In Europe ≈15,000 patients receive larval therapy for wound treatment annually. Over the past few years, clinical studies have demonstrated the success of larvae of Lucilia sericata as debridement agents. This is based on a combination of physical and biochemical actions. Laboratory investigations have advanced our understanding of the biochemical mechanisms underlying the beneficial effects of larval secretions, including removal of dead tissue, reduction of the bacterial burden, and promotion of tissue regeneration. The present article summarizes our current understanding of the microbiological, immunological, and wound healing actions of larval therapy, and the molecules involved in these beneficial effects. Future studies will focus on the isolation, identification, and (pre)clinical testing of the effective molecules of L. sericata larvae. These molecules may be candidates for the development of new agents for the treatment of several infectious and inflammatory diseases, including chronic wounds.

Abbreviations

bFGF: basic fibroblast growth factor
fMLP: N-formyl-methionine-leucine-phenylalanine
IL: interleukin
LPS: lipopolysaccharide
LTA: lipoteichoic acid
MDT: maggot debridement therapy
MIF: macrophage inhibitory factor
MIP: macrophage inflammatory protein
PDGF: platelet-derived growth factor
TIME: tissue, infection/inflammation, moisture imbalance, wound edge
TNF: tumor necrosis factor
tPA: tissue-type plasminogen activator
uPA: urokinase-type plasminogen activator
VEGF: vascular endothelial growth factor

Introduction

Larval therapy displays important benefits in the management of chronic, infected wounds, and is used in hundreds of clinics worldwide 1-3. Since ancient times, people were aware that larvae of certain Dipteran flies, e.g. the green-bottle fly Lucilia sericata, cleaned and disinfected wounds. Evidence for the use of larvae to heal wounds has been found on paintings from tribes of the Mayas in Central America and aboriginals in Australia and the first written description of beneficial effects of larvae was from Baron D.J. Larrey, inspector-general of the medical department of Napoleon's army 4, 5. Further observations of the beneficial effects of larvae were communicated by the Confederate Army surgeons J. Joseph and J.D. Zacharias, the latter intentionally introduced larvae into wounds for debridement 6. In 1929, William Baer, a consultant orthopaedic surgeon at the Johns Hopkins Hospital in Baltimore, reported that for the treatment of children with osteomyelitis, larvae of L. sericata could (1) rapidly debride, (2) reduce bacterial counts, and (3) decrease odor and alkalinization of the wound surface 7. However, the reports of Baer were only transiently noticed due to the discovery of penicillin by Alexander Fleming in 1928 8. Larval therapy became obsolete when industrially produced penicillin was introduced in clinics by the early 1940s. However, due to a rise in antibiotic resistance and failure of modern wound care to heal many chronic, infected wounds, medicinal larvae were reintroduced in the late 1980s 9. The US Food and Drug Administration approved Maggot Debridement Therapy (MDT) (510(k) #33391) in 2004 and described the indication for MDT as follows: “For debriding non-healing necrotic skin and soft tissue wounds, including pressure ulcers, venous stasis ulcers, neuropathic foot ulcers, and non-healing traumatic of post surgical wounds.” (http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpcd/classification.cfm?ID=5372). The debridement efficacy of MDT has been proven in randomized clinical studies, although there is no evidence in these studies that larvae influence the time to wound closure 10, 11. However, many other beneficial effects of larvae and their secretions on wounds have been observed. While wound debridement by larvae has been extensively reviewed by others 12, 13, this review focuses on the potential other beneficial effects of larvae and their secretions, such as antibacterial effects, reduced inflammation, neo-angiogenesis and improved wound healing 14-20.

Larvae influence wound bed preparation

An example of a patient receiving larval therapy is presented in Fig. 1. The photographs show the foot of a 48-year-old male patient with diabetes, who suffered a burn wound caused by a heating stove. An X-ray also showed osteomyelitis of the calcaneus. The wound did not exhibit a tendency to heal despite intensive (antibiotic) therapy for two months. A characteristic debris, resulting from chronic inflammation, was also present on the wound bed (Fig. 1A). After two applications of larvae, all debris was removed (Fig. 1B) and after four applications the wound progressed (Fig. 1C) and healed completely within four months (Fig. 1D). An X-ray also showed that the osteomyelitis had been cleared.

Details are in the caption following the image — **Figure 1**
Open in figure viewer PowerPoint

Photographs of a 48-year-old patient with diabetes, and a burn wound on his foot. His calcaneus was affected by osteomyelitis. A: Before starting larval therapy. B: After two applications of larvae, the wound has been debrided and well granulated. A tendon is visible at the right site of the wound. C: Wound healing progression one month after larval therapy. D: Wound closure four months after larval therapy. Photographs were taken by Gerrit Kracht, Leiden University Medical Center, The Netherlands.

Obviously, wound conditions in patients vary a lot and not a single case is identical or comparable. To describe the wound situation of individual patients in the context of their underlying diseases, and to provide the basis for the removal of barriers to healing, the holistic clinical concept of wound bed preparation was developed over ten years ago 21. The definition of wound bed preparation, described in the article by Schultz et al. is: “the management of the wound to accelerate endogenous healing or to facilitate the effectiveness of other therapeutic measures.” The TIME acronym was introduced to facilitate the understanding of wound bed preparation. It stands for Tissue (non-viable), Infection or inflammation, Moisture imbalance, and wound Edge (EWMA Position Document. 2004. Wound bed preparation in practice. http://ewma.org/fileadmin/user_upload/EWMA/pdf/Position_Documents/2004/pos_doc_English_final_04.pdf). Recently, the TIME concept was reviewed by Leaper et al. 22 who concluded that, although there are many new developments in the field of wound healing, the basic concept is still extremely relevant.

