Combination of therapeutic hypothermia and insulin-like growth factor-1 in ischemic stroke rats : effect on infarct size and neurological outcome

COMBINATION OF THERAPEUTIC HYPOTHERMIA AND INSULIN-LIKE GROWTH FACTOR-1 IN ISCHEMIC STROKE RATS: EFFECT ON INFARCT SIZE AND NEUROLOGICAL OUTCOME Arnaud Potvin1, Pieter Olivier1, Joline Goossens1,2,3, Ron Kooijman3, Jacques De Keyser3, Said Hachimi-Idrissi1,2,3 1. Faculty of Medicine and Health Sciences, Ghent University 2. Department of Emergency Medicine, Ghent University Hospital 3. Center for Neurosciences, Free University Brussels Introduction – Intravenous (IV) administration of rt-PA within 4.5 h is the only approved therapeutic measure after stroke onset (IS) [1]. Only a few patients are eligible for this treatment because of presentation delay. Other alternative treatments such as therapeutic hypothermia (TH) and insulin-like growth factor-1 (IGF-1) have shown promising results in animal studies. Subcutaneous (SC) administration of IGF-1 in an animal model was neuroprotective only when administered within 30 min, and not after 2 and 4 hours after stroke onset [2]. We wonder if TH can synergistically be used with IGF-1 and if this combination could broaden the therapeutic window of IGF-1 in a rat model of focal cerebral ischemia [3]. Methods – Male Wistar rats (n=27) weighing 275-300 g were randomly divided into 9 experimental groups: a sham operated group, a normothermic (NT; 37.0±0.5 °C) and hypothermic (HT; 33.0±0.3 °C) control group, three normothermic IGF-1 treated groups and three hypothermic IGF-1 treated groups. SC IGF-1 administration occurred at either 30 min, 2 h or 4 h after ischemia onset. TH was induced within 10 min and maintained for 2 h with a delay of 20 min after the insult. Focal ischemia was induced by a local intracerebral injection of the potent vasoconstrictor endothelin-1 (Et-1). A non-blinded assessor evaluated functional outcome at 3, 6 and 24 h after the insult using the neurological deficit score (NDS), whereupon the animals were sacrificed and their brains were collected for histological examination. After staining with Cresyl Violet, digital images of the 50 μm slices were analyzed using Image J software. Three blinded assessors performed infarct size measurement independently. Results – Although a trend towards higher NDS with TH and later administration of IGF-1, was seen, no significant differences could be observed at either time point (Figure 1). In NT groups, there was a trend towards smaller infarcts with later administration of IGF-1 compared to the NT control group. This was not the case for the HT groups, as the HT control group had the smallest infarct sizes. All NT groups displayed larger infarct sizes than the HT counterparts, except for the NT group with IGF-1 administration at 4 h after stroke onset (Figure 2). Conclusions – Nor IGF-1 administration at any time point nor TH nor the combination of both treatments significantly improved the NDS at 3, 6 or 24 h and infarct size at 24 h. The hypothesis that TH could broaden the therapeutic window of opportunity for subcutaneously injected IGF-1 could not be confirmed. Further research is needed to evaluate whether larger experimental groups or alterations to the treatment protocol might be more effective. [1] Wahlgren et al. (2008). Lancet; 372(9646):1303-9. [2] De Geyter et al. (2013). Neuroscience; 250:253-62. [3] Kollmar et al. (2009). Journal of neurotrauma; 26(3):377-86.