hepatic differentiation of human-induced pluripotent stem cells in 2d cultures

Purification of Human iPSC-Derived Hepatocytes by Mitochondrial-ALCAM Sorting

Embryonic and induced pluripotent stem cells (ES and iPS, respectively) are considered promising cell sources for regenerative therapies. However, the efficiency of differentiating these cells into specific target cell types can vary, even when using the same cell line, protocol, and experimenter1,2,3,4. This variability may be attributed to the high sensitivity of human ES/iPS cells to their environment. Therefore, it is currently difficult to consistently obtain pure target cells. To achieve highly safe regenerative medicine, it is crucial to eliminate proliferative cells and undifferentiated stem cells in therapeutic cells, and advanced purification technology for target cells is essential5,6,7.
A cell sorter is a device that instantaneously analyzes individual cells and sorts live cells of interest based on the fluorescent signal strengths, offering a promising solution. This can be accomplished through antibody staining of cell type-specific surface markers or by utilizing cell type-specific reporter gene expressions. Using this technique, there are several reports on methods for purifying pluripotent stem cell-derived cardiomyocytes8,9,10 and hepatocytes11,12. Hattori et al. developed an innovative mitochondrial purification method using a cell sorter13. Taking advantage of the fact that cardiomyocytes have high energy demands through mitochondrial activity, staining the cells with the live mitochondria-indicative dye TMRM (tetramethylrhodamine methyl ester) can be used to label and highly purify cardiomyocytes by FACS from human ES cell-derived embryoid bodies containing various cell types. The absence of tumorigenicity was confirmed by teratoma formation assays with the purified cardiomyocytes. Furthermore, Yamashita et al. unexpectedly discovered a method to purify hepatocytes from human ES cell-derived embryoid bodies by isolating fractions with high mitochondrial activity and ALCAM-positive expression14. The rationale for this method is that hepatocytes also have a relatively high number of mitochondria due to their high consumption of ATP for nutrient metabolism and detoxification15, and hepatocytes express ALCAM, a member of the immunoglobulin superfamily, which plays a role in cell adhesion and migration16.
Previous highly purifying methods for pluripotent stem cell-derived hepatocytes required genetic modifications, and non-genetic purification methods had low efficiency17. The mitochondrial non-genetic method holds merit for achieving high purity. When hepatic progenitor cells are needed, CD133 and CD13- or Dlk1-based methods18,19 can be chosen. Although the accuracy of genome editing technology has advanced, the potential risk of unforeseen genomic changes (e.g., carcinogenesis) cannot be entirely eliminated. Methods based on mitochondrial activity, without involving genetic modification, can be free from such risks.
As a result of examining various mitochondrial indicators in neonatal rat cardiomyocytes, TMRM was observed to disappear completely within 24 h, whereas other dyes remained for at least 5 days13. Moreover, it is important to note that TMRM and JC-1 did not impact cell viability when assessed with the 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, while other dyes demonstrated varying effects on cell viability13. TMRM demonstrates higher safety.
To date, several two-dimensional (2D) differentiation methods have been developed as more efficient approaches for inducing differentiation compared to three-dimensional (3D) embryoid body formation. This is because step-wise differentiation-inducing compounds or cytokines can be uniformly administered to cells on a 2D plane, rather than in a 3D space. In this study, the previously reported method20 was modified to induce differentiation into human iPS cell-derived hepatocytes. Here, the details of the procedures for the up-to-date 2D differentiation and purification of hepatocytes derived from human iPS cells are described.

Author Spotlight: Advancing Hepatocyte Purification from Human Induced Pluripotent Stem Cells for Regenerative Medicine

Application of Live Mitochondria Staining in Cell-Sorting to Purify Hepatocytes Derived from Human Induced Pluripotent Stem Cells

The scope of our research is to purify human induced pluripotent stem cell-derived hepatocytes, using without genetic modification. We aim to address the issue of the tumorigenic risk associated with the undifferentiated cells, among those differentiated from human iPS cells. One of the current experimental challenges is a low cell purity, due to the mechanical storage of sorting.We are developing a new purification method, that utilizes the unique metabolism features of hepatocytes, for large-scale purification. One non-cell sorting method for hepatic progenitor cells cannot obtain pure hepatocytes. Another one for mature hepatocytes can only treat a small fraction of hepatocytes, because of the limited expression of the marker protein.In contrast, our approach can obtain hepatocytes at different maturation levels with a higher eve. Human iPS cell-derived hepatocytes are extremely immature, and show more reduced hepatocyte macro expression after purification. Our future goal is to enhance hepatocyte modulation using organoidal technology and day-to-day advancements to regenerative medicine and drug discovery.

Hepatic Differentiation of Human-Induced Pluripotent Stem Cells in 2D Cultures

To begin, coat each well of a six-well plate with one milliliter of basement membrane matrix and incubate at 37 degrees Celsius for one hour. Remove the coated matrix from the plate and add human-induced pluripotent stem cells prepared in AK02N medium supplemented with 10 micromolar ROCK inhibitor. Incubate the cells at 37 degrees Celsius and 5%carbon dioxide for three days.After three days, on day zero of the initiating hepatic differentiation, wash the cells once with RPMI 1640 medium. Next, to initiate endoderm differentiation, add RPMI B27 GlutaMAX supplemented with three to six micromolar CHIR 99021 and 100 nanograms per milliliter Activin A into the plate. Incubate the cells at 37 degrees Celsius and 5%carbon dioxide for 24 hours.On day one, replace the existing medium with RPMI B27 GlutaMAX supplemented with 50 nanograms per milliliter of Activin A.Incubate the cells at 37 degrees Celsius and 5%carbon dioxide for 24 hours. On day two, to induce hepatic progenitor differentiation, replace the existing medium with RPMI B27 GlutaMAX medium supplemented with 1%dimethyl sulfoxide, and continue incubation for up to five days. On day seven, to initiate hepatocyte maturation, switch to hepatocyte maturation medium and incubate for 20 days at 37 degrees Celsius and 5%carbon dioxide.On day 27, human-induced pluripotent stem cells displayed polygonal cell shapes and rounded nuclei, characteristics of hepatocytes.

Research

JoVE Journal

Biology

Human embryonic stem (ES) and induced pluripotent stem (iPS) cells have potential applications in cell-based regenerative medicine for treating severely ...