scholarly journals Lyophilized Human Platelets Restore Hemostasis in the Presence of the P2Y12 Inhibitors Cangrelor, Ticagrelor and Clopidogrel

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 25-25
Author(s):  
Matthew Dickerson ◽  
Amber Lee ◽  
Anne Hale ◽  
Keith A. Moskowitz
Keyword(s):  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Human Platelets ◽  
In Vivo Studies ◽  
Thrombotic Risk ◽  
P2y12 Inhibitor ◽  
P2y12 Inhibitors ◽  
P2y12 Antagonists

• Background: P2Y12 inhibitors block platelet ADP receptors thereby reducing clotting capacity. In an emergency, these agents must be reversed or therapeutically overcome to stop bleeding. Additionally, prior to and during elective procedures these inhibitors must be withdrawn, thereby increasing thrombotic risk. Lyophilized human platelets (Thrombosomes®) are stabilized platelet derived hemostatic agents currently under Phase 2 clinical development for thrombocytopenia and have potential as antiplatelet reversal agents. • Aims: The aim of this study was to determine if lyophilized human platelets are resistant to the antiplatelet effect of P2Y12 inhibitors and therefore restore hemostasis in the presence of P2Y12 inhibitors. • Methods: Fresh drawn platelet rich plasma (PRP) was treated with pharmacological concentrations of P2Y12 inhibitors cangrelor or ticagrelor and confirmed to inhibit ADP-stimulated aggregation on the PAP-8E Platelet Aggregometer. Changes in hemostatic properties of the P2Y12 inhibitor treated PRP were also tested under shear force on the Total Thrombus formation Analysis System (T-TAS®). P2Y12 inhibitor treated PRP samples were dosed with lyophilized platelets and tested for return of hemostatic properties by T-TAS. NOD SCID mice were used in a tail snip model to determine hemostatic efficacy of Thrombosomes® after super pharmacological doses of clopidogrel treatment. • Results: Fresh PRP derived platelet aggregation response to ADP was inhibited by cangrelor or ticagrelor whereas lyophilized platelets did not respond to either inhibitor. Normal thrombus formation of PRP as measured by T-TAS occurred at 19.5± 1.5 minutes (n=4) but increases to 28.0±3.0 minutes with cangrelor (n=4) or 28.0±3.0 minutes with ticagrelor (n=5) treatment. The addition of 150k/µL lyophilized platelets to P2Y12-inhibited PRP reduced time to thrombus formation to lower than PRP alone; 15.5 ±0.5 minutes in the presence of cangrelor (n=3) versus 17.5 ±1.5 minutes in the presence of ticagrelor (n=5). In the in vivo tail snip mouse model animals treated with super pharmacological dose of clopidogrel bled for 18.0±10.0 minutes (n=5) unlike those not treated that only bleed for 9.5±2.5 minutes (n=6). Lyophilized platelet treated clopidogrel animals stopped bleeding at 12.5 ±4.5 minutes (n=5) after tail snip. • Conclusion: Lyophilized human platelets, unlike normal platelets were resistant to the antiplatelet effects of P2Y12 inhibitors. In vitro and in vivo studies reveal that lyophilized human platelets can be used to recover the anti-thrombotic effect of P2Y12 antagonists, potentially allowing continued drug compliance prior to elective procedures and as a possible treatment for emergent acute bleeding while on P2Y12 antagonist therapy. Disclosures Dickerson: Cellphire Inc.: Current Employment. Lee:Cellphire, Inc.: Current Employment. Hale:Cellphire: Current Employment. Moskowitz:Cellphire Inc.: Current Employment.

