Project description:In the earliest step of thymic organogenesis, mesenchymal cells support the growth of thymic epithelial cells (TECs). It is established that TECs and thymocytes influence each other for their growth/differentiation, a process called thymic crosstalk. However, little is known about the influence of developing thymocytes or TECs on mesenchymal cells. Here, we show that during normal thymus development fibroblast ingrowth occurs towards hypoxic areas. Similar overgrowth of mesenchymal cells is seen in a fetal thymic organ culture system under low oxygen conditions. However, when thymocytes were depleted by deoxyguanosine treatment, mesenchymal cells were also induced, precluding the direct effect of hypoxia. In the fetal thymus of hCD3εTg mice, which lack T lineage cells, an overgrowth of mesenchymal cells can be seen at a very early stage of thymic organogenesis. The growth of the mesenchymal cells is due to extensive proliferation and not mere enrichment. With RNA sequencing analysis comparing hCD3εTg with wild type TECs, we identified candidate factors that could be involved in mesenchymal network formation.
Project description:This file contains a 136-node modular Boolean network model of EMT triggered by biomechanical and growth signaling crosstalk, linked to a published network of epithelial contact inhibition, proliferation, and apoptosis (MODEL2006170001). This model reproduces the ability of the core EMT transcriptional network to maintain distinct epithelial, hybrid E/M and mesenchymal states, as well as EMT driven by mitogens such as EGF on stiff ECM. We also reproduce the observed lack of stepwise MET, in that our model's dynamics does not pass through the hybrid E/M state during MET. We show that in the absence of strong autocrine signals such as TGFβ (not included in this version), cells cannot maintain their mesenchymal state in the absence of mitogens, on softer matrices, or at high cell density.
Project description:This model is based on:
Computational Modeling of the Crosstalk Between Macrophage Polarization and Tumor Cell Plasticity in the Tumor Microenvironment.
Abstract:
Tumor microenvironments contain multiple cell types interacting among one another via different signaling pathways. Furthermore, both cancer cells and different immune cells can display phenotypic plasticity in response to these communicating signals, thereby leading to complex spatiotemporal patterns that can impact therapeutic response. Here, we investigate the crosstalk between cancer cells and macrophages in a tumor microenvironment through in silico (computational) co-culture models. In particular, we investigate how macrophages of different polarization (M1 vs. M2) can interact with epithelial-mesenchymal plasticity of cancer cells, and conversely, how cancer cells exhibiting different phenotypes (epithelial vs. mesenchymal) can influence the polarization of macrophages. Based on interactions documented in the literature, an interaction network of cancer cells and macrophages is constructed. The steady states of the network are then analyzed. Various interactions were removed or added into the constructed-network to test the functions of those interactions. Also, parameters in the mathematical models were varied to explore their effects on the steady states of the network. In general, the interactions between cancer cells and macrophages can give rise to multiple stable steady-states for a given set of parameters and each steady state is stable against perturbations. Importantly, we show that the system can often reach one type of stable steady states where cancer cells go extinct. Our results may help inform efficient therapeutic strategies.
Project description:This model is an expansion of the Regan2022 - Mechanosensitive EMT model (MODEL2208050001); it includes a TGFβ signaling module and autocrine signaling in mesenchymal cells. The expanded 150-node (630 link) modular model undergoes EMT triggered by biomechanical and growth signaling crosstalk, or by TGFβ. As its predecessor, this model also reproduces the ability of the core EMT transcriptional network to maintain distinct epithelial, hybrid E/M and mesenchymal states, as well as EMT driven by mitogens such as EGF on stiff ECM. We also reproduce the observed lack of stepwise MET, in that our model's dynamics does not pass through the hybrid E/M state during MET. We show that in the absence of strong autocrine signals such as TGFβ (not included in this version), cells cannot maintain their mesenchymal state in the absence of mitogens, on softer matrices, or at high cell density. In contrast, potent autocrine signaling can stabilize the mesenchymal state in all but very dense monolayers on soft ECM. This expanded model also reproduces the inhibitory effects of TGFβ on proliferation and anoikis resistance in mesenchymal cells, as well as its ability to trigger apoptosis on soft ECM vs. EMT on stiff matrices. The model offers several experimentally testable predictions related to the effect of neighbors on partial vs. full EMT, the tug of war between mitosis and the maintenance of migratory hybrid E/M states, as well as cell cycle defects in dynamic, heterogeneous populations of epithelial, hybrid E/M and mesenchymal cells.
