Faculty Bibliography

OBJECTIVES/OBJECTIVE:, the classical risk factor for the disease. The mechanistic implications and biological consequences of this epistatic relationship are unknown. Here, we aimed to determine its biological relevance and functional impact. METHODS:LCL, analysed the HLA class I-bound peptidome for peptide length differences and assessed immunogenicity of genome-edited cells in CD8 T cell co-culture systems. RESULTS:KO cells showed peptidomes with longer peptides above 9mer and significant differences in their ability to stimulate alloreactive CD8 T cells compared with wild-type control cells. CONCLUSIONS:at the cellular level and point to an HLA-B51-restricted process. Our findings suggest that variant ERAP1-Hap10 partakes in BD pathogenesis by generating HLA-B51-restricted peptides, causing a change in immunodominance of the ensuing CD8 T cell response.

Gpr125 is an orphan G-protein coupled receptor, with homology to cell adhesion and axonal guidance factors, that is implicated in planar polarity and control of cell movements. By lineage tracing we demonstrate that Gpr125 is a highly specific marker of bipotent mammary stem cells in the embryo and of multiple long-lived unipotent basal mammary progenitors in perinatal and postnatal glands. Nipple-proximal Gpr125+ cells express a transcriptomic profile indicative of chemo-repulsion and cell movement, whereas Gpr125+ cells concentrated at invasive ductal tips display a hybrid epithelial-mesenchymal phenotype and are equipped to bind chemokine and growth factors and secrete a promigratory matrix. Gpr125 progenitors acquire bipotency in the context of transplantation and cancer and are greatly expanded and massed at the pushing margins of short latency MMTV-Wnt1 tumors. High Gpr125 expression identifies patients with particularly poor outcome within the basal breast cancer subtype highlighting its potential utility as a factor to stratify risk.

The severe acute respiratory syndrome coronavirus-2 emerged as a serious human pathogen in late 2019, causing the disease coronavirus disease 2019 (COVID-19). The most common clinical presentation of severe COVID-19 is acute respiratory failure consistent with the acute respiratory distress syndrome. Airway, lung parenchymal, pulmonary vascular, and respiratory neuromuscular disorders all feature in COVID-19. This article reviews what is known about the effects of severe acute respiratory syndrome coronavirus-2 infection on different parts of the respiratory system, clues to understanding the underlying biology of respiratory disease, and highlights current and future translation and clinical research questions.

Pulmonary disease increases the risk of developing abdominal aortic aneurysms (AAA). However, the mechanism underlying the pathological dialogue between the lungs and aorta is undefined. Here, we find that inflicting acute lung injury (ALI) to mice doubles their incidence of AAA and accelerates macrophage-driven proteolytic damage of the aortic wall. ALI-induced HMGB1 leaks and is captured by arterial macrophages thereby altering their mitochondrial metabolism through RIPK3. RIPK3 promotes mitochondrial fission leading to elevated oxidative stress via DRP1. This triggers MMP12 to lyse arterial matrix, thereby stimulating AAA. Administration of recombinant HMGB1 to WT, but not Ripk3^-/- mice, recapitulates ALI-induced proteolytic collapse of arterial architecture. Deletion of RIPK3 in myeloid cells, DRP1 or MMP12 suppression in ALI-inflicted mice repress arterial stress and brake MMP12 release by transmural macrophages thereby maintaining a strengthened arterial framework refractory to AAA. Our results establish an inter-organ circuitry that alerts arterial macrophages to regulate vascular remodeling.

Progressive fibrosing interstitial lung disease (PF-ILD) has been redefined as a new clinical syndrome that shares similar genetics, pathophysiology, and natural history to idiopathic pulmonary fibrosis (IPF). IPF is the most common form of idiopathic interstitial pneumonias, which is progressive in nature and is associated with significant mortality. Therapies targeting an inflammatory and/or immune response have not been consistently effective or well tolerated in patients with IPF. The two antifibrotic drugs approved for IPF treatment, nintedanib and pirfenidone, have been shown to reduce lung function decline in PF-ILD. Novel uses of antifibrotic therapy are emerging due to a paucity of evidence-based treatments for multiple ILD subtypes. In this review, we describe the current body of knowledge on antifibrotic therapy and immunomodulators in PF-ILD, drawing from experience in IPF where appropriate.

