Generation of Novel Chimeric Mice with Humanized Livers by Using Hemizygous cDNA-uPA/SCID Mice

Abstract

We have used homozygous albumin enhancer/promoter-driven urokinase-type plasminogen activator/severe combined immunodeficient (uPA/SCID) mice as hosts for chimeric mice with humanized livers. However, uPA/SCID mice show four disadvantages: the human hepatocytes (h-heps) replacement index in mouse liver is decreased due to deletion of uPA transgene by homologous recombination, kidney disorders are likely to develop, body size is small, and hemizygotes cannot be used as hosts as more frequent homologous recombination than homozygotes. To solve these disadvantages, we have established a novel host strain that has a transgene containing albumin promoter/enhancer and urokinase-type plasminogen activator cDNA and has a SCID background (cDNA-uPA/SCID). We applied the embryonic stem cell technique to simultaneously generate a number of transgenic lines, and found the line with the most appropriate levels of uPA expression—not detrimental but with a sufficiently damaged liver. We transplanted h-heps into homozygous and hemizygous cDNA-uPA/SCID mice via the spleen, and monitored their human albumin (h-alb) levels and body weight. Blood h-alb levels and body weight gradually increased in the hemizygous cDNA-uPA/SCID mice and were maintained until they were approximately 30 weeks old. By contrast, blood h-alb levels and body weight in uPA/SCID chimeric mice decreased from 16 weeks of age onwards. A similar decrease in body weight was observed in the homozygous cDNA-uPA/SCID genotype, but h-alb levels were maintained until they were approximately 30 weeks old. Microarray analyses revealed identical h-heps gene expression profiles in homozygous and hemizygous cDNA-uPA/SCID mice were identical to that observed in the uPA/SCID mice. Furthermore, like uPA/SCID chimeric mice, homozygous and hemizygous cDNA-uPA/SCID chimeric mice were successfully infected with hepatitis B virus and C virus. These results indicate that hemizygous cDNA-uPA/SCID mice may be novel and useful hosts for producing chimeric mice for use in future long-term studies, including hepatitis virus infection analysis or drug toxicity studies.

Usefulness of humanized cDNA-uPA/SCID mice for the study of hepatitis B virus and hepatitis C virus virology

“…5b). A prior study showed that cDNA-uPA/SCID chimeric mice have fewer kidney disorders, higher body weights and a higher survival rate than uPA/SCID chimeric mice at week 28 [16]. The present study also showed a higher survival rate in cDNA-uPA/SCID mice than in uPA/ SCID mice 8 weeks after HCV infection [92.1 % (164 out of 168) vs 84.8 % (151 out of 198)].…”

“…Generation of uPA+/+/SCID+/+ mice (uPA/SCID) and cDNA-uPA/SCID mice and transplantation of human hepatocytes were performed as described previously [8,16]. All animal protocols described in this study were performed in accordance with the guidelines of the local committee for animal experiments, and all animals received humane care.…”

“…In addition, hemizygotes cannot be used as hosts [7]. To overcome these problems, cDNA-uPA/SCID mice containing uPA cDNA were developed [16]. The cDNA with the albumin promoter/enhancer and uPA shows no loss of uPA due to deletion of transgenes.…”

Assessment of amiodarone-induced phospholipidosis in chimeric mice with a humanized liver

“…Chimeric mice (PXB mice ® , PhoenixBio Co. Ltd., Hiroshima, Japan) were prepared by transplantation of commercially available human hepatocytes into cDNAurokinase-type plasminogen activator-transgenic severe combined immunodeficient mice (cDNA-uPA wild/+ /SCID, Tateno et al, 2015a). We used chimeric mice (male, 11 to 12-week old) with the middle replacement index (RI) of human hepatocytes (60.8-65.4%), in which the occupancy ratio of the human hepatic region to the total area was estimated based on the human albumin concentration in the blood.…”

“…We succeeded in producing chimeric mice with a humanized liver composed of approximately > 70% human hepatocytes stably (Tateno et al, 2004(Tateno et al, , 2015a, which will likely become a useful animal model to predict drug-induced hepatotoxicity in humans. For example, increased serum alanine aminotransferase (ALT) levels in response to troglitazone were observed in chimeric mice (Kakuni et al, 2012).…”