Ageing and interferon gamma response drive the phenotype of neutrophils in the inflamed joint

Abstract

ObjectiveNeutrophils are typically the most abundant leucocyte in arthritic synovial fluid. We sought to understand changes that occur in neutrophils as they migrate from blood to joint.MethodsWe performed RNA sequencing of neutrophils from healthy human blood, arthritic blood and arthritic synovial fluid, comparing transcriptional signatures with those from murine K/BxN serum transfer arthritis. We employed mass cytometry to quantify protein expression and sought to reproduce the synovial fluid phenotype ex vivo in cultured healthy blood neutrophils.ResultsBlood neutrophils from healthy donors and patients with active arthritis showed largely similar transcriptional signatures. By contrast, synovial fluid neutrophils exhibited more than 1600 differentially expressed genes. Gene signatures identified a prominent response to interferon gamma (IFN-γ), as well as to tumour necrosis factor, interleukin-6 and hypoxia, in both humans and mice. Mass cytometry confirmed that healthy and arthritic donor blood neutrophils are largely indistinguishable but revealed a range of neutrophil phenotypes in synovial fluid defined by downregulation of CXCR1 and upregulation of FcγRI, HLA-DR, PD-L1, ICAM-1 and CXCR4. Reproduction of key elements of this signature in cultured blood neutrophils required both IFN-γ and prolonged culture.ConclusionsCirculating neutrophils from patients with arthritis resemble those from healthy controls, but joint fluid cells exhibit a network of changes, conserved across species, that implicate IFN-γ response and ageing as complementary drivers of the synovial fluid neutrophil phenotype.

Human and murine neutrophils share core transcriptional programs in both homeostatic and inflamed contexts

“…In murine neutrophils, the combination of GM-CSF and LPS led to a stronger increase in expression of CD14, CD69, IL-4R and CD40 compared to GM-CSF and IFN-γ. The reverse was true for PD-L1, which is driven substantially by IFN-γ signaling (8). In mice, IFN-γ stimulation reduced CD69 expression, while LPS increased it.…”

“…For example, human neutrophils are highly abundant in defensins, yet their murine orthologs are expressed in gut epithelial cells, not in neutrophils. Furthermore, neutrophils display high phenotypic and functional heterogeneity as a function of organ, maturation and inflammatory condition (6)(7)(8)(9), but whether a core inflammation program consisting of genes that become induced across a range of inflammatory conditions exists, is not known. It is thus unclear how similarities and differences between human and mouse transcriptomes should be interpreted, particularly in the context of different inflammatory conditions.…”

Neutrophil extracellular traps in systemic autoimmune and autoinflammatory diseases

“…1 ). In addition, neutrophil migration into inflamed tissues, such as the inflamed joint in patients with rheumatoid arthritis, is considered a strong driver of changes in gene and protein expression, creating further complexity in terms of neutrophil heterogeneity between blood and tissues 35 .…”

T lymphocytes-related cell network in the pathogenesis of juvenile idiopathic arthritis: a key point for personalized treatment

“…Their activity is strictly influenced by T cells, indeed it has been demonstrated that while circulating neutrophils do not significantly differ from healthy donors, those infiltrating the SF display an IFN-γ signature at transcriptomic level. SF neutrophils have also phenotypic abnormalities, such as CXCR1 downregulation and upregulation of CD11c, PD-L1, ICAM-1, HLA-DR [32 ▪ ,18]. An elevated percentage of CXCR4 + neutrophils was observed in SF, allowing these cells to respond to CXCL12/SDF-1 and to be retained in the inflamed tissue [32 ▪ ,18].…”

“…SF neutrophils have also phenotypic abnormalities, such as CXCR1 downregulation and upregulation of CD11c, PD-L1, ICAM-1, HLA-DR [32 ▪ ,18]. An elevated percentage of CXCR4 + neutrophils was observed in SF, allowing these cells to respond to CXCL12/SDF-1 and to be retained in the inflamed tissue [32 ▪ ,18]. Finally, SF neutrophils display an aged phenotype (CD16high, CD62low), differently from those in the blood that instead are primarily CD16high CD62Lhigh [33].…”