Functional development of human fetal gastrointestinal tract.

The morphological development of the gastrointestinal tract (GI), in laboratory animals as well as in humans, has been well described since more than 100 years. However, even though its functional development and regulatory mechanisms are pretty well understood, our knowledge of the human GI functions originated primarily from studies on rat and mouse. Because of clear differences in genetic make up, development rates and sequences, as well as physiological differences, extrapolations of animal data to the human must be made with caution. A reliable organ culture technique in which the morphological as well as physiological parameters are well maintained has been set up. This technique allows studies of basic physiological functions such as gene expression, localization of specific cell markers, numerous digestive enzymatic activities, and lipid and lipoprotein processing. Furthermore, it also permits to determine and characterize the biological actions of potential regulators such as growth factors and hormones. Finally, the establishment of human intestinal epithelial cell lines allows the validation and the characterization of the molecular mechanisms involved in the specific regulatory pathways of the human GI development.