Sinusoidal endothelial cell repopulation following ischemia/reperfusion injury in rat liver transplantation

SENP1 attenuates hypoxia‑reoxygenation injury in liver sinusoid endothelial cells by relying on the HIF‑1α signaling pathway

Liver sinusoidal endothelial cells (LSECs) have an important role in hepatic ischemia‑reperfusion injury (I/R), but the specific molecular mechanism of action is unknown. LSEC proliferation is regulated and fenestration is maintained via the Sentrin/SUMO‑specific protease 1 (SENP1)/hypoxia‑inducible factor‑1α (HIF‑1α) signaling axis under hypoxic conditions. In the present study, a hypoxia‑reoxygenation (H‑R) injury model was established using mouse LSECs to explore the relationship between SENP1 and H‑R injury in vitro, and the specific underlying mechanism was identified, revealing new targets for the clinical attenuation of hepatic I/R injury. Following the culture of LSECs under H‑R conditions, it was demonstrated that the expression of SENP1 was upregulated by reverse transcription‑quantitative polymerase chain reaction and western blotting (WB). In addition, scanning electron microscopy indicated that fenestrae damage was increased, a Cell Counting Kit‑8 assay demonstrated that the proliferation of cells was impaired and flow cytometry showed that apoptosis was increased. After silencing SENP1 expression with short interfering RNA, the proliferation activity of LSECs decreased, the fenestrae damage increased, the apoptosis rate increased and the expression levels of SENP1, HIF‑1α, heme oxygenase and Bcl‑2 were downregulated (as demonstrated by WB), while the expression levels of apoptosis‑related proteins, cleaved‑caspase‑3 and Bax, were upregulated. Enzyme‑linked immunosorbent assay detection showed that the level of vascular endothelial growth factor in the supernatant decreased and the level of IL‑6 and TNF‑α increased. Following the administration of an HIF‑1α signaling pathway agonist, the situation was reversed. These results therefore suggested that SENP1 attenuated the reduction in proliferation, apoptosis and fenestration of LSECs observed following H‑R injury through the HIF‑1α signaling pathway. In conclusion, SENP1 may attenuate H‑R injury in LSECs in a HIF‑1α signaling pathway‑dependent manner.

Ghrelin protects against ischemia/reperfusion-induced hepatic injury via inhibiting Caspase-11-mediated noncanonical pyroptosis

BACKGROUND

Ischemia/reperfusion (I/R) injury is a complication of liver transplantation. I/R-induced inflammatory cell death, namely, pyroptosis, that is triggered by overactive inflammasomes results in the production of proinflammatory cytokines. Hepatic I/R injury correlates with the activation of the Caspase-11-mediated pyroptosis pathway. We investigated whether ghrelin, which is a pleiotropic gut hormone, may have anti-hepatic I/R injury effects, but the mechanism by which Ghrelin ameliorates hepatic I/R -induced injury remains a mystery.

METHODS

Hepatic I/R injury was induced in a mouse model by clamping the left and right lobes of the liver for 90 min followed by reperfusion for 6 h, 12 h, or 24 h. As treatment, a saline with or without ghrelin was infused via the tail vain. Hepatocytes were isolated using a two-step collagenase liver perfusion method.

RESULTS

In our study, treatment with ghrelin protected against hepatic I/R injury as shown by decreased alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels (p < 0.001) and reduced the histological injury in liver tissues compared with untreated controls. The LDH level of primary hepatocytes was increased by hypoxia/reoxygenation (H/R), and it was then restored to normal levels by ghrelin-treatment (p < 0.05). Western blotting analysis showed that ghrelin significantly inhibited the expression of pyroptosis-related proteins, including Caspase-11, GSDMD-N, NLRP3 and HMGB1, both in vivo and in vitro (all p < 0.05) compared with the untreated controls. Immunofluorescence showed that the expression of Gasdamin D (GSDMD) in hepatocytes was increased after I/R or H/R, whereas GSDMD expression was reduced by ghrelin treatment (p < 0.05).

CONCLUSIONS

Our findings suggest that ghrelin ameliorated I/R-induced hepatic injury by inhibiting Caspase-11-mediated pyroptosis. Ghrelin may be a potential therapeutic option to prevent hepatic I/R injury after liver transplantation.

The role of liver sinusoidal endothelial cells in liver remodeling after injury

Liver transplantation is the optimal treatment for patients with end-stage liver disease, metabolic liver diseases, and hepatic malignancies that are not amenable to resection. Hepatic ischemia-reperfusion injury (IRI) is the main problem in liver transplantation and liver resection, leading to parenchymal cell injury and organ dysfunction. The damage of liver sinusoidal endothelial cells (LSECs) is a critical event in IRI. LSECs work as an important regulating factor of liver regeneration after partial hepatectomy. This review primarily describes the mechanisms of LSECs injury in IRI and explores the roles of LSECs in liver regeneration, and briefly introduces the protective strategies targeting LSECs damaged in IRI.

Preclinical Application of Reduced Manipulated Processing Strategy to Collect Transplantable Hepatocytes: A Pilot and Feasibility Study

Background: The complex isolation and purification process of hepatocytes for transplantation is labor intensive and with great contamination risk. Here, as a pilot and feasibility study, we examined in vitro and in vivo hepatocyte isolation feasibility and cell function of Cell Saver^® Elite^®, an intraoperative blood-cell-recovery system. Methods: Rat and pig liver cells were collected using this system and then cultured in vitro, and their hepatocyte-specific enzymes were characterized. We then transplanted the hepatocytes in an established acute liver–injured (retrorsine+D-galactosamine-treated) rat model for engraftment. Recipient rats were sacrificed 1, 2, and 4 weeks after transplantation, followed by donor-cell identification and histological, serologic, and immunohistopathological examination. To demonstrate this Cell Saver^® strategy is workable in the first place, traditional (classical) strategy, in our study, behaved as certainty during the cell manufacturing process for monitoring quality assurance throughout the course, from the start of cell isolation to post-transplantation. Results: We noted that in situ collagenase perfusion was followed by filtration, centrifugation, and collection in the Cell Saver^® until the process ended. Most (>85%) isolated cells were hepatocytes (>80% viability) freshly demonstrating hepatocyte nuclear factor 4α and carbamoyl-phosphate synthase 1 (a key enzyme in the urea cycle), and proliferating through intercellular contact in culture, with expression of albumin and CYP3A4. After hepatocyte transplantation in dipeptidyl peptidase IV (−/−) rat liver, wild-type donor hepatocytes engrafted and repopulated progressively in 4 weeks with liver functional improvement. Proliferating donor hepatocyte–native biliary ductular cell interaction was identified. Post-transplantation global liver functional recovery after Cell Saver and traditional methods was comparable. Conclusions: Cell Saver^® requires reduced manual manipulation for isolating transplantable hepatocytes.

