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Objective:
Brain tissue oxygenation (PbtO
2
) monitoring has been
utilized in the severe traumatic brain injury (sTBI) population as an
in vivo
tool to detect oxygenation changes in the acute recovery phase.
It has been previously reported that the longer the time a patient
experiences a PbtO
2
of
£
15 torr, the greater the likelihood of death.
The purpose of this study is to assess PbtO
2
values and its relationship
to hypoxia responsive gene expression.
Methods:
Age, gender and initial Glasgow Coma Scale (GCS)
score matched cohorts (PbtO
2
<
15 mmHg and PbtO
2
‡
30 mmHg) of
severe TBI patients (n
=
20) were assessed. Post-trauma day 1 blood
samples were collected via Paxgene tubes and processed for gene
expression utilizing the Ilumina Human HT12 expression BeadChip
technology. For the comparison of low PbtO
2
vs high PbtO
2
, differ-
entially expressed genes were identified using data analysis methods
selected by efficiency analysis (EA) using Auto AE software. Raw
expression values were normalized through the Gene Expression Data
Analysis (GEDA) tool and the J5 test was used at a threshold of 33 to
identify differently expressed genes.
Results:
Post-trauma day 1 gene expression was significantly
higher in the low PbtO
2
cohort for neonatal hemoglobin, gamma G
(HBG2) and gamma A (HGB1), and ferritin ( J5 values 164.1, 128.3
and 45.5 respectively) and also hypoxia-responsive genes associated
with hypoxia inducible factor (HIF-1
a
), S100A4 and annexin A1( J5
values 45.3 and 14.72, respectively).
Conclusion:
Increased gene expression for higher-affinity fetal
hemoglobin, increased iron storage and hypoxia-responsive genes
occurred in a low brain oxygenation state following TBI. With ad-
ditional study, these pathways may represent a therapeutic avenue to
treat brain hypoxia in the injured brain.
Keywords: traumatic brain injury, hypoxia, brain tissue oxygena-
tion, fetal hemoglobin
C2-08
GENOME-WIDE CHANGES IN GENE EXPRESSION FOL-
LOWING SPORTS-RELATED CONCUSSION
Kian Merchant-Borna
1
, Jeffrey Bazarian
1
, Hyunhwa Lee
2
, Jessica
Gill
3
1
University of Rochester Medical Center, Emergency Medicine, Ro-
chester, USA
2
University of Nevada, School of Nursing, Las Vegas, USA
3
National Institutes of Health, National Institute for Nursing Re-
search, Bethesda, USA
Objective:
To determine changes in global gene expression (GE)
following sport-related concussion (SRC).
Methods:
From 2010–2012, 253 NCAA collegiate contact ath-
letes from two universities in Rochester, New York, underwent
collection of peripheral blood mononuclear cells (PBMC) at the start
of the sport season (baseline). Sixteen athletes who subsequently
developed a SRC, along with 16 non-concussed teammates who
served as controls, underwent repeat collection of PBMC within 6
hours of injury (acutely). Concussed athletes underwent additional
PBMC collection at 7 days post-injury (sub-acutely). PBMC mRNA
expression at baseline was compared to mRNA expression acutely
and sub-acutely post-SRC. Ingenuity Pathway Analysis was used to
translate differential GE into gene networks most likely affected by
SRC. Clinical recovery was determined by examining changes in
post-concussive symptoms, postural stability, and cognition from
baseline to the sub-acute timepoint.
Results:
Athletes with SRC had significant changes in mRNA
expression at both the acute and sub-acute timepoints compared to
their baseline profiles. There were no significant GE changes among
uninjured teammate control athletes. Acute transcriptional changes
centered on inflammatory activity with key transcriptional hubs
being interleukins 6 and 12, toll-like receptor 4, and NF-
j
B. Sub-
acute GE changes centered on glucocorticoid receptor signaling
with NF-
j
B, follicle stimulating hormone, chorionic gonadotropin,
and protein kinase catalytic subunit being the key transcriptional
hubs. All concussed athletes were recovered by the sub-acute
timepoint.
Conclusion:
Acute post-SRC gene transcriptional changes reflect
regulation of the innate immune response as well as the transition to
an acquired, adaptive immune response. By 7 days post-injury, tran-
scriptional activity is centered on the regulation of the hypothalamic-
pituitary-adrenal axis. These findings illustrate a time-dependent shift
in GE post-injury that may provide insight into the pathophysiology of
recovery from SRC and suggest putative targets for therapeutic in-
tervention.
Keywords: gene expression, concussion, sports, clinical research
C2-09
PATHWAY ANALYSIS OF LONG TERM GENOMIC CHAN-
GES AFTER EXPERIMENTAL TBI
Harris Weisz
, Deborah Boone, Donald Prough, Douglas DeWitt,
Helen Hellmich
University of Texas Medical Branch, Department of Anesthesiology,
Galveston, USA
Background:
Despite expansive literature on the acute effects of
traumatic brain injury (TBI), much less is known about the causal
injury mechanisms that trigger chronic neurodegenerative changes.
Here, we examined genomic changes that persist from 24 hours up to
3 months after TBI, and test our hypothesis that a core set of dysre-
gulated genes/pathways could be associated with long-term neuro-
degeneration.
Methods:
Male, Sprague-Dawley rats (300–350 g) were anesthe-
tized (isoflurane), subjected to moderate fluid percussion TBI, and
survived 24 hr or 3 months. Sham animals received the same anes-
thetic regimen, surgical preparation, and survival time points, but no
injury. Hippocampal regions were microdissected and sent to GenUs
BioSystems for genome-wide microarray analysis (Agilent Rat GE
8x60K arrays). Quantitative real-time PCR, using individual Taqman
assays, was performed to validate selected gene expression changes in
pathways activated/inhibited by TBI.
Results:
24 h post-injury, 554 genes (p
£
0.05, fold-change
‡
1.5) on
the microarray were differentially expressed, compared to sham in-
jured control samples. At 3 months, 83 genes (p
£
0.05, fold-
change
‡
1.5) were differentially expressed. Using gene expression
analysis tools in Ingenuity Pathway Analysis software, we constructed
causal and network interactions among the differentially expressed
genes, which allowed us to infer the effects of TBI on critical cell
signaling pathways. Genes commonly found dysregulated after TBI
acutely (24 h) and chronically (3 months) are members of cell sig-
naling pathways that are critical for cell survival/death (PI3K sig-
naling), neurodegeneration (RHOGDI), inflammation (acute phase
response), and immune response (complement system activation).
Conclusion:
These data support our hypothesis that chronic neu-
rodegeneration may be linked to the persistent (up to 3 month) ex-
pression of critical hub genes that are important for cell survival/
death. Understanding the molecular mechanisms underlying chronic
neurodegenerative processes will enable the development of targeted
therapies for TBI and aid in characterizing biomarkers for diagnosis.
A-79