Changes in portal venous pressure in the early phase after living donor liver transplantation: pathogenesis and clinical implications

Outcome of patients undergoing right lobe living donor liver transplantation with small-for-size grafts

AIM: To investigate the outcome of living donor liver transplantation (LDLT) recipients transplanted with small-for-size grafts (SFSGs).

METHODS: Between November 2001 and December 2010, 196 patients underwent LDLT with right lobe liver grafts at our center. Recipients were divided into 2 treatment groups: group A with an actuarial graft-to-recipient weight ratio (aGRWR) < 0.8% (n = 45) and group B with an aGRWR ≥ 0.8% (n = 151). We evaluated serum liver function markers within 4 wk after transplantation. We also retrospectively evaluated the outcomes of these patients for potential effects related to the recipients, the donors and the transplantation procedures based upon a review of their medical records.

RESULTS: Small-for-size syndrome (SFSS) developed in 7 of 45 patients (15.56%) in group A and 9 of 151 patients (5.96%) in group B (P = 0.080). The levels of alanine aminotransferase and aspartate aminotransferase in group A were higher than those in group B during early period after transplantation, albeit not significantly. The cumulative 1-, 3- and 5-year liver graft survival rates were 82.22%, 71.11% and 71.11% for group A and 81.46%, 76.82%, and 75.50% for group B patients, respectively (P = 0.623). However, univariate analysis of risk factors associated with graft survival in group A demonstrated that the occurrence of SFSS after LDLT was the only significant risk factor affecting graft survival (P < 0.001). Furthermore, multivariate analysis of our data did not identify any additional significant risk factors accounting for poor graft survival.

CONCLUSION: Our study suggests that LDLT recipients with an aGRWR < 0.8% may have liver graft outcomes comparable to those who received larger size grafts. Further studies are required to ascertain the safety of using SFSGs.

How do transplant surgeons accomplish optimal portal venous flow during living-donor liver transplantation? Noninvasive measurement of indocyanine green elimination rate

BACKGROUND

Balancing donor safety and graft volume is difficult. We previously reported that intentional modulation of portal venous pressure (PVP) during living-donor liver transplantation (LDLT) is crucial to overcoming problems with small-for-size grafts; however, detailed studies of portal venous flow (PVF) and a reliable parameter are still required.

PATIENTS AND METHODS

The elimination rate (k) of indocyanine green (ICG) was measured in 49 adult LDLT recipients. PVP was controlled during LDLT, with a target of <20 mm Hg. ICG reflects hepatocyte volume and effective PVF. The kICG value is divided by the graft weight to calculate PVF. Recipients were divided into 2 groups: those with severe and/or fatal complications within 1 month after LDLT and those without.

RESULTS

Survival rates and postoperative profiles were significantly different between the 2 groups. Univariate analysis showed significant differences in ABO blood group, final PVP, final kICG, and the final kICG/graft weight value; however, multivariate analysis showed that only the kICG/graft weight value was significant. The cutoff level for the final kICG/graft weight value for predicting successful LDLT was 3.1175 × 10(-4)/g.

CONCLUSION

Accurate evaluation and monitoring of optimal PVF during LDLT should overcome the use of small-for-size grafts and improve donor safety and recipient outcomes.

Left hepatectomy versus right hepatectomy for living donor liver transplantation: shifting the risk from the donor to the recipient

Living donor liver transplantation (LDLT), originally used in children with left lateral segment grafts, has been expanded to adults who require larger grafts to support liver function. Most adult LDLT procedures have been performed with right lobe grafts, and this means a significant risk of morbidity for the donors. To minimize the donor risk for adults, there is renewed interest in smaller left lobe grafts. The smaller graft size increases the recipient risk in the form of small-for-size syndrome (SFSS) and essentially transfers the risk from the donor to the recipient. We review the donor and recipient risks of LDLT and pay particular attention to the different types of liver grafts and the use of graft inflow modification to ameliorate the risk of SFSS. Finally, a new metric is proposed for quantifying the recipient benefit in exchange for a specific donor risk.

Liver retransplantation for adult recipients

Living donor liver graft can be used for the first or second liver transplantation. The timing of retransplantation also should be stratified as 2 types according to the reoperation timing. Combination of these two classifications results in 6 types of living donor liver transplantation (LDLT)-associated retransplantation. However, late retransplantation to LDLT might have not been performed in most LDLT programs, thus other 4 types of LDLT-associated retransplantation can be taken into account. The most typical type of LDLT-associated retransplantation might be early living donor-to-deceased donor retransplantation. For early living donor-to-living donor retransplantation, its eligibility criteria might be similar to those of early living donor-to-deceased donor retransplantation. For early deceased donor-to-living donor retransplantation, its indications are exactly the same to those for aforementioned living donor-to-living donor retransplantation. Late deceased donor retransplantation after initial LDLT has the same indication for ordinary late deceased donor retransplantation.

"Small-for-flow" syndrome: shifting the "size" paradigm

The "small-for-size" syndrome and "post-hepatectomy liver failure" refers to the development of liver failure (hyperbilirubinemia, coagulopathy, encephalopathy and refractory ascites) resulting from the reduction of liver mass beyond a certain threshold. This complication is associated with a high mortality and is a major concern in liver transplantation involving reduced liver grafts from deceased and living donors as well as in hepatic surgeries involving extended resections of liver mass. The limiting threshold for liver resection or transplantation is currently predicted based on the mass of the remnant liver (or donor graft) in relation to the body weight of the patient, with a ratio above 0.8 being considered safe. This approach, however, has proved inaccurate, because some patients develop the "small-for-size" syndrome despite complying with the "safe" threshold while other patients who surpass the threshold do not develop it. We hypothesize that the development of the "small-for-size" syndrome is not exclusively determined by the ratio of the mass of the liver remnant (or graft) to the body weight, but it is instead strictly determined by the hemodynamic parameters of the hepatic circulation. This hypothesis is based in recent clinical and experimental reports showing that relative portal hyperperfusion is a critical factor in the development of the "small-for-size" syndrome and that maneuvers that manipulate the hepatic vascular inflow are able to prevent the development of the syndrome despite liver-to-body weight ratios well below the "limiting" threshold. Measurements of hepatic blood flow and pressure, however, are not routinely performed in hepatic surgeries. Focusing on the "flow" rather than in the "size" may improve our understanding of the pathophysiology of the "small-for-size" syndrome and "post-hepatectomy liver failure" and it would have important implications for the clinical management of patients at risk. First, hepatic hemodynamic parameters would have to be measured in hepatic surgeries. Second, these parameters (in addition to liver mass) would be the principal basis for deciding the "safe" threshold of viable liver parenchyma. Third, the hepatic hemodynamic parameters are amenable to manipulation and, consequently, the "safe" threshold may also be manipulated. Shifting the paradigm from "small-for-size" to "small-for-flow" syndrome would thus represent a major step for optimizing the use of donor livers, for expanding the indications of hepatic surgery, and for increasing the safety of these procedures.

