<p>UVOD: Procesi koji obuhvataju endotelnu disfunkciju, oksidativni stres, hroničnu inflamaciju, hiperaktivnost i aktivaciju trombocita te naru&scaron;avanje ravnoteže procesa koagulacije i fibrinolize od najranijih faza razvoja dijabetes melitusa tip 2 (T2DM) promovi&scaron;u aterogenezu i nastanak aterotromboznih komplikacija. Kompleksan terapijski pristup u T2DM ima za cilj ne samo uspostavljanje glikoregulacije, korekciju brojnih metaboličkih poremećaja i modifikaciju pridruženih faktora rizika za nastanak ateroskleroze već i primenu antitrombocitne terapije u cilju primarne ili sekundarne prevencije aterotromboznih komplikacija. Uprkos primenjenoj antiagregacionoj terapiji, deo bolesnika doživi rekurentne aterotrombozne atake. Bolesnici sa T2DM se izdvajaju kao grupa sa posebnim rizikom za recidivantne aterotromboze &scaron;to može biti uslovljeno rezistencijom na primenjenu antitrombocitnu terapiju. Praćenje efekata antitrombocitne terapije i blagovremeno identifikovanje rezistentnih bolesnika ima za cilj optimizaciju primenjene antitrombocitne terapije &scaron;to može biti od izuzetnog kliničkog značaja u smislu sprečavanja progresije aterotromboznog procesa. CILJ: Proceniti i uporediti nivoe biomarkera, pokazatelja endotelne aktivacije, aktivacije i agregabilnosti trombocita u bolesnika sa bole&scaron;ću arterijskih krvnih sudova u tipu 2 dijabetes melitusa u odnosu na njihove vrednosti u zdravoj populaciji. Uporediti efikasnost primenjene antitrombocitne terapije tienopiridinima u bolesnika sa tipom 2 dijabetes melitusa i bole&scaron;ću arterijskih krvnih sudova u odnosu na efikasnost ove terapije u nedijabetičnoj populaciji bolesnika sa bole&scaron;ću arterijskih krvnih sudova. MATERIJAL I METODE: U ispitivanje je uključeno 100 ispitanika oba pola, starosti od 33 do 70 godina života, kod kojih je prethodno utvrđeno postojanje neke od kliničkih manifestacija bolesti arterijskih krvnih sudova (IBS, CVB, PAB) koji kao antitrombocitnu terapiju uzimaju tienopiridinski preparat, klopidogrel. Od toga, 50 uključenih ispitanika imalo je dijagnozu dijabetes melitus tipa 2, a 50 su bili bolesnici bez dijabetesa. Kontrolnu grupu je činilo 30 klinički i biohemijski zdravih ispitanika, nepu&scaron;ača koji su prema polnoj i dobnoj strukturi odgovarali ispitivanim grupama bolesnika. Svim ispitanicima su urađena antropometrijska merenja, laboratorijska analiza uzoraka krvi na automatizovanim analizatorima sa određivanjem parametara metabolizma glukoze, lipida, parametera inflamacije, KKS, parmetara koagulacije i trombocitnih pokazatelja. Određivanje serumske koncentracije sE&ndash;selektina i sP-selektina je vr&scaron;eno ELISA tehnikom (R&amp;D Systems, Inc. Minneapolis, USA). Plazmatska koncentracija vWFAg-a određivana je imunoturbidimetrijskom metodom na koagulacionom analizatoru Siemens Healthcare Diagnostics, Nemačka. Agregabilnost trombocita je određivana impedantnom agregometrijom (Multiple Electrode Aggregometry - MEA) na Multiplate analizatoru, Dynabyte, Minhen, Nemačka. Bazalna agregabilnost trombocita procenjivana je TRAP testom, rezidualna agregabilnost trombocita pod terapijom klopidogrela ADP testom, rezidualna agregabilnost trombocita pod terapijom aspirina, ASPI testom. Individualni odgovor na primenjenu antiagregacionu terapiju je procenjivan i na osnovu procenta sniženja bazalne agregabilnosti trombocita (%SAT) nakon primenjene antiagregacione terapije &scaron;to je izračunato sledećim formulama: procena antiagregacionog efekta klopidogrela:%SATadp =100 x (1-ADP/TRAP) i procena antiagregacionog efekta aspirina:%SATaspi =100 x (1-ASPI/TRAP). REZULTATI: Nivo sE-slektina je bio signifikantno vi&scaron;i u bolesnika sa T2DM u odnosu na bolesnike bez dijabetesa (45,1&plusmn;18,1vs.31,8&plusmn;10,5ng/ml; p&lt;0,001) i kontrolnu grupu zdravih ispitanika (45,1&plusmn;18,1vs.27,2&plusmn;11,2ng/ml; p&lt;0,001). Plazmatski nivo vWF Ag, bio je statistički značajno vi&scaron;i u bolesnika sa T2DM u odnosu na grupu ispitanika bez dijabetesa (172&plusmn;75,2vs. 146&plusmn;40,6%; p=0,045), kao i u odnosu na kontrolnu grupu zdravih (172&plusmn;75,2vs.130&plusmn;33,8%; p=0,007). Nivo sPselektina bio je statistički značajno vi&scaron;i kod bolesnika s T2DM u odnosu na ispitanike u grupi dijabetesa (95,2&plusmn;31,8vs.84,0&plusmn;21,8 ng/ml; p=0,042) i kontrolnoj grupi (95,2&plusmn;31,8vs.76,7&plusmn;16,2ng/ml; p=0,004). Uočeno je da je %rP statistički bio značajno vi&scaron;i u grupi dijabetičara u odnosu na grupu ispitanika bez dijabetesa (3,47&plusmn;1,30vs.2,30&plusmn;1,30%; p&lt;0,001) i kontrolnu grupu zdravih (3,47&plusmn;1,30vs.2,29&plusmn;1,23%; p&lt;0,001). Bolesnici sa T2DM imali su statistički značajno vi&scaron;e vrednosti ADP testa (70,3&plusmn;22,0vs.56,9&plusmn;19,7U; p=0,002) u odnosu na bolesnike bez dijabetesa, a uočen je i značajno niži stepen procenta sniženja bazalne agregabilnosti, %SATadp, u dijabetičara u odnosu na ispitanike bez dijabetesa (31,6&plusmn;12,4vs. 48,6&plusmn;12,6 %; p&lt;0,001). U grupi ispitanika sa T2DM vrednost TRAP testa statistički značajno pozitivno koreli&scaron;e sa brojem neutrofila (r=0,349;p= 0,013) i NLR-om (r=0,472;p=0,001), a multivarijantnom linearnom regresionom analizom dokazana je nezavisna povezanost TRAP testa i fibrinogena (B=9,61;p=0,009). Takođe, u istoj ispitivanoj grupi postoji pozitivna povezanost ADP testa sa HOMAIR (r=0,319;p=0,024), NLR-om (r=0,515;p&lt;0,001), hsCRP-om (r=0,356;p=0,011), kao i sa %rP (r=0,302;p=0,049). Multivarijantnom linearnom regresionom analizom dokazana je nezavisna povezanost ADP testa i ITM (B=1,43;p=0,043). %SATadp u bolesnika sa T2DM negativno je korelisao sa ITM (r= -0,381;p=0,006), OS (r= - 0,387;p=0,006), HOMA-IR (r= -0,349;p=0,013), hsCRP-om (r= -0,288; p=0,043), %rP (r= -0,302;p=0,049), sE-selektinom (r= -0,369; p=0,008) i sP-selektinom (r= - 0,374;p=0,007). U grupi dijabetičara, postoji pozitivna povezanost %rP sa ITM (r=0,365;p= 0,016), OS (r=0,435;p=0,004), HOMA-IR (r=0,409;p=0,006), hsCRP (r=0,374;p=0,014), sP-selektinom (r=0,341;p=0,025) i vWFAg-om (r=0,348;p=0,022). Takođe, sE-selektin pozitivno koreli&scaron;e sa ITM (r=0,380;p =0,006), OS (r=0,380; p=0,007), HOMA-IR (r=0,339;p=0,016), hsCRP-om (r=0,351;p=0,013), a sP-selektin sa ITM (r=0,312;p=0,027), OS (r=0,395;p=0,005), HOMA-IR (r=0,286;p=0,044), hsCRP-om (r=0,369; p=0,008) i nivoom sE &ndash; selektina (r=0,560;p &lt;0,001). Evaluirajući odgovor na terapiju klopidogrelom u podgrupama bolesnika sa dijabetesom, napravljenim prema kvartilnoj distribuciji nivoa ADP-a, tj. stepenu rezidualne agregabilnosti trombocita u toku terapije klopidogrelom, uočeno je da ukupna bazalna agregabilnost trombocita procenjena TRAP testom statistički značajno raste od prvog do četvrtog kvartila (76,50 &plusmn;19,91 vs. 94,54&plusmn;16,67 vs. 112,00&plusmn;10,22 vs. 128,92&plusmn;15,69U;p&lt;0,001), dok se %SATadp od prvog do četvrtog kvartila značajno smanjivao (40,44&plusmn;13,33 vs. 31,20&plusmn;11,82 vs. 33,16&plusmn;7,03 vs. 21,53&plusmn;10,16%). ZAKLJUČAK: Koncentracije cirkuli&scaron;ućih biomarkera endotelne aktivacije, sE &ndash; selektina i vWF Ag-a, solubilnog biomarkera trombocitne aktivacije, sP &ndash; selektina, kao i procenat retikulisanih trombocita, %rP, markera trombocitnog prometa, značajno su povi&scaron;ene kod bolesnika sa bole&scaron;ću arterijskih krvnih sudova u tipu 2 dijabetes melitusa u odnosu na njihove koncentracije kod zdravih ispitanika i bolesnika bez dijabetesa. Bolesnici sa T2DM imali su znatno vi&scaron;i stepen rezistencije na antitrombocitnu terapiju klopidogrelom u odnosu na bolesnike bez dijabetesa, procenjene stepenom rezidualne agregabilnosti trombocita, ADP test, kao i procentom sniženja ukupne bazalne agregabilnosti trombocita, %SATadp, metodom impedantne agregometrije, a &scaron;to je uslovilo i trend učestalijeg ponavljanja ishemijskih ataka u odnosu na bolesnike bez dijabetesa. Međusobna povezanost ispitivanih biomarkera endotelne i trombocitne aktivacije (sE &ndash; selektina, vWF Aga, sP &ndash; selektina), kao i markera prometa trombocita (%rP) sa metaboličko inflamatornim parametrima i sa indikatorima odgovora na antiagregacionu terapiju, može ukazivati na to da nepovoljan metabolički milje dijabetičara može biti jedan od doprinosnih faktora lo&scaron;em odgovoru na antitrombocitnu terapiju klopidogrelom.</p> / <p>INTRODUCTION: Processes involving endothelial dysfunction, oxidative stress, chronic inflammation, platelet activation and the imbalance between coagulation and fibrinolysis promote atherogenesis and atherothrombotic complications at early stage of diabetes mellitus type 2 (T2DM). The complex therapeutic approach in T2DM aims not only to reestablish glycemic control and to correct a number of metabolic disorders, but also to achieve primary or secondary prevention of atherothrombotic complications. Despite the applied antiplatelet therapy, some patients experience recurrent atherothrombotic attacks. Patients with T2DM are the group at particular risk for recurrent atherothrombosis, which can be caused by antiplatelet therapy resistance. Monitoring the effectiveness of antiplatelet therapy and identification of resistant patients aims to optimize the applied antiplatelet therapy, which can be of great clinical significance in terms of preventing progression of atherotrombotic processes. AIM: Evaluate and compare the levels of biomarkers, indicators of endothelial activation, platelet activation and aggregability in patients with arterial vascular disease in type 2 diabetes mellitus compared to their values in a healthy population. Compare the effectiveness of applied antiplatelet therapy with thienopyridines in patients with type 2 diabetes mellitus and arterial vascular disease compared to the efficacy of this therapy in nondiabetic population of patients with arterial vascular disease. MATERIAL AND METHODS: The study included 100 patients, 33 to 70 years of age, with previously established existence of some of the clinical manifestations of arterial vascular disease (CAD, CVD, PAD), taking thienopyridine antiplatelet therapy with clopidogrel. 50 patients was previously diagnosed with diabetes mellitus type 2 and 50 were nondiabetic patients. Control group included 30 age and sex matched healthy participants, non-smokers. All subjects underwent anthropometric measurements and laboratory analysis of blood samples on automated analyzers with determining the parameters of glucose metabolism, lipids, inflammation parameters, complete blood count, coagulation and platelet parameters. Serum concentrations of sEselectin and sP-selectin were determined by ELISA (R&amp;D Systems, Inc., Minneapolis, USA). vWFAg was determined by immunoturbidimetry on coagulometer Siemens Healthcare Diagnostics, Germany. Platelet aggregability was determined by impedance aggregometry (Multiple Electrode Aggregometry - MEA) on Multiplate analyzer, Dynabyte, Munich, Germany. Basal platelet aggregability was estimated by TRAP test, residual platelet aggregability during clopidogrel treatment was estimated by ADP test and during aspirin treatement by ASPI test. Individual response to antiplatelet therapy was estimated by the percentage of decrease in basal platelet aggregability (%DPA) obtained after antiplatelet therapy, calculated bypresented formulas: %DPAadp =100 x (1-ADP/TRAP)and %DPAaspi =100 x (1- ASPI/TRAP). RESULTS: Concentration of sE-selectin was significantly higher in patients with T2DM in order to non-diabetic patients (45,1&plusmn;18,1vs.31,8&plusmn;10,5ng/ml;p&lt;0,001) and healthy control group (45,1&plusmn;18,1vs.27,2&plusmn;11,2ng/ml; p&lt;0,001). vWF Ag was significantly higher in diabetic patients than in non-diabetics (172&plusmn;75,2vs. 146&plusmn;40,6%; p=0,045) and healthy controls (172&plusmn;75,2vs.130&plusmn;33,8%; p=0,007). sP-selectin was also significantly higher in patients with T2DM than in non-diabetics (95,2&plusmn;31,8vs.84,0&plusmn;21,8 ng/ml; p=0,042) and healthy controls (95,2&plusmn;31,8vs.76,7&plusmn;16,2ng/ml; p=0,004). %rP was significantly higher in group of patients with T2DM than in nondiabetic patients (3,47&plusmn;1,30vs.2,30&plusmn;1,30%; p&lt;0,001) and healthy control group (3,47&plusmn;1,30vs.2,29&plusmn;1,23%; p&lt;0,001). T2DM patients had statistically higher values of ADP test (70,3&plusmn;22,0vs.56,9&plusmn;19,7U; p=0,002) compared to patients without diabetes, and significantly lower %DPAadp (31,6&plusmn;12,4vs. 48,6&plusmn;12,6 %; p&lt;0,001). In T2DM group of patients, level of TRAP test correlated positively with number of white blood cells (r=0,349;p= 0,013) and NLR (r=0,472;p=0,001), and multivariant linear regression analisys showed significant independent association of TRAP test with fibrinogen (B=9,61;p=0,009). Statistically significant positive correlation of ADP test with HOMA-IR (r=0,319;p=0,024), NLR (r=0,515;p&lt;0,001), hsCRP (r=0,356;p=0,011) and %rP (r=0,302;p=0,049) was observed in patients with T2DM. Multivariant linear regression analisys showed significant independent association of ADP test with BMI (B=1,43;p=0,043). %DPAadp negatively correlated with BMI (r=-0,381;p=0,006), WC (r= - 0,387;p=0,006), HOMA-IR (r= -0,349;p=0,013), hsCRP (r= -0,288; p=0,043), %rP (r= -0,302;p=0,049), sE-selectin (r= -0,369; p=0,008) and sP-selectin (r= -0,374;p=0,007) in diabetic patients. Significant positive correlation of %rP with BMI (r=0,365;p= 0,016), WC (r=0,435;p=0,004), HOMA-IR (r=0,409;p=0,006), hsCRP (r=0,374;p=0,014), sP-selectin (r=0,341;p=0,025) and vWFAg (r=0,348;p=0,022) was found in diabetics. Also, sE-selectin positively correlated with BMI (r=0,380;p =0,006), WC (r=0,380; p=0,007), HOMA-IR (r=0,339;p=0,016), hsCRP(r=0,351;p=0,013), and sPselectin correlated positively with BMI (r=0,312;p=0,027), WC (r=0,395;p=0,005), HOMA-IR (r=0,286;p=0,044), hsCRP (r=0,369; p=0,008) and sE &ndash; selectin (r=0,560;p &lt;0,001). Evaluating the response to clopidogrel therapy in subgrpoups of diabetic patients accoarding the quartile distribution of ADP test (clopidogrel on-treatment platelet reactivity), it is found that total basal aggregability estimated by TRAP test significantly increased from the first to the fourth quartile (76,50 &plusmn;19,91 vs. 94,54&plusmn;16,67 vs. 112,00&plusmn;10,22 vs. 128,92&plusmn;15,69U;p&lt;0,001) while %DPAadp decreased (40,44&plusmn;13,33 vs. 31,20&plusmn;11,82 vs. 33,16&plusmn;7,03 vs. 21,53&plusmn;10,16%). CONCLUSION: Concentration of circulating biomarkers of endothelial activation, sE-selectin and vWF Ag, soluble marker of platelet activation, sP &ndash; selectin, as well as percentage of reticulated platelets, %rP, marker of platelet turnover, were significantly higher in patients with arterial vascular disease in T2DM compared to healthy controls and non-diabetics. Patients with T2DM had significantly higher degree of resistance to antiplatelet therapy with clopidogrel compared to non diabetics, estimated by ADP test, as well as with %DPAadp, what caused more frequent recurrent ischemic attacks compared to nondiabetic patients. Correlation of biomarkers of endothelial and platelet activation (sE &ndash; selectin, vWF Ag, sP &ndash; selectin) and markers of platelet turnover (%rP) with metabolic profile indicators and poor antiplatelet therapy response suggest that altered metabolic profile can be one of contributing factors of poor antiplatelet response in diabetic patients.</p>

Lors du phénomène d’hémostase primaire ou de thrombose vasculaire, les plaquettes sanguines doivent adhérer aux parois afin de remplir leur fonction réparatrice ou pathologique. Pour ce faire, certains facteurs rhéologiques et hémodynamiques tels que l’hématocrite, le taux de cisaillement local et les contraintes de cisaillement pariétal, entrent en jeu afin d’exclure les plaquettes sanguines de l’écoulement principal et de les transporter vers le site endommagé ou enflammé. Cette exclusion pourrait aussi être influencée par l’agrégation de globules rouges qui est un phénomène naturel présent dans tout le système cardiovasculaire selon les conditions d’écoulement. La dérive de ces agrégats de globules rouges vers le centre des vaisseaux provoque la formation de réseaux d’agrégats dont la taille et la complexité varient en fonction de l’hématocrite et des conditions de cisaillement présentes. Il en résulte un écoulement bi-phasique avec un écoulement central composé d’agrégats de globules rouges avoisinés par une région moins dense en particules où l’on peut trouver des globules rouges singuliers, des petits rouleaux de globules rouges et une importante concentration en plaquettes et globules blancs. De ce fait, il est raisonnable de penser que plus la taille des agrégats qui occupent le centre du vaisseau augmente, plus il y aura de plaquettes expulsées vers les parois vasculaires. L'objectif du projet est de quantifier, in vitro, la migration des plaquettes sanguines en fonction du niveau d’agrégation érythrocytaire présent, en faisant varier l’hématocrite, le taux de cisaillement et en promouvant l’agrégation par l’ajout d’agents tels que le dextran à poids moléculaire élevé. Cependant, le comportement non Newtonien du sang dans un écoulement tubulaire peut être vu comme un facteur confondant à cause de son impact sur l’organisation spatiale des agrégats de globules rouges. De ce fait, les études ont été réalisées dans un appareil permettant de moduler, de façon homogène, la taille et la structure de ces agrégats et de quantifier ainsi leur effet sur la migration axiale des plaquettes. Du sang de porc anti coagulé a été ajusté à différents taux d’hématocrite et insérer dans un appareil à écoulement de Couette, à température ambiante. Les plaquettes sanguines, difficilement isolables in vitro sans en activer certains ligands membranaires, ont été remplacées par des fantômes en polystyrène ayant un revêtement de biotine. La quantification de la migration de ces fantômes de plaquettes a été réalisée grâce à l’utilisation de membranes biologiques fixées sur les parois internes de l’entrefer du rhéomètre de Couette. Ces membranes ont un revêtement de streptavidine assurant une très forte affinité d’adhésion avec les microparticules biotynilées. À 40% d’hématocrite, à un cisaillement de 2 s-1, 566 ± 53 microparticules ont été comptées pour un protocole préétabli avec du sang non agrégeant, comparativement à 1077 ± 229 pour du sang normal et 1568 ± 131 pour du sang hyper agrégeant. Les résultats obtenus suggèrent une nette participation de l’agrégation érythrocytaire sur le transport des fantômes de plaquettes puisque l’adhésion de ces derniers à la paroi du rhéomètre de Couette augmente de façon quasi exponentielle selon le niveau d’agrégation présent. / During the primary hemostatis or thrombosis phenomenon, the human blood platelets must adhere to the vascular wall in order for them to perform their repairing or pathological function. To do so, certain rheological and hemodynamic factors such as the hematocrit, local shear rate and the wall shear stress, must come into play to exclude blood platelets from the main blood stream and transport them to the vicinity of the damaged or inflamed site. This exclusion could also be influenced by red blood cell aggregation which is a natural process present throughout the entire cardiovascular system under certain flow conditions. The displacement of these rouleaux of red blood cells towards the centre of the vessel induces the formation of 3D networks of aggregates whose size and complexity vary as a function of the hematocrit and the shearing conditions present. It results in a two phase flow with an inner core composed of red blood cell aggregates surrounded by single red blood cells or small aggregates and large numbers of white blood cells and platelets. It is therefore reasonable to believe that the larger the inner core becomes, the more platelets will be expulsed towards the vascular wall. The objective of the study was to quantify, in vitro, the lateral migration of blood platelets as a function of the level of red blood cell aggregation present, by changing the hematocrit, the shear rate and by promoting red blood cell aggregation with the use of agents such as high molecular weight dextran. However, the