NEUROPROTECTION/ Acute Therapy

BACKGROUND
The only approved stroke treatment so far is the acute thrombolytic therapy with recombinant tissue plasminogen activator (rt-PA) when administered within 3-4.5 hours after symptoms onset. However, a reduced number of patients (5-8%) profit by this treatment, primarily because of the narrow therapeutic time-window and the risk of brain bleedings beyond thromrbolytic therapy to achieve the recanalization of the occluded artery. Moreover, the inflammatory response that accompanied necrotic brain injury contributes to aggravate acutely the progression of ischemic pathology. Inflammatory and brain damaged cells release a variety of cytotoxic agents including cytokines, MMPs and ROS which induce more cell damage as well as disruption of BBB and brain edema.
Thereby, it would be desirable to improve the efficacy and safety for thrombolytic therapy of stroke using combined anti-inflammatory strategies that may ameliorate the ischemic injury and means the best therapy translated at the clinical level.

Our research, conducted on experimental models of cerebral ischemia, is focused on the development of neuroprotective strategies aimed to salvage ischemic brain tissue by means complementary to reperfusion. Our goal is to find out a multimodal treatment that combines the administration of tPA together with other co-agents (as simvastatin and/or anti-aggregants with anti-inflammatory and neuro-protective properties) in attempt to obtain the most therapeutic benefice in the acute phase of ischemic stroke.

EXPERIMENTAL MODELS AND TECHNIQUES
Ischemic stroke has a complex pathophysiology involving the interplay of many different cells and tissues. Animal models of ischemic stroke are procedures inducing cerebral ischemia, which mimicked satisfactorily this cerebrovascular disease. Therefore, research stroke conducted on animal models has been shown essential for treatment approach of ischemic stroke.

Intra-arterial Suture Occlusion Model of Focal Cerebral Ischemia
Infarction in the territory of the middle cerebral artery (MCA) is induced by extracranial vascular occlusion on rat. A heat-blunted 4/0 nylon-monofilament is used to block the origin of MCA during 90 or 120 min and then, the monofilament is removed and reperfusion is allowed during the followed 24, 48 or 72 h.
This model mimics a clinical situation where recanalization of the occluded artery takes place, allowing test neuroprotectants that could be potentially co-administered with reperfusion agents like tPA.

Embolic Model of Focal Cerebral Ischemia
The stroke animal model by clot embolism has a large scientific interest in the clinical field because the high incidence of human thrombotic stroke and the use of reperfusion therapy with tPA, which can be assay on this model. Thromboembolic occlusion at the proximal level of MCA is achieved by injection of a rich fibrin clot through the internal carotid artery in the rat. Clots are previously performed using arterial blood from a donor rat. Thrombolytic therapy with tPA (9 mg/Kg) is administered by tail vein infusion (2 mg/mL;75 l/min) at different times points (2, 3, 4 hours) after occlusion.

Relative Cerebral Blood Flow (rCBF) is measured in the cortex supplied by the MCA by continuous Laser Doppler flowmetry (LDF) to ensure the successful of the artery occlusion or reperfusion in these models.  To examine the grade of infarction on rats, analysis of the infarct volume is evaluated using 2,3,5-triphenyltetrazolium chloride (TTC) staining and neurological score is assayed with a 9-point neurological at baseline (1-2 h) and each 24 h after occlusion.

NMR Imaging
Bruker-BIOSPEC 70/30 USR, 7 T Preclinical MRI System is used for the neuroimaging studies. Neuroimaging studies are conducted in vivo to valuate the cytotoxic edema and ischemic lesion (DWI, ADC map and T2WI) in the acute phase. Specific sequences are performed to assess Brain-Blood Barrier disruption (DCE) and occurrences of intracranial hemorrhages (T2*WI). Angiography is performed to document MCA occlusion or recanalization

The Neuroprotection Team:

Lidia Garcia-Bonilla, PhD
Staff Researcher
lidgarcia@ir.vhebron.net / lidibonilla@gmail.com
LidiaCV

Mireia Campos, MSc
PhD Student
mir@ir.vhebron.net /
MireiaCV