Transplantation of purified populations of Schwann cells into lesioned adult rat spinal cord

Both peripheral nerve and purified populations of Schwann cells promote axonal regeneration in the peripheral and central nervous systems. In order to assess whether Schwann cells can provide a bridge enabling regrowth of descending and ascending axons across an area of injury in adult spinal cord, Schwann cells enclosed within a collagen scroll were transplanted into lesions created photochemically. Numerous myelinated and unmyelinated axons were found throughout 28-90 day implants; Schwann cells myelinated or ensheathed the ingrowing axons normally. In contrast, acellular collagen grafts did not contain axons. Thus, Schwann cells stimulated abundant growth of axons into the grafts. In part to address the concern that the dense collagen layer acted as a barrier, we assessed transplantation of Schwann cells, inside semi-permeable polyacrylonitrile/polyvinylchloride (PAN/PVC) guidance channels, after transection of adult inbred rat spinal cords at T8 with removal of the the T9-11 segments. One month after grafting, a vascularized tissue cable was present with more myelinated and unmyelinated axons in the Schwann cell seeded channels than controls. Supraspinal axons did not invade the channel; some were of peripheral origin and others were spinal cord interneurons found up to nine segments away from the graft. When both cut ends of the cord were from inserted into Schwann cell filled channels, a vascularized tissue cable bridged the ends of the spinal cord, containing numerous myelinated axons and more unmyelinated axons, originating from spinal grey matter and dorsal root ganglion neurons.