The Role of Matricellular Proteins in Experimental Subarachnoid Hemorrhage-Induced Early Brain Injury

The Role of Tenascin-C in Tissue Injury and Repair After Stroke

Stroke is still one of the most common causes for mortality and morbidity worldwide. Following acute stroke onset, biochemical and cellular changes induce further brain injury such as neuroinflammation, cell death, and blood-brain barrier disruption. Matricellular proteins are non-structural proteins induced by many stimuli and tissue damage including stroke induction, while its levels are generally low in a normal physiological condition in adult tissues. Currently, a matricellular protein tenascin-C (TNC) is considered to be an important inducer to promote neuroinflammatory cascades and the resultant pathology in stroke. TNC is upregulated in cerebral arteries and brain tissues including astrocytes, neurons, and brain capillary endothelial cells following subarachnoid hemorrhage (SAH). TNC may be involved in blood-brain barrier disruption, neuronal apoptosis, and cerebral vasospasm via the activation of mitogen-activated protein kinases and nuclear factor-kappa B following SAH. In addition, post-SAH TNC levels in cerebrospinal fluid predicted the development of delayed cerebral ischemia and angiographic vasospasm in clinical settings. On the other hand, TNC is reported to promote fibrosis and exert repair effects for an experimental aneurysm via macrophages-induced migration and proliferation of smooth muscle cells. The authors review TNC-induced inflammatory signal cascades and the relationships with other matricellular proteins in stroke-related pathology.

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.

Matricellular proteins as possible biomarkers for early brain injury after aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage remains devastating, and the most important determinant of poor outcome is early brain injury (EBI). In clinical settings, as a surrogate marker of EBI, loss of consciousness at ictus, poor initial clinical grades, and some radiographic findings are used, but these markers are somewhat subjective. Thus, it is imperative to find biomarkers of EBI that have beneficial prognostic and therapeutic implications. In our opinion, an ideal biomarker is a molecule that is implicated in the pathogenesis of both EBI and subsequently developing delayed cerebral ischemia (DCI), being a therapeutic target, and can be measured easily in the peripheral blood in an acute stage. A good candidate of such a biomarker is a matricellular protein, which is a secreted, inducible and multifunctional extracellular matrix protein. There are many kinds of matricellular proteins reported, but only tenascin-C, osteopontin, galectin-3 and periostin are reported relevant to EBI and DCI. Reliable biomarkers of EBI may stratify aneurysmal subarachnoid hemorrhage patients into categories of risk to develop DCI, and allow objective monitoring of the response to treatment for EBI and earlier diagnosis of DCI. This review emphasizes that further investigation of matricellular proteins as an avenue for biomarker discovery is warranted.