BG05 (P45): The good, the bad and the ugly: inflammation in epidermolysis bullosa wounds

A. Bardhan,^1,2 M. Muchova,¹ D. Wen,^1,2 N. Harper,² D. Balacco,¹ J. Hirschfeld,^1,3 S. Kuehne,¹ M. Grant,¹ I. Chapple^1,3 and A. Heagerty^1,2

¹Dermatology Research Group, University of Birmingham; ²Adult Epidermolysis Bullosa Unit, Department of Dermatology, University Hospitals Birmingham NHS Foundation Trust; and ³Birmingham Community Health NHS Trust, Birmingham, UK

Epidermolysis bullosa (EB) is a heterogeneous group of rare genetic skin fragility syndromes characterized by blistering induced by little-to-no trauma. To date, 16 genes underlying EB have been identified, encoding proteins predominantly underpinning cellular adhesion and integrity. Affected individuals suffer from recurrent and chronic wounds necessitating painful, time-intensive and costly dressings, potentially significant analgesic burden and markedly impaired psychosocial wellbeing. Moreover, chronically inflamed wounds and scars carry the risk of transformation to aggressive squamous cell carcinoma. The early inflammatory phase of wound healing is recognized as a necessary and pivotal stage in a precisely coordinated cascade of overlapping mechanisms required to maintain homeostasis. Nonetheless, the nature of inflammation in EB wounds is poorly understood, and the transition from acute to nonresolving inflammation remains to be elucidated. Neutrophils are the most abundant leucocyte subset, and are rapidly recruited to sites of injury as the principal cellular effectors of the inflammatory and immune responses, with their antimicrobial functions executed via a range of mechanisms, including phagocytosis, release of chemokines and proteases, and the production of reactive oxygen species (ROS) and neutrophil extracellular traps. However, neutrophils are now known to contribute to wound healing under both nonsterile and sterile conditions, influencing the resolution of inflammation and stimulating tissue repair. Conversely, dysfunctional neutrophils may provoke delayed healing, for instance through failure to clear invading microbes in the context of diminished neutrophil influx or function, or through bystander tissue damage in the context of excessive neutrophil activation or impaired clearance. We sought to characterize comprehensively the contribution of circulating neutrophils to wound healing across three major EB types: EB simplex (EBS), junctional EB (JEB) and dystrophic EB (DEB). Peripheral blood neutrophils were isolated via discontinuous density gradient centrifugation and analysed by fluorescence- and luminescence-based assays to explore neutrophil antimicrobial function and apoptosis in response to physiological and experimental stimuli. Our preliminary data demonstrate a diverse spectrum of neutrophil activity across EB types, with distinct clustering of data depicting greater ROS generation in the JEB cohort, and high rates of apoptosis in DEB vs. EBS and healthy controls. The differential neutrophil behaviour illustrated may contribute to the observed phenotype across major EB types, and possibly influences delayed healing via differing mechanisms. Ongoing work to further define the significance of this neutrophil activity across EB types may unveil novel therapeutic targets that can be exploited to modulate neutrophil function and the wound microenvironment to accelerate healing in EB.