Davina Wojtacha

Highly efficient differentiation of hESCs to functional hepatic endoderm requires ActivinA and Wnt3a signaling

Human embryonic stem cells (hESCs) are a valuable source of pluripotential primary cells. To date, however, their homogeneous cellular differentiation to specific cell types in vitro has proven difficult. Wnt signaling has been shown to play important roles in coordinating development, and we demonstrate that Wnt3a is differentially expressed at critical stages of human liver development in vivo. The essential role of Wnt3a in hepatocyte differentiation from hESCs is paralleled by our in vitro model, demonstrating the importance of a physiologic approach to cellular differentiation. Our studies provide compelling evidence that Wnt3a signaling is important for coordinated hepatocellular function in vitro and in vivo. In addition, we demonstrate that Wnt3a facilitates clonal plating of hESCs exhibiting functional hepatic differentiation. These studies represent an important step toward the use of hESC-derived hepatocytes in high-throughput metabolic analysis of human liver function.

Macrophage therapy for murine liver fibrosis recruits host effector cells improving fibrosis, regeneration, and function.

Clinical studies of bone marrow (BM) cell therapy for liver cirrhosis are under way but the mechanisms of benefit remain undefined. Cells of the monocyte‐macrophage lineage have key roles in the development and resolution of liver fibrosis. Therefore, we tested the therapeutic effects of these cells on murine liver fibrosis. Advanced liver fibrosis was induced in female mice by chronic administration of carbon tetrachloride. Unmanipulated, syngeneic macrophages, their specific BM precursors, or unfractionated BM cells were delivered during liver injury. Mediators of inflammation, fibrosis, and regeneration were measured. Donor cells were tracked by sex‐mismatch and green fluorescent protein expression. BM‐derived macrophage (BMM) delivery resulted in early chemokine up‐regulation with 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 antiinflammatory cytokine interleukin 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. Up‐ regulation of the liver progenitor cell mitogen tumor necrosis factor‐like weak inducer of apoptosis (TWEAK) preceded expansion of the progenitor cell compartment. Increased expression of colony stimulating factor‐1, insulin‐like growth factor‐1, and vascular endothelial growth factor also followed BMM delivery. In contrast to the effects of differentiated macrophages, liver fibrosis was not significantly altered by the application of macrophage precursors and was exacerbated by whole BM. Conclusion: Macrophage cell therapy improves clinically relevant parameters in experimental chronic liver injury. Paracrine signaling to endogenous cells amplifies the effect. The benefits from this single, defined cell type suggest clinical potential. (HEPATOLOGY 2011;)

Hepatic progenitor cells of biliary origin with liver repopulation capacity

Hepatocytes and cholangiocytes self-renew following liver injury. Following severe injury hepatocytes are increasingly senescent, but whether hepatic progenitor cells (HPCs) then contribute to liver regeneration is unclear. Here, we describe a mouse model where the E3 ubiquitin ligase Mdm2 is inducibly deleted in more than 98% of hepatocytes, causing apoptosis, necrosis and senescence with nearly all hepatocytes expressing p21. This results in florid HPC activation, which is necessary for survival, followed by complete, functional liver reconstitution. HPCs isolated from genetically normal mice, using cell surface markers, were highly expandable and phenotypically stable in vitro. These HPCs were transplanted into adult mouse livers where hepatocyte Mdm2 was repeatedly deleted, creating a non-competitive repopulation assay. Transplanted HPCs contributed significantly to restoration of liver parenchyma, regenerating hepatocytes and biliary epithelia, highlighting their in vivo lineage potency. HPCs are therefore a potential future alternative to hepatocyte or liver transplantation for liver disease.

Bone marrow injection stimulates hepatic ductular reactions in the absence of injury via macrophage-mediated TWEAK signaling

Tissue progenitor cells are an attractive target for regenerative therapy. In various organs, bone marrow cell (BMC) therapy has shown promising preliminary results, but to date no definite mechanism has been demonstrated to account for the observed benefit in organ regeneration. Tissue injury and regeneration is invariably accompanied by macrophage infiltration, but their influence upon the progenitor cells is incompletely understood, and direct signaling pathways may be obscured by the multiple roles of macrophages during organ injury. We therefore examined a model without injury; a single i.v. injection of unfractionated BMCs in healthy mice. This induced ductular reactions (DRs) in healthy mice. We demonstrate that macrophages within the unfractionated BMCs are responsible for the production of DRs, engrafting in the recipient liver and localizing to the DRs. Engrafted macrophages produce the cytokine TWEAK (TNF-like weak inducer of apoptosis) in situ. We go on to show that recombinant TWEAK activates DRs and that BMC mediated DRs are TWEAK dependent. DRs are accompanied by liver growth, occur in the absence of liver tissue injury and hepatic progenitor cells can be isolated from the livers of mice with DRs. Overall these results reveal a hitherto undescribed mechanism linking macrophage infiltration to DRs in the liver and highlight a rationale for macrophage derived cell therapy in regenerative medicine.

