The mode of anesthesia influences outcome in mouse models of arterial thrombosis

Developing human tissue engineered arterial constructs to simulate human in vivo thrombus formation

Thrombus formation is highly dependent upon the physico-chemical environment in which it is triggered. Our ability to understand how thrombus formation is initiated, regulated, and resolved in the human body is dependent upon our ability to replicate the mechanical and biological properties of the arterial wall. Current in vitro thrombosis models principally use reductionist approaches to model the complex biochemical and cellular milieu present in the arterial wall, and so researcher have favored the use of in vivo models. The field of vascular tissue engineering has developed a range of techniques for culturing artificial human arteries for use as vascular grafts. These techniques therefore provide a basis for developing more sophisticated 3D replicas of the arterial wall that can be used in in vitro thrombosis models. In this review, we consider how tissue engineering approaches can be used to generate 3D models of the arterial wall that improve upon current in vivo and in vitro approaches. We consider the current benefits and limitations of reported 3D tissue engineered models and consider what additional evidence is required to validate them as alternatives to current in vivo models.

Loss of 12-Lipoxygenase Improves the Post-Transfusion Function of Stored Platelets

BACKGROUND

Platelets for transfusion are stored for 5 to 7 days. Previous studies have shown that HETE levels in the storage bag negatively correlate with platelet performance in vivo, suggesting that the dysregulation of bioactive lipid mediators may contribute to the storage lesion. In the current study, we sought to understand how genetic deletion and pharmacological inhibition of 12-LOX (12-lipoxygenase) affects platelets during storage and after transfusion.

METHODS

Platelets from 12-LOX+/+ (wild-type [WT]) and 12-LOX-/- mice were stored for 24 and 48 hours and profiled using liquid chromatography-tandem mass spectrometry-multiple reaction monitoring or transfused into thrombocytopenic hIL4R (human interleukin 4 receptor)-transgenic mice. Platelet function was assessed by flow cytometry and in vivo thrombosis and hemostasis models. To test the role of the COX-1 (cyclooxygenase-1) pathway, donor mice were treated with acetylsalicylic acid. Human platelets were treated with the 12-LOX inhibitor, VLX-1005, or vehicle, stored, and transfused to NOD/SCID (nonobese diabetic/severe combined immunodeficiency) mice.

RESULTS

Polyunsaturated fatty acids increased significantly in stored platelets from 12-LOX-/- mice, whereas oxylipin concentrations were significantly higher in WT platelets. After transfusion to thrombocytopenic mice, we observed significantly more baseline αIIbβ3 integrin activation in 12-LOX-/- platelets than in WT platelets. Stored platelets from 12-LOX-/- mice occluded vessels significantly faster than stored WT platelets. In hemostasis models, significantly more stored 12-LOX-/- than WT platelets accumulated at the site of venous injury leading to reduced blood loss. Inhibition of COX-1 abrogated both increased integrin activation and thromboxane generation in stored 12-LOX-/- platelets, highlighting the critical role of this pathway for improved post-transfusion function. Consistent with our mouse studies, human platelets stored with VLX-1005, showed increased integrin activation compared with vehicle-treated platelets after transfusion.

CONCLUSIONS

Deleting 12-LOX improves the post-transfusion function of stored murine platelets by increasing thromboxane generation through COX-1-dependent arachidonic acid metabolism. Future studies should determine the feasibility and safety of 12-LOX-inhibited platelets transfused to humans.

Developing Biomimetic Hydrogels of the Arterial Wall as a Prothrombotic Substrate for In Vitro Human Thrombosis Models

Current in vitro thrombosis models utilise simplistic 2D surfaces coated with purified components of the subendothelial matrix. The lack of a realistic humanised model has led to greater study of thrombus formation in in vivo tests in animals. Here we aimed to develop 3D hydrogel-based replicas of the medial and adventitial layers of the human artery to produce a surface that can optimally support thrombus formation under physiological flow conditions. These tissue-engineered medial- (TEML) and adventitial-layer (TEAL) hydrogels were developed by culturing human coronary artery smooth muscle cells and human aortic adventitial fibroblasts within collagen hydrogels, both individually and in co-culture. Platelet aggregation upon these hydrogels was studied using a custom-made parallel flow chamber. When cultured in the presence of ascorbic acid, the medial-layer hydrogels were able to produce sufficient neo-collagen to support effective platelet aggregation under arterial flow conditions. Both TEML and TEAL hydrogels possessed measurable tissue factor activity and could trigger coagulation of platelet-poor plasma in a factor VII-dependent manner. Biomimetic hydrogel replicas of the subendothelial layers of the human artery are effective substrates for a humanised in vitro thrombosis model that could reduce animal experimentation by replacing current in vivo models.