Importance of the temporary portocaval shunt during adult living donor liver transplantation

Adult living donor liver transplantation (aLDLT) is associated with surgical risks for the donor and with the possibility of small-for-size syndrome (SFSS) for the recipient, with both events being of great importance. An excessively small liver graft entails a relative increase in the portal blood flow during reperfusion, and this factor predisposes the recipient to an increased risk of SFSS in the postoperative period, although other causes related to recipient, graft, and technical factors have also been reported. A hemodynamic monitoring protocol was used for 45 consecutive aLDLT recipients. After various hemodynamic parameters before reperfusion were analyzed, a significant correlation between the temporary portocaval shunt flow during the anhepatic phase and the portal vein flow (PVF) after reperfusion of the graft (R(2) = 0.3, P < 0.001) was found, and so was a correlation between the native liver portal pressure and PVF after reperfusion (R(2) = 0.21, P = 0.007). The identification of patients at risk for excessive portal hyperflow will allow its modulation before reperfusion. This could favor the use of smaller grafts and ultimately lead to a reduction in donor complications because it would allow more limited hepatectomies to be performed.

Small-for-size syndrome in living donor liver transplantation

When the graft volume is too small to satisfy the recipient's metabolic demand, the recipient may thus experience small-for-size syndrome (SFSS). Because the occurrence of SFSS is determined by not only the liver graft volume but also a combination of multiple negative factors, the definitions of small-for-size graft (SFSG) and SFSS are different in each institute and at each time. In the clinical setting, surgical inflow modulation and maximizing the graft outflow are keys to overcoming SFSS. Accordingly, relatively smaller-sized grafts can be used with surgical modification and pharmacological manipulation targeting portal circulation and liver graft quality. Therefore, the focus of the SFSG issue is now shifting from how to obtain a larger graft from the living donor to how to manage the use of a smaller graft to save the recipient, considering donor safety to be a priority.

[Hemodynamic monitoring protocol during living donor liver transplantation]

INTRODUCTION

The recipient of an adult living donor liver transplant (ALDLT) is subjected to great haemodynamic changes that could lead to the appearance of a "small-for-size" syndrome in the post-operative period due to portal hyperflow. The aim of this article is to evaluate these changes, and try to correlate them with portal vein flow during reperfusion.

MATERIAL AND METHODS

A protocol for monitoring various liver haemodynamic data of the ALDLT recipient before, during and after surgery has been used since the year 2003. The haemodynamic outcome of the recipient after the transplant, as well as the correlation between the portal vein flow during reperfusion and the collected haemodynamic data is analysed.

RESULTS

There was no small for size syndrome. A significant relationship was found between the portal flow during reperfusion and the portal vein pressure at the beginning of the operation (r=0.46, P<.006) and with the portocaval shunt flow during the anhepatic phase (r=0.55, P<.001). The recipients showed a normal splanchnic hemodynamic state at 3 months after the transplant.

CONCLUSIONS

Haemodynamic monitoring of the ALDLT recipient is essential to prevent portal hyperflow. The relationship between flow during reperfusion and flow through the portocaval shunt means that patients with a higher risk of hyperflow can be identified and can be modified before reperfusion.

How transplant surgeons can overcome the inevitable insufficiency of allograft size during adult living-donor liver transplantation: strategy for donor safety with a smaller-size graft and excellent recipient results

Small-for-size grafts are an issue in liver transplantation. Portal venous pressure (PVP) was monitored and intentionally controlled during living-donor liver transplantation (LDLT) in 155 adult recipients. The indocyanine green elimination rate (kICG) was simultaneously measured in 16 recipients and divided by the graft weight (g) to reflect portal venous flow (PVF). The target PVP was <20 mmHg. Patients were divided by the final PVP (mmHg): Group A, PVP < 12; Group B, 12 ≤ PVP < 15; Group C, 15 ≤ PVP < 20; and Group D, PVP ≥ 20. With intentional PVP control, we performed splenectomy and collateral ligation in 80 cases, splenectomy in 39 cases, and splenectomy, collateral ligation, and additional creation in five cases. Thirty-one cases received no modulation. Groups A and B showed good LDLT results, while Groups C and D did not. Final PVP was the most important factor for the LDLT results, and the PVP cutoffs for good outcomes and clinical courses were both 15.5 mmHg. The respective kICG/graft weight cutoffs were 3.5580 × 10(-4) /g and 4.0015 × 10(-4) /g. Intentional PVP modulation at <15 mmHg is a sure surgical strategy for small-for-size grafts, to establish greater donor safety with good LDLT results. The kICG/graft weight value may have potential as a parameter for optimal PVF and a predictor for LDLT results.

Dual cytoprotective effects of splenectomy for small-for-size liver transplantation in rats

The problems associated with small-for-size liver grafts (ie, high mortality rates, postoperative complications, and acute rejection) remain critical issues in partial orthotopic liver transplantation (OLT). In association with partial OLT, splenectomy (SP) is a procedure used to reduce the portal pressure. However, the precise effects of SP on partial OLT have been unclear. In this study, using small-for-size liver grafts in rats, we examined the cytoprotective effects of SP on OLT. Liver grafts were assigned to 2 groups: a control group (OLT alone) and an SP group (OLT after SP). SP significantly increased animal survival and decreased liver damage. SP exerted the following cytoprotective effects: (1) it improved hepatic microcirculation and prevented increases in the portal pressure after OLT, (2) it suppressed the hepatic infiltration of neutrophils and macrophages through the direct elimination of splenic inflammatory cells before OLT, (3) it decreased the hepatic expression of tumor necrosis factor α and interleukin-6, (4) it attenuated sinusoidal endothelial injury, (5) it decreased plasma endothelin 1 levels and increased hepatic heme oxygenase 1 expression, (6) it suppressed hepatocellular apoptosis through the down-regulation of hepatic caspase-3 and caspase-8 activity, and (7) it increased hepatic regeneration. In conclusion, SP for small-for-size grafts exerts dual cytoprotective effects by preventing excessive portal vein hepatic inflow and eliminating splenic inflammatory cell recruitment into the liver; this in turn inhibits hepatocellular apoptosis and improves liver regeneration.