Hypothermic oxygenated perfusion inhibits HECTD3-mediated TRAF3 polyubiquitination to alleviate DCD liver ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is an inevitable and serious clinical problem in donations after heart death (DCD) liver transplantation. Excessive sterile inflammation plays a fateful role in liver IRI. Hypothermic oxygenated perfusion (HOPE), as an emerging organ preservation technology, has a better preservation effect than cold storage (CS) for reducing liver IRI, in which regulating inflammation is one of the main mechanisms. HECTD3, a new E3 ubiquitin ligase, and TRAF3 have an essential role in inflammation. However, little is known about HECTD3 and TRAF3 in HOPE-regulated liver IRI. Here, we aimed to investigate the effects of HOPE on liver IRI in a DCD rat model and explore the roles of HECTD3 and TRAF3 in its pathogenesis. We found that HOPE significantly improved liver damage, including hepatocyte and liver sinusoidal endothelial cell injury, and reduced DCD liver inflammation. Mechanistically, both the DOC and HECT domains of HECTD3 directly interacted with TRAF3, and the catalytic Cys (C832) in the HECT domain promoted the K63-linked polyubiquitination of TRAF3 at Lys138. Further, the ubiquitinated TRAF3 at Lys138 increased oxidative stress and activated the NF-κB inflammation pathway to induce liver IRI in BRL-3A cells under hypoxia/reoxygenation conditions. Finally, we confirmed that the expression of HECTD3 and TRAF3 was obviously increased in human DCD liver transplantation specimens. Overall, these findings demonstrated that HOPE can protect against DCD liver transplantation-induced-liver IRI by reducing inflammation via HECTD3-mediated TRAF3 K63-linked polyubiquitination. Therefore, HOPE regulating the HECTD3/TRAF3 pathway is a novel target for improving IRI in DCD liver transplantation.

Detection of early allograft dysfunction at 30 min of reperfusion in liver transplantation: An intraoperative diagnostic tool with real time assessment of graft function

INTRODUCTION

During the anhepatic phase of liver transplantation (LT), fibrinolytic activity increases, since the liver clears tissue plasminogen activator (tPA). We hypothesize that patients who fail to reduce fibrinolytic activity following graft reperfusion will have an increased rate of early allograft dysfunction (EAD).

METHODS

Assessment of fibrinolysis in liver transplant recipients was quantified with thrombelastography (TEG) LY30. Changes in LY30 were assessed after graft reperfusion. The 30-min post-reperfusion LY30 was subtracted from the anhepatic LY30 quantifying fibrinolytic changes (delta-LY30).

RESULTS

Seventy-three primary LT patients were included in the analysis. Receiver operating characteristic curve (ROC) analysis identified an inflection point of delta-LY30-5.3% as a risk factor for EAD. EAD occurred in 44% of these patients compared to 5% in high delta-LY30 (p = 0.002).

CONCLUSION

LT recipients that develop hyperfibrinolysis who fail to reduce fibrinolytic activity 30 min after graft reperfusion had an EAD rate 8-fold higher than patients who had a large reduction in LY30 following reperfusion.

Cell release during perfusion reflects cold ischemic injury in rat livers

The global shortage of donor organs has made it crucial to deeply understand and better predict donor liver viability. However, biomarkers that effectively assess viability of marginal grafts for organ transplantation are currently lacking. Here, we showed that hepatocytes, sinusoidal endothelial, stellate, and liver-specific immune cells were released into perfusates from Lewis rat livers as a result of cold ischemia and machine perfusion. Perfusate comparison analysis of fresh livers and cold ischemic livers showed that the released cell profiles were significantly altered by the duration of cold ischemia. Our findings show for the first time that parenchymal cells are released from organs under non-proliferative pathological conditions, correlating with the degree of ischemic injury. Thus, perfusate cell profiles could serve as potential biomarkers of graft viability and indicators of specific injury mechanisms during organ handling and transplantation. Further, parenchymal cell release may have applications in other pathological conditions beyond organ transplantation.

Ischaemia-reperfusion injury with Pringle's maneuver induces unusually large von Willebrand factor multimers after hepatectomy

INTRODUCTION

von Willebrand factor (VWF) is synthesised in vascular endothelial cells and released into the plasma as unusually large VWF multimers (UL-VWFMs). Sinusoidal endothelial cells are a major target of ischaemia-reperfusion injury due to liver surgery. This study aimed to clarify the effect of hepatectomy on UL-VWFMs.

MATERIALS AND METHODS

Thirty-five patients who underwent hepatectomy were eligible for the study. Plasma ADAMTS13 activity and VWF antigen levels were measured by enzyme-linked immunosorbent assay and multimer analysis of plasma VWF was performed according to Ruggeri and Zimmerman's method. For analyses, patients were categorised according to UL-VWFM positivity after hepatectomy.

RESULTS

Plasma ADAMTS13 activity significantly decreased from 61.0% (27.7%-126.2%) before operation to 37.4% (20.2%-71.4%) on postoperative day 7 (p < 0.001). Plasma VWF antigen levels significantly increased from 172.1% (80.5%-412.8%) before operation to 361.0% (154.7%-745.8%) on postoperative day 2, which remained high until postoperative day 7 (p < 0.001). Seven patients remained UL-VWFMs-negative and 22 patients became UL-VWFMs-positive after operation. Pringle's maneuver duration was significantly longer and blood loss volume was significantly higher in the UL-VWFMs-positive group (p = 0.001 and p = 0.003, respectively). By multivariable analysis, Pringle's maneuver duration [odds ratio 1.049, 95% confidence interval (CI) 1.001-1.098; p = 0.043] was significantly associated with increased UL-VWFMs level after hepatectomy. UL-VWFMs index was significantly correlated with Pringle's maneuver duration (r = 0.444, p = 0.017).

CONCLUSIONS

Plasma UL-VWFMs levels increased after hepatectomy due to ischaemia-reperfusion injury with Pringle's maneuver.

Overexpression of the long noncoding RNA TUG1 protects against cold-induced injury of mouse livers by inhibiting apoptosis and inflammation

Hepatic injury provoked by cold storage is a major problem affecting liver transplantation, as exposure to cold induces apoptosis in hepatic tissues. Long noncoding RNAs (lncRNAs) are increasingly understood to regulate apoptosis, but the contribution of lncRNAs to cold-induced liver injury remains unknown. Using RNA-seq, we determined the differential lncRNA expression profile in mouse livers after cold storage and found that expression of the lncRNA TUG1 was significantly down-regulated. Overexpression of TUG1 attenuated cold-induced apoptosis in mouse hepatocytes and liver sinusoidal endothelial cells LSECs, in part by blocking mitochondrial apoptosis and endoplasmic reticulum (ER) stress pathways. Moreover, TUG1 attenuated apoptosis, inflammation, and oxidative stress in vivo in livers subjected to cold storage. Overexpression of TUG1 also improved hepatocyte function and prolonged hepatic graft survival rates in mice. These results suggest that the lncRNA TUG1 exerts a protective effect against cold-induced liver damage by inhibiting apoptosis in mice, and suggests a potential role for TUG1 as a target for the prevention of cold-induced liver damage in liver transplantation.

DATABASES

RNA-seq data are available from GEO using accession number GSE76609.

