In vitro characterization of 3D culture-based differentiation of human liver stem cells

Authors:
Marta Tapparo , Gabriele Saccu , Chiara Pasquino , Valentina Fonsato , Claudio Medana , Valentina Schiavo , Enrica Mecarelli , Monica Maccagno , Lorenzo Silengo , Stefania Bruno , Giovanni Camussi , Maria Beatriz Herrera Sanchez 
In:
Source: Frontiers in Pharmacology
Publication Date: (2024)
Issue: 12: 1352013
Research Area:
Stem Cells
Toxicology
Drug Discovery
Cells used in publication:
HaCaT
Species: human
Tissue Origin: dermal
Hep G2
Species: human
Tissue Origin: liver
Hepatocyte, human
Species: human
Tissue Origin: liver
Culture Media:
Experiment

Indocyanine green (ICG) (ICG, USP, Frederick, MD, United States) was dissolved in DMSO at 33 mg/mL and added to alpha MEM (without Phenol red, Lonza, Basel) to a final concentration of 0.5 mg/mL. The cells or aggregates were incubated with ICG at 37°C for 60 min. After incubation, the medium with ICG was blocked with FCS and discarded. The cells or aggregates were washed three times with PBS and examined under the microscope to check for cellular uptake of ICG. Representative images were taken using the Moticam BTX8 Camera (Motic, Xiamen, China). The quantification of ICG uptake was performed by lysing the aggregates or cells with 400 µL of RIPA buffer and measuring the absorbance at 750 nm with a plate reader (iMark Microplate reader, Bio-Rad). The ICG concentration was calculated by plotting a concentration vs. absorbance standard curve of ICG. Measurements were performed in duplicates. HaCaT and non-differentiated HLSC were used as negative control, while hepatocytes (Lonza) were used as a positive control.

Abstract

Introduction: The lack of functional hepatocytes poses a significant challenge for drug safety testing and therapeutic applications due to the inability of mature hepatocytes to expand and their tendency to lose functionality in vitro. Previous studies have demonstrated the potential of Human Liver Stem Cells (HLSCs) to differentiate into hepatocyte-like cells within an in vitro rotary cell culture system, guided by a combination of growth factors and molecules known to regulate hepatocyte maturation. In this study, we employed a matrix multi-assay approach to comprehensively characterize HLSC differentiation. Methods: We evaluated the expression of hepatic markers using qRT-PCR, immunofluorescence, and Western blot analysis. Additionally, we measured urea and FVIII secretion into the supernatant and developed an updated indocyanine green in vitro assay to assess hepatocyte functionality. Results: Molecular analyses of differentiated HLSC aggregates revealed significant upregulation of hepatic genes, including CYP450, urea cycle enzymes, and uptake transporters exclusively expressed on the sinusoidal side of mature hepatocytes, evident as early as 1 day post-differentiation. Interestingly, HLSCs transiently upregulated stem cell markers during differentiation, followed by downregulation after 7 days. Furthermore, differentiated aggregates demonstrated the ability to release urea and FVIII into the supernatant as early as the first 24 h, with accumulation over time. Discussion: These findings suggest that a 3D rotation culture system may facilitate rapid hepatic differentiation of HLSCs. Despite the limitations of this rotary culture system, its unique advantages hold promise for characterizing HLSC GMP batches for clinical applications.