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arly UPA independent experimental thrombusesolution: MMP2 as an alternative mechanismikram Sood BS,* M Mitsuya BS, Miller Erin MS, Cathy Luke LVT,ilbert Upchurch MD, FACS, Thomas Wakefield MD, FACS,eter Henke MD, FACSniversity of Michigan, Ann Arbor, MI

NTRODUCTION: Physiologic venous thrombosis (VT) resolutions thought to be primarily an urokinase plasminogen activator (uPA)ependent mechanism, although other non-fibrinolytic mechanismsay exist. We hypothesize that early VT resolution may be matrix-etalloproteinase (MMP) 2 or 9 dependent.

ETHODS: Male B6/129 (WT) and matched uPA genetically de-eted (KO) mice underwent IVC ligation to create stasis VT, withissue harvest at 4, 8, and 21 days. Thrombus size (weight to length),issue analysis by real time PCR, gelatin zymography, immunohisto-hemistry (IHC), and western immunoblot were performed.

ESULTS: Thrombus size was similar between WT and uPA KOice at 4d, but was 28 and 42% larger at 8 and 21 days (N � 13-20;

�.01). At 4d, intrathrombus neutrophils and monocytes were reducedand 3.5 fold in uPA KO as compared with WT (N � 5-6; p�.01),hile vein wall gene expression of elastase, cathepsin-G, MMP2 andMP9 were not significantly altered. Fibrin at 4d was increased 1.4 fold

n uPA KO as compared to control (N � 5-6;p�.05). Importantly, tPAas not up regulated in uPA KO mice at day 4 (13�4 vs. 11�2 AU/mgrotein, N�5-6), but PAI-1 levels were increased 2.5 fold (N � 4-5;�.01). Thrombus active MMP2, but not MMP9, was elevated 9 foldn uPA KO mice as compared with WT at 4d (N � 9-10; p�.01).hrombus type III collagen was reduced as measured by IHC analysis.

ONCLUSIONS: Early experimental venous thrombosis resolu-ion is independent of uPA, and, in part, inflammatory cell influx.

MP2 dependent thrombus collagenolysis is an important mecha-ism of VT resolution.

urgically implantable magnetic resonancengiography coils improve resolution to allowisualization of blood flow dynamicsamara N Fitzgerald MD, PhD, Akihito Muto MD, PhD,iffany T Fancher MD, Peter B Brown, Karen A Martin RT(R),art E Muhs MD, PhD, Douglas L Rothman PhD,Todd Constable PhD, Smita Sampath PhD,lan Dardik MD, PhD, FACSale University, New Haven, CT

NTRODUCTION: Magnetic resonance angiography (MRA) is clini-ally useful but of limited applicability to small animal research modelsue to poor signal resolution, with typical voxel sizes of 1mm that are

nsufficient to analyze vessels of diameter �1mm. We determinedhether surgically implantable periadventitial extravascular MRA coils

ncrease signal resolution adequately to examine blood flow dynamics.

ETHODS: A custom MRA coil was surgically implanted next to thearotid artery of a New Zealand White rabbit. A stenosis was created inhe carotid artery to induce complicated, non-laminar (‘turbulent’) flow.

low was also measured with a Doppler flow probe; vessel diameters and P

S1132008 by the American College of Surgeons

ublished by Elsevier Inc.

low velocities were validated with duplex ultrasound. Phase contrastmages were obtained with 3T MRA and velocity profiles were calcu-ated under both laminar and complicated flow conditions (Matlab).

ESULTS: Carotid artery blood flow was 25.5�5.5 ml/min (n�2),nd was reduced to 12.5�2.5 ml/min (n�2) by the stenosis. An MRAoxel size of 0.1x0.1x3mm was achieved. The carotid artery diameteras 1.85�0.1 mm (n�5), thus achieving arterial cross-section images

ontaining 270�33 voxels (n�5). Velocity profiles resembled laminar flowroximal to the stenosis. Immediately distal to stenoses, flow became com-licated and then returned to laminar conditions with increasing distance.

ONCLUSIONS: Implantable, extra-vascular coils can measuremall enough MRA voxel sizes to reproducibly calculate complexelocity profiles under both laminar and complicated flow in a smallnimal model. This technique may be applied to study blood flowynamics of vessel remodeling and atherogenesis.

O attenuates platelet activation and recruitmentf neutrophils: A potential mechanism for blockingntimal hyperplasialka Sachdev MD, Chase Gladstone BA, Min Qi BA,

eung Namkoong PhD, Edith Tzeng MD, FACSniversity of Pittsburgh Medical Center, Pittsburgh, PA

NTRODUCTION: We have demonstrated that a brief exposure tonhaled CO markedly inhibits intimal hyperplasia (IH) in rats. Theeverity of IH correlates with early platelet-leukocyte interactions athe vessel wall. Therefore, we hypothesize that CO may modulatelatelet activation and recruitment of neutrophils.

ETHODS: Sprague Dawley rats were treated with inhaled CO (250pm) for 1 hr and recovered in room air (RA) for 1 hr. Control rats wereaintained in RA. Platelets were isolated from blood by gentle centrif-

gation. Neutrophils were separated using a Ficoll gradient. Plateletsctivation by thrombin (0.75 U/ml) was quantified by flow cytometryor P-selectin surface expression. Neutrophils and platelets were mixed:1 (v:v) and activated with thrombin. The mixture was sampled at 1, 5nd 10 min. Neutrophils and platelets were labeled with antibodies toD11b and b3, respectively, and neutrophil-platelet aggregates wereuantified by flow cytometry.

ESULTS: CO reduced platelet activation by thrombin (4.2% �.5% vs. 20.1% � 8.7% in RA treated platelets, 3 exp, P�0.03). Atll time points, neutrophil binding of platelets also was significantlyeduced in CO-treated vs. RA rats ( Table).

latelet-neutrophil Interactions are Inhibited by Inhaled CO

n Vivo Treatment % Neutrophils Staining for Platelets

1 min 5 min 10 min

O 21.6 � 5.6 45.6 � 7.5 35.5 � 3.6ir 52.5 � 10.4 76.1 � 5.3 71.2 � 5.6

ean % neutrophils with a platelet label � SEM of 3 separate experiments.

� 0.05 between RA and CO groups at all time points.

ISSN 1072-7515/08/$34.00