Small-for-size syndrome after living donor liver transplantation: successful treatment with a transjugular intrahepatic portosystemic shunt

Small-for-size syndrome (SFSS) is a serious complication after living donor liver transplantation (LDLT) that can disrupt liver regeneration and result in hepatic dysfunction. Until now, the treatment options for SFSS after LDLT have been very limited. Here we describe a patient with SFSS after LDLT who was successfully treated with a transjugular intrahepatic portosystemic shunt (TIPS). A 56-year-old man who had undergone adult-to-adult LDLT because of decompensated liver cirrhosis started displaying signs of acute jaundice and ascites within 72 hours of the operation. The patient was diagnosed with SFSS, and because he had already undergone splenectomy before the transplant, partial splenic embolization was not feasible. Consequently, the TIPS procedure was chosen in an attempt to reduce portal hyperperfusion. After the procedure, the patient's symptoms were gradually ameliorated and were eventually resolved. In conclusion, when partial splenic embolization is not feasible, TIPS placement may be a feasible option for the treatment of SFSS after LDLT.

[Small-for-size: experimental findings for liver surgery]

The characteristics of the hepatic macrocirculation, i.e., the parallel portal-venous and arterial blood supply, is of utmost relevance for liver surgery. With extended hepatectomy or transplantation of a reduced-size liver the remaining or transplanted liver tissue is overperfused because the liver fails to regulate the portal-venous inflow. This portal hyperperfusion is responsible for the initiation of liver cell proliferation but represents at the same time one of the substantial events in the pathogenesis of the small-for-size syndrome. Portal-venous hyperperfusion, the so-called hepatic arterial buffer response, which describes the semi-reciprocal relationship between the portal-venous and hepatic arterial blood flows, leads to an arterial hypoperfusion of the small-for-size liver. In this article experimental and clinical data are discussed which underline the high but so far overseen relevance of this arterial underperfusion in the development of a small-for-size syndrome.

Is left lobe adult-to-adult living donor liver transplantation ready for widespread use? The US experience (1998-2010)

OBJECTIVES

Living donor liver transplantation (LDLT) is an accepted treatment for patients with end-stage liver disease. To minimize risk to the donor, left lobe (LL) LDLT may be an ideal option in adult LDLT.

METHODS

This study assessed the outcomes of LL-LDLT compared with right lobe (RL) LDLT in adults (1998-2010) as reported to the United Network for Organ Sharing (UNOS) Organ Procurement and Transplantation Network (OPTN).

RESULTS

A total of 2844 recipients of LDLT were identified. Of these, 2690 (94.6%) underwent RL-LDLT and 154 (5.4%) underwent LL-LDLT. A recent increase in the number of LL-LDLTs was noted: average numbers of LL-LDLTs per year were 5.2 during 1998-2003 and 19.4 during 2004-2010. Compared with RL-LDLT recipients, LL-LDLT recipients were younger (mean age: 50.5 years vs. 47.0 years), had a lower body mass index (BMI) (mean BMI: 24.5 kg/m(2) vs. 26.8 kg/m(2)), and were more likely to be female (64.6% vs. 41.9%). Donors in LL-LDLT had a higher BMI (mean BMI: 29.4 kg/m(2) vs. 26.5 kg/m(2)) and were less likely to be female (30.9% vs. 48.1%). Recipients of LL-LDLT had a longer mean length of stay (24.9 days vs. 18.2 days) and higher retransplantation rates (20.3% vs. 10.9%). Allograft survival in LL-LDLT was significantly lower than in RL-LDLT and there was a trend towards inferior patient survival. In Cox regression analysis, LL-LDLT was found to be associated with an increased risk for allograft failure [hazard ratio (HR): 2.39)] and inferior patient survival (HR: 1.86).

CONCLUSIONS

The number of LL-LDLTs has increased in recent years.

Challenges and Outcome of Left-lobe Liver Transplants in Adult Living Donor Liver Transplants

Adult-to-adult living donor liver transplant (LDLT) frequently depend on using the right-lobes of the donor for obtaining adequate graft-to-recipient weight ratio (GRWR) of over 0.8% in the recipient. However, left-lobes remain an important option in adults, since the morbidity in the donor is considerably less with left donor hepatectomy when compared with right side liver resection. Further benefits of left-lobes in LDLT include more predictable anatomy of the left hepatic duct and left portal vein, which are usually long and single resulting in easier anastomosis in the recipient. Likewise, left-lobe grafts are easier to implant with an excellent venous outflow through the combined orifice of left and middle hepatic vein, as opposed to the complex hepatic vein reconstruction required in right-lobe grafts. However, left hepatic artery is often multiple unlike the right hepatic artery. The holy grail of left-lobe transplants is avoidance of small for size syndrome (SFSS) in the recipients. The strategies for overcoming SFSS currently depend on circumventing portal hyperperfusion in the graft. Measurement of portal pressure and modulating it if high, by splenic artery ligation, splenectomy, or hemiportocaval shunts are proving successful in avoiding SFSS. The future aim in adult LDLT should be to use the left-lobe as much as possible for the benefit of the donor at the same time avoiding SFSS even at very low GRWR for the benefit of the recipient.

Implanted adipose-derived stem cells attenuate small-for-size liver graft injury by secretion of VEGF in rats

Graft injury after small-for-size liver transplantation impairs graft function and threatens the survival of the recipients. The use of adipose-derived stem cells (ADSCs) for liver injury protection and repair is promising. Our aim was to investigate the role of vascular endothelial growth factor (VEGF) secreted by ADSCs in the treatment of small-for-size liver graft injury. Studies were performed using ADSCs with VEGF secretion blocked by RNA interference. In vitro, ADSCs prevented apoptosis of freshly isolated liver sinusoidal endothelial cells (LSECs) by secretion of VEGF. Syngeneic 35% orthotopic liver transplantation followed by implantation of syngeneic ADSCs through the portal vein system was performed using Wistar rats. We found VEGF secreted by implanted ADSCs improved graft microcirculatory disturbances, serum liver function parameters and survival. The improved microcirculatory status was also reflected by reduced hepatocellular damage, especially LSEC apoptosis and improved liver regeneration. These effects were accompanied by decreased expression of endothelin receptor type A, increased Bcl-2/Bax ratio, decreased expression of Bad and elevated proportion of phosphorylated Bad. In conclusion, implanted syngeneic ADSCs attenuated small-for-size liver graft injuries and subsequently enhanced liver regeneration in a rat 35% liver transplantation model. The VEGF secreted by implanted ADSCs played a crucial role in this process.