A Comparison of the in Vitro and in Vivo Thrombogenic Activity of Factor IX Concentrates Using Stasis (Wessler) and Non-Stasis Rabbit Models

1980 ◽  
Vol 44 (02) ◽  
pp. 081-086 ◽  
Author(s):  
C V Prowse ◽  
A E Williams
Keyword(s):  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Factor Ix ◽  
Coagulation System ◽  
In Vitro Tests ◽  
Clinical Use ◽  
Low Activity

SummaryThe thrombogenic effects of selected factor IX concentrates were evaluated in two rabbit models; the Wessler stasis model and a novel non-stasis model. Concentrates active in either the NAPTT or TGt50 in vitro tests of potential thrombogenicity, or both, caused thrombus formation in the Wessler technique and activation of the coagulation system in the non-stasis model. A concentrate with low activity in both in vitro tests did not have thrombogenic effects in vivo, at the chosen dose. Results in the non-stasis model suggested that the thrombogenic effects of factor IX concentrates may occur by at least two mechanisms. A concentrate prepared from platelet-rich plasma and a pyrogenic concentrate were also tested and found to have no thrombogenic effect in vivo.These studies justify the use of the NAPTT and TGt50 in vitro tests for the screening of factor IX concentrates prior to clinical use.

Transplantation of Adipose-derived Cells for Periodontal Regeneration: A Systematic Review

2019 ◽  
Vol 14 (6) ◽  
pp. 504-518 ◽  
Author(s):  
Dilcele Silva Moreira Dziedzic ◽  
Bassam Felipe Mogharbel ◽  
Priscila Elias Ferreira ◽  
Ana Carolina Irioda ◽  
Katherine Athayde Teixeira de Carvalho
Keyword(s):  
Systematic Review ◽  
Animal Models ◽  
Platelet Rich Plasma ◽  
Periodontal Regeneration ◽  
In Vitro Studies ◽  
In Vivo Studies ◽  
Cell Sources ◽  
Study Designs

This systematic review evaluated the transplantation of cells derived from adipose tissue for applications in dentistry. SCOPUS, PUBMED and LILACS databases were searched for in vitro studies and pre-clinical animal model studies using the keywords “ADIPOSE”, “CELLS”, and “PERIODONTAL”, with the Boolean operator “AND”. A total of 160 titles and abstracts were identified, and 29 publications met the inclusion criteria, 14 in vitro and 15 in vivo studies. In vitro studies demonstrated that adipose- derived cells stimulate neovascularization, have osteogenic and odontogenic potential; besides adhesion, proliferation and differentiation on probable cell carriers. Preclinical studies described improvement of bone and periodontal healing with the association of adipose-derived cells and the carrier materials tested: Platelet Rich Plasma, Fibrin, Collagen and Synthetic polymer. There is evidence from the current in vitro and in vivo data indicating that adipose-derived cells may contribute to bone and periodontal regeneration. The small quantity of studies and the large variation on study designs, from animal models, cell sources and defect morphology, did not favor a meta-analysis. Additional studies need to be conducted to investigate the regeneration variability and the mechanisms of cell participation in the processes. An overview of animal models, cell sources, and scaffolds, as well as new perspectives are provided for future bone and periodontal regeneration study designs.

Abstract 13598: The G-protein BetaGamma Subunits Regulate Platelet Function

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Ahmed Alarabi ◽  
Zubair Karim ◽  
Victoria Hinojos ◽  
Patricia A Lozano ◽  
Keziah Hernandez ◽  
...  
Keyword(s):  
G Protein ◽  
Platelet Function ◽  
Thrombus Formation ◽  
Human Platelets ◽  
Inhibitory Effects ◽  
Clot Retraction ◽  
Betagamma Subunits

Platelet activation involves tightly regulated processes to ensure a proper hemostasis response, but when unbalanced, can lead to pathological consequences such as thrombus formation. G-protein coupled receptors (GPCRs) regulate platelet function by interacting with and mediating the response to various physiological agonists. To this end, an essential mediator of GPCR signaling is the G protein Gαβγ heterotrimers, in which the βγ subunits are central players in downstream signaling pathways. While much is known regarding the role of the Gα subunit in platelet function, that of the βγ remains poorly understood. Therefore, we investigated the role of Gβγ subunits in platelet function using a Gβγ (small molecule) inhibitor, namely gallein. We observed that gallein inhibits platelet aggregation and secretion in response to agonist stimulation, in both mouse and human platelets. Furthermore, gallein also exerted inhibitory effects on integrin αIIbβ3 activation and clot retraction. Finally, gallein’s inhibitory effects manifested in vivo , as documented by its ability to modulate physiological hemostasis and delay thrombus formation. Taken together, our findings demonstrate, for the first time, that Gβγ directly regulates GPCR-dependent platelet function, in vitro and in vivo . Moreover, these data highlight Gβγ as a novel therapeutic target for managing thrombotic disorders.

