Neohepatocytes from alcoholics and controls express hepatocyte markers and display reduced fibrogenic TGF-ß/Smad3 signaling: advantage for cell transplantation?

Development of Scaffolds with Adjusted Stiffness for Mimicking Disease-Related Alterations of Liver Rigidity

Drug-induced liver toxicity is one of the most common reasons for the failure of drugs in clinical trials and frequent withdrawal from the market. Reasons for such failures include the low predictive power of in vivo studies, that is mainly caused by metabolic differences between humans and animals, and intraspecific variances. In addition to factors such as age and genetic background, changes in drug metabolism can also be caused by disease-related changes in the liver. Such metabolic changes have also been observed in clinical settings, for example, in association with a change in liver stiffness, a major characteristic of an altered fibrotic liver. For mimicking these changes in an in vitro model, this study aimed to develop scaffolds that represent the rigidity of healthy and fibrotic liver tissue. We observed that liver cells plated on scaffolds representing the stiffness of healthy livers showed a higher metabolic activity compared to cells plated on stiffer scaffolds. Additionally, we detected a positive effect of a scaffold pre-coated with fetal calf serum (FCS)-containing media. This pre-incubation resulted in increased cell adherence during cell seeding onto the scaffolds. In summary, we developed a scaffold-based 3D model that mimics liver stiffness-dependent changes in drug metabolism that may more easily predict drug interaction in diseased livers.

Pluripotency gene expression and growth control in cultures of peripheral blood monocytes during their conversion into programmable cells of monocytic origin (PCMO): evidence for a regulatory role of autocrine activin and TGF-β

Previous studies have shown that peripheral blood monocytes can be converted in vitro to a stem cell-like cell termed PCMO as evidenced by the re-expression of pluripotency-associated genes, transient proliferation, and the ability to adopt the phenotype of hepatocytes and insulin-producing cells upon tissue-specific differentiation. However, the regulatory interactions between cultured cells governing pluripotency and mitotic activity have remained elusive. Here we asked whether activin(s) and TGF-β(s), are involved in PCMO generation. De novo proliferation of PCMO was higher under adherent vs. suspended culture conditions as revealed by the appearance of a subset of Ki67-positive monocytes and correlated with down-regulation of p21WAF1 beyond day 2 of culture. Realtime-PCR analysis showed that PCMO express ActRIIA, ALK4, TβRII, ALK5 as well as TGF-β1 and the βA subunit of activin. Interestingly, expression of ActRIIA and ALK4, and activin A levels in the culture supernatants increased until day 4 of culture, while levels of total and active TGF-β1 strongly declined. PCMO responded to both growth factors in an autocrine fashion with intracellular signaling as evidenced by a rise in the levels of phospho-Smad2 and a drop in those of phospho-Smad3. Stimulation of PCMO with recombinant activins (A, B, AB) and TGF-β1 induced phosphorylation of Smad2 but not Smad3. Inhibition of autocrine activin signaling by either SB431542 or follistatin reduced both Smad2 activation and Oct4A/Nanog upregulation. Inhibition of autocrine TGF-β signaling by either SB431542 or anti-TGF-β antibody reduced Smad3 activation and strongly increased the number of Ki67-positive cells. Furthermore, anti-TGF-β antibody moderately enhanced Oct4A/Nanog expression. Our data show that during PCMO generation pluripotency marker expression is controlled positively by activin/Smad2 and negatively by TGF-β/Smad3 signaling, while relief from growth inhibition is primarily the result of reduced TGF-β/Smad3, and to a lesser extent, activin/Smad2 signaling.

Chunggan extract, a traditional herbal formula, ameliorated alcohol-induced hepatic injury in rat model

AIM: To evaluate protective effects of Chunggan extract (CGX), a traditional herbal formula, under 4 wk of alcohol consumption-induced liver injury.

METHODS: Male Sprague-Dawley Rats were orally administered 30% ethanol daily for 4 wk with or without CGX. The pharmaceutical properties were assessed through liver enzymes, histopathology, fibrogenic cytokines, and alcohol metabolism in hepatic tissues as well as by in vitro experiment using HSC-T6 cells.

RESULTS: Four weeks of alcohol consumption notably increased liver enzymes and malondialdehyde levels in serum and hepatic tissue. CGX not only prevented the collagen deposition determined by histopathology and hydroxyproline content, but also normalized transforming growth factor-beta, platelet-derived growth factor-beta and connective tissue growth factor at the gene expression and protein levels in liver tissue. Moreover, CGX treatment also significantly normalized the abnormal changes in gene expression profiles of extracellular matrix proteins, matrix metalloproteinase and their inhibitors, alcohol metabolism, and inflammatory reactions. In the acetaldehyde-stimulated HSC-T6 cells, CGX considerably inhibited collagen production and normalized fibrogenic cytokines in both gene expression and protein levels.