Current status of organ transplantation in Japan

To overcome severe donor shortage, Japanese doctors over the years have developed innovative strategies to maximize organs transplanted per brain death donor and expanded the donor pool using living donors. They also used living and marginal organs and drastically improved living donor lung, liver, pancreas and kidney transplantations. Moreover, they initiated ABO blood type incompatible liver transplantation advancements and succeeded in overcoming the blood type barrier in kidney and liver transplantations. Similar efforts are underway for pancreas transplantation. Furthermore, Japanese doctors have developed a nonaggressive step to achieve immunosuppression following organ transplantation by carefully monitoring donor-specific hyporesponsiveness and infectious immunostatus. However, the institution of amendments to allocation systems and the intensification of efforts to decrease living donor morbidity and to increase the number of brain death donors have remained important issues needing attention. Overall, the strategies Japan has adopted to overcome donor shortage can provide useful insights on how to increase organ transplantations.

Left lobe adult-to-adult living donor liver transplantation: Should portal inflow modulation be added?

Recently, the successful application of portal inflow modulation has led to renewed interest in the use of left lobe grafts in adult-to-adult living donor liver transplantation (LDLT). However, data on the hepatic hemodynamics supporting portal inflow modulation are limited, and the optimal portal circulation for a liver graft is still unclear. We analyzed 42 consecutive adult-to-adult left lobe LDLT cases without splenectomy or a portocaval shunt. The mean actual graft volume (GV)/recipient standard liver volume (SLV) ratio was 39.8% ± 5.7% (median = 38.9%, range = 26.1%-54.0%). The actual GV/SLV ratio was less than 40% in 24 of the 42 cases, and the actual graft-to-recipient weight ratio was less than 0.8% in 17 of the 42 recipients. The mean portal vein pressure (PVP) was 23.9 ± 7.6 mm Hg (median = 23.5 mm Hg, range = 9-38 mm Hg) before transplantation and 21.5 ± 3.6 mm Hg (median = 22 mm Hg, range = 14-27 mm Hg) after graft implantation. The mean portal pressure gradient (PVP - central venous pressure) was 14.5 ± 6.8 mm Hg (median = 13.5 mm Hg, range = 3-26 mm Hg) before transplantation and 12.4 ± 4.4 mm Hg (median = 13 mm Hg, range = 1-21 mm Hg) after graft implantation. The mean posttransplant portal vein flow was 301 ± 167 mL/minute/100 g of liver in the 38 recipients for whom it was measured. None of the recipients developed small-for-size syndrome, and all were discharged from the hospital despite portal hyperperfusion. The overall 1-, 3-, and 5-year patient and graft survival rates were 100%, 97%, and 91%, respectively. In conclusion, LDLT with a left liver graft without splenectomy or a portocaval shunt yields good long-term results for adult patients with a minimal donor burden.

Left-sided grafts for living-donor liver transplantation and split grafts for deceased-donor liver transplantation: their impact on long-term survival

BACKGROUND

A small-for-size graft is important in living-donor liver transplantation (LDLT) and deceased-donor liver transplantation (DDLT).

SUBJECTS AND METHODS

First, we confirmed the effect of initial graft volume on survival using a rat model of liver transplantation (LT). We then evaluated the actual long-term survival based on graft type in 1421 LTs (including 1364 LDLTs) at Kyoto University and 2000 DDLTs at the Mayo Clinic, to evaluate donor safety in LDLT and the possibility of shifting to split orthotopic liver transplantation (SOLT) in DDLT.

RESULTS

In the rat model, SOLTs with 40%- and 20%-grafts had a poor survival. A total of 697 pediatric LTs showed good long-term outcomes (survival rate was 0.764 at 21.2 years). The survival rate of 724 adult LTs was 0.664 at 17.8 years. The survival rates of auxiliary partial orthotopic liver transplantation with a left-sided graft (0.421 at 15.0 years) and SOLT with a left-sided graft (0.000 at 0.8 years) need to be improved. Although the survival rate of 1965 adult DDLTs with a whole-liver graft in the Mayo Clinic was 0.727 at 12.8 years, that of adult SOLT was 0.595 at 11.0 years.

CONCLUSION

From the viewpoint of greater donor safety and expanded donor candidates in LDLT, the choice of a left-sided graft still remains controversial. A shift to SOLT to achieve excellent results should be established to resolve a donor shortage in DDLT.

Modulation of graft vascular inflow guided by flowmetry and manometry in liver transplantation

BACKGROUND

Survival of the partial graft after living donor liver transplantation owes much to its tremendous regenerative ability. With excellent venous outflow capacity, a graft within a wide range of graft-to-standard-liver-volume ratios can cope with portal hypertension that is common in liver transplant recipients. However, when the ratio range is exceeded, modulation of graft vascular inflow becomes necessary for graft survival. The interplay between graft-to-standard-liver-volume ratio and portal pressure, in the presence of portosystemic shunt or otherwise, requires individualized modulation of graft portal and arterial inflows. Boosting of portal inflow by shunt ligation can be guided by transonic flowmetry, whereas muting of portal inflow by splenic artery ligation can be monitored by portal electronic manometry.

METHOD

We describe four cases to illustrate the above.

RESULTS

One patient had hepatic artery thrombosis resulting from splenic artery steal syndrome which was the sequela of small-for-size syndrome. Emergency splenic artery ligation and re-anastomosis of the hepatic artery successfully muted the portal inflow and boosted the hepatic arterial inflow. Another patient with portal vein thrombosis underwent thrombendvenectomy. Portal inflow was boosted with ligation of portosystemic shunt, which is often present in these patients with portal hypertension. The coexistence of splenic aneurysm and splenorenal shunt required ligation of both in the third patient. The fourth patient, with portal pressure and flow monitoring, avoided ligation of a coronary vein which became a main portal inflow after portal thrombendvenectomy.

CONCLUSION

Management of graft inflow modulation guided selectively by transonic flowmetry or portal manometry was described.

Role of hepatic stellate cells on graft injury after small-for-size liver transplantation

BACKGROUND AND AIM

Small-for-size grafts are prone to mechanical injury and a series of chemical injuries that are related to hemodynamic force. Hepatic stellate cells activate and trans-differentiate into contractile myofibroblast-like cells during liver injury. However, the role of hepatic stellate cells on sinusoidal microcirculation is unknown with small-for-size grafts.

METHODS

Thirty-five percent of small-for-size liver transplantation was performed with rats as donors and recipients. Endothelin-1 levels as well as hepatic stellate cells activation-related protein expression, endothelin-1 receptors, and ultrastructural changes were examined. The cellular localizations of two types of endothelin-1 receptors were detected. Furthermore, liver function and sinusoidal microcirculation were analyzed using two different selective antagonists of endothelin-1 receptor.

