Characteristics of Platelet Lysate Compared to Autologous and Allogeneic Serum Eye Drops.

Purpose: Platelet lysate produced from platelet apheresis components has been proposed as an alternative to serum eye drops in the treatment of ocular surface disease. This study compared the effects of platelet lysate and serum on growth factor, cytokine and nanoparticle concentrations, and corneal epithelial cell proliferation. Methods: The concentration of growth factors, cytokines, and nanoparticles in platelet lysates manufactured from either fresh or expired platelet apheresis concentrations collected with Trima or Haemonetics technology was characterized and compared with those of allogeneic, autologous, and fetal calf serum. The ability to promote corneal epithelial cell proliferation and wound healing was tested in vitro. Results: Platelet lysate enriched the amount of transforming growth factor ß1, platelet-derived growth factor -AB and -BB, fibroblast growth factor, and epidermal growth factor compared with the two sera groups. The concentrations of insulin-like growth factor 1, hepatocyte growth factor, and fibronectin were significantly lower than in sera. There were no differences in nanoparticle concentrations. There was no significant difference in corneal epithelial cell proliferation. Platelet lysates were comparable to fetal calf serum in accelerating corneal epithelial wound healing in vitro. Conclusions: Fresh and expired platelet lysates from the Trima and Haemonetics systems had higher growth factor concentrations than sera. The ability of platelet lysates to promote corneal epithelial cell proliferation and wound healing was equivalent to sera. Translational Relevance: Platelet lysates may serve as an efficient and reliable source of human growth factors for the treatment of ocular surface diseases.

Spontaneous intracerebral haemorrhage: a rare complication of aortic aneurysm endoleak.

We present a rare case of intracerebral haemorrhage secondary to consumptive coagulopathy in relation to ongoing endoleak after thoracic endovascular aneurysm repair (TEVAR). A 68-year-old man underwent elective TEVAR for an 18 cm diameter Crawford type II thoracoabdominal aneurysm. He was subsequently shown to have a type 1b endoleak and a short episode of disseminated intravascularcoagulation (DIC) perioperatively. Two months after the procedure, he experienced a consumptive coagulopathy leading to intracerebral haemorrhage and ultimately his death. Endoleak-related DIC is an underappreciated phenomenon within the medical literature. Currently, management is reliant on general DIC principles and anecdotal experiences of others within the case report literature.

An Evaluation of a Factor Xa-Based Clotting Time Test for Enoxaparin: A Proof-of-Concept Study.

A well-accepted test for monitoring anticoagulation by enoxaparin is not currently available. As inadequate dosing may result in thrombosis or bleeding, a clinical need exists for a suitable test. Previous in silico and in vitro studies have identified factor Xa as an appropriate activating agent, and the phospholipid Actin FS as a cofactor for a Xa clotting time (TenaCT) test. A proof-of-concept study was designed to (1) explore the reproducibility of the TenaCT test and (2) explore factors that could affect the performance of the test. In vitro clotting time tests were carried out using plasma from 20 healthy volunteers. The effect of enoxaparin was determined at concentrations of 0.25, 0.50, and 1.0 IU/mL. Clotting times for the volunteers were significantly prolonged with increasing enoxaparin concentrations. Clotting times were significantly shortened for frozen plasma samples. No significant differences in prolongation of clotting times were observed between male and female volunteers or between the 2 evaluated age groups. The clotting times were consistent between 2 separate occasions. The TenaCT test was able to distinguish between the subtherapeutic and therapeutic concentrations of enoxaparin. Plasma should not be frozen prior to performing the test, without defining a frozen plasma reference range. This study provided proof-of-concept for a Xa-based test that can detect enoxaparin dose effects, but additional studies are needed to further develop the test.

Mechanistic insight into the procoagulant activity of tumor-derived apoptotic vesicles.

