Biology subjects

Flodby, P.

Publications and source records attributed to Flodby, P..

4 recordsLinked to original sources

bioRxiv2025

Loss of tight junction protein claudin 18 uncovers alveolar epithelial stem cell plasticity and emergence of non-fibrogenic transitional progenitors

Persistence of senescent alveolar transitional progenitors following lung injury is implicated in the pathogenesis of fibrosis. We identified transitional cells in uninjured Cldn18 knockout (KO) mouse lungs distinct from previously reported damage-associated transitional progenitors (DATPs) with a less fibrogenic transcriptomic profile. Cldn18 KO mice are protected from bleomycin-induced fibrosis, with early restoration of cellular homeostasis. Lineage tracing implicates accelerated differentiation as a mechanism for protection from fibrosis, leading us to name these cells regeneration-associated transitional progenitors (RATPs). Multiome confirms that RATPs and DATPs are epigenetically distinct, with RATPs comprised of RATP2s and RATP1s based on epigenomic proximity to AT2s and AT1s, respectively, and suggests dynamic regulatory remodeling during AT2-to-AT1 differentiation, with NKX2.1 and AP-1 active in early transitions and TEAD factors in later stages. These results reveal an unexpected role for Cldn18 in regulation of AEC plasticity, while identification of RATPs challenges the notion that persistence of transitional alveolar cells is invariably pathologic.

cell biology↗

bioRxiv2023

GRAMD2+ alveolar type I cell plasticity facilitates cell state transitions in organoid culture

Alveolar epithelial regeneration is critical for normal lung function and becomes dysregulated in disease. While alveolar type 2 (AT2) and club cells are known distal lung epithelial progenitors, determining if alveolar epithelial type 1 (AT1) cells also contribute to alveolar regeneration has been hampered by lack of highly specific mouse models labeling AT1 cells. To address this, the Gramd2CreERT2 transgenic strain was generated and crossed to RosamTmG mice. Extensive cellular characterization, including distal lung immunofluorescence and cytospin staining, confirmed that GRAMD2+ AT1 cells are highly enriched for green fluorescent protein (GFP). Interestingly, Gramd2CreERT2 GFP+ cells were able to form organoids in organoid co-culture with Mlg fibroblasts. Temporal scRNAseq revealed that Gramd2+ AT1 cells transition through numerous intermediate lung epithelial cell states including basal, secretory and AT2 cell in organoids while acquiring proliferative capacity. Our results indicate that Gramd2+ AT1 cells are highly plastic suggesting they may contribute to alveolar regeneration.

cell biology↗

bioRxiv2022

Alveolar epithelial type 1 cells serve as a cell of origin for lung adenocarcinoma with distinct molecular and phenotypic presentation

Lung adenocarcinoma (LUAD) is the most common subtype of cancer arising in the distal lung. LUAD encompasses several pathologic subtypes, each with differing clinical outcomes and biological behaviors. However, the molecular and cellular underpinnings of the different subtypes are largely unknown. Understanding which cell populations in the distal lung contribute to LUAD could provide insights into the marked heterogeneity in pathologic features, clinical presentation and responses to therapy of LUAD. Differential expression analysis of lung adenocarcinoma transcriptomes from The Cancer Genome Atlas revealed distinct alveolar epithelial type 1 (AT1) and alveolar epithelial type 2 (AT2) cell signatures within human LUAD with significantly different survival outcomes between tumors expressing AT2 and AT1 gene signatures, suggesting AT1 cells might contribute to a subset of LUAD cases. To address this, we tested the ability of AT1 cells to give rise to LUAD following induction of KrasG12D, a known oncogenic driver of human LUAD. Activation of KrasG12D in Gram-domain containing 2 (Gramd2)+ AT1 cells gave rise to multiple LUAD lesions, primarily of papillary histology. In contrast, activation of KrasG12D in surfactant protein C (Sftpc+) AT2 cells resulted in LUAD lesions of lepidic histology. Immunohistochemistry established that Gramd2:KrasG12D lesions were of primary lung origin and not metastatic events. Spatial transcriptomic profiling revealed distinct pathway alterations within Gramd2- and Sftpc-derived LUAD. Immunofluorescence confirmed differences observed in the spatial transcriptomic analysis in expression patterns and distribution of cell-specific markers depending on cell of origin, while universal upregulation of the Krt8 intermediate cell state marker was observed. Our results are consistent with Gramd2+ AT1 cells serving as a putative cell of origin for LUAD and suggest that LUAD may be a collection of adenocarcinomas that share a common location within the distal lung but arise from different cells of origin.

cancer biology↗

bioRxiv2019

Epithelial Vegfa specifies a distinct endothelial population in the mouse lung

The lung microvasculature is essential for gas exchange and commonly considered homogeneous. We show that Vascular endothelial growth factor A (Vegfa) from the epithelium specifies a distinct endothelial cell (EC) population in the postnatal mouse lung. Vegfa is predominantly expressed by alveolar type 1 (AT1) cells and locally required to specify a subset of ECs. Single cell RNA-seq identified 15-20% lung ECs as transcriptionally distinct and marked by Carbonic anhydrase 4 (Car4), which are specifically lost upon epithelial Vegfa deletion. Car4 ECs, unlike bulk ECs, have extensive cellular projections and are separated from AT1 cells by a limited basement membrane without intervening pericytes. Without Car4 ECs, the alveolar space is aberrantly enlarged despite the normal appearance of myofibroblasts. Lung Car4 ECs and retina tip ECs have common and distinct transcriptional profiles. These findings support a signaling role of AT1 cells and shed light on alveologenesis.

developmental biology↗