Project description:Fibrotic interstitial lung disease (ILD) are lung disorders characterized by the accumulation of extracellular matrix, ultimately resulting in the destruction of the pulmonary scaffold. Continuous pro-fibrotic signaling perpetuates the remodeling process, specifically targeting the epithelial cell compartment, thereby destroying the gas exchange area. Studies that address this detrimental crosstalk between lung epithelial cells and fibroblasts are key to understanding ILD. With the aim of identifying functionally relevant targets that drive mesenchymal-epithelial crosstalk and their potential as new avenues to therapeutic strategies, we developed an organoid co-culture system based on human induced pluripotent stem cell-derived alveolar epithelial type 2 cells and lung fibroblasts from ILD patients as well as IMR-90 controls. While organoid formation capacity and organoid size was comparable in the presence of ILD or control lung fibroblasts, metabolic activity was significantly increased in ILD co-cultures. Alveolar organoids cultured with ILD fibroblasts further demonstrated reduced stem cell function supported by reduced Surfactant Protein C gene expression together with an aberrant basaloid-prone differentiation program indicated by elevated Cadherin 2, Bone Morphogenic Protein 4 and Vimentin transcription. In order to identify key mediators of the misguided mesenchymal-to-epithelial crosstalk with a focus on disease-relevant inflammatory processes, we used secretome mass spectrometry to identify key signals secreted by end stage ILD lung fibroblasts. Over 2000 proteins were detected in a single-shot experiment with 47 differentially upregulated proteins when comparing ILD and non-chronic lung disease control fibroblasts. The secretome profile was dominated by chemokines of the C-X-C motif family, including CXCL1, -3, and -8, all interfering with (epithelial) growth factor signaling orchestrated by Interleukin 11 (IL11), steering fibrogenic cell-cell communication, and proteins regulating extracellular matrix remodeling including epithelial-to-mesenchymal transition. When in turn treating 3D monocultures of iAT2s with IL11 we recapitulated the co-culture results obtained with primary ILD fibroblasts including changes in metabolic activity as well as organoid formation capacity and size. In summary, our analysis identified mesenchyme-derived mediators likely contributing to the disease-perpetuating mesenchymal-to-epithelial crosstalk in ILD by using sophisticated alveolar organoid co-cultures indicating the importance of cytokine-driven aberrant epithelial differentiation and confirmed IL11 as a key player in ILD using an unbiased approach.
Project description:Thymic epithelium is critical for the structural integrity of the thymus and for T cell development. Within the fully formed thymus, large numbers of hematopoietic cells shape the thymic epithelium into a scaffold-like structure which bears little similarity to classical epithelial layers, such as those observed in the skin, intestine or pancreas. Here, we show that human thymic epithelial cells (TECs) possess an epithelial identity that also incorporates the expression of mesenchymal cell associated genes, whose expression levels vary between medullary and cortical TECs (m/cTECs). Using pluripotent stem cell (PSC) differentiation systems, we identified a unique population of cells that co-expressed the master TEC transcription factor FOXN1, as well as the epithelial associated marker EPCAM and the mesenchymal associated gene CD90. Using the same serum free culture conditions, we also observed co-expression of EPCAM and CD90 on cultured TECs derived from neonatal human thymus in vitro. Single cell RNA-sequencing revealed these cultured TECs possessed an immature mTEC phenotype and expressed epithelial and mesenchymal associated genes, such as EPCAM, CLDN4, CD90 and COL1A1. Importantly, flow cytometry and single cell RNA-sequencing analysis further confirmed the presence of an EPCAM+CD90+ population in the CD45- fraction of neonatal human thymic stromal cells in vivo. Using the human thymus cell atlas, we found that cTECs displayed more pronounced mesenchymal characteristics than mTECs during embryonic development. Collectively, these results suggest human TECs possess a hybrid gene expression program comprising both epithelial and mesenchymal elements, and provide a basis for the further exploration of thymus development from primary tissues and from the in vitro differentiation of PSCs.
Project description:Conventional 2-D differentiation from pluripotency fails to recapitulate cell interactions occurring during organogenesis. 3-D organoids generate complex organ-like tissues, however it is unclear how heterotypic interactions impact lineage identity. Here we use single-cell RNA-seq to reconstruct hepatocyte-like lineage progression from pluripotency in 2-D culture. We then derive 3-D liver bud (LB) organoids by reconstituting hepatic, stromal, and endothelial interactions, and deconstruct heterogeneity during LB self-organization. We find that LB hepatoblasts differentiate towards hepatocyte fate, and in addition express epithelial migration signatures characteristic of organ budding. We identify hypoxia and inflammation signatures in endothelial and mesenchymal cells, which we suggest induce LB vasculogenesis. We use network analysis to predict autocrine and paracrine signaling in LBs, and show that VEGF crosstalk potentiates endothelial network formation and hepatoblast differentiation. Our molecular dissection reveals inter-lineage communication that is required for self-organization, and illuminates previously inaccessible aspects of human organ development and regeneration.