Locking and Unlocking Thrombin Function Using Immunoquiescent Nucleic Acid Nanoparticles with Regulated Retention In Vivo

The unbalanced coagulation of blood is a life-threatening event that requires accurate and timely treatment. We introduce a user-friendly biomolecular platform based on modular RNA-DNA anticoagulant fibers programmed for reversible extracellular communication with thrombin and subsequent control of anticoagulation via a "kill-switch" mechanism that restores hemostasis. To demonstrate the potential of this reconfigurable technology, we designed and tested a set of anticoagulant fibers that carry different thrombin-binding aptamers. All fibers are immunoquiescent, as confirmed in freshly collected human peripheral blood mononuclear cells. To assess interindividual variability, the anticoagulation is confirmed in the blood of human donors from the U.S. and Brazil. The anticoagulant fibers reveal superior anticoagulant activity and prolonged renal clearance in vivo in comparison to free aptamers. Finally, we confirm the efficacy of the "kill-switch" mechanism in vivo in murine and porcine models.

Effect of Different Anesthesia Methods on Emergence Agitation and Related Complications in Postoperative Patients with Osteosarcoma

Purpose

To explore the effect of different anesthesia methods on emergence agitation (EA) and related complications in postoperative patients with osteosarcoma.

Methods

According to the order of admission, 115 patients requiring osteosarcoma surgery treated in our hospital from January 2018 to December 2020 were selected as the research object and randomly divided into the control group (n = 57, accepted the general anesthesia with tracheal intubation) and the experimental group (n = 58, accepted the combined spinal-epidural anesthesia) to compare their anesthesia effect, incidence rates of agitation and complications, and other indexes.

Results

In terms of the hemodynamic indexes (MAP, HR, and CVP values), both groups had lower ones at T₁ than at T₀, but the decline of the experimental group was generally lesser than that of the control group; at T₂, no statistical difference was shown within the experimental group's indexes when comparing with those at T₁, but the control group obtained a significant increase; at T₃ and T₄, both groups had their hemodynamic indexes increased, but such increase within the experimental group showed no statistical difference when comparing with those at T₀, while the control group achieved obviously higher values at T₄ than at T₀ (before the anesthesia); and the between-group difference in the hemodynamic indexes at T₁ and T₄ was significant. Compared with the control group, the experimental group achieved better VAS scores and anesthesia indexes and lower incidence rates of EA and complications such as the hypoxemia, cardiovascular response, delayed recovery, and headache. In addition, the differences in the incidence rates of hypotension and cognitive dysfunction between the two groups were not statistically significant.

Conclusion

When comparing with tracheal intubation general anesthesia, the combined spinal-epidural anesthesia has a better effect in osteosarcoma surgery, with less hemodynamics influence on patients, reduced postoperative pain and stress reaction, and lowered incidence rates of postoperative EA and complications, which is worthy of wide application in clinical treatment.

Early Endothelial Activation in a Mouse Model of Graft vs Host Disease Following Chemotherapy

Allogenic hematopoietic stem cell transplant (allo-HSCT) can lead to sinusoidal obstruction syndrome (SOS) and graft-versus-host disease (GvHD) in some individuals. GvHD is characterised by an immune triggered response that arises due to donor T cells recognizing the recipient tissue as “foreign”. SOS results in impaired liver function due to microvascular thrombosis and consequent obstruction of liver sinusoids. Endothelial damage occurs following chemotherapy and allo-HSCT and is strongly associated with GvHD onset as well as hepatic SOS. Animal models of GvHD are rarely clinically relevant, and endothelial dysfunction remains uncharacterised. Here we established and characterised a clinically relevant model of GvHD wherein Balb/C mice were subjected to myeloablative chemotherapy followed by transplantation of bone marrow (BM) cells± splenic T-cells from C57Bl6 mice, resulting in a mismatch of major histocompatibility complexes (MHC). Onset of disease indicated by weight loss and apoptosis in the liver and intestine was discovered at day 6 post-transplant in mice receiving BM+T-cells, with established GvHD detectable by histology of the liver within 3 weeks. Together with significant increases in pro-inflammatory cytokine gene expression in the liver and intestine, histopathological signs of GvHD and a significant increase in CD4+ and CD8+ effector and memory T-cells were seen. Endothelial activation including upregulation of vascular cell adhesion molecule (VCAM)- 1 and downregulation of endothelial nitric oxide synthase (eNOS) as well as thrombosis in the liver indicated concomitant hepatic SOS. Our findings confirm that endothelial activation is an early sign of acute GvHD and SOS in a clinically relevant mouse model of GvHD based on myeloablative chemotherapy. Preventing endothelial activation may be a viable therapeutic strategy to prevent GvHD.

