The role of the endothelium in traumatic coagulopathy.

Lead Research Organisation: University of Oxford
Department Name: RDM Clinical Laboratory Sciences

Abstract

What is trauma coagulopathy?
Worldwide, trauma is the most common cause of death for people aged less than 44. Uncontrolled bleeding leads directly to the deaths of two-thirds of injured patients who might otherwise have survived. Clinical studies have shown that if a trauma patient develops a failure of their clotting system (trauma coagulopathy) they are much more likely to bleed heavily; to develop organ failure; and to die.

What is known about the clotting changes that take place in trauma coagulopathy?
The main purpose of the clotting system is to reduce blood loss at sites of injury. When a blood vessel is injured, a coordinated process is activated and small cells called platelets bind to the site of injury and are held in place by a protein called fibrin. In order that the clot remains only at the site of injury, anticoagulant and clot breakdown proteins act at the edges of the clot. One of the most important of these proteins is called activated protein C. Activated protein C forms after it binds to a protein complex called the thrombin-thrombomodulin complex. In health, thrombomodulin is found on the surface of the cells that line blood vessels (the endothelium) and it acts mainly to restrict clot formation to the site of injury.
Large clinical studies of blood samples taken from trauma patients have shown changes that occur as part of the clotting problem. These include high activated protein C levels, high levels of clot breakdown proteins, and evidence of blood vessel wall damage (i.e. high thrombomodulin levels).

How is bleeding after trauma treated?
The treatment of bleeding relies almost entirely on simple replacement of clotting factors that have been lost (given as a transfusion of plasma) in combination with a blood transfusion. The only drug shown to be of benefit is tranexamic acid which reduces clot breakdown. However, if tranexamic acid is given after 3 hours of injury, patients are more likely to die. Current therapy is therefore limited.

What is unknown?
So far, research into trauma coagulopathy has looked at the changes that happen to blood clotting factor levels in simple experiments. This work is good at finding out what happens to specific clotting protein levels at a single time point, but it has several problems. Firstly, it does not look at the complex interactions of all of the proteins with each other. Secondly, it does not test how the injured vessel wall interacts with the forming clot. And finally, this test does not take into account that a clot forms in a vessel i.e. whilst blood flows past the clot.
Vessel wall cells have proteins on their surface which are involved in clotting. Some of these proteins have been shown to be sloughed off the vessel wall after injury (e.g. thrombomodulin) and it is unknown how much this affects clotting after injury. Understanding the links between injury, the blood vessel wall and the coagulopathy will allow more effective treatments to be developed.

What will I do?
I want to understand how injury alters the complex interactions of clotting proteins in trauma and how the blood vessel wall influences these changes. I will do this by using tests that evaluate an overall measure of how well a clot can be formed or broken down. I will also develop a cell model which includes two further elements: endothelial cells and blood flow. Once I have developed the best recipe for this model, I will test samples of blood taken from trauma patients and look at how their clots form.

Why is this research important?
Despite an improvement in the treatment of patients with bleeding, a 2019 NHS survey reported that one quarter of patients still die by 48 hours. The annual cost of treating trauma related bleeding in the UK is £168 million (2012 data). This research will enable the development of a robust method to test why clotting becomes so abnormal after injury and will allow testing of new targeted treatments for this global problem.

Technical Summary

As a clinician specialising in bleeding disorders, and as the Chair of the Major Haemorrhage Committee, I have seen how important it is to develop effective treatments for trauma-related-haemorrhage. Mortality associated with major bleeding is high and the lack of understanding of how coagulopathy develops in patients with uncontrolled bleeding underpins the lack of effective treatments.

Aim: to understand the pathophysiology of acute traumatic coagulopathy, with a focus on the endothelial/coagulation interface.
Objective 1: To critically evaluate the effects of thrombomodulin (TM) in vitro on key clotting factors in trauma coagulopathy using two dynamic haemostasis assays.
Objective 2: To develop an endothelial model of trauma coagulopathy using blood outgrowth endothelial cells (BOECs).
Objective 3: To investigate the effects of thrombomodulin on thrombus formation using the BOEC trauma model under flow conditions.

I will set up a study to collect blood and plasma samples from 20 healthy volunteers and from 2 members of a family with a known THBD variant. I set up the ACIT-2 study in Oxford in 2010 and with my ongoing oversight it continues to recruit patients. Detailed clinical data and linked plasma samples have been collected according to the REC approved study protocol. All studies will comply and follow the Codes of Practice issued by the Human Tissue Authority.
The dynamic real time haemostasis assays, and the ELISA tests will be conducted at the Oxford Haemophilia and Thrombosis Centre using existing resources. The BOEC work, in both static and flow conditions, will be completed within Professor Choudhury's laboratory within the Division of Cardiovascular Medicine, Oxford University using existing resources.
Outcomes: My goal is to develop a robust 'trauma endothelial' model which will form the basis for future work exploring the key endothelial drivers of trauma coagulopathy and which will lead on to the testing of potential therapeutic targets.

