was performed to observe the effects of S100A6 on capillary- like network formation. RESULTS: S100A6-treated hearts after cardiac I/R had signifi- cantly lower heart weight to tibia length (HW/TL) ratio, lower expression of b MHC and ANF in the infarct and non-infarct regions of myocardium and smaller cardiomyocyte size compared to controls at day 28. Extent of fibrosis/infarct size at day 28 was significantly lower in S100A6 pre-treated animals compared to empty plasmid and non-treated controls. MCE-derived myocar- dial blood flow at day 28 post ischemia/reperfusion in the risk area (infarct and peri-infarct regions) normalized to the remote non- infarct regions was significantly higher in the S100A6 treated group confirmed with IHC staining showing increased vessel density there. S100A6 over-expressing HUVECs formed signifi- cantly greater number of nodes and tubes compared to null- transduced and non-transduced controls after 3 hours. CONCLUSION: S100A6 overexpression results in reduced infarct size, not only by prevention of cardiomyocyte apoptosis (based on our previous data), but also via prevention of late fibrosis, enhancement of angiogenesis within the infarct and peri-infarct regions and attenuation of myocyte hyper- trophy after acute infarction-reperfusion. 003 MINICIRCLE-S100A6 GENE THERAPY BY ULTRASOUND- TARGETED MICROBUBBLE DESTRUCTION FOR TREATMENT OF ACUTE MYOCARDIAL INFARCTION-REPERFUSION IN RATS A Mofid, D Rudenko, WJ Cao, PJ Lee, NS Newman, MA Kuliszewski, HH Chen, TG Parker, H Leong-Poi Toronto, Ontario BACKGROUND: We have previously shown that UTMD of plasmid-S100A6, an EF-hand Ca2+-binding protein, 2 days prior to ligation/reperfusion attenuates myocardial infarction- reperfusion (I/R) injury, resulting in lower mortality and improved LV systolic function. The next step towards clinical translation is the development of UTMD techniques for effective delivery at the time of coronary reperfusion. Pre- liminary experiments with UTMD of minicircle DNA suggest more rapid and sustained transfection, and thus may be a more effective vector for UTMD in acute I/R. Hypothesis: We hypothesize that UTMD of minicircle- S100A6 (MC-S100A6), a very small episomal DNA vector, will lead to smaller infarct size and greater LV systolic function after myocardial I/R. METHODS: Male Fischer rats (n¼20; 150-200 g), underwent I/R induction surgery by a 30-minute ligation of the left anterior descending coronary artery (LAD) followed by reperfusion. MC- S100A6 (214 mcg+1x106 cationic microbubbles) was delivered by UTMD to the left ventricle of animals immediately after coronary reperfusion. Control animals received no therapy. Ani- mals were followed by serial echocardiography to evaluate LV systolic function and circumferential extent of akinesis at various time points until day 28. Subgroups of animals were sacrificed at earlier time points to collect tissue for PCR and Western blotting. RESULTS: We observed robust expression of exogenous S100A6 in all regions of the heart with maximal transfection in the infarct and per-infarct (anterior) regions at day 3 post-delivery. Western blot data of human S100A6 protein was consistent with PCR results. Echo data from control untreated and MC- S100A6 UTMD-treated rats after I/R injury showed that ani- mals treated with UTMD of MC-S100A6 had significantly improved fractional shortening (33.8% vs. 20.9%, P<0.05, day 28) and LVEF (59.7% vs. 45.5%, P<0.05, day 28), with less circumferential extent of akinesis (24.1% vs. 31.3%, P<0.05, day 28) compared to non-treated controls. CONCLUSION: UTMD of minicircle-S100A6 immediately af- ter coronary reperfusion results in targeted transfection in the infarct and peri-infarct regions, leading to improved LV sys- tolic function and less regional wall motion abnormalities, after acute myocardial infarction-reperfusion. 004 THE INFUSION OF MESENCHYMAL STROMAL CELLS INCREASES MYOCARDIAL S100A6 AND LIMITS ADVERSE LEFT VENTRICULAR REMODELING POST MYOCARDIAL INFARCTION JN Tsoporis, S Izhar, J Desjardins, G Yannarelli, A Keating, TG Parker Toronto, Ontario BACKGROUND: The beneficial effects originally attributed to the ability of bone-marrow derived mesenchymal stromal cells BM-MSCs to differentiate into cardiomyocytes, both in vitro and in vivo experimental models has been questioned due to the transient presence of donor cells at injury site following myocardial infarction (MI) suggesting that the MSC-induced improvement in hemodynamic function may be attributable to paracrine effects. We have shown that S100A6, a 20 kDa EF-hand Ca ++ -binding dimer, is upregulated and secreted following MI and forced expression post-MI attenuated myocyte hypertrophy, decreased fibrosis and apoptosis and was beneficial to the preservation of cardiac function. The aim of this study was to determine whether the beneficial effects of infused BM-MSCs may be related to the secretion of S100A6. METHODS: In 12 week old Balb/c mice, saline or green fluo- rescence protein (GFP)-marked BM-MSCs transfected with either a scrambled or S100A6 siRNA were infused intrave- nously 3-4 hrs post coronary artery ligation. RESULTS: Balb/c murine cultured GFP-marked BM-MSCs ex- press cytoplasmic and nuclear S100A6 at baseline and in response to a hypoxia (5%C0 2 /95% N2) for 1 hr increase S100A6 mRNA and protein approximately 2-3 fold, and release S100A6 (1 nM) in the culture media, responses inhibited in BM-MSCs transfected with S100A6 siRNA. Treatment of neonatal Balb/c cardiac myocytes with human recombinant S100A6 (1nM) for 1-24 hrs attenuated baseline apoptosis (30 per cent decrease in BAX/BCL2 ratio), induced cyclin-depen- dent kinase 1(CDK1) mRNA 1.5 fold, miR199a 2 fold and myocyte proliferation 2.5 fold, the latter inhibited in the pres- ence of anti-miR 199a. In Balb/c mice, 3-4 days post infusion, S56 Canadian Journal of Cardiology Volume 30 2014