Brain-derived neurotrophic factor in astrocytes, oligodendrocytes, and microglia/macrophages after spinal cord injury

Recent studies suggest that the injured adult spinal cord responds to brain -derived neurotrophic factor (BDNF) and neurotrophin-3 (NT3) with enhanced neuron survival and axon regeneration. Potential neurotrophin sources and c ellular localization in spinal cord are largely undefined. We examined glia l BDNF localization in normal cord and its temporospatial distribution afte r injury in viva We used dual immunolabeling for BDNF and glial fibrillary acidic protein (GFAP) in astrocytes, adenomatous polyposis coli tumor suppr essor protein (APC) for oligodendrocytes or type III CDH receptor (OX42) fo r microglia/macrophages. In normal cord, small subsets of astrocytes and mi croglia/macrophages and most oligodendrocytes exhibited BDNF-immunoreactivi ty. Following injury, the number of BDNF-immunopositive astrocytes and micr oglia/macrophages increased dramatically at the injury site over time. Most oligodendrocytes contained BDNF 1 day and 1 week following injury, but APC -positive cells were largely absent at the injury site 6 weeks postinjury. Glial BDNF-immunolabeling was also examined 10 and 20 mm from the wound. Te n millimeters from the lesion, astrocyte and microglia/macrophage BDNF-immu nolabeling resembled that at the injury at all times examined. Twenty milli meters from injury, BDNF localization in all three glial subtypes resembled controls, regardless of time postlesion. Our findings suggest that in norm al adult cord, astrocytes, oligodendrocytes, and microglia/macrophages play roles in local trophin availability and in trophin-mediated injury and hea ling responses directly within and surrounding the wound site. (C) 2000 Aca demic Press.