Blood-brain barrier leakage after transient cerebral ischemia

Acute ischemic stroke is a devastating disease leaving more than half of its victims disabled and causing nearly 5% of all deaths worldwide. In large ischemic strokes, a major cause of death is brain edema, which follows blood-brain barrier (BBB) leakage. The BBB ensures brain homeostasis in health and disease by limiting the entry of harmful blood-borne substances into the brain parenchyma. With a leaky BBB, the brain becomes devoid of protection from detrimental components of the circulating blood. The BBB leakage in animal models of ischemia reperfusion has long been considered to be biphasic; however, a considerable amount of discrepancies exist among the studies. Knowing exact temporal changes of the BBB permeability (BBBP) is important for the management of stroke patients. When the BBB is open, BBBP alleviating therapies would be effective, neuroprotective or neurorestorative drugs would be introduced, and if the BBB is closed these drugs would not enter the brain. Practical and reliable biomarkers of BBBP status are needed. Stanniocalcins (STCs) are widely expressed in the brain and STC-1 expression is elevated in pathologies, such as hypoxia and focal ischemia. Recent data suggest a neuroprotective role for STC-1 especially trough hypoxic preconditioning (HPC). No previous data associate STC-1 and the BBB. We systematically evaluated disruption of the BBB following ischemia-reperfusion in a rat model of transient focal ischemia via suture occlusion of the middle cerebral artery for 90 min. Firstly (I, II), animals were allocated to 15 groups after reperfusion (25 min to 5 weeks). Secondly (III), a group of animals were evaluated repeatedly from 2 h to 1 week after reperfusion. BBBP to both small (gadolinium) (I, II, III), and large (Evans blue) (I) molecules were quantified by magnetic resonance imaging and fluorescence, respectively. Lastly, the contribution of STC-1 to HPC and the BBB was explored using STC-1 deficient mice (STC-/-). (I, II, III) After transient ischemia, the BBB leakage was continuous. Leakage to Evans Blue persisted up to 3 weeks and to gadolinium up to 5 weeks. Evans blue leakage slightly decreased at 36 and 72 h, gadolinium leakage was lesser at 25 min, 3 and 4 weeks. (IV) In STC-/- mice, HPC was effective in reducing lesion size, but these mice scored worse than wild type littermates. BBBP to Evans blue was not increased in STC-/- mice; neither under normal conditions, nor after hypoxia. To conclude, transient focal ischemia in rats triggers a continuous BBB leakage lasting for several weeks. Until the final closure of the BBB, no earlier transient closure occurs. This finding indicates a long therapeutic window opportunity in respect to BBB passage of drugs to treat stroke. BBBP imaging method used in these studies may be easily translated to clinics. STC-1 is not obligatory for hypoxic preconditioning and is not a determining component of the BBB. Yet, STC-1 is important for preservation of neurological function after transient ischemia.Aivoinfarkti on vakava tauti jonka seurauksena yli puolet potilaista vammautuu ja tarvitsevat ulkopuolista apua. Maailmassa kaikesta kuolemista 5% johtuu aivoinfarktista. Kun kyseessä on laaja-alainen aivoinfarkti, tärkein kuoleman syy on veri-aivoesteen häiriö, joka johtaa nesteen siirtymiseen suonista aivokudokseen ja siten aivoturvotukseen. Aivoinfarktin eläinmalleissa aivoinfarktin jälkeinen veri-aivoesteenhäiriö on toistetusti osoitettu bifaasiseksi ilmiöksi, määrittäen että, este ensin avautuu, sitten sulkeutuu ja uudestaan avautuu. Kuitenkin, tutkimustuloksissa on merkittäviä eroja, lähinnä esteen avautumisen ajankohdat suuresti vaihtelevat. Väitöskirjatyössäni olen tutkinut aivoiskemian aiheuttamaa veri-aivoesteen vauriota systemaattisesti histologisin menetelmin ja magneettikuvausta käyttäen. Osatöissäni I-III rotille aiheutettiin aivoinfarkti ja veri-aivoesteen läpäisevyys tutkittiin 5-15 eri aikapisteessä. Menetelminä käytettiin eläinten ollessa elossa varjoaine (gadolinium, pieni molekyyli) -magneettikuvaus ja kokeiden lopetusvaiheessa Evans blue värjäys (iso molekyyli). Osajulkaisussa IV tutkittiin stanniokalsiini-1 (STC-1):n roolia veri-aivoesteen läpäisevyydessä ja hypoksia-esikäsittelyn jälkeen aivoinfarktista suojaamisessa (hypoxic preconditioning). Tätä varten käytettiin STC-1 poistogeenisiä hiiriä ja aivoinfarktimallia. Tutkimuksessa I-III todettiin veri-aivoesteen olevan jatkuvasti avoimena, toisin sanoen osoitimme häiriön olevan monofaasinen. Veri-aivoesteen lisääntynyt Evans blue-läpäisevyys on normalisoitunut 3 vko aivoinfarktin aiheuttamisen jälkeen ja gadolinium-läpäisevyys 5 vko jälkeen. Evans blue-läpäisevyys hieman väheni 36 ja 72 t infarktista, gadolinium läpäisi vähemmän 25 min sekä 3 ja 4 vko infarktista. STC-1 poistogeeniset hiiret pystyivät suojautumaan infarktista hypoksia-esikäsittelyn jälkeen, mutta olivat huonommassa neurologisessa tilassa kuin villityypin hiiret. Veri-aivoesteen vaurioitumisessa ei todettu eroja. Yhteenvetona, aivoinfarkti johtaa veri-aivoesteen jatkuvaan avautumiseen, joka kestää useita viikkoja. Ei paljastunut merkittäviä eroja läpäisevyydessä kunnes aivo-veriesteen toiminta lopulta korjaantui. Tulokset tulevat auttamaan veri-aivoesteen toimintahäiriön patofysiologian syvällisemmässä ymmärtämisessä ja siten saattavat auttaa kehittämään täsmähoitoja tähän vakavaan, aivohalvauspotilaiden henkeä uhkaavaan aivoturvotukseen. Väitöskirjani magneettikuvaukseen perustuva tutkimusmenetelmä voisi siirtää sellaisenaan kliiniseen käyttöön veri-aivoesteen läpäisevyyden tutkimiseksi aivoinfarkti potilailla

