Upregulation of amyloid precursor protein and its mRNA in an experimental model of paediatric head injury

Amyloid precursor protein (APP), a membrane spanning glycoprotein which plays an important role in neuronal growth and synaptic plasticity, is increased after traumatic brain injury (TBI) and has been used as a sensitive marker of neuronal damage in an adult sheep head impact model. We hypothesised that APP expression would similarly be increased in lambs, suggesting that in the immature injured brain APP is also upregulated as an acute phase response to trauma. Ten anaesthetised and ventilated 4-5 week old Merino lambs sustained a left temporal head impact from a humane stunner. At 2 h after impact, there was widespread and intense neuronal cell body APP immunoreactivity which was more widely distributed than axonal APP. APP messenger RNA (mRNA) expression was also markedly increased with a distribution similar to that of APP antigen. These results demonstrate that APP antigen and mRNA are sensitive early indicators of TBI in paediatric cases.