcerative colitis (UC) on the basis of need for colectomy.

METHODS

We analyzed data from 167 patients with PSC and UC who were followed from 1985 to 2011. Patients with PSC and UC were divided into groups that received orthotopic liver transplantation (OLT) (n = 86) or did not (non-OLT, n = 81). Clinical and demographic variables were obtained, and patients were followed until they received OLT or the date of their last clinical visit.

RESULTS

The OLT group had significantly more subjects with less severe symptoms of UC (59, 68.6%) than the non-OLT group (12, 14.8%; P < .001). The subjects in the OLT group had a median of 0 UC flares compared with 3 in the non-OLT group (P < .001); fewer subjects in the OLT group required use of azathioprine or mercaptopurine (1, 1.2%), compared with the non-OLT group (14, 17.3%; P = .006). More subjects in the non-OLT group required colectomies (61, 75.3%) than in the OLT group (23, 26.7%; P < .001). On the basis of Cox regression analysis, OLT for PSC independently reduces the need for colectomy (hazard ratio [HR], 0.43; 95% confidence interval [CI], 0.25-0.75; P = .003), as does a high Mayo risk score at diagnosis (HR, 0.52; 95% CI, 0.37-0.72; P < .001). Development of colon neoplasia increased the risk for colectomy (HR, 2.47; 95% CI, 1.63-3.75; P < .001).

CONCLUSIONS

Severe progressive PSC that requires liver transplantation appears to reduce the disease activity of UC and the need for colectomy.

Progressive primary sclerosing cholangitis requiring liver transplantation is associated with reduced need for colectomy in patients with ulcerative colitis

BACKGROUND & AIMS

We investigated the association between the severity of primary sclerosing cholangitis (PSC) and clinical outcomes of patients with ulcerative colitis (UC) on the basis of need for colectomy.

METHODS

We analyzed data from 167 patients with PSC and UC who were followed from 1985 to 2011. Patients with PSC and UC were divided into groups that received orthotopic liver transplantation (OLT) (n = 86) or did not (non-OLT, n = 81). Clinical and demographic variables were obtained, and patients were followed until they received OLT or the date of their last clinical visit.

RESULTS

The OLT group had significantly more subjects with less severe symptoms of UC (59, 68.6%) than the non-OLT group (12, 14.8%; P < .001). The subjects in the OLT group had a median of 0 UC flares compared with 3 in the non-OLT group (P < .001); fewer subjects in the OLT group required use of azathioprine or mercaptopurine (1, 1.2%), compared with the non-OLT group (14, 17.3%; P = .006). More subjects in the non-OLT group required colectomies (61, 75.3%) than in the OLT group (23, 26.7%; P < .001). On the basis of Cox regression analysis, OLT for PSC independently reduces the need for colectomy (hazard ratio [HR], 0.43; 95% confidence interval [CI], 0.25-0.75; P = .003), as does a high Mayo risk score at diagnosis (HR, 0.52; 95% CI, 0.37-0.72; P < .001). Development of colon neoplasia increased the risk for colectomy (HR, 2.47; 95% CI, 1.63-3.75; P < .001).

CONCLUSIONS

Severe progressive PSC that requires liver transplantation appears to reduce the disease activity of UC and the need for colectomy.

Stromal cell-based immunotherapy in transplantation

Organs are composed of parenchymal cells that characterize organ function and nonparenchymal cells that are composed of cells in transit, as well as tissue connective tissue, also referred to as tissue stromal cells. It was originally thought that these tissue stromal cells provided only structural and functional support for parenchymal cells and were relatively inert. However, we have come to realize that tissue stromal cells, not restricted to in the thymus and lymphoid organs, also play an active role in modulating the immune system and its response to antigens. The recognition of these elements and the elucidation of their mechanisms of action have provided valuable insight into peripheral immune regulation. Extrapolation of these principles may allow us to utilize their potential for clinical application. In this article, we will summarize a number of tissue stromal elements/cell types that have been shown to induce hyporesponsiveness to transplants. We will also discuss the mechanisms by which these stromal cells create a tolerogenic environment, which in turn results in long-term allograft survival.