WNT signaling drives cholangiocarcinoma growth and can be pharmacologically inhibited

Cholangiocarcinoma (CC) is typically diagnosed at an advanced stage and is refractory to surgical intervention and chemotherapy. Despite a global increase in the incidence of CC, little progress has been made toward the development of treatments for this cancer. Here we utilized human tissue; CC cell xenografts; a p53-deficient transgenic mouse model; and a non-transgenic, chemically induced rat model of CC that accurately reflects both the inflammatory and regenerative background associated with human CC pathology. Using these systems, we determined that the WNT pathway is highly activated in CCs and that inflammatory macrophages are required to establish this WNT-high state in vivo. Moreover, depletion of macrophages or inhibition of WNT signaling with one of two small molecule WNT inhibitors in mouse and rat CC models markedly reduced CC proliferation and increased apoptosis, resulting in tumor regression. Together, these results demonstrate that enhanced WNT signaling is a characteristic of CC and suggest that targeting WNT signaling pathways has potential as a therapeutic strategy for CC.

CSF1 Restores Innate Immunity After Liver Injury in Mice and Serum Levels Indicate Outcomes of Patients With Acute Liver Failure

Background & Aims Liver regeneration requires functional liver macrophages, which provide an immune barrier that is compromised after liver injury. The numbers of liver macrophages are controlled by macrophage colony-stimulating factor (CSF1). We examined the prognostic significance of the serum level of CSF1 in patients with acute liver injury and studied its effects in mice. Methods We measured levels of CSF1 in serum samples collected from 55 patients who underwent partial hepatectomy at the Royal Infirmary Edinburgh between December 2012 and October 2013, as well as from 78 patients with acetaminophen-induced acute liver failure admitted to the Royal Infirmary Edinburgh or the University of Kansas Medical Centre. We studied the effects of increased levels of CSF1 in uninjured mice that express wild-type CSF1 receptor or a constitutive or inducible CSF1-receptor reporter, as well as in chemokine receptor 2 (Ccr2)-/- mice; we performed fate-tracing experiments using bone marrow chimeras. We administered CSF1-Fc (fragment, crystallizable) to mice after partial hepatectomy and acetaminophen intoxication, and measured regenerative parameters and innate immunity by clearance of fluorescent microbeads and bacterial particles. Results Serum levels of CSF1 increased in patients undergoing liver surgery in proportion to the extent of liver resected. In patients with acetaminophen-induced acute liver failure, a low serum level of CSF1 was associated with increased mortality. In mice, administration of CSF1-Fc promoted hepatic macrophage accumulation via proliferation of resident macrophages and recruitment of monocytes. CSF1-Fc also promoted transdifferentiation of infiltrating monocytes into cells with a hepatic macrophage phenotype. CSF1-Fc increased innate immunity in mice after partial hepatectomy or acetaminophen-induced injury, with resident hepatic macrophage as the main effector cells. Conclusions Serum CSF1 appears to be a prognostic marker for patients with acute liver injury. CSF1 might be developed as a therapeutic agent to restore innate immune function after liver injury.

Immunological studies of the placenta in systemic lupus erythematosus.

An immunological study was made of the placentae from 5 mothers with lupus erythematosus. 3 of the 5 mothers had anti-DNA antibodies in their sera at the time of delivery and in one of these anti-DNA antibodies were detected in the cord blood. This patient had active renal disease and serological evidence suggestive of circulating immune complexes in her blood at the time of delivery. Immunofluorescence studies showed granular deposition of immunoglobulin and C3 on the trophoblast basement membrane similar to that previously described on the glomerular basement membrane in systemic lupus erythematosus. Anti-DNA antibodies were eluted from the placenta in this case. We suggest that immune complex deposition on the trophoblast basement membrane in patients with active systemic lupus erythematosus may play a part in the increased fetal mortality in this disease.

