Human distal airways contain a multipotent secretory cell that can regenerate alveoli.

The human lung differs substantially from its mouse counterpart, resulting in a distinct distal airway architecture affected by disease pathology in chronic obstructive pulmonary disease. In humans, the distal branches of the airway interweave with the alveolar gas-exchange niche, forming an anatomical structure known as the respiratory bronchioles. Owing to the lack of a counterpart in mouse, the cellular and molecular mechanisms that govern respiratory bronchioles in the human lung remain uncharacterized. Here we show that human respiratory bronchioles contain a unique secretory cell population that is distinct from cells in larger proximal airways. Organoid modelling reveals that these respiratory airway secretory (RAS) cells act as unidirectional progenitors for alveolar type 2 cells, which are essential for maintaining and regenerating the alveolar niche. RAS cell lineage differentiation into alveolar type 2 cells is regulated by Notch and Wnt signalling. In chronic obstructive pulmonary disease, RAS cells are altered transcriptionally, corresponding to abnormal alveolar type 2 cell states, which are associated with smoking exposure in both humans and ferrets. These data identify a distinct progenitor in a region of the human lung that is not found in mouse that has a critical role in maintaining the gas-exchange compartment and is altered in chronic lung disease.

Activation of STING Signaling Pathway Effectively Blocks Human Coronavirus Infection.

The COVID-19 pandemic poses a serious global health threat. The rapid global spread of SARS-CoV-2 highlights an urgent need to develop effective therapeutics for blocking SARS-CoV-2 infection and spread. Stimulator of Interferon Genes (STING) is a chief element in host antiviral defense pathways. In this study, we examined the impact of the STING signaling pathway on coronavirus infection using the human coronavirus OC43 (HCoV-OC43) model. We found that HCoV-OC43 infection did not stimulate the STING signaling pathway, but the activation of STING signaling effectively inhibits HCoV-OC43 infection to a much greater extent than that of type I interferons (IFNs). We also discovered that IRF3, the key STING downstream innate immune effector, is essential for this anticoronavirus activity. In addition, we found that the amidobenzimidazole (ABZI)-based human STING agonist diABZI robustly blocks the infection of not only HCoV-OC43 but also SARS-CoV-2. Therefore, our study identifies the STING signaling pathway as a potential therapeutic target that could be exploited for developing broad-spectrum antiviral therapeutics against multiple coronavirus strains in order to face the challenge of future coronavirus outbreaks.IMPORTANCE The highly infectious and lethal SARS-CoV-2 is posing an unprecedented threat to public health. Other coronaviruses are likely to jump from a nonhuman animal to humans in the future. Novel broad-spectrum antiviral therapeutics are therefore needed to control known pathogenic coronaviruses such as SARS-CoV-2 and its newly mutated variants, as well as future coronavirus outbreaks. STING signaling is a well-established host defense pathway, but its role in coronavirus infection remains unclear. In the present study, we found that activation of the STING signaling pathway robustly inhibits infection of HCoV-OC43 and SARS-CoV-2. These results identified the STING pathway as a novel target for controlling the spread of known pathogenic coronaviruses, as well as emerging coronavirus outbreaks.

Long noncoding RNAs are spatially correlated with transcription factors and regulate lung development.

Long noncoding RNAs (lncRNAs) are thought to play important roles in regulating gene transcription, but few have well-defined expression patterns or known biological functions during mammalian development. Using a conservative pipeline to identify lncRNAs that have important biological functions, we identified 363 lncRNAs in the lung and foregut endoderm. Importantly, we show that these lncRNAs are spatially correlated with transcription factors across the genome. In-depth expression analyses of lncRNAs with genomic loci adjacent to the critical transcription factors Nkx2.1, Gata6, Foxa2 (forkhead box a2), and Foxf1 mimic the expression patterns of their protein-coding neighbor. Loss-of-function analysis demonstrates that two lncRNAs, LL18/NANCI (Nkx2.1-associated noncoding intergenic RNA) and LL34, play distinct roles in endoderm development by controlling expression of critical developmental transcription factors and pathways, including retinoic acid signaling. In particular, we show that LL18/NANCI acts upstream of Nkx2.1 and downstream from Wnt signaling to regulate lung endoderm gene expression. These studies reveal that lncRNAs play an important role in foregut and lung endoderm development by regulating multiple aspects of gene transcription, often through regulation of transcription factor expression.

Coordination of heart and lung co-development by a multipotent cardiopulmonary progenitor.

