A novel epineural tube implantation paradigm in the adult rat was designed for the analysis of regulatory cell interactions in peripheral nerves and for the development of therapeutic implants. The aim was to allow the integration of synthetic regenerative structures and cells into the nerve interior while preserving an outer nerve tissue layer with a supportive vasculature. The microsurgical technique allowed us to remove the interfascicular epineurium, leaving behind an epineural tube with an intact tissue wall of about 0.1-0.2mm. The resulting tube was filled with hundreds of bioengineered bands of Bungner which were composed of resorbable polymer filaments seeded with Schwann cells. Alternatively, purified cells to be analyzed or different types of growth matrices were injected into the epineural tube. Such manipulations will allow to generate and investigate concentration gradients of biological factors or to analyse cell-matrix interactions under defined conditions in a supportive in vivo environment. Our current aim is to evaluate bioengineered neural implants. In summary, a microsurgical in vivo paradigm has been developed to address multiple aspects of peripheral nerve regeneration.