Jerome M. Teitel

Phosphatidylserine exposure and other apoptotic-like events in Bernard-Soulier syndrome platelets†

In the Bernard‐Soulier syndrome (BSS), the giant platelets are said to have increased phosphatidylserine (PS) surface exposure in the resting state and shortened survival in the circulation. When normal platelets are activated, they undergo many biochemical and morphological changes, some of which are apoptotic. Herein, we investigated apoptotic‐like events in BSS platelets upon activation, specifically, PS exposure, microparticle (MP) formation, cell shrinkage, and loss of mitochondrial inner membrane potential (ΔΨm). Platelets from two unrelated BSS patients were examined in whole blood; agonists used were collagen, thrombin, PAR1‐ or PAR4‐activating peptides (APs), or combinations of collagen with thrombin, and the PAR‐APs. Flow cytometry was used to measure PS exposure (annexin A5 binding), platelet‐derived MPs (forward scatter; events <0.75 μm size), and ΔΨm (TMRM fluorescence). PS exposure was increased on resting and activated BSS platelets, and this was independent of the platelet size. MP formation by BSS platelets was generally enhanced. Cell shrinkage occurred on activation to form smaller, PS‐exposing platelets in BSS and controls. A proportion of PS‐exposing BSS and control platelets exhibited ΔΨm loss, but unlike controls, there was also loss of ΔΨm in the BSS platelets not exposing PS. Thus, BSS platelets undergo apoptotic‐like events upon activation, with PS exposure and MP formation being enhanced. These events may play a role in the shortened survival in BSS, as well as affecting thrombin generation. Am. J. Hematol. 85:584–592, 2010.

Thrombin-activatable fibrinolysis inhibitor (TAFI): a novel predictor of angiographic coronary restenosis

The fibrinolytic system is closely related to several processes that are involved in restenosis. We previously showed that low PAI-1 plasma levels predicted restenosis. Recently, a different fibrinolytic inhibitor, TAFI, has been described. The aims of this study were to evaluate the relationship between pre-procedural plasma levels of TAFI and late angiographic restenosis and the interaction between TAFI and PAI-1.We prospectively studied 159 patients with stable angina who underwent successful elective angioplasty or stenting of de novo native coronary artery lesions. TAFI and PAI-1 antigen levels were measured in plasma samples drawn before the procedure. Follow-up coronary angiography was performed in 92% of patients. There was a significant correlation between pre-procedural TAFI levels and 6-month % diameter stenosis (DS) (r = 0.21; p = 0.013). The overall angiographic restenosis rate (DS>50%) was 31%. Pre-procedural TAFI levels were significantly higher in patients with restenosis (108 +/- 33% versus 94+/-30%, p = 0.011). Restenosis rates for patients in the upper tertile of TAFI levels were 2-fold higher than for those in the lowest tertile (45% versus 22%; p = 0.016). A combination of high TAFI and low PAI-1 levels identified patients at the highest risk of restenosis (53%) compared to 14% in patients with low TAFI and high PAI-1 levels; p = 0.027. In conclusion, pre-procedural plasma TAFI antigen levels identify patients at increased risk for restenosis after PCI.

Viral safety of haemophilia treatment products.

The epidemics of HIV and hepatitis C in treated haemophiliacs spurred rapid technological advances in the viral safety of clotting factor concentrates produced from large donor pools. Sequential steps are now employed to minimize infectious risks. The initial viral burden is reduced by screening donors and by testing individual donations and plasma pools for antivirus antibodies, viral antigens, and nucleic acid. These techniques are supplemented by nonspecific viral reduction steps based on physical partitioning and inactivation of pathogens by physical (eg, heat) or chemical (eg, solvent-detergent) means. Although these processes have virtually eliminated the transmission of HIV and hepatitis B and C, there is still evidence that concentrates can transmit small nonenveloped viruses, such as parvovirus B19 and hepatitis A virus. Furthermore, new agents which may not be susceptible to current viral inactivation procedures continue to be identified. Concerns such as these have also given impetus to the development of recombinant clotting factor proteins. Recombinant factor IX concentrate is now produced without the use of human plasma proteins at any step in the manufacturing or formulation process. In practice, the risk of viral transmission by clotting factor concentrates is now so remote that any manipulations to further reduce this risk may be counter-productive, by enhancing cost (hence compromising availability) and potentially promoting other adverse effects such as immunogenicity.