non Newtonian behavior of blood in tube flow can be seen as a confounding factor to the understanding of the spatial organization of the red blood cell aggregates. In this study, whole blood was circulated in a simple shear flow apparatus, which allowed to homogeneously modulate the red blood cell aggregate sizes and structure, and quantify their effect on the axial migration of blood platelets. Anticoagulated porcine bloods were adjusted to different hematocrits and inserted into a Couette flow apparatus, at room temperature. Blood platelets, difficult to isolate in vitro without activating in a non reproducible manner specific membrane ligands, were replaced with biotin coated fluorescent polystyrene beads. The quantification of the migration of these platelet ghosts was conducted with the use of biological membranes fixed on the interior walls of the Couette apparatus. These streptavidin coated membranes ensure a strong adhesive affinity with the biotynilated beads. At 40% hematocrit and at a shear of 2 s-1, 566 ± 53 micro particles were counted for non aggregated erythrocytes, 1077 ± 229 for aggregating red blood cells and 1568 ± 131 for hyper aggregating blood. The results obtained suggest a strong participation of the red blood cell aggregation on the transport of platelet ghosts since the number of ghost cells fixed on the wall of the Couette rheometer increases almost exponentially with the level of aggregation present.

Sepse, a resposta do organismo a uma infecção, está associada a altas taxas de mortalidade. A razão pela qual um mecanismo protetor resulta num quadro clínico fatal permanece inexplicada. Em trabalho prévio nosso grupo demonstrou que exossomos de origem plaquetária são os mais freqüentes em plasma de pacientes com choque séptico e que estes podem induzir apoptose em células musculares lisas vasculares e células endoteliais em cultura. Demonstramos ainda que tais exossomos possuíam uma fonte enzimática de ROS, uma NADPH oxidase cuja atividade poderia estar associada à indução da apoptose (Janiszewski et al., 2004). No presente trabalho, nós buscamos criar um modelo de geração ex vivo de exossomos similares aos encontrados em pacientes sépticos e identificar possíveis vias responsáveis pela liberação destes e seus efeitos. Choque séptico é uma condição relacionada com exposição a lipopolissacarídeo (LPS) e geração de alta quantidade de trombina, TNF e espécies reativas de nitrogênio. Através de citometria de fluxo revelamos que plaquetas humanas expostas ao doador de NO dietilamina-NONOato e ao LPS geraram exossomos similares àqueles encontrados em pacientes com choque séptico, expondo alta quantidade de tetraspaninas CD9, CD63 e CD81 mas pouca fosfatidilserina. Por outro lado, plaquetas expostas à trombina ou TNF liberaram partículas com características claramente distintas, com alta exposição de fosfatidilserina e baixa de tetraspaninas. Assim como os exossomos sépticos, os exossomos obtidos pela exposição de NO e LPS geraram radical superóxido e NO, como demonstrado pela quimioluminescência da lucigenina (5M) e celenterazinina (5M) e pela fluorescência da 4,5-diaminofluoresceína (10mM) e 2,7-diclorofluoresceína (10mM). A análise por Western Blot nos permitiu identificar as subunidades Nox1, Nox2 e p22phox da NADPH oxidase e a isoforma induzível da enzima NO sintase (NOS) nesses exossomos. Como esperado, inibidores da NOS e da NADPH oxidase reduziram significamente os sinais fluorescentes e quimioluminescentes. Em adição, as células endoteliais em cultura expostas aos exossomos gerados por dietilamina-NONOato e LPS sofreram significativo aumento da taxa de apoptose quando comparadas àquelas expostas a exossomos controle. A inibição da NADPH oxidase assim como da NOS reduziu expressivamente tal efeito. Adição de urato (1mM), mostrou efeito aditivo sobre a inibição do sinal fluorescente, assim como redução adicional da taxa apoptótica, sugerindo papel importante do radical peroxinitrito. Nós propomos, assim, que exossomos derivados de plaquetas podem representar papel adicional no já complexo cenário da sinalização vascular redox. Nesse sentido, uma abordagem baseada em exossomos pode fornecer novas ferramentas para o entendimento e até tratamento da disfunção vascular na sepse / Sepsis, the bodys response to infection, is associated with high mortality rates. Why a protective mechanism turns into a deadly clinical picture is a matter of debate, and goes largely unexplained. In previous work we demonstrated that plateled derived exosomes are found in the plasma of septic patients with septic shock and can induce endothelial and vascular smooth muscle cell apoptosis in culture through an enzymatic superoxide source (Janiszewski et al., 2004). In this work we sought to create a model for ex vivo generation of exosomes, and to identify the pathways responsible for ROS release by exosomes and their effects. Septic shock is a condition related to exposure of lipopolysaccharide (LPS), generation of high amounts of thrombin, TNF and nitrogen reactive species. Through flow cytometry we demonstrated that human platelets exposed to the NO-donor diethylamine-NONOate, and to LPS, generated exosomes similar to those found in the blood of septic shock patients, with high exposure of the tetraspanin CD9, CD63, and CD81, but little phosphatidylserine. On the other hand, platelets exposed to thrombin or TNF released particles with clearly distinct characteristics, such as high phosphatidylserine and low tetraspanin. Like the septic exosomes, the exosomes obtained by NO and LPS exposure generated superoxide radical and NO, as disclosed by lucigenin and coelenterazine chemiluminescence and by 4,5-diaminofluorescein and 2,7-dichlorofluorescein fluorescence. Western Blot analysis revealed the presence of Nox1, Nox2 and p22phox NADPH oxidase subunits and the inducible isoform of NO synthase (NOS) in these exosomes. As expected, NOS inhibitors or NADPH oxidase inhibitors significantly reduced the fluorescence and chemiluminescente signals. In addition, endothelial cells exposed to NO or LPS generated exosomes underwent apoptotic death, while control exosomes had no effects on apoptosis. NADPH oxidase as well as NOS inhibition significantly reduced apoptosis rates. Concomitant generation of NO and superoxide suggests biological effects of the highly reactive radical peroxynitrite. In fact, the peroxynitrite scavenger urate (1 mM) showed an additive effect on fluorescent signal inhibition, as well as on endothelial apoptosis rate reduction. We thus propose that platelet-derived exosomes may be another class of actors in the complex play known as vascular redox signaling. In this sense, an exosome-based approach can provide novel tools for further understanding and even treating vascular dysfunction related to sepsis

