Neuronal and glial apoptosis in human traumatic brain injury

To establish reliable methods to aid the timing of brain damage after traumatic brain injury (TBI), brain tissue from 56 autopsy cases with TBI and known survival times, ranging from a few minutes to 126 days, were tested for apoptotic changes to the neuronal and glial cells. Apoptosis was established using the TdT-mediated dUTP nick end labelling (TUNEL) method of in-situ labelling and immunohistochemical reaction of caspase 3. In addition, cellular reaction and astroglial cell differentiation were investigated using histological and immunohistochemical markers. From a survival time of 120 min up to 12 days, TUNEL-positive apoptotic neuronal cells were frequently detected in the contusion zone. The earliest positive caspase 3 reaction in cortical neurons was evident after a posttraumatic interval of 80 min. Detection of apoptotic glial cells using the TUNEL technique showed that as in the case of neuronal cells, the earliest positive TUNEL reaction was obtained after 110 min. In cases of survival times of 120 min up to 4 days, apoptotic glial cells could frequently be detected. However, the first caspase 3-positive glial cells appeared 5 h after injury. Cerebral apoptosis was significantly associated with TBI cases as compared to control cases (P<0.001). The reference histological findings of neutrophilic granulocytes, CD3-positive T-lymphocytes, CD68-positive activated microglial cells/macrophages and TUNEL-positive neuronal cells increases the degree of certainty in determining the probable age of traumatic brain injury to 87.5%.