The Axonal Regeneration Across a Honeycomb Collagen Sponge Applied to the Transected Spinal Cord

We developed a honeycomb-shaped lyophilizedType I atelocollagen (Honeycomb Collagen: HC)with different pore sizes, and the effectiveness ofthe honeycomb shape on nerve regeneration wasexamined. We analyzed neurite outgrowth of dorsalroot ganglion (DRG) explants on HC, both in vitroand, with direct implantation of HC into thedefects of adult rat spinal cords, in vivo. The neuritesof DRGs on HC extended linearly through thepores. HC with a 400 Òm-pore size enhanced neuriteextension, and YIGSR laminin peptide coatingto the HC extended more neurites than fibronectincoating. The HC scaffolds coated with YIGSRwere implanted into 2 mm-defects of spinal cords atthe level of T8-9. Four weeks after implantation, theimplants had degraded and been replaced withself-tissues, repairing the injured site.Neurofilament-positive fibers were observed inthe implantation area and passed the bordersbetween the HC and spinal cord stumps.Functionally, a motor-evoked potential wasobserved in the quadriceps femoris muscle 10weeks after implantation. The electrophysiologicalexamination showed reconstruction of axontracts over the implant. This result indicates thatour developed honeycomb shape is advantageousfor host spinal cord compared to the randompored sponge shape, and that it promotes axonalregeneration after spinal cord injury.