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FAQs

Hepatocytes Derived from Human iPS Cells—
Cellartis Enhanced hiPS-HEP

General FAQs

What is the source of Cellartis enhanced hiPS-HEP cells?

Cellartis enhanced hiPS-HEP cells are differentiated from human induced pluripotent stem (hiPS) cell lines ChiPSC12, ChiPSC18, and ChiPSC22. These lines were created by reprogramming human dermal fibroblasts with defective polycistronic retrovirus technology. This includes a retroviral vector containing Oct4, Sox2, Klf4, and c-Myc (pRV-OCT4-SOX2-KLF4-MYC; the vector map is proprietary). Reverse transcriptase activity testing shows that the hiPS cell lines do not contain replication-competent retroviruses. In addition, the viral reprogramming genes are silenced.

What is the difference between a Cellartis enhanced hiPS-HEP v2 kit and the older version?

With Cellartis enhanced hiPS-HEP v2 kits, we are fulfilling a need for longer-lasting, functional, and mature hiPS cell-derived hepatocytes as a better alternative to primary and tumor-based cell models. Cellartis enhanced hiPS-HEP v2 kits contain the same high-performance Cellartis enhanced hiPS-HEP cells as the original kits. Both versions also contain hepatocyte thawing medium, coating, plating medium, and washing medium. However, the newer v2 kits contain long-term maintenance medium for extended culture of enhanced hiPS-HEP cells, ideal for disease modeling and drug discovery experiments.

Are Cellartis enhanced hiPS-HEP cells genetically engineered?

No. In some hepatocytes, genetic engineering is used to improve hepatic function. Instead, we developed a culture protocol that substantially improves functionality. Each hiPS cell line—the source of the Cellartis hepatocytes—was reprogrammed using an integrative, retroviral technique. We tested for reverse transcriptase activity in the hiPS cell lines to confirm the absence of replication-competent retroviruses. We also confirmed that the factors used for reprogramming are silenced in the hiPS cell lines.

Are Cellartis enhanced hiPS-HEP cells available from several hiPS cell lines?

Yes, Cellartis enhanced hiPS-HEP cells are available from three different cell lines: ChiPSC12, ChiPSC18, and ChiPSC22. Hepatocytes derived from different hiPS cell lines model the genetic variation between individuals; therefore, the cells display phenotypic variation.

How soon after thawing Cellartis enhanced hiPS-HEP cells can I begin testing?

High and constant CYP enzyme activities, plus albumin and urea secretion, are detected at Days 4–19 post-thawing. CYP activity is measured by LC/MS 4, 12, and 19 days post-thaw. Albumin and urea secretion is measured by ELISA at 2, 4, 12, and 20 days post-thaw. Both are comparable to human primary hepatocytes 20 hr post-thaw.

Can other maintenance media or coatings be used for culturing Cellartis enhanced hiPS-HEP cells?

We recommend using the provided Cellartis HEP Coat and Cellartis HEP Supplement. The coating and supplement are crucial for optimal performance and results when using Cellartis enhanced hiPS-HEP cells. Other coatings or media can be used, however we cannot guarantee optimal performance. If you have questions or specific requirements regarding media or coating, please contact tech support.

Does Cellartis Enhanced hiPS-HEP Long-Term Maintenance Medium contain dexamethasone, hydrocortisone, and DMSO?

Yes, Cellartis Enhanced hiPS-HEP Long-Term Maintenance Medium contains all three of these components. We have not evaluated the performance of Cellartis enhanced hiPS-HEP cells in the absence of dexamethasone, hydrocortisone, or DMSO.

How do we know Cellartis enhanced hiPS-HEP cells are mature hepatocytes?

To determine the maturity of the cells, we investigated genes known to be expressed in fetal and adult hepatocytes and tested by multiple assays how they compare to primary hepatocytes. We observed high expression and activity of multiple adult hepatocyte markers such as albumin, CYP1A2, CYP2C9, CYP2C19, CYP3A4, HNFα, and ASGPR1. We confirmed this by immunofluorescence, activity, and qPCR analyses. We also observed a low expression level of the fetal gene CYP3A7—similar to the level in primary hepatocytes.

Do Cellartis enhanced hiPS-HEP cells express transporter proteins?

Yes, Cellartis enhanced hiPS-HEP cells express several transporters: BSEP, MRP2, NTCP, OATP1B1, OCT1, and BCRP. Some transporters are expressed at similar levels as cryopreserved human primary hepatocytes; other transporters are expressed at lower levels than cryopreserved human primary hepatocytes.

Do Cellartis enhanced hiPS-HEP cells express phase II enzymes?

Yes, Cellartis enhanced hiPS-HEP cells display phase II enzyme activities, e.g., UGT and sulfotransferase activities, at similar or higher levels as in cryopreserved human primary hepatocytes cultured 24 hours, as measured by LC/MS.

Can CYP expression be induced in Cellartis enhanced hiPS-HEP cells?

The cells have basal CYP enzyme activities that are measured during quality control and presented in the Certificate of Analysis. Minimal CYP induction is observed in Cellartis enhanced hiPS-HEP cells in 2D culture.

Does fetal CYP3A7 contribute to overall CYP activity in these cells?