Tolerance-inducing strategies in islet transplantation

Allogeneic islet transplantation is a promising approach for restoring normoglycemia in type 1 diabetic patients. Current use of immunosuppressive therapies for management of islet transplant recipients can be counterintuitive to islet function and can lead to complications in the long term. The induction of donor-specific tolerance eliminates the dependency on immunosuppression and allows recipients to retain responses to foreign antigens. The mechanisms by which tolerance is achieved involve the deletion of donor-reactive T cells, induction of T-cell anergy, immune deviation, and generation of regulatory T cells. This review will outline the various methods used for inducing donor-specific tolerance in islet transplantation and will highlight the previously unforeseen potential of tissue stromal cells in promoting islet engraftment.

Hepatic blood flow plays an important role in ischemia-reperfusion injury

Severe ischemia/reperfusion (IR) injury is associated with poor hepatic microperfusion. The aim of this study was to investigate the role of hepatic artery flow (HAF) and portal vein flow (PVF) in IR injury. From January 2004 to June 2008, 566 patients underwent orthotopic liver transplantation (OLT). The data were retrospectively reviewed via the transplant database. Patients with hepatic artery (HA) or portal vein (PV) thrombosis and retransplant patients were excluded. Intraoperative PVF and HAF values and graft weights were measured routinely, and the central venous pressure, mean arterial pressure, cardiac output, and cardiac index were recorded with hepatic blood flow measurements. Complete data were available for 312 primary OLT recipients (215 males and 97 females; mean age = 54 ± 10 years). The patients' follow-up ranged from 215 to 1746 days (705 ± 408 days). IR injury was defined by the aspartate aminotransferase (AST) level on postoperative day (POD) 2, and the patients were divided into 3 groups: (1) mild IR injury [AST < 500 U/L; n = 160 (51%)], (2) moderate IR injury [AST = 500-1000 U/L; n = 85 (27%)], and (3) severe IR injury [AST > 1000 U/L; n = 67 (21%)]. The demographics and pre-OLT variables (the Model for End-Stage Liver Disease score (MELD), platelet counts, PV thrombosis, transjugular intrahepatic portosystemic shunts, and shunts on computed tomography scans) were similar in all groups. The graft survival rate was 99% in group 1, 95.2% in group 2 (P = 0.02), and 92.3% in group 3 (P = 0.016). The patient survival rates were similar in the 3 groups. The cold ischemia time (CIT) was significantly higher in group 3 versus group 1 (P < 0.007). In the statistical analysis, low HAF, PVF, total liver blood flow (TLBF), and augmented HAF values were associated with a greater likelihood of elevated AST levels on POD 2. The strongest univariate predictors of AST were reduced augmented HAF (mL/minute/100 g) values (P < 0.001) and reduced TLBF (mL/minute/100 g) values (P < 0.001). In a covariate analysis with adjustments for CIT and donor variables, the blood flow parameters remained important predictors of graft function. In conclusion, this report demonstrates for the first time that reduced hepatic blood flow is a significant finding in patients with severe hepatic IR injury.

Present state of immunosuppressive therapy in liver transplant recipients

1. Our increasing understanding of the signaling pathways and cellular interactions in transplant immunobiology has facilitated targeted strategies using novel immunosuppressive agents. 2. The pattern of immunosuppressive drug use in the United States continues to change, and the changes include the use of antibody induction therapy and the agents used in maintenance therapy. 3. The driving forces behind the development of new immunosuppressive regimens are the long-term complications of current immunosuppressive regimens (particularly renal dysfunction and metabolic disturbances).

Future prospects in immunosuppression for liver transplantation

1. Our increasing understanding of signaling pathways and cellular interactions in transplant immunobiology and the availability of novel immunosuppressive agents have facilitated targeted strategies. 2. The driving forces behind the development of new immunosuppressive regimens are the long-term complications of current immunosuppressive regimens (particularly renal dysfunction and metabolic disturbances). 3. By regulatory mandate, the requirement for the primary endpoint to be a composite of death, graft loss, and rejection remains intact; however, current and future clinical trials could incorporate key secondary endpoints that address renal and metabolic derangements.

