Astrogliosis limits the integration of peripheral nerve grafts into the spinal cord

Segments of peripheral nerve were grafted into the site of a spinal cord transection in mice. To determine the relationship of spinal cord astrocytes to graft derived Schwann cells, graft sites were examined with immunohistochemical as well as conventional histological techniques. Myelin derived from Schwann cells, as identified by immunoreactivity to antibodies against its major protein PO, was strictly confined to the graft. Astrocytes and astrocytic filaments, identified by immunoreactivity to antibodies against glial fibrillary acidic protein (GFAP), predominated at the graft-spinal cord interface, bordering the most central penetration of Schwann cell myelin. Occasional GFAP-positive astrocytes were observed within the graft. It appears that astrocytes limit the penetration of Schwann cells from peripheral nerve grafts into the spinal cord.