Sepse, a resposta do organismo a uma infecção, está associada a altas taxas de mortalidade. A razão pela qual um mecanismo protetor resulta num quadro clínico fatal permanece inexplicada. Em trabalho prévio nosso grupo demonstrou que exossomos de origem plaquetária são os mais freqüentes em plasma de pacientes com choque séptico e que estes podem induzir apoptose em células musculares lisas vasculares e células endoteliais em cultura. Demonstramos ainda que tais exossomos possuíam uma fonte enzimática de ROS, uma NADPH oxidase cuja atividade poderia estar associada à indução da apoptose (Janiszewski et al., 2004). No presente trabalho, nós buscamos criar um modelo de geração ex vivo de exossomos similares aos encontrados em pacientes sépticos e identificar possíveis vias responsáveis pela liberação destes e seus efeitos. Choque séptico é uma condição relacionada com exposição a lipopolissacarídeo (LPS) e geração de alta quantidade de trombina, TNF e espécies reativas de nitrogênio. Através de citometria de fluxo revelamos que plaquetas humanas expostas ao doador de NO dietilamina-NONOato e ao LPS geraram exossomos similares àqueles encontrados em pacientes com choque séptico, expondo alta quantidade de tetraspaninas CD9, CD63 e CD81 mas pouca fosfatidilserina. Por outro lado, plaquetas expostas à trombina ou TNF liberaram partículas com características claramente distintas, com alta exposição de fosfatidilserina e baixa de tetraspaninas. Assim como os exossomos sépticos, os exossomos obtidos pela exposição de NO e LPS geraram radical superóxido e NO, como demonstrado pela quimioluminescência da lucigenina (5M) e celenterazinina (5M) e pela fluorescência da 4,5-diaminofluoresceína (10mM) e 2,7-diclorofluoresceína (10mM). A análise por Western Blot nos permitiu identificar as subunidades Nox1, Nox2 e p22phox da NADPH oxidase e a isoforma induzível da enzima NO sintase (NOS) nesses exossomos. Como esperado, inibidores da NOS e da NADPH oxidase reduziram significamente os sinais fluorescentes e quimioluminescentes. Em adição, as células endoteliais em cultura expostas aos exossomos gerados por dietilamina-NONOato e LPS sofreram significativo aumento da taxa de apoptose quando comparadas àquelas expostas a exossomos controle. A inibição da NADPH oxidase assim como da NOS reduziu expressivamente tal efeito. Adição de urato (1mM), mostrou efeito aditivo sobre a inibição do sinal fluorescente, assim como redução adicional da taxa apoptótica, sugerindo papel importante do radical peroxinitrito. Nós propomos, assim, que exossomos derivados de plaquetas podem representar papel adicional no já complexo cenário da sinalização vascular redox. Nesse sentido, uma abordagem baseada em exossomos pode fornecer novas ferramentas para o entendimento e até tratamento da disfunção vascular na sepse / Sepsis, the bodys response to infection, is associated with high mortality rates. Why a protective mechanism turns into a deadly clinical picture is a matter of debate, and goes largely unexplained. In previous work we demonstrated that plateled derived exosomes are found in the plasma of septic patients with septic shock and can induce endothelial and vascular smooth muscle cell apoptosis in culture through an enzymatic superoxide source (Janiszewski et al., 2004). In this work we sought to create a model for ex vivo generation of exosomes, and to identify the pathways responsible for ROS release by exosomes and their effects. Septic shock is a condition related to exposure of lipopolysaccharide (LPS), generation of high amounts of thrombin, TNF and nitrogen reactive species. Through flow cytometry we demonstrated that human platelets exposed to the NO-donor diethylamine-NONOate, and to LPS, generated exosomes similar to those found in the blood of septic shock patients, with high exposure of the tetraspanin CD9, CD63, and CD81, but little phosphatidylserine. On the other hand, platelets exposed to thrombin or TNF released particles with clearly distinct characteristics, such as high phosphatidylserine and low tetraspanin. Like the septic exosomes, the exosomes obtained by NO and LPS exposure generated superoxide radical and NO, as disclosed by lucigenin and coelenterazine chemiluminescence and by 4,5-diaminofluorescein and 2,7-dichlorofluorescein fluorescence. Western Blot analysis revealed the presence of Nox1, Nox2 and p22phox NADPH oxidase subunits and the inducible isoform of NO synthase (NOS) in these exosomes. As expected, NOS inhibitors or NADPH oxidase inhibitors significantly reduced the fluorescence and chemiluminescente signals. In addition, endothelial cells exposed to NO or LPS generated exosomes underwent apoptotic death, while control exosomes had no effects on apoptosis. NADPH oxidase as well as NOS inhibition significantly reduced apoptosis rates. Concomitant generation of NO and superoxide suggests biological effects of the highly reactive radical peroxynitrite. In fact, the peroxynitrite scavenger urate (1 mM) showed an additive effect on fluorescent signal inhibition, as well as on endothelial apoptosis rate reduction. We thus propose that platelet-derived exosomes may be another class of actors in the complex play known as vascular redox signaling. In this sense, an exosome-based approach can provide novel tools for further understanding and even treating vascular dysfunction related to sepsis

Trombocitopenia e diminuição da função plaquetária são achados comuns em pacientes picados por serpentes do gênero Bothrops. Sabe-se que o veneno de Bothrops jararaca (VBj) apresenta compostos com características pró e anti-agregantes plaquetárias, porém existem poucos estudos sobre a influência do veneno total assim como das principais famílias de proteínas que o compõem sobre as funções plaquetárias. A utilização de modelos experimentais é essencial para entender as desordens plaquetárias em humanos que culminam em sangramentos diversos. Portanto, o objetivo deste estudo foi (i) comparar as respostas ex vivo de plaquetas lavadas de humanos e de camundongos frente ao VBj, assim como entender a participação de serinaproteinases (SVSP) e metaloproteinases (SVMP) presentes no veneno sobre a agregação dessas plaquetas; e (ii) delimitar dentro do complexo proteico do veneno os compostos que induzem a trombocitopenia em camundongos após 3 horas do início do envenenamento botrópico. As plaquetas lavadas de humanos e camundongos BALB/c, C57BL/6 e do mutante natural pérola (Ap3b1-/-) apresentaram respostas de agregação máxima ao VBj na concentração de 24,4 ?g/mL, porém esta concentração provocou uma agregação menos intensa em plaquetas humanas quando comparada àquela observada nas linhagens BALB/c e C57BL/6. Mesmo em plaquetas de camundongos pérolas, deficientes em corpos densos plaquetários, o VBj se mostrou um potente agonista, promovendo a agregação plaquetária sem a necessidade da secreção do conteúdo granular. A ação agonista do veneno promoveu a secreção de ATP presente nos corpos densos plaquetários de humanos e das linhagens BALB/c e C57BL/6 de forma tão intensa quanto à provocada pela trombina, assim como a secreção de PF4 presente nos grânulos ? de plaquetas humanas e de camundongos BALB/c. Já em relação à secreção lisossomal, observou-se que as plaquetas humanas secretam níveis mais baixos de ?