Biology subjects

Summers, C.

Publications and source records attributed to Summers, C..

4 recordsLinked to original sources

bioRxiv2026

Circulating pre-osteoclasts are primed for osteoclast fate and synovial tissue homing in psoriatic arthritis.

Psoriatic arthritis (PsA) is a complex immune-mediated inflammatory disease with heterogenous clinical features. Osteoclasts have a unique ability to destroy bone, playing key roles in both healthy bone turnover and pathological erosions in arthritis. They are believed to arise from monocytic precursors migrating to inflamed synovial tissue, though the identity of this precursor in humans has remained elusive. Here, we sought to determine whether monocytes home to psoriatic joints and their phenotype. We find that monocytes are recruited to inflamed joints in PsA but not uninvolved or healthy joints, and identify a pre-osteoclast (preOC) cell state derived from classical monocytes. PreOC are transcriptionally distinct from classical monocytes, are enriched for NFACT1, the master regulator of osteoclastogenesis, and form multinucleated osteoclasts in vitro without exogenous RANKL. They are expanded in the circulation of donors with active treatment naive PsA, compared to both healthy controls and those with cutaneous psoriasis only. Finally, using a customised spatial transcriptomics workflow, we identified these cells within human synovial tissue, and radiolabelling confirmed their recruitment from the circulation. These findings highlight the role of systemic immune priming in macrophage pathophysiology.

immunology↗

bioRxiv2023

Efficient methods for target gene manipulation in haematopoietic stem cell derived human neutrophils.

Neutrophils are the most abundant leukocyte in humans and the principal effectors of the innate immue response. Genetic modification of human neutrophils is challenging due to their short lifespan and tendency to activate in response to even minor perturbation. However, genetic manipulation of haematopoietic progenitor cells and subsequent directed differentation into neutrophils represents a potential avenue to study the contributions of individual genes and pathways to human neutrophil function. Here we present a method of directed granulocytic CD34+ progenitor differentiation into neutrophils capable of key functions such as priming and neutrophil extracellular trap (NET) formation. We further show that differentiating progenitors can be efficiently and stably modified by lentiviral gene delivery and Cas9-gRNP nucleofection to produce potent and activation-free gene knockdown in mature neutrophils, thereby providing new tools for understanding the contribution of neutrophils to health and disease. Using this model we have shown that, contrary to previous reports, CD11b is not required for phagocytosis of serum-opsonised bacterial particles.

cell biology↗

bioRxiv2020

Circulating BMP9 protects the pulmonary endothelium during inflammation-induced lung injury in mice

RationalePulmonary endothelial permeability contributes to the high-permeability pulmonary edema that characterizes acute respiratory distress syndrome (ARDS), which carries a high mortality. Circulating bone morphogeneic protein 9 (BMP9) is emerging as an important regulator of pulmonary vascular homeostasis. ObjectiveTo determine whether endogenous BMP9 plays a role in preserving pulmonary endothelial integrity, and whether loss of endogenous BMP9 occurs during lipopolysacharride (LPS)-induced lung inflammation and permeability. MethodsA BMP9-neutralizing antibody was administrated to healthy adult mice and lung vasculature was examined. Potential mechanisms were delineated by transcript analysis in human primary lung endothelial cells. Impact of BMP9 was evaluated in a murine acute lung injury model induced by inhaled LPS. Levels of BMP9 were measured in plasma from patients with sepsis and endotoxemic mice. Main ResultsSubacute neutralization of endogenous BMP9 in mice resulted in increased lung vascular permeability, interstitial edema and neutrophil extravasation. In lung endothelial cells, BMP9 regulated a programme of gene expression and pathways controlling vascular permeability and cell membrane integrity. Augmentation of BMP9 signalling in mice with exogenous BMP9 prevented inhaled LPS-caused lung injury and edema. In endotoxemic mice, endogenous BMP9 levels were markedly reduced, due to a transient reduction in hepatic BMP9 mRNA expression and increased elastase activity in plasma. In human sepsis patients, circulating levels of BMP9 were also markedly reduced. ConclusionsEndogenous circulating BMP9 is a pulmonary endothelial protective factor, down-regulated during inflammation. Supplementation with exogenous BMP9 offers a potential therapy to prevent increased pulmonary endothelial permeability in the setting of lung injury. Short summaryO_ST_ABSScientific Knowledge on the SubjectC_ST_ABSIncreased pulmonary endothelial permeability is a major factor in the development of acute respiratory distress syndrome (ARDS). Evidence is emerging that circulating BMP9, secreted from the liver, might protect the pulmonary endothelium from injury. For example, loss of BMP9 levels or signalling receptor contributes to the development of pulmonary arterial hypertension. The role of endogenous BMP9 in endothelial permeability remains unclear. What This Study Adds to the FieldHere we show that subacute neutralization of endogenous BMP9 leads to lung vascular injury, including enhanced permeability and neutrophil extravasation. BMP9 levels were markedly reduced in the setting of inflammation in mice and humans. Conversely, exogenous supplementation of BMP9 protected the lung from LPS-induced injury. This study suggests that exogenous BMP9 could offer a novel approach to prevent increased pulmonary endothelial permeability in the setting of lung injury and ARDS.

physiology↗

bioRxiv2020

Complement C5a impairs phagosomal maturation in the neutrophil through phosphoproteomic remodelling.

Critical illness is accompanied by the release of large amounts of the anaphylotoxin, C5a. C5a suppresses antimicrobial functions of neutrophils which is associated with adverse outcomes. The signalling pathways that mediate C5a-induced neutrophil dysfunction are incompletely understood. Healthy donor neutrophils exposed to purified C5a demonstrated a prolonged defect (7 hours) in phagocytosis of Staphylococcus aureus. Phosphoproteomic profiling of 2712 phosphoproteins identified persistent C5a signalling and selective impairment of phagosomal protein phosphorylation on exposure to S. aureus. Notable proteins included early endosomal marker ZFYVE16 and V-ATPase proton channel component ATPV1G1. A novel assay of phagosomal acidification demonstrated C5a-induced impairment of phagosomal acidification which was recapitulated in neutrophils from critically ill patients. Examination of the C5a-impaired protein phosphorylation indicated a role for the phosphatidylinositol 3-kinase VPS34 in phagosomal maturation. Inhibition of VPS34 impaired neutrophil phagosomal acidification and killing of S. aureus. This study provides a phosphoproteomic assessment of human neutrophil signalling in response to S. aureus and its disruption by C5a, identifying a defect in phagosomal maturation and new mechanisms of immune failure in critical illness.

immunology↗