JAK/STAT signaling in rheumatoid arthritis leukocytes is uncoupled from serum cytokines in a subset of patients.

OBJECTIVE: Rheumatoid Arthritis (RA) is a systemic autoimmune disease involving pro-inflammatory cytokines that can be therapeutically targeted by antibodies or kinase inhibitors. Nevertheless, these drugs fail in a subset of patients independent of the abundance of the targeted cytokines. We aim to explore the cellular basis of this phenomenon by analyzing the relation of cytokine abundance and activation of downstream signaling pathways in RA. METHODS: The study included 62 RA patients and 9 healthy controls (HC). Phosphorylation of STAT 1-6 in various immune cell subsets was determined ex vivo using a novel robust flow cytometry-based protocol. Serum concentrations of IL-6, IL-10, IL-12p70, IL-17 A, interferon gamma, and TNFα in the same samples were measured using highly sensitive single molecule array (SIMOA). RESULTS: We found an increase in circulating cytokines in RA patients, while STAT activity was lower in RA patients compared to HC. Based on STAT activity we determined three endotypes in active RA patients (cDAI>10, n = 28): 1) those with active STAT5a/b signaling in T cells (n = 7/28), 2) those with a low STAT activity in all assessed cell types (n = 14/28), and 3) those with active STAT1 and STAT3 signaling mainly in myeloid cells (n = 7/28). Integrating intracellular STAT activation and cytokine analysis revealed diminished JAK/STAT signaling in a subset of patients (n = 8/20) despite elevated serum cytokine concentrations. CONCLUSION: Diminished JAK/STAT signaling in active RA may partly explain unresponsiveness to therapy targeting cytokine signaling. Analysis of JAK/STAT phosphorylation may identify patients at risk for non-response to these therapies.

Definitions of and Instruments for Disease Activity, Remission, and Relapse in Polymyalgia Rheumatica: A Systematic Literature Review.

OBJECTIVE: To perform a systematic literature review on definitions and instruments used to measure remission, relapse, and disease activity in polymyalgia rheumatica (PMR), to inform an OMERACT project to endorse instruments for these outcomes. METHODS: A search of Pubmed/MEDLINE, EMBASE, CINAHL, Cochrane, and Epistemonikos was performed May 2021 and updated August 2023. Qualitative and quantitative studies published in English were included if they recruited people with isolated PMR regardless of treatment. Study selection and data extraction was performed independently by two investigators and disagreement was resolved through discussion. Data extracted encompassed definitions of disease activity, remission and relapse, and details regarding the instruments used to measure these outcomes. RESULTS: From the 5,718 records, we included 26 articles on disease activity, 36 on remission, and 53 on relapse; 64 studies were observational and 15interventional, and none used qualitative methods. Some heterogeneity was found regarding definitions and instruments encompassing the domains pain, stiffness, fatigue, laboratory markers (mainly acute phase reactants), and patient and physician global assessment of disease activity. However, instruments for clinical signs were often poorly described. Whilst measurement properties of the polymyalgia rheumatica activity score (PMR-AS) have been assessed, data to support its use for measurement of remission and relapse is limited. CONCLUSION: Remission, relapse, and disease activity have been defined heterogeneously in clinical studies. Instruments to measure these disease states still need to be validated. Qualitative research is needed to better understand the concepts of remission and relapse in PMR. REVIEW REGISTRATION: PROSPERO identification: CRD42021255925.

Cranial involvement in giant cell arteritis.

Since its first clinical description in 1890, extensive research has advanced our understanding of giant cell arteritis, leading to improvements in both diagnosis and management for affected patients. Imaging studies have shown that the disease frequently extends beyond the typical cranial arteries, also affecting large vessels such as the aorta and its proximal branches. Meanwhile, advances in comprehending the underlying pathophysiology of giant cell arteritis have given rise to numerous potential therapeutic agents, which aim to minimise the need for glucocorticoid treatment and prevent flares. Classification criteria for giant cell arteritis, as well as recommendations for management, imaging, and treat-to-target have been developed or updated in the last 5 years, and current research encompasses a broad spectrum covering basic, translational, and clinical research. In this Series paper, we aim to discuss the current understanding of giant cell arteritis with cranial manifestations, describe the clinical approach to this condition, and explore future directions in research and patient care.