Effect of Pore Size of Honeycomb‐Patterned Polymer Film on Spontaneous Formation of 2D Micronetworks by Coculture of Human Umbilical Vein Endothelial Cells and Mesenchymal Stem Cells

The geometrical control of micronetwork structures (μNSs) formed by endothelial cells is an important topic in tissue engineering, cell‐based assays, and fundamental biological studies. In this study, μNSs are formed using human umbilical vein endothelial cells (HUVECs) by the coculture of HUVECs and human mesenchymal stem cells (MSCs) confined in a honeycomb‐patterned poly‐l‐lactic acid film (honeycomb film (HCF)), which is a novel cell culture scaffold. The HCF is produced using the breath figure method, which uses condensed water droplets as pore templates. The confinement of the HUVECs and MSCs in the HCF along with the application of centrifugal force results in μNS formation when the pore size is more than 20 μm. Furthermore, μNS development is geometrically restricted by the hexagonally packed and connected pores in the horizontal direction of the HCF. Network density is also controlled by changing the seeding density of the HUVECs and MSCs. The threshold pore size indicates that μNSs can be formed spontaneously by using an HCF with a perfectly uniform porous structure. This result provides an important design guideline for the structure of porous cell culture scaffolds by applying a blood vessel model in vitro. Micronetwork structures of cocultured human umbilical vein endothelial cells and mesenchymal stem cells are successfully formed within the pores of honeycomb‐patterned poly‐l‐lactic acid films. The results indicate that structurally well‐controlled tailored capillary networks can be obtained using the films and used as a cell culture platform for oxygen‐requiring organoids and for evaluating cell–cell interactions throughout the vascular system.