In order to study the 'in vivo' regenerative capacity of the central nervous system, a semipermeable tube was placed in the axis of the lesioned nigrostriatal pathway of adult rats. In spite of a correct positioning of the tube, no growing central nervous processes were observed within the tube after 3 to 6 weeks when it was left empty. However, when the lumen of the tube was previously filled with a pre-degenerated sciatic nerve, unmyelinated and myelinated fibers were observed growing in the peripheral graft. Since the content of the tube can be modified, it appears that this model can be used to test the capability of cellular or acellular microenvironments to promote the 'in vivo' regeneration of the mammalian central nervous system fibers.
Knoops, B., & van den Bosch de Aguilar, P. (1987). A new in vivo model to study the influence of the microenvironment in the regeneration of the central nervous system. Brain research, 425(1), 191-197. https://doi.org/10.1016/0006-8993(87)90500-2 (Original work published 1987)