Whereas a CYP activity assay cannot discriminate between CYP3A4 (adult), CYP3A5 (adult), and CYP3A7 (fetal), qPCR can. Cellartis enhanced hiPS-HEP cells express high mRNA levels of CYP3A4 and CYP3A5 and very low levels of CYP3A7—comparable to cryopreserved human primary hepatocytes cultured for 24 hours. Interestingly, inter-individual variation in CYP expression can be observed in Cellartis enhanced hiPS-HEP cells derived from different hiPS cell lines.

Cellartis enhanced hiPS-HEP cells are >90% pure. Which cell types make up the other 10%?

This subpopulation is likely a mixture of other endodermal cells, but the exact composition is unknown. We start with high-purity endodermal cells in the first step of differentiation, and we confirm through staining that there are no undifferentiated stem cells in the final product.

Can Cellartis enhanced hiPS-HEP cells be used for hepatitis virus research?

Cellartis enhanced hiPS-HEP cells express NTCP transporter, an important entry receptor for hepatitis B virus.

Handling FAQs

How are Cellartis enhanced hiPS-HEP cells shipped?

Cellartis enhanced hiPS-HEP cells are frozen in a cryovial and packaged as a part of a Cellartis enhanced hiPS-HEP v2 kit. This kit also contains the Cellartis Enhanced hiPS-HEP Thawing and Plating Kit and Cellartis Enhanced hiPS-HEP Long-Term Maintenance Medium. All items are shipped together on dry ice.

Which culture vessels are suitable for Cellartis enhanced hiPS-HEP cells?

96-well and 24-well plates are recommended.

Why should the cells be washed on Day 1 after plating?

Washing with Hepatocyte Washing Medium on Day 1 after plating is necessary to remove non-adherent cells. When washing, carefully remove 100% of the media from only a few wells at a time; do not let the wells dry.

Why should partial media changes be performed from Day 3 onward?

Repeated drying, which easily happens when changing 100% of the media, detaches the cells at the edges of the well. Changing only 90% of the media ensures that liquid is always left on the cells, preventing desiccation and detachment. For washing steps in assays or immunocytochemical staining, it is better to leave a small amount of buffer or washing solution on the cells and increase the number of washing steps.

Can Cellartis enhanced hiPS-HEP cells go without changing media over the weekend?

Yes, but add 50% more media on Friday (e.g., 1.5 ml/well of a 24-well plate and 230 µl/well of a 96-well plate). It is best to change the media late on Friday and early on Monday.

Is it possible to proliferate Cellartis enhanced hiPS-HEP cells?

No, Cellartis enhanced hiPS-HEP cells are terminally differentiated hepatocytes that are unable to proliferate.

Do Cellartis enhanced hiPS-HEP cells show formation of bile canaliculi?

We have not been able to show the formation of bile canaliculi in these cells.

How were CYP enzyme activities measured in Cellartis enhanced hiPS-HEP cells?

LC/MS was used to measure the formation of these specific metabolites: Acetaminophen (CYP1A), 4-OH-Diclofenac (CYP2C9), OH-Bufuralol (CYP2D6), and 1-OH-Midazolam (CYP3A). The CYP activities of Cellartis enhanced hiPS-HEP cells were analyzed at Days 4, 12, and 19 after thawing as part of routine quality control. LC/MS analysis was performed at Pharmacelsus GmbH, Germany.

To measure CYP activity, Cellartis enhanced hiPS-HEP cells were washed twice with pre-warmed William medium E (+0.1% PEST). Then, the activity assay was started by adding 110 µl/cm2 culture area of pre-warmed William medium E containing 0.1% PEST, 25 mM HEPES, 2 mM L-Glutamine, and the following probe substrate cocktail:

CYP Substrate Concentration
1A Phenacetin 10 µM
2B6 Bupropion 10 µM
2C9 Diclofenac 10 µM
2D6 Bufuralol 10 µM
3A Midazolam   5 µM

After 2 hr at 37°C, 100 µl of supernatant was collected and kept at –80°C until LC/MS analysis. The metabolite concentrations measured by LC/MS were normalized to the amount of protein per well (determined using the Pierce BCA Protein Assay Kit) and the assay duration (120 min).

I observe droplets in Cellartis enhanced hiPS-HEP cell culture. Is this normal?

ChIP-Seq products

These liquid extrusions are not abnormal. In time-lapse recordings, we have observed that hepatocytes release these drops into the media and remain healthy afterwards. This is not a sign of cell death, and cultures with these drops perform normally in activity assays. We have stained the cultures with Oil Red O and these drops were not stained, indicating that they are not lipid droplets. Although the exact nature of the drops is unknown, cell performance remains intact despite their presence.

I observe dome-like structures in Cellartis enhanced hiPS-HEP cell culture. Is this normal?

ChIP-Seq products

Occasionally, these domes appear but they do not affect overall cell performance. In these structures, the hepatocytes have detached from the coating, possibly because they were growing very densely. Please be careful when changing media by always leaving 10% of the media in each well.

Can you culture Cellartis enhanced hiPS-HEP cells as 3D spheroids?

Yes, we have successfully generated 3D spheroids using ultra-low attachment plates. Spheroids can be maintained for 3–4 weeks in culture.

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