Pathogenic Role of Mechanical Stress in Fibrosis and Tissue Remodeling in Crohn's Disease

由于组织纤维化和平滑肌增生而形成的狭窄是严重克罗恩病的一个特征 疾病(CD)。虽然狭窄的形成与慢性炎症有关，但没有抗炎作用。 除手术治疗外，治疗是有效的。然而，术后狭窄前期的复发 地区几乎是100%。炎症非依赖性机制在纤维化中可能作用的研究 和增生性疾病是必要的。与组织变形、水肿、纤维化和 在CD中经常会遇到膨胀现象。我们假设多发性硬化症在纤维化和 CD增生症。我们发现，在一种明确的CD啮齿动物模型中，结肠内注射TNBS诱导了 局限性的跨壁炎症，远端结肠管腔变窄，结肠壁明显扩张 炎性节段近端。我们发现结缔组织生长因子(CTGF)和 结肠平滑肌细胞(SMC)脑源性神经营养因子(BDNF)不仅被显著诱导 在炎症部位，但在炎症近端的膨大节段。我们还发现了显著的 21d时炎症部位和炎症近端的纤维化和增生。这个 炎症远端的非膨胀节段没有显示任何CTGF和BDNF的增加，也没有显示纤维化和 增生，表明MS依赖机制。此外，如果通过以下方式防止机械膨胀 只给大鼠喂流食，这类似于CD管理中的独家肠内营养(EEN)， 结缔组织生长因子和脑源性神经营养因子的表达明显减弱，纤维化明显改善。 机械牵张诱导结缔组织生长因子和脑源性神经营养因子在结肠SMC表达并激活转录 激活因子是相关蛋白-1(YAP)。此外，在纤维狭窄患者中发现YAP活性显著升高。 人体内的CD组织。我们认为CD的跨壁炎症导致炎症部位的MS，并且 炎症近端的膨大节段，MS诱导YAP依赖的机械敏感性 结缔组织生长因子和脑源性神经营养因子的表达，促进肝纤维化和增生性病变。这项研究的具体目的 目的：1.探讨MS是否参与CD的肠纤维化和SMC增生。我们将差异化 通过评估纤维化、SMC生长和表达的部位特异性变化来评价炎症对MS的影响 CTGF和BDNF在炎症部位(既有炎症又有MS)，近端(有 MS)和远端(既无炎症也无MS)至CD模型炎症部位。微软的角色在 在没有MS的CD(流食大鼠)和CD中将进一步评估ECM产生和SMC增殖。 在仅具有MS的模型中(机械障碍)。2.探讨MS诱导的信号转导机制 YAP激活及依赖YAP的CTGF和BDNF表达。3.研究其致病作用 YAP介导CTGF和BDNF在纤维化和增生性病变中的机械敏感性表达。可能的 炎症和MS在纤维化和增生中的合作也将被调查。

Stricture formation due to tissue fibrosis and smooth muscle hyperplasia is a hallmark of severe Crohn’s disease (CD). Although stricture formation is associated with chronic inflammation, no anti-inflammatory treatment is effective for it, except surgical approaches. However, post-surgery recurrences in the pre-stenotic region are almost 100%. Studies into the possible role of inflammation-independent mechanisms in fibrosis and hyperplasia are needed. Mechanical stress (MS) associated with tissue deformation, edema, fibrosis, and distention are commonly encountered in CD. We hypothesize that MS plays a critical role in fibrosis and hyperplasia in CD. We found in a well-defined rodent model of CD that intracolonic injection of TNBS induced a localized transmural inflammation with lumen narrowing in the distal colon and marked distention in the segment proximal to inflammation. We found that expression of connective tissue growth factor (CTGF) and brain-derived neurotrophic factor (BDNF) in colon smooth muscle cells (SMC) was markedly induced not only in the inflammation site but in the distended segment proximal to inflammation. We also detected significant fibrosis and hyperplasia in the inflammation site and the segment proximal to inflammation by 21 days. The non-distended segment distal to inflammation did not show any increased CTGF and BDNF, or fibrosis and hyperplasia, indicating a MS dependent mechanism. Furthermore, if mechanical distention was prevented by feeding rats with only liquid diet, which mimics exclusive enteral nutrition (EEN) in CD management, expression of CTGF and BDNF was dramatically attenuated and fibrosis was significantly improved. Mechanical stretch in vitro induced expression of CTGF and BDNF in colon SMC, and activated transcription activator yes-associated protein-1 (YAP). Moreover, YAP activity is found markedly increased in fibrostenotic CD tissues in humans. We propose that transmural inflammation in CD causes MS in the inflammation site and the distended segment proximal to inflammation, and the MS induces YAP-dependent mechanosensitive expression of CTGF and BDNF, which contribute to fibrosis and hyperplasia. The specific aims of the study are: 1. To determine if MS plays a role in intestinal fibrosis and SMC hyperplasia in CD. We will differentiate the effect of MS from inflammation by assessing site-specific changes of fibrosis, SMC growth, and expression of CTGF and BDNF in the site of inflammation (with both inflammation and MS), the segments proximal (with MS) and distal (with neither inflammation nor MS) to the inflammation site in the CD model. The role of MS in ECM production and SMC hyperplasia will be further assessed in CD without MS (rats fed with liquid diet) and in a model with MS only (mechanical obstruction). 2. To investigate the signaling mechanisms of MS-induced YAP activation and YAP-dependent expression of CTGF and BDNF. 3. To examine the pathogenic roles of YAP mediated mechanosensitive expression of CTGF and BDNF in fibrosis and hyperplasia. The possible cooperation between inflammation and MS in fibrosis and hyperplasia will be investigated as well.