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Background Cryptococcal meningitis (CM) is responsible for 15%–20% of human immunodeficiency virus (HIV)–associated mortalities. CM prevalence has also increased in other immunocompromised populations of transplant recipients, patients with cancer, and individuals on immunomodulatory medication. Methods This retrospective review included 51 definitive patients with CM hospitalized at a tertiary academic medical center in New York City between 2010 and 2023. We assessed clinical features and outcomes of CM, with additional analysis of factors related to antiretroviral therapy (ART) adherence in HIV-infected cases and immunomodulatory medication history of HIV-negative cases. Results The cohort had a mean (standard deviation) age of 47.1 ± 15.1 years, and was predominantly male (37, 72.5%). Of 32 patients with HIV, 3 (9.4%) were newly diagnosed with HIV at the time of CM hospitalization, 5 (15.6%) had recurrent CM, and 2 (6.3%) had a CM relapse. The majority (30, 93.8%) of patients with HIV were ART nonadherent. Of 19 HIV-negative patients, 8 (42.1%) were solid-organ transplant recipients, 5 (26.3%) had autoimmune conditions of sarcoidosis or systemic lupus erythematosus, and 3 (15.8%) had chronic lymphocytic leukemia. Six (11.8%) patients died during hospitalization, 4 of whom had HIV. Conclusions The burden of CM in people with HIV and immunocompromised patients continues even in settings with accessible standard antifungal treatment though interventions of increased ART adherence for those with HIV and antifungal prophylaxis may improve morbidity and mortality. [ABSTRACT FROM AUTHOR]

Objective: Emerging variants and sublineages of SARS‐CoV‐2 have differing disease severity, transmissibility, and immune evasion. The neurological conditions associated with the original strain of SARS‐CoV‐2 are well established. Our study assessed the neurological presentations specific to hospitalized patients during the B.1.1.529 (Omicron) variant surge in New York City. Methods: A total of 178 cases with positive RT‐PCR result within 6 weeks before admission, and subsequent development of select neurological conditions during the SARS‐CoV‐2 B.1.1.529 (Omicron) surge between December 1, 2021 and February 28, 2022, were included from 12,800 SARS‐CoV‐2‐positive hospital admissions. Clinical data from acute hospitalizations were compared to findings of inpatient neurological cases with COVID‐19 infections from the initial surge in NYC in the same hospital system. Results: Compared to SARS‐CoV‐2 infections of the original strain, COVID‐19 cases hospitalized during the Omicron surge (B.1.1.529) were associated with incidental and/or asymptomatic COVID‐19 cases (96, 53.9%) and an increased incidence of pre‐existing neurological and immunocompromising conditions. Encephalopathy, seizures, and stroke remained the most prevalent neurological conditions identified in hospitalized COVID‐19 cases during the study period, reflecting a similar distribution of neurological presentations associated with the original strain. Interpretation: In our cohort of 178 admitted SARS‐CoV‐2‐positive patients with select neurological conditions during the Omicron B.1.1.529 surge, 54% of COVID‐19 cases were considered incidental and/or asymptomatic, and the identified neurological conditions resembled those associated with the original SARS‐CoV‐2 strain. Further studies characterizing neurological presentation in Omicron sublineages and other variants are warranted in an ongoing COVID‐19 pandemic. [ABSTRACT FROM AUTHOR]

Background Herpes simplex virus–1 is the most common cause of sporadic encephalitis worldwide and requires prompt antiviral treatment. Traditionally, herpes simplex virus–1 (HSV-1) cerebrospinal fluid (CSF) testing is conducted using standalone polymerase chain reaction (PCR). The BioFire CSF FilmArray Meningitis/Encephalitis Panel (BioFire ME Panel) was introduced in 2015 at our institution, providing an alternative method of HSV-1 CSF testing. This study assesses the impact of the BioFire ME Panel on duration of intravenous acyclovir treatment. Methods A retrospective review of electronic medical records between 2010 and 2019 was performed. Information on intravenous acyclovir treatment and HSV-1 CSF testing was collected and analyzed. Our descriptive analysis included Mann-Whitney tests, 2 proportion Z-tests, and logistic regression. Results Our CSF HSV-1-negative cohort included 524 BioFire patients (125 pediatric, 399 adult) and 287 standalone PCR patients (115 pediatric, 172 adult). Across both pediatric and adult groups, patients who were tested for HSV-1 with the BioFire ME Panel had shorter average (SD) durations of intravenous acyclovir treatment (pediatric: 2.00 [5.71] days; adult: 3.26 [6.59] days) compared with patients tested with standalone PCR (pediatric: 4.83 [8.62] days; adult: 4.93 [8.46] days; P  < .001). Time from lumbar puncture collection to HSV-1 results was additionally faster on average for the BioFire ME Panel than the standalone PCR (P  < .001). Conclusions The implementation of the BioFire ME Panel shortened CSF HSV-1 PCR result time and intravenous acyclovir duration. The shortened treatment and testing times from the BioFire ME Panel implementation may reduce hospital treatment costs and unnecessary use of antiviral treatments. [ABSTRACT FROM AUTHOR]

In the last decade, the generation and maintenance of organotypic structures has been propelled to the center stage of biomedical research. In the lung, a variety of protocols has been devised to generate organoids mimicking lung structures, but most methods with human cells have complicated lengthy protocols or a progressive decline in differentiation potential and physiological function with increasing passaging. A new study from Sachs et al () seeks to solve these issues, providing a versatile methodology to efficiently isolate, indefinitely culture, and manipulate human airway organoids, potentially allowing the in vitro modeling of a plethora of lung diseases. A new methods resource reports long‐term propagation of human lung epithelium as three dimensional organoids which can be exploited for disease modeling. [ABSTRACT FROM AUTHOR]

Tumors have long been suspected of hijacking stem cell mechanisms used for tissue maintenance and repair. Ge et al. now show that skin tumors exhibit merged chromatin profiles from distinct stem cell lineages. This “lineage infidelity” recreates a state akin to transient wound repair that persists to maintain uncontrolled growth. [ABSTRACT FROM AUTHOR]

New discoveries in stem cell biology are making the biology of solid tissues increasingly complex. Important seminal studies demonstrating the presence of damage-resistant cell populations together with new isolation and characterization techniques suggest that stem cells exist in the adult lung. More detailed in vivo molecular and cellular characterization of bronchioalveolar stem cells (BASCs), other putative lung stem and progenitor cells, and differentiated cells is needed to determine the lineage relationships in adult lung. Lung diseases such as cystic fibrosis or chronic obstructive pulmonary disease, as well as the most common form of lung cancer in the United States, all involve apparent bronchiolar and alveolar cell defects. It is likely that the delicate balance of stem, progenitor, and differentiated cell functions in the lung is critically affected in patients with these devastating diseases. Thus the discovery of BASCs and other putative lung stem cells will lay the foundation for new inroads to understanding lung biology related to lung disease. [ABSTRACT FROM AUTHOR]

