Abstract

Thymic epithelial cells (TECs) are essential regulators of T-cell development and selection. miRNAs play critical roles in regulating TEC proliferation during the process of thymic aging. Our previous studies revealed that miR-199b-5p was upregulated in TECs from 1- to 3-month-old mice. But its function and potential mechanism are not clear. We hypothesized that miR-199b-5p may play an important role in age-related thymus involution via targeting some genes. To confirm it, the murine thymic epithelial cell line 1 (MTEC1) cells were used. Our results showed that overexpression of miR-199b-5p can enhance MTEC1 cell proliferation. On the contrary, repression of miR-199b-5p can inhibit MTEC1 cell proliferation. Meanwhile, it was confirmed that frizzled receptor 6 (Fzd6) is the direct target gene of miR-199b-5p. Furthermore, overexpression of miR-199b-5p can upregulate the expressions of β-catenin, Tcf7, Wnt4, and C-myc to activate Wnt signaling and cell cycle signaling. Silence of Fzd6 and co-transfection with siFzd6 and miR-199b-5p mimic/inhibitor confirmed that the biological function of miR-199b-5p is indeed by targeting Fzd6 in medullary TECs. Overall, miR-199b-5p is an important regulator in medullary TEC proliferation through targeting Fzd6 to activate Wnt signaling and cell cycle signaling. Our data indicate that miR-199b-5p may block the process of thymic aging and be a potential therapeutic target for thymus involution.

中文翻译：

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miR-199b-5p通过靶向Fzd6调节Wnt信号传导来增强髓样胸腺上皮细胞的增殖

摘要

胸腺上皮细胞（TECs）是T细胞发育和选择的重要调节剂。在胸腺衰老过程中，miRNA在调节TEC增殖中起关键作用。我们以前的研究表明，miR-199b-5p在1至3个月大的小鼠的TECs中上调。但是其功能和潜在机制尚不清楚。我们假设miR-199b-5p通过靶向某些基因可能在与年龄有关的胸腺退化中发挥重要作用。为了证实这一点，使用了鼠胸腺上皮细胞系1（MTEC1）细胞。我们的结果表明，miR-199b-5p的过度表达可以增强MTEC1细胞的增殖。相反，抑制miR-199b-5p可以抑制MTEC1细胞的增殖。同时，确认了卷曲的受体6（Fzd6）是miR-199b-5p的直接靶基因。此外，miR-199b-5p的过表达可以上调β-catenin，Tcf7，Wnt4和C-myc的表达，从而激活Wnt信号和细胞周期信号。Fzd6沉默并与si Fzd6和miR-199b-5p模拟物/抑制剂共转染证实，miR-199b-5p的生物学功能确实是通过靶向髓质TEC中的Fzd6。总体而言，miR-199b-5p通过靶向Fzd6激活Wnt信号传导和细胞周期信号传导，成为髓样TEC增殖的重要调节剂。我们的数据表明，miR-199b-5p可能会阻断胸腺衰老的过程，并可能成为胸腺退化的潜​​在治疗靶点。