Changes in the blood-CSF barrier in experimental traumatic brain injury

Elevation of intracranial pressure (ICP) is a major complication of traumatic brain injury (TBI), and cerebrospinal fluid (CSF) volume is a key factor in ICP regulation. Choroidal epithelial cells (CEC) form the blood-CSF barrier and their integrity is essential for controlling CSF production. In the current study, the morphology of the CEC was studied from 5 h to 28 day after TBI in the rat.

Male Sprague-Dawley rats were subjected to severe TBI using the impact-acceleration model, and the ultrastructure of the CEC was studied using transmission (TEM) and scanning (SEM) electron microscopy.

Radical ultrastructural changes were seen by TEM in CEC in injured animals. At 5 h post-injury cell swelling and incipient cytoplasmic vacuoles were seen. At 24 h most severe changes were noted with extensive widening of intercellular clefts. At 7 day and 14 day post-injury, increased cytoplasmic electron density was evident. At 21 day, most microvilli had bulbous ends, and at 28 day cytoplasmic vacuoles were numerous with widened intercellular clefts. SEM revealed a continuum of changes in all injured animals and most conspicuous was the heterogeneity of surface features, with most cells showing bulbous and cup-shaped microvilli, burr-like processes and pits. Epiplexus cells were hypertrophic and more numerous.

At 4 weeks after trauma, choroidal epithelial cells continued to show morphological alterations suggesting that brain homeostasis was still not restored.