Ultrastructural Characterization of a Regular Schwann-Axon-Islet Complex after the Autograft of Pancreatic Fragments into the Spleen of the Adult Dog

Abstract

After autotransplantation of pancreatic fragments into the dog's spleen, the morphogenesis of the reinnervating process has evolved as an highly differentiated model, reproducing the most peculiar and systematic relationships between Schwann cells, axons, and islet cells reported in the dog's islet, despite it's modulation by the restrictive conditions derived from the intrasplenic location of the dispersed pancreatic tissue. The reinnervating process is described, emphasizing the peculiar ultrastructural features and topography of the Schwann cells and of the axonal network that impose the concept of a true anatomical reinnervation, which make previsible the possibility of a very selective and direct neurochemical and/or electrotonic control of the engrafted islet cells. The schwann-axon-islet complexes are a very peculiar and regular arrangement between islet cells and nervous elements and are reproduced after the autotransplant without the engrafted ganglia, whose potential but aleatory contribution could not be unequivocally characterized. Axonal profiles or Schwann cells on the abundant regenerated ductal-acinar structures were not identified.