RESULTS

Intragraft expression of hepatic stellate cells activation-related protein such as desmin, crystallin-B and smooth muscle α-actin was upregulated as well as serum endothelin-1 levels and intragraft expression of the two endothelin receptors. The antagonist to endothelin-1 A receptor not to the endothelin-1 B receptor could attenuate microcirculatory disturbance and improve liver function.

CONCLUSIONS

Small-for-size liver transplantation displayed increased hepatic stellate cells activation and high level of endothelin-1 binding to upregulation of endothelin-1 A receptor on hepatic stellate cells, which contracted hepatic sinusoid inducing graft injury manifested as reduction of sinusoidal perfusion rate and elevation of sinusoidal blood flow.

Early effects of portal flow modulation after extended liver resection in rat

INTRODUCTION

The incidence of small-for-size-liver-syndrome after liver transplantation and extended liver resection may be reduced by portal flow modulation. However, many aspects of the small-for-size-liver-syndrome pathogenesis are still unclear. In this experimental study we evaluated the early effects of portal flow modulation after 80% hepatic resection in rats.

MATERIALS AND METHODS

Rats were randomised in: sham operation (G1), conventional hepatic resection (G2), splenectomy and hepatic resection (G3), splenic transposition followed by hepatic resection after three weeks (G4). Six hours after operation, oxygen saturation of hepatic vein blood, glutathione, and standard liver markers were measured from hepatic venous blood. Glutathione measurement and histopatological examination were performed in the remnant liver.

RESULTS

Total bilirubin and liver glutathione did not show differences between groups. Aspartate aminotransferase and alanine aminotransferase significantly increased in G2-G4 groups. Blood glutathione and oxygen saturation of hepatic vein blood were lower in G2 than in other groups. A gradient of micro-vesicular degeneration was more severe in G2 compared with G3 and G4. Apoptosis, hemorrhagic necrosis, mitochondrial damage and leucocyte adhesion were evident in G2.

CONCLUSION

The portal flow modulation induced by splenectomy or splenic transposition was effective in limiting early damage after extended liver resection.

Body surface area index predicts outcome in orthotopic liver transplantation

BACKGROUND/PURPOSE

In living donor liver transplantation (LDLT), matching of liver volume between donor and recipient is critical to the success of the procedure; mismatch can result in 'small- or large-for-size syndrome'. In orthotopic liver transplantation (OLT), matching criteria are less stringent and non-uniform. We sought to determine whether a new parameter, the ratio of donor to recipient body surface area (BSAi), is predictive of size mismatch and/or post-transplant morbidity or mortality.

METHODS

We reviewed data on 1228 OLT recipients and stratified this data according to three categories: small-for-size (BSAi <0.6), control (BSAi = 0.6-1.4), and large-for-size (BSAi >1.4) donors.

RESULTS

We found that: (1) matching of grafts at the upper and lower extremes of BSAi had significantly reduced graft survival; (2) matches with lower BSAi sustained a less severe form of intraoperative post-reperfusion syndrome, and the incidence of hepatic artery thrombosis was high postoperatively in these grafts; (3) BSAi and donor age correlated well with the severity of intraoperative post-reperfusion hypotension; and (4) small-for-size (BSAi <0.6) and large-for-size (BSAi >1.4) grafts, as well as preoperative total bilirubin, were significant risk factors for decreased graft survival.

CONCLUSION

We conclude that the BSAi can predict clinically significant size mismatch and adverse outcomes in cadaveric whole OLT.

Lack of a correlation between portal vein flow and pressure: toward a shared interpretation of hemodynamic stress governing inflow modulation in liver transplantation

The portal vein flow (PVF), portal vein pressure (PVP), and hepatic venous pressure gradient (HVPG) were prospectively assessed to explore their relationships and to better define hyperflow and portal hypertension (PHT) during liver transplantation (LT). Eighty-one LT procedures were analyzed. No correlation between PVF and PVP was observed. Increases in the central venous pressure (CVP) were transmitted to the PVP (58%, range = 25%-91%, P = 0.001). Severe PHT (HVPG ≥ 15 mm Hg) showed a significant reciprocal association with high PVF (P = 0.023) and lower graft survival (P = 0.04). According to this initial experience, an HVPG value ≥ 15 mm Hg is a promising tool for the evaluation of hemodynamic stress potentially influencing outcomes. An algorithm for graft inflow modulation based on flows, gradients, and systemic hemodynamics is provided. In conclusion, the evaluation of PHT severity with PVP could be delusive because of the influence of CVP. PVF and PVP do not correlate and should not be used individually to assess hyperflow and PHT during LT.

Temporal changes in the stiffness of the remnant liver and spleen after donor hepatectomy as assessed by acoustic radiation force impulse: A preliminary study

AIM

  Virtual touch tissue quantification (VTTQ) is an implementation of ultrasound acoustic radiation force impulse imaging that provides numerical measurements of tissue stiffness. We have evaluated the temporal changes of the remnant liver and spleen after living donor hepatectomy with special reference to the differences between right and left liver donation.

METHODS

  Nineteen living donors who received right lobectomy (small remnant liver [SRL] group; n = 7) or extended left and caudate lobectomy (large remnant liver [LRL] group; n = 12) were enrolled. They underwent measurement of liver and spleen VTTQ before and after donor surgery.

RESULTS

  Virtual touch tissue quantification of the remnant liver increased postoperatively until postoperative day (POD) 3-5, and the values in the SRL group were significantly higher than those in the LRL group at POD 3-9. The values of the spleen also increased after donor surgery and the values in the SRL group were significantly higher than those in the LRL group at POD 3-14. A significant positive correlation between postoperative maximum value of VTTQ and postoperative maximum total bilirubin levels was observed. In liver transplant recipients, there was a significant positive correlation between preoperative spleen VTTQ and the corresponding actual portal venous pressure that was measured at the time of transplant surgery.

CONCLUSION

  Stiffness of the remaining liver and spleen in the smaller remnant liver group became harder than that in the larger remnant liver group. Perioperative measurement of liver and spleen VTTQ seems to be a useful means for assessing the physiology of liver regeneration.