Abstract: The airway epithelium is comprised of specialized cell types that play key roles in protecting the lungs from environmental insults. The cellular composition of the murine respiratory epithelium is established during development and different cell types populate specific regions along the airway. Here we show that E2f4-deficiency leads to an absence of ciliated cells from the entire airway epithelium and the epithelium of the submucosal glands in the paranasal sinuses. This defect is particularly striking in the nasal epithelium of E2f4−/− mice where ciliated cells are replaced by columnar secretory cells that produce mucin-like substances. In addition, in the proximal lung, E2f4 loss causes a reduction in Clara cell marker expression indicating that Clara cell development is also affected. These defects arise during embryogenesis and, in the nasal epithelium, appear to be independent of any changes in cell proliferation, the principal process regulated by members of the E2f family of transcription factors. We therefore conclude that E2f4 is required to determine the appropriate development of the airway epithelium. Importantly, the combination of no ciliated cells and excess mucous cells can account for the chronic rhinitis and increased susceptibility to opportunistic infections that causes the postnatal lethality of E2f4 mutant mice. [Copyright &y& Elsevier]

Injury models have suggested that the lung contains anatomically and functionally distinct epithelial stem cell populations. We have isolated such a regional pulmonary stem cell population, termed bronchioal- veolar stem cells (BASCs). Identified at the bronchioalveolar duct junction, BASCs were resistant to bronchiolar and alveolar damage and proliferated during epithelial cell renewal in vivo. BASCs exhibited self-renewal and were multipotent in clonal as- says, highlighting their stem cell properties. Further- more, BASCs expanded in response to oncogenic K-ras in culture and in precursors of lung tumors in vivo. These data support the hypothesis that BASCs are a stem cell population that maintains the bronchiolar Clara cells and alveolar cells of the distal lung and that their transformed counterparts give rise to adenocarcinoma. Although bronchiolar cells and alveolar cells are proposed to be the precursor cells of adenocarcinoma, this work points to BASCs as the putative cells of origin for this subtype of lung cancer. [ABSTRACT FROM AUTHOR]

The article presents two studies conducted by W. Zuo and colleagues and A.E. Vaughan describe different populations of distal lung stem or progenitor cells that help in lung repair. Topics discussed include use of transgenic mice expressing tamoxifen-dependent lacZ under the control of the bovine Krt5 promoter, use of genetic lineage tagging approaches to characterize cell population, and failure of marker integrin-Beta4 in isolating lineage-negative epithelial progenitor (LNEP) cell.

Glycine-12 mutations in the GTPase KRAS (KRASG12) are an initiating event for development of lung adenocarcinoma (LUAD). KRASG12 mutations promote cell-intrinsic rewiring of alveolar type-II progenitor (AT2) cells, but to what extent such changes interplay with lung homeostasis and cell fate pathways is unclear. Here, we generated single-cell RNA-seq (scRNA-seq) profiles from AT2-mesenchyme organoid co-cultures, mice, and stage-IA LUAD patients, identifying conserved regulators of AT2 transcriptional dynamics and defining the impact of KRASG12D mutation with temporal resolution. In AT2WT organoids, we found a transient injury/plasticity state preceding AT2 self-renewal and AT1 differentiation. Early-stage AT2KRAS cells exhibited perturbed gene expression dynamics, most notably retention of the injury/plasticity state. The injury state in AT2KRAS cells of patients, mice, and organoids was distinguishable from AT2WT states via altered receptor expression, including co-expression of ITGA3 and SRC. The combination of clinically relevant KRASG12D and SRC inhibitors impaired AT2KRAS organoid growth. Together, our data show that an injury/plasticity state essential for lung repair is co-opted during AT2 self-renewal and LUAD initiation, suggesting that early-stage LUAD may be susceptible to interventions that target specifically the oncogenic nature of this cell state. Synopsis: KRASG12 mutations promote cell-intrinsic rewiring of alveolar type II progenitor (AT2) cells, but to what extent such changes interplay with lung homeostasis and cell fate pathways is unclear. This study investigates the epigenetic and transcriptomic responses of AT2 cells to specific oncogenic events. AT2WT organoids adopt a transient, transitional injury/plasticity state prior to both AT2 self-renewal and AT1 differentiation. AT2KRAS cells co-opt and retain the transitional injury/plasticity state. AT2KRAS cells in patients, mice, and organoids differ from AT2WT cells by altered gene expression, including co-expression of ITGA3 and SRC. AT2KRAS cells in patients, mice, and organoids can be targeted using clinically-relevant KRASG12D and SRC inhibitors. KRASG12 mutations cause persistence of a normally transient injury/plasticity state in progenitor cells, leading to initiation of lung adenocarcinoma. [ABSTRACT FROM AUTHOR]

Background Assessment of the impact of cerebrospinal fluid (CSF) analysis including investigation for the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential for the optimization of patient care. Methods In this case series, we review patients diagnosed with SARS-CoV-2 undergoing lumbar puncture (LP) admitted to Columbia University Irving Medical Center (New York, NY, USA) from March 1 to May 26, 2020. In a subset of patients, CSF SARS-CoV-2 quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) testing is performed. Results The average age of 27 patients who underwent LP with definitive SARS-CoV-2 (SD) was 37.5 (28.7) years. CSF profiles showed elevated white blood cell counts and protein in 44% and 52% of patients, respectively. LP results impacted treatment decisions in 10 (37%) patients, either by change of antibiotics, influence in disposition decision, or by providing an alternative diagnosis. CSF SARS-CoV-2 qRT-PCR was performed on 8 (30%) patients, with negative results in all samples. Conclusions Among patients diagnosed with SARS-CoV-2, CSF results changed treatment decisions or disposition in over one-third of our patient cohort. CSF was frequently abnormal, though CSF SARS-CoV-2 qRT-PCR was negative in all samples. Further studies are required to define whether CSF SARS-CoV-2 testing is warranted in certain clinical contexts. [ABSTRACT FROM AUTHOR]