-hexosaminidase quando estimuladas com VBj do que pela trombina, enquanto que em plaquetas de camundongos BALB/c a secreção lisossomal ao VBj foi superior à constatada com a trombina. Os baixos níveis de lactato desidrogenase (LDH) no sobrenadante das plaquetas estudadas mostraram ausência de atividade direta citotóxica pelo VBj. Para verificar se as principais classes de famílias de enzimas do VBj, SVMP e SVSP, estavam envolvidas na ativação plaquetária ex vivo, elas foram inibidas com Na2EDTA (13 mM) e AEBSF (8 mM), respectivamente. Observou-se que em plaquetas humanas as serinaproteases são importantes para a agregação ex vivo, enquanto a agregação das plaquetas de camundongos BALB/c foi independente dessa classe de toxinas. Os resultados dos ensaios in vivo demonstraram que as proteínas do VBj com peso molecular inferior a 50 kDa (UF < 50 kDa) são importantes para o estabelecimento da trombocitopenia em camundongos BALB/c que receberam essa fração por via subcutânea e que esse quadro é independente de manifestações hemorrágicas e do desenvolvimento de coagulopatia durante o envenenamento botrópico. A caracterização dos compostos presentes no UF < 50 kDa foi realizada por espectrometria de massas e foi observada a presença predominante de metaloproteinases (37%) e proteínas similares às lectinas do tipo-C (33%), enquanto serinaproteases (17%), fosfolipases A2 (10%) e outros compostos (3%) somaram 30% da fração UF < 50 kDa. Em conclusão, o veneno é um potente agonista plaquetário que promove agregação, aglutinação e secreção de plaquetas humanas e de camundongos, independente da secreção de corpos densos plaquetários, e a fração do veneno responsável pela trombocitopenia em camundongos BALB/c tem peso molecular menor que 50 kDa / Thrombocytopenia and platelet dysfunction are common findings in patients bitten by Bothrops jararaca snakes. Pro- and anti-aggregating toxins have been isolated from Bothrops jararaca venom (BjV), but only few studies have been carried out about the effects of crude BjV and its main families of enzymes on platelet function ex vivo, as well as to understand their relevance to the pathophysiological events that occur during B. jararaca envenomation. Animal models have been used to understand platelet disorders in humans that culminate in bleeding manifestations. Thus, the aim of this study was to investigate (i) the effects of BjV, and snake venom serine proteinases (SVSP) and snake venom metalloproteinases (SVMP) contained therein, on aggregation and secretion in suspensions of washed human and mouse platelets, and (ii) to determine the BjV fractions, obtained by ultrafiltration, that induce thrombocytopenia in BALB/c mice after 3 h of administration of Bothrops envenomation. Washed platelets from humans and BALB/c, C57BL/6 and pearl (Ap3b1-/-) mice showed maximal aggregation responses to BjV at the concentration of 24.4 ?g/mL. However, this concentration aggregated less intensely platelets from humans than BALB/c or C57BL/6 mice. Even in pearl mouse platelets, which are deficient in dense bodies, BjV proved to be a potent agonist, promoting platelet aggregation without the requirement of granule content secretion. Nonetheless, BjV induced secretion of ATP, present in dense bodies, and PF4, present in ? granules, in the same extent as thrombin, from platelets of humans and mice. In regard to lysosomal secretion, it was observed that human platelets secreted low ?-hexosaminidase levels when stimulated by BjV than thrombin, whereas in BALB/c platelets higher secretion was induced by BjV than by thrombin. Release of lactate dehydrogenase (LDH) was similar between BjV and thrombin, evidencing the absence of cytotoxic activity by BjV on platelets. Inhibition of SVMP and SVSP, using Na2EDTA (13 mM) and AEBSF (8 mM), respectively, demonstrated that SVSP are important for ex vivo aggregation only in human platelets, whilst BALB/c platelet aggregation was independent of both of them. In in vivo studies, only BjV toxins with molecular weight less than 50 kDa (UF50) caused thrombocytopenia when administered s.c. to BALB/c mice, and it was independent of hemorrhagic manifestations and consumptive coagulopathy. Characterization by mass spectrometry of these toxins present in UF50 showed the predominant presence of SVMP (37%) and type-C lectin proteins (33%) were observed, while SVSP (17%), phospholipases A2 (10%) and other proteins (3%) accounted for the remaining toxins in UF50. In conclusion, BjV is a potent platelet activating agent that promotes aggregation, agglutination and secretion of human and mouse platelets, independent of secretion of dense platelet bodies, and the fraction of venom responsible for thrombocytopenia in BALB / c mice has a molecular weight less than 50 kDa

OBJETIVO El objetivo nuestro proyecto de investigación es demostrar si la presencia de plasma rico en plaquetas (PRP) autólogo, que aporta varios factores de crecimiento en proporciones fisiológicas, en la interfase injerto tendinoso-hueso modifica el proceso de reparación de los tejidos locales en nuestro modelo experimental. MATERIAL Y MÉTODO Diseñamos un estudio de tipo experimental, longitudinal y prospectivo. Diez conejos albinos de Nueva Zelanda son intervenidos en sus 2 extremidades traseras, en una se realiza la técnica Experimental aplicando PRP y la otra sirve de control, sin aplicar PRP . Una vez intervenidos, los animales son divididos en 2 grupos de 5 de forma aleatoria. Un grupo es sacrificado a la 2ª semana y el otro a la 4ª semana postintervención. El área quirúrgica fue estudiada macroscópica, radiográfica, histológica e inmunohistoquímicamente. RESULTADOS El estudio macroscópico y radiográfico de las piezas muestra la presencia de un área de reacción ósea de mayor tamaño en la zona de entrada del tendón en el interior del túnel óseo en el grupo Experimental sacrificado a la 4ª sem. respecto al resto de grupos. Microscópicamente, en ningún corte histológico, tanto de los grupos Control como Experimental, se observa la línea de separación basófila, denominada tidemark190 entre