Novel strategy to decrease reperfusion injuries and improve function of cold-preserved livers using normothermic ex vivo liver perfusion machine

Normothermic extracorporeal liver perfusion (NELP) can decrease ischemia/reperfusion injury to the greatest degree when cold ischemia time is minimized. Warm perfusion of cold-stored livers results in hepatocellular damage, sinusoidal endothelial cell (SEC) dysfunction, and Kupffer cell activation. However, the logistics of organ procurement mandates a period of cold preservation before NELP. The aim of this study was to determine the beneficial effects of gradual rewarming of cold-stored livers by placement on NELP. Three female porcine livers were used for each group. In the immediate NELP group, procured livers were immediately placed on NELP for 8 hours. In the cold NELP group, livers were cold-stored for 4 hours followed by NELP for 4 hours. In rewarming groups, livers were cold-stored for 4 hours, then gradually rewarmed in different durations to 38°C and kept on NELP for an additional 4 hours. For comparison purposes, the last 4 hours of NELP runs were considered to be the evaluation phase. Immediate NELP livers had significantly lower concentrations of liver transaminases, hyaluronic acid, and β-galactosidase and had higher bile production compared to the other groups. Rewarming livers had significantly lower concentrations of hyaluronic acid and β-galactosidase compared to the cold NELP livers. In addition, there was a significant decline in international normalized ratio values, improved bile production, reduced biliary epithelial cell damage, and improved cholangiocyte function. Thus, if a NELP machine is not available at the procurement site and livers will need to undergo a period of cold preservation, a gradual rewarming protocol before NELP may greatly reduce damages that are associated with reperfusion. In conclusion, gradual rewarming of cold-preserved livers upon NELP can minimize the hepatocellular damage, Kupffer cell activation, and SEC dysfunction.

Molecular pathways in protecting the liver from ischaemia/reperfusion injury: a 2015 update

Ischaemia/reperfusion injury is an important cause of liver damage during surgical procedures such as hepatic resection and liver transplantation, and represents the main cause of graft dysfunction post-transplantation. Molecular processes occurring during hepatic ischaemia/reperfusion are diverse, and continuously include new and complex mechanisms. The present review aims to summarize the newest concepts and hypotheses regarding the pathophysiology of liver ischaemia/reperfusion, making clear distinction between situations of cold and warm ischaemia. Moreover, the most updated therapeutic strategies including pharmacological, genetic and surgical interventions, as well as some of the scientific controversies in the field are described.

Pretransplant replacement of donor liver grafts with recipient Kupffer cells attenuates liver graft rejection in rats

BACKGROUND AND AIM

Rejection of liver grafts is a difficult issue that has not been resolved. Preoperative replacement of liver cells in the graft with cells from the intended recipient may attenuate rejection. We investigated whether preoperative transplant of recipient bone marrow cells (BMCs) to the donor replaced liver allograft cells and attenuated rejection.

METHODS

We used a rat model of allogeneic liver transplant (LT) from Dark Agouti (DA) to Lewis (LEW) rats. In BMC group, DA rats received BMC transplants from LacZ-transgenic LEW rats at 1 week before LT. In the control group, DA rats received no preoperative treatment. We evaluated graft damage at 7 days after LT and the survival of the recipient rats.

RESULTS

Rats in the BMC group experienced prolonged survival that was abrogated by the administration of gadolinium chloride to donors at 24 h before LT. Serum concentrations of total bilirubin and hyaluronic acid on day 7 were significantly lower in the BMC group, and histopathological analyses revealed that rejection of the liver graft was attenuated. X-gal staining and immunohistostaining of the liver graft revealed that BMCs engrafted in the sinusoidal space differentiated into Kupffer cells.

CONCLUSIONS

Preoperative transplant of recipient BMCs to LT donors replaced donor Kupffer cells and attenuated post-LT rejection, indicating that this strategy may increase the success of LT.

Effects of Institut Georges Lopez-1 and Celsior preservation solutions on liver graft injury

AIM: To compare Institut Georges Lopez (IGL-1) and Celsior preservation solutions for hepatic endothelium relaxation and liver cold ischemia reperfusion injury (IRI).

METHODS: Two experimental models were used. In the first one, acetylcholine-induced endothelium-dependent relaxation (EDR) was measured in isolated ring preparations of rat hepatic arteries preserved or not in IGL-1 or Celsior solutions (24 h at 4 °C). To determine nitric oxide (NO) and cyclooxygenase EDR, hepatic arteries were incubated with L-NG-nitroarginine methyl ester (L-NAME), an inhibitor of endothelium nitric oxide synthase (eNOS), or with L-NAME plus indomethacin, an inhibitor of cyclooxygenase. In the second experiment, rat livers were cold-stored in IGL-1 or Celsior solutions for 24 h at 4 °C and then perfused “ex vivo” for 2 h at 37 °C. Liver injury was assessed by transaminase measurements, liver function by bile production and bromosulfophthalein clearance, oxidative stress by malondialdehyde levels and catalase activity and alterations in cell signaling pathways by pAkt, pAMPK, eNOS and MAPKs proteins level.

RESULTS: After cold storage for 24 h with either Celsior or IGL-1, EDR was only slightly altered. In freshly isolated arteries, EDR was exclusively mediated by NO. However, cold-stored arteries showed NO- and COX-dependent relaxation. The decrease in NO-dependent relaxation after cold storage was significantly more marked with Celsior. The second study indicated that IGL-1 solution obtained better liver preservation and protection against IRI than Celsior. Liver injury was reduced, function was improved and there was less oxidative stress. IGL-1 solution activated Akt and AMPK, which was concomitant with increased eNOS expression and nitrite/nitrate levels. Furthermore, MAPKs kinases were regulated in livers preserved with IGL-1 solution since reductions in p-p38, p-ERK and p-JNK protein levels were observed.

CONCLUSION: IGL-1 solution preserved NO-dependent relaxation better than Celsior storage solution and enhanced liver graft preservation.

Ischemia-reperfusion: From cell biology to acute kidney injury

Ischemia reperfusion injury occurs in the kidney when blood supply is interrupted in clinical settings such as kidney transplantation or nephron sparing surgery for renal tumors. These lesions lead to acute kidney injury (AKI) a detrimental situation associated with impaired short-term allograft function (delayed graft function or primary non function) but also long-term transplant survival through the onset of chronic allograft nephropathy. The present review details the cellular and molecular consequences of ischemia reperfusion in a native kidney as well as in a kidney graft after cold ischemia time, giving a comprehensive description of biological pathways involved during the phase of ischemia and during the reperfusion period where the rapid return to normoxia leads to a large burst of reactive oxygen species along with a dramatic reduction in antioxidant defenses. This work also focuses on the distinct susceptibilities of kidney cells to ischemia (endothelial vs epithelial) and the outcome of acute kidney injury.

VEGFR1-positive macrophages facilitate liver repair and sinusoidal reconstruction after hepatic ischemia/reperfusion injury

Liver repair after acute liver injury is characterized by hepatocyte proliferation, removal of necrotic tissue, and restoration of hepatocellular and hepatic microvascular architecture. Macrophage recruitment is essential for liver tissue repair and recovery from injury; however, the underlying mechanisms are unclear. Signaling through vascular endothelial growth factor receptor 1 (VEGFR1) is suggested to play a role in macrophage migration and angiogenesis. The aim of the present study was to examine the role of VEGFR1 in liver repair and sinusoidal reconstruction after hepatic ischemia/reperfusion (I/R). VEGFR1 tyrosine kinase knockout mice (VEGFR1 TK-/- mice) and wild-type (WT) mice were subjected to hepatic warm I/R, and the processes of liver repair and sinusoidal reconstruction were examined. Compared with WT mice, VEGFR1 TK-/- mice exhibited delayed liver repair after hepatic I/R. VEGFR1-expressing macrophages recruited to the injured liver showed reduced expression of epidermal growth factor (EGF). VEGFR1 TK-/- mice also showed evidence of sustained sinusoidal functional and structural damage, and reduced expression of pro-angiogenic factors. Treatment of VEGFR1 TK-/- mice with EGF attenuated hepatoceullar and sinusoidal injury during hepatic I/R. VEGFR1 TK-/- bone marrow (BM) chimeric mice showed impaired liver repair and sinusoidal reconstruction, and reduced recruitment of VEGFR1-expressing macrophages to the injured liver. VEGFR1-macrophages recruited to the liver during hepatic I/R contribute to liver repair and sinusoidal reconstruction. VEGFR1 activation is a potential therapeutic strategy for promoting liver repair and sinusoidal restoration after acute liver injury.

