The development of novel vascularization strategies for tissue constructs is still one of the major challenges in tissue engineering and regeneration. In the present study we investigate the establishment of vascular networks in the absence and presence of fluid flow conditions using a microfluidic co-culture system. In the presented configuration adipose derived stem cells (ASCs) and human umbilical vein cells (HUVEC) are embedded within a 3D fibrin matrix to study accumulation and depletion of ASCs secreted paracrine pro-angiogenic factors on vascular tube formation. Initial experiments using fluorescently labelled bovine serum albumin confirmed rapid transport of biomolecules within the fibrin matrix over a distance of various millimeters. Results using 3D co-cultures showed that even in the presence of low fluid mechanical shear forces of 0.025 dyn/mm
the onset and maturation of vascular endothelial networks formation were significantly affected, leading to altered tube size and tube length.