el fibrocartílago mineralizado y el no mineralizado. Si se evidenció la aparición de una mayor cantidad de los elementos tisulares fibrosos, cartilaginosos y osteoides, y un mayor grado de ordenación celular en el fibrocartílago y sustancia osteoide en los grupos Experimentales respecto a sus correspondientes grupos Control. Además se observa la aparición de zonas de anclaje hueso-tendón en dos extremidades del grupo Experimental sacrificado a la 4ª sem., no encontradas en ningún caso Control. En el estudio inmunohistoquímico no apreciamos diferencias en el patrón de distribución del colágeno tipo II entre los distintos grupos, aunque si existe una mayor área de tinción de colágeno tipo II en los grupos Experimentales respecto a sus correspondientes grupos Control, ya que la cantidad de tejido fibrocartilaginoso, en sus variadas formas de presentación, también es mayor en los grupos que recibieron PRP. CONCLUSIONES El análisis de los resultados concluye que macroscópica, radiográfica y microscópicamente, este estudio demuestra que la administración de PRP como fuente de FC afecta al proceso de reparación del autoinjerto tendinoso dentro de un túnel óseo en nuestro modelo experimental. El PRP aceleró la curación, anticipando en el tiempo la aparición de elementos celulares y tisulares propios de fases posteriores del proceso de cicatrización, y además incrementó la cantidad éstos. / EFFECT OF PLATELET RICH PLASMA IN THE BIOLOGIC INCORPORATION OF A TENDON GRAFT IN A BONE TUNNEL Objective: To study the effect of the platelet rich plasma (PRP) in the biological process of tendon healing inside a bone tunnel Material y Methods: We designed an experimental, longitudinal and prospective research study. Ten animals were operated on their back legs (one as Experimental group and the other as Control group). In the Experimental group the tendon of the internal gastrocnemius muscle was cut, infiltrated with PRP, placed in a tibial bone tunnel filled with PRP, and finally, fixed by a bioabsorbable screw. The same procedure was practiced in the Control group without the use of PRP. Five rabbits were sacrificed on the second week and five on the fourth week after surgery. The legs were evaluated macroscopic, radiographic, histologic and immunohistochemically. Results: The macroscopic and radiographic study of the pieces shows the presence of a larger bone reaction area in the entrance of the tendon within the bone tunnel in the Experimental group sacrificed on the fourth week compared to other groups. Microscopically, the "tidemark" isn’t observed between mineralized and unmineralized fibrocartilage in any group . The Experimental group presents a statistically significant greater amount of chondroid tissue, osteoid tissue and trabecular bone, both the second and fourth week. We observe continuity zones between tendinous fibers and bone in some cases of the Experimental group on the fourth week . Immunohistochemically, no appreciable differences in the distribution pattern of type II collagen between the groups could be seen, although there is a greater area of staining in the Experimental group compared to their corresponding Control group Conclusion: The analysis of results and assessment of the comparison established between the research groups concludes that macroscopic, radiographic and microscopically, this study demonstrates that administration of PRP affects the repair process of tendon autograft in a bone tunnel in our experimental model. The PRP accelerated the healing time anticipating the emergence of cellular and tissue elements characteristic of later stages of the healing process, and also increased the amount of them.

Lors du phénomène d’hémostase primaire ou de thrombose vasculaire, les plaquettes sanguines doivent adhérer aux parois afin de remplir leur fonction réparatrice ou pathologique. Pour ce faire, certains facteurs rhéologiques et hémodynamiques tels que l’hématocrite, le taux de cisaillement local et les contraintes de cisaillement pariétal, entrent en jeu afin d’exclure les plaquettes sanguines de l’écoulement principal et de les transporter vers le site endommagé ou enflammé. Cette exclusion pourrait aussi être influencée par l’agrégation de globules rouges qui est un phénomène naturel présent dans tout le système cardiovasculaire selon les conditions d’écoulement. La dérive de ces agrégats de globules rouges vers le centre des vaisseaux provoque la formation de réseaux d’agrégats dont la taille et la complexité varient en fonction de l’hématocrite et des conditions de cisaillement présentes. Il en résulte un écoulement bi-phasique avec un écoulement central composé d’agrégats de globules rouges avoisinés par une région moins dense en particules où l’on peut trouver des globules rouges singuliers, des petits rouleaux de globules rouges et une importante concentration en plaquettes et globules blancs. De ce fait, il est raisonnable de penser que plus la taille des agrégats qui occupent le centre du vaisseau augmente, plus il y aura de plaquettes expulsées vers les parois vasculaires. L'objectif du projet est de quantifier, in vitro, la migration des plaquettes sanguines en fonction du niveau d’agrégation érythrocytaire présent, en faisant varier l’hématocrite, le taux de cisaillement et en promouvant l’agrégation par l’ajout d’agents tels que le dextran à poids moléculaire élevé. Cependant, le comportement non Newtonien du sang dans un écoulement tubulaire peut être vu comme un facteur confondant à cause de son impact sur l’organisation spatiale des agrégats de globules rouges. De ce fait, les études ont été réalisées dans un appareil permettant de moduler, de façon homogène, la taille et la structure de ces agrégats et de quantifier ainsi leur effet sur la migration axiale des plaquettes. Du sang de porc anti coagulé a été ajusté à différents taux d’hématocrite et insérer dans un appareil à écoulement de Couette, à température ambiante. Les plaquettes sanguines, difficilement isolables in vitro sans en activer certains ligands membranaires, ont été remplacées par des fantômes en polystyrène ayant un revêtement de biotine. La quantification de la migration de ces fantômes de plaquettes a été réalisée grâce à l’utilisation de membranes biologiques fixées sur les parois internes de l’entrefer du rhéomètre de Couette. Ces membranes ont un revêtement de streptavidine assurant une très forte affinité d’adhésion avec les microparticules biotynilées. À 40% d’hématocrite, à un cisaillement de 2 s-1, 566 ± 53 microparticules ont été comptées pour un protocole préétabli avec du sang non agrégeant, comparativement à 1077 ± 229 pour du sang normal et 1568 ± 131 pour du sang hyper agrégeant. Les résultats obtenus suggèrent une