Graft reconditioning with nitric oxide gas in rat liver transplantation from cardiac death donors

BACKGROUND

Liver transplant outcomes using grafts donated after cardiac death (DCD) remain poor.

METHODS

We investigated the effects of ex vivo reconditioning of DCD grafts with venous systemic oxygen persufflation using nitric oxide gas (VSOP-NO) in rat liver transplants. Orthotopic liver transplants were performed in Lewis rats, using DCD grafts prepared using static cold storage alone (group-control) or reconditioning using VSOP-NO during cold storage (group-VSOP-NO). Experiment I: In a 30-min warm ischemia model, graft damage and hepatic expression of inflammatory cytokines, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and endothelin-1 (ET-1) were examined, and histologic analysis was performed 2, 6, 24, and 72 hr after transplantation. Experiment II: In a 60-min warm ischemia model, grafts were evaluated 2 hr after transplantation (6 rats/group), and survival was assessed (7 rats/group).

RESULTS

Experiment I: Group-VSOP-NO had lower alanine aminotransferase (ALT) (P<0.001), hyaluronic acid (P<0.05), and malondialdehyde (MDA) (P<0.001), hepatic interleukin-6 expression (IL-6) (P<0.05), and hepatic tumor necrosis factor-alpha (TNF-α) expression (P<0.001). Hepatic eNOS expression (P<0.001) was upregulated, whereas hepatic iNOS (P<0.01) and ET-1 (P<0.001) expressions were downregulated. The damage of hepatocyte and sinusoidal endothelial cells (SECs) were lower in group-VSOP-NO.Experiment II: VSOP-NO decreased ET-1 and 8-hydroxy-2'deoxyguanosine (8-OHdG) expression and improved survival after transplantation by 71.4% (P<0.01).

CONCLUSION

These results suggest that VSOP-NO effectively reconditions warm ischemia-damaged grafts, presumably by decreasing ET-1 upregulation and oxidative damage.

Mesenchymal stem cells support hepatocyte function in engineered liver grafts

Recent studies suggest that organ decellularization is a promising approach to facilitate the clinical application of regenerative therapy by providing a platform for organ engineering. This unique strategy uses native matrices to act as a reservoir for the functional cells which may show therapeutic potential when implanted into the body. Appropriate cell sources for artificial livers have been debated for some time. The desired cell type in artificial livers is primary hepatocytes, but in addition, other supportive cells may facilitate this stem cell technology. In this context, the use of mesenchymal stem cells (MSC) is an option meeting the criteria for therapeutic organ engineering. Ideally, supportive cells are required to (1) reduce the hepatic cell mass needed in an engineered liver by enhancing hepatocyte function, (2) modulate hepatic regeneration in a paracrine fashion or by direct contact, and (3) enhance the preservability of parenchymal cells during storage. Here, we describe enhanced hepatic function achieved using a strategy of sequential infusion of cells and illustrate the advantages of co-cultivating bone marrow-derived MSCs with primary hepatocytes in the engineered whole-liver scaffold. These co-recellularized liver scaffolds colonized by MSCs and hepatocytes were transplanted into live animals. After blood flow was established, we show that expression of adhesion molecules and proangiogenic factors was upregulated in the graft.

Mesenchymal stem cell-conditioned medium reduces liver injury and enhances regeneration in reduced-size rat liver transplantation

BACKGROUND

Mesenchymal stem cell (MSC) therapy can prevent parenchymal cell loss and promotes tissue repair through the action of trophic, secreted molecules. In this study, we investigated whether MSC-conditioned medium (MSC-CM) could protect hepatocytes and sinusoidal endothelial cells (SECs) and stimulate their regeneration in 50% reduced-size liver transplantation (RSLT).

MATERIALS AND METHODS

Rats were randomly divided into three groups: sham-operated group, MSC-CM group (rats with 50% RSLT receiving MSC-CM infusion), and medium group (rats with 50% RSLT receiving medium therapy). Graft function, proinflammatory cytokines, incidence of apoptosis, proliferation of hepatocytes and SECs, and the expression of vascular endothelial growth factor and matrix metallopeptidase 9 were assessed in this study.

RESULTS

Systemic infusion of MSC-CM prevented the release of liver injury biomarkers and provided a significant survival benefit. Furthermore, MSC-CM therapy resulted in reduction of apoptosis of hepatocytes and SECs. The number of proliferating hepatocytes and SECs increased 1.2- and 1.6-fold, respectively, accompanied by a decrease in the expression levels of several proinflammatory cytokines and a noticeable decrease in infiltration of neutrophils and activation of Kupffer cells. Also, increased expression of vascular endothelial growth factor and matrix metallopeptidase 9 in the grafts was observed after MSC-CM therapy.

CONCLUSIONS

These data suggest that MSC-CM therapy in RSLT provides trophic support to the injured liver by inhibiting SEC and hepatocellular death and stimulating their regeneration.

Mesenchymal stem cells overexpressing C-X-C chemokine receptor type 4 improve early liver regeneration of small-for-size liver grafts

Mesenchymal stem cell (MSC) therapy can prevent hepatic parenchymal cell loss and promote tissue repair. However, poor MSC engraftment is one of the primary barriers to the effectiveness of cell therapy because culture-expanded MSCs progressively down-regulate C-X-C chemokine receptor type 4 (CXCR4) expression and lose their ability to migrate toward a concentration gradient of stromal cell-derived factor 1a (SDF1a). In this study, we investigated whether a CXCR4-MSC infusion could protect hepatocytes and stimulate regeneration in 50% reduced size liver transplantation (RSLT). Rats that underwent 50% RSLT were randomly divided into 3 groups: a phosphate-buffered solution group (PBS), a green fluorescent protein (GFP)-MSC group, and a CXCR4-MSC group. Rats received 1 mL of PBS with or without a resuspension of GFP-MSCs or CXCR4-MSCs. The factors secreted by MSCs, the graft function, the apoptosis and proliferation of hepatocytes, the efficacy of MSC engraftment, and the expression of SDF1α, albumin (Alb), and cytokeratin 18 (CK18) in engrafted GFP-positive MSCs were assessed. A systemic infusion of GFP-MSCs led to a reduction of the release of liver injury biomarkers and apoptosis of hepatocytes; CXCR4 overexpression did not further reduce the liver injury. However, CXCR4 overexpression enhanced MSC engraftment in liver grafts, improved the effect on the proliferation of hepatocytes, and thus provided a significant 1-week survival benefit. SDF1α expression in grafts was elevated after transplanted CXCR4-MSCs were recruited to the remnant liver. However, engrafted MSCs did not express the markers of hepatocytes, including Alb and CK18, in vivo 168 hours after transplantation. CXCR4 overexpression enhanced the mobilization and engraftment of MSCs into small-for-size liver grafts, in which these cells promoted the early regeneration of the remnant liver not by direct differentiation but perhaps by a paracrine mechanism.

