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

Abstract

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