Basic Sciences Alternatively-Spliced Extra Domain A of Fibronectin Promotes Acute Inflammation and Brain Injury After Cerebral Ischemia in Mice

Background and Purpose—The fibronectin isoform containing the alternatively spliced extra domain A (EDA -FN) is normally absent from the circulation, but plasma levels of EDA -FN can become markedly elevated in several human pathological conditions associated with inflammation including ischemic stroke. It remains unknown whether EDA -FN contributes to stroke pathogenesis or is simply an associative marker. Several in vitro studies suggest that EDA -FN can activate Toll-like receptor 4, an innate immune receptor that triggers proinflammatory responses. We undertook a genetic approach in mice to investigate the ability of EDA -FN to mediate inflammatory brain damage in a focal cerebral ischemia/reperfusion injury model. Methods—We used genetically modified EDA / mice, which constitutively express EDA -FN. Extent of injury, neurological outcome, and inflammatory mechanisms were assessed after 1-hour cerebral ischemia/23-hour reperfusion injury and compared with wild-type mice. Results—We found that EDA / mice developed significantly larger infarcts and severe neurological deficits that were associated with significant increased neutrophil and macrophage infiltration as quantitated by immunohistochemistry. Additionally, we found upregulation of nuclear factorB, cyclo-oxygenase-2, and inflammatory cytokines tumor necrosis factor, interleukin-1 , and interleukin-6 in the EDA / mice compared with wild-type mice. Interestingly, increased brain injury and neurological deficits were largely abrogated in EDA / mice by treatment with a specific Toll-like receptor 4 inhibitor. Conclusions—These findings provide the first evidence that EDA -FN promotes inflammatory brain injury after ischemic stroke and suggest that the elevated levels of plasma EDA -FN observed in chronic inflammatory conditions could worsen injury and outcome in patients after acute stroke. (Stroke. 2012;43:1376-1382.)