Co-development of the cardiovascular and pulmonary systems is a recent evolutionary adaption to terrestrial life that couples cardiac output with the gas exchange function of the lung. Here we show that the murine pulmonary vasculature develops even in the absence of lung development. We have identified a population of multipotent cardiopulmonary mesoderm progenitors (CPPs) within the posterior pole of the heart that are marked by the expression of Wnt2, Gli1 and Isl1. We show that CPPs arise from cardiac progenitors before lung development. Lineage tracing and clonal analysis demonstrates that CPPs generate the mesoderm lineages within the cardiac inflow tract and lung including cardiomyocytes, pulmonary vascular and airway smooth muscle, proximal vascular endothelium, and pericyte-like cells. CPPs are regulated by hedgehog expression from the foregut endoderm, which is required for connection of the pulmonary vasculature to the heart. Together, these studies identify a novel population of multipotent cardiopulmonary progenitors that coordinates heart and lung co-development that is required for adaptation to terrestrial existence.

Ezh2 represses the basal cell lineage during lung endoderm development.

The development of the lung epithelium is regulated in a stepwise fashion to generate numerous differentiated and stem cell lineages in the adult lung. How these different lineages are generated in a spatially and temporally restricted fashion remains poorly understood, although epigenetic regulation probably plays an important role. We show that the Polycomb repressive complex 2 component Ezh2 is highly expressed in early lung development but is gradually downregulated by late gestation. Deletion of Ezh2 in early lung endoderm progenitors leads to the ectopic and premature appearance of Trp63+ basal cells that extend the entire length of the airway. Loss of Ezh2 also leads to reduced secretory cell differentiation. In their place, morphologically similar cells develop that express a subset of basal cell genes, including keratin 5, but no longer express high levels of either Trp63 or of standard secretory cell markers. This suggests that Ezh2 regulates the phenotypic switch between basal cells and secretory cells. Together, these findings show that Ezh2 restricts the basal cell lineage during normal lung endoderm development to allow the proper patterning of epithelial lineages during lung formation.

Expression of histone deacetylase 3 instructs alveolar type I cell differentiation by regulating a Wnt signaling niche in the lung.

The commitment and differentiation of the alveolar type I (AT1) cell lineage is a critical step for the formation of distal lung saccules, which are the primitive alveolar units required for postnatal respiration. How AT1 cells arise from the distal lung epithelial progenitor cells prior to birth and whether this process depends on a developmental niche instructed by mesenchymal cells is poorly understood. We show that mice lacking histone deacetylase 3 specifically in the developing lung mesenchyme display lung hypoplasia including decreased mesenchymal proliferation and a severe impairment of AT1 cell differentiation. This is correlated with a decrease in Wnt/ß-catenin signaling in the lung epithelium. We demonstrate that inhibition of Wnt signaling causes defective AT1 cell lineage differentiation ex vivo. Importantly, systemic activation of Wnt signaling at specific stages of lung development can partially rescue the AT1 cell differentiation defect in vivo. These studies show that histone deacetylase 3 expression generates an important developmental niche in the lung mesenchyme through regulation of Wnt signaling, which is required for proper AT1 cell differentiation and lung sacculation.

Wnt ligand/Frizzled 2 receptor signaling regulates tube shape and branch-point formation in the lung through control of epithelial cell shape.

Changing the morphology of a simple epithelial tube to form a highly ramified branching network requires changes in cell behavior that lead to tissue-wide changes in organ shape. How epithelial cells in branched organs modulate their shape and behavior to promote bending and sculpting of the epithelial sheet is not well understood, and the mechanisms underlying this process remain obscure. We show that the Wnt receptor Frizzled 2 (Fzd2) is required for domain branch formation during the initial establishment of the respiratory tree. Live imaging and transcriptome analysis of lung-branching morphogenesis demonstrate that Fzd2 promotes changes in epithelial cell length and shape. These changes in cell morphology deform the developing epithelial tube to generate and maintain new domain branches. Fzd2 controls branch formation and the shape of the epithelial tube by regulating Rho signaling and by the localization of phospho-myosin light chain 2, in turn controlling the changes in the shape of epithelial cells during morphogenesis. This study demonstrates the importance of Wnt/Fzd2 signaling in promoting and maintaining changes in epithelial cell shape that affect development of a branching network.

Vascular endothelial-derived SPARCL1 exacerbates viral pneumonia through pro-inflammatory macrophage activation.

