Adenovirus-mediated transfer and expression of β-Gal in injured hippocampus after traumatic brain injury in mice

In models of focal cerebral ischemia, adenoviral gene transfer is often attenuated or delayed versus naive. After controlled cortical impact (CCI)-induced traumatic brain injury in mice, CA1 and CA3 hippocampus exhibit delayed neuronal death by 3 days, with subsequent near complete loss of hippocampus by 21 days. We hypothesized that adenoviral-mediated expression of the reporter gene β-Galactosidase (β-Gal) in hippocampus would be attenuated after CCI in mice. C57BL6 mice (n = 16) were subjected to either CCI to left parietal cortex or sham (burr hole). Adenovirus carrying the β-Gal gene (AdlacZ; 1 x 10)⁹ plaque-forming units [pfu]/mL) was then injected into left dorsal hippocampus. At 24 or 72 h, β-Gal expression was quantified (mU/mg protein). Separate mice (n = 10) were used to study β-Gal spatial distribution in brain sections. β-Gal expression in left hippocampus was similar in shams at 24 h (48.4 ± 4.1) versus 72 h (68.8 ± 8.8, not significant). CCI did not reduce β-Gal expression in left hippocampus (68.8 ± 8.8 versus 88.1 ± 7.0 at 72 h, sham versus CCI, not significant). In contrast, CCI reduced β-Gal expression in right (contralateral) hippocampus versus sham (p < 0.05 at both 24 and 72 h). β-Gal was seen in many cell types in ipsilateral hippocampus, including CA3 neurons. Despite eventual loss of ipsilateral hippocampus, adenovirus-mediated gene transfer was surprisingly robust early after CCI providing an opportunity to test novel genes targeting delayed hippocampal neuronal death.