The role of the A2a receptor agonist, regadenoson, in modulating hepatic artery flow in the porcine small-for-size liver graft

BACKGROUND

Hepatic artery vasoconstriction plays a major role in the pathophysiology of the small-for-size (SFS) liver graft injury and is reversed by adenosine. The A2a adenosine receptor (AR) has been suggested to be one of the key receptors that modulate hepatic hemodynamic changes. The aim of the study is to define the effects of the A2a AR agonist, regadenoson, in modulating hepatic artery flow (HAF) in SFS liver grafts of a porcine model.

METHODS

Seven female recipient pigs (66-70 kg) receiving 20% liver grafts were treated with regadenoson, 0.1 ug/kg/min starting on POD1 (n = 7). Results were compared with those with untreated 20% liver grafts (n= 8). The recipients were observed for 14 d. Hepatic artery flow (HAF) and portal vein flow (PVF) were recorded. Liver biopsies and serum samples were also taken at the designed time points through postoperative day (POD)14.

RESULTS

Dose-response curves of regadenoson established 0.1 ug/kg/min as the most effective dose of regadenoson for maintaining an increase in HAF. No adverse effects were seen with regadenoson infusion. HAF immediately increased by up to 2.2-fold after regadenoson infusion. The levels of daily average of HAF and percentage of HAF in total liver blood flow were 34.5% and 41.8%, respectively, higher in the regadenoson group than in the untreated group. Histologic scores of hepatic artery spasm and bile duct necrosis were significantly lower in the regadenoson group than in the untreated group (P = 0.01 and 0.04, respectively). The complication rates of hepatic artery thrombosis and gastrointestinal bleeding were lower in the regadenoson group than in the untreated group (0/7, 0% versus 2/8, 25% and 0/7, 0% versus 2/8 and 25%, respectively). The 14-d survival rates were 4/7 (57.1 %) in regadenoson group compared with 2/8 (25%) in the untreated group.

CONCLUSION

Adenosine A2a AR agonist, regadenoson, increases HAF in the recipients of SFS grafts with modest improvements in outcome.

Splenic artery embolization for the treatment of refractory ascites after liver transplantation

Refractory ascites (RA) is a challenging complication after orthotopic liver transplantation. Its treatment consists of the removal of the precipitating factors. When the etiology is unknown, supportive treatment can be attempted. In severe cases, transjugular intrahepatic portosystemic shunts, portocaval shunts, and liver retransplantation have been used with marginal results. Recently, splenic artery embolization (SAE) has been described as an effective procedure for reducing portal hyperperfusion in patients undergoing partial or whole liver transplantation. Here we describe our experience with SAE for the treatment of RA. Between June 2004 and June 2010, 6 patients underwent proximal SAE for RA. Intraoperative flow measurements, graft characteristics, embolization portal vein (PV) velocities before and after SAE, and spleen/liver volume ratios were collected and analyzed. The response to treatment was assessed with imaging (ultrasound/computed tomography) and on the basis of clinical outcomes (weight changes, diuretic requirements, and the time to ascites resolution). The PV velocity decreased significantly for each patient after the embolization (median = 66.5 cm/second before SAE and median = 27.5 cm/second after SAE, P < 0.01). All patients experienced a significant postprocedural weight loss (mean = 88.1 ± 28.4 kg before SAE and mean = 75.8 ± 28.4 kg after SAE, P < 0.01) and a dramatic decrease in their diuretic requirements. All but 1 of the patients experienced a complete resolution of ascites after a median time of 49.5 days (range = 12-295 days). No patient presented with postembolization complications. In conclusion, SAE was effective in reducing the PV velocity immediately after the procedure. Clinically, this translated into a dramatic weight loss, a reduction of diuretic use, and a resolution of ascites. SAE appears to be a safe and effective treatment for RA.