This systematic review evaluates the evidence for accuracy of automated analyzers that estimate cerebrospinal fluid (CSF) white blood cell counts (WBC) compared to manual microscopy. Inclusion criteria of original research articles included human subjects, English language, and manual microscopy comparator. PUBMED, EMBASE and Cochrane Review databases were searched through 2019 and QUADAS‐2 Tool was used for assessment of bias. Data were pooled and analyzed by comparison method, using random effects estimation. Among 652 titles, 554 abstracts screened, 104 full‐text review, 111 comparisons from 41 studies were included. Pooled estimates of sensitivity and specificity (n = 7) were 95% (95%‐CI 93%–97%) and 84% (95%‐CI: 64%–96%), respectively. Pooled R2 estimates (n = 29) were 0.95 (95%‐CI: 0.95–0.96); Pooled spearman rho correlation (n = 27) estimates were 0.95 (95% CI 0.95–0.96). Among those comparisons using Bland–Altman analysis (n = 11) pooled mean difference was estimated at 0.98 (95% CI‐0.54–2.5). Among comparisons using Passing‐Bablok regressions (n = 14) the pooled slope was estimated to be 1.05 (95% CI 1.03–1.07). Q tests of homogeneity were all significant with the exception of the Bland–Altman comparisons (I2 10%, p value 0.35). There is good overall accuracy for CSF WBC by automated hematologic analyzers. These findings are limited by the small sample sizes and inconsistent validation methodology in the reviewed studies. [ABSTRACT FROM AUTHOR]

The authors discusses a report within the issue by M. E. Kumar et al. on the identification of distinct pools of mesenchymal progenitor cells that develop into stromal tissues of the mammalian lung during the embryonic phase. Topics include the differentiation of mesenchymal progenitor cells, the role of mesenchymal progenitors in the budding phase of early lung morphogenesis in mice, and interactions between neighboring epithelial, endothelial, and mesenchymal cells in the lung.

The authors discuss various studies on oncogenic mutation of Kirsten rat sarcoma viral oncogene homologue (K-RAS) that are common in the lung cancer, adenocarcinoma. They state that K-Ras-activated cells may pass through several forms before its formation of tumors cells. They also mention that lung adenocarcinomas develop from different cells influenced by several factors including developmental, environmental and genetic.

Unbiased high-throughput sequencing (HTS) has enabled new insights into the diversity of agents implicated in central nervous system (CNS) infections. The addition of positive selection capture methods to HTS has enhanced the sensitivity while reducing sequencing costs and the complexity of bioinformatic analysis. Here we report the use of virus capture-based sequencing for vertebrate viruses (VirCapSeq-VERT) and bacterial capture sequencing (BacCapSeq) in investigating CNS infections. Thirty-four samples were categorized: (1) patients with definitive CNS infection by routine testing; (2) patients meeting clinically the Brighton criteria (BC) for meningoencephalitis; (3) patients with presumptive infectious etiology highest on the differential. RNA extracts from cerebrospinal fluid (CSF) were used for VirCapSeq-VERT, and DNA extracts were used for BacCapSeq analysis. Among 8 samples from known CNS infections in group 1, VirCapSeq and BacCapSeq confirmed 3 expected diagnoses (42.8%), were negative in 2 (25%), yielded an alternative result in 1 (11.1%), and did not detect 2 expected negative pathogens. The confirmed cases identified HHV-6, HSV-2, and VZV while the negative samples included JCV and HSV-2. In groups 2 and 3, 11/26 samples (42%) were positive for at least one pathogen; however, 27% of the total samples (7/26) were positive for commensal organisms. No microbial nucleic acids were detected in negative control samples. HTS showed limited promise for pathogen identification in presumed CNS infectious diseases in our small sample. Before conducting larger-scale prospective studies to assess the clinical value of this novel technique, clinicians should understand the benefits and limitations of using this modality. [ABSTRACT FROM AUTHOR]

Objectives: Early presentation and workup for acute infectious (IE) and autoimmune encephalitis (AE) are similar. This study aims to identify routine laboratory markers at presentation that are associated with IE or AE. Methods: This was a multi‐center retrospective study at three tertiary care hospitals in New York City analyzing demographic and clinical data from patients diagnosed with definitive encephalitis based on a confirmed pathogen and/or autoantibody and established criteria for clinical syndromes. Results: Three hundred and thirty‐three individuals with confirmed acute meningoencephalitis were included. An infectious‐nonbacterial (NB) pathogen was identified in 151/333 (45.40%), bacterial pathogen in 95/333 (28.50%), and autoantibody in 87/333 (26.10%). NB encephalitis was differentiated from AE by the presence of fever (NB 62.25%, AE 24.10%; p < 0.001), higher CSF white blood cell (WBC) (median 78 cells/μL, 8.00 cells/μL; p < 0.001), higher CSF protein (76.50 mg/dL, 40.90 mg/dL; p < 0.001), lower CSF glucose (58.00 mg/dL, 69.00 mg/dL; p < 0.001), lower serum WBC (7.80 cells/μL, 9.72 cells/μL; p < 0.050), higher erythrocyte sedimentation rate (19.50 mm/HR, 13.00 mm/HR; p < 0.05), higher C‐reactive protein (6.40 mg/L, 1.25 mg/L; p = 0.005), and lack of antinuclear antibody titers (>1:40; NB 11.54%, AE 32.73%; p < 0.001). CSF‐to‐serum WBC ratio was significantly higher in NB compared to AE (NB 11.3, AE 0.99; p < 0.001). From these findings, the association of presenting with fever, CSF WBC ≥50 cells/μL, and CSF protein ≥75 mg/dL was explored in ruling‐out AE. When all three criteria are present, an AE was found to be highly unlikely (sensitivity 92%, specificity 75%, negative predictive value 95%, and positive predictive value 64%). Interpretations: Specific paraclinical data at initial presentation may risk stratify which patients have an IE versus AE. [ABSTRACT FROM AUTHOR]

Abstract: Tumors have been increasingly recognized as organs with a complexity that approaches, and may even exceed, that of healthy tissues. When viewed from this perspective, the biology of a tumor can be understood only by studying tumor cell heterogeneity and the microenvironment that is constructed during the course of tumorigenesis and malignant progression. Recent work has revealed the existence of cancer stem cells, the “bugs”, with the capacity for self-renewal and tumor propagation. In addition, it is now recognized that the tumor microenvironment, the “bed”, plays a critical role in supporting cancer stem cells and also may promote neoplasia and malignant progression. The interdependence of the cell-intrinsic features of cancer, including the cancer stem cell “bugs” and the tumor microenvironment “bed”, is only beginning to be understood. In this review, we highlight the rapidly evolving concepts about the interactions between tumor stem cells and their microenvironment, the insights gained from studying their normal tissue counterparts, and the questions and controversies surrounding this area of research, with an emphasis on breast and lung cancer. Finally, we address evidence supporting the notion that eliminating the bed as well as the bugs should lead to more effective and personalized cancer treatments that improve patient outcome. [Copyright &y& Elsevier]

