The liver is the largest solid organ in the body and is frequently the site of injury. During disease, liver injury is usually compensated for by exceptionally efficient regeneration which occurs both from differentiated epithelia and also from an undifferentiated cell population with stem cell like qualities known as hepatic progenitor cells (HPCs). HPCs are particularly active during massive or chronic liver injury and therefore are an attractive target for much needed novel therapies to enhance regeneration in patients for whom the only current effective therapy is liver transplantation. Stem cells in other organs systems are believed to reside in a specialised microenvironment or niche which supports their maintenance and function. To investigate the hypothesis that HPCs are supported by a functional niche and are capable of regenerating hepatocytes, we commenced by establishing a number of murine in vivo models. Having shown a stereotypical niche, consisting of macrophages, myofibroblasts and laminin exists in both animal models and human disease, we investigated the active recruitment of extrahepatic cells into this niche and showed that macrophages are actively recruited from the bone marrow during liver injury. Macrophages were shown to influence HPC behaviour during injury. Furthermore using macrophages as a cellular therapy, induced HPC activation with corresponding changes to liver structure and function. Investigation of signalling pathways revealed and confirmed a TWEAK dependent activation of HPCs following macrophage transfer. Having demonstrated the potential for macrophage therapy via HPC activation, we aimed to study the ability of HPCs to regenerate the hepatic parenchyma. To do so we developed and characterised a novel model of hepatocellular injury and HPC activation. Using the genetic labeling of hepatocytes in this model we were able to show rapid and large scale repopulation of hepatocytes from a precursor source with HPCs being the critical precursor source of hepatocellular regeneration. In addition this process is again dependent on TWEAK signalling, without which HPC mediated regeneration fails resulting in mortality. Therefore HPCs are an attractive biological target for regenerative medicine, and both TWEAK signalling and autologous macrophage infusion offer genuine potential to manipulate these cells as future therapies.

A cirurgia do fígado apresentou extraordinário avanço desde a primeira ressecção planejada realizada por Langenbuch em 1888, e o primeiro transplante de fígado realizado por Starzl em 1963, até atualmente quando extensas ressecções e transplantes de partes do fígado são possíveis. Isso se deve graças, entre outros fatores, ao reconhecimento da grande capacidade regenerativa do fígado. A regeneração hepática tem sido objeto de estudo por quase 100 anos, no entanto, o mecanismo pelo qual o hepatócito é estimulado à replicação não foi completamente elucidado. As citocinas têm papel fundamental no mecanismo de regeneração do fígado, destacando-se entre elas o TNF- e a IL-6. Elas favorecem a indução de outras citocinas e estimulam a regeneração. Elas, no entanto, contribuem também no mecanismo de lesão do hepátocito em situações como a da isquemia e reperfusão. Alguns dados da literatura são conflitantes e mostram respostas diferentes na regeneração hepática provocadas pela inibição do TNF-. A pentoxifilina é um derivado da metilxantina que tem uma potente ação inibidora da síntese de TNF-. O presente estudo visa a avaliar o efeito da administração de pentoxifilina na regeneração hepática em ratos submetidos a ressecção de 70% do parênquima hepático. Os animais foram divididos em 4 grupos: Controle, grupo I (laparotomia), Grupo II (hepatectomia + salina) e grupo III (hepatectomia + pentoxifilina). Foram realizadas dosagens de transaminases (AST e ALT) 2, 6 e 48 horas após o procedimento, de citocinas (TNF- e IL-6) no soro e no tecido hepático 2 e 6 horas após a operação, e realizado estudo histológico para avaliação do índice mitótico e do PCNA com o intuito de quantificar a regeneração hepática 48 horas após o procedimento. Os resultados mostraram que a pentoxifilina foi efetiva no bloqueio do TNF- e da IL-6 no soro, mas não no tecido hepático dos animais, e que esse bloqueio melhorou a regeneração hepática documentada pelo índice mitótico e pelo PCNA. Pudemos então concluir que a pentoxifilina, nas condições do presente estudo, melhorou a regeneração do fígado após ressecção de 70% do parênquima hepático por mecanismo relacionado a redução das citocinas séricas e manutenção das citocinas do tecido hepático / Liver surgery has grown extraordinarily from the first planned ressection performed by Langenbuch in 1888, and the first successful orthotopic liver transplantation by Starzl in 1963 to the extended liver resections and living donors liver transplantations currently performed in many centers. It occurred, among others factors, because of the recognition of the great liver regenerative capacity. Liver regeneration has been object of study for almost 100 years. However the mechanism by which hepatocytes replication is stimulated is not completely elucidated. Cytokines, mainly TNF- and IL-6, play a pivotal role in liver regeneration mechanism. However they also contribute to hepatocytes damage mechanisms, like in ischemia-reperfusion injury. Indeed some studies are conflicting, and show different effects of TNF- inhibition in liver regeneration. Pentoxifylline is a methylxanthine compound known to inhibits TNF- production by monocytic cells. The present study aims to evaluate the effect of pentoxifylline in liver regeneration in rats submitted to 70% hepatectomy. The animals were randomized into 4 groups: Control, group I (sham), Group II (hepatectomy + saline) and group III (hepatectomy + pentoxifylline). AST and ALT serum levels were determined at 2, 6 and 48 hours after the procedure, TNF- and IL-6 serum levels and liver tissue levels were determined at 2 and 6 hours after the operation. Mitotic index and PCNA were performed to quantify liver regeneration 48 hours after the procedure. We found that pentoxifylline reduces TNF- and IL-6 serum levels, without changes in the liver tissue levels. These results were associated with an improvement liver regeneration evaluated by the mitotic index and the PCNA. We concluded that pentoxifylline improved liver regeneration after 70% hepatectomy by a mechanism that comprises blood but not hepatic cytokines reduction