Hepatic stellate cells undermine the allostimulatory function of liver myeloid dendritic cells via STAT3-dependent induction of IDO

Hepatic stellate cells (HSCs) are critical for hepatic wound repair and tissue remodeling. They also produce cytokines and chemokines that may contribute to the maintenance of hepatic immune homeostasis and the inherent tolerogenicity of the liver. The functional relationship between HSCs and the professional migratory APCs in the liver, that is, dendritic cells (DCs), has not been evaluated. In this article, we report that murine liver DCs colocalize with HSCs in vivo under normal, steady-state conditions, and cluster with HSCs in vitro. In vitro, HSCs secrete high levels of DC chemoattractants, such as MΙP-1α and MCP-1, as well as cytokines that modulate DC activation, including TNF-α, IL-6, and IL-1β. Culture of HSCs with conventional liver myeloid (m) DCs resulted in increased IL-6 and IL-10 secretion compared with that of either cell population alone. Coculture also resulted in enhanced expression of costimulatory (CD80, CD86) and coinhibitory (B7-H1) molecules on mDCs. HSC-induced mDC maturation required cell-cell contact and could be blocked, in part, by neutralizing MΙP-1α or MCP-1. HSC-induced mDC maturation was dependent on activation of STAT3 in mDCs and, in part, on HSC-secreted IL-6. Despite upregulation of costimulatory molecules, mDCs conditioned by HSCs demonstrated impaired ability to induce allogeneic T cell proliferation, which was independent of B7-H1, but dependent upon HSC-induced STAT3 activation and subsequent upregulation of IDO. In conclusion, by promoting IDO expression, HSCs may act as potent regulators of liver mDCs and function to maintain hepatic homeostasis and tolerogenicity.

Human liver endothelial cells, but not macrovascular or microvascular endothelial cells, engraft in the mouse liver

Liver cell transplantation has had limited clinical success so far, partly due to poor engraftment of hepatocytes. Instead of hepatocytes. other cell types, such as endothelial cells, could be used in ex vivo liver gene therapy. The goal of the present study was to compare the grafting and repopulation capacity of human endothelial cells derived from various tissues. Human endothelial cells were isolated from adult and fetal livers using anti-human CD31 antibody-conjugated magnetic beads. Human macrovascular endothelial cells were obtained from umbilical vein. Human microvascular endothelial cells were isolated from adipose tissue. Cells were characterized using flow cytometry. Liver engraftment and repopulation of endothelial cells was studied after intrasplenic transplantation in monocrotaline-treated immunodeficient mice. Following transplantation, human liver endothelial cells engrafted throughout the mouse liver. With immunoscanning electron microscopy, fenestrae in engrafted human liver endothelial cells were identified, a characteristic feature of liver sinusoidal endothelial cells. In contrast, CD31-negative liver cells, human macrovascular and microvascular endothelial cells were not capable of repopulating mouse liver. Characterization of human liver, macrovascular, and microvascular endothelial cells demonstrated expression of CD31, CD34, and CD146 but not CD45. Our study shows that only human liver endothelial cells, but not macro- and microvascular endothelial cells, have the unique capacity to engraft and repopulate the mouse liver. These results indicate that mature endothelial cells cannot transdifferentiate in vivo and thus do not exhibit phenotypic plasticity. Our results have set a basis for further research to the potential of human liver endothelial cells in liver-directed cell and gene therapy.

Impact of hepatic arterial reconstruction on orthotopic liver transplantation in the rat

Orthotopic liver transplantation (OLT) models in rats have been investigated in many studies, but detailed information on the impact of hepatic artery (HA) reconstruction on postoperative factors remains to be investigated. HA reconstruction also requires advanced skills. The effect of the reconstruction of the HA by a hand-suture technique in rats with a whole-liver syngeneic graft was investigated. Long-term survival, histopathological assessment, immunohistological evaluation, and blood biochemistry were investigated until postoperative day (POD) 28. From the early postoperative period, significant differences between OLTs with or without HA reconstruction were found in graft parenchymal damage, induction of apoptosis, and transaminase levels, though survival curves and the coagulation profile showed no differences. In OLT without HA reconstruction, biliary proliferation was decreased at POD 5-14, and total bilirubin level was increased at PODs 10 and 14. The study indicates that HA reconstruction is required for reliable OLT in rats.

Hepatic arterial reconstruction for orthotopic liver transplantation in the rat

BACKGROUND

Orthotopic liver transplantation (OLT) models in rats have been investigated in many studies. The reconstruction of hepatic artery is required for reliable OLT and also requires advanced skills.

METHODS

The hepatic artery reconstructions by a hand-suture technique and a new method using a micro T-tube were investigated in rats with a whole-liver syngeneic graft. Operative time and postoperative patency were compared between the hand-suture and micro T-tube techniques.

RESULTS

Our technique using the micro T-tube shortened the operative time of recipient surgery compared with the hand-suture technique and prolonged the operative time for the donor. The patency ratio was maintained at 24h after OLT with hand suturing but was significantly reduced with the micro T-tube, which had a patency ratio of 0.83 only up to 6h after OLT.

CONCLUSION

The micro T-tube technique may have potential usefulness in the rat OLT model but requires further modification.

Selective expansion of allogeneic regulatory T cells by hepatic stellate cells: role of endotoxin and implications for allograft tolerance

Hepatic stellate cells (HSCs) may play an important role in hepatic immune regulation by producing numerous cytokines/chemokines and expressing Ag-presenting and T cell coregulatory molecules. Due to disruption of the endothelial barrier during cold-ischemic storage and reperfusion of liver grafts, HSCs can interact directly with cells of the immune system. Endotoxin (LPS), levels of which increase in liver diseases and transplantation, stimulates the synthesis of many mediators by HSCs. We hypothesized that LPS-stimulated HSCs might promote hepatic tolerogenicity by influencing naturally occurring immunosuppressive CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs). Following their portal venous infusion, allogeneic CD4(+) T cells, including Tregs, were found closely associated with HSCs, and this association increased in LPS-treated livers. In vitro, both unstimulated and LPS-stimulated HSCs upregulated Fas (CD95) expression on conventional CD4(+) T cells and induced their apoptosis in a Fas/Fas ligand-dependent manner. By contrast, HSCs induced Treg proliferation, which required cell-cell contact and was MHC class II-dependent. This effect was augmented when HSCs were pretreated with LPS. LPS increased the expression of MHC class II, CD80, and CD86 and stimulated the production of IL-1α, IL-1β, IL-6, IL-10 and TNF-α by HSCs. Interestingly, production of IL-1α, IL-1β, IL-6, and TNF-α was strongly inhibited, but that of IL-10 enhanced in LPS-pretreated HSC/Treg cocultures. Adoptively transferred allogeneic HSCs migrated to the secondary lymphoid tissues and induced Treg expansion in lymph nodes. These data implicate endotoxin-stimulated HSCs as important immune regulators in liver transplantation by inducing selective expansion of tolerance-promoting Tregs and reducing inflammation and alloimmunity.