A number of novel approaches for repair and regeneration of injured lung have developed over the past several years. These include a better understanding of endogenous stem and progenitor cells in the lung that can function in reparative capacity as well as extensive exploration of the potential efficacy of administering exogenous stem or progenitor cells to function in lung repair. Recent advances in ex vivo lung engineering have also been increasingly applied to the lung. The current status of these approaches as well as initial clinical trials of cell therapies for lung diseases are reviewed below. [ABSTRACT FROM AUTHOR]

Understanding the pathways that control epithelial carcinogenesis is vital to the development of effective treatments. The Polycomb group family member Bmi1 is overexpressed in numerous epithelial tumors, but its role in their development has not been established. We now show a key role for Bmi1 in lung adenocarcinoma. Whereas lung development occurs normally in Bmi1-deficient mice, loss of Bmi1 decreases the number and progression of lung tumors at a very early point in an oncogenic K-ras-initiated mouse model of lung cancer. This correlates with a defect in the ability of Bmi1-deficient putative bronchiolalveolar stem cells (BASCs) to proliferate in response to the oncogenic stimulus. Notably, in the absence of oncogenic K-ras, Bmi1-deficient BASCs show impaired proliferation and self-renewal capacity in culture and after lung injury in vivo. Abrogated lung cancer development and BASC self-renewal occur partially in a p19A-dependent manner. Our data suggest that Bmi1 deficiency suppresses tumor development by limiting the expansion potential of BASCs, the apparent lung cancer cells of origin. Because Bmi1 is elevated in additional tumor types, this suggests that Bmi1 plays a key role in regulating proliferation of both stem cells and tumor cells in diverse adult epithelial tissues. [ABSTRACT FROM AUTHOR]

Genetic and cytologic data from Saccharomyces cerevisiae and mammals implicate the Mre11 complex, consisting of Mre11, Rad50, and Nbs1, as a sensor of DNA damage, and indicate that the complex influences the activity of ataxia-telangiectasia mutated (ATM) in the DNA damage response. Rad50S/S mice exhibit precipitous apoptotic attrition of hematopoietic cells. We generated ATM- and Chk2-deficient Rad50S/S mice and found that Rad50S/S cellular attrition was strongly ATM and Chk2 dependent. The hypomorphic Mre11ATLD1 and Nbs1ΔB alleles conferred similar rescue of Rad50S/S-dependent hematopoietic failure. These data indicate that the Mre11 complex activates an ATM-Chk2-dependent apoptotic pathway. We find that apoptosis and cell cycle checkpoint activation are parallel outcomes of the Mre11 complex-ATM pathway. Conversely, the Rad50S mutation mitigated several phenotypic features of ATM deficiency. We propose that the Rad50S allele is hypermorphic for DNA damage signaling, and that the resulting constitutive low-level activation of the DNA damage response accounts for the partial suppression of ATM deficiency in Rad50S/S Atm-/- mice. [ABSTRACT FROM AUTHOR]

The role of adjunctive corticosteroids in reducing morbidity and mortality of viral CNS infections remains poorly defined. Clinicians are often left in a quagmire regarding steroid use in complex and rapidly evolving viral CNS infections. Limited studies have explored the underlying mechanisms behind the potential benefit of steroids. Here, we describe steroid use in three cases of viral CNS disease: varicella zoster virus (VZV), Powassan virus, and influenza A-associated acute necrotizing encephalopathy. [ABSTRACT FROM AUTHOR]

Many patients with SARS-CoV-2 infection develop neurological signs and symptoms, though, to date, little evidence exists that primary infection of the brain is a significant contributing factor. We present the clinical, neuropathological, and molecular findings of 41 consecutive patients with SARS-CoV-2 infections who died and underwent autopsy in our medical center. The mean age was 74 years (38-97 years), 27 patients (66%) were male and 34 (83%) were of Hispanic/Latinx ethnicity. Twenty-four patients (59%) were admitted to the intensive care unit (ICU). Hospital-associated complications were common, including 8 (20%) with deep vein thrombosis/pulmonary embolism (DVT/PE), 7 (17%) patients with acute kidney injury requiring dialysis, and 10 (24%) with positive blood cultures during admission. Eight (20%) patients died within 24 hours of hospital admission, while 11 (27%) died more than 4 weeks after hospital admission. Neuropathological examination of 20-30 areas from each brain revealed hypoxic/ischemic changes in all brains, both global and focal; large and small infarcts, many of which appeared hemorrhagic; and microglial activation with microglial nodules accompanied by neuronophagia, most prominently in the brainstem. We observed sparse T lymphocyte accumulation in either perivascular regions or in the brain parenchyma. Many brains contained atherosclerosis of large arteries and arteriolosclerosis, though none had evidence of vasculitis. Eighteen (44%) contained pathologies of neurodegenerative diseases, not unexpected given the age range of our patients. We examined multiple fresh frozen and fixed tissues from 28 brains for the presence of viral RNA and protein, using quantitative reverse-transcriptase PCR (qRT-PCR), RNAscope, and immunocytochemistry with primers, probes, and antibodies directed against the spike and nucleocapsid regions. qRT-PCR revealed low to very low, but detectable, viral RNA levels in the majority of brains, although they were far lower than those in nasal epithelia. RNAscope and immunocytochemistry failed to detect viral RNA or protein in brains. Our findings indicate that the levels of detectable virus in COVID-19 brains are very low and do not correlate with the histopathological alterations. These findings suggest that microglial activation, microglial nodules and neuronophagia, observed in the majority of brains, do not result from direct viral infection of brain parenchyma, but rather likely from systemic inflammation, perhaps with synergistic contribution from hypoxia/ischemia. Further studies are needed to define whether these pathologies, if present in patients who survive COVID-19, might contribute to chronic neurological problems. [ABSTRACT FROM AUTHOR]

The population is aging at a rate never seen before in human history. As the number of elderly adults grows, it is imperative we expand our understanding of the underpinnings of aging biology. Human lungs are composed of a unique panoply of cell types that face ongoing chemical, mechanical, biological, immunological, and xenobiotic stress over a lifetime. Yet, we do not fully appreciate the mechanistic drivers of lung aging and why age increases the risk of parenchymal lung disease, fatal respiratory infection, and primary lung cancer. Here, we review the molecular and cellular aspects of lung aging, local stress response pathways, and how the aging process predisposes to the pathogenesis of pulmonary disease. We place these insights into context of the COVID-19 pandemic and discuss how innate and adaptive immunity within the lung is altered with age. Recent cellular and molecular studies have given insight into why the incidence and/or severity of many lung diseases, from lung cancer to COVID-19, increase with age. [ABSTRACT FROM AUTHOR]