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 163-183).

There is a growing literature of clinical studies of bone marrow (BM) cell therapy for liver cirrhosis. At present, the optimum choice of cell type(s) and the mechanism(s) of effect remain undefined. Cells of the monocyte-macrophage lineage have key roles in the development and resolution of liver fibrosis. Therefore, I tested the therapeutic effects of these cells in the context of experimental murine liver fibrosis. The effects of unmanipulated, syngeneic macrophages, their specific BM precursors and unfractionated (whole) BM cells were examined in the iterative carbon tetrachloride model of liver fibrosis. BM-derived macrophage (BMM) delivery resulted in early chemokine upregulation with the hepatic recruitment of endogenous macrophages and neutrophils. These cells delivered matrix metalloproteinases-13 and -9 respectively, into the hepatic scar. The effector cell infiltrate was accompanied by increased levels of the anti-inflammatory cytokine IL-10. A reduction in hepatic myofibroblasts was followed by reduced fibrosis detected 4 weeks after macrophage infusion. Serum albumin levels were elevated at this time. Upregulation of the liver progenitor cell mitogen TWEAK preceded expansion of the progenitor cell compartment. BMM delivery increased hepatic expression of cytokines with reparative effects (including colony stimulating factor-1, insulin-like growth factor-1 and vascular endothelial growth factor). In contrast to the effects of differentiated macrophages, liver fibrosis was not significantly improved by the application of macrophage precursors and was exacerbated by whole BM. BMMs did not affect liver fibrosis or regeneration in the 1% DDC model of biliary disease. These effects were only detected following the intraportal delivery of BM cells. The peripheral (tail) vein administration of BMMs, either singly or repeatedly did not recapitulate the therapeutic phenotype. This was investigated by in vivo tracking of BMMs constitutively expressing green fluorescent protein (GFP). The peripheral administration route resulted in the early (1 hour) accumulation of BMMs within the pulmonary system. This was followed by delayed hepatic engraftment, which was also numerically reduced (< 30%) compared with intraportal administration. Macrophage cell therapy improves clinically relevant parameters in experimental chronic liver injury. Paracrine signalling to endogenous cells amplifies the effect. The benefits from this single, defined cell type suggest clinical potential.