BACKGROUND: Chemotherapy induces the release of apoptotic vesicles (ApoV) from the tumor plasma membrane. Tumor ApoV may enhance the risk of thrombotic events in cancer patients undergoing chemotherapy. However, the relative contribution of ApoV to coagulation and the pathways involved remain poorly characterized. In addition, this study sets out to compare the procoagulant activity of chemotherapy-induced ApoV with their cell of origin and to determine the mechanisms of ApoV-induced coagulation. METHODS: We utilized human and murine cancer cell lines and chemotherapeutic agents to determine the requirement for the coagulation factors (tissue factor; TF, FII, FV, FVII, FVIII, FIX and phosphatidylserine) in the procoagulant activity of ApoV. The role of previously identified ApoV-associated FV was determined in a FV functional assay. RESULTS: ApoV were significantly more procoagulant per microgram of protein compared to parental living or dying tumor cells. In the phase to peak fibrin generation, procoagulant activity was dependent on phosphatidylserine, TF expression, FVII and the prothrombinase complex. However, the intrinsic coagulation factors FIX and FVIII were dispensable. ApoV-associated FV could not support coagulation in the absence of supplied, exogenous FV. CONCLUSIONS: ApoV are significantly more procoagulant than their parental tumor cells. ApoV require the extrinsic tenase and prothrombinase complex to activate the early phase of coagulation. Endogenous FV identified on tumor ApoV is serum-derived and functional, but is non-essential for ApoV-mediated fibrin generation. GENERAL SIGNIFICANCE: This study clarifies the mechanisms of procoagulant activity of vesicles released from dying tumor cells.

Procoagulant and immunogenic properties of melanoma exosomes, microvesicles and apoptotic vesicles.

Extracellular vesicles (EV) are lipid particles released from eukaryotic cells into the extracellular fluid. Depending on the cell type or mechanism of release, vesicles vary in form and function and exert distinct functions in coagulation and immunity. Tumor cells may constitutively shed vesicles known as exosomes or microvesicles (MV). Alternatively, apoptosis induces the release of apoptotic blebs or vesicles (ApoV) from the plasma membrane. EV have been implicated in thrombotic events (the second highest cause of death in cancer patients) and tumor vesicles contribute to the anti-cancer immune response. In this study, we utilized the well characterized B16 melanoma model to determine the molecular composition and procoagulant and immunogenic potential of exosomes, MV and ApoV. Distinct patterns of surface and cytoplasmic molecules (tetraspanins, integrins, heat shock proteins and histones) were expressed between the vesicle types. Moreover, in vitro coagulation assays revealed that membrane-derived vesicles, namely MV and ApoV, were more procoagulant than exosomes-with tissue factor and phosphatidylserine critical for procoagulant activity. Mice immunized with antigen-pulsed ApoV and challenged with B16 tumors were protected out to 60 days, while lower protection rates were afforded by MV and exosomes. Together the results demonstrate distinct phenotypic and functional differences between vesicle types, with important procoagulant and immunogenic functions emerging for membrane-derived MV and ApoV versus endosome-derived exosomes. This study highlights the potential of EV to contribute to the prothrombotic state, as well as to anti-cancer immunity.

Application of Adaptive DP-optimality to Design a Pilot Study for a Clotting Time Test for Enoxaparin.

PURPOSE: Dosing of enoxaparin, like other anticoagulants, may result in bleeding following excessive doses and clot formation if the dose is too low. We recently showed that a factor Xa based clotting time test could potentially assess the effect of enoxaparin on the clotting system. However, the test did not perform well in subsequent individuals and effectiveness of an exogenous phospholipid, Actin FS, in reducing the variability in the clotting time was assessed. The aim of this work was to conduct an adaptive pilot study to determine the range of concentrations of Xa and Actin FS to take forward into a proof-of-concept study. METHODS: A nonlinear parametric function was developed to describe the response surface over the factors of interest. An adaptive method was used to estimate the parameters using a D-optimal design criterion. In order to provide a reasonable probability of observing a success of the clotting time test, a P-optimal design criterion was incorporated using a loss function to describe the hybrid DP-optimality. RESULTS: The use of adaptive DP-optimality method resulted in an efficient estimation of model parameters using data from only 6 healthy volunteers. The use of response surface modelling identified a range of sets of Xa and Actin FS concentrations, any of which could be used for the proof-of-concept study. CONCLUSIONS: This study shows that parsimonious adaptive DP-optimal designs may provide both precise parameter estimates for response surface modelling as well as clinical confidence in the potential benefits of the study.

Octanoate in Human Albumin Preparations Is Detrimental to Mesenchymal Stromal Cell Culture.