There is a growing appreciation of the role of lung stem/progenitor cells in the development and perpetuation of chronic lung disease including idiopathic pulmonary fibrosis. Human amniotic epithelial cells (hAECs) were previously shown to improve lung architecture in bleomycin-induced lung injury, with the further suggestion that hAECs obtained from term pregnancies possessed superior anti-fibrotic properties compared with their preterm counterparts. In the present study, we aimed to elucidate the differential effects of hAECs from term and preterm pregnancies on lung stem/progenitor cells involved in the repair. Here we showed that term hAECs were better able to activate bronchioalveolar stem cells (BASCs) and type 2 alveolar epithelial cells (AT2s) compared with preterm hAECs following bleomycin challenge. Further, we observed that term hAECs restored TGIF1 and TGFß2 expression levels, while increasing c-MYC expression despite an absence of significant changes to Wnt/ß-catenin signaling. In vitro, term hAECs increased the average size and numbers of BASC and AT2 colonies. The gene expression levels of Wnt ligands were higher in term hAECs, and the expression levels of BMP4, CCND1 and CDC42 were only increased in the BASC and AT2 organoids co-cultured with hAECs from term pregnancies but not preterm pregnancies. In conclusion, term hAECs were more efficient at activating the BASC niche compared with preterm hAECs. The impact of gestational age and/or complications leading to preterm delivery should be considered when applying hAECs and other gestational tissue-derived stem and stem-like cells therapeutically. [ABSTRACT FROM AUTHOR]

Widefield calcium imaging enables recording of large-scale neural activity across the mouse dorsal cortex. In order to examine the relationship of these neural signals to the resulting behavior, it is critical to demix the recordings into meaningful spatial and temporal components that can be mapped onto well-defined brain regions. However, no current tools satisfactorily extract the activity of the different brain regions in individual mice in a data-driven manner, while taking into account mouse-specific and preparation-specific differences. Here, we introduce Localized semi-Nonnegative Matrix Factorization (LocaNMF), a method that efficiently decomposes widefield video data and allows us to directly compare activity across multiple mice by outputting mouse-specific localized functional regions that are significantly more interpretable than more traditional decomposition techniques. Moreover, it provides a natural subspace to directly compare correlation maps and neural dynamics across different behaviors, mice, and experimental conditions, and enables identification of task- and movement-related brain regions. Author summary: While recording from multiple regions of the brain, how does one best incorporate prior information about anatomical regions while accurately representing the data? Here, we introduce Localized semi-NMF (LocaNMF), an algorithm that efficiently decomposes widefield video data into meaningful spatial and temporal components that can be decoded and compared across different behavioral sessions and experimental conditions. Mapping the inferred components onto well-defined brain regions using a widely-used brain atlas provides an interpretable, stable decomposition. LocaNMF allows us to satisfactorily extract the activity of the different brain regions in individual mice in a data-driven manner, while taking into account mouse-specific and preparation-specific differences. [ABSTRACT FROM AUTHOR]

Adult stem cells are rare, undifferentiated cells found in all tissues of the body. Although normally kept in a quiescent, nondividing state, these cells can proliferate and differentiate to replace naturally dying cells within their tissue and to repair its wounds in response to injury. Due to their proliferative nature and ability to regenerate tissue, adult stem cells have the potential to treat a variety of degenerative diseases as well as aging. In addition, since stem cells are often thought to be the source of malignant tumors, understanding the mechanisms that keep their proliferative abilities in check can pave the way for new cancer therapies. While adult stem cells have had limited practical and clinical applications to date, several clinical trials of stem cell–based therapies are underway. This report details recent research presented at the New York Academy of Sciences on March 14, 2019 on understanding the factors that regulate stem cell activity and differentiation, with the hope of translating these findings into the clinic. [ABSTRACT FROM AUTHOR]

The lung contains multiple progenitor cell types, but how their responses are choreographed during injury repair and whether this changes with age is poorly understood. We report that histone H3 lysine 9 di-methylation (H3K9me2), mediated by the methyltransferase G9a, regulates the dynamics of distal lung epithelial progenitor cells and that this regulation deteriorates with age. In aged mouse lungs, H3K9me2 loss coincided with fewer alveolar type 2 (AT2) cell progenitors and reduced alveolar regeneration but increased the frequency and activity of multipotent bronchioalveolar stem cells (BASCs) and bronchiolar progenitor club cells. H3K9me2 depletion in young mice decreased AT2 progenitor activity and impaired alveolar injury repair. Conversely, H3K9me2 depletion increased chromatin accessibility of bronchiolar cell genes, increased BASC frequency, and accelerated bronchiolar cell injury repair. These findings indicate that during aging, the epigenetic regulation that coordinates lung progenitor cells' regenerative responses becomes dysregulated, aiding our understanding of age-related susceptibility to lung disease. [Display omitted] • Old lungs have fewer alveolar type II cells and more bronchioalveolar stem cells (BASCs) • Epithelial cells in old lungs have significantly lower levels of H3K9me2 • H3K9me2 loss slows alveolar regeneration and enhances airway epithelial regeneration • Loss of H3K9me2 increases airway epithelium gene accessibility and BASC frequency Rowbotham et al. report that changes in the frequency of epithelial progenitor cells in old lungs are downstream of reductions in the levels of the histone modification H3K9me2. Depleting H3K9me2 in young mice changes the regenerative dynamics of the distal lung to resemble those of old animals. [ABSTRACT FROM AUTHOR]

