Increase in TNFalpha transport after SCI is specific for time, region, and type of lesion

The dynamic changes of the blood-brain barrier and blood-spinal cord barrier (BBB) are an important part of the CNS response to injury. This study addresses the permeability of the BBB in the acute phase of spinal cord injury (SCI) to the thoracic region. SCI by compression or by complete transection was generated in mice. BBB disruption was evaluated by spinal cord uptake of radiolabeled albumin. The BBB of the thoracic spinal cord was disrupted immediately after compression injury, lasting for 2 days. This was followed by a delayed permeability increase in the cervical spinal cord beginning 3 days after injury. After transection, BBB disruption was limited to the thoracic spinal cord and was present only immediately postinjury. The entry of TNFalpha not only was increased at the time of BBB disruption, following the same pattern, but also had secondary changes after the BBB permeability to albumin had returned to normal. The increase of TNFalpha entry, best explained by upregulation of the specific transport system for TNFalpha, was pronounced in the lumbar spinal cord as well as the thoracic region, and followed a different time course after the two types of injury. Integrating our results with those of the literature regarding the roles of inflammatory responses and the effects of TNFalpha in spinal cord regeneration, we conclude that the time-, region-, and lesion-specificity of the upregulation of TNFalpha transport is part of the regulatory changes at the BBB in response to SCI.