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1.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-329632

ABSTRACT

Unlike many mammalian vital organs, the lung exhibits a robust, multifaceted regenerative response to severe injuries such as influenza infection, which primarily targets epithelial cells in the airways and alveoli. Quiescent lung-resident epithelial progenitors proliferate, migrate, and differentiate following lung injury, participating in two distinct reparative pathways: functionally beneficial regeneration and dysplastic tissue remodeling. Intrapulmonary airway-resident basal-like p63 + progenitors are one such progenitor cell type that migrates from the airways to form ectopic bronchiolar tissue in the alveoli, generating honeycomb-like cysts that fail to resolve after injury. Though this phenomenon is now well described, the cell-autonomous signals that drive dysplastic alveolar remodeling remain uncertain, a question made especially salient by observations that p63 + progenitors also expand dramatically upon diffuse alveolar damage in humans resulting from a variety of insults including SARS-CoV-2-induced ARDS. Here we show that the master basal cell transcription factor ΔNp63 is required for the immense migratory capacity of intrapulmonary p63 + progenitors and consequently for the dysplastic repair pathway manifest by these cells. We further demonstrate that ΔNp63 restricts the fate plasticity of intrapulmonary p63 + progenitors by regulating their epigenetic landscape, and that loss of ΔNp63 alters the deposition of active and repressive histone modifications at key differentiation gene loci, allowing ΔNp63 KO progenitors to proceed towards airway or alveolar differentiation depending on their surrounding environment. These insights into the regulatory mechanisms of dysplastic repair and intrapulmonary p63 + progenitor fate choice highlight potential therapeutic targets to promote more effective alveolar regeneration following severe lung injuries.

2.
Sci Transl Med ; 13(616): eabj1008, 2021 Oct 20.
Article in English | MEDLINE | ID: covidwho-1518118

ABSTRACT

Red blood cells (RBCs) are essential for aerobic respiration through delivery of oxygen to distant tissues. However, RBCs are currently considered immunologically inert, and few, if any, secondary functions of RBCs have been identified. Here, we showed that RBCs serve as critical immune sensors through surface expression of the nucleic acid­sensing Toll-like receptor 9 (TLR9). Mammalian RBCs expressed TLR9 on their surface and bound CpG-containing DNA derived from bacteria, plasmodia, and mitochondria. RBC-bound mitochondrial DNA was increased during human and murine sepsis and pneumonia. In vivo, CpG-carrying RBCs drove accelerated erythrophagocytosis and innate immune activation characterized by increased interferon signaling. Erythroid-specific deletion of TLR9 abrogated erythrophagocytosis and decreased local and systemic cytokine production during CpG-induced inflammation and polymicrobial sepsis. Thus, detection and capture of nucleic acid by TLR9-expressing RBCs regulated red cell clearance and inflammatory cytokine production, demonstrating that RBCs function as immune sentinels during pathologic states. Consistent with these findings, RBC-bound mitochondrial DNA was elevated in individuals with viral pneumonia and sepsis secondary to coronavirus disease 2019 (COVID-19) and associated with anemia and severity of disease. These findings uncover a previously unappreciated role of RBCs as critical players in inflammation distinct from their function in gas transport.


Subject(s)
Anemia , Immunity, Innate , Toll-Like Receptor 9 , Animals , DNA , Erythrocytes , Humans , Mice
3.
Sci Adv ; 6(48)2020 11.
Article in English | MEDLINE | ID: covidwho-1388431

ABSTRACT

Acute respiratory distress syndrome is associated with a robust inflammatory response that damages the vascular endothelium, impairing gas exchange. While restoration of microcapillaries is critical to avoid mortality, therapeutic targeting of this process requires a greater understanding of endothelial repair mechanisms. Here, we demonstrate that lung endothelium possesses substantial regenerative capacity and lineage tracing reveals that native endothelium is the source of vascular repair after influenza injury. Ablation of chicken ovalbumin upstream promoter-transcription factor 2 (COUP-TF2) (Nr2f2), a transcription factor implicated in developmental angiogenesis, reduced endothelial proliferation, exacerbating viral lung injury in vivo. In vitro, COUP-TF2 regulates proliferation and migration through activation of cyclin D1 and neuropilin 1. Upon influenza injury, nuclear factor κB suppresses COUP-TF2, but surviving endothelial cells ultimately reestablish vascular homeostasis dependent on restoration of COUP-TF2. Therefore, stabilization of COUP-TF2 may represent a therapeutic strategy to enhance recovery from pathogens, including H1N1 influenza and SARS-CoV-2.


Subject(s)
COUP Transcription Factor II/metabolism , Endothelial Cells/metabolism , Endothelium, Vascular/metabolism , Influenza A Virus, H1N1 Subtype , Lung/cytology , Lung/physiology , Orthomyxoviridae Infections/metabolism , Regeneration/genetics , Animals , COUP Transcription Factor II/genetics , Cell Movement/genetics , Cell Proliferation/genetics , Disease Models, Animal , Female , Gene Knockout Techniques , HEK293 Cells , Humans , Male , Mice , Mice, Transgenic , Orthomyxoviridae Infections/virology , Transfection
4.
Stem Cell Reports ; 15(5): 1015-1025, 2020 11 10.
Article in English | MEDLINE | ID: covidwho-864993

ABSTRACT

Despite the central importance of the respiratory system, the exact mechanisms governing lung repair after severe injury remain unclear. The notion that alveolar type 2 cells (AT2s) self-renew and differentiate into alveolar type 1 cells (AT1s) does not fully encompass scenarios where these progenitors are severely affected by disease, e.g., H1N1 influenza or SARS-CoV-2 (COVID-19). Intrapulmonary p63+ progenitor cells, a rare cell type in mice but potentially encompassing more numerous classic basal cells in humans, are activated in such severe injury settings, proliferating and migrating into the injured alveolar parenchyma, providing a short-term "emergency" benefit. While the fate of these cells is controversial, most studies indicate that they represent a maladaptive repair pathway with a fate restriction toward airway cell types, rarely differentiating into AT2 or AT1 cells. Here, we discuss the role of intrapulmonary basal-like p63+ cells in alveolar regeneration and suggest a unified model to guide future studies.


Subject(s)
Lung/physiology , Regeneration , Stem Cells/metabolism , Alveolar Epithelial Cells/cytology , Alveolar Epithelial Cells/metabolism , COVID-19/pathology , COVID-19/virology , Cell Differentiation , Humans , Lung/metabolism , Lung Diseases/pathology , Lung Diseases/therapy , Lung Diseases/virology , SARS-CoV-2/isolation & purification , Stem Cell Transplantation , Stem Cells/cytology
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