Th17在過敏性呼吸道再塑型機轉所扮演的角色

Abstract

氣喘是一種慢性呼吸道發炎的疾病，伴隨有呼吸道再塑型，大量嗜酸性球進入呼吸道，及呼吸道過度反應等的症狀。其中，呼吸道過度反應的症狀在病理學上則出現因受到各式發炎刺激而發生呼吸道結構改變的情形。在這種情況下，呼吸道纖維化的情形增加，表皮細胞及呼吸道平滑肌增生，杯狀細胞的增大及增生，及呼吸道黏液增加。第十七型輔助型T細胞（Th17）是近年被發現的一種特殊輔助型T細胞，因其可分泌IL-17家族的細胞激素（cytokine）而被命名，主要參與免疫調控及發炎反應，其中也包括呼吸道再塑型。為了瞭解Th17在呼吸道再塑型的發展過程中扮演的角色，我們利用雞卵蛋白（OVA）先經兩次腹腔注射，再接著連續四個禮拜利用含OVA蒸汽刺激小鼠呼吸道而建立的小鼠慢性呼吸道發炎動物模式來研究。我們在不同時間點收取肺及肺泡沖洗液（Bronchial alveolar lavage fluid, BALF）。一半的肺進行 H & E 及 PAS等化學組織染色，以同步觀察氣喘條件下肺及呼吸道的病理發展，另一半的肺利用液態氮磨碎後抽取RNA以偵測Th17 相關因子在不同時間點的表現量，肺泡沖洗液離心取上清液測定呼吸道內各種Th17相的cytokines 含量，同時利用劉氏染色分離參與病程的細胞種類。從化學組織染色的結果可以看到當刺激的時間越長，以OVA刺激的小鼠組別在進入呼吸道的細胞，呼吸道壁的增厚及杯狀細胞的增生情形隨著時間越見顯著。在刺激初期(第22天)可以看到Th17相關因子，像是IL-17A，IL-6，IL-23R 基因表現量增加，Rorc的表現量有增高的趨勢，雖然TGF-β1的基因表現量在各時間點沒有顯著差異，但在肺泡沖洗液中，TGF-β1可在刺激的第22, 29天開始被偵測到，時間點和Th17相關因子基因表現量吻合。從化學組織染色的結果可以看到當刺激的時間越長，也就是大約第22, 29天之後，氣喘及呼吸道再塑型的情況越見明顯。先前已經有研究指出，在IL-17A缺乏的環境下，呼吸道再塑型及呼吸道過度反應等氣喘情況可被部分緩解，對照此動物模式之下的實驗結果，Th17的存在可能扮演呼吸道再塑型形成的信號。

Asthma is characterized by chronic allergic airway inflammation with remodeling, cell infiltration in lung, and airway hyper-responsiveness (AHR) to stimulations. Airway remodeling is structural changes of asthmatic airway, featured by increased fibrosis, epithelial hyperplasia, myocyte hyperplasia, and increased mucus secretion. Th17 cell is a kind of T helper cells with the ability to secrete IL-17 family cytokines and regulate immune responses and various kinds of inflammation, including airway remodeling. However, the role of Th17 in airway remodeling remains unknown. Here we established an OVA- sensitized animal model of asthmatic airway remodeling to investigate the role of Th17 in the progressing of airway remodel. By sacrificing the mice at different time points and simultaneously evaluated the AHR, we collected lung, for H & E and PAS staining, to display the remodeling progress of asthmatic airway, and for quantitative real-time PCR, to show the expression time and level of Th17-related factors (IL-17A, Rorc, IL-6, and IL-23R). Aligning with the results of Th17-related cytokines profile in bronchial alveolar lavage fluid (BALF), we hope to dissect the role of Th17 in the pathogenesis of airway remodeling. The results showed that an early expression of Th17-related factors in the process of the disease. Although there is no significant differences of TGF-β1 at different time points, the expression pattern of TGF-β1 in BALF align with the expression trend of Th17-related factors. Compared to histochemical staining, the existences of Th17-related factors seem to be closely followed by the subsequent progression of airway remodeling, enhanced cell infiltration, and thickening of airway wall. Although more studies are needed, Th17 might be involved in the process to trigger airway remodeling and other relative pathological changes.