Hepatic stellate cells regulate immune response by way of induction of myeloid suppressor cells in mice

Although organ transplants have been applied for decades, outcomes of somatic cell transplants remain disappointing, presumably due to lack of appropriate supporting stromal cells. Thus, cotransplantation with liver stromal cells, hepatic stellate cells (HSC), achieves long-term survival of islet allografts in mice by way of induction of effector T cell apoptosis and generation of regulatory T (Treg) cells. In this study we provide evidence both in vitro and in vivo that HSC can promote generation of myeloid-derived suppressor cells (MDSC). HSC-induced MDSC demonstrate potent immune inhibitory activity. Induction of MDSC is dependent on an intact interferon gamma signaling pathway in HSC and is mediated by soluble factors, suggesting that the specific tissue stromal cells, such as HSC, play a crucial role in regulating immune response by way of inflammation-induced generation of MDSC. Large amounts of MDSC can be propagated in vitro from bone marrow-derived myeloid precursor cells under the influence of HSC.

CONCLUSION

Cotransplantation with in vitro generated MDSC can effectively protect islet allografts from host immune attack. Local delivery of potent immune suppressor cells for cell transplants holds great clinical application potential.

Use of tissue plasminogen activator in liver transplantation from donation after cardiac death donors

Ischemic-type biliary stricture (ITBS) occurs in up to 50% after liver transplantation (LT) from donation after cardiac death (DCD) donors. Thrombus formation in the peribiliary microcirculation is a postulated mechanism. The aim was to describe our experience of tissue plasminogen activator (TPA) administration in DCD-LT. TPA was injected into the donor hepatic artery on the backtable (n = 22). Two recipients developed ITBS including one graft failure. Although excessive postreperfusion bleeding was seen in 14 recipients, the amount of TPA was comparable between those with and without excessive bleeding (6.4 ± 2.8 vs. 6.6 ± 2.8 mg, p = 0.78). However, donor age (41 ± 12 vs. 29 ± 9 years, p = 0.02), donor BMI (26.3 ± 5.5 vs. 21.7 ± 3.6 kg/m(2) , p = 0.03), previous laparotomy (50% vs. 0%, p = 0.02) and lactate after portal reperfusion (6.3 ± 4.6 vs. 2.8 ± 0.9 mmol/L, p = 0.005) were significantly greater in recipients with excessive bleeding. In conclusion, the use of TPA may lower the risk of ITBS-related graft failure in DCD-LT. Excessive bleeding may be related to poor graft quality and previous laparotomy rather than the amount of TPA. Further studies are needed in larger population.

Deep hypothermia with circulatory arrest to aid in the management of suprahepatic vena cava stenosis after liver transplantation

Liver transplantation is the treatment of choice for many liver diseases in the pediatric population. Complications involving late suprahepatic vena cava obstructions after liver transplantation are not common, but they tend to be more frequently seen in pediatric recipients. When such complications have occurred, approaches involving direct abdominal surgery or interventional radiology guidance have been used with satisfactory results. We present a case report of an alternative approach to a suprahepatic vena cava complication. An 18-year-old man who underwent pediatric liver transplantation for biliary atresia presented with a symptomatic total occlusion of the suprahepatic caval anastomosis that could not be crossed with a wire. We used a right atrial approach and hypothermic circulatory (cardiac) arrest. The anastomotic stricture was easily identified and excised. The postoperative course was uneventful with a rapid resolution of the symptoms. Because the occlusion was not amenable to angioplasty or stenting, a direct surgical approach was necessary. The right atrial approach with hypothermic cardiac arrest gave us direct access to the obliterated cavoatrial anastomosis through a virgin area and allowed us to avoid the difficulties and dangers of the large collaterals in the abdomen.

Complement mediated hepatocytes injury in a model of autoantibody induced hepatitis

Despite multiple reports on autoantibody-initiated complement activation in autoimmune hepatitis (AIH), how does the humoral immunity contribute to the pathogenesis of AIH remained unclear. In this report, by adoptively transferring a polyclonal rabbit anti-OVA antibody into Hep-OVA Tg mice in which OVA is selectively expressed on the surface of hepatocytes, we found that excessive complement activation initiated by the autoantibody overwhelmed the protection of intrinsic cell surface complement regulators, and induced hepatocytes injury both in vitro and in vivo. The anti-OVA antibody induced hepatic injury in Hep-OVA Tg but not WT C57BL/6 mice as assessed by serum ALT levels and liver histopathology. Immunohistochemical analyses showed that after the antibody administration, there was massive complement activation on anti-OVA IgG coated hepatocytes in Hep-OVA Tg mice, but not in WT mice. Consistent with these results, depleting complement by cobra venom factor (CVF) prior to antibody injections protected Hep-OVA Tg mice from anti-OVA IgG induced hepatic injury. In addition, treating Hep-OVA Tg mice with recombinant mouse decay accelerating factor, a native complement inhibitor, protected them from autoantibody induced hepatitis. These results suggest that complement could play a pivotal role in liver specific autoantibody mediated hepatocyte injury in AIH, and that complement inhibitors could be, in principle, developed as novel therapeutics against AIH.

