[Prevascularisation strategies in tissue engineering]

Introduction Experiments on animals have underlined the importance of vascularisation for biointegration and functionality of any given tissue engineering device. The aim of this investigation was to dissect the angiogenetic process in the frame of axial neovascularisation of a xenogenic solid matrix. The ultimate goal of this series of studies is the application of cells onto a prevascularised matrix, with the ambition to enhance cell survival after transplantation in vivo. Materials and methods We performed a study in the rat with different vascular configurations in an isolation chamber. A disc-formed biogenic hard matrix (9 x 5 mm) was encased into an isolation chamber made of Teflon. In group 1, an arteriovenous fistula (AV loop) between the femoral vessels was microsurgically constructed and was placed around the matrix (n = 15). In group 2, the vascular carrier had the form of an arteriovenous ligated pedicle (n = 15). Evaluation intervals were two, four and eight weeks after implantation. The modes of evaluation included histology, scanning electron microscopy of corrosion casts as well as intravital micro-magnetic resonance imaging (MRI). Results The arteriovenous loop as vascular carrier revealed a higher capacity for angiogenesis over the bundle configuration. The neo-fibrovascular tissue displayed minimal inflammatory elements but dense vascularisation. Scanning electron microscopy demonstrated a vivid angiogenesis with rapid evolution of the vascular bead into mature, hierarchically organised network. Micro-MRI could be used for serial investigation in terms of flow measurements and detection of thrombosis. Discussion The presence of a vascular bed prior to cell transplantation might protect against hypoxia-induced cellular death, especially at central portions of the matrix, and therefore ensure physiological function of the device. The generation of vascularised bioartificial tissue substitutes might offer new modalities of surgical reconstruction for use in reparative medicine.