Cell-Free DNA as a Marker for Prediction of Brain Damage in Traumatic Brain Injury in Rats

Abstract

Traumatic brain injury (TBI) is a major cause of morbidity and mortality, and early predictors of neurological outcomes are of great clinical importance. Cell free DNA (CFD), a biomarker used for the diagnosis and monitoring of several diseases, has been implicated as a possible prognostic indicator after TBI. The purpose of this study was to determine the pattern and timing of CFD levels after TBI, and whether a relationship exists between the level of CFD and brain edema and neurological outcomes. Thirty-nine Sprague-Dawley rats were randomly assigned to two groups: rats in group 1 (sham group) were anesthetized and had a scalp incision without TBI, and rats in group 2 were anesthetized and had a scalp incision with TBI, which was induced by using a weight drop model that causes diffuse brain injury. A neurological severity score (NSS) was assessed at 1, 24, and 48 h after TBI. CFD was measured via blood samples drawn at t=0 (baseline), 12, 24, 48, 72, and 120 h after TBI. At 48 h after TBI, brain edema was determined in a subgroup of 11 rats by calculating the difference between rats' wet and dry brain weight. The significance of comparisons between and within groups (CFD levels, brain water content, and NSS) were determined using the Kruskal-Wallis, Mann-Whitney and Student t test. The correlation between CFD levels and the NSS, as well as between CFD levels and the extent of brain edema, was calculated using the Spearman and Pearson tests, respectively. Compared with baseline levels, the CFD levels in rats subjected to TBI were significantly increased at 24 and 48 h after TBI (p<0.01 and p<0.05, respectively). A positive correlation was demonstrated between CFD levels 24 h following TBI and the extent of brain edema (r=0.63, p<0.05), as well as between CFD levels and the NSS (r=0.79, p<0.005). In this study, we demonstrated an increase in CFD levels after TBI, as well as a correlation between CFD levels and brain edema and NSS. CFD levels may provide a quick, reliable, and simple prognostic indicator of neurological outcome in animals after TBI. Its role in humans has not been clearly elucidated, but has potentially significant clinical implications.

Repeated Blast Exposures Cause Brain DNA Fragmentation in Mice

“…6,22 DNA fragmentation in the brain has also been reported after other forms of TBI, indicating that it may represent a shared final common pathophysiological mechanism of injury across a variety of brain insults. [12][13][14][15] The increased CFD observed in plasma after repeated blast exposures is also a somewhat novel finding. Increased plasma CFD has been reported after other forms of TBI as well as in patients with neurological abnormalities.…”

“…Increased plasma CFD has been reported after other forms of TBI as well as in patients with neurological abnormalities. 12,[14][15][16][17]19,20 The maximum level of circulating CFD was observed at 2 h and was still significantly elevated at 6 h after repeated blast exposures, likely indicating a slow clearance after a transient release of CFD into the circulation.…”

“…In addition to direct injury to the brain, BOP exposure also causes systemic injuries (e.g., to the lungs and liver), and the systemic factors released from these injured organs are reported to have a direct adverse effect on the traumatized brain and to aggravate ongoing pathophysiological processes. [9][10][11] Damage to DNA in the brain has been associated with the pathology of different forms of TBI [12][13][14][15][16] and neurodegenerative disorders, including Alzheimer's disease and Parkinson's disease. [17][18][19][20] Because DNA damage results in the release of cell-free DNA (CFD) from the brain, the levels of CFD in cerebrospinal fluid and plasma have been projected as sensitive markers for diagnosis and prognosis of TBI 12,14,15 and neurodegenerative disorders.…”

“…[9][10][11] Damage to DNA in the brain has been associated with the pathology of different forms of TBI [12][13][14][15][16] and neurodegenerative disorders, including Alzheimer's disease and Parkinson's disease. [17][18][19][20] Because DNA damage results in the release of cell-free DNA (CFD) from the brain, the levels of CFD in cerebrospinal fluid and plasma have been projected as sensitive markers for diagnosis and prognosis of TBI 12,14,15 and neurodegenerative disorders. 21 Lowlevel ( < 11.3 pounds per square inch [psi]) single BOP exposure using TNT in an open-field setting produced significant numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells, especially oligodendrocytes and astrocytes in cerebral white matter (WM) of rodents at 24 h postexposure, indicating potential DNA fragmentation.…”

A vision for ubiquitous sequencing

“…These molecules are released into the plasma due to various biological processes, including cancer, conferring a diagnostic vantage point without invasive biopsies (Van Der Vaart and Pretorius 2008). Multiple lines of evidence have shown that these nucleic acids can be used as biomarkers for a series of acute conditions, such as liver response to drug overdose (Wang et al 2009), heart attack (Creemers et al 2012), sepsis (Dwivedi et al 2012), and brain trauma (Ohayon et al 2012). Real-time bedside sequencing at relatively short intervals can serve as the basis for a universal apparatus to capture these biomarkers, adding a new layer of information to patient status.…”