Abstract: The present invention relates to a method of culturing and/or monitoring epithelial cells using a microfluidic cell culture system comprising a microfluidic channel network. In the method epithelial cells are lined, in the microfluidic cell culture system by cells of mesenchymal origin. The cells may form a tubular or tube-like structure, i.e. a.tube in a tube. The method allows for improved epithelial models suitable for a wide variety of applications, including but not limited to high-throughput screening and analysis of epithelium in health and disease.