Human Adipose-Derived Mesenchymal Stem Cells Promote Liver Regeneration

Background and Aims: Liver regeneration (LR) is of crucial importance to patients with acute liver failure, those undergoing live donor liver transplantations or extended liver resections. Effective treatment strategies aimed at accelerating liver regeneration could offer major benefits in these patients. Due to easy accessibility, human adipose-derived mesenchymal stem cells (HADMSC) are an attractive source for regenerative medicine. Herein, we investigated the effect of HADMSC on LR in a murine model. We hypothesized that HADMSC will promote LR. Methods: Mice were subjected to CCl₄-induced acute liver failure (ALF). Animals in the experimental arm were treated with HADMSC prior to CCl₄-induced ALF. Liver injury was evaluated using serum levels of alanine aminotransferase (ALT), serum interleukin-6 (IL-6), and histopathology. Liver samples were stained for a specific marker of regeneration, proliferating cell nuclear antigen (PCNA). Results: Histology, serum IL-6, and ALT release revealed that HADMSC treatment attenuated liver injury compared with control animals. In addition, animals treated with HADMSC were observed to have improved survival and increased number of PCNA positive cells on histology when compared with controls. Conclusion: HADMSCs represent a potential therapeutic strategy to promote liver regeneration.     

Cellular therapies for liver replacement

Insufficient donor organs for orthotopic liver transplantation worldwide have urgently increased the requirement for new therapies for acute and chronic liver disease. Whilst none are yet clinically proven there are at least two different approaches for which there is extensive experimental data, some human anecdotal evidence and some data emerging from Phase 1 clinical trials. Both approaches involve bio-engineering. In vivo tissue engineering involves isolated liver cell transplantation into the liver and/or other ectopic sites and in vitro tissue engineering, using an extracorporeal hepatic support system or bioartificial liver. Some questions are common to both these approaches, such as the best cell source and the therapeutic mass required, and are discussed. Others are specific to each approach. For cell transplantation in vivo the initial engraftment and repopulation will make a critical difference to the outcome, and development of markers for transplanted cells has enabled significant advances in understanding, and therefore manipulating, the process. Moreover, the role of immunosuppression is also important and novel approaches to natural immunosuppression are discussed. For use in a bioartificial liver, the ability for hepatocytes to perform ex vivo at in vivo levels is critical. Three dimensional culture improves cell performance over monolayer cultures. Alginate encapsulated cells offer a suitable 3-D environment for a bioartificial liver since they are both easily manipulatable and cryopreservable. The use of cells derived from stem cells or foetal rather than adult liver cells is also emerging as a potential human cell source which may overcome problems associated with xenogeneic cells.     

Acute liver failure

Acute liver failure (ALF) is a rare but life-threatening disease with varying aetiologies worldwide. Drug-induced liver injury, including paracetamol poisoning, is the main cause in Europe and the USA. Whereas in the developing world, viral hepatitis is most common. ALF is a multisystem illness that leads to development of hepatic encephalopathy, cerebral oedema, vasodilatory shock, coagulopathy, hypoglycaemia and multiple-organ failure. Early referral to a specialist liver unit is essential. The core principles of ALF management are to identify/treat the underlying cause, provide supportive care and treat any complications. Optimal management will allow time for spontaneous liver regeneration or liver transplantation, and result in improved survival rates. This article provides an overview of the key concepts in ALF diagnosis and management.     

肝癌干细胞的研究进展

肿瘤起源于干细胞的假说正在各种人类肿瘤中得到证实.肿瘤不仅是一种基因病,而且是一种干细胞病,基因突变作用于干细胞,干细胞突变成为肿瘤干细胞,这是肿瘤发生、再生、转移和复发的关键.为证实肝癌干细胞的存在,有两个问题必须提出:(1)肝细胞型肝癌是否来源于肝干细胞?(2)肝细胞型肝癌中是否具有干细胞特征的细胞?最新研究表明:肝细胞型肝癌可能是由肝干细胞未分化或分化不全引起的.对于肝癌细胞的研究我们知道肝细胞型肝癌中的细胞具有干细胞特性,如永生性、可移植性以及对治疗手段的抵抗性.但是,至今为止,确切的肝癌干细胞的标记物没有找到,而且没有分离出肝癌干细胞.     