Splenectomy improves survival by increasing arterial blood supply in a rat model of reduced-size liver

Prevention of acute portal hyperperfusion in small-for-size livers by inflow modulation results in beneficial postoperative outcome. The objective of this study was to unravel the underlying mechanism, emphasizing the intimate relationship between portal venous (PV) and hepatic arterial (HA) blood flow (BF). Rats underwent partial hepatectomy (pHx), splenectomy before pHx or splenectomy and ligation of the A. hepatica before pHx. Portal venous blood flow (PVBF), hepatic arterial blood flow (HABF), and tissue pO₂ were assessed during stepwise resection from 30% to 90%. Hepatic regeneration and hypoxia-responsive gene expression were analyzed in each group after nonlethal 85% pHx. 90% pHx caused a fourfold rise in PVBF, a slight decrease in HABF with a 50% reduction in pO₂, and high mortality. Splenectomy before pHx reduced the PVBF and caused a rise in HABF with doubling in tissue pO₂. An attenuation of hypoxia-responsive gene expression turned into enhanced hepatocellular regeneration and improved survival. A. hepatica ligation abolished the beneficial effect of splenectomy on tissue oxygenation, proliferation, and outcome. In conclusion, the beneficial effect of splenectomy in small-for-size livers can be attributed to a rise in HABF with sufficient oxygen supply rather than to a reduced portal venous hyperperfusion to the remnant liver.

Portal inflow and pressure changes in right liver living donor liver transplantation including the middle hepatic vein

The middle hepatic vein may be included in right liver living donor liver transplantation (LDLT) to optimize hepatic venous outflow. We studied the graft's ability to relieve portal hypertension and accommodate portal hyperperfusion with portal manometry and ultrasonic flowmetry. Surgical outcomes with respect to portal hemodynamometry were also investigated. The ages of the recipients and donors for 46 consecutive LDLT procedures were 50 (range, 16-66 years) and 31 years (range, 18-54 years), respectively. The graft to standard liver volume ratio was 47.4% (range, 32.4%-69.0%). The hospital mortality rate was 4.4% as 2 recipients died from a subarachnoid hemorrhage and sepsis. The portal pressure dropped by 8 mm Hg (range, -7 to 19 mm Hg) from 23 (range, 8-37 mm Hg) to 14 mm Hg (range, 10-26 mm Hg) after graft implantation. The portal inflow positively correlated with the portal pressure before native liver hepatectomy (R(2) = 0.305, P = 0.001) and not with the graft size. The portal inflow increased from 81 mL/minute/100 g (range, 35-210 mL/minute/100 g) before donor right hepatectomy to 318 mL/minute/100 g (range, 102-754 mL/minute/100 g) after graft implantation. The graft portal inflow had a positive linear correlation with the recipient portal pressure before native liver total hepatectomy (R(2) = 0.261, P = 0.001) but not after graft implantation, and it had a negative correlation with the graft to standard liver volume ratio (R(2) = 0.247, P = 0.001). Only 1 of the graft biopsies showed moderate sinusoidal congestion. Twelve recipients had Clavien grade 2+ complications that were not related to the portal inflow and pressure or graft size. Right liver LDLT including the middle hepatic vein effectively lowered the recipient portal pressure by allowing unimpeded venous outflow.

Massive ascites after living donor liver transplantation with a right lobe graft larger than 0.8% of the recipient's body weight

BACKGROUND

There are only limited data on post-transplant ascites unrelated to small-sized grafts in living donor liver transplantation (LDLT).

METHODS

The subjects were 59 adult patients who had received right lobe LDLT with a graft weight-to-recipient weight ratio (GRWR)>0.8%. Patients were divided into either Group 1 (n=14, massive ascites, defined as the production of ascitic fluid>1000 mL/d that lasted longer than 14 d after LDLT) or Group 2 (n=45, no development of massive ascites). Patients were followed for a median period of 3.0 yr (range, 0.5-7.5 yr).

RESULTS

Group 1 had both higher Model for End-Stage Liver Disease score and Child-Pugh score than Group 2. Portal venous flow volume just after reperfusion was significantly greater in Group 1 than Group 2 (307.8±268.8 vs. 176.2±75.0 mL/min/100 g graft weight, respectively; p<0.05). Post-transplant infectious complications including ascites infection developed more frequently within the first post-transplant month in Group 1. Massive ascites was significantly associated with early graft loss (p<0.05).

CONCLUSION

Post-transplant massive ascites associated with portal over-perfusion into the graft liver can develop in patients with a GRWR over 0.8%. Recipients with post-transplant massive ascites require careful management to prevent infection.

Regulation of hepatic blood flow: The hepatic arterial buffer response revisited

The interest in the liver dates back to ancient times when it was considered to be the seat of life processes. The liver is indeed essential to life, not only due to its complex functions in biosynthesis, metabolism and clearance, but also its dramatic role as the blood volume reservoir. Among parenchymal organs, blood flow to the liver is unique due to the dual supply from the portal vein and the hepatic artery. Knowledge of the mutual communication of both the hepatic artery and the portal vein is essential to understand hepatic physiology and pathophysiology. To distinguish the individual importance of each of these inflows in normal and abnormal states is still a challenging task and the subject of ongoing research. A central mechanism that controls and allows constancy of hepatic blood flow is the hepatic arterial buffer response. The current paper reviews the relevance of this intimate hepatic blood flow regulatory system in health and disease. We exclusively focus on the endogenous interrelationship between the hepatic arterial and portal venous inflow circuits in liver resection and transplantation, as well as inflammatory and chronic liver diseases. We do not consider the hepatic microvascular anatomy, as this has been the subject of another recent review.

Small for size syndrome following living donor and split liver transplantation

The field of liver transplantation is limited by the availability of donor organs. The use of living donor and split cadaveric grafts is one potential method of expanding the donor pool. However, primary graft dysfunction can result from the use of partial livers despite the absence of other causes such as vascular obstruction or sepsis. This increasingly recognised phenomenon is termed “Small-for-size syndrome” (SFSS). Studies in animal models and humans have suggested portal hyperperfusion of the graft combined with poor venous outflow and reduced arterial flow might cause sinusoidal congestion and endothelial dysfunction. Graft related factors such as graft to recipient body weight ratio < 0.8, impaired venous outflow, steatosis > 30% and prolonged warm/cold ischemia time are positively predictive of SFSS. Donor related factors include deranged liver function tests and prolonged intensive care unit stay greater than five days. Child-Pugh grade C recipients are at relatively greater risk of developing SFSS. Surgical approaches to prevent SFSS fall into two categories: those targeting portal hyperperfusion by reducing inflow to the graft, including splenic artery modulation and portacaval shunts; and those aiming to relieve parenchymal congestion. This review aims to examine the controversial diagnosis of SFSS, including current strategies to predict and prevent its occurrence. We will also consider whether such interventions could jeopardize the graft by compromising regeneration.