Background: Despite advances in neonatal care, bronchopulmonary dysplasia (BPD) remains a significant contributor to infant mortality and morbidity. While human amnion epithelial cells (hAECs) have shown promise in small and large animal models of BPD, there is scarce information on long-term benefit and clinically relevant questions surrounding administration strategy remain unanswered. In assessing the therapeutic potential of hAECs, we investigated the impact of cell dosage, administration routes and timing of treatment in a pre-clinical model of BPD. Methods: Lipopolysaccharide was introduced intra-amniotically at day 16 of pregnancy prior to exposure to 65% oxygen (hyperoxia) at birth. hAECs were administered either 12 hours (early) or 4 days (late) after hyperoxia commenced. Collective lung tissues were subjected to histological analysis, multikine ELISA for inflammatory cytokines, FACS for immune cell populations and 3D lung stem cell culture at neonatal stage (postnatal day 7 and 14). Invasive lung function test and echocardiography were applied at 6 and 10 weeks of age. Results: hAECs improved the tissue-to-airspace ratio and septal crest density in a dose-dependent manner, regardless of administration route. Early administration of hAECs, coinciding with the commencement of postnatal hyperoxia, was associated with reduced macrophages, dendritic cells and natural killer cells. This was not the case if hAECs were administered when lung injury was established. Fittingly, early hAEC treatment was more efficacious in reducing interleukin-1β, tumour necrosis factor alpha and monocyte chemoattractant protein-1 levels. Early hAEC treatment was also associated with reduced airway hyper-responsiveness and normalisation of pressure-volume loops. Pulmonary hypertension and right ventricle hypertrophy were also prevented in the early hAEC treatment group, and this persisted until 10 weeks of age. Conclusions: Early hAEC treatment appears to be advantageous over late treatment. There was no difference in efficacy between intravenous and intratracheal administration. The benefits of hAEC administration resulted in long-term improvements in cardiorespiratory function. [ABSTRACT FROM AUTHOR]

Elevated levels of the β-amyloid peptide (Aβ) are thought to contribute to cognitive and behavioral impairments observed in Alzheimer's disease (AD). Protein phosphatase 2A (PP2A) participates in multiple molecular pathways implicated in AD, and its expression and activity are reduced in postmortem brains of AD patients. PP2A is regulated by protein methylation, and impaired PP2A methylation is thought to contribute to increased AD risk in hyperhomocysteinemic individuals. To examine further the link between PP2A and AD, we generated transgenic mice that overexpress the PP2A methylesterase, protein phosphatase methylesterase-1 (PME-1), or the PP2A methyltransferase, leucine carboxylmethyltransferase-1 (LCMT-1), and examined the sensitivity of these animals to behavioral and electrophysiological impairments caused by exogenous Aβ exposure. We found that PME-1 overexpression enhanced these impairments, whereas LCMT-1 overexpression protected against Aβ-induced impairments. Neither transgene affected Aβ production or the electrophysiological response to low concentrations of Aβ, suggesting that these manipulations selectively affect the pathological response to elevated Aβ levels. Together these data identify a molecular mechanism linking PP2A to the development of AD-related cognitive impairments that might be therapeutically exploited to target selectively the pathological effects caused by elevated Aβ levels in AD patients. [ABSTRACT FROM AUTHOR]

Non-small-cell lung cancer is the leading cause of cancer-related death worldwide. Chemotherapies such as the topoisomerase II (TopoII) inhibitor etoposide effectively reduce disease in a minority of patients with this cancer; therefore, alternative drug targets, including epigenetic enzymes, are under consideration for therapeutic intervention. A promising potential epigenetic target is the methyltransferase EZH2, which in the context of the polycomb repressive complex 2 (PRC2) is well known to tri-methylate histone H3 at lysine 27 (H3K27me3) and elicit gene silencing. Here we demonstrate that EZH2 inhibition has differential effects on the TopoII inhibitor response of non-small-cell lung cancers in vitro and in vivo. EGFR and BRG1 mutations are genetic biomarkers that predict enhanced sensitivity to TopoII inhibitor in response to EZH2 inhibition. BRG1 loss-of-function mutant tumours respond to EZH2 inhibition with increased S phase, anaphase bridging, apoptosis and TopoII inhibitor sensitivity. Conversely, EGFR and BRG1 wild-type tumours upregulate BRG1 in response to EZH2 inhibition and ultimately become more resistant to TopoII inhibitor. EGFR gain-of-function mutant tumours are also sensitive to dual EZH2 inhibition and TopoII inhibitor, because of genetic antagonism between EGFR and BRG1. These findings suggest an opportunity for precision medicine in the genetically complex disease of non-small-cell lung cancer. [ABSTRACT FROM AUTHOR]

Non-small-cell lung cancers (NSCLCs), the most common lung cancers, are known to have diverse pathological features. During the past decade, in-depth analyses of lung cancer genomes and signalling pathways have further defined NSCLCs as a group of distinct diseases with genetic and cellular heterogeneity. Consequently, an impressive list of potential therapeutic targets was unveiled, drastically altering the clinical evaluation and treatment of patients. Many targeted therapies have been developed with compelling clinical proofs of concept; however, treatment responses are typically short-lived. Further studies of the tumour microenvironment have uncovered new possible avenues to control this deadly disease, including immunotherapy. [ABSTRACT FROM AUTHOR]

Non-small-cell lung cancers (NSCLCs), the most common lung cancers, are known to have diverse pathological features. During the past decade, in-depth analyses of lung cancer genomes and signalling pathways have further defined NSCLCs as a group of distinct diseases with genetic and cellular heterogeneity. Consequently, an impressive list of potential therapeutic targets was unveiled, drastically altering the clinical evaluation and treatment of patients. Many targeted therapies have been developed with compelling clinical proofs of concept; however, treatment responses are typically short-lived. Further studies of the tumour microenvironment have uncovered new possible avenues to control this deadly disease, including immunotherapy. [ABSTRACT FROM AUTHOR]

Lung cancer is notorious for its ability to metastasize, but the pathways regulating lung cancer metastasis are largely unknown. An in vitro system designed to discover factors critical for lung cancer cell migration identified brain-derived neurotrophic factor, which stimulates cell migration through activation of tropomyosin-related kinase B (TrkB; also called NTRK2). Knockdown of TrkB in human lung cancer cell lines significantly decreased their migratory and metastatic ability in vitro and in vivo. In an autochthonous lung adenocarcinoma model driven by activated oncogenic Kras and p53 loss, TrkB deficiency significantly reduced metastasis. Hypoxia-inducible factor-1 directly regulated TrkB expression, and, in turn, TrkB activated Akt signaling in metastatic lung cancer cells. Finally, TrkB expression was correlated with metastasis in patient samples, and TrkB was detected more often in tumors that did not have Kras or epidermal growth factor receptor mutations. These studies demonstrate that TrkB is an important therapeutic target in metastatic lung adenocarcinoma. [ABSTRACT FROM AUTHOR]

