Background: Growing evidence from studies elsewhere have illustrated that microRNAs (miRNAs) play important roles in polymyositis and dermatomyositis (PM/DM). However, little has been reported on their relationship with regenerating islet-derived protein 3-alpha (REG3A) as well as their associative roles in macrophage migration. Therefore, this study sought to establish the association between miR-146a and REG3A as well as investigate their functional roles in macrophage migration and PM/DM pathogenesis.

Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from PM/DM patients and healthy controls through density centrifugation. Macrophages were obtained from monocytes purified from PBMCs via differentiation before their transfection with miRNA or plasmids to investigate cell migration with transwell assay. An experimental autoimmune myositis murine model was used to investigate PM/DM. Real-time PCR and Western blot analysis were conducted to determine the expression levels of miR-146a, interferon gamma (IFN-γ), interleukin (IL)-17A, and REG3A.

Results: The messenger RNA (mRNA) expression level of miR-146a markedly decreased, while the mRNA level of REG3A, IFN-γ, and IL-17A expression increased substantially in PBMCs from PM/DM patients compared with the healthy controls. The levels of IFN-γ and IL-17A in serum from PM/DM patients was much higher than the healthy controls. Immunohistochemistry analysis showed that REG3A expression increased in muscle tissues from patients. Consistent with clinical data, the mRNA expression level of miR-146a also decreased, whereas the mRNA and protein level of REG3A, IFN-γ, and IL-17A significantly increased in the muscle tissues of experimental autoimmune myositis mice. Moreover, miR-146a inhibited monocyte-derived macrophage migration, and REG3A promoted macrophage migration. In addition, IL-17A induced REG3A expression, while miR146a inhibited expression of REG3A in monocyte-derived macrophages from the PBMCs of the healthy donors. Notably, inhibition of macrophage migration by miR-146a was via the reduction in REG3A expression.

Conclusions: Reduced miR-146a expression in PM/DM leads to increased REG3A expression that increases inflammatory macrophage migration, which may be a possible underlying mechanism of DM/PM pathogenesis.

背景：来自其他地方的越来越多的证据表明，microRNA（miRNA）在多发性肌炎和皮肌炎（PM / DM）中起重要作用。然而，关于它们与再生胰岛衍生蛋白3-alpha（REG3A）的关系以及它们在巨噬细胞迁移中的相关作用的报道很少。因此，本研究试图建立miR-146a和REG3A之间的联系，并研究它们在巨噬细胞迁移和PM / DM发病机理中的功能。

方法：通过密度离心从PM / DM患者和健康对照中分离出外周血单核细胞（PBMC）。巨噬细胞是从PBMC中纯化出来的单核细胞通过分化获得的，然后再用miRNA或质粒转染，以通过Transwell分析研究细胞迁移。实验性自身免疫性肌炎鼠模型用于研究PM / DM。进行实时PCR和蛋白质印迹分析以确定miR-146a，干扰素γ（IFN-γ），白介素（IL）-17A和REG3A的表达水平。

结果：与健康对照组相比，PM / DM患者的PBMC中miR-146a的信使RNA（mRNA）表达水平显着降低，而REG3A，IFN-γ和IL-17A的mRNA表达则显着增加。PM / DM患者血清中的IFN-γ和IL-17A水平远高于健康对照组。免疫组织化学分析表明，患者肌肉组织中的REG3A表达增加。与临床数据一致，miR-146a的mRNA表达水平也降低，而REG3A，IFN-γ和IL-17A的mRNA和蛋白水平在实验性自身免疫性肌炎小鼠的肌肉组织中显着增加。此外，miR-146a抑制了单核细胞衍生的巨噬细胞迁移，而REG3A则促进了巨噬细胞迁移。此外，IL-17A诱导REG3A表达，而miR146a抑制健康捐献者PBMC单核细胞衍生巨噬细胞中REG3A的表达。值得注意的是，miR-146a对巨噬细胞迁移的抑制作用是通过减少REG3A表达来实现的。

结论： PM / DM中miR-146a表达的降低导致REG3A表达增加，从而增加了炎性巨噬细胞的迁移，这可能是DM / PM发病机制的潜在潜在机制。