Characterization of genetically engineered mouse hepatoma cells with inducible liver functions by overexpression of liver-enriched transcription factors

Transplantable cell-encapsulation device using a semipermeable ethylene-vinyl alcohol copolymer membrane in a mouse diabetic model

Cell-based therapy is an attractive approach, and encapsulation of therapeutic cells is a promising strategy because it prevents immune responses and allows transplanted cells to be retrieved in case of dysfunction. Bioartificial pancreas, in which insulin-secreting cells are encapsulated in a semipermeable membrane bag, is a new class of medical device for treating type-I diabetes. In this study, we developed a macroencapsulation device in which the pancreatic beta cell line MIN6 was encapsulated in a semipermeable bag made of an ethylene-vinyl alcohol copolymer membrane. In vitro evaluation of ATP and insulin levels revealed that MIN6 cells grown in Matrigel within the device secreted insulin in response to glucose levels. Transplantation of the device lowered blood glucose levels for 30 days in diabetic mice. Histological observation revealed that MIN6 cells formed spheroids in Matrigel, and no host cells were detected within the device. Blood levels of inflammatory cytokines in the transplanted mice were similar to those in non-transplanted mice, and antibody levels in the device were lower than those in the intraperitoneal fluid. These results suggest that the semipermeable ethylene-vinyl alcohol copolymer membrane developed in this study is useful for cell encapsulation in cell-based therapies, including beta-cell macroencapsulation for type-1 diabetes.

Determining the metabolic effects of dietary fat, sugars and fat-sugar interaction using nutritional geometry in a dietary challenge study with male mice

The metabolic effects of sugars and fat lie at the heart of the "carbohydrate vs fat" debate on the global obesity epidemic. Here, we use nutritional geometry to systematically investigate the interaction between dietary fat and the major monosaccharides, fructose and glucose, and their impact on body composition and metabolic health. Male mice (n = 245) are maintained on one of 18 isocaloric diets for 18-19 weeks and their metabolic status is assessed through in vivo procedures and by in vitro assays involving harvested tissue samples. We find that in the setting of low and medium dietary fat content, a 50:50 mixture of fructose and glucose (similar to high-fructose corn syrup) is more obesogenic and metabolically adverse than when either monosaccharide is consumed alone. With increasing dietary fat content, the effects of dietary sugar composition on metabolic status become less pronounced. Moreover, higher fat intake is more harmful for glucose tolerance and insulin sensitivity irrespective of the sugar mix consumed. The type of fat consumed (soy oil vs lard) does not modify these outcomes. Our work shows that both dietary fat and sugars can lead to adverse metabolic outcomes, depending on the dietary context. This study shows how the principles of the two seemingly conflicting models of obesity (the "energy balance model" and the "carbohydrate insulin model") can be valid, and it will help in progressing towards a unified model of obesity. The main limitations of this study include the use of male mice of a single strain, and not testing the metabolic effects of fructose intake via sugary drinks, which are strongly linked to human obesity.

Hepatogenesis and hepatocarcinogenesis: Alignment of the main signaling pathways

Development is a symphony of cells differentiation in which different signaling pathways are orchestrated at specific times and periods to form mature and functional cells from undifferentiated cells. The similarity of the gene expression profile in malignant and undifferentiated cells is an interesting topic that has been proposed for many years and gave rise to the differentiation-therapy concept, which appears a rational insight and should be reconsidered. Hepatocellular carcinoma (HCC), as the sixth common cancer and the third leading cause of cancer death worldwide, is one of the health-threatening complications in communities where hepatotropic viruses are endemic. Sedentary lifestyle and high intake of calories are other risk factors. HCC is a complex condition in which various dimensions must be addressed, including heterogeneity of cells in the tumor mass, high invasiveness, and underlying diseases that limit the treatment options. Under these restrictions, recognizing, and targeting common signaling pathways during liver development and HCC could expedite to a rational therapeutic approach, reprograming malignant cells to well-differentiated ones in a functional state. Accordingly, in this review, we highlighted the commonalities of signaling pathways in hepatogenesis and hepatocarcinogenesis, and comprised an update on the current status of targeting these pathways in laboratory studies and clinical trials.