Metastasis is the leading cause of morbidity for lung cancer patients. Here we demonstrate that murine tumor propagating cells ( TPCs) with the markers Sca1 and CD24 are enriched for metastatic potential in orthotopic transplantation assays. CD24 knockdown decreased the metastatic potential of lung cancer cell lines resembling TPCs. In lung cancer patient data sets, metastatic spread and patient survival could be stratified with a murine lung TPC gene signature. The TPC signature was enriched for genes in the Hippo signaling pathway. Knockdown of the Hippo mediators Yap1 or Taz decreased in vitro cellular migration and transplantation of metastatic disease. Furthermore, constitutively active Yap was sufficient to drive lung tumor progression in vivo. These results demonstrate functional roles for two different pathways, CD24-dependent and Yap/ Taz-dependent pathways, in lung tumor propagation and metastasis. This study demonstrates the utility of TPCs for identifying molecules contributing to metastatic lung cancer, potentially enabling the therapeutic targeting of this devastating disease. [ABSTRACT FROM AUTHOR]

Summary: Lung stem cells are instructed to produce lineage-specific progeny through unknown factors in their microenvironment. We used clonal 3D cocultures of endothelial cells and distal lung stem cells, bronchioalveolar stem cells (BASCs), to probe the instructive mechanisms. Single BASCs had bronchiolar and alveolar differentiation potential in lung endothelial cell cocultures. Gain- and loss-of-function experiments showed that BMP4-Bmpr1a signaling triggers calcineurin/NFATc1-dependent expression of thrombospondin-1 (Tsp1) in lung endothelial cells to drive alveolar lineage-specific BASC differentiation. Tsp1 null mice exhibited defective alveolar injury repair, confirming a crucial role for the BMP4-NFATc1-TSP1 axis in lung epithelial differentiation and regeneration in vivo. Discovery of this pathway points to methods to direct the derivation of specific lung epithelial lineages from multipotent cells. These findings elucidate a pathway that may be a critical target in lung diseases and provide tools to understand the mechanisms of respiratory diseases at the single-cell level. [Copyright &y& Elsevier]

The Hippo-YAP pathway is an emerging signalling cascade involved in the regulation of stem cell activity and organ size. To identify components of this pathway, we performed an RNAi-based kinome screen in human cells. Our screen identified several kinases not previously associated with Hippo signalling that control multiple cellular processes. One of the hits, LKB1, is a common tumour suppressor whose mechanism of action is only partially understood. We demonstrate that LKB1 acts through its substrates of the microtubule affinity-regulating kinase family to regulate the localization of the polarity determinant Scribble and the activity of the core Hippo kinases. Our data also indicate that YAP is functionally important for the tumour suppressive effects of LKB1. Our results identify a signalling axis that links YAP activation with LKB1 mutations, and have implications for the treatment of LKB1-mutant human malignancies. In addition, our findings provide insight into upstream signals of the Hippo-YAP signalling cascade. [ABSTRACT FROM AUTHOR]

Obliterative bronchiolitis (OB) remains the most significant cause of death in long-term survival of lung transplantation. Using an established murine heterotopic tracheal allograft model, the effects of different routes of administration of bone marrow-derived multipotent stromal cells (MSCs) on the development of OB were evaluated. Tracheas from BALB/c mice were implanted into the subcutaneous tissue of major histocompatibility complex- (MHC-) disparate C57BL/6 mice. At the time of transplant, bone marrow-derived MSCs were administered either systemically or locally or via a combination of the two routes. The allografts were explanted at various time points after transplantation and were evaluated for epithelial integrity, inflammatory cell infiltration, fibrosis, and luminal obliteration. We found that the most effective route of bone marrow-derived MSC administration is the combination of systemic and local delivery. Treatment of recipient mice with MSCs suppressed neutrophil, macrophage, and T-cell infiltration and reduced fibrosis. These beneficial effects were observed despite lack of significant MSC epithelial engraftment or new epithelial cell generation. Our study suggests that optimal combination of systemic and local delivery of MSCs may ameliorate the development of obliterative airway disease through modulation of immune response. [ABSTRACT FROM AUTHOR]

Progression of premalignant lesions is restrained by oncogene-induced senescence. Oncogenic Ras triggers senescence in many organs, including the lung, which exhibits high levels of the angiogenesis inhibitor thrombospondin-1 (TSP-1). The contribution of TSP-1 upregulation to the modulation of tumorigenesis in the lung is unclear. Using a mouse model of lung cancer, we have shown that TSP-1 plays a critical and cell-autonomous role in suppressing Kms-induced lung tumorigenesis independent of its antiangiogenic function. Overall survival was decreased in a Kras-driven mouse model of lung cancer on a Tsp-1-/- background. We found that oncogenic Kras-induced TSP-1 upregulation in a p53-dependent manner. TSP-1 functioned in a positive feedback loop to stabilize p53 by interacting directly with activated ERK. TSP-1 tethering of ERK in the cytoplasm promoted a level of MAPK signaling that was sufficient to sustain p53 expression and a senescence response. Our data identify TSP-1 as a p53 target that contributes to maintaining Ras-induced senescence in the lung. [ABSTRACT FROM AUTHOR]

Bronchopulmonary dysplasia (BPD) remains a major complication of prematurity resulting in significant morbidity and mortality. The pathology of BPD is multifactorial and leads to alveolar simplification and distal lung injury. Previous studies have shown a beneficial effect of systemic treatment with bone marrow-derived mesenchymal stromal cells (MSCs) and MSC-conditioned media (MSC-CM) leading to amelioration of the lung parenchymal and vascular injury in vivo in the hyperoxia murine model of BPD. It is possible that the beneficial response from the MSCs is at least in part due to activation of endogenous lung epithelial stem cells. Bronchioalveolar stem cells (BASCs) are an adult lung stem cell population capable of self-renewal and differentiation in culture, and BASCs proliferate in response to bronchiolar and alveolar lung injury in vivo. Systemic treatment of neonatal hyperoxia-exposed mice with MSCs or MSC-CM led to a significant increase in BASCs compared with untreated controls. Treatment of BASCs with MSC-CM in culture showed an increase in growth efficiency, indicating a direct effect of MSCs on BASCs. Lineage tracing data in bleomycin-treated adult mice showed that Clara cell secretory protein-expressing cells including BASCs are capable of contributing to alveolar repair after lung injury. MSCs and MSC-derived factors may stimulate BASCs to play a role in the repair of alveolar lung injury found in BPD and in the restoration of distal lung cell epithelia. This work highlights the potential important role of endogenous lung stem cells in the repair of chronic lung diseases. [ABSTRACT FROM AUTHOR]

