Laura Taylor, Leonard Jones, Mark H. Tuszynski, and Armin Blesch
Neurotrophic factors can stimulate the growth of axons after spinal cord injury. For example, when genetically modified cells expressing the neurotrophin NT-3 are grafted into the site of injury, axons grow into the lesion. However, these axons rarely exit the graft to innervate the adjoining spinal cord. This week, Taylor et al. tried to overcome this stumbling block to regeneration. They transplanted grafts of syngeneic marrow stromal cells overexpressing NT-3 into dorsal column lesions in the adult rat spinal cord; this fiber tract carries ascending sensory axons. The authors then injected lentiviral vectors expressing NT-3 at sites rostral to the graft, thus establishing an extended gradient of neurotrophic factor to guide axons growth. In injected animals, axons indeed bridged the gap and extended beyond the graft boundary but did not proceed further than 500 祄, although NT-3 gradients extended further. Thus, the growth pattern was not strictly "chemotropic."

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