A cirurgia do fígado apresentou extraordinário avanço desde a primeira ressecção planejada realizada por Langenbuch em 1888, e o primeiro transplante de fígado realizado por Starzl em 1963, até atualmente quando extensas ressecções e transplantes de partes do fígado são possíveis. Isso se deve graças, entre outros fatores, ao reconhecimento da grande capacidade regenerativa do fígado. A regeneração hepática tem sido objeto de estudo por quase 100 anos, no entanto, o mecanismo pelo qual o hepatócito é estimulado à replicação não foi completamente elucidado. As citocinas têm papel fundamental no mecanismo de regeneração do fígado, destacando-se entre elas o TNF- e a IL-6. Elas favorecem a indução de outras citocinas e estimulam a regeneração. Elas, no entanto, contribuem também no mecanismo de lesão do hepátocito em situações como a da isquemia e reperfusão. Alguns dados da literatura são conflitantes e mostram respostas diferentes na regeneração hepática provocadas pela inibição do TNF-. A pentoxifilina é um derivado da metilxantina que tem uma potente ação inibidora da síntese de TNF-. O presente estudo visa a avaliar o efeito da administração de pentoxifilina na regeneração hepática em ratos submetidos a ressecção de 70% do parênquima hepático. Os animais foram divididos em 4 grupos: Controle, grupo I (laparotomia), Grupo II (hepatectomia + salina) e grupo III (hepatectomia + pentoxifilina). Foram realizadas dosagens de transaminases (AST e ALT) 2, 6 e 48 horas após o procedimento, de citocinas (TNF- e IL-6) no soro e no tecido hepático 2 e 6 horas após a operação, e realizado estudo histológico para avaliação do índice mitótico e do PCNA com o intuito de quantificar a regeneração hepática 48 horas após o procedimento. Os resultados mostraram que a pentoxifilina foi efetiva no bloqueio do TNF- e da IL-6 no soro, mas não no tecido hepático dos animais, e que esse bloqueio melhorou a regeneração hepática documentada pelo índice mitótico e pelo PCNA. Pudemos então concluir que a pentoxifilina, nas condições do presente estudo, melhorou a regeneração do fígado após ressecção de 70% do parênquima hepático por mecanismo relacionado a redução das citocinas séricas e manutenção das citocinas do tecido hepático / Liver surgery has grown extraordinarily from the first planned ressection performed by Langenbuch in 1888, and the first successful orthotopic liver transplantation by Starzl in 1963 to the extended liver resections and living donors liver transplantations currently performed in many centers. It occurred, among others factors, because of the recognition of the great liver regenerative capacity. Liver regeneration has been object of study for almost 100 years. However the mechanism by which hepatocytes replication is stimulated is not completely elucidated. Cytokines, mainly TNF- and IL-6, play a pivotal role in liver regeneration mechanism. However they also contribute to hepatocytes damage mechanisms, like in ischemia-reperfusion injury. Indeed some studies are conflicting, and show different effects of TNF- inhibition in liver regeneration. Pentoxifylline is a methylxanthine compound known to inhibits TNF- production by monocytic cells. The present study aims to evaluate the effect of pentoxifylline in liver regeneration in rats submitted to 70% hepatectomy. The animals were randomized into 4 groups: Control, group I (sham), Group II (hepatectomy + saline) and group III (hepatectomy + pentoxifylline). AST and ALT serum levels were determined at 2, 6 and 48 hours after the procedure, TNF- and IL-6 serum levels and liver tissue levels were determined at 2 and 6 hours after the operation. Mitotic index and PCNA were performed to quantify liver regeneration 48 hours after the procedure. We found that pentoxifylline reduces TNF- and IL-6 serum levels, without changes in the liver tissue levels. These results were associated with an improvement liver regeneration evaluated by the mitotic index and the PCNA. We concluded that pentoxifylline improved liver regeneration after 70% hepatectomy by a mechanism that comprises blood but not hepatic cytokines reduction

