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

我们的目的是研究在生理条件下调节肠上皮持续更新和损伤后恢复的机制。这一认识将有助于确定维持健康和预防胃肠道疾病的策略。肠上皮形成了肠腔和身体之间的第一道屏障。排列在小肠上的上皮细胞单层具有复杂的结构，在称为绒毛的指状突起之间的称为隐窝的肠壁内陷。几个隐窝围绕绒毛形成一个隐窝-绒毛单位;每个隐窝参与一个以上的单位，为一个以上的绒毛提供细胞。位于每个隐窝底部的肠干细胞增殖并产生上皮细胞，上皮细胞迁移到相邻绒毛的顶端，从那里它们脱落到肠腔中。在健康的肠道中，这个隐窝绒毛单位的尺寸和细胞数量在成年期间保持非常恒定。这意味着细胞从绒毛尖端脱落的速率被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所平衡。因此，维持肠屏障的功能完整性需要紧密协调隐窝和绒毛的数量、隐窝中的细胞产生、细胞沿着隐窝-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导致细胞逃避正常生长控制和肿瘤形成。炎症过程的特征在于增强的细胞脱落，其可能无法通过隐窝内细胞增殖的增加来补偿，导致肠屏障完整性的丧失。此外，腹腔疾病的肠道病变反映了绒毛细胞凋亡和隐窝内细胞增殖之间平衡的严重改变。本提案的主题是深入了解维持肠上皮中隐窝和绒毛之间平衡的机制以及损伤后如何恢复这种平衡。这对于维持胃肠道的健康和开发新的肠道病理学预防策略（如肿瘤发生、溃疡性炎症过程和腹腔疾病）至关重要。然而，这些问题目前不能单独通过实验来解决，因为不可能在长时间内收集整个隐窝/绒毛单位的体内时程成像。为此，数学和/或计算建模代表了一种替代框架，在该框架内进行计算机模拟实验，以补充体外实验方法。我们计划将计算模型与实验数据相结合，以阐明生物物理机制，可以协调细胞增殖的隐窝内，细胞迁移沿着隐窝绒毛轴和细胞脱落的绒毛，以保持小肠内的隐窝和绒毛的数量和大小。然后将进行经验证的模型的计算模拟，以预测损伤后上皮恢复的动态。我们还将确定上皮改变的潜在早期标志物。

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.