Vimentin and GFAP responses in astrocytes after contusion trauma to the murine brain

Abstract

Astroglial responses after traumatic brain injury are difficult to detect with routine morphological methods. The aims for this study were to compare the temporal and spatial expression pattern of vimentin- and glial fibrillary acidic protein (GFAP) in a weight drop model of mild cerebral contusion injury in the rat. We also wanted to study the vimentin response with immunohistochemistry and vimentin mRNA RT-PCR analysis in severe cortical contusion injury produced by the controlled cortical impact in the mouse. Vimentin and GFAP immunohistochemistry (1 day, 3 days and 7 days) combined with vimentin mRNA RT-PCR analysis (1 h, 4 h, 22 h, 3 days and 7 days) were used after experimental traumatic brain injury in the rat and mouse. Increases in post-traumatic vimentin mRNA levels in the cortex and in the hippocampus appeared together with vimentin immunoreactivity in astrocytes in the perimeter of the cortical lesion, in the subcortical white matter and in the hippocampus starting at one day after severe trauma. GFAP immunostaining revealed hypertrophic astrocytes peaking at day 3 in the perifocal cortical region. There was no significant increase in GFAP immunoreactivity in the white matter in the rat. However, in the mouse there was a slight increase in the number of GFAP positive cells in this region, 3 days after trauma. Overall the pattern of vimentin immunoreactivity was very similar in the rat and mouse. Vimentin immunoreactivity was more sensitive than the GFAP staining method to demonstrate the distribution and time course of astrocyte reactions after a contusion injury, especially in the white matter distant from the cortical lesion.