Planned Impact

Patients: as a clinician my primary aim is to improve the treatment of patients suffering with abnormalities of haemostasis, including those with haemorrhage-associated coagulopathy. One person dies every nine minutes from injury, and uncontrolled bleeding is the primary cause of death in 60% of patients who might otherwise have survived their injury. As a haemostasis clinician involved in managing these complex and critically ill patients, it is very clear that current therapy is inadequate and there is a strong rationale for developing targeted treatments which treat and prevent coagulopathy. The incidence of major trauma haemorrhage within the UK is estimated at 83 per million of the population. Mortality amongst these patients reaches 50% at 1 year (i.e. 2,500 patients annually). A 10% reduction in major haemorrhage related deaths would equate to 250 patients surviving every year. In order to achieve this goal, it is necessary to understand the complex interactions between the endothelial surface and the coagulation proteases. This research application is based on developing an understanding of these mechanisms and represents an early stage in the process towards developing targeted therapies. Ultimately the main beneficiaries of this research work will be future patients.

Oxford Haemophilia & Thrombosis Centre (OHTC): The longer-term goal is to develop a research group at the OHTC which will conduct translational research into the causes and treatments for both acquired and inherited bleeding conditions using similar endothelial biology techniques. At present at the OHTC there is a large diagnostic service, but investigations are centred on blood coagulation analysis and do not include endothelial function. OHTC is one of the largest haemostasis centres in the UK with a large patient base and is ideally suited to support such a research facility. This will enable both large patient cohorts (acquired bleeding) and rare conditions with small patient cohorts (inherited bleeding) to be investigated. It will also provide an invaluable training centre for trainee scientists and clinical academics.

Public beneficiaries: trauma patients account for 15% of all major haemorrhage activations across the UK and empirical blood transfusion therapy is standard of care. The development of strategies to prevent traumatic coagulopathy will reduce the need for inappropriate blood transfusion, will improve outcomes and reduce the high cost of trauma haemorrhage therapy (£168 million annually based on 2012 costs).

Drug discovery: the proposed endothelial model will provide a novel platform for drug discovery. This will have the potential to investigate novel therapeutic targets.

Publications

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Dhanapal J (2022) Clinical aspects of coagulation and haemorrhage in Anaesthesia & Intensive Care Medicine

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Morrow GB (2021) Fibrinogen Replacement Therapy for Traumatic Coagulopathy: Does the Fibrinogen Source Matter? in International journal of molecular sciences

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Winearls J (2021) Fibrinogen in traumatic haemorrhage. in Current opinion in anaesthesiology

 
Description Funding to support a 2 year post doctoral researcher to suport enothelial cell model development
Amount £57,000 (GBP)
Organisation University of Oxford 
Sector Academic/University
Country United Kingdom
Start 05/2022 
End 06/2024
 
Description Development of a novel plasmin inhibitor 
Organisation University of Leeds
Country United Kingdom 
Sector Academic/University 
PI Contribution I am beginning to develop a partnership with Professor Helen Phillipou in Leeds to work on a novel new molecule with the aim to undertake clinical studies with a plasmin inhibitor in patients with acquired bleeding. THis is a very early collaboration (2 weeks old) and therefore we are at the stages of discussion rather than anything more solid.
Collaborator Contribution I will be providing the scientific team in Leeds with my clinical expertise and my knowlegde of the importance of fibrinolysis in acquried bleeding - it is possible in time that this collaboration will develop into a real development of a drug that can be used in clinical practice. This is however a long way off.
Impact Nil to date
Start Year 2023
 
Description Porcine coagulopathy 
Organisation Defence Science & Technology Laboratory (DSTL)
Country United Kingdom 
Sector Public 
PI Contribution I am developing a collaboration with the scientific team at Porton Down. We work together on aspects of traumatic coagulopathy - exploring the role of Fibrinogen in porcine models. COVID has slightly got in the way, due to Porton Down scientists needing to be redeployed for different work - so this collaboration is slow in developing due to this
Collaborator Contribution However, we meet once a quarter to discuss models of porcine traumatic coagfulopathy, and we are providing the means by which porcine plasma can be analysed for the fibrinolytic pathways. Up until now, the MoD haven't been able to analyse firbinolysis in the pig very well, but we have begun recently to be able to show that we can get fibrinolytic curves using a mixture of a human and porcine model - so we are bringing our different experiences together to develop a novel testing strategy.
Impact Between 2022 - 2023, this collaboration continues and together we have put in an application to explore fibrinolysis in the pig model in more detail. We have found some interesting findings with the fibrinolytic measures which may in part provide infomration about the fibrinolytic pathway in patients.
Start Year 2020
 
Description International meeting - presentation of work by my post doctoral researcher 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Winner of the best abstract for acquired bleeding at the International Society of Haemostasis and Thrombosis - the largest annual conference in haematology (10,000 attendees).
My post-doc presented in the plenary lecture theatre our work on trauma coagulopathy - the reach was to the whole of the attendees - but it is unliekly they all attended/watch on line - so possibly several thousand in total.
Year(s) Of Engagement Activity 2022
 
Description Presentation of work at the Radcliffe Department of Medicine annual meeting 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Postgraduate students
Results and Impact Presentation of my work to date on trauma coagulopathy and the development of the endothelial model
150 members of the oxford university RDM dept attended
Year(s) Of Engagement Activity 2022