Altered Acidic and Basic Fibroblast Growth Factor Expression Following Spinal Cord Injury

In normal spinal cord, acidic fibroblast growth factor (aFGF) immunoreactivity was localized in the cytoplasm of ventral motor neurons and sensory fibers in the dorsal columns. Basic FGF (bFGF) immunoreactivity was restricted to astrocyte nuclei and the cytoplasm of a few neurons in the intermediate gray matter. Spinal cord lesions resulted in complete destruction of the dorsal columns at T8. Two days postlesion, aFGF immunoreactivity was increased in ventral motor neurons and was now seen in intermediate gray matter neurons. Acidic FGF was not detected in the lesioned fasciculus gracilis at T4-5, but markedly increased in the fasciculus cuneatus. At L1-2, aFGF-immunoreactive fibers in the fasciculus gracilis also increased. This aFGF immunostaining was maintained 5 and 12 days postlesion. A lesion-induced loss of aFGF immunoreactivity in the nucleus gracilis suggests that aFGF is anterogradely transported in ascending sensory fibers. Two days postlesion, glial fibrillary acidic protein immunoreactivity increased at the lesion site, as well as at T4-5 and L1-2, with no change in bFGF staining. Five days postlesion, increased bFGF immunoreactivity appeared at the edge of the cystic cavity and the dorsal columns at T4-5 in both the nucleus and the cytoplasm of reactive astrocytes, and was increased at 12 days postlesion. The differential cellular, temporal, and spatial expression of aFGF and bFGF following spinal cord lesion suggest they subserve distinct roles in the response to CNS injury.