Effects of low central venous pressure during preanhepatic phase on blood loss and liver and renal function in liver transplantation

BACKGROUND

Although the low central venous pressure (LCVP) technique is used to decrease blood loss during liver resection, its efficacy and safety during transplant procedures are still debatable. Our study aimed to assess the effects of this technique and its clinical safety for recipients undergoing liver transplantation.

METHODS

Eighty-six adult patients were randomly divided into a LCVP group and a control group. In the LCVP group, CVP was maintained below 5 mmHg or 40% lower than baseline during the preanhepatic phase by limiting infusion volume, manipulating the patient's posture, and administration of somatostatin and nitroglycerine. Recipients in the control group received standard care. Hemodynamics, blood loss, liver function, and renal function of the two groups were compared perioperatively.

RESULTS

A lower CVP was maintained in the LCVP group during the preanhepatic phase, resulting in a significant decrease in blood loss (1922 +/- 1429 vs. 3111 +/- 1833 ml, P < 0.05) and transfusion volume (1200 +/- 800 vs. 2400 +/- 1200 ml, P < 0.05) intraoperatively. Compared with the control group, the LCVP group had a significantly lower mean arterial pressure at 2 h after the start of the operation (74 +/- 11 vs. 84 +/- 14 mmHg, P < 0.05), a lower lactate value at the end of the operation (5.9 +/- 3.0 vs. 7.2 +/- 3.0 mmol/l, P < 0.05), and a better preservation of liver function after the declamping of the portal vein. There were no significant differences in perioperative renal function and postoperative complications between the groups.

CONCLUSIONS

The LCVP technique during the preanhepatic phase reduced intraoperative blood loss, protected liver function, and had no detrimental effects on renal function in LT.

Differences in portal hemodynamics between whole liver transplantation and living donor liver transplantation

The aim of this study was to investigate the differences in portal hemodynamics between whole liver transplantation and living donor liver transplantation (LDLT). Twenty patients who underwent LDLT (the L group) and 42 patients who underwent whole liver transplantation (the W group) were enrolled, and colored Doppler ultrasonography was performed preoperatively and on postoperative days (PODs) 1, 3, 5, 7, 30, and 90. The changes in the portal blood flow velocity (PBV) and portal blood flow volume (PBF) were monitored. The graft and spleen sizes were measured with angiographic computed tomography, and upper endoscopy was used to measure esophageal varices on PODs 14, 30, and 90. Although the portal venous pressure (PVP) decreased after graft implantation, it was higher in the L group with a smaller graft size ratio (25.7 ± 5.1 cm H₂O for the L group and 18.5 ± 4.6 cm H₂O for the W group, P < 0.05). PBF and PBV increased in both the W and L groups on POD 1 after transplantation; however, the PBF and PBV peaks were significantly higher in the W group. The postoperative PVP and graft volume were greatly related to PBF on POD 1. Grafts in the L group regenerated rapidly after the operation, and the volume increased from 704 ± 115 to 1524 ± 281 mL as early as 1 month after transplantation. A rapid improvement in splenomegaly was observed in both groups. An improvement in esophageal varices was observed in the W group on POD 14 after transplantation, whereas no change was observed in the L group. The portal venous flow in patients with portal hypertension showed a high perfusion state after LDLT, but in contrast to whole liver transplantation, the PVP elevation after LDLT postponed the closing time of the collateral circulation and affected the recovery from splenomegaly.

Liver resection associated with mini porto-caval shunt as salvage treatment in patients with progression of hepatocellular carcinoma before liver transplantation: a case report

Tumor progression before orthotopic liver transplantation (OLT) is the main cause of dropouts from waiting lists among patients with hepatocellular carcinoma (HCC). Performing a porto-caval shunt (PCS) before parenchymal liver transection has the potential to allow an extended hepatectomy in patients with decompensated liver cirrhosis, reducing portal hyperflow and therefore the sinusoidal shear-stress on the remnant liver. We report the case of a 59-year-old man affected by hepatitis C virus (HCV)-related decompensated liver cirrhosis (Child Pugh score presentation, C-10; Model for End Stage Liver Disease score, 18) and HCC (2 lesions of 2 and 2.8 cm). The patient began the evaluation to join the OLT waiting list, but, in the 3 months required to complete the evaluation, he developed tumor progression: 3 HCC lesions, the largest 1 with a diameter of about 4.4 cm. These findings excluded transplantation criteria and the patient was referred to our center. After appropriate preoperative studies, the patient underwent a major liver resection (trisegmentectomy) after side-to-side PCS by interposition of an iliac vein graft from a cadaveric donor. The patient overcame the worsened severity of cirrhosis. After 6 months of follow-up, he developed 2 other HCC nodules. He was then included on the waiting list at our center, undergoing OLT from a cadaveric donor at 8 months after salvage treatment. At 36 months after OLT, he is alive and free from HCC recurrence. Associating a partial side-to-side PCS with hepatic resection may represent a potential salvage therapy for patients with decompensated cirrhosis and HCC progression beyond listing criteria for OLT.

Small-for-size syndrome in adult-to-adult living-related liver transplantation

Small-for-size syndrome (SFSS) in adult-to-adult living-related donor liver transplantation (LRLT) remains the greatest limiting factor for the expansion of segmental liver transplantation from either cadaveric or living donors. Portal hyperperfusion, venous pathology, and the arterial buffer response significantly contribute to clinical and histopathological manifestations of SFSS. Here, we review the technical aspects of surgical and radiological procedures developed to treat SFSS in LRLT, along with the pathophysiology of this condition.

Deceleration of regenerative response improves the outcome of rat with massive hepatectomy

Small residual liver volume after massive hepatectomy or partial liver transplantation is a major cause of subsequent liver dysfunction. We hypothesize that the abrupt regenerative response of small remnant liver is responsible for subsequent deleterious outcome. To slow down the regenerative speed, NS-398 (ERK1/2 inhibitor) or PD98059 (selective MEK inhibitor) was administered after 70% or 90% partial hepatectomy (PH). The effects of regenerative speed on liver morphology, portal pressure and survival were assessed. In the 70% PH model, NS-398 treatment suppressed the abrupt replicative response of hepatocytes during the early phase of regeneration, although liver volume on day 7 was not significantly different from that of the control group. Immunohistochemical analysis for CD31 (for sinusoids) and AGp110 (for bile canaliculi) revealed that lobular architectural disturbance was alleviated by NS-398 treatment. In the 90% PH model, administration of NS-398 or PD98059, but not hepatocyte growth factor, significantly enhanced survival. The abrupt regenerative response of small remnant liver is suggested to be responsible for intensive lobular derangement and subsequent liver dysfunction. The suppression of MEK/ERK signaling pathway during the early phase after hepatectomy makes the regenerative response linear, and improves the prognosis for animals bearing a small remnant liver.

