GM-CSF: Orchestrating the Pulmonary Response to Infection

This review summarizes the structure and function of the alveolar unit, comprised of alveolar macrophage and epithelial cell types that work in tandem to respond to infection. Granulocyte-macrophage colony-stimulating factor (GM-CSF) helps to maintain the alveolar epithelium and pulmonary immune system under physiological conditions and plays a critical role in restoring homeostasis under pathologic conditions, including infection. Given the emergence of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and global spread of coronavirus disease 2019 (COVID-19), with subsequent acute respiratory distress syndrome, understanding basic lung physiology in infectious diseases is especially warranted. This review summarizes clinical and preclinical data for GM-CSF in respiratory infections, and the rationale for sargramostim (yeast-derived recombinant human [rhu] GM-CSF) as adjunctive treatment for COVID-19 and other pulmonary infectious diseases.

Gene Therapy Potential for Genetic Disorders of Surfactant Dysfunction

Pulmonary surfactant is critically important to prevent atelectasis by lowering the surface tension of the alveolar lining liquid. While respiratory distress syndrome (RDS) is common in premature infants, severe RDS in term and late preterm infants suggests an underlying genetic etiology. Pathogenic variants in the genes encoding key components of pulmonary surfactant including surfactant protein B (SP-B, SFTPB gene), surfactant protein C (SP-C, SFTPC gene), and the ATP-Binding Cassette transporter A3 (ABCA3, ABCA3 gene) result in severe neonatal RDS or childhood interstitial lung disease (chILD). These proteins play essential roles in pulmonary surfactant biogenesis and are expressed in alveolar epithelial type II cells (AEC2), the progenitor cell of the alveolar epithelium. SP-B deficiency most commonly presents in the neonatal period with severe RDS and requires lung transplantation for survival. SFTPC mutations act in an autosomal dominant fashion and more commonly presents with chILD or idiopathic pulmonary fibrosis than neonatal RDS. ABCA3 deficiency often presents as neonatal RDS or chILD. Gene therapy is a promising option to treat monogenic lung diseases. Successes and challenges in developing gene therapies for genetic disorders of surfactant dysfunction include viral vector design and tropism for target cell types. In this review, we explore adeno-associated virus (AAV), lentiviral, and adenoviral (Ad)-based vectors as delivery vehicles. Both gene addition and gene editing strategies are compared to best design treatments for lung diseases resulting from pathogenic variants in the SFTPB, SFTPC, and ABCA3 genes.

Fibroblast growth factor-9 expression in airway epithelial cells amplifies the type I interferon response and alters influenza A virus pathogenesis

Influenza A virus (IAV) preferentially infects conducting airway and alveolar epithelial cells in the lung. The outcome of these infections is impacted by the host response, including the production of various cytokines, chemokines, and growth factors. Fibroblast growth factor-9 (FGF9) is required for lung development, can display antiviral activity in vitro, and is upregulated in asymptomatic patients during early IAV infection. We therefore hypothesized that FGF9 would protect the lungs from respiratory virus infection and evaluated IAV pathogenesis in mice that overexpress FGF9 in club cells in the conducting airway epithelium (FGF9-OE mice). However, we found that FGF9-OE mice were highly susceptible to IAV and Sendai virus infection compared to control mice. FGF9-OE mice displayed elevated and persistent viral loads, increased expression of cytokines and chemokines, and increased numbers of infiltrating immune cells as early as 1 day post-infection (dpi). Gene expression analysis showed an elevated type I interferon (IFN) signature in the conducting airway epithelium and analysis of IAV tropism uncovered a dramatic shift in infection from the conducting airway epithelium to the alveolar epithelium in FGF9-OE lungs. These results demonstrate that FGF9 signaling primes the conducting airway epithelium to rapidly induce a localized, protective IFN and proinflammatory cytokine response during viral infection. Although this response protects the airway epithelial cells from IAV infection, it allows for early and enhanced infection of the alveolar epithelium, ultimately leading to increased morbidity and mortality. Our study illuminates a novel role for FGF9 in regulating respiratory virus infection and pathogenesis.