HepG2-Based Designer Cells with Heat-Inducible Enhanced Liver Functions

Functional human hepatocytes have been a pivotal tool in pharmacological studies such as those investigating drug metabolism and hepatotoxicity. However, primary human hepatocytes are difficult to obtain in large quantities and may cause ethical problems, necessitating the development of a new cell source to replace human primary hepatocytes. We previously developed genetically modified murine hepatoma cell lines with inducible enhanced liver functions, in which eight liver-enriched transcription factor (LETF) genes were introduced into hepatoma cells as inducible transgene expression cassettes. Here, we establish a human hepatoma cell line with heat-inducible liver functions using HepG2 cells. The genetically modified hepatoma cells, designated HepG2/8F_HS, actively proliferated under normal culture conditions and, therefore, can be easily prepared in large quantities. When the expression of LETFs was induced by heat treatment at 43 °C for 30 min, cells ceased proliferation and demonstrated enhanced liver functions. Furthermore, three-dimensional spheroid cultures of HepG2/8F_HS cells showed a further increase in liver functions upon heat treatment. Comprehensive transcriptome analysis using DNA microarrays revealed that HepG2/8F_HS cells had enhanced overall expression of many liver function-related genes following heat treatment. HepG2/8F_HS cells could be useful as a new cell source for pharmacological studies and for constructing bioartificial liver systems.

Impact of dietary carbohydrate type and protein-carbohydrate interaction on metabolic health

Reduced protein intake, through dilution with carbohydrate, extends lifespan and improves mid-life metabolic health in animal models. However, with transition to industrialised food systems, reduced dietary protein is associated with poor health outcomes in humans. Here we systematically interrogate the impact of carbohydrate quality in diets with varying carbohydrate and protein content. Studying 700 male mice on 33 isocaloric diets, we find that the type of carbohydrate and its digestibility profoundly shape the behavioural and physiological responses to protein dilution, modulate nutrient processing in the liver and alter the gut microbiota. Low (10%)-protein, high (70%)-carbohydrate diets promote the healthiest metabolic outcomes when carbohydrate comprises resistant starch (RS), yet the worst outcomes were with a 50:50 mixture of monosaccharides fructose and glucose. Our findings could explain the disparity between healthy, high-carbohydrate diets and the obesogenic impact of protein dilution by glucose-fructose mixtures associated with highly processed diets.

Development of a genetically modified hepatoma cell line with heat-inducible high liver function

Hepatoma cells are a promising cell source for the construction of bioartificial liver (BAL) systems owing to their high proliferative capability. However, their low liver function compared with primary hepatocytes is a major problem. In a previous study, we established a genetically modified hepatoma cell line, Hepa/8F5, in which eight liver-enriched transcription factor (LETF) genes were transduced into mouse hepatoma Hepa1-6 cells using a drug-inducible transactivator system. These cells proliferate actively under normal culture conditions, meaning that large quantities can be prepared easily. When the overexpression of the LETFs is induced by the addition of an inducer drug, cell growth stops and cell morphology changes with concomitant high expression of liver functions. However, the liver functions largely depend on the presence of the inducer drug, which must be continuously added to maintain these enhanced functions. In the present study, we attempted to modify the method of induction of LETF overexpression in Hepa/8F5 cells to remove the requirement for continual drug addition. To this end, we constructed a system in which the artificial transactivator was transcribed and amplified under the control of a heat-shock protein promoter, and introduced the system into the genome of Hepa/8F5 cells. In our modified cell line, heat-triggered LETF expression was confirmed to induce high liver function. After drug-screening of transfected cells, we established a hepatoma cell line (Hepa/HS), which exhibited high, heat-inducible liver functions. The Hepa/HS cells may represent a new cell source for hepatic studies such as the construction of BAL systems.

Supplementary Information

The online version of this article (10.1007/s10616-021-00457-4) contains supplementary material, which is available to authorized users.

A bioartificial liver device based on three-dimensional culture of genetically engineered hepatoma cells using hollow fibers

The bioartificial liver (BAL) device is an extracorporeal liver support system incorporating living hepatocytes. A major problem in BAL device development is to obtain a high number of functional cells. In this study, we focused on a genetically engineered mouse hepatoma cell line, Hepa/8F5, in which elevated liver functions are induced via overexpression of liver-enriched transcription factors activated by doxycycline (Dox) addition. We applied a three-dimensional culture technique using hollow fibers (HFs) to Hepa/8F5 cells. Hepa/8F5 cells responded to Dox addition by reducing their proliferative activity and performing liver-specific functions of ammonia removal and albumin secretion. The functional activities of cells depended on the timing of Dox addition. We also found that Hepa/8F5 cells in the HF culture were highly functional in a low rather than high cell density environment. We further fabricated an HF-type bioreactor with immobilized Hepa/8F5 cells as a BAL device. Although ammonia removal activity of this BAL device was lower than that of the small-scale HF bundle, albumin secretion activity was slightly higher. These results indicated that the BAL device with immobilized Hepa/8F5 cells was highly functional with potential to show curative effects in liver failure treatment.