Cell therapies hold great promise as the next major advance in medical treatment. To enable safe, effective ex vivo culture whilst maintaining cell phenotype, growth media constituents must be carefully controlled. We have used a chemically defined mesenchymal stromal cell culture medium to investigate the influence of different preparations of human serum albumin. We examined two aspects of cell culture, growth rate as measured by population doubling time and colony forming ability which is a representative measure of the stemness of the cell population. Albumin preparations showed comparative differences in both of these criteria. Analysis of the albumin bound fatty acids also showed differences depending on the manufacturing procedure used. We demonstrated that octanoate, an additive used to stabilize albumin during pasteurization, slows growth and lowers colony forming ability during ex vivo culture. Further to this we also found the level of Na(+)/K(+) ATPase, a membrane bound cation pump inhibited by octanoate, is increased in cells exposed to this compound. We conclude that the inclusion of human serum albumin in ex vivo growth media requires careful consideration of not only the source of albumin, but also the associated molecular cargo, for optimal cell growth and behavior.

Benign FGB (148Lys→Asn, and 448Arg→Lys), and novel causative γ211Tyr→His mutation distinguished by time of flight mass spectrometry in a family with hypofibrinogenaemia.

We describe a novel procedure for the direct analysis of plasma fibrinogen by HPLC time of flight (TOF) mass spectrometry and apply it to the investigation of a family with hypofibrinogenaemia. Electrospray TOF analysis provided much higher resolution than was possible with our previous quadrupole analyser and revealed three different mass changes within the fibrinogen Bß and γ chains of the family. It also demonstrated the actual hypofibrinogenaemia phenotype was caused by an aberrantγ chain (-23 Da) which was expressed at a diminished ratio of 0.2:1 relative to γ(A) and co-inherited with a second coequally expressed Bß variant (Bß(M) /Bß(A), 1:1). Co-segregation was confirmed by gene analysis that showed the affected father and son had a very rare Bß148Lys→Arg mutation (-14 Da) inherited together with a unique new γ211Tyr→His mutation (-26 Da). This latter causative substitution occurs at a site that is absolutely conserved across all fibrinogen chains and preserved across all species. TOF analysis also identified a variant Bß chain (54,186 Da) that was coequally expressed with normal Bß chains (54,213 Da) in the unaffected mother.

Dabigatran: rational dose individualisation and monitoring guidance is needed.

Dabigatran is the first oral anticoagulant to be introduced in New Zealand without prescribing restrictions for over 50 years. Not surprisingly, the drug has created a great deal of interest amongst health care providers as well as the general public and media. There seems to be a general feeling that warfarin, with its requisite dose adjustments and INR monitoring, is an outdated drug and should be shelved in favour of this novel agent. The assumption is that the newer drug must be better and safer as well as easier to use. Much of the literature associated with dabigatran encourages this view, stressing that dabigatran is a 'game changer' with the advantage of fixed dosing for most patients and no anticoagulation monitoring. In this paper we question whether dabigatran can really live up to these expectations. We suggest that the safe and effective prescribing of dabigatran, like all anticoagulants used in therapeutic doses, will most likely require dose individualisation and selective monitoring. This requirement should not be viewed as a failure for dabigatran but rather as a success for rational therapeutics.

Development and evaluation of a prototype of a novel clotting time test to monitor enoxaparin.

PURPOSE: Dosing of the anticoagulant enoxaparin may result in bleeding following excessive doses or thrombosis if dose is too low. Rarely, anti-Xa activity is used to assess the dose for enoxaparin, but its utility to predict clotting or bleeding remains uncertain. We aimed to develop a clotting time test to monitor enoxaparin therapy. METHODS: A previously developed mathematical model of the coagulation network was used to identify suitable targets for monitoring enoxaparin therapy. In vitro experiments were then carried out to demonstrate proof of mechanism of the clotting time test activated by the new target activator. RESULTS: Using the mathematical model, we identified Xa as a plausible activating agent for a clotting time test for enoxaparin. In vitro experiments showed a prolongation of the Xa clotting time of 4.6-fold in the presence of enoxaparin (0.5 IU/ml) where 10 nM Xa was used to activate clotting. CONCLUSIONS: Using both simulations and in vitro experiments, we provide a proof of mechanism for the Xa clotting time (XaCT) test, which can be considered for further development to provide a biomarker of the effect of enoxaparin on the clotting system.