Human Liver Regeneration Is Characterized by the Coordinated Expression of Distinct MicroRNA Governing Cell Cycle Fate

In the absence of adequate compensatory regeneration, overwhelming liver damage can cause acute liver failure (ALF) and death without emergent liver transplantation (LT). Auxiliary LT produces satisfactory outcomes in this setting, with the prospect of native liver regeneration sustaining long‐term survival. Since animal models only partially recapitulate human liver regeneration, we investigated the molecular mechanisms controlling it in this unique LT setting, as an exemplar of human liver regeneration. We demonstrate coordinated changes in expression of microRNA (miRNA) during regeneration that drive proliferation, innate immunity and angiogenesis. In contrast, failed regeneration in a similar cohort is associated with distinct miRNA enforcing cell cycle inhibition and DNA methylation. The miRNA expression associated with successful or failed regeneration when recapitulated in vitro, triggered expression of cardinal regeneration‐linked genes promoting cell cycle entry or inhibition, respectively. Furthermore, inhibition of miRNA 150, 663 and 503, whose downregulation is associated with successful regeneration, induced cell proliferation which a key determinant of successful regeneration. Our data indicate that human liver regeneration may be orchestrated by distinct miRNA controlling key regeneration‐linked processes including hepatocyte proliferation. To our knowledge this is the first characterization of molecular processes associated with human liver regeneration.     

A Distinct Subpopulation of Bone Marrow Mesenchymal Stem Cells,Muse Cells,Directly Commit to the Replacement of Liver Components

Genotyping graft livers by short tandem repeats after human living‐donor liver transplantation (n = 20) revealed the presence of recipient or chimeric genotype cases in hepatocytes (6 of 17, 35.3%), sinusoidal cells (18 of 18, 100%), cholangiocytes (15 of 17, 88.2%) and cells in the periportal areas (7 of 8, 87.5%), suggesting extrahepatic cell involvement in liver regeneration. Regarding extrahepatic origin, bone marrow mesenchymal stem cells (BM‐MSCs) have been suggested to contribute to liver regeneration but compose a heterogeneous population. We focused on a more specific subpopulation (1–2% of BM‐MSCs), called multilineage‐differentiating stress‐enduring (Muse) cells, for their ability to differentiate into liver‐lineage cells and repair tissue. We generated a physical partial hepatectomy model in immunodeficient mice and injected green fluorescent protein (GFP)‐labeled human BM‐MSC Muse cells intravenously (n = 20). Immunohistochemistry, fluorescence in situ hybridization and species‐specific polymerase chain reaction revealed that they integrated into regenerating areas and expressed liver progenitor markers during the early phase and then differentiated spontaneously into major liver components, including hepatocytes (≈74.3% of GFP‐positive integrated Muse cells), cholangiocytes (≈17.7%), sinusoidal endothelial cells (≈2.0%), and Kupffer cells (≈6.0%). In contrast, the remaining cells in the BM‐MSCs were not detected in the liver for up to 4 weeks. These results suggest that Muse cells are the predominant population of BM‐MSCs that are capable of replacing major liver components during liver regeneration.     

Resolution of hypophosphatemia is associated with recovery of hepatic function in children with fulminant hepatic failure

Fulminant hepatic failure (FHF) is a rare but often fatal disease in children. Clinical and laboratory predictors of liver regeneration and recovery, however, have not been well established. We hypothesized that hypophosphatemia may indicate recovery of liver synthetic function in children with FHF. We retrospectively reviewed the medical records of children with FHF who were admitted to UCLA and recovered hepatic function either spontaneously or by liver transplantation (LTx). Serum phosphate (Ph) and prothrombin time or international normalized ratio (INR) were compared over the patient's clinical course. Records of 39 children who spontaneously recovered experienced profound hypophosphatemia that resolved as liver synthetic function improved. Similar patterns were seen in the 84 children who recovered after LTx. We found that hypophosphatemia precedes the recovery of liver synthetic function in children with FHF who recovered with or without transplantation, and that Ph levels return to normal as liver synthetic function improves. These data suggest that hypophosphatemia may be a useful laboratory indicator of recovering liver function in children with FHF.     

