Transgenic pig expressing the red fluorescent protein kusabira-orange as a novel tool for preclinical studies on hepatocyte transplantation

Study of the Potential Hepatoprotective Effect of Myo-Inositol and Its Influence on Zebrafish Development

Inositol is a natural substance found widely in plants. It is used in therapies for many medical cases. The aim of this study was to determine the toxicity of myo-inositol (MI) and to investigate its potential hepatoprotective character. In the first part of the study, zebrafish embryos were incubated with 5, 10, 20, 40, 60, 80, and 100 mg/mL MI. Endpoints such as survivability, hatching rate, malformation, and mobility were evaluated. Our results demonstrated that the high doses of MI lead to increased mortality and malformations and reduce the hatching rate in comparison to the control group. Moreover, low doses of this compound do not produce a negative effect on zebrafish and even have the ability to increase the hatching rate and mobility. In the second part of the study, the hepatoprotective effect of MI was tested. Zebrafish larvae from the line Tg (fabp10a:DsRed) were incubated for 24 h with 1% and 2% ethanol (EtOH), 5 mg/mL of MI with 1% EtOH, and 5 mg/mL of MI with 2% EtOH. No significant differences between the groups with EtOH and the group treated with EtOH with MI were observed. Our results suggest that MI has no positive benefits on hepatocytes of zebrafish larvae.

Natural Flavonol, Myricetin, Enhances the Function and Survival of Cryopreserved Hepatocytes In Vitro and In Vivo

To improve the therapeutic potential of hepatocyte transplantation, the effects of the mitogen-activated protein kinase kinase 4 (MKK4) inhibitor, myricetin (3,3′,4′,5,5′,7-hexahydroxylflavone) were examined using porcine and human hepatocytes in vitro and in vivo. Hepatocytes were cultured, showing the typical morphology of hepatic parenchymal cell under 1–10 µmol/L of myricetin, keeping hepatocyte specific gene expression, and ammonia removal activity. After injecting the hepatocytes into neonatal Severe combined immunodeficiency (SCID) mouse livers, cell colony formation was found at 10–15 weeks after transplantation. The human albumin levels in the sera of engrafted mice were significantly higher in the recipients of myricetin-treated cells than non-treated cells, corresponding to the size of the colonies. In terms of therapeutic efficacy, the injection of myricetin-treated hepatocytes significantly prolonged the survival of ornithine transcarbamylase-deficient SCID mice from 32 days (non-transplant control) to 54 days. Biochemically, the phosphorylation of MKK4 was inhibited in the myricetin-treated hepatocytes. These findings suggest that myricetin has a potentially therapeutic benefit that regulates hepatocyte function and survival, thereby treating liver failure.

Hepatocyte spheroids as an alternative to single cells for transplantation after ex vivo gene therapy in mice and pig models

BACKGROUND

Autologous hepatocyte transplantation after ex vivo gene therapy is an alternative to liver transplantation for metabolic liver disease. Here we evaluate ex vivo gene therapy followed by transplantation of single-cell or spheroid hepatocytes.

METHODS

Pig and mouse hepatocytes were isolated, labeled with zirconium-89 and returned to the liver as single cells or spheroids. Biodistribution was evaluated through positron emission tomography-computed tomography. Fumarylacetoacetate hydrolase-deficient pig hepatocytes were isolated and transduced with a lentiviral vector containing the Fah gene. Animals received portal vein infusion of single-cell or spheroid autologous hepatocytes after ex vivo gene delivery. Portal pressures were measured and ultrasound was used to evaluate for thrombus. Differences in engraftment and expansion of ex vivo corrected single-cell or spheroid hepatocytes were followed through histologic analysis and animals' ability to thrive off 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione.

RESULTS

Positron emission tomography-computed tomography imaging showed spheroid hepatocytes with increased heterogeneity in biodistribution as compared with single cells, which spread more uniformly throughout the liver. Animals receiving spheroids experienced higher mean changes in portal pressure than animals receiving single cells (P < .01). Additionally, two animals from the spheroid group developed portal vein thrombi that required systemic anticoagulation. Immunohistochemical analysis of spheroid- and single-cell-transplanted animals showed similar engraftment and expansion rates of fumarylacetoacetate hydrolase-positive hepatocytes in the liver, correlating with similar weight stabilization curves.

CONCLUSION

Ex vivo gene correction of autologous hepatocytes in fumarylacetoacetate hydrolase-deficient pigs can be performed using hepatocyte spheroids or single-cell hepatocytes, with spheroids showing a more heterogeneous distribution within the liver and higher risks for portal vein thrombosis and increased portal pressures.

Experimental Hepatocyte Transplantation in Pigs

Technical issues of experimental hepatocyte transplantation in pigs, i.e., selection of animals, anesthesia, route of transplantation, and segment-specific transplantation have described.

A transgenic-cloned pig model expressing non-fluorescent modified Plum

Genetically modified pigs that express fluorescent proteins such as green and red fluorescent proteins have become indispensable biomedical research tools in recent years. Cell or tissue transplantation studies using fluorescent markers should be conducted, wherein the xeno-antigenicity of the fluorescent proteins does not affect engraftment or graft survival. Thus, we aimed to create a transgenic (Tg)-cloned pig that was immunologically tolerant to fluorescent protein antigens. In the present study, we generated a Tg-cloned pig harboring a derivative of Plum modified by a single amino acid substitution in the chromophore. The cells and tissues of this Tg-cloned pig expressing the modified Plum (mPlum) did not fluoresce. However, western blot and immunohistochemistry analyses clearly showed that the mPlum had the same antigenicity as Plum. Thus, we have obtained primary proof of principle for creating a cloned pig that is immunologically tolerant to fluorescent protein antigens.

Transgenic pigs with pancreas-specific expression of green fluorescent protein

The development and regeneration of the pancreas is of considerable interest because of the role of these processes in pancreatic diseases, such as diabetes. Here, we sought to develop a large animal model in which the pancreatic cell lineage could be tracked. The pancreatic and duodenal homeobox-1 (Pdx1) gene promoter was conjugated to Venus, a green fluorescent protein, and introduced into 370 in vitro-matured porcine oocytes by intracytoplasmic sperm injection-mediated gene transfer. These oocytes were transferred into four recipient gilts, all of which became pregnant. Three gilts were sacrificed at 47-65 days of gestation, and the fourth was allowed to farrow. Seven of 16 fetuses obtained were transgenic (Tg) and exhibited pancreas-specific green fluorescence. The fourth recipient gilt produced a litter of six piglets, two of which were Tg. The founder Tg offspring matured normally and produced healthy first-generation (G1) progeny. A postweaning autopsy of four 27-day-old G1 Tg piglets confirmed the pancreas-specific Venus expression. Immunostaining of the pancreatic tissue indicated the transgene was expressed in β-cells. Pancreatic islets from Tg pigs were transplanted under the renal capsules of NOD/SCID mice and expressed fluorescence up to one month after transplantation. Tg G1 pigs developed normally and had blood glucose levels within the normal range. Insulin levels before and after sexual maturity were within normal ranges, as were other blood biochemistry parameters, indicating that pancreatic function was normal. We conclude that Pdx1-Venus Tg pigs represent a large animal model suitable for research on pancreatic development/regeneration and diabetes.