In vitro model of a vascular stroma for the engineering of vascularized tissues.

A major problem for the in vitro engineering of larger tissue equivalents like those required in reconstructive surgery is the lack of solutions for sufficient nutrition and oxygenation. The starting point of our investigation was the question of whether the principles of in vitro angiogenesis can be applied and utilized for tissue engineering. A soft tissue model was developed, consisting of human adipose tissue stromal cells and umbilical vein endothelial cells in a fibrin-microcarrier scaffold. Capillary-like structures were visualized using UEA-I-lectin labelling and confocal laser scanning microscopy. Length of capillary-like structures was measured in an image analysis system. Under serum-free culture conditions, maintenance of capillary-like structures was significantly increased in comparison to serum-containing cultures. The application of vascular endothelial growth factor (VEGF) resulted in a high initial angiogenic response; long-term stabilization of capillary-like structures could not be achieved, however supplementation with IGF-1 resulted in the highest values and the slightest decrease in length of capillary-like structures, so that the results could be interpreted as an improved stabilization.