Liver transplantation

Huge developments in the field of liver transplantation have occurred over the last 30 years. Improved immunosuppression regimens brought about by the introduction of cyclosporin and tacrolimus, the development of organ preservation solutions and enhanced perioperative care have meant that survival at 1 year following liver transplantation now reaches approximately 90%. The spectrum of disease now treated with liver transplantation has also grown to encompass a wide range of chronic disease and primary liver malignancy. Early referral to specialist centres affords better outcomes for potential recipients and has prompted the development of specific scoring systems to objectively assess liver failure and guide organ allocation. The consistent gap between the number of recipients and availability of organs however, has driven many new developments such as split grafts and live donor transplantation. The use of the marginal graft is now commonplace in many centres in an attempt to reduce waiting list mortality. Here, we examine the origins and evolution of the specialty and describe some of the latest developments in the field of liver transplantation, with specific reference to the surgical techniques currently used as well as recent advances in immunosuppression therapy.     

Liver transplantation

Huge developments in the field of liver transplantation have occurred over the last 30 years. Improved immunosuppression regimens brought about by the introduction of ciclosporin and tacrolimus, the development of organ preservation solutions and enhanced perioperative care have meant that survival at 1 year following liver transplantation now reaches approximately 90%. The spectrum of disease now treated with liver transplantation has also grown to encompass a wide range of chronic disease and primary liver malignancy. Early referral to specialist centres affords better outcomes for potential recipients and has prompted the development of specific scoring systems to objectively assess liver failure and guide organ allocation. The consistent gap between the number of recipients and availability of organs, however, has driven many new developments such as split grafts and live donor transplantation. The use of the marginal graft is now commonplace in many centres in an attempt to reduce waiting list mortality. Here, we examine the origins and evolution of the specialty and describe some of the latest developments in the field of liver transplantation, with specific reference to the surgical techniques currently used as well as recent advances in immunosuppression therapy.     

Liver Graft Regeneration in Right Lobe Adult Living Donor Liver Transplantation

Optimal portal flow is one of the essentials in adequate liver function, graft regeneration and outcome of the graft after right lobe adult living donor liver transplantation (ALDLT). The relations among factors that cause sufficient liver graft regeneration are still unclear. The aim of this study is to evaluate the potential predisposing factors that encourage liver graft regeneration after ALDLT. The study population consisted of right lobe ALDLT recipients from Chang Gung Memorial Hospital-Kaohsiung Medical Center, Taiwan. The records, preoperative images, postoperative Doppler ultrasound evaluation and computed tomography studies performed 6 months after transplant were reviewed. The volume of the graft 6 months after transplant divided by the standard liver volume was calculated as the regeneration ratio. The predisposing risk factors were compiled from statistical analyses and included age, recipient body weight, native liver disease, spleen size before transplant, patency of the hepatic venous graft, graft weight-to-recipient weight ratio (GRWR), posttransplant portal flow, vascular and biliary complications and rejection. One hundred forty-five recipients were enrolled in this study. The liver graft regeneration ratio was 91.2 ± 12.6% (range, 58–151). The size of the spleen (p = 0.00015), total portal flow and GRWR (p = 0.005) were linearly correlated with the regeneration rate. Patency of the hepatic venous tributary reconstructed was positively correlated to graft regeneration and was statistically significant (p = 0.017). Splenic artery ligation was advantageous to promote liver regeneration in specific cases but splenectomy did not show any positive advantage. Spleen size is a major factor contributing to portal flow and may directly trigger regeneration after transplant. Control of sufficient portal flow and adequate hepatic outflow are important factors in graft regeneration.     

