Focal Embolic Cerebral Ischemia in Rats

Improving tissue-type plasminogen activator (tPA) thrombolytic therapy is a high priority in stroke research. The ability of tPA to convert plasminogen efficiently into clot-dissolving plasmin relies on an endogenous fibrinolytic assembly via a triple complex formation of tPA, annexin A2, and plasminogen. Annexin A2 is a cell-surface protein, which, in complex with its binding partner p11, forms a heterotetrameric (A2 2 p11 2 ) receptor for both plasminogen, the inactive precursor of plasmin, and its activator, tPA. By assembling tPA, annexin A2, and plasminogen, this complex increases the catalytic efficiency of tPA, enabling it to convert plasminogen to plasmin more efficiently than the same amount of tPA alone. We hypothesize that low-dose tPA plus recombinant annexin A2 protein (rA2) improve reperfusion and neurological outcomes. Our previous experiments have shown that combining rA2 with lowdose tPA successfully achieved reperfusion and reduced acute infarct size when treated at 2 hours, and significantly decreased hemorrhagic transformation when treatment was delayed to 4 hours after focal embolic stroke in rats. The purpose of the present study was to extend these promising findings by asking whether the benefits of tPA plus rA2 combination therapy can be sustained for long-term neurological outcomes. Materials and Methods Focal Embolic Cerebral Ischemia in Rats All experiments were performed following an institutionally approved protocol in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals. Male Wistar rats (280–330 g) were subjected to focal embolic strokes as we previously described.