Publications by authors named "Susan H Guttentag"

During alveolar repair, alveolar type 2 (AT2) epithelial cell progenitors rapidly proliferate and differentiate into flat AT1 epithelial cells. Failure of normal alveolar repair mechanisms can lead to loss of alveolar structure (emphysema) or development of fibrosis, depending on the type and severity of injury. To test if β1-containing integrins are required during repair following acute injury, we administered E.

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Lung organogenesis requires precise timing and coordination to effect spatial organization and function of the parenchymal cells. To provide a systematic broad-based view of the mechanisms governing the dynamic alterations in parenchymal cells over crucial periods of development, we performed a single-cell RNA-sequencing time-series yielding 102,571 epithelial, endothelial and mesenchymal cells across nine time points from embryonic day 12 to postnatal day 14 in mice. Combining computational fate-likelihood prediction with RNA in situ hybridization and immunofluorescence, we explore lineage relationships during the saccular to alveolar stage transition.

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Article Synopsis
  • AEC2 dysfunction plays a crucial role in both adult and pediatric interstitial lung diseases, including idiopathic pulmonary fibrosis (IPF), but studying early disease mechanisms has been challenging due to limited access to primary AEC2s.
  • Researchers developed an in vitro model using patient-specific induced pluripotent stem cells (iPSCs) with a disease-associated variant to explore AEC2 dysfunction.
  • Findings show that mutant AEC2s accumulate improperly processed proteins, leading to reduced progenitor capacity and metabolic issues, and treatment with hydroxychloroquine worsens these dysfunctions, demonstrating the model's potential for studying disease mechanisms in ILD.
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Lamellar bodies (LBs) are lysosome-related organelles (LROs) of surfactant-producing alveolar type 2 (AT2) cells of the distal lung epithelium. Trafficking pathways to LBs have been understudied but are likely critical to AT2 cell homeostasis given associations between genetic defects of endosome to LRO trafficking and pulmonary fibrosis in Hermansky Pudlak syndrome (HPS). Our prior studies uncovered a role for AP-3, defective in HPS type 2, in trafficking Peroxiredoxin-6 to LBs.

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Background: In preterm infants who require mechanical ventilation (MV), volume-targeted ventilation (VTV) modes are associated with lower rates of bronchopulmonary dysplasia compared with pressure-limited ventilation. Bronchopulmonary dysplasia rates in our NICU were higher than desired, prompting quality improvement initiatives to improve MV by increasing the use of VTV.

Methods: We implemented and tested interventions over a 3-year period.

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The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) novel coronavirus 2019 (COVID-19) global pandemic has led to millions of cases and hundreds of thousands of deaths. While older adults appear at high risk for severe disease, hospitalizations and deaths due to SARS-CoV-2 among children have been relatively rare. Integrating single-cell RNA sequencing (scRNA-seq) of developing mouse lung with temporally resolved immunofluorescence in mouse and human lung tissue, we found that expression of SARS-CoV-2 Spike protein primer TMPRSS2 was highest in ciliated cells and type I alveolar epithelial cells (AT1), and TMPRSS2 expression increased with aging in mice and humans.

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Emerging evidence indicates that early life events can increase the risk for developing chronic obstructive pulmonary disease (COPD). Using an inducible transgenic mouse model for NF-κB activation in the airway epithelium, we found that a brief period of inflammation during the saccular stage (P3-P5) but not alveolar stage (P10-P12) of lung development disrupted elastic fiber assembly, resulting in permanent reduction in lung function and development of a COPD-like lung phenotype that progressed through 24 months of age. Neutrophil depletion prevented disruption of elastic fiber assembly and restored normal lung development.

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The SARS-CoV-2 novel coronavirus global pandemic (COVID-19) has led to millions of cases and hundreds of thousands of deaths around the globe. While the elderly appear at high risk for severe disease, hospitalizations and deaths due to SARS-CoV-2 among children have been relatively rare. Integrating single-cell RNA sequencing (scRNA-seq) of the developing mouse lung with temporally-resolved RNA-in-situ hybridization (ISH) in mouse and human lung tissue, we found that expression of SARS-CoV-2 Spike protein primer was highest in ciliated cells and type I alveolar epithelial cells (AT1), and expression was increased with aging in mice and humans.

