NeurorehabiIitation and Neural Repair 2000;14:265-275 © 2000Demos Medical Publishing Review Article Neurotrophic Factors and Gene Therapy in Spinal Cord Injury

Although it was once thought that the central nervous system (CNS) of mam-mals was incapable of substantial recovery from injury, it is now clear that the adult CNS remains responsive to various substances that can promote cell survival and stim-ulate axonal growth. Among these substances are growth factors, including the neu-rotrophins and cyroklnes, and growth-supportive cells such as Schwarm cells, olfac-tory ensheathing glia, and stem cells. We review the effects of these substances on promoting axonal growth after spinal cord injury, placing particular emphasis on the genetic delivery of nervous system growth factors to specific sites of injury as a means of promoting axonal growth and, in limited instances, functional recovery.Key Words: Central nervous system-Cytokinc-Neurotrophin-Stem cell-Regeneration. There are an estimated 150,000-250,000 individu-als with spinal cord injuries in the United States, and ap-proximately 10,000 new injuries occur annually{I, 2). Little Spontaneous improvement in function occurs after spinal cord injury (SCI), resulting in significant long-term disability. Thus, the need for promoting recovery after SCI is substantial. Spinal cord injury causes both direct damage to cell bodies and interruption ofaxons that pass through the injury site. Clearly, the majority of functional deficits re-sulting from SCI in humans are due to damage to the ap-proximately 2 million axons passing through the injury site. Yet careful analysis of injured spinal cords in ani-mal models and humans has demonstrated that tran-sected axons remain in close proximity to the injured site for protracted periods (3), providing an opportunity po-tentially to promote the regrowth of lesioned axons