Endothelial and skeletal muscle lineages arise from common embryonic progenitors. Despite their shared developmental origin, adult endothelial cells (ECs) and muscle stem cells (MuSCs; satellite cells) have been thought to possess distinct gene signatures and signaling pathways. Here, we shift this paradigm by uncovering how adult MuSC behavior is affected by the expression of a subset of EC transcripts. We used several computational analyses including single-cell RNA-seq (scRNA-seq) to show that MuSCs express low levels of canonical EC markers in mice. We demonstrate that MuSC survival is regulated by one such prototypic endothelial signaling pathway (VEGFA-FLT1). Using pharmacological and genetic gain- and loss-of-function studies, we identify the FLT1-AKT1 axis as the key effector underlying VEGFA-mediated regulation of MuSC survival. All together, our data support that the VEGFA-FLT1-AKT1 pathway promotes MuSC survival during muscle regeneration, and highlights how the minor expression of select transcripts is sufficient for affecting cell behavior.
© 2024, Verma et al.

Endothelial progenitor cells (EPCs) dysfunction is involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). The transcription factor PU.1 is essential for the maintenance of stem/progenitor cell homeostasis. However, the role of PU.1 in COPD and its effects on EPC function and lung-homing, remain unclear. This study aimed to explore the protective activity of PU.1 and the underlying mechanisms in a cigarette smoke extract (CSE)-induced emphysema mouse model.
C57BL/6 mice were treated with CSE to establish a murine emphysema model and injected with overexpressed PU.1 or negative control adeno-associated virus. Morphometry of lung slides, lung function, and apoptosis of lung tissues were evaluated. Immunofluorescence co-localization was used to analyze EPCs homing into the lung. Flow cytometry was performed to detect EPC count in lung tissues and bone marrow (BM). The angiogenic ability of BM-derived EPCs cultured in vitro was examined by tube formation assay. We determined the expression levels of PU.1, β-catenin, C-X-C motif ligand 12 (CXCL12), C-X-C motif receptor 4 (CXCR4), stem cell antigen-1 (Sca-1), and stemness genes.
CSE exposure significantly reduced the expression of PU.1 in mouse lung tissues, BM, and BM-derived EPCs. PU.1 overexpression attenuated CSE-induced emphysematous changes, lung function decline, and apoptosis. In emphysematous mice, PU.1 overexpression markedly reversed the decreased proportion of EPCs in BM and promoted the lung-homing of EPCs. The impaired angiogenic ability of BM-derived EPCs induced by CSE could be restored by the overexpression of PU.1. In addition, PU.1 upregulation evidently reversed the decreased expression of β-catenin, CXCL12, CXCR4, Scal-1, and stemness genes in mouse lung tissues, BM, and BM-derived EPCs after CSE exposure.
PU.1 alleviates the inhibitory effects of CSE on EPC function and lung-homing via activating the canonical Wnt/β-catenin pathway and CXCL12/CXCR4 axis. While further research is needed, our research may indicate a potential therapeutic target for COPD patients.
© 2024 He X. et al.

While the generation of many lineages from pluripotent stem cells has resulted in basic discoveries and clinical trials, the derivation of tissue-specific mesenchyme via directed differentiation has markedly lagged. The derivation of lung-specific mesenchyme is particularly important since this tissue plays crucial roles in lung development and disease. Here we generate a mouse induced pluripotent stem cell (iPSC) line carrying a lung-specific mesenchymal reporter/lineage tracer. We identify the pathways (RA and Shh) necessary to specify lung mesenchyme and find that mouse iPSC-derived lung mesenchyme (iLM) expresses key molecular and functional features of primary developing lung mesenchyme. iLM recombined with engineered lung epithelial progenitors self-organizes into 3D organoids with juxtaposed layers of epithelium and mesenchyme. Co-culture increases yield of lung epithelial progenitors and impacts epithelial and mesenchymal differentiation programs, suggesting functional crosstalk. Our iPSC-derived population thus provides an inexhaustible source of cells for studying lung development, modeling diseases, and developing therapeutics.
© 2023. The Author(s).

