Osmolar Modulation Drives Reversible Cell Cycle Exit and Human Pluripotent Cell Differentiation via NF‐κВ and WNT Signaling

Abstract

Terminally differentiated cells are commonly regarded as the most stable cell state in adult organisms, characterized by growth arrest while fulfilling their specialized functions. A better understanding of the mechanisms involved in promoting cell cycle exit will improve the ability to differentiate pluripotent cells into mature tissues for both pharmacological and therapeutic use. Here, it demonstrates that a hyperosmolar environment enforces a protective p53‐independent quiescent state in immature hepatoma cells and in pluripotent stem cell‐derived models of human hepatocytes and endothelial cells. Prolonged culture in hyperosmolar conditions stimulates changes in gene expression promoting functional cell maturation. Interestingly, hyperosmolar conditions do not only trigger growth arrest and cellular maturation but are also necessary to maintain this maturated state, as switching back to plasma osmolarity reverses the changes in expression of maturation and proliferative markers. Transcriptome analysis revealed sequential stages of osmolarity‐regulated growth arrest followed by cell maturation, mediated by activation of NF‐κВ, and repression of WNT signaling, respectively. This study reveals that a modulated increase in osmolarity serves as a biochemical signal to promote long‐term growth arrest and cellular maturation into different lineages, providing a practical method to generate differentiated hiPSCs that resemble their mature counterpart more closely.

Human iPSC-derived liver co-culture spheroids to model liver fibrosis

“…Medium compositions previously optimized for functionalized hydrogel cultures with similar iPSC-derived liver cells turned out to not have a large impact on maturity of the individual cell types in the spheroid cultures; only the high amino acid and L-Serine concentrations had a significant impact on CYP3A4 levels. Most probably, the hyperosmolar environment created by the L-Serine enforces a protective p53-independent quiescent state in the iPSC-derived hepatocytes, thereby promoting functional maturations (Chui et al 2024). Previous studies have already shown that growth factors can be (partly) replaced by small molecules, leading to successful differentiation of hepatocytes (Siller et al 2015, Pan et al 2022, Vanmarcke et al 2023.…”