A critical role of TRAIL expressed on cotransplanted hepatic stellate cells in prevention of islet allograft rejection

Hepatic stellate cells (HSCs) have demonstrated a strong T-cell inhibitory activity. In a mouse islet transplantation model, cotransplanted HSCs can protect islet allografts from rejection. The involved mechanism is not fully understood. We showed in this study that expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), an important apoptosis-inducing ligand, on HSCs was crucial in protection of islet allografts, since HSCs derived from TRAIL knockout mice demonstrated less inhibitory activity towards T-cell proliferative responses, and substantially lost their capacity in protecting cotransplanted islet allografts from rejection, suggesting that TRAIL-mediated T cell apoptotic death is important in HSC-delivered immune regulation activity.

Glucose balance of porcine liver allograft is an important predictor of outcome

BACKGROUND

The role of glucose metabolism in predicting postoperative liver graft function after transplantation is unclear. We investigated the relation between intraoperative glucose balance of the liver allograft and the postoperative graft function and survival in a porcine partial liver transplant model.

MATERIALS AND METHODS

Experiments follow Guiding Principles in the Care and Use of Animals. Fourteen female pigs received liver allografts of 17%-39% recipient liver volume. Recipients were classified into two groups based on positive glucose balance: the mean intraoperative blood glucose of the graft outflow was greater than the blood glucose of inflow, negative glucose balance: the mean blood glucose of graft outflow was less than blood glucose of inflow. Perioperative data and survival were studied.

RESULTS

In the positive group (n=9) intraoperative hepatic artery flow was significantly higher (P=0.028), and oxygen consumption was lower (P=0.018) than the negative group (n=5). Postoperatively, maximal serum aspartate aminotransferase (AST) (P=0.028), alanine aminotransferase (ALT) (P=0.028), and total bilirubin (P=0.027) of the positive group were significantly lower than the negative group. In survival analysis, the positive group had significantly better survival rate than the negative group (P=0.034). Using Periodic acid-Schiff staining, glycogen content of the allograft in the positive group at 10 min post-reperfusion was significantly decreased in comparison with the baseline value in the normal liver (P=0.005), however not statistically different in the negative group (P=0.175).

CONCLUSION

Intraoperative glucose balance can be used as an early predictor of the graft function following transplantation of partial liver allografts.

Themes of liver transplantation

Liver transplantation was the product of five interlocking themes. These began in 1958-1959 with canine studies of then theoretical hepatotrophic molecules in portal venous blood (Theme I) and with the contemporaneous parallel development of liver and multivisceral transplant models (Theme II). Further Theme I investigations showed that insulin was the principal, although not the only, portal hepatotrophic factor. In addition to resolving long-standing controversies about the pathophysiology of portacaval shunt, the hepatotrophic studies blazed new trails in the regulation of liver size, function, and regeneration. They also targeted inborn metabolic errors (e.g., familial hyperlipoproteinemia) whose palliation by portal diversion presaged definitive correction with liver replacement. Clinical use of the Theme II transplant models depended on multiple drug immunosuppression (Theme III, Immunology), guided by an empirical algorithm of pattern recognition and therapeutic response. Successful liver replacement was first accomplished in 1967 with azathioprine, prednisone, and antilymphoid globulin. With this regimen, the world's longest surviving liver recipient is now 40 years postoperative. Incremental improvements in survival outcome occurred (Theme IV) when azathioprine was replaced by cyclosporine (1979), which was replaced in turn by tacrolimus (1989). However, the biologic meaning of alloengraftment remained enigmatic until multilineage donor leukocyte microchimerism was discovered in 1992 in long-surviving organ recipients. Seminal mechanisms were then identified (clonal exhaustion-deletion and immune ignorance) that linked organ engraftment and the acquired tolerance of bone marrow transplantation and eventually clarified the relationship of transplantation immunology to the immunology of infections, neoplasms, and autoimmune disorders. With this insight, better strategies of immunosuppression have evolved. As liver and other kinds of organ transplantation became accepted as healthcare standards, the ethical, legal, equity, and the other humanism issues of Theme V have been resolved less conclusively than the medical-scientific problems of Themes I-IV.