Portal pressure <15 mm Hg is a key for successful adult living donor liver transplantation utilizing smaller grafts than before

To prevent small-for-size syndrome in adult-to-adult living donor liver transplantation (A-LDLT), larger grafts (ie, right lobe grafts) have been selected in many transplant centers. However, some centers are investigating the benefits of portal pressure modulation. Five hundred sixty-six A-LDLT procedures using right or left lobe grafts were performed between 1998 and 2008. In 2006, we introduced intentional portal pressure control, and we changed the graft selection criteria to include a graft/recipient weight ratio >0.7% instead of the original value of >0.8%. All recipients were divided into period I (1998-2006, the era of unintentional portal pressure control; n = 432) and period II (2006-2008, the era of intentional portal pressure control; n = 134). The selection of small-for-size grafts increased from 7.8% to 23.9%, and the selection of left lobe grafts increased from 4.9% to 32.1%. Despite the increase in the number of smaller grafts in period II, 1-year patient survival was significantly improved (87.9% versus 76.2%). In 129 recipients in period II, portal pressure was monitored. Patients with a portal pressure <15 mm Hg demonstrated better 2-year survival (n = 86, 93.0%) than patients with a portal pressure >or=15 mm Hg (n = 43, 66.3%). The recovery from hyperbilirubinemia and coagulopathy after transplantation was significantly better in patients with a portal pressure <15 mm Hg. In conclusion, our strategy for A-LDLT has changed from larger graft-based A-LDLT to controlled portal pressure-based A-LDLT with smaller grafts. A portal pressure <15 mm Hg seems to be a key for successful A-LDLT.

Left lobe adult-to-adult living donor liver transplantation: small grafts and hemiportocaval shunts in the prevention of small-for-size syndrome

Adult-to-adult living donor liver transplantation (AA-LDLT) has better outcomes when a graft weight to recipient weight ratio (GW/RW) > 0.8 is selected. A smaller GW/RW may result in small-for-size syndrome (SFSS). Portal inflow modulation seems to effectively prevent SFSS. Donor right hepatectomy is associated with greater morbidity and mortality than left hepatectomy. In an attempt to shift the risk away from the donor, we postulated that left lobe grafts with a GW/RW < 0.8 could be safely used with the construction of a hemiportocaval shunt (HPCS). We combined data from 2 centers and selected suitable left lobe living donor/recipient pairs. Since January 2005, 21 patients underwent AA-LDLT with left lobe grafts. Sixteen patients underwent the creation of an HPCS between the right portal vein and the inferior vena cava. The portocaval gradient (portal pressure - central venous pressure) was measured before the unclamping of the shunt and 10 minutes after unclamping. The median actual graft weight was 413 g (range = 350-670 g), and the median GW/RW was 0.67 (range = 0.5-1.0). The portocaval gradient was reduced from a median of 18 to 5 mmHg. Patient survival and graft survival at 1 year were 87% and 81%, respectively. SFSS developed in 1 patient, who required retransplantation. Two patients died at 3 and 10 months from a bile leak and fungal sepsis, respectively. The median recipient bilirubin level and INR were 1.7 mg/dL and 1.1, respectively, at 4 weeks post-transplant. One donor had a bile leak (cut surface). This is the first US series of small left lobe AA-LDLT demonstrating that the transplantation of small grafts with modulation of the portal inflow by the creation of an HPCS may prevent the development of SFSS while at the same time providing adequate liver volume. As it matures, this technique has the potential for widespread application and could positively effect donor safety, the donor pool, and waiting list times.

Over-expression of Toll-like receptors and their ligands in small-for-size graft

AIM

Toll-like receptors (TLRs) participate in several physiological and pathological processes of transplantation, including inflammation and allograft rejection, but the expression of TLRs and their ligands remains undetermined in small-for-size graft transplantation.

METHODS

A non-arterialized partial liver transplantation model was used. The expression of TLR2 and TLR4 mRNA and protein, CD14 and Myeloid Differentiation-2 (MD-2) mRNA, as well as TLR2 and TLR4 exogenous ligands (endotoxin) and endogenous ligands [heat shock protein (HSP) 60 and 70] were assessed. The signaling pathways induced by TLR2 and TLR4 were also assessed.

RESULTS

In small-for-size liver graft, the expression of mRNA and protein of TLR2 and TLR4, CD14 and MD-2 mRNA, as well as endogenous ligands of TLR2 and TLR4 such as HSP60 and HSP70 was quickly and significantly increased after reperfusion, and reached a peak at 3 h after reperfusion. The levels of exogenous ligands (endotoxin) were increased and reached a peak at 6 h after reperfusion. The appearance of TLR2 and TLR4 mRNA was accompanied by increased HSP 60 and 70 mRNA within 24 h after reperfusion. In the small-for-size group, the peak levels of TLRs and their endogenous ligands appeared earlier than those in the full size group; the peak levels of TLRs and their endogenous and exogenous ligands were higher than those in the full size group.

CONCLUSION

TLR2 and TLR4, as well as their endogenous and exogenous ligands were activated in small-for-size liver graft transplantation.

Inhibition of matrix metalloproteinase-9 attenuates acute small-for-size liver graft injury in rats

Ischemia/reperfusion (I/R) and portal hypertension have been implicated in small-for-size liver graft dysfunction. Matrix metalloproteinases-2 and -9 (MMP-2/9) are critically proposed to involve in hepatic I/R injury and activated by hemodynamic force. We hypothesized that MMP-2/9 overexpression played a crucial role in acute graft injury following small-for-size liver transplantation (LT). Rats were randomly assigned into four groups: 75% partial hepatectomy (PH); 100% LT; 25% LT and 25% LT treated with CTT peptide (MMP-2/9 inhibitor). ELISA, real-time PCR, gelatin zymography and immunohistochemistry were used to determine the expression pattern of MMP-2/9 in liver tissue. MMP-9 expression was significantly increased 6 h after reperfusion and reached a peak 12 h in the 25% LT group, whereas MMP-2 was expressed in all groups invariably. Compared with the 25% LT group, rats from CTT-treated group exhibited markedly decreased alanine aminotransferase and total bilirubin values, downregulated proinflammatory cytokines, attenuated malondialdehyde (MDA) and myeloperoxidase (MPO) activities, and improved liver histology. Likewise, MMP-9 inhibition significantly reduced number of TUNEL-positive cells and caspase-3 activity, along with decreased protein levels of Fas and Fas-L. Specifically, rat survival was also improved in the CTT-treated group. These results support critical function of MMP-9 involved in acute small-for-size livergraft injury.