Liver transplantation

Huge developments in the field of liver transplantation have occurred over the last 30 years. Improved immunosuppression regimens following the introduction of calcineurin-inhibitors, the development of organ preservation solutions and enhanced peri-operative care have resulted in 1-year survival rates of approximately 90%. The spectrum of disease now treated with liver transplantation has also grown to encompass a wide range of chronic disease and hepatic malignancies. Early referral to specialist centres affords better outcomes for potential recipients and has prompted the development of specific scoring systems to objectively assess liver failure and guide organ allocation. The consistent gap between the number of recipients and availability of organs has driven many new developments such as split grafts and live donor transplantation. Use of the marginal graft is now commonplace in many centres in an attempt to reduce waiting list mortality. Here, we examine the origins and evolution of the speciality and describe some of the latest developments in the field of liver transplantation, with specific reference to current surgical techniques, evolving organ preservation technology and recent advances in associated medical therapies.     

CMV infection, diagnosis and antiviral strategies after liver transplantation

Cytomegalovirus (CMV) is a significant pathogen complicating the post-transplant course of organ recipients. In liver transplant patients, the febrile clinical illness caused by CMV may be associated with end-organ disease, such as hepatitis or infection of the gastrointestinal tract. In addition to direct effects, CMV may have indirect effects including the risk of other infections or graft rejection. Recently, major advances in the management of CMV infection have been achieved through the development of new diagnostic techniques and antiviral strategies to prevent CMV disease. Quantitative nucleic acid testing to monitor viral load is now commonly used to diagnose and guide the treatment of CMV infections. The standardization of the testing, however, needs to be improved. There are two main strategies to prevent CMV disease after liver transplantation: prophylaxis and pre-emptive therapy. Both strategies are effective, but also have disadvantages. The disadvantages of prophylaxis include prolonged drug exposure, the development of resistance and, most of all, the development of delayed and late-onset CMV disease. On the other hand, the pre-emptive strategy is based on frequent laboratory monitoring of viral loads, and some patients may develop symptomatic infection before the diagnosis of CMV. This overview summarizes the current status of CMV in liver transplantation.     

Functional portal flow competition after auxiliary partial orthotopic living donor liver transplantation in noncirrhotic metabolic liver disease

Auxilliary partial orthotopic liver transplantation (APOLT) was introduced initially as a tentative or permanent support for patients with potentially reversible fulminant hepatic failure and has extended its indication to congenital metabolic disorder of the liver that has otherwise normal functional integrity. Postoperative management of APOLT is complicated because of functional portal flow competition between the native and graft liver. The native portal vein diversion to the graft is sometimes indicated to prevent functional competition; however, it is still an open question whether this technique can be theoretically indicated for APOLT patients. The authors report a on patient with ornithine transcarbamylase deficiency who received APOLT from a living donor without native portal vein diversion. Because of functional portal vein competition between the native and graft liver, the patient had to have portal vein diversion, portal vein embolization, and finally native hepatectomy to induce the graft regeneration after APOLT. After the experience of the current case, primary portal vein diversion for APOLT with noncirrhotic metabolic liver disease patients to prevent functional portal flow competition is recommended.     

辅助肝移植技术创新与展望

辅助肝移植首创于1964年，是一种保留受者部分或全部肝脏的特殊肝移植术式。随着术式创新、病例积累以及对肝再生、移植免疫的机制研究的不断深入，辅助肝移植技术或将发挥更大的优势，在供体缺乏的情况下，最大范围地使病人获益。近年来，辅助肝移植在遗传代谢性肝病、不可切除性肝恶性肿瘤等治疗中不断创新，但辅助肝移植需要更严格的风险管理、更周密的术前评估和更加个体化的免疫调控。     

Successful transplantation of a 20% partial liver graft in rats: a technical innovation

BACKGROUND: Graft-size disparity negatively impacts the postoperative outcome in the setting of adult-to-adult living donor liver transplantation. MATERIALS AND METHODS: As a model for partial liver transplantation in rats using a minimized graft volume, we orthotopically transplanted a 20% reduced-size liver with the two-cuff method. Blood chemistry, graft weight restoration, and labeling indices of 5-bromo-2'-deoxyuridine were estimated. RESULTS: We achieved 100% 2-week survival. Hepatic mass was restored rapidly with early normalization of biochemical parameters, although albumin synthesis capacity required more time to recover. CONCLUSION: This technique has great potential for research as well as a therapeutic approach to regeneration and functional recovery of small liver grafts under various posttransplant circumstances.     