Endothelial dysfunction in the regulation of cirrhosis and portal hypertension

Portal hypertension is caused by an increased intrahepatic resistance, a major consequence of cirrhosis. Endothelial dysfunction in liver sinusoidal endothelial cells (LSECs) decreases the production of vasodilators, such as nitric oxide, and favours vasoconstriction. This contributes to an increased vascular resistance in the intrahepatic/sinusoidal microcirculation and develops portal hypertension. Portal hypertension, in turn, causes endothelial dysfunction in the extrahepatic, i.e. splanchnic and systemic, circulation. Unlike dysfunction in LSECs, endothelial dysfunction in the splanchnic and systemic circulation causes overproduction of vasodilator molecules, leading to arterial vasodilation. In addition, portal hypertension leads to the formation of portosystemic collateral vessels. Both arterial vasodilation and portosystemic collateral vessel formation exacerbate portal hypertension by increasing the blood flow through the portal vein. Pathological consequences, such as oesophageal varices and ascites, result. While the sequence of pathological vascular events in cirrhosis and portal hypertension has been elucidated, the underlying cellular and molecular mechanisms causing endothelial dysfunctions are not yet fully understood. This review article summarizes the current cellular and molecular studies on endothelial dysfunctions found during the development of cirrhosis and portal hypertension with a focus on the intra- and extrahepatic circulations. The article ends by discussing the future directions of the study for endothelial dysfunction.

Carbon monoxide induces hypothermia tolerance in Kupffer cells and attenuates liver ischemia/reperfusion injury in rats

Ischemia/reperfusion (I/R) injury in liver grafts, which is initiated by cold preservation and is augmented by reperfusion, is a major problem that complicates graft quality, posttransplant patient care, and outcomes of liver transplantation (LT). Kupffer cells (KCs) play important roles in I/R injury; however, little is known about their changes during cold preservation. We examined whether a pretreatment with carbon monoxide (CO), a cytoprotective product of heme degradation, could influence KC activity during cold storage and protect liver grafts against LT-induced I/R injury. In vitro, primary rat KCs were stimulated for 24 hours under hypothermic conditions (4°C, 20% O(2)), with lipopolysaccharide, or under hypoxic conditions (37°C, 5% O(2)) with or without a CO pretreatment. When rat KCs were exposed to hypothermic conditions, they produced reactive oxygen species (ROS), but they did not produce tumor necrosis factor α (TNF-α) or nitric oxide. The preincubation of KCs with CO up-regulated heat shock protein 70 (HSP70) and inhibited ROS generation. When liver grafts from donor rats exposed to CO (250 ppm) for 24 hours were transplanted after 18 hours of cold preservation in University of Wisconsin solution, HSP70 expression increased in these grafts versus control grafts, and serum aspartate aminotransferase and alanine aminotransferase levels as well as necrotic areas and inflammatory infiltrates were significantly reduced after LT. CO-pretreated liver grafts showed less up-regulation of TNF-α and inducible nitric oxide synthase messenger RNA (mRNA) and reduced expression of proapoptotic B cell lymphoma 2-associated X protein mRNA, cleaved caspase-3, and poly(adenosine diphosphate ribose) polymerase. In conclusion, the pretreatment of donors with CO ameliorates LT-associated I/R injury with increased hepatic HSP70 expression, particularly in the KC population.

Treprostinil, a prostacyclin analog, ameliorates ischemia-reperfusion injury in rat orthotopic liver transplantation

Prostaglandins have been evaluated for their ability to reduce IRI after liver transplantation; however, poor stability, side effects and the inability to show a significant difference in primary endpoint have limited their clinical application. Treprostinil, a prostacyclin (PGI(2) ) analog, has a higher potency and longer elimination half-life than other commercially available PGI(2) analogs. We examined the efficacy of treprostinil to prevent IRI during OLT. OLT was performed in syngeneic Lewis rats after 18 h of cold preservation (4°C) in the UW solution. IRI significantly increased serum ALT and AST levels, neutrophil infiltration, hepatic necrosis and mRNA levels of proinflammatory cytokines post-OLT, while treatment with treprostinil decreased all the parameters. Cold storage of liver grafts significantly reduced ATP levels and treprostinil restored energy levels in liver grafts early postreperfusion. In addition, treprostinil preserved the sinusoidal endothelial cell lining and reduced platelet deposition early post-transplantation compared to placebo. Hepatic tissue blood flow was significantly compromised in the placebo group, whereas treprostinil maintained blood-flow similar to normal levels. Treprostinil protected the liver graft against IRI during OLT. Treprostinil has the potential to serve as a therapeutic option to protect the liver graft against I/R injury in patients undergoing OLT.

The protective role of CD59 and pathogenic role of complement in hepatic ischemia and reperfusion injury

Hepatic ischemia-reperfusion injury (IRI) is a major factor influencing graft outcome in liver transplantation, but its mechanism is not well defined. Although complement, including the membrane attack complex (MAC), a terminal product of complement activation, is thought to be involved in the multiple reactions subsequent to the ischemia-reperfusion (IR) process, the role of MAC in the pathogenesis of hepatic IRI requires further investigation. We used a warm ischemia-reperfusion injury model in mice and a syngeneic orthotopic liver transplantation model in rats to define the role of complement, including MAC, in hepatic IR. CD59-deficient mice had more severe liver dysfunction, evidenced by increased aspartate aminotransferase levels and increased injury of liver parenchymal and nonparenchymal cells than did CD59-sufficient mice during warm hepatic IR. Furthermore, complement depletion in CD59-deficient mice by pretreatment with cobra venom factor (CVF) or the genetic introduction of C3 deficiency partially protected against development of the severe liver dysfunction that occurred in CD59-deficient mice. Severity of liver dysfunction correlated with MAC deposition, apoptotic cells, and increased inflammatory mediators such as tumor necrosis factor α. Moreover, depletion of complement with CVF in orthotopic liver transplantation recipient rats attenuated IRI of the donor livers. Taken together, these results highlight the protective role of CD59 and pathogenic role of complement, including MAC, in the pathogenesis of hepatic IRI.

