Fumi Nakano

Role of Periostin in Early Brain Injury After Subarachnoid Hemorrhage in Mice

Background and Purpose— A matricellular protein tenascin-C is implicated in early brain injury after experimental subarachnoid hemorrhage (SAH). This study first evaluated the role of another matricellular protein periostin and the relationships with tenascin-C in post-SAH early brain injury. Methods— Wild-type (n=226) and tenascin-C knockout (n=9) C57BL/6 male adult mice underwent sham or filament perforation SAH modeling. Vehicle, anti-periostin antibody, or recombinant periostin was randomly administrated by an intracerebroventricular injection at 30 minutes post-modeling. Neuroscores, SAH grading, brain water content, immunostaining, and Western blotting were blindly evaluated at 24 to 48 hours post-SAH. Results— Periostin was induced in brain capillary endothelial cells and neurons at 24 hours post-SAH. Anti-periostin antibody improved post-SAH neurobehavior, brain edema, and blood–brain barrier disruption associated with downregulation of tenascin-C, inactivation of p38, extracellular signal-related kinase 1/2 and matrix metalloproteinase-9, and subsequent preservation of zona occludens-1. Recombinant periostin aggravated post-SAH brain edema and tenascin-C induction. Tenascin-C knockout prevented post-SAH neurobehavioral impairments and periostin induction. Conclusions— Periostin may cause post-SAH early brain injury through activating downstream signaling pathways and interacting with tenascin-C, providing a novel approach for the treatment of early brain injury.

To Improve Translational Research in Subarachnoid Hemorrhage

The advantage of animal studies is to study a relatively homogeneous group of animals instead of a heterogeneous group of patients in clinical studies. Animal studies also offer a wider range of possibilities for example such as examining toxicity of a specific treatment or studying the underlying mechanisms of diseases. However, because most of new therapies shown to be effective in animal studies have been ineffective in clinical trials, some guidelines including the Stroke Therapy Academic Industry Roundtable (STAIR) were proposed to improve the quality and reproducibility of individual animal studies evaluating neuroprotective drugs in ischemic stroke [1–3]. Recent special issues BChallenges and Controversies in Translational Stroke Research, Part 1 and 2^ in this journal provide an excellent overview as to the innate biological variability and the methodological challenges that are needed to address bias in preclinical research for the successful translation of experimental therapies to clinical stroke treatments. The proposed standards include (1) clinical relevance of animal models (detailed information on animals used (species, strain, age, weight, gender, etc.), selection of anesthetics, inclusion and exclusion criteria), (2) sample size calculation and accurate statistical analysis, (3) treatment (randomization, allocation concealment, dose-response determinations, therapeutic time window, blood-brain barrier permeability and tissue drug levels, physiological monitoring), (4) outcome (blinded assessment, at least two outcomemeasures (morphology and function), covering both acute (1–3 days) and longterm (7–30 days) endpoints), and (5) reporting of animals excluded from analysis, potential conflicts of interest, and study funding [1–7]. In addition, several challenges exist to successfully translate the outcomes from animal research to humans in a clinical setting. First, age and sex are two important non-modifiable risk factors for stroke [5, 8]. With aging, there is a shift toward a proinflammatory phenotype in the brain as well as the periphery, and blood-brain barrier disruption [8]. Women are protected from stroke before menopause, but have increased stroke rates and worse outcomes at older ages [5]. On the other hand, the use of adult reproductive female animals in stroke research is complicated by the sex hormone cycle. However, the male-biased use of research animals is distinguished from the clinical situation where there is a disproportionate and growing female stroke population, making it important to include both sexes with diverse ages in preclinical as well as clinical studies that evaluate potential stroke therapies. Second, cerebrovascular anatomy and collaterals, as well as biological and secondary neuroinflammatory responses to insults, are different between species or strains, causing flawed design, unreliable outcomes, unnecessarily more costs, and experimental animals [7, 9–11]. Genetic differences between animals and humans, and even within animal species, strains, and cell lines, may affect the immune responses and outcomes [10, 12, 13]. Third, stroke patients have many comorbidities or vascular risk factors including hypertension, diabetes mellitus, dyslipidemia, cardiac diseases, current smoking, obesity, poor diet, inactivity, high alcohol intake, psychosocial stress and depression, social factors such as marital and residence status (i.e., living alone), and prestroke dysfunction, causing stroke severity [5, 14]. Animal models having these factors are also subjected to different stroke injuries or changes in the structure of the neurovascular unit [14]. Thus, the use of young healthy animals causes a barrier for translation of findings to patients, while, in preclinical stroke studies with comorbidities, comorbidity duration * Hidenori Suzuki mie1192suzuki@gmail.com

Tenascin-C in brain injuries and edema after subarachnoid hemorrhage: Findings from basic and clinical studies

Subarachnoid hemorrhage (SAH) by a rupture of cerebral aneurysms remains the most devastating cerebrovascular disease. Early brain injury (EBI) is increasingly recognized to be the primary determinant for poor outcomes, and also considered to cause delayed cerebral ischemia (DCI) after SAH. Both clinical and experimental literatures emphasize the impact of global cerebral edema in EBI as negative prognostic and direct pathological factors. The nature of the global cerebral edema is a mixture of cytotoxic and vasogenic edema, both of which may be caused by post‐SAH induction of tenascin‐C (TNC) that is an inducible, non‐structural, secreted and multifunctional matricellular protein. Experimental SAH induces TNC in brain parenchyma in rats and mice. TNC knockout suppressed EBI in terms of brain edema, blood‐brain barrier disruption, neuronal apoptosis and neuroinflammation, associated with the inhibition of post‐SAH activation of mitogen‐activated protein kinases and nuclear factor‐kappa B in mice. In a clinical setting, more severe SAH increases more TNC in cerebrospinal fluid and peripheral blood, which could be a surrogate marker of EBI and predict DCI development and outcomes. In addition, cilostazol, a selective inhibitor of phosphodiesterase type III that is a clinically available anti‐platelet agent and is known to suppress TNC induction, dose‐dependently inhibited delayed cerebral infarction and improved outcomes in a pilot clinical study. Thus, further studies may facilitate application of TNC as biomarkers for non‐invasive diagnosis or assessment of EBI and DCI, and lead to development of a molecular target drug against TNC, contributing to the improvement of post‐SAH outcomes.