Human Embryonic Stem Cells Passaged Using Enzymatic Methods Retain a Normal Karyotype and Express CD30

Human embryonic stem cells (hESCs) are thought to be susceptible to chromosomal rearrangements as a consequence of single cell dissociation. Compared in this study are two methods of dissociation that do not generate single cell suspensions (collagenase and EDTA) with an enzymatic procedure using trypsin combined with the calcium-specific chelator EGTA (TEG), that does generate a single cell suspension, over 10 passages. Cells passaged by single cell dissociation using TEG retained a normal karyotype. However, cells passaged using EDTA, without trypsin, acquired an isochromosome p7 in three replicates of one experiment. In all of the TEG, collagenase and EDTA-treated cultures, cells retained consistent telomere length and potentiality, demonstrating that single cell dissociation can be used to maintain karyotypically and phenotypically normal hESCs. However, competitive genomic hybridization revealed that subkaryotypic deletions and amplifications could accumulate over time, reinforcing that present culture regimes remain suboptimal. In all cultures the cell surface marker CD30, reportedly expressed on embryonal carcinoma but not karyoptically normal ESCs, was expressed on hESCs with both normal and abnormal karyotype, but was upregulated on the latter.

Galectin-3 regulates hepatic progenitor cell expansion during liver injury

Objective Following chronic liver injury or when hepatocyte proliferation is impaired, ductular reactions containing hepatic progenitor cells (HPCs) appear in the periportal regions and can regenerate the liver parenchyma. HPCs exist in a niche composed of myofibroblasts, macrophages and laminin matrix. Galectin-3 (Gal-3) is a β-galactoside-binding lectin that binds to laminin and is expressed in injured liver in mice and humans. Design We examined the role of Gal-3 in HPC activation. HPC activation was studied following dietary induced hepatocellular (choline-deficient ethionine-supplemented diet) and biliary (3,5-diethoxycarbonyl-1,4-dihydrocollidine supplemented diet) injury in wild type and Gal-3(−/−) mice. Results HPC proliferation was significantly reduced in Gal-3(−/−) mice. Gal-3(−/−) mice failed to form a HPC niche, with reduced laminin formation. HPCs isolated from wild type mice secrete Gal-3 which enhanced adhesion and proliferation of HPCs on laminin in an undifferentiated form. These effects were attenuated in Gal3(−/−) HPCs and in wild type HPCs treated with the Gal-3 inhibitor lactose. Gal-3(−/−) HPCs in vitro showed increased hepatocyte function and prematurely upregulated both biliary and hepatocyte differentiation markers and regulated cell cycle genes leading to arrest in G0/G1. Conclusions We conclude that Gal-3 is required for the undifferentiated expansion of HPCs in their niche in injured liver.

Notch3 drives development and progression of cholangiocarcinoma

Significance Clinical outcomes in cholangiocarcinoma (CC) are poor; few patients are candidates for curative resection, and palliative chemotherapy produces only modest effects on survival. With an increasing incidence, new targets are urgently needed. Notch has been identified as having potential to induce CC when transgenically overexpressed, and this study aimed to characterize how endogenous Notch might drive tumorigenesis. We identify the atypical receptor Notch3 as differentially overactivated in CCs in humans, rats, and mice, with genetic deletion significantly reducing CC growth. Notch3 sustains tumor cell survival through PI3k/Akt activation via a noncanonical mechanism independent of Recombinant Signal Binding Protein for Immunoglobulin Kappa J Region (RBPJ), presenting an opportunity to target the pathway without disrupting classical Notch and bypassing toxicities associated with γ-secretase inhibitors. The prognosis of cholangiocarcinoma (CC) is dismal. Notch has been identified as a potential driver; forced exogenous overexpression of Notch1 in hepatocytes results in the formation of biliary tumors. In human disease, however, it is unknown which components of the endogenously signaling pathway are required for tumorigenesis, how these orchestrate cancer, and how they can be targeted for therapy. Here we characterize Notch in human-resected CC, a toxin-driven model in rats, and a transgenic mouse model in which p53 deletion is targeted to biliary epithelia and CC induced using the hepatocarcinogen thioacetamide. We find that across species, the atypical receptor NOTCH3 is differentially overexpressed; it is progressively up-regulated with disease development and promotes tumor cell survival via activation of PI3k-Akt. We use genetic KO studies to show that tumor growth significantly attenuates after Notch3 deletion and demonstrate signaling occurs via a noncanonical pathway independent of the mediator of classical Notch, Recombinant Signal Binding Protein for Immunoglobulin Kappa J Region (RBPJ). These data present an opportunity in this aggressive cancer to selectively target Notch, bypassing toxicities known to be RBPJ dependent.