Platelet activation induced by porcine factor VIII (HYATE:C)

We studied the effects of porcine factor VIII (P‐FVIII; Hyate:C) and other coagulation products employed in the management of patients with hemophilia A, on platelet activation in vitro. Exposure of normal resting platelets to P‐FVIII resulted in platelet activation, as manifested by increased expression of the platelet surface activation markers CD62, CD63, and activated‐GPIIbIIIa, and by activation‐induced modulation of expression of normal platelet membrane glycoproteins CD41, CD42, and CD36. In contrast, platelet activation was not observed after exposure of the platelets to human FVIII, FEIBA, recombinant FVIIa, or cryosupernatant plasma. As with thrombin, exposure of platelets to P‐FVIII resulted in the generation of platelet microparticles, an effect not seen not with the other products. In contrast to the characteristic reduction in expression in the number of CD42 molecules detected on thrombin‐activated platelets, P‐FVIII‐stimulated platelets showed a small increase in CD42 expression. In contrast to thrombin, P‐FVIII did not cause platelet dense granule release. The results indicate that therapeutic P‐FVIII activates platelets, likely in ways that are different from the platelet activation seen with thrombin. The observed platelet activation and microparticle generation may provide a “hypercoagulable” mechanism for hemostasis with P‐FVIII therapy separate from, and additional to, that due to increased circulating FVIII levels. Am. J. Hematol. 57:200–205, 1998.

Vascular Injury and Thrombotic Potential: A Note of Caution About Recombinant Factor VIIa

Postoperative hemorrhage following cardiac surgery increases morbidity, mortality, and costs. Several case reports have described the successful use of recombinant factor VIIa to decrease or stop bleeding in patients undergoing cardiac surgery. The mechanism of action of recombinant factor VIIa is thought to be increased site-specific thrombin generation by tissue factor—mediated activation of coagulation or from activated platelets. However, there have also been many reports of thrombotic complications after recombinant factor VIIa administration. Randomized clinical trials and further laboratory studies should help better clarify the efficacy, safety, cost-effectiveness, and optimal dosing of recombinant factor VIIa in the cardiac surgical setting.

A 24-year-old woman with heavy menstrual bleeding

A 24-year-old woman presents to her family physician for follow-up of bloodwork for a history of heavy menstrual bleeding from the onset of menarche. She also describes easy bruising and recurrent episodes of epistaxis. Routine coagulation studies (platelet count, activated partial thromboplastin

Thrombotic microangiopathy in a patient with adult-onset Still's disease.

Since there are many disorders that can present with thrombotic microangiopathy (TMA), establishing a correct diagnosis is important to offer the most appropriate therapy.

In collaboration with the Canadian Anesthesiologists’ Society, the Canadian Journal of Anesthesia is proud to publish the best abstracts presented at the Annual Meeting of the Canadian Anesthesiologists’ Society held in Quebec City, Quebec, June 18–22, 2004

tion by a member of the Society. The Richard Knill competition was instituted in memory of Dr. Richard Knill, a foremost researcher in anesthesiology and prominent collaborator to the Canadian Journal of Anesthesia (CJA). The Annual Meeting Committee selects the top abstracts submitted for presentation by members of the Society at the Annual Meeting. The authors are invited to present their results at the Richard Knill competition. Presentations are marked by a jury composed of the members of the Editorial Board of the CJA. In 2004, the Richard Knill Award was presented to Dr. David C. Campbell for his work on Patient Controlled Epidural Analgesia during labour.