Dermatomyositis (DM) is a systemic autoimmune disease. It’s known that the number of regulatory T (Treg) cells was decreased in DM. Besides, Treg cells were increased after treatment in DM patients. Forkhead box P3 (Foxp3) is specifically expressed in Treg cells and Runt-related transcription factor (RUNX3) could regulate Foxp3 transcription. And our previous experiment showed that Homeobox D gene cluster antisense growth-associated long noncoding RNA (HAGLR) was up-regulated in DM patients. Here, we aimed to explore whether HAGLR regulated the differentiation of Treg cells through RUNX3-mediated transcription of Foxp3, thus affecting the progression of DM. The levels of HAGLR, Foxp3, and RUNX3 were examined by quantitative real-time PCR. The protein levels of Foxp3 and RUNX3 were examined by western blot. The proportions of Treg cells in CD4⁺ T cells were detected by flow cytometry. Hematoxylin and eosin staining was conducted to observe the histopathological changes of the muscle. RNA pull-down assay was performed to detect the interaction between HAGLR and RUNX3. A dual-luciferase reporter gene assay was conducted to examine the effect of HAGLR on the transcriptional regulation of Foxp3 by RUNX3. HAGLR was up-regulated and Foxp3 was down-regulated in DM patients. Besides, RUNX3 protein levels were decreased in DM patients, while its mRNA levels did not change significantly. The proportion of Treg cells was down-regulated in DM patients. In addition, interference with HAGLR could increase the levels of Foxp3, RUNX3 protein level, and the proportion of Treg cells. Besides, there was an interaction between HAGLR and RUNX3. We also found that knockdown of HAGLR and RUNX3 restored the increased Treg cells induced by HAGLR knockdown alone. In vivo experiments indicated that injection with adv-HAGLR increased Treg cell proportion and attenuated DM development. Interference with HAGLR could increase the protein levels of RUNX3, high levels of RUNX3 further promoted the expression of the Foxp3, thus restoring the number of Treg cells and easing the development of DM.

皮肌炎（DM）是一种全身性自身免疫性疾病。众所周知，DM 中调节性 T (Treg) 细胞的数量减少。此外，DM患者治疗后Treg细胞增加。Forkhead box P3 (Foxp3) 在 Treg 细胞中特异性表达，Runt 相关转录因子 (RUNX3) 可以调节 Foxp3 的转录。我们之前的实验表明，同源框 D 基因簇反义生长相关的长链非编码 RNA (HAGLR) 在 DM 患者中上调。在这里，我们旨在探索 HAGLR 是否通过 RUNX3 介导的 Foxp3 转录调节 Treg 细胞的分化，从而影响 DM 的进展。通过定量实时 PCR 检测 HAGLR、Foxp3 和 RUNX3 的水平。通过蛋白质印迹检查 Foxp3 和 RUNX3 的蛋白质水平。CD4中Treg细胞的比例⁺流式细胞仪检测 T 细胞。进行苏木精伊红染色，观察肌肉组织病理学变化。进行 RNA 下拉测定以检测 HAGLR 和 RUNX3 之间的相互作用。进行双荧光素酶报告基因测定以检查HAGLR对RUNX3对Foxp3转录调控的影响。在 DM 患者中，HAGLR 上调，Foxp3 下调。此外，DM患者RUNX3蛋白水平降低，而其mRNA水平没有显着变化。DM患者中Treg细胞的比例下调。此外，干扰HAGLR可增加Foxp3水平、RUNX3蛋白水平和Treg细胞比例。此外，HAGLR 和 RUNX3 之间存在交互作用。我们还发现 HAGLR 和 RUNX3 的敲低恢复了仅由 HAGLR 敲低诱导的增加的 Treg 细胞。体内实验表明注射 adv-HAGLR 增加了 Treg 细胞的比例并减弱了 DM 的发展。干扰HAGLR可以增加RUNX3的蛋白水平，高水平的RUNX3进一步促进了Foxp3的表达，从而恢复了Treg细胞的数量，缓解了DM的发展。