Sonic Hedgehog (SHH) signaling, a developmental pathway promoting lung mesenchymal expansion and differentiation during embryogenesis, has been increasingly recognized as a profibrotic factor in mature lung, where it might contribute to the pathogenesis of lung fibrosis. Pathway inhibition at the level of the downstream Gli transcription factors Gli1 and Gli2 (by GANT61) ameliorates lung fibrosis in the bleomycin model, whereas inhibition proximally at the level of HH ligand (by anti Hh antibody 5E1) or Smo (by GDC-0449) of the canonical pathway does not, implicating Gli1 and/or Gli2 as a key target. The fact that both the Gli1-labelled cell lineage and Gli1 expressing cells expand during fibrosis formation and contribute significantly to the pool of myofibroblasts in the fibrosis scars suggests a fibrogenic role for Gli1. Therefore to further dissect the roles of Gli1 and Gli2 in lung fibrosis we evaluated Gli1 KO and control mice in the bleomycin model. Monitoring of Gli1^+/+ (n = 12), Gli1^lZ/+ (n = 37) and Gli1^lZ/lZ (n = 18) mice did not reveal differences in weight loss or survival. Lung evaluation at the 21-day endpoint did not show differences in lung fibrosis formation (as judged by morphology and trichrome staining), Ashcroft score, lung collagen content, lung weight, BAL protein content or BAL cell differential count. Our data suggest that Gli1 is not required for bleomycin-induced lung fibrosis.

Sonic Hedgehog (Shh) signaling regulates mesenchymal proliferation and differentiation during embryonic lung development. In the adult lung, Shh signaling maintains mesenchymal quiescence and is dysregulated in diseases such as IPF and COPD. Our previous data implicated a role for Shh in postnatal lung development. Here we report a detailed analysis of Shh signaling during murine postnatal lung development. We show that Shh pathway expression and activity during alveolarization (P0-P14) are distinct from those during maturation (P14-P24). This biphasic pattern is paralleled by the transient presence of Gli1+;alpha-smooth muscle actin (aSMA)+ myofibroblasts in the growing alveolar septal tips. Carefully-timed inhibition of Hedgehog (Hh) signaling during alveolarization defined mechanisms by which Shh influences the mesenchymal compartment. First, interruption of Hh signaling at earlier time points results in increased lung compliance and wall structure defects of increasing severity, ranging from moderately enlarged alveolar airspaces to markedly enlarged airspaces and fewer secondary septa. Second, Shh signaling is required for myofibroblast differentiation: Hh inhibition during early alveolarization almost completely eliminates Gli1+;aSMA+ cells at the septal tips, and Gli1-lineage tracing revealed that Gli1+ cells do not undergo apoptosis after Hh inhibition, but remain in the alveolar septa and are unable to express aSMA. Third, Shh signaling is vital to mesenchymal proliferation during alveolarization, as Hh inhibition decreased proliferation of Gli1+ cells and their progeny. Our study establishes Shh as a new alveolarization promoting factor that might be affected in perinatal lung diseases that are associated with impaired alveolarization.

Over the past two decades, the secreted protein sonic hedgehog (SHH) has emerged as a critical morphogen during embryonic lung development, regulating the interaction between epithelial and mesenchymal cell populations in both the airway and alveolar compartments. There is increasing evidence that the SHH pathway is active in adult lung diseases such as pulmonary fibrosis, asthma, chronic obstructive pulmonary disease (COPD) and lung cancer, which raises two questions: (1) what role does SHH signaling play in these diseases? (2) Is it a primary driver of the disease, or a response (perhaps beneficial) to the primary disturbance? In this review we aim to fill the gap between the well-studied period of embryonic lung development and the adult diseased lung by reviewing the HH pathway during the postnatal period, and in adult uninjured and injured lungs. We elucidate the similarities and differences in the epithelial-mesenchymal interplay during the fibrosis response to injury in lung compared to other organs, and present a critical appraisal of tools and agents available to evaluate HH signaling.

Sonic Hedgehog (Shh) signals from epithelium to mesenchyme during embryonic lung development, but the roles of Hedgehog (Hh) signaling in postnatal lung development and adult lung are not known. Using Gli1nlacZ reporter mice to identify cells with active Hh signaling, we found that Gli1nlacZ-positive mesenchymal cells are densely and diffusely present up to 2 weeks after birth and decline in number thereafter. In adult mice, Gli1nlacZ-positive cells are present around large airways and vessels and are sparse in alveolar septa. Hh-stimulated cells are mostly fibroblasts; only 10% of Gli1nlacZ-positive cells are smooth muscle cells, and most smooth muscle cells do not have activation of Hh signaling. After bleomycin injury there are abundant Gli1nlacZ-positive mesenchymal cells in fibrotic lesions and increased numbers of Gli1nlacZ-positive cells in preserved alveolar septa. Inhibition of Hh signaling with an antibody against all Hedgehog isoforms does not reduce bleomycin-induced fibrosis, but adenovirus-mediated over-expression of Shh increases collagen production in this model. Inhibition of Hh signaling during early postnatal lung development causes airspace enlargement without diminished alveolar septation. Reduction of Hh signaling in the later stages of postnatal lung development may be required for normal thinning and maturation of alveolar septa.