Arginine vasopressin release from human platelets after irreversible aggregation

1990 ◽  
Vol 78 (1) ◽  
pp. 113-116 ◽  
Author(s):  
Giovanni Anfossi ◽  
Elena Mularoni ◽  
Mariella Trovati ◽  
Paola Massucco ◽  
Luigi Mattiello ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Arginine Vasopressin ◽  
Platelet Rich Plasma ◽  
Human Platelets ◽  
Vasopressin Release ◽  
Irreversible Aggregation ◽  
Local Release

1. The release of arginine vasopressin from human platelets was investigated in platelet-rich plasma after irreversible aggregation induced by adenosine 5′-pyrophosphate, collagen, sodium arachidonate, thrombin and adrenaline in vitro. 2. Arginine vasopressin levels were significantly higher in the supernatant from stimulated platelet-rich plasma than from unstimulated samples, reaching 3.5 × 10−12 (range 1.6–12.5 × 10−12) mol/l in the absence of an aggregating agent, 8.8 × 10−12 (range 4.2–17.5 × 10−12) mol/l after adenosine 5′-pyrophosphate, 13.7 × 10−12 (2.2–63.2 × 10−12) mol/l after collagen, 7.8 × 10−12 (2.2–14.6 × 10−12) mol/l after sodium arachidonate, 7.8 × 10−12 (2.2–16.3 × 10−12) mol/l after thrombin and 12.2 × 10−12 (4.8–32.1 × 10−12) mol/l after adrenaline. 3. An arginine vasopressin level of 18 × 10−12 mol/l, which can be achieved physiologically, increased the sensitivity of platelets to adenosine 5′-pyrophosphate and collagen in vitro; the same concentration of arginine vasopressin caused a potentiation of the effect of catecholamines on the response of platelets to sodium arachidonate. 4. These results indicate that intraplatelet arginine vasopressin is released during aggregation and suggest that a local release of arginine vasopressin could occur after complete platelet aggregation in vivo.

Comparative lyophilized platelet-rich plasma wafer and powder for wound-healing enhancement: formulation, in vitro and in vivo studies

2019 ◽  
Vol 45 (8) ◽  
pp. 1379-1387 ◽  
Author(s):  
Ghada E. Yassin ◽  
Marwa H. S. Dawoud ◽  
Reham Wasfi ◽  
Ahmed Maher ◽  
Ahmed M. Fayez
Keyword(s):  
Wound Healing ◽  
Platelet Rich Plasma ◽  
In Vivo Studies

scholarly journals IκB kinase 2 is not essential for platelet activation

2020 ◽  
Vol 4 (4) ◽  
pp. 638-643
Author(s):  
Manuel Salzmann ◽  
Sonja Bleichert ◽  
Bernhard Moser ◽  
Marion Mussbacher ◽  
Mildred Haase ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Active Site ◽  
Bleeding Time ◽  
Thrombus Formation ◽  
Human Platelets ◽  
Iκb Kinase ◽  
Specific Deletion

Abstract Platelets are small anucleate cells that release a plethora of molecules to ensure functional hemostasis. It has been reported that IκB kinase 2 (IKK2), the central enzyme of the inflammatory NF-κB pathway, is involved in platelet activation, because megakaryocyte/platelet-specific deletion of exons 6 and 7 of IKK2 resulted in platelet degranulation defects and prolonged bleeding. We aimed to investigate the role of IKK2 in platelet physiology in more detail, using a platelet-specific IKK2 knockout via excision of exon 3, which makes up the active site of the enzyme. We verified the deletion on genomic and transcriptional levels in megakaryocytes and were not able to detect any residual IKK2 protein; however, platelets from these mice did not show any functional impairment in vivo or in vitro. Bleeding time and thrombus formation were not affected in platelet-specific IKK2-knockout mice. Moreover, platelet aggregation, glycoprotein GPIIb/IIIa activation, and degranulation were unaltered. These observations were confirmed by pharmacological inhibition of IKK2 with TPCA-1 and BMS-345541, which did not affect activation of murine or human platelets over a wide concentration range. Altogether, our results imply that IKK2 is not essential for platelet function.