Liver transplantation in the United States, 1999-2008

Changes in organ allocation policy in 2002 reduced the number of adult patients on the liver transplant waiting list, changed the characteristics of transplant recipients and increased the number of patients receiving simultaneous liver-kidney transplantation (SLK). The number of liver transplants peaked in 2006 and declined marginally in 2007 and 2008. During this period, there was an increase in donor age, the Donor Risk Index, the number of candidates receiving MELD exception scores and the number of recipients with hepatocellular carcinoma. In contrast, there was a decrease in retransplantation rates, and the number of patients receiving grafts from either a living donor or from donation after cardiac death. The proportion of patients with severe obesity, diabetes and renal insufficiency increased during this period. Despite increases in donor and recipient risk factors, there was a trend towards better 1-year graft and patient survival between 1998 and 2007. Of major concern, however, were considerable regional variations in waiting time and posttransplant survival. The current status of liver transplantation in the United States between 1999 and 2008 was analyzed using SRTR data. In addition to a general summary, we have included a more detailed analysis of liver transplantation for hepatitis C, retransplantation and SLK transplantation.

Is impaired hepatic arterial buffer response a risk factor for biliary anastomotic stricture in liver transplant recipients?

BACKGROUND

Blood flow to the liver is partly maintained by the hepatic arterial buffer response (HABR), which is an intrinsic autoregulatory mechanism. Temporary clamping of the portal vein (PV) results in augmentation in hepatic artery flow (augHAF). Portal hyperperfusion impairs HAF due to the HABR in liver transplantation (LT). The aim of this study is to examine the effect of the HABR on biliary anastomotic stricture (BAS).

METHODS

In 234 cadaveric whole LTs, PV flow (PVF), basal HAF, and augHAF were measured intra-operatively after allograft implantation. All recipients with a vascular complication were excluded. Buffer capacity (BC) was calculated as (augHAF - basal HAF)/PVF to quantify the HABR. Recipients were divided into 2 groups based on their BC: low BC (<0.074; n = 117) or high BC (> or =0.074; n = 117).

RESULTS

Of the 234 recipients, 23 (9.8%) had early BAS (< or =60 days after LT) and 18 (7.7%) had late BAS (>60 days after LT). The incidence of late BAS and bile leakage was similar between the groups; however, the incidence of early BAS in the low BC group was greater than that in the high BC group (15% vs 5.1%; P = .0168). In the multivariate analysis, low BC (P = .0325) and bile leakage (P = .0002) were found to be independent risk factors affecting early BAS.

CONCLUSION

Recipients with low BC who may have impaired HABR are at greater risk of early BAS after LT. Intraoperative measurements of blood flow help predict the risk of BAS.

Mechanistic insights into immunomodulation by hepatic stellate cells in mice: a critical role of interferon-gamma signaling

The liver is considered to be an immune-privileged organ that favors the induction of tolerance. The underlying mechanisms are not completely understood. Interestingly, liver transplants are spontaneously accepted in several animal models, but hepatocyte transplants are acutely rejected, suggesting that liver nonparenchymal cells may effectively protect the parenchymal cells from immune attack. We have shown the profound T cell inhibitory activity of hepatic stellate cells (HSCs). Thus, cotransplantation with HSCs effectively protects islet allografts from rejection in mice. In this study, using T cell receptor transgenic and gene knockout approaches, we provided definitive evidence that HSCs protected cotransplanted islet allografts by exerting comprehensive inhibitory effects on T cells, including apoptotic death in graft-infiltrating antigen-specific effector T cells and marked expansion of CD4(+) Forkhead box protein (Foxp)3(+) T regulatory (Treg) cells. All these effects required an intact interferon-gamma (IFN-gamma) signaling in HSCs, demonstrated by using HSCs isolated from IFN-gamma receptor 1 knockout mice. B7-H1 expression on HSCs, a product molecule of IFN-gamma signaling, was responsible for induction of T cells apoptosis, but had no effect on expansion of Treg cells, suggesting that undetermined effector molecules produced by IFN-gamma signaling is involved in this process.

