Tiam Mana Saffari

37 THE ROLE OF VASCULARIZATION IN NERVE REGENERATION 2 regeneration 29 . Thus, vascularity would accelerate revascularization compared to non-vascularized nerve grafts (NVNG) 30,31 . A well vascularized bed does not only decrease fibroblast infiltration, but also provides an optimal nutritional environment 30 . In a scarred, non-vascularized wound bed model, increase in myelination has been found when providing vascularization 32,33 . However, no differences were found in nerve conduction velocity 34 . When intraneural blood supply is limited, the fibroblasts replace the Schwann cells, causing a fibrotic distal nerve and scarred endoneurial tube 28 . In normal, vascularized beds, reported results have been conflicting. Some studies found no differences between VNGs and NVNGs 35-37 in rat models, while in rabbit models increased remyelination and enhanced contraction force have been reported in VNGs 38,39 . These results may be explained by the length of the gap and regeneration process in these animal models. The rat model could be used as a bioassay to evaluate treatments but translation to larger animals may be complicated as differences may occur due to the small gap (<11 mm) and superlative regeneration rate in rats 40 . Other studies have focused on VEGF administration to the nerve site to enhance vessel formation and thus nerve regeneration and subsequently motor recovery 7,8 . It has been demonstrated that VEGF increases revascularization 7,8 , however, the application of VEGF did not improve functional motor nerve recovery in the long term 7 . It is assumed that producing a supportive microenvironment after nerve injury including stable blood supply may have more effect than the application of VEGF alone. A vascularized fascial flap containing adipose tissue and a vascular bundle has been suggested to improve revascularization through the excreted angiogenic factors, provided by the stem cells in the adipose tissue as well as the blood supply and environmental support. The application of the superficial inferior epigastric artery fascial (SIEF) flap to provide vascularization to the nerve graft site in an experimental model has been described 41 and found to increase revascularization of transplanted nerve allografts 27 (Figure 2). However, further animal studies are required to determine its role in nerve reconstruction.