The American Association for the Study of Liver Diseases (AASLD) has selected ISCO's presentation, titled "Human parthenogenetic stem cell-derived hepatocyte transplantation controls serum bilirubin in Gunn rats" as a Presidential Poster of Distinction at The Liver Meeting, AASLD'S 64th Annual Meeting in Washington,DC,Novemberl-November5,2013
The presentation authors are Dr. Alina Ostrowska, Dr. Larisa Agapova, Tiffany Chu, Dr. Trudy Christiansen-Weber and Dr. Ruslan Semechkin all of International Stem Cell Corporation, Carlsbad, CA, USA
Background:
Extensive studies indicate that pluripotent stem cells are a highly promising
alternative source of histocompatible cells for cell replacement therapy.
Hepatocyte-like cells (HLCs) derived from human parthenogenetic stem cells
(hpSCs) might be transplanted to treat a wide array of metabolic liver diseases including CN1
(Crigler-Najjar syndrome type I). CN1 is the paradigm of
inherited liver-based metabolic disorders in that the host liver is lacking one
hepatic enzyme - UGT1A1, which is essential for the conjugation and excretion
of bilirubin. To obtain ultimate proof that differentiation has been achieved,
following the preliminary evaluation in
vitro, we tested hepatocyte-like cells in
vivo using an accurate animal model of CN1, the Gunn rats which accumulate
toxic plasma levels of unconjugated bilirubin. Methods: Highly enriched populations of definitive endoderm were
generated from hpSCs in a novel 3D-differentiation system and then induced to
differentiate towards HLCs. The final cells were characterized by using
expression profiling including RT-qPCR for dynamic expression of the hepatic
lineage genes, immunohistochemistry and FACS analysis to demonstrate
hepatocyte-specific markers, drug metabolism assays to determine the activity
of CYP450s as well as a luminescent method for measuring UGT activity profile. Production
of liver-specific proteins in the culture medium was simultaneously measured by
quantitative ELISA. To evaluate engraftment and functional repopulation in
vivo, CFSE-labeled hpHC were injected (10x106 per animal) into
the spleen of 4-6 week old Gunn rats. Blood serum samples of tested animals
were evaluated for indirect bilirubin levels 4, 8 and 19 weeks
post-transplantation. Liver tissue samples were embedded in OCT compound and
snap frozen, until cryosectioning. Results:
CFSE-labeled HLCs transferred into the spleen were shown to migrate into the
liver. Multiple engrafted cells were observed in the periportal regions of the
liver lobules and formed morphologically distinct aggregates. The overall liver
structure appeared undamaged without signs of inflammation, fibrosis or tumor.
Significant decrease and long-term stabilization of bilirubin levels was
demonstrated in the serum of tested animals in comparison with sham-treated
controls. Although by week 19th serum indirect bilirubin was not
normalized in transplanted animals, it resulted in an average 70% reduction
compared with pretreatment levels. Conclusion:
This pre-clinical study describes important supportive evidence of the potential
efficacy and safety of hpSC-derived hepatocytes which might constitute an
easily available source to obtain a large number of transplantable cells for
regenerative treatments of CN1. In the long-term,
experience with HLCs transplantation for CN1 can be used to develop therapeutic
strategies for more common inherited liver diseases.