Inflammation induced by lung infection is a double-edged sword, moderating both anti-viral and immune pathogenesis effects; the mechanism of the latter is not fully understood. Previous studies suggest the vasculature is involved in tissue injury. Here, we report that expression of Sparcl1, a secreted matricellular protein, is upregulated in pulmonary capillary endothelial cells (EC) during influenza-induced lung injury. Endothelial overexpression of SPARCL1 promotes detrimental lung inflammation, with SPARCL1 inducing 'M1-like' macrophages and related pro-inflammatory cytokines, while SPARCL1 deletion alleviates these effects. Mechanistically, SPARCL1 functions through TLR4 on macrophages in vitro, while TLR4 inhibition in vivo ameliorates excessive inflammation caused by endothelial Sparcl1 overexpression. Finally, SPARCL1 expression is increased in lung ECs from COVID-19 patients when compared with healthy donors, while fatal COVID-19 correlates with higher circulating SPARCL1 protein levels in the plasma. Our results thus implicate SPARCL1 as a potential prognosis biomarker for deadly COVID-19 pneumonia and as a therapeutic target for taming hyperinflammation in pneumonia.

Vascular Endothelial-derived SPARCL1 Exacerbates Viral Pneumonia Through Pro-Inflammatory Macrophage Activation.

Inflammation upon infectious lung injury is a double-edged sword: while tissue-infiltrating immune cells and cytokines are necessary to control infection, these same factors often aggravate injury. Full appreciation of both the sources and targets of inflammatory mediators is required to facilitate strategies to maintain antimicrobial effects while minimizing off-target epithelial and endothelial damage. Recognizing that the vasculature is centrally involved in tissue responses to injury and infection, we observed that pulmonary capillary endothelial cells (ECs) exhibit dramatic transcriptomic changes upon influenza injury punctuated by profound upregulation of Sparcl1 . Endothelial deletion and overexpression of SPARCL1 implicated this secreted matricellular protein in driving key pathophysiologic symptoms of pneumonia, which we demonstrate result from its effects on macrophage polarization. SPARCL1 induces a shift to a pro-inflammatory "M1-like" phenotype (CD86 + CD206 - ), thereby increasing associated cytokine levels. Mechanistically, SPARCL1 acts directly on macrophages in vitro to induce the pro-inflammatory phenotype via activation of TLR4, and TLR4 inhibition in vivo ameliorates inflammatory exacerbations caused by endothelial Sparcl1 overexpression. Finally, we confirmed significant elevation of SPARCL1 in COVID-19 lung ECs in comparison with those from healthy donors. Survival analysis demonstrated that patients with fatal COVID-19 had higher levels of circulating SPARCL1 protein compared to those who recovered, indicating the potential of SPARCL1 as a biomarker for prognosis of pneumonia and suggesting that personalized medicine approaches might be harnessed to block SPARCL1 and improve outcomes in high-expressing patients.

SWI/SNF chromatin remodeling enzyme ATPases promote cell proliferation in normal mammary epithelial cells.

The ATPase subunits of the SWI/SNF chromatin remodeling enzymes, Brahma (BRM) and Brahma-related gene 1 (BRG1), can induce cell cycle arrest in BRM and BRG1 deficient tumor cell lines, and mice heterozygous for Brg1 are pre-disposed to breast tumors, implicating loss of BRG1 as a mechanism for unregulated cell proliferation. To test the hypothesis that loss of BRG1 can contribute to breast cancer, we utilized RNA interference to reduce the amounts of BRM or BRG1 protein in the nonmalignant mammary epithelial cell line, MCF-10A. When grown in reconstituted basement membrane (rBM), these cells develop into acini that resemble the lobes of normal breast tissue. Contrary to expectations, knockdown of either BRM or BRG1 resulted in an inhibition of cell proliferation in monolayer cultures. This inhibition was strikingly enhanced in three-dimensional rBM culture, although some BRM-depleted cells were later able to resume proliferation. Cells did not arrest in any specific stage of the cell cycle; instead, the cell cycle length increased by approximately 50%. Thus, SWI/SNF ATPases promote cell cycle progression in nonmalignant mammary epithelial cells.

Reliability and diagnostic accuracy of clinical special tests for myelopathy in patients seen for cervical dysfunction.