The Combination of Tissue-Engineered Blood Vessel Constructs and Parallel Flow Chamber Provides a Potential Alternative to In Vivo Drug Testing Models

Cardiovascular disease is a major cause of death globally. This has led to significant efforts to develop new anti-thrombotic therapies or re-purpose existing drugs to treat cardiovascular diseases. Due to difficulties of obtaining healthy human blood vessel tissues to recreate in vivo conditions, pre-clinical testing of these drugs currently requires significant use of animal experimentation, however, the successful translation of drugs from animal tests to use in humans is poor. Developing humanised drug test models that better replicate the human vasculature will help to develop anti-thrombotic therapies more rapidly. Tissue-engineered human blood vessel (TEBV) models were fabricated with biomimetic matrix and cellular components. The pro- and anti-aggregatory properties of both intact and FeCl₃-injured TEBVs were assessed under physiological flow conditions using a modified parallel-plate flow chamber. These were perfused with fluorescently labelled human platelets and endothelial progenitor cells (EPCs), and their responses were monitored in real-time using fluorescent imaging. An endothelium-free TEBV exhibited the capacity to trigger platelet activation and aggregation in a shear stress-dependent manner, similar to the responses observed in vivo. Ketamine is commonly used as an anaesthetic in current in vivo models, but this drug significantly inhibited platelet aggregation on the injured TEBV. Atorvastatin was also shown to enhance EPC attachment on the injured TEBV. The TEBV, when perfused with human blood or blood components under physiological conditions, provides a powerful alternative to current in vivo drug testing models to assess their effects on thrombus formation and EPC recruitment.

Wall shear rates in human and mouse arteries: Standardization of hemodynamics for in vitro blood flow assays: Communication from the ISTH SSC subcommittee on biorheology

Hemodynamics play a central role in hemostasis and thrombosis by affecting all aspects linked to platelet functions and coagulation. In vitro flow devices are extensively used in basic research, pharmacological studies, antiplatelet agent screening, and development of diagnostic tools. Because hemodynamic conditions vary tremendously throughout the vascular tree and among different (patho)physiological processes, it is important to use flow conditions based on relevant biorheological reference ranges. Surprisingly, it is particularly difficult to find a concise overview of relevant hemodynamic parameters in various human and mouse vessels. To our knowledge, this is the first time an inventory of flow conditions in healthy, non-diseased, human and mouse vessels has been created. The objective of providing such a repertoire is to aid researchers in the field of hemostasis and thrombosis in choosing rheological conditions relevant in in vitro flow experiments and to promote harmonization of flow-based assays to facilitate comparative evaluations between studies. With reference to the human, we discuss relevant similarities and discrepancies in wall shear rates in the mouse, which are typically one order of magnitude greater in agreement with allometric scaling laws between species. Importantly, we bring the attention of the researchers to the fact that the relevant range of average wall shear rates in human arteries where clinically relevant arterial thrombosis occurs may fall as low as 100 to 200 s-1, thus significantly overlapping with what are considered "venous" shear rates. The same range for the murine arteries used for arterial thrombosis models may significantly exceed 1000 s-1 reaching values considered to be "pathological."

Mouse models of hemostasis

Hemostasis is the normal process that produces a blood clot at a site of vascular injury. Mice are widely used to study hemostasis and abnormalities of blood coagulation because their hemostatic system is similar in most respects to that of humans, and their genomes can be easily manipulated to create models of inherited human coagulation disorders. Two of the most widely used techniques for assessing hemostasis in mice are the tail bleeding time (TBT) and saphenous vein bleeding (SVB) models. Here we discuss the use of these methods in the evaluation of hemostasis, and the advantages and limits of using mice as surrogates for studying hemostasis in humans.

How useful are ferric chloride models of arterial thrombosis?

The ferric chloride models of arterial thrombosis are useful tools with which to investigate the cellular and molecular mechanisms that contribute to arterial thrombosis. Recent insights have, however, revealed the complex and multifaceted mechanism by which ferric chloride induces thrombus formation. Here, we discuss the strengths and weaknesses of the ferric chloride models of arterial thrombosis. Particular focus is given to the phenotypes of different knockout mice in the ferric chloride models and how these compare to other models with independent modes of initiation. Further, we discuss the relevance of the ferric chloride models to the human pathology of atherothrombotic disease.