Expression of glia maturation factor beta after cryogenic brain injury

Glia maturation factor beta (GMFB) was identified as a growth and differentiation factor acting on neurons as well as glia. We investigated the expression of GMFB during 56 days after cryogenic brain injury, using immunohistochemistry, reverse transcriptase polymerase chain reaction (RT-PCR), Western blotting and enzyme immunoassay. Immunohistochemical analysis demonstrated that the GFAP-positive astrocytes around the lesion expressed GMFB protein, peaking 14 days after injury. Weak astrocytic expression of GMFB-immunoreactivity was seen in sham-operated animal brains. Cryogenic injury (CI) induced GMFB mRNA in the lesioned side after 7 days with a maximum at 14 days. Western blotting revealed the induction of GMFB protein starting 1 day after injury, and continuing until 14 days after injury. In the enzyme immunoassay, GMFB protein concentration peaked 14 days after injury in extracts from the injured side of the brain, whereas in serum it peaked 1 day after injury. These data indicate that the expression of GMFB increased in the astrocytes around the lesioned area after cortical cryogenic brain injury. These findings may provide new insight into GMFB function in pathological conditions following brain injury.