RORγt 的siRNA 在乾癬動物模型的治療應用

Abstract

乾癬(Psoriasis)為常見的慢性皮膚發炎病變的疾病，由於免疫失調或是乾癬易感性基因誘發表皮細胞生長速度增加、角化不全及脫屑等現象，且會併發乾癬性關節炎等，嚴重影響患者的生活品質。過去研究發現T細胞族群中的17型T輔助細胞(Th17 cells)在乾癬發病中扮演重要角色，其免疫機制由炎性髓樣樹突狀細胞 (inflammatory myeloid dendritic cells)釋放介白素23(interleukin-23, IL-23)與Th17 cells作用，從而產生豐富的促發炎細胞因子造成皮膚發炎，如: IL-17、干擾素-γ (interferon-γ, IFN-γ)、腫瘤壞死因子(tumor necrosis factor, TNF)和IL-22。且目前已有IL-23、IL-17A單株抗體藥物對乾癬的皮膚和關節產生實質性的有益反應，如:Tildrakizumab和Secukinumab等藥物。隨著治療乾癬的分子和遺傳病理機制不斷被闡明，藥物也不斷地被開發，但口服或注射所造成的副作用相對局部應用大，因此我們想利用潛在的免疫治療靶點進行研究與開發局部siRNA塗抹的藥物。我們的研究將針對造成乾癬重要的Th17細胞的轉錄因子為RAR-related orphan receptor γ t (RORγt)作為治療靶點，利用慢病毒載體遞送siRNA 進入皮膚內進行基因沉默，藉此減少Th17細胞的分化及IL-17等細胞因子的生成來達到治療的效果。由我們的研究結果證實了針對RORγt的siRNA在體外的功性，確認其siRNA序列能有效抑制IL-23/IL-17軸的訊息路徑，而後利用水凝膠及帶有針對RORγt的siRNA慢病毒載體塗抹至乾癬小鼠進行治療，由皮膚切片及促發炎基因表現量中顯示有不錯的治療效果。在未來的研究，我們將選擇微針 (microneedle)更具生物相容性的方式，將此siRNA遞送入皮下進行局部治療，這將會是個新興的治療方式。

Psoriasis is mediated by the immune cells which pro-inflammatory cell lineage mainly is T helper 17 cells (Th17 cells). Th17 cells produced abundant inflammatory cytokines by myeloid dendritic cells, such as IL-17, IFN-γ, TNF and IL-22. Currently, the drug development of monoclonal antibodies against IL-17 and IL-23 including Secukinumab and Tildrakizumab. However, oral administration or injection can cause more side effects. Therefore, we want to use potential immunotherapeutic targets for research and development of siRNA drugs for topical application. We aimed to target the retinoic acid-receptor-related orphan receptor (RORγt) transcription factor of Th17 cells through the siRNA against RORγt deliver into the skin via lentiviral vector. It can reduce the differentiation of Th17 cells and the production of pro-inflammatory cytokines such as IL-17 to achieve therapeutic effects. Therefore, our study confirmed the functionality of the siRNA targeting RORγt in vitro, and has a significant therapeutic effect in the imiquimod (IMQ) induced psoriasis model. In the future, we will choose a more biocompatible way of microneedles to delivery siRNA into the subcutaneous for topical treatment. It might become a novel therapeutic modality for psoriasis.