Vascular endothelial growth factor receptor-1 signaling promotes liver repair through restoration of liver microvasculature after acetaminophen hepatotoxicity

Vascular endothelial growth factor (VEGF) and its receptors promote liver regeneration. The objective of the present study was to examine the role of VEGF receptor 1 (VEGFR1) signaling in hepatic tissue repair after acetaminophen (N-acetyl-para-aminophenol) (APAP)-induced liver injury. To do this, we treated VEGFR1 tyrosine kinase knockout (VEGFR1 TK(-/-)) and wild-type (WT) mice with APAP (300 mg/kg, ip). In WT mice, serum levels of alanine aminotransferase (ALT) and the necrotic area peaked between 8 and 24 h and then declined. In VEGFR1 TK(-/-) mice, ALT levels remained high at 48 h and extensive hepatic necrosis and hemorrhage were observed, as well as high mortality. Downregulation of hepatic messenger RNA expression of VEGFR1 and VEGFR2 was also noted in VEGFR1 TK(-/-) mice. VEGFR1 TK(-/-) mice displayed lower expression of proliferating cell nuclear antigen and of growth factors including hepatocyte growth factor, CD31, and basic fibroblast growth factor than WT. The hepatic microvasculature in VEGFR1 TK(-/-) was compromised as evidenced by impaired sinusoidal perfusion, suppressed endocytosis in liver sinusoidal endothelial cells (LSECs), and the formation of large gaps in LSECs. In WT mice, immunofluorescence revealed that recruited VEGFR1(+) cells in the necrotic area were positive for CD11b. VEGFR1 TK(-/-) exhibited fewer VEGFR1(+) and VEGFR2(+) cells. These results suggest that VEGFR1 signaling facilitates liver recovery from APAP hepatotoxicity by preventing excessive hemorrhage and reconstituting the sinusoids through recruitment of VEGFR1-expressing macrophages to the injured area and also through affecting expression of genes including hepatotrophic and pro-angiogenic growth factors.

Liver sinusoidal endothelial and biliary cell repopulation following irradiation and partial hepatectomy

AIM: To investigate whether irradiation (IR) and partial hepatectomy (PH) may prepare the host liver for non-parenchymal cell (NPC) transplantation.

METHODS: Livers of dipeptidyl peptidase IV (DPPIV)-deficient rats were pre-conditioned with external beam IR (25 Gy) delivered to two-thirds of the right liver lobules followed by a one-third PH of the untreated lobule. DPPIV-positive liver cells (NPC preparations enriched for liver sinusoidal endothelial cells (LSECs) and hepatocytes) were transplanted via the spleen into the recipient livers. The extent and quality of donor cell engraftment and growth was studied over a long-term interval of 16 wk after transplantation.

RESULTS: Host liver staining demonstrated 3 different repopulation types. Well defined clusters of donor-derived hepatocytes with canalicular expression of DPPIV were detectable either adjacent to or in between large areas of donor cells (covering up to 90% of the section plane) co-expressing the endothelial marker platelet endothelial cell adhesion molecule. The third type consisted of formations of DPPIV-positive duct-like structures which co-localized with biliary epithelial CD49f.

CONCLUSION: Liver IR and PH as a preconditioning stimulus enables multiple cell liver repopulation by donor hepatocytes, LSECs, and bile duct cells.

Pharmacological strategies against cold ischemia reperfusion injury

IMPORTANCE OF THE FIELD

Good organ preservation is a determinant of graft outcome after revascularization. The necessity of increasing the quality of organ preservation, as well as of extending cold storage time, has made it necessary to consider the use of pharmacological additives.

AREAS COVERED IN THIS REVIEW

The complex physiopathology of cold-ischemia-reperfusion (I/R) injury--and in particular cell death, mitochondrial injury and endoplasmic reticulum stress--are reviewed. Basic principles of the formulation of the different preservation solutions are discussed.

WHAT THE READER WILL GAIN

Current strategies and new trends in static organ preservation using additives such as trimetazidine, polyethylene glycols, melatonin, trophic factors and endothelin antagonists in solution are presented and discussed. The benefits and mechanisms responsible for enhancing organ protection against I/R injury are also discussed. Graft preservation was substantially improved when additives were added to the preservation solutions.

TAKE HOME MESSAGE

Enrichment of preservation solutions by additives is clinically useful only for short periods. For longer periods of cold ischemia, the use of such additives becomes insufficient because graft function deteriorates as a result of ischemia. In such conditions, the preservation strategy should be changed by the use of machine perfusion in normothermic conditions.

Critical role of interferon regulatory factor-1 in murine liver transplant ischemia reperfusion injury

Interferon regulatory factor-1 (IRF-1) is a transcription factor that regulates gene expression during immunity. We hypothesized that IRF-1 plays a pivotal role in liver transplant (LTx) ischemia/reperfusion (I/R) injury. Mouse orthotopic LTx was conducted after 24 hours cold storage in University of Wisconsin (UW) solution in wildtype (WT) C57BL/6 and IRF-1 knockout (KO) mice. IRF-1 deficiency in liver grafts, but not in recipients, resulted in significant reduction of hepatocyte apoptosis and liver injury, as well as improved survival. IRF-1 mRNA up-regulation was typically seen in graft hepatocytes in WT-->WT LTx. Deficiency of IRF-1 signaling in graft resulted in significantly reduced messenger RNA (mRNA) levels for death ligands and death receptors in hepatocytes, as well as decreased caspase-8 activities, indicating that IRF-1 mediates death ligand-induced hepatocyte death. Further, a smaller but significant IRF-1 mRNA up-regulation was seen in WT graft nonparenchymal cells (NPC) and associated with interferon gamma (IFN-gamma) mRNA up-regulation exclusively in NPC. IFN-gamma mRNA was significantly reduced in IRF-1 KO graft. Thus, IRF-1 in graft hepatocytes and NPC has distinct effects in hepatic I/R injury. However, LTx with chimeric liver grafts showed that grafts lacking hepatocellular IRF-1 had better protection compared with those lacking IRF-1 in NPC. The study identifies a critical role for IRF-1 in liver transplant I/R injury.

Adrenomedullin in sinusoidal endothelial cells play protective roles against cold injury of liver

Donor organ damage caused by cold preservation is a major problem affecting liver transplantation. Cold preservation most easily damages liver sinusoidal endothelial cells (LSECs), and information about the molecules modulating LSECs function can provide the basis for new therapeutic strategies. Adrenomedullin (AM) is a peptide known to possess anti-apoptotic and anti-inflammatory properties. AM is abundant in vascular endothelial cells, but levels are comparatively low in liver, and little is known about its function there. In this study, we demonstrated both AM and its receptors are expressed in LSECs. AM treatment reduced LSECs loss and apoptosis under cold treatment. AM also downregulated cold-induced expression of TNFalpha, IL1beta, IL6, ICAM1 and VCAM1. AM reduced apoptosis and expression of ICAM1 and VCAM1 in an in vivo liver model subjected to cold storage. Conversely, apoptosis was exacerbated in livers from AM and RAMP2 (AM receptor activity-modifying protein) knockout mice. These results suggest that AM expressed in LSECs exerts a protective effect against cold-organ damage through modulation of apoptosis and inflammation.

