Brain Research 887 2000 134–143 www.elsevier.com locate bres
Research report
Evaluation of combined fibroblast growth factor-2 and moderate hypothermia therapy in traumatically brain injured rats
a a
a b
a
Hong Qu Yan , Jianyun Yu , Anthony E. Kline , Peter Letart , Larry W. Jenkins ,
a a ,
Donald W. Marion , C. Edward Dixon
a
Brain Trauma Research Center , Department of Neurosurgery, University of Pittsburgh, Pittsburgh, Pennsylvania, PA 15260, USA
b
Department of Neurosurgery , Loyola University Chicago, Maywood, IL 60153, USA
Accepted 19 September 2000
Abstract
Both the exogenous administration of fibroblast growth factor-2 FGF-2 or the induction of moderate hypothermia have been shown to attenuate histopathology and improve functional outcome after traumatic brain injury TBI. Since combined therapeutic strategies may be
more beneficial than single therapies, we examined the potential synergistic effect of FGF-2 combined with moderate hypothermia treatment induced 10 min after TBI on functional and histological outcome following controlled cortical impact CCI injury. Fifty male
Sprague–Dawley rats were randomized to one sham and four CCI treatment groups: Sham1vehicle VEH; FGF-2 45 mg kg h for 3 h i.v.1Normothermia 3760.58C; FGF-21Hypothermia 3260.58C for 3 h; VEH1Norm; VEH1Hypo. Vestibulomotor performance on
the beam balance and beam-walk BW tasks on post-operative days 1–5 and spatial memory acquisition in the Morris water maze MWM on days 14–18 were assessed. After 4 weeks survival, histological evaluations CA and CA cell counts and lesion volume
1 3
were performed. MWM performance improved in all treatment groups, but combined treatment was not more efficacious than either alone. The FGF-21Hypo group performed significantly better than the other injured treatment groups in the BW task. Lastly, no
significant group differences in beam balance or histological outcome were observed. These data suggest a suboptimal and incomplete synergy of combined FGF-2 and hypothermia treatment. These data may indicate that either our dose of FGF-2 or combination therapy
was not optimized in our model.
2000 Elsevier Science B.V. All rights reserved.
Theme : Disorders of the nervous system
Topic : Trauma
Keywords : Controlled cortical impact; Neurotrophin; MWM
1. Introduction hypothermia after TBI reduces both neuronal death and
axonal injury [6,13] while providing functional benefit [5], The experimental evidence that moderate hypothermia is
others have shown that moderate hypothermia initiated neuroprotective when given before or even after traumatic
following CCI improves motor and spatial memory re- brain injury TBI or cerebral ischemia is overwhelming
covery despite no significant effect on structural pathology for general review see [14,35,36] and occurs across a
as reflected by cortical necrosis or hippocampal cell variety of different models. Specifically, hypothermia has
survival [18]. Thus, hypothermia may independently re- improved outcome following experimental TBI via central
duce both lethal and sublethal TBI damage. Despite or lateral fluid percussion [5,9,34], weight drop-induced
positive preliminary reports using moderate hypothermia in diffuse injury [29], and controlled cortical impact CCI
clinical TBI [8,36], recent results from the multicenter [7,18,36]. While some TBI studies have shown that
National Brain Injury Study: Hypothermia NABIS:H clinical trial appear disappointing personal communica-
tion. The results suggest that more refinement of the
Corresponding author. Tel.: 11-412-383-2188; fax: 11-412-624-
clinical application of hypothermia to severe TBI is needed
0943. E-mail address
: edixonneuronet.pitt.edu C.E. Dixon.
and perhaps the beneficial actions of hypothermia need to
0006-8993 00 – see front matter
2000 Elsevier Science B.V. All rights reserved. P I I : S 0 0 0 6 - 8 9 9 3 0 0 0 3 0 0 2 - X
H .Q. Yan et al. Brain Research 887 2000 134 –143
135
be better clarified and enhanced while minimizing potential 4 isoflurane Anaquest, Memphis, TN in oxygen and the
nonspecific effects, which can reduce therapeutic efficacy. rats intubated with a 14-gauge angiocatheter and me-
Consequently, the best protocol and patient populations for chanically ventilated with 2.0 isoflurane 66 N O bal-
2
the use of hypothermia in clinical TBI remain to be defined ance O
for surgery. Venous and arterial catheters were
2
and optimized. One approach that may prove useful is to placed in the tail for FGF-2 infusion and the continuous
combine other treatments with hypothermia that are in- monitoring of blood pressure and arterial glucose and
dependently effective and have other beneficial specific blood gas sampling. A rectal probe was inserted for
mechanistic actions. The use of exogenous trophic factors continuous monitoring of body temperature, and a micro-
is one class of candidates, especially since there is probe thermistor Type MT-29 1, Physiotemp Instruments
evidence that TBI alters neurotrophin receptors after injury Inc., Clifton, NJ was inserted into a temporalis muscle for
[39] and hypothermia treatment can reduce the endogenous indirect monitoring of brain temperature. A midline inci-
neurotrophic response of the brain after experimental CCI sion was made, the soft tissues reflected, and a 7 mm
[11,23,24]. craniotomy was made between lambda and bregma and
A number of studies in experimental TBI have shown centered 5 mm laterally on the right side of the central
that neurotrophins attenuate functional deficits or his- suture. The rats received a CCI through the craniotomy at a
topathology [16,44–46]. One of several neurotrophic fac- velocity of 4 m s with a tissue deformation depth of 2.6
tors, fibroblast growth factor-2 FGF-2 has been shown mm. Shams underwent identical surgical procedures, but
protective in a number of in vitro injury models [33,37,52], did not receive the impact. After injury, the scalp incision
and in vivo models such as fluid percussion TBI was closed with interrupted nylon sutures and the rat was
[12,25,38], stroke [27,28], and spinal cord injury [31,40]. removed from the injury device and returned to the heating
Importantly, FGF-2 is effective when administered after pad. The rat was stabilized on anesthesia for 30 min after
injury, and retards functional recovery when its endogen- which arterial blood gas ABG, glucose, and hematocrit
ous expression is inhibited [42]. were checked just before injury. Mean arterial pressure
Given the previous beneficial effects of FGF-2, we was kept above 90 mm Hg, brain and body temperature
combined FGF-2 treatment with moderate hypothermia were kept at 3760.58C, and pCO at 4065 mm Hg.
2
therapy to determine if synergistic effects occur by evaluating the effect of individual or combined FGF-2 and
2.3. Injury device moderate hypothermia therapy on motor, cognitive, and
histological outcome following a moderate CCI injury in The CCI injury device [15] consisted of a small 1.975
rats. cm bore, double-acting, stroke-constrained, pneumatic
cylinder with a 5.0 cm stroke. The cylinder was rigidly mounted in an angled vertical position on a crossbar. The
2. Material and methods lower rod end had an impactor tip attached i.e., that part
