Introduction: The aetiopathogenesis of juvenile dermatomyositis (JDM) remains poorly understood. In particular the contribution of monocytes or macrophages, which are frequently observed to be an infiltrate within muscle tissue very early in the disease process, is unknown. We hypothesised that these cells secrete the pro-inflammatory myeloid related protein (MRP) 8/14 which may then contribute to muscle pathology in JDM.

Methods: In this study of 56 JDM patients, serum MRP8/14 levels were compared with clinical measures of disease activity. Muscle biopsies taken early in disease were assessed by immunohistochemistry to determine the frequency and identity of MRP-expressing cells. The effects of MRP stimulation and endoplasmic reticulum (ER) stress on muscle were tested in vitro. Serum or supernatant levels of cytokines were analyzed by multiplex immunoassay.

Results: Serum MRP8/14 correlated with physician's global assessment of disease activity in JDM (R = 0.65, p = 0.0003) and muscle strength/endurance, childhood myositis assessment score (CMAS, R = -0.55, p = 0.004). MRP8/14 was widely expressed by CD68+ macrophages in JDM muscle tissue. When cultured with human myoblasts, MRP8 led to the secretion of MCP-1 and IL-6, which was enhanced by ER stress. Both inflammatory mediators were detected in significantly higher levels in the serum of JDM patients compared to healthy controls.

Conclusions: This study is the first to identify serum MRP8/14 as a potential biomarker for disease activity in JDM. We propose that tissue infiltrating macrophages secreting MRP8/14 may contribute to myositis, by driving the local production of cytokines directly from muscle.

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乐备实是国内专注于提供高质量蛋白检测以及组学分析服务的实验服务专家，自2018年成立以来，乐备实不断寻求突破，公司的服务技术平台已扩展到单细胞测序、空间多组学、流式检测、超敏电化学发光、Luminex多因子检测、抗体芯片、PCR Array、ELISA、Elispot、PLA蛋白互作、多色免疫组化、DSP空间多组学等30多个，建立起了一套涵盖基因、蛋白、细胞以及组织水平实验的完整检测体系。

 
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