The successful generation of endodermal, ectodermal, and most mesodermal lineages from pluripotent stem cells has resulted in basic discoveries and regenerative medicine clinical trials of cell-based therapies. In contrast, the derivation of tissue-specific mesenchyme via directed differentiation in vitro has markedly lagged, due in part to a limited understanding of the signaling pathways regulating in vivo mesenchymal development and a lack of specific markers or reporters able to purify such lineages. The derivation of lung-specific mesenchyme is a particularly important goal since this tissue plays important roles in lung development and respiratory disease pathogenesis. Here we generate a mouse induced pluripotent stem cell (iPSC) line carrying a lung-specific mesenchymal reporter/lineage tracer facilitating the tracking and purification of engineered lung-specific mesenchyme. We identify the key signaling pathways (RA and Shh) necessary to specify lung mesenchyme from lateral plate mesodermal precursors and find that mouse iPSC-derived lung mesenchyme (iLM) expresses the molecular and functional phenotypes of primary developing lung mesenchyme. Purified iLM can be recombined with separately engineered lung epithelial progenitors, self-organizing into 3-dimensional organoids featuring significantly augmented structural complexity and lineage purity, including interacting juxtaposed layers of epithelium and mesenchyme. Co-culture with iLM increases the yield of lung epithelial progenitors and impacts epithelial and mesenchymal differentiation programs, suggesting functional epithelial-mesenchymal crosstalk. Our iPSC-derived population thus expresses key features of developing lung mesenchyme, providing an inexhaustible source of cells for studying lung development, modeling diseases, and developing therapeutics.

h4>Background: /h4> Chemotherapy remains the mainstay of treatment for various cancers. However recent studies suggested that it may also induce local or systemic changes that promote the dissemination and proliferation of cancer cells leading to successful metastasis. Understanding this process is therefore instrumental to help us identify patient population that may or may not be benefit from chemotherapy, and develop innovative approaches to prevent metastasis. Methods In this study, we investigated the mechanism of chemotherapy causing the metastasis of colorectal cancer, and the roles of G-CSF induced by chemotherapy in the vessel formation. Eight-week-old C57/BL6 mice were used as animal models in this study to investigate the lung metastasis by the chemotherapy. Conditional endothelial cell STAT3 −/− (Signal Transducer and Activator of Transcription, STAT) knockout mice (STAT3 flox/flox ; Tek-Cre mice), were used to investigate the function of STAT3 on lung metastasis under the chemotherapy. Bone marrow and plasma was selected to detect the mobilization of endothelial progenitor cells (EPCs) and MDSCs. To trace BM-derived cells, we prepared chimeric mouse transplanted with BM cells from green fluorescent protein (GFP) transgenic mouse. In vitro, experiments were performed in human umbilical vein endothelial cells (HUVEC) to analyse the function of G-CSF on angiogenesis. Detected the G-CSF content in the plasma of the patients who received an adjuvant chemotherapy with the XELOX (oxaliplatin plus capecitabine) regimen. Results Our study showed that oxaliplatin chemotherapy could increase the expression of G-CSF to promote lung metastasis. First, G-CSF/STAT3 signaling facilitated lung metastasis by enhancing vascular adhesion rather than diminishing the blood vessel density. G-CSF also promoted Endothelial Progenitor Cells (EPCs) mobilization that devoted to vasculogenesis, a critical step for vessel density in metastatic sites; moreover, chemotherapy augmented the mobilization of MDSCs from the bone marrow by G-CSF. In consistent with these, anti-G-CSF suppressed the formation of a functional vasculature and induced tumoral immunosuppression, resulting in an anti-metastasis effect during chemotherapy. Furthermore, at human level, we observed high level of G-CSF, either at baseline or after receiving adjuvant XELOX chemotherapy, correlated with poor overall and recurrence-free survival. Conclusions These results demonstrate that certain chemotherapy could paradoxically result in worse outcome due to increased expression of G-CSF. Our findings provide mechanistic insight into cautious use of G-CSF and potential utility of anti-G-CSF in personalized cancer therapy.