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BackgroundOrganoids, as near-physiological 3D culture systems, offer new opportunities to study the pathogenesis of various organs in mimicking the cellular complexity and functionality of human organs.MethodHere we used a quite simple and very practicable method to successfully generate induced pluripotent stem cell (iPSC)-derived human lung organoids (LuOrg) in a matrix-free manner as an alternative to the widely used preclinical mouse models in order to investigate normal lung damage in detail and as close as possible to the patient. We performed detailed morphological and molecular analyses, including bulk and single cell RNA sequencing, of generated lung organoids and evaluated the quality and robustness of our model as a potential in vitro platform for lung diseases, namely radiation-induced lung injury.ResultsA matrix-free method for differentiation of iPSCs can be used to obtain lung organoids that morphologically reflect the target tissue of the human lung very well, especially with regard to the cellular composition. The different cellular fates were investigated following the genotoxic stress induced by radiation and revealed further insights in the radiation-sensitivity of the different lung cells. Finally, we provide cellular gene sets found to be induced in the different lung organoid cellular subsets after irradiation, which could be used as additional RT response and particularly senescence gene sets in future studies.ConclusionBy establishing these free-floating LuOrgs for the investigation of cancer therapeutic approaches as a new and patient-oriented in vitro platform particularly in experimental radiooncology, not only a reduction in the number of experimental animals, but also an adequately and meaningfully replacement of corresponding animal experiments can be achieved.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13287-024-04106-3. Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1186/s13287-024-04106-3.

Human-induced pluripotent stem cell (iPSC)-derived hepatocyte-like cells (HLCs) have been shown to be useful for the development of cell-based regenerative strategies and for modelling drug discovery. However, stem cell-derived HLCs are not identical in nature to primary human hepatocytes (PHHs), which could affect the cell phenotype and, potentially, model reliability. Therefore, we employed the in-depth gene expression profiling of HLCs and other important and relevant cell types, which led to the identification of clear similarities and differences between them at the transcriptional level. Through gene set enrichment analysis, we identified that genes that are critical for immune signalling pathways become downregulated upon HLC differentiation. Our analysis also found that TAV.HLCs exhibit a mild gene signature characteristic of acute lymphoblastic leukaemia, but not other selected cancers. Importantly, HLCs present significant similarity to PHHs, making them genuinely valuable for modelling human liver biology in vitro and for the development of prototype cell-based therapies for pre-clinical testing.

Fibroblast growth factors (FGFs) control organ morphogenesis during development as well as tissue homeostasis and repair in the adult organism. Despite their importance, many mechanisms that regulate FGF function are still poorly understood. Interestingly, the thermodynamic stability of 22 mammalian FGFs varies widely, with some FGFs remaining stable at body temperature for more than 24 h, while others lose their activity within minutes. How thermodynamic stability contributes to the function of FGFs during development remains unknown. Here we show that FGF10, an important limb and lung morphogen, exists as an intrinsically unstable protein that is prone to unfolding and is rapidly inactivated at 37?°C. Using rationally driven directed mutagenesis, we have developed several highly stable (STAB) FGF10 variants with a melting temperature of over 19?°C more than that of wildtype FGF10. In cellular assays in vitro, the FGF10-STABs did not differ from wildtype FGF10 in terms of binding to FGF receptors, activation of downstream FGF receptor signaling in cells, and induction of gene expression. In mouse embryonal lung explants, FGF10-STABs, but not wildtype FGF10, suppressed branching, resulting in increased alveolarization and expansion of epithelial tissue. Similarly, FGF10-STAB1, but not FGF10 wildtype, inhibited the growth of mouse embryonic tibias and markedly altered limb morphogenesis when implanted into chicken limb buds, collectively demonstrating that thermal instability should be considered an important regulator of FGF function that prevents ectopic signaling. Furthermore, we show enhanced differentiation of human iPSC-derived lung organoids and improved regeneration in ex vivo lung injury models mediated by FGF10-STABs, suggesting an application in cell therapy.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00018-025-05681-1.

SummaryCardiac fibrosis is a key characteristic of heart failure. CTPR390, an experimental anti-fibrotic inhibitor targeting Hsp90, has shown success in animal models, but remains unexplored in human cardiac models. This study evaluated an engineered cardiac connective tissue (ECCT) model, focusing on changes in the extracellular matrix and fibroblasts. Results showed that CTPR390 prevented architectural changes in TGF?1-activated ECCT, preserving tissue perimeter, collagen fibers alignment while reducing structured areas and degree of collagen structuration. CTPR390 treatment reduced cell area of fibroblasts under tension, without changes in the internal rounded cells devoid of tension. Fibroblast recruitment to tension areas was diminished, showing biomechanical behavior similar to control ECCT. This treatment also lowered the gene and protein expression of key pro-fibrotic markers. Here, advanced biotechnology was employed to detect the detailed structure of tissue fibrosis reduction after administering CTPR390, representing a significant advancement toward clinical application for cardiac fibrosis treatment. Graphical abstract Highlights•CTPR390 prevented architectural changes in TGF?1-activated ECCT•CTPR390 preserves tissue perimeter, collagen fibers alignment•CTPR390 reduces structured areas and degree of collagen structuration•CTPR390-trested ECCTs presented a biomechanical behavior similar to control ECCT Molecular biology; Cell biology

Fragile X Syndrome (FXS) is a neurological disorder caused by epigenetic silencing of the FMR1 gene. Reactivation of FMR1 is a potential therapeutic approach for FXS that would correct the root cause of the disease. Here, using a candidate-based shRNA screen, we identify nine epigenetic repressors that promote silencing of FMR1 in FXS cells (called FMR1 Silencing Factors, or FMR1- SFs). Inhibition of FMR1-SFs with shRNAs or small molecules reactivates FMR1 in cultured undifferentiated induced pluripotent stem cells, neural progenitor cells (NPCs) and post-mitotic neurons derived from FXS patients. One of the FMR1-SFs is the histone methyltransferase EZH2, for which an FDA-approved small molecule inhibitor, EPZ6438 (also known as tazemetostat), is available. We show that EPZ6438 substantially corrects the characteristic molecular and electrophysiological abnormalities of cultured FXS neurons. Unfortunately, EZH2 inhibitors do not efficiently cross the blood-brain barrier, limiting their therapeutic use for FXS. Recently, antisense oligonucleotide (ASO)-based approaches have been developed as effective treatment options for certain central nervous system disorders. We therefore derived efficacious ASOs targeting EZH2 and demonstrate that they reactivate FMR1 expression and correct molecular and electrophysiological abnormalities in cultured FXS neurons, and reactivate FMR1 expression in human FXS NPCs engrafted within the brains of mice. Collectively, our results establish EZH2 inhibition in general, and EZH2 ASOs in particular, as a therapeutic approach for FXS.