Epithelial Wntless (Wls) regulates postnatal alveologenesis

Alveologenesis requires the coordinated modulation of the epithelial and mesenchymal compartments to generate mature alveolar saccules for efficient gas exchange. However, the molecular mechanisms underlying the epithelial-mesenchymal interaction during alveologenesis are poorly understood. Here, we report that Wnts produced by epithelial cells are critical for neonatal alveologenesis. Deletion of the Wnt chaperon protein Wntless homolog (Wls) disrupts alveolar formation, resulting in enlarged saccules in Sftpc-Cre/Nkx2.1-Cre; Wlsloxp/loxp mutants. Although commitment of the alveolar epithelium is unaffected, α-SMA+ mesenchymal cells persist in the alveoli accompanied by increased collagen deposition and mutants exhibit exacerbated fibrosis following bleomycin challenge. Notably, α-SMA+ cells include a significant number of endothelial cells resembling endothelial to mesenchymal transition (EndMT) which is also present in Ager-CreER; Wlsloxp/loxp mutants following early postnatal Wls deletion. These findings provide initial evidence that epithelial-derived Wnts are critical for the differentiation of the surrounding mesenchyme during early postnatal alveologenesis.

Clinical and pathomorphological analysis of deaths from COVID-19 in 2020

The aim of the work – to conduct clinical and pathomorphological analysis of deaths from COVID-19 in 2020. Materials and methods. We analyzed 41 case histories and results of pathological-anatomical examination of patients who were died of COVID-19 during 2020. Results. The lethal outcome of COVID-19 disease was recorded at day 22 (16; 27) of the disease. Among the dead, there is a high percentage of men (73.2 %), early old age and middle old age patients (75.6 %) with comorbid pathology (92.7 %). Early lung damage with COVID-19 in the deceased was determined by pronounced interstitial and interstitial-alveolar edema, the presence of erythrocyte stasis in the pulmonary microvessels, blood clots and hypoperfusion leukocyte stasis, as well as the presence of erythrocytes in the alveoli. Bilateral polysegmental subtotal viral pneumonia in 90.2 % of dead patients was characterized by significant edema and thickening of the alveolar walls with their moderate infiltration by lymphocytes, focal peribronchial and perivascular inflammatory polymorphonuclear infiltration, multiple and small exfoliated alveolar epithelium (87.8 %), as well as metaplasia of a few alveolocytes preserved on the luminal surface of the alveoli (82.9 %). Every tenth person who died of COVID-19 had signs of secondary bacterial microflora. In 85.4 % of patients who died on day 22–27 of the disease focal or sublobar pneumofibrosis was diagnosed. In those who died due to COVID-19, multiorgan failure was characterized by focal necrosis of the renal tubular epithelium (73.2 %), focal lymphocytic-leukocyte infiltration (12.2 %) and renal microvascular thrombosis (17.1 %), focal centro-lobular necrosis (90.2 %) and focal lymphocytic-leukocyte infiltration of lobes (7.3 %) of the liver. Thrombotic complications were confirmed in 22.0 % of deceased patients: ischemic cerebral infarction, transmural myocardial infarction, pulmonary embolism, deep vein thrombosis of the lower extremities under the pathology. These thrombotic complications were not diagnosed during life in all patients. The majority of deaths due to COVID-19 had morphological signs of chronic cardiovascular pathology. Ischemic heart disease and hypertension during the life of patients were not diagnosed in all cases. Conclusions. Early lung damage in COVID-19 in the deceased was determined by pronounced interstitial-alveolar edema, blood clots and leukocyte stasis in microvessels, less often – the presence of “hyaline membranes”. In 90.2 % of the dead patients bilateral polysegmental subtotal pneumonia with edema and lymphocytic infiltration of the pulmonary interstitium, inflammatory peribronchial and perivascular focal polymorphonuclear infiltrates, foci of atelectasis and dyscryphaseses was found. In 9.7 % of patients bilateral subtotal viral-bacterial fibrinous-purulent bronchopneumonia developed. In those who died on the 22nd–27th day of the disease focal pneumofibrosis was determined. Pathomorphologically, thrombotic complications, which were not diagnosed in all patients during their lifetime, were confirmed in 22.0 % of deceased patients. Most deaths from COVID-19 had morphological signs of chronic cardiovascular disease.