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Bronchopulmonary dysplasia (BPD) is a leading complication of preterm birth that affects infants born in the saccular stage of lung development at <32 weeks of gestation. Although the mechanisms driving BPD remain uncertain, exposure to hyperoxia is thought to contribute to disease pathogenesis. To determine the effects of hyperoxia on epithelial-mesenchymal interactions and to define the mediators of activated Wnt/β-catenin signaling after hyperoxia injury.

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Article Synopsis
  • Alveolar epithelial type 2 cells (AEC2s) are essential for lung health, but isolating them from patients is challenging; researchers are engineering these cells from human pluripotent stem cells (PSCs) for better study and utilization.* -
  • Using advanced techniques like single-cell RNA sequencing, the study traces how AEC2s differentiate in the lab, revealing divergent pathways where some cells successfully become AEC2s while others take on different identities.* -
  • The research develops a model to understand how certain signals affect this differentiation, finding that while early developmental flexibility allows for varied fates, this plasticity decreases over time, ultimately leading to stable, self-renewing AEC2s.*
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Integrins, the extracellular matrix receptors that facilitate cell adhesion and migration, are necessary for organ morphogenesis; however, their role in maintaining adult tissue homeostasis is poorly understood. To define the functional importance of β1 integrin in adult mouse lung, we deleted it after completion of development in type 2 alveolar epithelial cells (AECs). Aged β1 integrin-deficient mice exhibited chronic obstructive pulmonary disease-like (COPD-like) pathology characterized by emphysema, lymphoid aggregates, and increased macrophage infiltration.

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Article Synopsis
  • Scientists have created new mouse and human stem cell lines with special reporters that help track and study airway secretory cells generated from pluripotent stem cells (PSCs).
  • These engineered cells show a tendency to adopt characteristics of both airway and alveolar cell types, indicating a level of flexibility in their development.
  • By inhibiting Wnt signaling, researchers can reduce this plasticity, providing valuable insights for better directing the differentiation of lung cells and creating a model for human airway development.
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Alveolar type II (AT2) epithelial cells are uniquely specialized to produce surfactant in the lung and act as progenitor cells in the process of repair after lung injury. AT2 cell injury has been implicated in several lung diseases, including idiopathic pulmonary fibrosis and bronchopulmonary dysplasia. The inability to maintain primary AT2 cells in culture has been a significant barrier in the investigation of pulmonary biology.

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Wnt/β-catenin signaling is necessary for normal lung development, and abnormal Wnt signaling contributes to the pathogenesis of both bronchopulmonary dysplasia (BPD) and idiopathic pulmonary fibrosis (IPF), fibrotic lung diseases that occur during infancy and aging, respectively. Using a library of human normal and diseased human lung samples, we identified a distinct signature of nuclear accumulation of β-catenin phosphorylated at tyrosine 489 and epithelial cell cytosolic localization of β-catenin phosphorylated at tyrosine 654 in early normal lung development and fibrotic lung diseases BPD and IPF. Furthermore, this signature was recapitulated in murine models of BPD and IPF.

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Defining the mechanisms of cellular pathogenesis in rare lung diseases such as Hermansky-Pudlak syndrome (HPS) is often complicated by loss of the differentiated phenotype of cultured primary alveolar type 2 (AT2) cells, as well as by a lack of durable cell lines that are faithful to both AT2-cell and rare disease phenotypes. We used CRISPR/Cas9 gene editing to generate a series of HPS-specific mutations in the MLE-15 cell line. The resulting MLE-15/HPS cell lines exhibit preservation of AT2 cellular functions, including formation of lamellar body-like organelles, complete processing of surfactant protein B, and known features of HPS specific to each trafficking complex, including loss of protein targeting to lamellar bodies.