nette participation de l’agrégation érythrocytaire sur le transport des fantômes de plaquettes puisque l’adhésion de ces derniers à la paroi du rhéomètre de Couette augmente de façon quasi exponentielle selon le niveau d’agrégation présent. / During the primary hemostatis or thrombosis phenomenon, the human blood platelets must adhere to the vascular wall in order for them to perform their repairing or pathological function. To do so, certain rheological and hemodynamic factors such as the hematocrit, local shear rate and the wall shear stress, must come into play to exclude blood platelets from the main blood stream and transport them to the vicinity of the damaged or inflamed site. This exclusion could also be influenced by red blood cell aggregation which is a natural process present throughout the entire cardiovascular system under certain flow conditions. The displacement of these rouleaux of red blood cells towards the centre of the vessel induces the formation of 3D networks of aggregates whose size and complexity vary as a function of the hematocrit and the shearing conditions present. It results in a two phase flow with an inner core composed of red blood cell aggregates surrounded by single red blood cells or small aggregates and large numbers of white blood cells and platelets. It is therefore reasonable to believe that the larger the inner core becomes, the more platelets will be expulsed towards the vascular wall. The objective of the study was to quantify, in vitro, the lateral migration of blood platelets as a function of the level of red blood cell aggregation present, by changing the hematocrit, the shear rate and by promoting red blood cell aggregation with the use of agents such as high molecular weight dextran. However, the non Newtonian behavior of blood in tube flow can be seen as a confounding factor to the understanding of the spatial organization of the red blood cell aggregates. In this study, whole blood was circulated in a simple shear flow apparatus, which allowed to homogeneously modulate the red blood cell aggregate sizes and structure, and quantify their effect on the axial migration of blood platelets. Anticoagulated porcine bloods were adjusted to different hematocrits and inserted into a Couette flow apparatus, at room temperature. Blood platelets, difficult to isolate in vitro without activating in a non reproducible manner specific membrane ligands, were replaced with biotin coated fluorescent polystyrene beads. The quantification of the migration of these platelet ghosts was conducted with the use of biological membranes fixed on the interior walls of the Couette apparatus. These streptavidin coated membranes ensure a strong adhesive affinity with the biotynilated beads. At 40% hematocrit and at a shear of 2 s-1, 566 ± 53 micro particles were counted for non aggregated erythrocytes, 1077 ± 229 for aggregating red blood cells and 1568 ± 131 for hyper aggregating blood. The results obtained suggest a strong participation of the red blood cell aggregation on the transport of platelet ghosts since the number of ghost cells fixed on the wall of the Couette rheometer increases almost exponentially with the level of aggregation present.

Indiana University-Purdue University Indianapolis (IUPUI) / Solid organ transplantation is limited by available donor allografts. Pig to human transplantation, xenotransplantation, could potentially solve this problem if physiologic and immunologic incompatibilities are overcome. Genetic modifications of pigs have proven valuable in the study of xenotransplantation by improving pig to human compatibility. More genetic targets must be identified for clinical success. First, this study examines platelet homeostasis incompatibilities leading to acute thrombocytopenia in liver xenotransplantation. Mechanisms for xenogeneic thrombocytopenia were evaluated using liver macrophages, Kupffer cells, leading to identification of CD18, beta-2 integrin, as a potential target for modification. When disruption of CD18 was accomplished, human platelet binding and clearance by pig Kupffer cells was inhibited. Further, human and pig platelet surface carbohydrates were examined demonstrating significant differences in carbohydrates known to be involved with platelet homeostasis. Carbohydrate recognition domains of receptors responsible for platelet clearance Macrophage antigen complex-1 (CD11b/CD18) and Asialoglycoprotein receptor 1 in pigs were found to be different from those in humans, further supporting the involvement of platelet surface carbohydrate differences in xenogeneic thrombocytopenia. Second, immunologic incompatibilities due to antibody recognition of antigens resulting in antibody-mediated rejection were studied. Identification of relevant targets was systematically approached through evaluation of a known xenoantigenic protein fibronectin from genetically modified pigs. N-Glycolylneuraminic acid, a sialic acid not found in humans, was expressed on pig fibronectin and was identified as an antigenic epitope recognized by human IgG. These studies have provided further insight into xenogeneic thrombocytopenia and antibody-mediated rejection, and have identified potential targets to improve pig to human transplant compatibility.

No / Cyclic adenosine monophosphate (cAMP)-dependent signaling modulates platelet function at sites of vascular injury. Here we show that thrombospondin-1 (TSP-1) prevents cAMP/protein kinase A (PKA) signaling through a CD36-dependent mechanism. Prostaglandin E(1) (PGE(1)) induced a robust inhibition of both platelet aggregation and platelet arrest under physiologic conditions of flow. Exogenous TSP-1 reduced significantly PGE(1)-mediated inhibition of both platelet aggregation and platelet arrest. TSP-1 prevented PGE(1)-stimulated cAMP accrual and phosphorylation of PKA substrates, through a mechanism requiring phosphodiesterase3A. TSP-1 also inhibited VASP phosphorylation stimulated by the nonhydrolyzable cAMP analog, 8-bromo-cAMP, indicating that it may regulate cAMP-mediated activation of PKA. The inhibitory effect of TSP-1 on cAMP signaling could be reproduced with a peptide possessing a CD36 binding sequence of TSP-1, while the effects of TSP-1 were prevented by a CD36 blocking antibody. TSP-1 and the CD36 binding peptide induced phosphorylation of Src kinases, p38 and JNK. Moreover, inhibition of Src kinases blocked TSP-1-mediated regulation of cAMP concentrations and the phosphorylation of VASP, indicating that TSP-1 modulated the cAMP/PKA signaling events through a tyrosine kinase-dependent pathway downstream of CD36. These data reveal a new role for TSP-1 in promoting platelet aggregation through modulation of the cAMP-PKA signaling pathway.