Collagen nerve guide tubes in the rat septohippocampal pathway

Synthetic porous collagen tubes were implanted into the rat fimbria in order to determine whether such prostheses will permit axonal growth in the mature mammalian central nervous system (CNS). The tubes were found to slowly degrade over 4 weeks. In the majority of cases a distinct tissue core occupied the lumen of the tube and extended from the rostral (septal) end to the caudal (hippocampal) end. The core consisted of cellular aggregates of various cell types and blood vessels. In addition, the presence of axons within the tube lumen was demonstrated at both light and electron microscopic levels. Fibers within the tubes were visualized with noradrenergic histofluorescence and with neurofilament immunohistochemistry. Pretreatment of the tubes with nerve growth factor (NGF) resulted in circumferential disposition of the tissue core and an increase in acetylcholinesterase activity associated with the tube but no obvious change in axonal regeneration. No evidence was obtained for reinnervation of the hippocampal formation by cholinergic or noradrenergic fibers. These results indicate that porous collagen tubes will persist for several weeks within the mature rat CNS and can support axonal growth.