Allergic Asthma Responses Are Dependent on Macrophage Ontogeny.

The ontogenetic composition of tissue-resident macrophages following injury, environmental exposure, or experimental depletion can be altered upon re-establishment of homeostasis. However, the impact of altered resident macrophage ontogenetic milieu on subsequent immune responses is poorly understood. Hence, we assessed the effect of macrophage ontogeny alteration following return to homeostasis on subsequent allergic airway responses to house dust mites (HDM). Using lineage tracing, we confirmed alveolar and interstitial macrophage ontogeny and their replacement by bone marrow-derived macrophages following LPS exposure. This alteration in macrophage ontogenetic milieu reduced allergic airway responses to HDM challenge. In addition, we defined a distinct population of resident-derived interstitial macrophages expressing allergic airway disease genes, located adjacent to terminal bronchi, and reduced by prior LPS exposure. These findings support that the ontogenetic milieu of pulmonary macrophages is a central factor in allergic airway responses and has implications for how prior environmental exposures impact subsequent immune responses and the development of allergy.

Single-Cell Analysis Reveals Distinct Immune and Smooth Muscle Cell Populations that Contribute to Chronic Thromboembolic Pulmonary Hypertension.

Rationale: Chronic thromboembolic pulmonary hypertension (CTEPH) is a sequela of acute pulmonary embolism (PE) in which the PE remodels into a chronic scar in the pulmonary arteries. This results in vascular obstruction, pulmonary microvasculopathy, and pulmonary hypertension. Objectives: Our current understanding of CTEPH pathobiology is primarily derived from cell-based studies limited by the use of specific cell markers or phenotypic modulation in cell culture. Therefore, our main objective was to identify the multiple cell types that constitute CTEPH thrombusy and to study their dysfunction. Methods: Here we used single-cell RNA sequencing of tissue removed at the time of pulmonary endarterectomy surgery from five patients to identify the multiple cell types. Using in vitro assays, we analyzed differences in phenotype between CTEPH thrombus and healthy pulmonary vascular cells. We studied potential therapeutic targets in cells isolated from CTEPH thrombus. Measurements and Main Results: Single-cell RNA sequencing identified multiple cell types, including macrophages, T cells, and smooth muscle cells (SMCs), that constitute CTEPH thrombus. Notably, multiple macrophage subclusters were identified but broadly split into two categories, with the larger group characterized by an upregulation of inflammatory signaling predicted to promote pulmonary vascular remodeling. CD4+ and CD8+ T cells were identified and likely contribute to chronic inflammation in CTEPH. SMCs were a heterogeneous population, with a cluster of myofibroblasts that express markers of fibrosis and are predicted to arise from other SMC clusters based on pseudotime analysis. Additionally, cultured endothelial, smooth muscle, and myofibroblast cells isolated from CTEPH fibrothrombotic material have distinct phenotypes from control cells with regard to angiogenic potential and rates of proliferation and apoptosis. Last, our analysis identified PAR1 (protease-activated receptor 1) as a potential therapeutic target that links thrombosis to chronic PE in CTEPH, with PAR1 inhibition decreasing SMC and myofibroblast proliferation and migration. Conclusions: These findings suggest a model for CTEPH similar to atherosclerosis, with chronic inflammation promoted by macrophages and T cells driving vascular remodeling through SMC modulation, and suggest new approaches for pharmacologically targeting this disease.

Defining genetic diversity of rhesus macaque Fcγ receptors with long-read RNA sequencing.

Fcγ receptors (FcγRs) are membrane-bound glycoproteins that bind to the fragment crystallizable (Fc) constant regions of IgG antibodies. Interactions between IgG immune complexes and FcγRs can initiate signal transduction that mediates important components of the immune response including activation of immune cells for clearance of opsonized pathogens or infected host cells. In humans, many studies have identified associations between FcγR gene polymorphisms and risk of infection, or progression of disease, suggesting a gene-level impact on FcγR-dependent immune responses. Rhesus macaques are an important translational model for most human health interventions, yet little is known about the breadth of rhesus macaque FcγR genetic diversity. This lack of knowledge prevents evaluation of the impact of FcγR polymorphisms on outcomes of preclinical studies performed in rhesus macaques. In this study we used long-read RNA sequencing to define the genetic diversity of FcγRs in 206 Indian-origin Rhesus macaques, Macaca mulatta. We describe the frequency of single nucleotide polymorphisms, insertions, deletions, frame-shift mutations, and isoforms. We also index the identified diversity using predicted and known rhesus macaque FcγR and Fc-FcγR structures. Future studies that define the functional significance of this genetic diversity will facilitate a better understanding of the correlation between human and macaque FcγR biology that is needed for effective translation of studies with antibody-mediated outcomes performed in rhesus macaques.

The skin transcriptome in hidradenitis suppurativa uncovers an antimicrobial and sweat gland gene signature which has distinct overlap with wounded skin.

Hidradenitis suppurativa (HS) is a debilitating chronic inflammatory skin disease resulting in non-healing wounds affecting body areas of high hair follicle and sweat gland density. The pathogenesis of HS is not well understood but appears to involve dysbiosis-driven aberrant activation of the innate immune system leading to excessive inflammation. Marked dysregulation of antimicrobial peptides and proteins (AMPs) in HS is observed, which may contribute to this sustained inflammation. Here, we analyzed HS skin transcriptomes from previously published studies and integrated these findings through a comparative analysis with a published wound healing data set and with immunofluorescence and qPCR analysis from new HS patient samples. Among the top differently expressed genes between lesional and non-lesional HS skin were members of the S100 family as well as dermcidin, the latter known as a sweat gland-associated AMP and one of the most downregulated genes in HS lesions. Interestingly, many genes associated with sweat gland function, such as secretoglobins and aquaporin 5, were decreased in HS lesional skin and we discovered that these genes demonstrated opposite expression profiles in healing skin. Conversely, HS lesional and wounded skin shared a common gene signature including genes encoding for S100 proteins, defensins, and genes encoding antiviral proteins. Overall, our results suggest that the pathogenesis of HS may be driven by changes in AMP expression and altered sweat gland function, and may share a similar pathology with chronic wounds.