INFLUENCE OF IN-1 ANTIBODY AND ACIDIC FGF-FIBRIN GLUE ON THE RESPONSEOF INJURED CORTICOSPINAL TRACT AXONS TO HUMAN SCHWANN-CELL GRAFTS

Two strategies have been shown by others to improve CST regeneration f ollowing thoracic spinal cord injury: 1) the administration of a monoc lonal antibody, IN-1, raised against a myelin-associated, neurite grow th inhibitory protein, and 2) the delivery of acidic fibroblast growth factor (aFGF) in fibrin glue in association with peripheral nerve gra fts. Because autologous transplantation of human Schwann cells (SCs) i s a potential strategy for CNS repair, we evaluated the ability of the se two molecular agents to induce CST regeneration into human SC graft s placed to span a midthoracic spinal cord transection in the adult nu de rat, a xenograft tolerant strain. IN-1 or control (HRP) antibodies were delivered to the injury/graft region by encapsulated hybridoma ce lls (''IN-1 ravioli'') or daily infusion of hybridoma culture supernat ant; dFGF-fibrin glue was placed in the same region in other animals. Anterograde tracing from the motor cortex using the dextran amine trac ers, Fluororuby (FR) and biotinylated dextran amine (BDA), was perform ed. Thirty-five days after grafting, the CST response was evaluated qu alitatively by looking for regenerated CST fibers in or beyond grafts and quantitatively by constructing camera lucida composites to determi ne the sprouting index (SI), the position of the maximum termination d ensity (MTD) rostral to the GFAP-defined host/graft interface, and the longitudinal spread (LS) of bulbous end terminals. The latter two mea sures provided information about axonal die-back. In control animals ( graft only), the CST did not enter the SC graft and underwent axonal d ie-back [SI = 1.4 +/- 0.1, MTD = 2.0 +/- 0.2, LS = 1.3 +/- 0.3, (n = 3 )]. Results of IN-1 delivery from ravioli did not differ from controls , bat injections of IN-1-containing supernatant resulted in a signific ant degree of sprouting but did not prevent axonal die-back [SI = 1.9 +/- 0.1, MTD = 1.5 +/- 0.2, LS = 1.1 +/- 0.1, (n = 7)] and traced fibe rs did not enter grafts. Acidic FGF dramatically reduced axonal die-ba ck and caused sprouting [SI = 2.0 +/- 0.1 (n = 5), MTD = 0.5 +/- 0.04 (n = 6), LS = 0.4 +/- 0.1 (n = 6)]. Same traced fibers entered SC graf ts and in 2/6 cases entered the distal interface. We conclude that 1) human SC grafts alone do not support the regeneration of injured CST f ibers and do not prevent die-back, 2) grafts plus IN-1 antibody-contai ning supernatant support some sprouting but die-back continues, and 3) grafts piles aFGF-fibrin glue support regeneration of some fibers int o the grafts and reduce die-back. (C) 1997 Wiley-Liss, Inc.