Anticoagulant and antithrombotic properties of platelet protease nexin-1

Blood ◽  
2010 ◽  
Vol 115 (1) ◽  
pp. 97-106 ◽  
Author(s):  
Yacine Boulaftali ◽  
Frédéric Adam ◽  
Laurence Venisse ◽  
Véronique Ollivier ◽  
Benjamin Richard ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Thrombus Formation ◽  
Human Platelets ◽  
Platelet Surface ◽  
Type Plasminogen Activator ◽  
Healthy Donors ◽  
Protease Nexin ◽  
Deficient Mice

AbstractProtease nexin–1 (PN-1) is a serpin that inhibits plasminogen activators, plasmin, and thrombin. PN-1 is barely detectable in plasma but is expressed by platelets. Here, we studied platelet PN-1 in resting and activated conditions and its function in thrombosis. Studies on human platelets from healthy donors and from patients with a Gray platelet syndrome demonstrate that PN-1 is present both at the platelet surface and in α-granules. The role of PN-1 was investigated in vitro using human platelets incubated with a blocking antibody and using platelets from PN-1–deficient mice. Both approaches indicate that platelet PN-1 is active on thrombin and urokinase-type plasminogen activator. Blockade and deficiency of platelet PN-1 result in accelerated and increased tissue factor-induced thrombin generation as indicated by calibrated automated thrombography. Moreover, platelets from PN-1–deficient mice respond to subthreshold doses of thrombin, as assessed by P-selectin expression and platelet aggregation. Thrombus formation, induced ex vivo by collagen in blood flow conditions and in vivo by FeCl3-induced injury, is significantly increased in PN-1–deficient mice, demonstrating the antithrombotic properties of platelet PN-1. Platelet PN-1 is thus a key player in the thrombotic process, whose negative regulatory role has been, up to now, markedly underestimated.

Thrombostatin Inhibits Induced Canine Coronary Thrombosis

1999 ◽  
Vol 82 (09) ◽  
pp. 1182-1187 ◽  
Author(s):  
Ahmed Hasan ◽  
Sam Rebello ◽  
Edward Smith ◽  
Sujata Srikanth ◽  
Steven Werns ◽  
...  
Keyword(s):  
Coronary Artery ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Coronary Thrombosis ◽  
Human Platelets ◽  
Coronary Artery Thrombosis ◽  
Electrolytic Injury ◽  
Protease Activated Receptor 1

SummaryThrombostatin (RPPGF), an angiotensin converting enzyme metabolite of bradykinin, is an inhibitor of α-thrombin’s ability to activate platelets. We examined the in vivo pharmacokinetics and pharmacodynamics of thrombostatin in rabbits and its ability to inhibit coronary thrombosis induced by electrolytic injury in dogs. Plasma half-life of thrombostatin had a t1/2α of 2.6 min and a t1/2β of 24 min in rabbits. Ligating the renal arteries did not prolong clearance (t1/2α = 2.4 min; t1/2β = 12 min). Thrombostatin produced a prolonged in vivo antiplatelet effect. At 30 min after a single intravenous administration in rabbits, thrombostatin’s plasma concentration was <8.7 μM (5 μg/ml). However, ex vivo 20 and 40 nM γ-thrombin-induced platelet aggregation of these rabbits’ platelets was inhibited 40% for 2.75 and 1 h, respectively. In vitro, flow cytometry studies revealed that thrombostatin specifically bound to human platelets and washed human platelets treated with thrombostatin were less responsive to γ-thrombin than control platelets. Using electrolytic injury to induce coronary artery thrombosis, dogs treated with thrombostatin, aspirin, or combined thrombostatin and aspirin occluded in 62 ± 25 (mean ± SD), 62 ± 36, or 89 ± 32 min versus untreated animals which occluded at 39 ± 27 min, (p <0.01, p <0.01 and p <0.001, respectively). These studies show that thrombostatin binds to platelets and can delay coronary occlusion in vivo. Abbreviations: RPPGF: thrombostatin; PAR1: protease activated receptor 1, the first cloned thrombin receptor; PRP: platelet-rich plasma; PPP: plateletpoor plasma; LCX: left circumflex coronary artery; APTT: activated partial thromboplastin time; PT: prothrombin time

