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An iPSC model recapitulates key features of LCH and identifies cell type-specific BRAFV600E effects and drug responses

ABSTRACT: Langerhans cell histiocytosis (LCH) is a clonal hematopoietic disorder defined by tumorous lesions containing CD1a+/CD207+ cells. Two severe complications of LCH are systemic hyperinflammation and progressive neurodegeneration. The scarcity of primary samples and lack of appropriate models limit our mechanistic understanding of LCH pathogenesis and affect patient care. We generated a human in vitro model for LCH using induced pluripotent stem cells (iPSCs) harboring the BRAFV600E mutation, the most common genetic driver of LCH. We show that BRAFV600E/WT iPSCs display myelo-monocytic skewing during hematopoiesis and spontaneously differentiate into CD1a+/CD207+ cells that are similar to lesional LCH cells and are derived from a CD14+ progenitor. BRAFV600E modulates the expression of key transcription factors regulating monocytic differentiation and leads to an upregulation of pro-inflammatory molecules and LCH marker genes early during myeloid differentiation. BRAFV600E-induced transcriptomic changes are reverted upon treatment with MAPK-pathway inhibitors (MAPKi). Importantly, MAPKi does not affect myeloid progenitors but reduces only the mature CD14+ cell population. Furthermore, iPSC-derived neurons (iNeurons) cocultured with BRAFV600E/WT microglia-like cells (iMGL), differentiated from iPSC-derived CD34+ progenitors, exhibit signs of neurodegeneration with neuronal damage and release of neurofilament light chain. In summary, our model provides a platform to study the effect of BRAFV600E in different hematopoietic cell types and provides a tool to compare and identify novel approaches for the treatment of BRAFV600E-driven diseases.

ORGANISM(S): Homo sapiens

PROVIDER: GSE270891 | GEO | 2024/12/05

REPOSITORIES: GEO

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Project description:Langerhans-cell histiocytosis (LCH) is characterized by heterogeneous lesions containing CD207+ Langerhans cells (LCs) and lymphocytes. In this study, we isolated CD207+ cells and CD3+ T cells from LCH lesions to determine cell-specific gene expression. Compared to control epidermal CD207+ cells, the LCH CD207+ cells yielded 2113 differentially-expressed genes (FDR<0.01). Surprisingly, expression of many genes previously associated with LCH, including cell-cycle regulators, pro-inflammatory cytokines and chemokines were not significantly different from control LCs in our study. However, several novel genes whose products activate and recruit T cells to sites of inflammation, including SPP1 (osteopontin), were highly over-expressed in LCH CD207+ cells. Furthermore, several genes associated with immature myeloid dendritic cells were over-expressed in LCH CD207+ cells. Compared to the peripheral CD3+ cells from LCH patients, the LCH lesion CD3+ cells yielded only 162 differentially-regulated genes (FDR<0.01), and the expression profile of the LCH lesion CD3+ cells was consistent with an activated regulatory T cell phenotype with increased expression of FOXP3, CTLA4 as well as SPP1. Based on these results, we propose a new model of LCH pathogenesis in which lesions do not arise from epidermal Langerhans cells, but from accumulation of bone-marrow derived immature myeloid dendritic cells that recruit activated lymphocytes. Cell-specific gene expression from LCH biopsy specimens was evaluated by comparing hybridization signal from amplified cDNA on Affymetrix gene chips (U133A Plus 2.0) (Table1). Three sets of comparisons were performed: 1) Thirteen LCH CD207+ samples were compared to 12 control skin LCH CD207+ samples. 2) Seven LCH lesion CD3+ samples were compared to 7 peripheral blood CD3+ samples from the same patients. 3) Twelve LCH lesion CD3+ samples were compared to 4 pooled control tonsil CD3+ samples (5 individual tonsil CD3+ samples/pool).

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An iPSC model recapitulates key features of LCH and identifies cell type-specific BRAFV600E effects and drug responses

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