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ObjectiveIncreased apoptotic shedding has been linked to intestinal barrier dysfunction and development of inflammatory bowel diseases (IBD). In contrast, physiological cell shedding allows the renewal of the epithelial monolayer without compromising the barrier function. Here, we investigated the role of live cell extrusion in epithelial barrier alterations in IBD.DesignTaking advantage of conditional GGTase and RAC1 knockout mice in intestinal epithelial cells (Pggt1biΔIEC and Rac1iΔIEC mice), intravital microscopy, immunostaining, mechanobiology, organoid techniques and RNA sequencing, we analysed cell shedding alterations within the intestinal epithelium. Moreover, we examined human gut tissue and intestinal organoids from patients with IBD for cell shedding alterations and RAC1 function.ResultsEpithelial Pggt1b deletion led to cytoskeleton rearrangement and tight junction redistribution, causing cell overcrowding due to arresting of cell shedding that finally resulted in epithelial leakage and spontaneous mucosal inflammation in the small and to a lesser extent in the large intestine. Both in vivo and in vitro studies (knockout mice, organoids) identified RAC1 as a GGTase target critically involved in prenylation-dependent cytoskeleton dynamics, cell mechanics and epithelial cell shedding. Moreover, inflamed areas of gut tissue from patients with IBD exhibited funnel-like structures, signs of arrested cell shedding and impaired RAC1 function. RAC1 inhibition in human intestinal organoids caused actin alterations compatible with arresting of cell shedding.ConclusionImpaired epithelial RAC1 function causes cell overcrowding and epithelial leakage thus inducing chronic intestinal inflammation. Epithelial RAC1 emerges as key regulator of cytoskeletal dynamics, cell mechanics and intestinal cell shedding. Modulation of RAC1 might be exploited for restoration of epithelial integrity in the gut of patients with IBD.

Experiments play an important role in the education of undergraduate engineering students as they provide hands-on experience on the foundations of the discipline. Unfortunately, the recent change of the university program in Germany from the Diploma to the Bachelor/Master model had a direct negative impact on the curricula and the course schedules. The result of which is that the first-year curriculum is overloaded; exercises or practical courses have been dropped altogether from the first term, have been rescheduled to later terms and have been reduced in length. For this reason, other forms of experimenting have to be developed and integrated into the existing courses or lectures; virtual laboratories and remote experiments offer such an option: they enable students to access equipment 24h/7 days a week, they are independent from opening hours and the work schedule of the staff. Furthermore, simulations do have some other advantages: they provide a better control on the simulated phenomenon, allow observing effects and running experiments that are only very hard to measure or perform in practical applications. Another advantage besides their cost-efficiency is that simulations allow observations of effects in a simplified environment without any measurement errors. Therefore, remote and virtual experiments have already or will soon be set up by various universities across Europe. However, building a pool of experiments sufficient to cover all of undergraduate physics is an overwhelmingly complex and costly task for a single university to handle on its own. Therefore, the EUfunded LiLa project -short for "Library of Labs" -is building a network of virtual laboratories and remote experiments. The LiLa Portal provides access to manifold experiments, free to use in courses and lectures. Additionally, LiLa partners will profit from the experience gained from using remote experiments, and the LiLa network will provide best-practices in applications of remote experiments. This article starts with an introduction of LiLa and its aims; it then presents the integration of virtual labs and remote experiments into an existing course, "Physics for Engineers", at the University of Stuttgart. We introduce our concept for exercises with online-experiments and present some results of the pilot phase which took place in the winter term 2009/2010 and also some results on the winter term 2010/2011.