Inhibitory Effect of Piracetam on Platelet-rich Thrombus Formation in an Animal Model

1998 ◽  
Vol 79 (01) ◽  
pp. 222-227 ◽  
Author(s):  
F. Stockmans ◽  
W. Deberdt ◽  
Å. Nyström ◽  
E. Nyström ◽  
J. M. Stassen ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Peak Plasma ◽  
Thrombus Formation ◽  
Plasma Concentrations ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Cell Deformability

SummaryIntravenous administration of piracetam to hamsters reduced the formation of a platelet-rich venous thrombus induced by a standardised crush injury, in a dose-dependent fashion with an IC50 of 68 ± 8 mg/kg. 200 mg/kg piracetam also significantly reduced in vivo thrombus formation in rats. However, in vitro aggregation of rat platelets was only inhibited with piracetam-concentrations at least 10-fold higher than plasma concentrations (6.2 ± 1.1 mM) obtained in the treated animals. No effects were seen on clotting tests.In vitro human platelet aggregation, induced by a variety of agonists, was inhibited by piracetam, with IC50’s of 25-60 mM. The broad inhibition spectrum could be explained by the capacity of piracetam to prevent fibrinogen binding to activated human platelets. Ex vivo aggregations and bleeding times were only minimally affected after administration of 400 mg/kg piracetam i.v. to healthy male volunteers, resulting in peak plasma levels of 5.8 ± 0.3 mM.A possible antiplatelet effect of piracetam could be due to the documented beneficial effect on red blood cell deformability leading to a putative reduction of ADP release by damaged erythrocytes. However similarly high concentrations were needed to prevent stirring-induced “spontaneous” platelet aggregation in human whole blood.It is concluded that the observed antithrombotic action of piracetam cannot satisfactorily be explained by an isolated direct effect on platelets. An additional influence of piracetam on the rheology of the circulating blood and/or on the vessel wall itself must therefore be taken into consideration.

Anti-thrombotic effects of selective estrogen receptor modulator tamoxifen

2011 ◽  
Vol 106 (10) ◽  
pp. 624-635 ◽  
Author(s):  
Manasa Nayak ◽  
Sunil Singh ◽  
Arnab Roy ◽  
Vivek Prakash ◽  
Anand Kumar ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Present Report ◽  
Protein S ◽  
Collagen Matrix ◽  
Cancer Drug ◽  
Receptor Modulator

SummaryTamoxifen is a known anti-cancer drug and established estrogen receptor modulator. Few clinical studies have earlier implicated the drug in thrombotic complications attributable to lower anti-thrombin and protein S levels in plasma. However, action of tamoxifen on platelet signalling machinery has not been elucidated in detail. In the present report we show that tamoxifen is endowed with significant inhibitory property against human platelet aggregation. From a series of in vivo and in vitro studies tamoxifen was found to inhibit almost all platelet functions, prolong tail bleeding time in mouse and profoundly prevent thrombus formation at injured arterial wall in mice, as well as on collagen matrix perfused with platelet-rich plasma under arterial shear against the vehicle dimethylsulfoxide (DMSO). These findings strongly suggest that tamoxifen significantly downregulates platelet responses and holds potential as a promising anti-platelet / anti-thrombotic agent.

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