Abstract 1007: Bone Marrow-Derived CD39 Provides Critical Protection in the Ischemic Brain
The ectoapyrase CD39 is an important modulator of cellular response to vascular inflammation and ischemia. CD39 is thought to provide this protection by catalyzing the breakdown of ADP and ATP into AMP. As extracellular nucleotides, ADP and ATP drive inflammatory and coagulation cascades in platelets, granulocytes, and endothelial cells during hypoxia and ischemia-reperfusion. CD39 has been shown to be protective in stroke by dampening these inflammatory cascades in models using CD39-deficient mice. The majority of CD39 is found on leukocytes and endothelial cells, though, it has not been determined if its presence on only one of these cell types can maintain homeostasis. Given that we have shown that soluble CD39 can protect CD39-deficient mice during ischemia, we hypothesized that bone-marrow derived cells expressing CD39 could protect a CD39−/− mouse from ischemic injury. To examine this we performed bone marrow transplants between 8 week old wild-type (CD39+/+) and CD39−/−mice. After 4 weeks, we induced cerebral infarcts with a photo-thrombotic model of middle cerebral artery occlusion. Forty-eight hours post infarct, the ipsilateral and contralateral hemispheres were compared to each other and between subjects via flow cytometry. Interestingly, reconstitution of a CD39−/− mouse with CD39+/+ bone marrow resulted in a phenotype very similar to that of a wild-type mouse. Time to thrombus formation of a CD39−/−mouse transplanted with CD39+/+ marrow was comparable to that of a wild-type mouse (5 min vs. 6 min measured by Doppler flow). Meanwhile, a CD39−/− mouse transplanted with CD39−/−marrow took 4 times longer to clot (24 min) in accordance with previous data on platelet purine receptor desensitization in CD39 deficient mice. This was reflected in flow cytomteric analysis of infarcted hemispheres. A CD39−/− mouse transplanted with wild-type bone marrow was protected, similar to a wild type animal, from leukocyte infiltration (2.56x105 vs 2.48x105). By comparison, a CD39−/− mouse had 17.2% more infiltrating cells than a reconstituted mouse (2.56x105 vs 3.0x105). In conclusion, bone marrow-derived CD39 appears sufficient to restore purine receptor sensitivity and mediate CD39’s anti-coagulant, anti-inflammatory effects in stroke.