Maggots and wound healing : the effects of Lucilia sericata larval secretions upon interactions between human dermal fibroblasts and extracellular matrix proteins
The introduction of necrophagous fly larvae (maggots) into chronic wounds for the purpose of inducing healing is an ancient practice that has recently undergone a renaissance in Western medicine. Through clinical observations, maggots are broadly recognised to debride the wound of necrotic tissue, cleanse the wound of infection and promote granulation tissue formation. Despite such recognition, little research at the biological level has been undertaken to identify the mechanisms by which maggots accomplish such feats. The dermal fibroblast is a major cellular component of granulation tissue and as such, its migration into the wound plays a vital role in new tissue growth. Fibroblast migration is directed by the composition of the extracellular matrix. Maggot secretions contain proteolytic enzymes that are active against a variety of extracellular matrix proteins which are present at the wound site. Hence, this thesis focused upon the effects of maggot secretions on human dermal fibroblast adhesion and migration in the presence of common extracellular matrix proteins. This was with the aim of elucidating the mechanisms by which maggots stimulate tissue formation within the wound and from there, developing new products that may be used to promote wound healing. Experiments showed that maggot secretions modulated fibroblast adhesion to tissue culture plastic surfaces and to surfaces coated with collagen and particularly fibronectin. Modification of the protein-coated surface by enzymes present within the secretion appeared to play a role. Fibroblast migration upon a fibronectin-coated surface was enhanced in the presence of maggot secretions. The same also occurred in the presence of a higher concentration of secretions when the cells were located within a three-dimensional environment comprising collagen gel and fibronectin. Evidence suggested that this may have been associated with enhanced matrix re-modelling.