Evaluation of Pathogenic Potentials of Microbial Contaminants from Naira Notes in Nigeria

The study was done to determine burden of fiat currencies. A total of Six hundred and twenty four pieces of different denominations of naira notes obtained from banks in Enugu metropolis and samples of nose swabs aseptically collected from fifty two note counters from those banks were examined for similar bacterial and fungal contaminants. All sequences were identified using the Basic Local Alignment Search Tool (BLAST) on National Center for Biotechnology Information (NCBI) website. While the fungi amplicons yielded DNA bands of approximately 650 base pair, that of the bacterial isolates were approximately 850 base pair. Proteus mirabilis (NR11449.1) and Escherichia coli (LN831043.1) were identical and selected from the bacterial category while Aspergillus fumigatus (MK910068), Aspergillus flavus (JQ860302) and Aspergillus niger (MK461093) were identical and selected from the fungal category. Rats inoculated orally with Escherichia coli and Proteus mirabilis presented with watery stool and reduction of weight by 16+0.4g after two weeks of commencement of inoculation. They showed reduction in activity and reduced locomotion when compared with the control. There were no physically observable changes in the other test groups. In the hematological investigation, the mean PCV in % were 39±1.0 for the E. coli, 40±0.4 for P. mirabilis, 35±0.2 for A. niger, 40±0.7 for A. fumigatus and 37±0.1 for A .flavus. These varied significantly at p<0.05 with the control which has mean PCV of 45±0.3. The differential leucocyte count showed a marked increase in the % neutrophil (E. coli 73±0.1, P. mirabilis 70±0.1, A. niger 78±1.1, A. fumigatus 59±0.3 and A. flavus 62±1.0) when compared with the control rats with percentage neutrophil of 20±0.2. There was also an increase in the white blood cell count of the test groups when compared with the control. Histopathological study of the lungs of the rats inoculated nasally with Aspergillus niger showed necrosis of the alveolar epithelium. This study has shown that naira notes could be a reservoir of microorganisms of medical importance which in turn could become vectors for the transmission of diseases in the society.

The Link between Circadian Clock Genes and Autophagy in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD), a progressive respiratory disease, is characterized by the alveolar epithelium injury and persistent airway inflammation. It is documented that oscillation and dysregulated expression of circadian clock genes, like Bmal1, Per1, and Per2, involved in COPD pathogenies, including chronic inflammation and imbalanced autophagy level, and targeting the associations of circadian rhythm and autophagy is promising strategies in the management and treatment of COPD. Herein, we reviewed the mechanisms of the circadian clock and the unbalance of the autophagic level in COPD, as well as the link between the two, so as to provide further theoretical bases for the study on the pathogenesis of COPD.

Human Microphysiological Models of Airway and Alveolar Epithelium

Human organ-on-a-chip models are powerful tools for pre-clinical research that can be used to study the mechanisms of disease and evaluate new targets for therapeutic intervention. Lung-on-a-chip models have been one of the most well-characterized designs in this field, and can be altered to evaluate various types of respiratory disease and to assess treatment candidates prior to clinical testing. These systems are capable of overcoming the flaws of conventional 2D cell culture and in vivo animal testing due to their ability to accurately recapitulate the in vivo microenvironment of human tissue with tunable material properties, microfluidic integration, delivery of precise mechanical and biochemical cues, and designs with organ-specific architecture. In this review, we first describe an overview of currently available lung-on-a-chip designs. We then present how recent innovations in human stem cell biology, tissue engineering, and microfabrication can be used to create more predictive human lung-on-a-chip models for studying respiratory disease. Finally, we discuss the current challenges and future directions of lung-on-a-chip designs for in vitro disease modeling with particular focus on immune and multi-organ interactions.

The Role of Hippo/YAP Signaling in Alveolar Repair and Pulmonary Fibrosis

Pulmonary fibrosis is characterized by loss of normal alveoli, accumulation of pathologic activated fibroblasts, and exuberant extracellular matrix deposition that over time can lead to progressive loss of respiratory function and death. This loss of respiratory function is associated with the loss of alveolar type 1 cells (AT1) that play a crucial role in gas exchange and the depletion of the alveolar type 2 cells (AT2) that act as progenitor cells to regenerate the AT1 and AT2 cell populations during repair. Understanding the mechanisms that regulate normal alveolar repair and those associated with pathologic repair is essential to identify potential therapeutic targets to treat or delay progression of fibrotic diseases. The Hippo/YAP developmental signaling pathway has been implicated as a regulator of normal alveolar development and repair. In idiopathic pulmonary fibrosis, aberrant activation of YAP/TAZ has been demonstrated in both the alveolar epithelium and activated fibroblasts associated with increased fibrotic remodeling, and there is emerging interest in this pathway as a target for antifibrotic therapies. In this review, we summarize current evidence as to the role of the Hippo-YAP/TAZ pathway in alveolar development, homeostasis, and repair, and highlight key questions that must be resolved to determine effective strategies to modulate YAP/TAZ signaling to prevent progressive pulmonary fibrosis and enhance adaptive alveolar repair.