ROLE OF PANETH CELLS AND THEIR DEFENSINS IN THE PATHOGENESIS OF SAMP ILEITIS

最近的研究强调了先天性免疫在克罗恩病(CD)发病机制中的重要性。潘氏细胞是先天免疫系统的关键细胞臂，分泌多种参与宿主对微生物区系反应的蛋白质。Paneth细胞还通过产生肿瘤坏死因子、粒细胞巨噬细胞集落刺激因子和其他免疫调节肽，在调节适应性免疫反应中发挥积极作用。最近的研究发现，与CD易感性密切相关的NOD2基因在回肠Paneth细胞中高度表达，这也与Paneth细胞在CD发病机制中的潜在重要性无关。我们在SAMP1/FC小鼠上的初步研究表明，潘氏细胞和中间细胞在疾病活动区显著扩张。SAMP1/FC小鼠是一种类似于人类CD的自发性回肠炎模型。这一建议的中心假设是潘氏细胞在CD的肠炎症发病机制中发挥作用，要么是通过不适当的或持续的促炎介质的阐述，要么是通过肠道微生物区系的独特塑造。 与未受影响的人群不同的构成，或两者都不同。该提案的具体目的是：1)确定SAMP1/FC小鼠回肠中Paneth/中间细胞数量增加的机制。将研究腔菌群和炎性细胞因子在分泌细胞增生的发生中的作用及其与决定疾病易感性的遗传位点的关系；目的2)确定在SAMP1/FC小鼠中，由Paneth/中间细胞调控的防御素和相关多肽的表达是否发生改变及其在回肠炎发病机制中的作用。回肠Paneth细胞防御素和相关基因的表达将在RNA和蛋白质水平上进行表征。将使用有针对性的基因破坏策略来检查它们在疾病发病机制中的作用； 目的3)明确Paneth和中间细胞在回肠炎发病机制中的作用。上皮细胞谱系消融方法将用于这些功能研究。

Recent studies have emphasized the importance of innate immunity in Crohn's disease (CD) pathogenesis. Paneth cells are a key cellular arm of the innate immune system, secreting a variety of proteins involved in the host response to microbiota. Paneth cells also play an active role in regulating the adaptive immune response via their production of TNF, GM-CSF and other immunomodulatory peptides. The potential importance of Paneth cells to CD pathogenesis is also undrelined by the recent finding that NOD2, a gene that is strongly linked to CD susceptibility, is highly expressed in ileal Paneth cells. Our initial studies in SAMP1/Fc mice, a spontaneous model of ilietis resembling human CD, demonstrate marked expansion of Paneth and Intermedate cells in areas of disease activity. The central hypothesis of this proposal is that Paneth cells play a role in the pathogenesis of intestinal inflammation in CD either through the inappropriate or continued elaboration of pro-inflammatory mediators or by a unique molding of the intestinal microflora composition that is different from the unaffected population or both. The specific aims of the proposal are: Aim 1) Determine the mechanism by which the number of Paneth/intermediate cells is increased in the ileum of SAMP1/Fc mice. The contributions of luminal flora and inflammatory cytokines to the genesis of secretory cell hyperplasia and the association of the hyperplasia with genetic loci that determine disease susceptibility will be investigated; Aim 2) Determine whether expression of defensins and related peptides elaborated by Paneth/intermediate cells is altered in SAMP1/Fc mice and their role in the pathogenesis of ileitis. Expression of ileal Paneth cell defensins and related genes will be characterized at both the RNA and protein level. A targeted gene disruption strategy will be used to examine their role in disease pathogenesis; and Aim 3) Determine the functional role of Paneth and intermediate cells in the pathogenesis of ilietis. An epithelial cell lineage ablation approach will be used for these functional studies.