The future of burn care from a complexity science perspective

An in silico modeling approach to understanding the dynamics of the post-burn immune response

Introduction

Burns are characterized by a massive and prolonged acute inflammation, which persists for up to months after the initial trauma. Due to the complexity of the inflammatory process, Predicting the dynamics of wound healing process can be challenging for burn injuries. The aim of this study was to develop simulation models for the post-burn immune response based on (pre)clinical data.

Methods

The simulation domain was separated into blood and tissue compartments. Each of these compartments contained solutes and cell agents. Solutes comprise pro-inflammatory cytokines, anti-inflammatory cytokines and inflammation triggering factors. The solutes diffuse around the domain based on their concentration profiles. The cells include mast cells, neutrophils, and macrophages, and were modeled as independent agents. The cells are motile and exhibit chemotaxis based on concentrations gradients of the solutes. In addition, the cells secrete various solutes that in turn alter the dynamics and responses of the burn wound system.

Results

We developed an Glazier-Graner-Hogeweg method-based model (GGH) to capture the complexities associated with the dynamics of inflammation after burn injuries, including changes in cell counts and cytokine levels. Through simulations from day 0 - 4 post-burn, we successfully identified key factors influencing the acute inflammatory response, i.e., the initial number of endothelial cells, the chemotaxis threshold, and the level of chemoattractants.

Conclusion

Our findings highlight the pivotal role of the initial endothelial cell count as a key parameter for intensity of inflammation and progression of acute inflammation, 0 - 4 days post-burn.

Working Towards Holistic Scar Assessment and Improved Shared Decision Making in Global Burn Care

Cutaneous burn scars impact various aspects of life. Scar treatment is mainly evaluated on scar characteristics. Consensus is needed on which other outcomes to capture, ensuring they are relevant to patients, clinicians, and researchers. The aim of this study was to identify, discuss and analyze outcomes related to cutaneous burn scarring, incorporating the voice of patients and views of healthcare professionals. For this, a Delphi process consisting of two survey rounds and a consensus meeting was initiated. Burn scar-related outcomes were identified from an existing comprehensive list of 100 outcomes by an international panel of patients, healthcare professionals and researchers. Fifty-nine outcomes were identified from the Delphi process as related to scarring (≥60% votes). Outcomes less impactful in relation to scar outcomes included psychosocial issues, sense of normality, understanding of treatment, costs and systemic issues. To represent a holistic assessment of outcomes related to cutaneous burn scarring, this Delphi process established a battery of outcomes currently included in scar quality assessment tools, and an expanded set of less frequently considered outcomes. Future work in this area must include the patient voice from developing countries. This is essential to identify globally applicable outcomes related to scarring.

Health systems research in burn care: an evidence gap map

BACKGROUND

Burn injury is associated with significant mortality and disability. Resilient and responsive health systems are needed for optimal response and care for people who sustain burn injuries. However, the extent of health systems research (HSR) in burn care is unknown. This review aimed to systematically map the global HSR related to burn care.

METHODS

An evidence gap map (EGM) was developed based on the World Health Organization health systems framework. All major medical, health and injury databases were searched. A standard method was used to develop the EGM.

RESULTS

A total of 6586 articles were screened, and the full text of 206 articles was reviewed, of which 106 met the inclusion criteria. Most included studies were cross-sectional (61%) and were conducted in hospitals (71%) with patients (48%) or healthcare providers (29%) as participants. Most studies were conducted in high-income countries, while only 13% were conducted in low-and middle-income countries, accounting for 60% of burns mortality burden globally. The most common health systems areas of focus were service delivery (53%), health workforce (33%) and technology (19%). Studies on health policy, governance and leadership were absent, and there were only 14 qualitative studies.

CONCLUSIONS

Major evidence gaps exist for an integrated health systems response to burns care. There is an inequity between the burden of burn injuries and HSR. Strengthening research capacity will facilitate evidence-informed health systems and policy reforms to sustainably improve access to affordable, equitable and optimal burn care and outcomes.

The Complexity of the Post-Burn Immune Response: An Overview of the Associated Local and Systemic Complications

Burn injury induces a complex inflammatory response, both locally and systemically, and is not yet completely unravelled and understood. In order to enable the development of accurate treatment options, it is of paramount importance to fully understand post-burn immunology. Research in the last decades describes insights into the prolonged and excessive inflammatory response that could exist after both severe and milder burn trauma and that this response differs from that of none-burn acute trauma. Persistent activity of complement, acute phase proteins and pro- and anti-inflammatory mediators, changes in lymphocyte activity, activation of the stress response and infiltration of immune cells have all been related to post-burn local and systemic pathology. This "narrative" review explores the current state of knowledge, focusing on both the local and systemic immunology post-burn, and further questions how it is linked to the clinical outcome. Moreover, it illustrates the complexity of post-burn immunology and the existing gaps in knowledge on underlying mechanisms of burn pathology.

Burn-injured skin is marked by a prolonged local acute inflammatory response of innate immune cells and pro-inflammatory cytokines

The systemic and local immune response in burn patients is often extreme and derailed. As excessive inflammation can damage healthy tissues and slow down the healing process, modulation of inflammatory responses could limit complications and improve recovery. Due to its complexity, more detailed information on the immune effects of thermal injury is needed to improve patient outcomes. We therefore characterized and quantified subsets of immune cells and mediators present in human burn wound tissue (eschar), sampled at various time points. This study shows that after burn injury, the number of immune cells were persistently increased, unlike the normal wound healing process. There was an immediate, strong increase in neutrophils and a moderate increase in monocytes/macrophages and lymphocytes, especially in the second and third week post burn. The percentage of classical (CD14highCD16-) monocytes/macrophages demonstrated a steady decrease over time, whereas the proportion of intermediate (CD14highCD16+) monocytes/macrophages slowly increased. The absolute numbers of T cells, NK cells and B cells increased up to week 3, while the fraction of γδ T cells was increased only in week 1. Secretome profiling revealed high levels of chemokines and an overall pro-inflammatory cytokine milieu in burn tissue. The local burn immune response shows similarities to the systemic immune reaction, but differs in neutrophil maturity and lymphocyte composition. Altogether, the neutrophil surges, high levels of pro-inflammatory cytokines and limited immunosuppression might be key factors that prolong the inflammation phase and delay the wound healing process in burns.