UC San Diego

This thesis examined the hypothesis that axonal guidance could be improved in the central and peripheral nervous systems using a highly linearized templated agarose scaffold. In the present study we examined whether a templated agarose scaffold improved axon retention across a large central nervous system (CNS) lesion and how cellular and axonal orientation was affected within the scaffold channels. The "physical" guidance from the scaffold was applied to an existing CNS "chemical" guidance strategy, shown to promote axons beyond the lesion site, to enhance the number of crossing axons in larger, disorganized, lesions. Specifically, there was the greatest number of long-tract sensory axons reaching the distal aspect of the lesion when the templated agarose scaffold was combined with a neurotrophic source of NT-3 beyond the lesion site and a conditioning lesion, to enhance chemical axon guidance and the intrinsic growth state of axons, respectively. When comparing the scaffold implant to a cell suspension grafts, we found a higher retention of long-tract ascending (sensory) axons and descending (motor) axons crossing large lesions (2mm). The enhanced axon retention may be attributed to the finding that cellular orientation within the scaffold channels is highly linear, thus promoting a less tortuous environment for axon orientation and bridging. Although an enhanced number of axons were able to cross the lesion, the axons did not repenetrate the host tissue due to a reactive cell layer, present only in scaffold the implant groups. Additionally, a peripheral nerve conduit, with the agarose scaffold as the core, displayed biocompatiablility and supported axon growth and vasculature beyond the clinically applicable distance of 4mm. Thus, the templated agarose scaffold enhances axon retention and guidance within CNS injury sites and has potential applications to the PNS.