Release of extracellular matrix components after human traumatic brain injury

Most research on the evolution of damage after traumatic brain injury (TBI) focuses on cellular effects, but the analysis of human tissue slices and animal research have shown that TBI causes concomitant damage in the extracellular matrix, which can play a significant role in both short-term consequences such as edema, and late effects such as post-traumatic epilepsy (PTE). To test the hypothesis that traumatic brain injury (TBI) in human patients causes disruption of sulfated glycosaminoglycan (sGAG) in the extracellular matrix, we measured levels of these substances in the ventricular cerebrospinal fluid (CSF) in patients with severe TBI in the acute post-injury period, along with concomitant levels in blood and urine. We assessed whether levels corresponded to parenchymal injury load, distance of traumatic brain lesions from the ventricle, presence of polytrauma, or host demographic factors.MethodsSamples of CSF, blood, and urine were obtained within 72 hours of injury in patients who received external ventricular drains as part of their treatment of severe TBI, and levels of chondroitin and heparan sGAGs were measured, along with their disaccharide constituents. Basic demographic information, presence and severity of polytrauma, brain injury load based on imaging findings, and distance of radiologically visible parenchymal injury from the ventricle were analyzed for correlation with total subtype sGAG levels in each patient.ResultsLevels were measured in 14 patients ranging in age from 17-90 years. CSF sGAG levels were variable among patients, and sGAG levels were higher in plasma than in CSF and variable in urine. Patients with polytrauma had non-significantly higher blood sGAG compared to patients with isolated head injury. Subcategories of CSF sGAG levels correlated with distance from the ventricle of parenchymal injury but not with brain injury load, which may reflect rapid metabolism in the parenchyma, contamination by blood, or bulk directional CSF flow from the ventricle to the subarachnoid space.ConclusionThis study is the first to measure sGAG levels in ventricular CSF and also provides the first measurements in patients with TBI. Damage to the extracellular matrix may play a major role in acute and chronic injury sequelae, and these data demonstrate elevation locally of intracranial sGAGS after severe TBI and also suggest rapid local metabolism of these breakdown products. The consequences of extracellular matrix breakdown may provide unique therapeutic and preventive avenues to mitigate post-injury sequelae.