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Manipulating the activity of the mammalian target of rapamycin
(mTOR) after experimental spinal cord injury (SCI) is reported to
increase intraspinal sprouting and functional recovery. Our published
evidence correlates post-traumatic maladaptive plasticity of both
primary afferents and ascending propriospinal neurons with the de-
velopment of autonomic dysreflexia (AD) after complete high tho-
racic (T4) SCI. Therefore, we are now testing the hypothesis that
pharmacologically targeting mTOR can modulate maladaptive neu-
ronal plasticity underlying AD. We are testing specifically whether
prolonged post-injury treatment with the antibiotic, rapamycin (RAP),
impedes intraspinal neuronal plasticity by inhibiting mTOR and,
consequently, mitigates the development of AD. Alternatively, pro-
longed post-injury treatment with bisperoxovanadium (bpV(pic)
should disinhibit mTOR activities to promote maladaptive plasticity
and exacerbate AD. We are employing pharmacological and cardio-
physiological methodologies we’ve used to document the palliative
effects of gabapentin treatment on the incidence and severity of AD.
Based on FDA approval of RAP, if therapeutic efficacy is shown in
our SCI model then clinical translation is tenable as a potential pro-
phylactic treatment to abrogate AD. Initial data on the time course of
phosphorylated mTOR (p-mTOR) expression in critical spinal cord
segments from naive tissues or at 3, 10 and 21 days post SCI (n
=
2–3/
group) showed that there is an approximate two-fold increased ex-
pression after 10 days that trends back to naı¨ve levels by 21 days. In
contrast, compared to 10 days, p-mTOR expression levels were ele-
vated after 21 days in rats that received colorectal distension (CRD) to
induce AD before euthanasia. Alternatively, following prolonged
RAP or bpV(pic) treatment (n
=
2–3/group), both mTOR and p-mTOR
expression profiles in spinal cord segments are being assessed com-
paratively. Moreover, proteins related to sprouting/synaptogenesis/
inflammation/injury will be evaluated by measuring Akt/PKB, p70 S6,
synaptophysin, PSD-95, VGlut2, c-Fos, p-NR1, IL-1b, ATF3, TSP4
and a2d1 receptor levels to establish correlations between such ex-
pression profiles and the incidence and severity of spontaneous and/or
experimentally induced AD.
Keywords: Autonomic Dysfunction, Spinal cord transection, Ra-
pamycin, Bisperoxivanadium, Sprouting
A8-02
IN VIVO REPROGRAMMING REACTIVE GLIA INTO IPSCS
TO PRODUCE NEW NEURONS IN THE CORTEX FOL-
LOWING TRAUMATIC BRAIN INJURY
Xiang Gao, Xiaoting Wang,
Jinhui Chen
Indiana University School of Medicine, Neurological Surgery, In-
dianapolis, USA
Traumatic brain injury (TBI) results in a significant amount of cell
death in the brain. Unfortunately, the adult mammalian brain pos-
sesses little regenerative potential following injury and little can be
done to reverse the initial brain damage caused by trauma. There is a
large number of reactive glia surrounding the injury area following
TBI. Reprogramming adult cells to generate induced pluripotent stem
cell (iPSCs) has opened new therapeutic opportunities to reprogram
these reactive glia to neural fate for possible cell-replacement therapy
in vivo. In this study we show that four retroviral mediated tran-
scription factors, Oct4, Sox2, Klf4 and c-Myc, expressed in the re-
active glial cells and cooperatively reprogrammed infected glia into
iPSCs in the adult neocortex following TBI. These iPSCs further
differentiated into a large number of neural stem cells, which further
differentiated into neurons and glia in situ, and filled up the tissue
cavity induced by TBI. The induced neurons showed a typical neu-
ronal morphology with axon and dendrites, and exhibited action po-
tential. The glia were preferentially astrocytes and oligodendrocytes,
but not microglia. Our results report a strategy to convert a non-
neurogenic cortex into a neurogenic region, one that can be potentially
developed for brain repair through reprogramming reactive glia resi-
dent in the injury area following brain injury.
Keywords: Reprogramming in vivo,, iPSC, reactive glial, neuron,
Traumatic brain Injury,
A8-03
TRAUMATIC BRAIN INJURY SEVERITY AFFECTS NEU-
ROGENESIS IN ADULT MOUSE HIPPOCAMPUS
Xiaoting Wang
, Xiang Gao, Stephanie Michalski, Shu Zhao, Jinhui
Chen
Indiana University School of Medicine, Neurosurgery, Indianapolis,
USA
Traumatic brain injury (TBI) has been proven to enhance neural stem
cell (NSC) proliferation in the hippocampal dentate gyrus (HDG),
which provides a potential approach to repairing the damaged brain by
increasing neurogenesis. However, various groups reported contra-
dictory results on whether TBI increases neurogenesis, partially due to
a wide range in the severity of injury seen with different TBI models.
To address whether the severity of TBI affects neurogenesis in the
injured brain, we assessed neurogenesis in mouse brains receiving
different severities of cortical impact with the same injury device. The
mice were subjected to mild, moderate, or severe TBI by a controlled
cortical impact (CCI) device. The effects of TBI severity on neuro-
genesis were evaluated at three stages: NSC proliferation, immature
neurons, and newly generated mature neurons. The results showed
that mild TBI did not affect NSC proliferation or neurogenesis.
Moderate TBI promoted NSC proliferation without increasing neu-
rogenesis. Severe TBI increased both NSC proliferation and neuro-
genesis. Our data suggest that the severity of injury affects adult
neurogenesis in the hippocampus, which may partially explain the
inconsistent results of different groups regarding neurogenesis fol-
lowing TBI. Further understanding the mechanism of TBI-enhanced
neurogenesis may provide a potential approach for using endogenous
NSCs to protect against neuronal loss after trauma.
Keywords: Neurogenesis, Neural stem cell proliferation, Traumatic
brain injury, Injury severity
A8-04
FIX THE LESION OR KEEP BRAIN DEVELOPMENT
GOING? NEUROBLAST PATTERNS AFTER TBI IN THE
IMMATURE GYRENCEPHALIC BRAIN
Beth Costine
, Colin Smith, George Price, Sabrina Taylor, Ann-
Christine Duhaime
Massachusetts General Hospital/ Harvard Medical School, Neuro-
surgery, Boston, USA
In rodents, neuroblasts generated in the subventicular zone have been
shown to migrate through gray matter to cortical lesions where they
aid in neural repair; however, it is not yet known if neuroblasts target
traumatic lesions in the immature gyrencephalic brain. Here we
quantify neuroblasts at the injury site (rostral gyrus) where both gray
matter and white matter are damaged, and at a distant, non-injured site
undergoing active population by neuroblasts (insular cortex). Piglets
(postnatal day 7; N
=
23) received a cortical impact to the rostral gyrus
or sham surgery and bromodeoxyuridine (BrdU) before or after injury.
A-39