Reuse of Auxiliary Liver Grafts in Second Recipients With Chronic Liver Disease

We describe the first cases of reuse of auxiliary liver grafts for orthotopic transplantation in chronic liver disease. A reduced liver graft (segments 2, 3, half of 4) was first transplanted auxiliary for acute liver failure using a new technique. After regeneration of both native liver and graft, the auxiliary graft was removed and immunosuppression discontinued in the first recipients. After informed consent of donors and recipients, both auxiliary grafts were then orthotopically transplanted into second recipients. Both grafts function normally. Reuse of auxiliary grafts may help to reduce the shortage or liver grafts available for transplantation.     

Advances in critical care hepatology

Complications of liver disease are commonly seen in the intensive care unit (ICU). When evaluating patients with liver disease in the ICU, it is important to determine whether it is acute or chronic liver disease. Because the pathophysiological mechanisms differ among acute and chronic liver, they will be consider separately in this review. Significant advances in the management of acute liver failure highlight the importance of intracranial pressure monitoring for Grade III/IV encephalopathy, and suggest that moderate hypothermia may be a promising treatment for these patients with refractory intracranial hypertension. Chronic liver disease is best discussed in terms of the various complications that may ensue such as ascites, hepatorenal syndrome, spontaneous bacterial peritonitis, variceal hemorrhage and hepatic encephalopathy. Each of these conditions will be discussed with specific attention to critical care management.     

Successful treatment of CCl4-induced acute liver failure with portal vein arterialization in the rat

BACKGROUND: Optimization of the conditions for regeneration is a major goal in the management of patients with acute liver failure (ALF). Previous observations suggested that hyperoxygenation of the liver may improve its regenerative capacity. Thus, this study aimed to determine whether an additional supply of oxygenated blood achieved by portal vein arterialization (PVA) is protective in rat ALF caused by toxin administration or hepatectomy. METHODS: Sprague-Dawley rats were subjected or not to PVA after CCl(4) intoxication or extended hepatectomy. PVA was performed by interposing a stent between the left renal artery and splenic vein after left nephrectomy and splenectomy. Liver injury was evaluated by the serum ALT level and necrotic cell count. Hepatocyte regeneration was assessed by calculating the mitotic index and bromodeoxyuridine (BrdU) staining. The 10-day survival was assessed in separate experimental groups. RESULTS: The pO(2) in portal blood increased significantly following PVA. In the CCl(4)-induced ALF, serum ALT levels and necrosis were significantly reduced in arterialized than non-arterialized rats. PVA greatly promotes liver regeneration in both models. Finally, PVA significantly improved survival compared to controls (CCl(4): 100 versus 40%; 90% hepatectomy: 90 versus 30%). Interestingly, in the CCl(4)-induced ALF, survival was 100% even when the shunt was closed after 48 h. CONCLUSION: These data indicate that the additional supply of arterial oxygenated blood through PVA promotes a rapid regeneration leading to the resolution of toxic-induced massive liver necrosis and a faster restoration of liver mass after partial hepatectomy in rats. Thus, PVA may represent a novel tool for optimizing hepatocyte regeneration.     

Liver transplantation

Huge developments in the field of liver transplantation have occurred over the last 50 years. Improved immunosuppression regimens following the introduction of calcineurin-inhibitors, the development of novel organ preservation strategies, and enhanced perioperative care have resulted in 1-year survival rates of approximately 90%. The spectrum of disease now treated with liver transplantation has also grown to encompass a wide range of acute and chronic disease and hepatic malignancies. Early referral to specialist centres affords better outcomes for potential recipients and has prompted the development of specific scoring systems to objectively assess liver failure and guide organ allocation. The consistent gap between the number of recipients and availability of organs has driven many new developments such as split grafts and live donor transplantation. Use of the marginal graft is necessitated in many centres in an attempt to reduce the waiting list mortality. Here, we examine the origins and evolution of the speciality and describe some of the latest developments in the field of liver transplantation, with specific reference to current surgical techniques, evolving organ preservation technology and recent advances in associated medical therapies.