CONCLUSION: The present study evidenced that CGX has hepatoprotective properties via modulation of fibrogenic cytokines and alcohol metabolism in alcoholic liver injury.

AAV-mediated administration of myostatin pro-peptide mutant in adult Ldlr null mice reduces diet-induced hepatosteatosis and arteriosclerosis

Genetic disruption of myostatin or its related signaling is known to cause strong protection against diet-induced metabolic disorders. The translational value of these prior findings, however, is dependent on whether such metabolically favorable phenotype can be reproduced when myostatin blockade begins at an adult age. Here, we reported that AAV-mediated delivery of a myostatin pro-peptide D76A mutant in adult mice attenuates the development of hepatic steatosis and arteriosclerosis, two common diet-induced metabolic diseases. A single dose of AAV-D76A in adult Ldlr null mice resulted in sustained expression of myostatin pro-peptide in the liver. Compared to vehicle-treated mice, D76A-treated mice gained similar amount of lean and fat mass when fed a high fat diet. However, D76A-treated mice displayed significantly reduced aortic lesions and liver fat, in association with a reduction in hepatic expression of lipogenic genes and improvement in liver insulin sensitivity. This suggests that muscle and fat may not be the primary targets of treatment under our experimental condition. In support to this argument, we show that myostatin directly up-regulated lipogenic genes and increased fat accumulation in cultured liver cells. We also show that both myostatin and its receptor were abundantly expressed in mouse aorta. Cultured aortic endothelial cells responded to myostatin with a reduction in eNOS phosphorylation and an increase in ICAM-1 and VCAM-1 expression.

CONCLUSIONS

AAV-mediated expression of myostatin pro-peptide D76A mutant in adult Ldlr null mice sustained metabolic protection without remarkable impacts on body lean and fat mass. Further investigations are needed to determine whether direct impact of myostatin on liver and aortic endothelium may contribute to the related metabolic phenotypes.

Further characterization of autologous NeoHepatocytes for in vitro toxicity testing

Gold standard for in vitro toxicity tests and drug screenings is primary human hepatocytes (hHeps). Because of their limited availability efforts have been made to provide alternatives, e.g., monocyte-derived NeoHepatocytes. In the past years it has been critically discussed if gaining hepatocyte features is associated with trans-differentiation of monocytes or their activation towards a macrophage phenotype. Generating NeoHepatocytes in the presence of six different human AB sera, fetal calf serum (FCS) or autologous serum showed that yield and quality of NeoHepatocytes is inversely correlated to macrophage activation. Using autologous serum constantly the highest amount of cells with the best metabolic capacity was obtained. Focus of this study was to further analyze bio-transformation capacity of the optimized NeoHepatocytes for use as in vitro toxicity test-system. Treatment of the optimized NeoHepatocytes with two different pro-teratogenic substances with corresponding metabolites and eight known hepatotoxins showed comparable toxicity to hHeps. Bio-transformation rates, assessed by testosterone metabolism, were comparable in both cell types. Our data reveal that use of autologous serum reduced macrophage activation which improved yield and function of NeoHepatocytes resulting in bio-transformation and toxicity profiles comparable to hHeps. Thus, their easy accessibility makes them an ideal candidate for in vitro toxicity studies.

Autologous serum improves yield and metabolic capacity of monocyte-derived hepatocyte-like cells: possible implication for cell transplantation

Hepatocyte-transplantation is a therapeutic approach for diverse acute and chronic liver diseases. As availability of primary cells is limited, there is an increasing demand for hepatocyte-like cells (e.g., neohepatocytes generated from peripheral blood monocytes). The aim of this study was to evaluate the effects of six different human AB sera, fetal calf serum, or autologous serum on production of neohepatocytes. The yield and quality of neohepatocytes varied considerably depending on the different sera. Using autologous sera for the whole production process we constantly generated the highest amount of cells with the highest metabolic activity for phase I (e.g., CYP1A1/2, CYP3A4) and phase II enzymes (e.g., glutathione-S-transferase). Moreover, similar effects were seen examining glucose and urea metabolism. Especially, glucose-6-phosphatase and PAS staining showed distinct serum-dependent differences. The role of macrophage activation was investigated by measuring the secretion of TNF-α, TGF-β, and RANKL, MMP activity, as well as mRNA levels of different interleukins in programmable cells of monocytic origin (PCMO). Our data clearly demonstrate that the use of autologous serum reduced initial macrophage activation in PCMOs and subsequently improved both yield and function of differentiated neohepatocytes. The autologous approach presented here might also be useful in other stem cell preparation processes where cell activation during generation shall be kept to a minimum.