Department of Orthopedics and Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.
Department of Orthopedics, Sun Yat-sen University Eighth Affiliated Hospital, Sun Yat-sen University, Shenzhen, China.
Stem Cells Dev. 2019 Oct 15;28(20):1398-1412. doi: 10.1089/scd.2019.0039.
The pathogenesis of ankylosing spondylitis (AS), an immune-mediated inflammatory disease, remains largely unknown. We previously reported that the immunoregulatory function of mesenchymal stem cells (MSCs) was dysfunctional in AS. Furthermore, it has been demonstrated that TLR3 and TLR4 could regulate the immunoregulatory function of MSCs. Therefore, this study aimed to investigate the effect of TLR3 and TLR4 activation on the immunoregulatory function of AS-MSCs. By gene expression and western blot analyses, we found that both TLR3 and TLR4 in AS-MSCs to be downregulated when compared with MSCs derived from healthy donors (HDs). Despite the lower basal expression of TLRs, AS-MSCs were as sensitive or more sensitive to TLR agonists as compared with HD-MSCs in terms of activation of p38 and ERK MAPK signaling pathways. Furthermore, TLR4-primed AS-MSCs were observed to possess enhanced immunoregulatory effects against the proliferation of naive CD4 T cells than HD-MSCs due to elevated IL-10 production. However, TLR activation or the source of MSCs did not affect MSC-induced differentiation of naive CD4 T cells to Th17 cells. Similarly, the MSC-induced inhibition of Treg cell differentiation of naive CD4 T cells was not affected by TLR activation or MSC source. MSC-induced Th17 differentiation was likely mediated by the elevated secretion of proinflammatory cytokines, IL-6 and IL-17, and reduced expression of IL-2, IL-4, and IFN-γ, which were not affected by TLR activation. Taken together, our results suggest that TLR3 and TLR4 may play an important role in the immunoregulatory function of MSCs in AS patients.
强直性脊柱炎（AS）是一种免疫介导的炎症性疾病，其发病机制在很大程度上尚不清楚。我们之前的研究报道称，间充质干细胞（MSCs）的免疫调节功能在 AS 中出现了功能障碍。此外，已经证实 TLR3 和 TLR4 可以调节 MSCs 的免疫调节功能。因此，本研究旨在探讨 TLR3 和 TLR4 激活对 AS-MSCs 免疫调节功能的影响。通过基因表达和 Western blot 分析，我们发现与来自健康供体（HD）的 MSC 相比，AS-MSCs 中的 TLR3 和 TLR4 表达下调。尽管 TLR 的基础表达水平较低，但与 HD-MSCs 相比，AS-MSCs 在 TLR 激动剂激活 p38 和 ERK MAPK 信号通路方面同样敏感或更敏感。此外，由于 IL-10 产生增加，TLR4 预刺激的 AS-MSCs 表现出对幼稚 CD4 T 细胞增殖的增强免疫调节作用，优于 HD-MSCs。然而，TLR 激活或 MSC 来源并不影响 MSC 诱导的幼稚 CD4 T 细胞向 Th17 细胞的分化。同样，TLR 激活或 MSC 来源也不影响 MSC 诱导的幼稚 CD4 T 细胞向 Treg 细胞分化的抑制作用。MSC 诱导的 Th17 分化可能是通过上调促炎细胞因子 IL-6 和 IL-17 的分泌和下调 IL-2、IL-4 和 IFN-γ 的表达来介导的，而 TLR 激活对这些因子没有影响。综上所述，我们的研究结果表明 TLR3 和 TLR4 可能在 AS 患者 MSC 的免疫调节功能中发挥重要作用。