STUDY DESIGN: Case control study. BACKGROUND: Myelopathy is a clinical diagnosis based largely on initial examination findings during a clinical screen, followed by imaging verification of cord injury or compression. At present, few studies have examined the reliability and diagnostic accuracy of clinical examination measures. OBJECTIVES: To determine the reliability and diagnostic accuracy of neurological tests associated with the diagnosis of myelopathy. METHODS AND MEASURES: Reliability and diagnostic accuracy of 7 frequently used tests and measures and subjective findings associated with myelopathy were examined on consecutive patients with cervical pain. Interrater reliability and diagnostic accuracy values, including posttest probability, based on a pretest probability of 40%, were calculated for each test and for combinations of tests and measures. RESULTS: Four of the 7 diagnostic tests were found to have a substantial interrater reliability. None of the single or clusters of tests yielded low negative likelihood ratios. Of the individual tests, the Babinski sign demonstrated the highest positive likelihood ratio (LR+, 4.0; 95% CI: 1.1-16.6) and posttest probability (73%) for diagnosis, but yielded only a moderate negative likelihood ratio (LR-, 0.7; 95% CI: 0.6-0.9). Combinations of tests did not yield improved accuracy values over single test results. CONCLUSION: This study demonstrated that 4 of 7 tests used to screen for myelopathy offered substantial levels of interrater agreement when used on individuals with cervical dysfunction. None of the tests when performed individually or in combinations are effective for screening; however, the Babinski sign did alter posttest probability more significantly than combinations of test findings. LEVEL OF EVIDENCE: Diagnosis, Level 2b.

Deterministic and probabilistic acute-based environmental risk assessment for naproxen for western Europe.

An environmental risk assessment (ERA) was made for the common nonsteroidal anti-inflammatory drug naproxen. The ERA was performed according to deterministic and probabilistic methods, based on different predicted environmental concentrations (PECs) and measured environmental concentrations (MECs) on the exposure side as well as on published and newly elaborated acute ecotoxicity data on the effects side. Compilation of a large set of MECs allowed a qualification of the various PEC derivations. The European Medicines Evaluation Authority (EMEA) phase I PEC was shown to be far above realistic values, while the refined EMEA phase II (A and B) PECs were not too far from the 95th percentile MEC, in agreement with their nature as local PECs. The western European continental and regional PECs extrapolated based on actual use data, using the European Union system for the evaluation of substances, with the region reconfigured for Germany where most of the available European MECs are from, were in good to very close agreement with the median MECs. No risk to surface waters is apparent by any of the methodologies applied from the current use of naproxen; however, because only insufficient chronic ecotoxicity data are available, this is a preliminary conclusion.

A microRNA-Hippo pathway that promotes cardiomyocyte proliferation and cardiac regeneration in mice.

In contrast to lower vertebrates, the mammalian heart has limited capacity to regenerate after injury in part due to ineffective reactivation of cardiomyocyte proliferation. We show that the microRNA cluster miR302-367 is important for cardiomyocyte proliferation during development and is sufficient to induce cardiomyocyte proliferation in the adult and promote cardiac regeneration. In mice, loss of miR302-367 led to decreased cardiomyocyte proliferation during development. In contrast, increased miR302-367 expression led to a profound increase in cardiomyocyte proliferation, in part through repression of the Hippo signal transduction pathway. Postnatal reexpression of miR302-367 reactivated the cell cycle in cardiomyocytes, resulting in reduced scar formation after experimental myocardial infarction. However, long-term expression of miR302-367 induced cardiomyocyte dedifferentiation and dysfunction, suggesting that persistent reactivation of the cell cycle in postnatal cardiomyocytes is not desirable. This limitation can be overcome by transient systemic application of miR302-367 mimics, leading to increased cardiomyocyte proliferation and mass, decreased fibrosis, and improved function after injury. Our data demonstrate the ability of microRNA-based therapeutic approaches to promote mammalian cardiac repair and regeneration through the transient activation of cardiomyocyte proliferation.

Wnt/ß-catenin signaling accelerates mouse lung tumorigenesis by imposing an embryonic distal progenitor phenotype on lung epithelium.

Although mutations in Kras are present in 21% of lung tumors, there is a high level of heterogeneity in phenotype and outcome among patients with lung cancer bearing similar mutations, suggesting that other pathways are important. Wnt/ß-catenin signaling is a known oncogenic pathway that plays a well-defined role in colon and skin cancer; however, its role in lung cancer is unclear. We have shown here that activation of Wnt/ß-catenin in the bronchiolar epithelium of the adult mouse lung does not itself promote tumor development. However, concurrent activation of Wnt/ß-catenin signaling and expression of a constitutively active Kras mutant (KrasG12D) led to a dramatic increase in both overall tumor number and size compared with KrasG12D alone. Activation of Wnt/ß-catenin signaling altered the KrasG12D tumor phenotype, resulting in a phenotypic switch from bronchiolar epithelium to the highly proliferative distal progenitors found in the embryonic lung. This was associated with decreased E-cadherin expression at the cell surface, which may underlie the increased metastasis of tumors with active Wnt/ß-catenin signaling. Together, these data suggest that activation of Wnt/ß-catenin signaling can combine with other oncogenic pathways in lung epithelium to produce a more aggressive tumor phenotype by imposing an embryonic distal progenitor phenotype and by decreasing E-cadherin expression.