Page 150 - NNS 2014 Program & Abstract Book

D2-14
PENETRATING BALLISTIC-LIKE BRAIN INJURY PRO-
MOTES TIME-DEPENDENT CELL PROLIFERATION IN
ADULT RAT HIPPOCAMPUS
Deng-Bryant, Y., Leung, L.Y., Tortella, F.C., Shear, D.A.
Walter Reed Army Institute of Research, Silver Spring, USA
Research has shown that the adult hippocampus retains the ability to
produce neural precursor cells and replace lost cells in response to
brain injuries. The current study examined the time course of pene-
trating ballistic-like brain injury (PBBI)-induced cell proliferation in
adult rat hippocampus. Unilateral frontal PBBI (10% injury severity)
or craniotomy (sham control) was performed on isoflurane anesthe-
tized Sprague-Dawley rats. To evaluate cell proliferation at specific
post-injury time points, BrdU (50 mg/kg x 3 i.p. injections delivered at
4 h-intervals) was initiated at 24 h prior to each experimental end-
point. At 24 h, 48 h, 72 h and 7 days post-injury rats were perfused
and brains were processed for fluorescence immunostaining for BrdU,
GFAP and Iba1. Minimal levels of BrdU-positive cells were detected
in the brains of sham controls, and at 24 h and 7 days post-PBBI.
However, a dramatic increase of BrdU-labeled cells was detected at
48 h and 72 h post-PBBI in ipsilateral and contralateral hippocampal
dentate gyri (DG). Further analysis was conducted to evaluate the
spatial distribution of BrdU-positive cells in hippocampal DG at 48 h
and 72 h post-PBBI. The results indicate that the majority of the
BrdU-positive cells were located throughout molecular layer and hilus
in the DG, accompanied by a few BrdU-positive cells scattered in the
subgranular zone where neural stem cells reside. Molecular layer and
hilus in the DG are regions where gliogenesis mainly occurs and
therefore, the majority of the BrdU-labeled cells observed in the
current study are potentially gliogenic. To confirm this, additional
cellular markers for astrocyte (i.e. GFAP) and microglia (i.e. Iba1)
were used to confirm the phenotype of these newly generated cells
following PBBI. BrdU-positive cells were primarily co-labeled with
Iba1, and to a lesser extent, with GFAP, suggesting that they are
proliferating microglia and astrocytes. Overall, the robust upregula-
tion of glial proliferation during acute phases after PBBI may reflect
an increasingly unfavorable environment for newborn neurons, po-
tentially leading to further cell loss.
Key words
cell proliferation, gliogenesis, hippocampus
D2-15
COMPREHENSIVE EVALUATION OF CHRONIC SPATIAL
LEARNING AND WORKING MEMORY DEFICITS FOL-
LOWING CLOSED-HEAD CONCUSSIVE INJURY IN RATS
Deng-Bryant, Y., Leung, L.Y., Flerlage, W.J., Winter, M., Yang, W.,
Tortella, F.C., Shear, D.A.
Walter Reed Army Institute of Research, Silver Spring, USA
This study was designed to identify optimal Morris water maze
(MWM) paradigms for evaluating cognitive abnormalities following
closed-head concussion leading to mild traumatic brain injury
(mTBI). For this purpose, all rats were exposed to a series of MWM
tasks designed to assess: (1) spatial reference memory using a spatial
learning task to find the hidden platform (two trials/day for 4 con-
secutive days), (2) memory retention using a missing platform (probe)
trial, (3) working memory using a delayed matching-to-place task (2
pairs of trials). Adult Sprague-Dawley rats received either anesthesia
(sham) or repeated projectile concussive impact (rPCI; 4 consecutive
PCIs at 1 hr interval). At 1 month post-injury, results of the spatial
learning task showed that the average latencies to locate the hidden
‘‘escape’’ platform were significantly longer in rPCI rats over the last
two days of the MWM testing compared to sham controls (p < 0.05).
In the memory retention task, rPCI rats also spent significantly less
time in the platform zone searching for the missing platform during
the probe trial (p < 0.05). On the working memory task, rPCI-injured
animals showed a trend toward worse performance, but this failed to
reach statistical significance compared to sham controls (p = 0.07). At
6 months post-injury, no differences were detected between rPCI and
sham controls on either the spatial learning or probe trials. However,
rPCI rats exhibited significantly worsened working memory perfor-
mance compared to sham controls (p < 0.05). Overall, the results in-
dicate that the MWM is capable of detecting cognitive deficits
following mTBI and thus may be useful in assessing the effects of
single vs. repeated injuries induced at varied intervals in the PCI
model. Furthermore, the results show that rPCI produced significant
cognitive deficits in both spatial learning abilities and in working
memory abilities in a time-dependent fashion that may be indicative
of progressive pathology and warrant further investigation. Funded by
CDMRP/DHP Grant W81XWH-12-2-0134.
Key words
chronic effects, concussion, spatial learning, working memory
D2-16
CAUSES OF INJURY VARIATION IN A PORCINE THOR-
ACIC CONTUSION MODEL
Santamaria, A.J.1 , Benavides, F.D.1, Guada, L.G.1, Nunez, Y.3,
Nasser, K.3, Guest, L.P.1, Levene, H.1,2, Solano, J.P.3, Guest, J.D.1,2
1University of Miami, The Miami Project to Cure Paralysis, Miami,
USA
2University of Miami, Neurological Surgery, Miami, USA
3University of Miami, Pediatric Critical Care, Miami, USA
Reproducible spinal cord injury (SCI) contusions are necessary for
assessment of safety and efficacy of experimental therapies. We
conducted a series of 93 T8 contusions in Yucatan minipigs to test
cellular, neuroprotective, and rehabilitative therapies; evaluating lo-
comotor outcome using an ordinal 10-point scale (Miami Porcine
Walking Scale-MPWS). Despite high mechanical reproducibility of
the Miami Porcine Impactor, we find variations in injury magnitude.
Severe injuries causing initial complete paraplegia lead to approxi-
mately 50% of pigs recovering weight-bearing and stepping, while the
other 50% do not (4–8 months post-contusion).
A multivariate model was constructed to determine the correlates
that may predict variations in tissue preservation and locomotor out-
come. Independent observers were trained such that inter-observer
MPWS score variation was < 0.5/10 points. Input variables to the
model include impact force in Newtons, the magnitude of post-injury
changes in heart rate and blood pressure, the size of injury signal
measured using ultrasound, and the presence/absence of somatosen-
sory evoked responses (SSEPs) post-injury. These variables were in-
put to a regression model to predict final MPWS or epicenter white
matter sparing. Results. Injuries > 20N peak force result in MPWS £ 5,
single variable correlates to MPWS were: (R2 = 0.91) for ultrasound
measured lesion-size, (R2 = 0.82) for final MPWS and white matter
preservation. There is an increase in blood pressure and heart rate
post-SCI but the correlation with the MPWS is poor (R2 < 0.2). Other
contributory variations are, differences in the diameter of cord and
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