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Article Synopsis
  • Researchers successfully created alveolar epithelial type 2 cells (AEC2s) from human pluripotent stem cells (PSCs), a crucial step for studying lung development and diseases.* -
  • They tracked the development of these cells using fluorescent markers and found that the cells could form structures called "alveolospheres" independently in 3D cultures.* -
  • The study also demonstrated gene correction in PSCs from patients with a surfactant mutation, showing potential for modeling diseases and regenerating lung tissue in the future.*
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Bronchopulmonary dysplasia (BPD) is a common complication of premature birth. The histopathology of BPD is characterized by an arrest of alveolarization with fibroblast activation. The Wnt/β-catenin signaling pathway is important in early lung development.

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Mutation of threonine for isoleucine at codon 73 (I73T) in the human surfactant protein C (hSP-C) gene (SFTPC) accounts for a significant portion of SFTPC mutations associated with interstitial lung disease (ILD). Cell lines stably expressing tagged primary translation product of SP-C isoforms were generated to test the hypothesis that deposition of hSP-C(I73T) within the endosomal system promotes disruption of a key cellular quality control pathway, macroautophagy. By fluorescence microscopy, wild-type hSP-C (hSP-C(WT)) colocalized with exogenously expressed human ATP binding cassette class A3 (hABCA3), an indicator of normal trafficking to lysosomal-related organelles.

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Mammals must inflate their lungs and breathe within minutes of birth to survive. A key regulator of neonatal lung inflation is pulmonary surfactant, a lipoprotein complex which increases lung compliance by reducing alveolar surface tension (Morgan, 1971). Whether other developmental processes also alter lung mechanics in preparation for birth is unknown.

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Yeast Atg1 initiates autophagy in response to nutrient limitation. The Ulk gene family encompasses the mammalian orthologs of yeast ATG1. We created mice deficient for both Ulk1 and Ulk2 and found that the mice die within 24 h of birth.

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The lipid transport protein, ABCA3, expressed in alveolar type 2 (AT2) cells, is critical for surfactant homeostasis. The first luminal loop of ABCA3 contains three putative N-linked glycosylation sites at residues 53, 124, and 140. A common cotranslational modification, N-linked glycosylation, is critical for the proper expression of glycoproteins by enhancing folding, trafficking, and stability through augmentation of the endoplasmic reticulum (ER) folding cycle.

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Background: Surfactant protein B (SP-B) is essential for normal lung function, and decreased concentrations of SP-B have a deleterious effect on pulmonary outcome. SP-B levels may correlate with variations in the encoding gene (SFTPB). SFTPB single-nucleotide polymorphism Ile131Thr affects proSP-B N-glycosylation in humans and the glycosylated Thr variant associates with pulmonary diseases.

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Effective major histocompatibility complex-II (MHC-II) antigen presentation from phagocytosed particles requires phagosome-intrinsic Toll-like receptor (TLR) signaling, but the molecular mechanisms underlying TLR delivery to phagosomes and how signaling regulates antigen presentation are incompletely understood. We show a requirement in dendritic cells (DCs) for adaptor protein-3 (AP-3) in efficient TLR recruitment to phagosomes and MHC-II presentation of antigens internalized by phagocytosis but not receptor-mediated endocytosis. DCs from AP-3-deficient pearl mice elicited impaired CD4(+) T cell activation and Th1 effector cell function to particulate antigen in vitro and to recombinant Listeria monocytogenes infection in vivo.

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Neutrophils are essential for maintaining innate immune surveillance under normal conditions, but also represent a major contributor to tissue damage during inflammation. Neutrophil homeostasis is therefore tightly regulated. Cxcr2 plays a critical role in neutrophil homeostasis, as Cxcr2(-/-) mice demonstrate mild neutrophilia and severe neutrophil hyperplasia in the bone marrow.

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Stretch is an essential mechanism for lung growth and development. Animal models in which fetal lungs have been chronically over or underdistended demonstrate a disrupted mix of type II and type I cells, with static overdistention typically promoting a type I cell phenotype. The Rho GTPase family, key regulators of cytoskeletal signaling, are known to mediate cellular differentiation in response to stretch in other organs.

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