Liver graft exposure to carbon monoxide during cold storage protects sinusoidal endothelial cells and ameliorates reperfusion injury in rats

Hepatic ischemia/reperfusion (I/R) injury significantly influences short-term and long-term outcomes after liver transplantation (LTx). The critical step initiating the injury is known to include sinusoidal endothelial cell (SEC) alteration during the cold preservation period. As carbon monoxide (CO) has potent cytoprotective functions on vascular endothelial cells, this study examined if CO treatment of excised liver grafts during cold storage could protect SECs and ameliorate hepatic I/R injury. Rat liver grafts were preserved in University of Wisconsin (UW) solution containing 5% CO (CO-UW solution) for 18 to 24 hours and were transplanted into syngeneic Lewis rats. After 18 hours of cold preservation, SEC damage was evident with propidium iodide (PI) nuclear staining on SECs, and the frequency of PI(+) SECs was significantly lower in grafts stored in CO-UW solution versus those stored in control UW solution. SEC protection with CO was associated with decreased intercellular cell adhesion molecule translocation and less matrix metalloproteinase release during cold preservation. After LTx with 18 hours of cold preservation, serum alanine aminotransferase levels and hepatic necrosis were significantly less in the CO-UW group than in the control UW group. With 24 hours of cold storage, 35% (7/20) survived with control UW solution, whereas the survival with CO-UW solution improved to 80% (8/10). These beneficial effects of CO-UW solution were associated with a significant reduction of neutrophil extravasation, down-regulation of hepatic messenger RNA for tumor necrosis factor alpha and intercellular cell adhesion molecule 1, and less hepatic extracellular signal-regulated kinase activation. Liver grafts from Kupffer cell-depleted donors or pseudogerm-free donors showed less SEC death during cold preservation, and CO-UW solution further reduced SEC death. In conclusion, CO delivery to excised liver grafts during cold preservation efficiently ameliorates SEC damage and hepatic I/R injury.

Preconditioning, organ preservation, and postconditioning to prevent ischemia-reperfusion injury to the liver

Ischemia and reperfusion lead to injury of the liver. Ischemia-reperfusion injury is inevitable in liver transplantation and trauma and, to a great extent, in liver resection. This article gives an overview of the mechanisms involved in this type of injury and summarizes protective and treatment strategies in clinical use today. Intervention is possible at different time points: during harvesting, during the period of preservation, and during implantation. Liver preconditioning and postconditioning can be applied in the transplant setting and for liver resection. Graft optimization is merely possible in the period between the harvest and the implantation. Given that there are 3 stages in which a surgeon can intervene against ischemia-reperfusion injury, we have structured the review as follows. The first section reviews the approaches using surgical interventions, such as ischemic preconditioning, as well as pharmacological applications. In the second section, static organ preservation and machine perfusion are addressed. Finally, the possibility of treating the recipient or postconditioning is discussed.

Bone marrow progenitor cells repair rat hepatic sinusoidal endothelial cells after liver injury

BACKGROUND & AIMS

Damage to hepatic sinusoidal endothelial cells (SECs) initiates sinusoidal obstruction syndrome (SOS), which is most commonly a consequence of myeloablative chemoirradiation or ingestion of pyrrolizidine alkaloids such as monocrotaline (Mct). This study examines whether SECs are of bone marrow origin, whether bone marrow repair can be a determinant of severity of liver injury, and whether treatment with progenitor cells is beneficial.

METHODS

Mct-treated female rats received infusion of male whole bone marrow or CD133(+) cells at the peak of sinusoidal injury. The Y chromosome was identified in isolated SECs by fluorescent in situ hybridization. Bone marrow suppression was induced by irradiation of both lower extremities with shielding of the abdomen.

RESULTS

SECs in uninjured liver have both hematopoietic (CD45, CD33) and endothelial (CD31) markers. After Mct-induced SOS, infusion of bone marrow-derived CD133(+) progenitor cells replaces more than one quarter of SECs. All CD133(+) cells recovered from the SEC fraction after injury are CD45(+). CD133(+)/CD45(+) progenitors also repaired central vein endothelium. Mct suppresses CD133(+)/CD45(+) progenitors in bone marrow by 50% and in the circulation by 97%. Irradiation-induced bone marrow suppression elicited SOS from a subtoxic dose of Mct, whereas infusion of bone marrow during the necrotic phase of SOS nearly eradicates histologic features of SOS.

CONCLUSIONS

SECs have both hematopoietic and endothelial markers. Bone marrow-derived CD133(+)/CD45(+) progenitors replace SECs and central vein endothelial cells after injury. Toxicity to bone marrow progenitors impairs repair and contributes to the pathogenesis of SOS, whereas timely infusion of bone marrow has therapeutic benefit.

Graft preconditioning with low-dose tacrolimus (FK506) and nitric oxide inhibitor aminoguanidine (AGH) reduces ischemia/reperfusion injury after liver transplantation in the rat

Ischemia/reperfusion (I/R) injury is a main cause of primary dysfunction or non-function after liver transplantation (LTx). Recent evidence indicates that an increase in nitric oxide (NO) production after LTx is associated with I/R injury. The aim of this study was to demonstrate that low-dose FK506 in combination with aminoguanidine (AGH), which leads to a reduction of NO levels, has a protective effect by reducing I/R associated injury after LTx. Fortyone DA-(RT1av1) rats served as donors and recipients for syngenic orthotopic arterialised LTx. They were divided into 4 groups: controls without pre-/treatment (I), pre-/treatment with high-dose FK506 (II), pre-/treatment with AGH only (III), and pre-/treatment with low-dose FK506 in combination with AGH (IV). After LTx the laboratory parameters and liver biopsy were performed. The levels of transaminase (ALT) in groups I, II and III were significantly higher on day 3 after LTx compared to group IV (p = 0.001, p = 0.001, p = 0.000). In group IV the I/R-associated liver necrosis rate was reduced significantly. Our results demonstrated that a combined dual pharmacological pretreatment (group IV) reduced I/R injury of the graft after LTx in a rat model.

Inhibition of Kupffer cell-mediated early proinflammatory response with carbon monoxide in transplant-induced hepatic ischemia/reperfusion injury in rats

Proinflammatory responses play critical roles in hepatic ischemia/reperfusion (I/R) injury associating with liver transplantation (LTx), and carbon monoxide (CO) can effectively down-regulate them. Using wild-type (WT) to enhanced green fluorescent protein (EGFP)-transgenic rat LTx with 18-hour cold preservation in University of Wisconsin solution, this study analyzed the relative contribution of donor and host cells during early posttransplantation period and elucidated the mechanism of hepatic protection by CO. CO inhibited hepatic I/R injury and reduced peak alanine aminotransferase levels at 24 hours and hepatic necrosis at 48 hours. Abundant EGFP(+) host cells were found in untreated WT liver grafts at 1 hour and included nucleated CD45(+) leukocytes (myeloid, T, B, and natural killer cells) and EGFP(+) platelet-like depositions in the sinusoids. However, reverse transcription polymerase chain reaction (RT-PCR) analysis of isolated graft nonparenchymal cells (NPCs) revealed that I/R injury-induced proinflammatory mediators [for example, tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS)] were not up-regulated in purified CD45(+) cells of donor or host origin. Instead, TNF-alpha and IL-6 messenger RNA (mRNA) elevation was exclusively seen in isolated CD68(+) cells, whereas iNOS mRNA up-regulation was seen in hepatocytes. Nearly all CD68(+) cells at 1 hour after LTx were EGFP(-) donor Kupffer cells, and CO efficiently inhibited TNF-alpha and IL-6 up-regulation in the CD68(+) Kupffer cell fraction. When graft Kupffer cells were inactivated with gadolinium chloride, activation of inflammatory mediators in liver grafts was significantly inhibited. Furthermore, in vitro rat primary Kupffer cell culture also showed significant down-regulation of lipopolysaccharide (LPS)-induced inflammatory responses by CO.

CONCLUSION

These results indicate that CO ameliorates hepatic I/R injury by down-regulating graft Kupffer cells in early postreperfusion period. The study also suggests that different cell populations play diverse roles by up-regulating distinctive sets of mediators in the acute phase of hepatic I/R injury.