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第13355号 / 論医博第2201号 / 新制||医||1044(附属図書館) / (主査)教授 妹尾 浩, 教授 羽賀 博典, 教授 武藤 学 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

Liver progenitor cells (LPCs) play a major role in the regeneration process following chronic liver damage. LPCs can differentiate into hepatocytes and cholangiocytes and thus are capable of replenishing the damaged liver. Due to their plasticity and robust nature in culture systems, they are promising candidates for use in cell therapy. However, to be able to use LPCs as tissue regenerating stem cell-like cells in the clinic, we need to fully understand how they are controlled. Although a strong association between LPCs and inflammation has been shown in many chronic liver diseases, the role of the immune system in LPC-mediated hepatic regeneration is poorly understood. We hypothesise that specific immune cells and mediators are needed to induce the LPC compartment, and that these are common to the LPC response in different injury settings. Therefore, the present study focused on the characterisation of the inflammatory environment in the LPC response, which generates this niche. The aims of this study were (i) to identify the immune cells that are important for the LPC response, (ii) to define the cytokine profile and (iii) to determine the role of the cytokine producing cells during liver regeneration. To study hepatic inflammation following liver injury, a diet-induced model of liver injury (choline-deficient, ethionine-supplemented diet, CDE diet) was compared to two transgenic mouse models of immune-mediated hepatitis (Met-Kb, 178.3). Although all three models are characterised by hepatitis, histological analysis revealed that LPCs were only detectable in the CDE and Met-Kb livers. In the 178.3 model, livers regenerated from proliferating hepatocytes. An LPC response could not be induced in these mice even when liver damage was made more severe. In the other two models, LPC numbers increased over time showing the highest numbers one week after the peak of liver injury. LPCs were often found in close proximity to inflammatory cells, in particular macrophages.

Indiana University-Purdue University Indianapolis (IUPUI) / CXXC finger protein 1 (Cfp1), a component of the Set1 histone methyltransferase complex, is a critical epigenetic regulator of both histone and cytosine methylation. Murine embryos lacking Cfp1 are unable to gastrulate and Cfp1-null embryonic stem (ES) cells fail to undergo cellular differentiation in vitro. However, expression of wild type Cfp1 in Cfp1-null ES cells rescues differentiation capacity, suggesting that dynamic epigenetic changes occurring during lineage specification require Cfp1. The domain structure of Cfp1 consists of a DNA binding CXXC domain and an N-terminal plant homeodomain (PHD). PHDs are frequently observed in chromatin remodeling proteins, functioning as reader modules for histone marks. However, the histone binding properties and underlying functional significance of Cfp1 PHD are largely unknown. My research revealed that Cfp1 PHD directly and specifically binds to histone H3K4me1/me2/me3 marks. A point mutation that abolishes binding to methylated H3K4 (W49A) does not affect rescue of cellular differentiation, but, point mutations that abolish both methylated H3K4 (W49A) and DNA (C169A) binding result in defective in vitro differentiation, indicating that PHD and CXXC exhibit redundant functions. The mammalian liver has the unique ability to regenerate following injury. Previous studies indicated that Cfp1 is essential for hematopoiesis in zebrafish and mice. I hypothesized that Cfp1 additionally plays a role in liver development and regeneration. To understand the importance of Cfp1 in liver development and regeneration, I generated a mouse line lacking Cfp1 specifically in the liver (Cfp1fl/fl Alb-Cre+). Around 40% of these mice display a wasting phenotype and die within a year. Livers of these mice have altered global H3K4me3 levels and often exhibit regenerative nodules. Most importantly, livers of these mice display an impaired regenerative response following partial hepatectomy. Collectively, these findings establish Cfp1 as an epigenetic regulator essential for ES cell function and liver homeostasis and regeneration.

Yun Jing-ping. / "March 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 185-226). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.