A multidisciplinary approach to studying crypt-villus homeostasis and regeneration in the intestinal epithelium

我们的目的是研究生理条件下肠上皮持续更新的调控机制及其损伤后的恢复。这一认识将有助于确定维持胃肠道(GI)健康和预防疾病的策略。肠道上皮形成肠腔和身体之间的第一道屏障。小肠衬里的上皮细胞单层有一个复杂的结构，内陷进入肠壁称为隐窝，位于手指状突起进入称为绒毛的管腔之间。几个隐窝围绕着一个绒毛，形成一个隐窝-绒毛单元；每个隐窝涉及一个以上的单元，为一个以上的绒毛提供细胞。位于每个隐窝底部的肠道干细胞增殖并产生上皮细胞，上皮细胞迁移到邻近绒毛的顶端，在那里它们被排入肠腔。在健康的肠道中，隐窝绒毛单位上的尺寸和细胞数量在成年后保持显著的恒定。这意味着细胞从绒毛顶端脱落的速率与支持隐窝内产生的新细胞从这些隐窝迁移到绒毛上的速率相平衡。因此，维持肠屏障功能的完整性需要密切协调隐窝和绒毛的数量、隐窝内细胞的产生、细胞沿隐窝-绒毛轴的迁移以及细胞从绒毛脱落。这些过程的调控失败可能会导致细胞逃避正常的生长控制和肿瘤形成。炎症过程的特点是细胞脱落增强，这种脱落可能无法通过腺体内细胞增殖的增加而补偿，从而导致肠道屏障的完整性丧失。此外，乳糜泻的肠道病变反映了绒毛上细胞凋亡和隐窝内细胞增殖之间的严重平衡的改变。这项建议的主题是深入了解维持肠上皮内隐窝和绒毛之间平衡的机制，以及在损伤后这种平衡是如何恢复的。这对于维持胃肠道的健康和开发新的肠道病理预防策略是必不可少的，例如肿瘤发生、溃疡性炎症过程和腹腔疾病。然而，这些问题目前不能仅通过实验来解决，因为不可能在体内收集长时间内整个隐窝/绒毛单位的时程成像。为此，数学和/或计算建模代表了一种替代框架，可以在其中进行补充体外实验方法的硅内实验。我们计划将计算模型与实验数据相结合，以阐明可能协调隐窝内细胞增殖、隐窝绒毛轴上的细胞迁移和绒毛细胞脱落的生物物理机制，以保持小肠内隐窝和绒毛的数量和大小。然后将对经过验证的模型进行计算模拟，以预测损伤后上皮恢复的动力学。我们还将确定病变上皮的潜在早期标志物。

We aim to study the mechanisms regulating the continuous renewal of the intestinal epithelium in physiological conditions and its recovery following injury. This understanding will contribute to the identification of strategies for maintaining the health and preventing diseases of the gastrointestinal (GI) tract.The intestinal epithelium forms the first barrier between the gut lumen and the body. The epithelial cell monolayer lining the small intestine has a complex architecture, with invaginations into the intestinal wall called crypts located between finger-like projections into the lumen called villi. Several crypts surround a villus forming a crypt-villus unit; each crypt is involved in more than one unit, providing cells to more than one villus. Intestinal stem cells located at the base of each crypt proliferate and give rise to epithelial cells, which migrate to the tip of the neighbouring villi, from where they are shed into the gut lumen. In the healthy intestine, the dimensions and cell number on this crypt-villus unit remain remarkably constant during adult life. This implies that the rate of cell shedding from the villus tip is balanced by the rate at which new cells produced within the supporting crypts migrate from these crypts onto the villus. Therefore, the maintenance of the functional integrity of the intestinal barrier requires a tight coordination of the numbers of crypts and villi, cell production in the crypts, cell migration along the crypt-villus axis, and cell shedding from the villus. Failure of regulation of these processes may result in cells escaping normal growth controls and tumour formation. Inflammatory processes are characterized by enhanced cell shedding that may fail to be compensated by the increase of cell proliferation within the crypts leading to the loss of the integrity of the intestinal barrier. In addition, the intestinal lesions in coeliac disease reflect a severe alteration of the balance between cell apoptosis on the villi and cell proliferation within the crypts. The subject of this proposal is gaining insight into the mechanisms underlying the maintenance of the equilibrium between crypts and villi in the intestinal epithelium and how this balance is regained after injury. This is essential to maintain the health of the GI tract and to develop novel preventive strategies for intestinal pathologies such as tumourigenesis, ulcerative inflammatory processes and coeliac disease. However, such questions cannot currently be resolved by experimentation alone, since it is not possible to collect in vivo time course imaging of entire crypt/villus units over prolonged periods. To this end, mathematical and/or computational modelling represents an alternative framework within which to conduct in-silico experiments that complement the in-vitro experimental approaches. We plan to integrate computational models with experimental data to elucidate the biophysical mechanisms that may coordinate cell proliferation within the crypt, cell migration along the crypt-villus axis and cell shedding from the villus in order to preserve the numbers and size of crypts and villi within the small intestine. Computational simulations of the validated models will then be performed to predict the dynamics of epithelial recovery after injury. We will also identify potential early markers of altered epithelium.