TIA model is attainable in Wistar rats by intraluminal occlusion of the MCA for 10 min or shorter

Transient ischemic attack (TIA) has received only little attention in the experimental research field. Recently, we introduced a TIA model for mice, and here we set similar principles for simulating this human condition in Wistar rats. In the model: 1) transient nature of the event is ensured, and 2) 24 h after the event animals are free from any sensorimotor deficit and from any detectable lesion by magnetic resonance imaging (MRI). Animals experienced varying durations of ischemia (5, 10, 12.5, 15, 25, and 30 min, n = 6-8 per group) by intraluminal middle cerebral artery occlusion (MCAO). Ischemia severity and reperfusion rates were controlled by cerebral blood flow measurements. Sensorimotor neurological evaluations and MRI at 24 h differentiated between TIA and ischemic stroke. Hematoxylin and eosin staining and apoptotic cell counts revealed pathological correlates of the event. We found that already 12.5 min of ischemia was long enough to induce ischemic stroke in Wistar rats. Ten min or shorter durations induced neither gross neurological deficits nor infarcts visible on MRI, but histologically caused selective neuronal necrosis. A separate group of animals with 10 min of ischemia followed up to 1 week after reperfusion remained free of infarction and any MRI signal change. Thus, 10 min or shorter focal cerebral ischemia induced by intraluminal MCAO in Wistar rats provides a clinically relevant TIA the rat. This model is useful for studying molecular correlates of TIA. (C) 2017 Elsevier B.V. All rights reserved.Peer reviewe

TIA model is attainable in Wistar rats by intraluminal occlusion of the MCA for 10 min or shorter

Transient ischemic attack (TIA) has received only little attention in the experimental research field. Recently, we introduced a TIA model for mice, and here we set similar principles for simulating this human condition in Wistar rats. In the model: 1) transient nature of the event is ensured, and 2) 24 h after the event animals are free from any sensorimotor deficit and from any detectable lesion by magnetic resonance imaging (MRI). Animals experienced varying durations of ischemia (5, 10, 12.5, 15, 25, and 30 min, n = 6–8 per group) by intraluminal middle cerebral artery occlusion (MCAO). Ischemia severity and reperfusion rates were controlled by cerebral blood flow measurements. Sensorimotor neurological evaluations and MRI at 24 h differentiated between TIA and ischemic stroke. Hematoxylin and eosin staining and apoptotic cell counts revealed pathological correlates of the event. We found that already 12.5 min of ischemia was long enough to induce ischemic stroke in Wistar rats. Ten min or shorter durations induced neither gross neurological deficits nor infarcts visible on MRI, but histologically caused selective neuronal necrosis. A separate group of animals with 10 min of ischemia followed up to 1 week after reperfusion remained free of infarction and any MRI signal change. Thus, 10 min or shorter focal cerebral ischemia induced by intraluminal MCAO in Wistar rats provides a clinically relevant TIA the rat. This model is useful for studying molecular correlates of TIA. © 2017 Elsevier B.V

Etiology of first-ever ischaemic stroke in European young adults: the 15 cities young stroke study.

BACKGROUND AND PURPOSE: Risk factors for IS in young adults differ between genders and evolve with age, but data on the age- and gender-specific differences by stroke etiology are scare. These features were compared based on individual patient data from 15 European stroke centers. METHODS: Stroke etiology was reported in detail for 3331 patients aged 15-49 years with first-ever IS according to Trial of Org in Acute Stroke Treatment (TOAST) criteria: large-artery atherosclerosis (LAA), cardioembolism (CE), small-vessel occlusion (SVO), other determined etiology, or undetermined etiology. CE was categorized into low- and high-risk sources. Other determined group was divided into dissection and other non-dissection causes. Comparisons were done using logistic regression, adjusting for age, gender, and center heterogeneity. RESULTS: Etiology remained undetermined in 39.6%. Other determined etiology was found in 21.6%, CE in 17.3%, SVO in 12.2%, and LAA in 9.3%. Other determined etiology was more common in females and younger patients, with cervical artery dissection being the single most common etiology (12.8%). CE was more common in younger patients. Within CE, the most frequent high-risk sources were atrial fibrillation/flutter (15.1%) and cardiomyopathy (11.5%). LAA, high-risk sources of CE, and SVO were more common in males. LAA and SVO showed an increasing frequency with age. No significant etiologic distribution differences were found amongst southern, central, or northern Europe. CONCLUSIONS: The etiology of IS in young adults has clear gender-specific patterns that change with age. A notable portion of these patients remains without an evident stroke mechanism according to TOAST criteria

Etiology of first-ever ischaemic stroke in European young adults: the 15 cities young stroke study

Background and purposeRisk factors for IS in young adults differ between genders and evolve with age, but data on the age- and gender-specific differences by stroke etiology are scare. These features were compared based on individual patient data from 15 European stroke centers