CONCLUSION

Upon inflammatory stimulation, specific organ stromal cells (such as HSCs in the liver) demonstrate potent immune regulatory activity. Understanding of the mechanisms involved may lead to development of novel strategies for clinical applications in transplantation and autoimmune diseases.

Adenosine restores the hepatic artery buffer response and improves survival in a porcine model of small-for-size syndrome

The aim of the study is to define the role of the HABR in the pathophysiology of the SFS liver graft and to demonstrate that restoration of hepatic artery flow (HAF) has a significant impact on outcome and improves survival. Nine pigs received partial liver allografts of 60% liver volume, Group 1; 8 animals received 20% LV grafts, Group 2; 9 animals received 20% LV grafts with adenosine infusion, Group 3. HAF and portal vein flow (PVF) were recorded at 10 min, 60 min and 90 min post reperfusion, on POD 3 and POD 7 in Group 1, and daily in Group 2 and 3 up to POD 14. Baseline HAF and PVF (ml/100 g/min) were 29 +/- 12 (mean +/- SD) and 74 +/- 8 respectively, with 28% of total liver blood flow (TLBF) from the HA and 72% from the PV. PVF peaked at 10 mins in all groups, increasing by a factor of 3.8 in the 20% group compared to an increase of 1.9 in the 60% group. By POD 7-14 PVF rates approached baseline values in all groups. The HABR was intact immediately following reperfusion in all groups with a reciprocal decrease in HAF corresponding to the peak PVF at 10 min. However in the 20% group HAF decreased to 12 +/- 8 ml/100 g/min at 90 min and remained low out to POD 7-14 despite restoration of normal PVF rates. Histopathology confirmed evidence of HA vasospasm and its consequences, cholestasis, centrilobular necrosis and biliary ischemia in Group 2. HA infusion of adenosine significantly improved HAF (p < .0001), reversed pathological changes and significantly improved survival (p = .05). An impaired HABR is important in the pathophysiology of the SFSS. Reversal of the vasospasm significantly improves outcome.

Distinct response of liver myeloid dendritic cells to endotoxin is mediated by IL-27

BACKGROUND/AIMS

The liver lies downstream of the gut, and is constantly exposed to bacteria. Liver dendritic cells (DC) are known to possess properties of tolerance, and respond to LPS differently when compared to conventional DC, but the underlying mechanisms are not completely understood. The aim of this study was to evaluate liver DC response to LPS stimulation.

METHODS

Liver or spleen derived DC were isoloated from mice treated with plasmid-GM-CSF hydrodynamic injection. The surface molecules and TLR4 expression on DC and cytokine productions of LPS stimulated DC were determinded by FACS analysis, ELISA and qPCR. The ability of DC to elicit T cell responses and differentiation were examined by MLR/CTL assay and qPCR for molecular markers related to Th1/Th2/Treg.

RESULTS

In this study, we demonstrated that the threshold of LPS stimulation for liver DC was markedly higher than spleen DC, even though the expression of TLR4 on both DCs was comparable. In contrast to spleen DC that produced high levels of IL-12 and induced Th1 response upon LPS stimulation, LPS-liver DC preferentially produced IL-10 and IL-27, instead of IL-12. In addition, liver DC induced T cell hyporesponsiveness, associated with selective expansion of CD4(+)Foxp3(+)T regulatory cells. Addition of exogenous IL-12 only slightly enhanced liver DC-induced T cell response. Interestingly, abrogation of IL-27 ligation by using IL-27R(-/-) T cells synergistically augmented the effect of IL-12, suggesting that IL-27 produced by liver DC plays a crucial role in induction of T cell hyporesponsiveness.

CONCLUSIONS

Liver DC respond distinctly to LPS stimulation by secreting IL-27 which synergizes with silencing of bioactive IL-12 activity leading to profound T cell inhibition.