Fabrication of Three-Dimensional Tissues with Perfused Microchannels

Recently, researchers have challenged to create three-dimensional (3-D) tissues with tissue engineering technology in order to establish in vitro models and new therapy for damaged organ. We have developed cell-sheet based tissue engineering and successfully fabricated pulsatile 3-D myocardial tissues both in vivo and in vitro by layering cardiac cell sheets. However, in vitro scaling up of 3-D cell-dense tissues is limited due to lack of blood vessels supplying oxygen and nutrition and removing waste molecules. In this study, we have developed novel bioreactor culturing layered cell sheets on collagen-based microchannels and examined cell behavior between tissues and channels. Rat cardiac cells including endothelial cells were cultured on temperature responsible culture dishes for 4 days. By lowering temperature, confluent cardiac cells were harvested as an intact cell sheet and two cardiac cell sheets are layered. Collagen-based microchannels were engineered by gelling collagen around parallel stainless wires and extracting the wires. The double-layer cell sheets were put on the microchannels and the constructs were connected to the novel perfusion bioreactor. After 5 days of cultivation, the tissue sections were stained with Hematoxylin-Eosin and endothelial cell specific Isolectin B4. HE staining demonstrated that layered cell sheets tightly connected onto the collagen microchannels. The microchannels maintained their patency during culture period. The cardiac cells migrated into collagen gel and the number of migration increased flow-rate dependently. At higher flow-rate, some cardiac cells reached to microchannels and covered over their inner surface. Isolectin B4 staining showed endothelial cells formed networks within the cell sheets and also played as migrating cells. We have successfully fabricated 3-D tissues with perfused microchannels and tissueoriginated cells migrated and communicated with the microchannels. These results showed new insights regarding in vitro vascular formation and indicated the possibility for fabricating vascularized 3-D tissues.