Intestine model (human/porcine)
Fraunhofer Institute for Interfacial Engineering and Biotechnology
- Human intestinal villus
The small intestine is the organ where the majority of digestion takes place. Nutrients are made accessible to the body by the absorption through the mucous layer and the intestinal lining epithelial layer functions as an effective barrier against the systemic access of substances and therefore has crucial influence on the bioavailability of orally administered drugs. The knowledge of the absorption and metabolism of active ingredients at the intestinal mucosa is of particular significance, since the oral bioavailability of a drug is defined as the fraction of an oral dose that reaches the systemic circulation. The failure of many drug candidates in the later phase of clinical trials due to a restricted translatability of preclinical data emphasizes the need of the design of standardized and validated human-based test systems.
At the Frauhofer IGB, we develop human based intestinal test systems for the evaluation of absorption across the intestinal barrier.
- Caco-2 cells cultured under static culture conditions on a commercial available PET membrane.
- Caco-2 cells cultured under static culture conditions on decellularized scaffolds.
- Caco-2 cells assemble as multilayers composed of highly prismatic cells, similar to the enterocytes in vivo.
2D test model
The standardized in vitro model for the investigation of absorption mechanisms at the intestinal barrier is based on a 2D test system with Caco-2 cells (colon carcinoma cell line), which is cultured on an artificial PET insert membrane. This test system was considerably improved in the Department of Cell and Tissue Engineering by modifying the cell culture conditions.
3D test system
We developed a dynamic 3D cell co-culture of human Caco-2 cells with primary-isolated human microvascular endothelial cells (hMECs) on decellularized porcine jejunal segments within a custom-made dynamic bioreactor system resembling the apical and basolateral side of the intestine. After 14 days, histological analyses revealed that the Caco-2 cells resembled normal primary enterocytes within their native environment, with a high-prismatic morphology. In comparison to dynamic cultures, cells cultured under static conditions are flattened. We further evaluated the transport of low permeable substances, such as fluorescein and desmopressin, which increased within the dynamic bioreactor cultures. Immunohistochemical staining showed a significantly higher expression of the efflux transport p-glycoprotein (p-gp) under dynamic culture conditions in comparison to static cultures.
The 3D intestine test system allows the investigation of resorption, toxicity and bioavailability of orally applied active substances and targeted improvement of formulations. It is also a novel model for the exploration of basic science questions regarding intestinal development and crypts.
The physiological performance of a three-dimensional model that mimics the microenvironment of the small intestine, Biomaterials (2011)