Serum levels of tau protein increase according to the severity of the injury in DAI rat model

Traumatic brain injury (TBI) in the form of diffuse
axonal injury (DAI) is difficult to diagnose in the early
phase of the injury. Early diagnosis of DAI may provide
opportunity for developing treatment and management
strategies. Tau protein has been demonstrated to increase in the early
phase of TBI with high diagnostic accuracy in patients with DAI. We tested
the biological plausibility of tau protein using a rat DAI model by
evaluating the association between serum tau levels and the severity of
brain injury. DAI was induced in animals using the Marmarou
model. After a survival of 60 minutes, rats were anesthetized and
sacrificed after obtaining blood samples (5ml) from the heart.
Eighteen rats were employed in the
present study and were randomly subjected to sham-operated
control (n=4), mild DAI (n=7), and severe DAI (n=7). Of seven severe DAI
rats, two rats that had focal injury caused by skull fracture were
excluded in the measurement of tau protein level. The serum levels of tau
protein in the rat DAI model were found to increase significantly and
consistently according to the severity of the injury. Rats with
DAI showed significantly higher serum levels of tau protein compared to
sham rats; the severe DAI rats had higher levels of tau than moderate DAI
and sham rats (sham vs. mild, P=0.02; mild vs.
severe, P=0.02). In conclusion, serum tau protein levels may be
useful as a biomarker for diagnosing and estimating the severity of DAI in
the early phase.