Summary: Polycomb repressive complexes (PRCs) play key roles in developmental epigenetic regulation. Yet the mechanisms that target PRCs to specific loci in mammalian cells remain incompletely understood. In this study we show that Bmi1, a core component of Polycomb Repressive Complex 1 (PRC1), binds directly to the Runx1/CBFβ transcription factor complex. Genome-wide studies in megakaryocytic cells demonstrate significant chromatin occupancy overlap between the PRC1 core component Ring1b and Runx1/CBFβ and functional regulation of a considerable fraction of commonly bound genes. Bmi1/Ring1b and Runx1/CBFβ deficiencies generate partial phenocopies of one another in vivo. We also show that Ring1b occupies key Runx1 binding sites in primary murine thymocytes and that this occurs via PRC2-independent mechanisms. Genetic depletion of Runx1 results in reduced Ring1b binding at these sites in vivo. These findings provide evidence for site-specific PRC1 chromatin recruitment by core binding transcription factors in mammalian cells. [ABSTRACT FROM AUTHOR]

Summary: In mice, Lkb1 deletion and activation of KrasG12D results in lung tumors with a high penetrance of lymph node and distant metastases. We analyzed these primary and metastatic de novo lung cancers with integrated genomic and proteomic profiles, and have identified gene and phosphoprotein signatures associated with Lkb1 loss and progression to invasive and metastatic lung tumors. These studies revealed that SRC is activated in Lkb1-deficient primary and metastatic lung tumors, and that the combined inhibition of SRC, PI3K, and MEK1/2 resulted in synergistic tumor regression. These studies demonstrate that integrated genomic and proteomic analyses can be used to identify signaling pathways that may be targeted for treatment. [Copyright &y& Elsevier]

Acute exposure to ionizing radiation can cause lethal damage to the gastrointestinal (Gl) tract, a condition called the Gl syndrome. Whether the target cells affected by radiation to cause the Gl syndrome are derived from the epithelium or endothelium and whether the target cells die by apoptosis or other mechanisms are controversial issues. Studying mouse models, we found that selective deletion of the proapoptotic genes Bak1 and Bax from the Gl epithelium or from endothelial cells did not protect mice from developing the Gl syndrome after sub-total-body gamma irradiation. In contrast, selective deletion of p53 from the Gl epithelium, but not from endothelial cells, sensitized irradiated mice to the Gl syndrome. Transgenic mice overexpressing p53 in all tissues were protected from the Gl syndrome after irradiation. These results suggest that the Gl syndrome is caused by the death of Gl epithelial cells and that these epithelial cells die by a mechanism that is regulated by p53 but independent of apoptosis. [ABSTRACT FROM AUTHOR]

Background: Non-small cell lung cancer (NSCLC) is the most common cause of cancer-related death in Western countries. Developing more effective NSCLC therapeutics will require the elucidation of the genetic and biochemical bases for this disease. Bronchioalveolar stem cells (BASCs) are a putative cancer stem cell population in mouse models of oncogenic K-rasinduced lung adenocarcinoma, an histologic subtype of NSCLC. The signals activated by oncogenic K-ras that mediate BASC expansion have not been fully defined. Methodology/Principal Findings: We used genetic and pharmacologic approaches to modulate the activity of phosphatidylinositol 3-kinase (PI3K), a key mediator of oncogenic K-ras, in two genetic mouse models of lung adenocarcinoma. Oncogenic K-ras-induced BASC accumulation and tumor growth were blocked by treatment with a small molecule PI3K inhibitor and enhanced by inactivation of phosphatase and tensin homologue deleted from chromosome 10, a negative regulator of PI3K. Conclusions/Significance: We conclude that PI3K is a critical regulator of BASC expansion, supporting treatment strategies to target PI3K in NSCLC patients. [ABSTRACT FROM AUTHOR]

Using gene expression profiling, we identified cathepsin cysteine proteases as highly up-regulated genes in a mouse model of human lung adenocarcinoma. Overexpression of cathepsin pro- teases in these lung tumors was confirmed by immunohistochemistry and Western blotting. Therefore, an optical probe activated by cathepsin proteases was selected to detect murine lung tumors in vivo as small as 1 mm in diameter and spatially separated. We generated 3D maps of the fluorescence signal and fused them with anatomical computed tomography images to show a close correlation between fluorescence signal and tumor burden. By serially imaging the same mouse, optical imaging was used to follow tumor progression. This study demonstrates the capability for molecular imaging of a primary lung tumor by using endogenous proteases expressed by a tumor. It also highlights the feasibility of using gene expression profiling to identify molecular targets for imaging lung cancer. [ABSTRACT FROM AUTHOR]

Vaccine induced immune mediated thrombocytopenia or VITT, is a recent and rare phenomenon of thrombosis with thrombocytopenia, frequently including cerebral venous thromboses (CVT), that has been described following vaccination with adenovirus vaccines ChAdOx1 nCOV-19 (AstraZeneca) and Ad26.COV2·S Johnson and Johnson (Janssen/J&J). The evaluation and management of suspected cases of CVT post COVID-19 vaccination are critical skills for a broad range of healthcare providers. A collaborative comprehensive review of literature was conducted among a global group of expert neurologists and hematologists. Strategies for rapid evaluation and treatment of the CVT in the context of possible VITT exist, including inflammatory marker measurements, PF4 assays, and non-heparin anticoagulation. [ABSTRACT FROM AUTHOR]

Summary The diversity of mesenchymal cell types in the lung that influence epithelial homeostasis and regeneration is poorly defined. We used genetic lineage tracing, single-cell RNA sequencing, and organoid culture approaches to show that Lgr5 and Lgr6, well-known markers of stem cells in epithelial tissues, are markers of mesenchymal cells in the adult lung. Lgr6 + cells comprise a subpopulation of smooth muscle cells surrounding airway epithelia and promote airway differentiation of epithelial progenitors via Wnt-Fgf10 cooperation. Genetic ablation of Lgr6 + cells impairs airway injury repair in vivo. Distinct Lgr5 + cells are located in alveolar compartments and are sufficient to promote alveolar differentiation of epithelial progenitors through Wnt activation. Modulating Wnt activity altered differentiation outcomes specified by mesenchymal cells. This identification of region- and lineage-specific crosstalk between epithelium and their neighboring mesenchymal partners provides new understanding of how different cell types are maintained in the adult lung. [ABSTRACT FROM AUTHOR]

Several corrections to the online version of the article "Non-Small-Cell Lung Cancers: A Heterogeneous Set of Diseases," by Zhao Chen and colleagues, published in the journal "Nature Reviews Cancer" is presented.

A correction to the article "A genetic screen identies an LKB1--MARK signalling axis controlling the Hippo--YAP pathway" that was published in the 2013 issue is presented.