MSC-exosomes促进巨噬细胞分泌IL-27治疗SS-ILD作用机制

The interstitial lung disease (ILD) is the common complication of Sjögren’s syndrome (SS) and a leading cause of death among SS patients. Mesencymal stem cell-derived exosomes (MEX) have immunomodulation potential. MEX can reduce potential risks associated with cellular therapies, such as pulmonary embolism. Therefore, MEX may be emerging as a novel clinically-viable therapy. However, the therapeutic effects and underlying mechanisms of MEX on SS-ILD remain unclear. Our previous studies showed that the SS-ILD could be alleviated by infusion of MEX in NOD mice. Many studies have provided evidence for the important role of macrophages (Mø) on lymphocytic infiltration in SS-ILD. Our results also indicated that IL-27 production by Mø regulated many lymphocyte subsets in SS. Therefore, we hypothesized that the beneficial effects of MEX on SS-ILD are related to regulating production of IL-27 by Mø and inhibiting infiltrating lymphocytes in lung. To testify this hypothesis, we aim to explore the effects of MEX on SS-ILD and the role of IL-27 from Mø in inhibiting infiltrating lymphocytes in wild-type and established IL-27 knockout NOD mice. The key molecule within MEX, which regulates IL-27 production by Mø will also be determined. The findings of the present study will reveal the underlying molecular mechanism of beneficial effects of MEX on SS-ILD. The results will also provide evidence for clinical translational research and practical clinical settings.

间质性肺疾病(ILD)是干燥综合征(SS)常见并发症,也是SS患者死亡主要原因之一。间充质干细胞来源外泌体(MEX)具有免疫调节作用,避免了细胞移植导致肺栓塞的风险,是治疗新策略。但是MEX治疗SS-ILD作用和机制不明。文献和我们前期研究表明MEX治疗SS鼠ILD有效,肺脏巨噬细胞(Mø)在SS-ILD炎症细胞浸润中起关键作用,以及Mø分泌IL-27具有调节多种淋巴细胞作用。因此,我们提出科学假说:MEX通过调控Mø分泌IL-27来抑制肺部淋巴细胞浸润,治疗SS-ILD。为了验证这一假说,我们应用已构建IL-27基因敲除SS鼠,确认MEX治疗SS-ILD与Mø分泌IL-27的关系;阐明MEX调控Mø分泌IL-27抑制肺部浸润特异淋巴细胞亚群的机制;解析MEX中特异调控Mø分泌IL-27的关键分子。本研究不仅能揭示MEX治疗SS-ILD分子机制,而且为临床转化和推广MEX治疗疾病提供依据。

干燥综合征（SS）是一种慢性系统性自身免疫疾病，主要侵犯泪腺、唾液腺等。SS可累及肺脏、肝脏、肾脏等多器官。SS 相关肺疾病常常表现为间质病变，这是由于肺部腺体功能异常、黏膜防御功能受损，增加了肺部炎症易感性，引发间质性肺疾病（ILD）。SS 相关 ILD（SS-ILD）是患者致残和致死的主要原因。与不伴肺部受累SS 患者相比，SS-ILD 患者生活质量和生理功能受到严重损伤。SS-ILD多数进展缓慢，但是部分患者肺功能呈逐年下降趋势，甚至发生急性加重。这类患者应予以积极治疗，治疗措施包括糖皮质激素和免疫抑制剂，或者生物制剂。但是，仍有一部分经上述治疗后病情不能缓解的重症/难治性 SS-ILD患者。本项目研究了模型小鼠中髓系来源抑制性细胞（MDSC）数目和功能改变在SS及其ILD样症状中的作用；应用间充质干细胞（MSC）或其外泌体治疗SS模型小鼠；检测和比较了SS和SS-ILD样症状变化情况；探索了MSC及其外泌体通过调控MDSC改善SS和SS-ILD的分子机制；研究结果发现，随着小鼠SS样疾病进展，外周血MDSCs数量显著增加。与正常小鼠相比，具有SS样症状的NOD小鼠MDSCs表面未成熟标志物表达量明显降低。尾静脉过继移植纯化的MDSCs至NOD小鼠，颌下腺淋巴细胞浸润情况加重，唾液流量显著降低，ILD病变加重。而腹腔注射MDSCs功能抗体后，颌下腺淋巴细胞浸润情况缓解，唾液流量显著升高，ILD病情减轻。给SS样NOD小鼠尾静脉移植MSC或者其外泌体后，颌下腺导管周围淋巴细胞浸润灶及浸润面积显著减少，分泌功能增强，ILD明显减轻，炎性因子IL-17水平显著降低；骨髓、外周血和脾脏中MDSCs比例显著降低，MDSCs的两个亚群G-MDSCs和M-MDSCs比例也都显著降低，血浆中IL-27显著降低。机制研究表明，MSC及其外泌体促进肺部巨噬细胞产生IL-27, MDSCs表面高表达IL-27受体，IL-27可明显抑制MDSCs和G-MDSCs分化。本项目的系列研究结果提示，MSC来源外泌体促进肺部巨噬细胞产生IL-27, IL-27抑制MDSCs数目和功能，从而治疗SS-ILD。这些原创性发现不仅具有阐明SS-ILD发病的新免疫机制，揭示MSC来源外泌体改善SS-ILD新分子机制的理论意义，而且具有为推广应用MSC来源外泌体治疗临床SS-ILD患者的实际意义。