Larval therapy is thought to have an effect on at least three of these components: it removes non-viable tissue effectively, it helps combat infection by reducing the bioburden, and it may facilitate the remodeling processes. As a consequence of these effects, moisture balance might also be normalized, as excessive exudation is often caused by infection, slough, and dead tissue on the wound surface, and tissue fluid resulting from inflammation 21.

Larval therapy is considered a suitable treatment modality to remove barriers to healing and prepare chronic wounds either for spontaneous healing or further interventions. Medicinal larvae are available as free-range, which are suitable for cavity wounds with undermined edges, and as so-called bagged larvae where they are contained in a sealed net dressing. The netting allows for free flow of larval secretions and the physical removal of solubilized eschar and slough, on which they feed. Medicinal larvae can stay on the wound for up to four days and the application of fresh larvae is recommended, should one treatment cycle not result in a clean and well-granulated wound bed.

Larvae of L. sericata are widely applied to treat chronic, infected wounds 1-3, 23-25. In Europe, ≈15,000 patients are treated annually. Despite clinical observations of beneficial effects of larvae in wound treatment since ancient times, their mechanisms of action are only recently becoming better understood. Investigations into the biological mechanisms that underlie the clinical effects of larval therapy have led to the identification and isolation of several molecules that exhibit proteolytic, antimicrobial, and growth-promoting activities 26-30. The scope of this review is to obtain insight into our current understanding of the microbiological, immunological, and wound healing actions of larval therapy and the identification of the molecules involved in these actions.

Cellular and biochemical processes regulate physiological wound healing

The physiological process of wound healing consists of three stages: inflammation, tissue proliferation, and tissue remodeling 31. Wounding immediately initiates various processes including clot formation to stop loss of fluids, and an inflammatory response. During the inflammatory phase, which normally lasts five days, complement components, cytokines, chemokines, enzymes, extracellular matrix proteins and growth factors, as well as inflammatory cells, including polymorphonuclear neutrophils, arrive at the injury site 32. Production of growth factors and chemokines by macrophages stimulates angiogenesis and attracts cells that are necessary for the next phase of wound healing: the proliferative phase. This phase may start a day or two after wounding and can last for a maximum of three weeks, during which time new stromal tissue, called granulation tissue, is formed. This process involves the migration of endothelial cells to the injury site and the accumulation of fibroblasts 31. The fibroblasts contribute collagen on the wound bed, and secrete the principal components of the extracellular matrix, such as fibronectin and hyaluron. Simultaneously, neovascularization occurs, while part of the fibrin clots and extracellular matrix are degraded. Besides endothelial cells and fibroblasts, granulation tissue comprises blood vessels, inflammatory cells, and myofibroblasts that cover the wound bed during the inflammatory and proliferative phase 31, 33. Myofibroblasts cause wound contraction and reduce the size of the wounded area. At the end of the second phase, granulation tissue is fully replaced by collagen and epithelial cells migrating onto the wound area. The epithelial cells degrade the remaining fibrin clots and extracellular matrix and once the wound surface is covered by keratinocytes, they begin to secrete proteins that form a new basement membrane. During this remodeling phase of the wound, redundant cells die by apoptosis and collagen is remodeled and re-aligned 31, 32. The remodeling phase can last up to two years.

How is wound healing disturbed in chronic wounds?

Prolonged inflammation or infection, and imbalance of moisture and/or deleterious composition of wound fluid can lead to impaired healing 31. As a result of these disturbances, chronic wounds are often characterized by slough and necrosis (debris) on the wound bed. Persistent influx of neutrophils into the wound bed associated with an elevated level of proteolytic activity, and unbalanced oxidant/antioxidant levels cause damage of the surrounding tissue rather than repair 31. Effective debridement, e.g. by larvae and their secretions, is thus essential to facilitate and continue the process of wound healing 33. In addition, larvae and their secretions affect the inflammatory and the wound healing processes 14, 15, 19, 20, 30. These combined actions may establish an optimal wound bed preparation.

Which beneficial actions do Lucilia sericata larvae and their secretions show in vitro?

Larvae produce antibacterial factors

The presence of a potential antibacterial entity in the elimination products of larvae was first described in the 1930s 34. Numerous studies have since investigated the antibacterial activity in larval secretions against both Gram-positive and Gram-negative bacteria, with inconsistent findings. While some studies have revealed that larvae and their secretions are poorly effective against Staphylococcus aureus and even less effective against Gram-negative bacteria, such as Pseudomonas aeruginosa and Acinetobacter baumannii 35, 36, others have identified antimicrobial molecules within larvae and their secretions 16, 17, 27, 28, 37-40. The reasons for this apparent discrepancy are not entirely clear, but may include different methods to collect larval secretions 41, the type of assay 39, 41, and bacterial species 37 to detect the antimicrobial effects, as well as the use of different concentrations of secretions 42. For example, Bexfield et al. 39 collected secretions from sterile larvae and applied them in different types of antibacterial activity assays. The zone of inhibition assay did not allow for the detection of any antibacterial activity within larval secretions, whereas a turbidometric assay assessing bacterial growth demonstrated significant antibacterial activity against a number of bacterial species including S. aureus and Escherichia coli. However, no effect of larval secretions on S. aureus and P. aeruginosa survival has been seen using in vitro killing assays 36 as well as MIC assays 35. P. aeruginosa was even shown to be toxic to L. sericata 43. Of note, Mumcuoglu et al. 44 have shown that larvae can ingest fluorescent bacteria, and subsequently the amount of fluorescent bacteria was reduced in their gastrointestinal tract, suggesting that the bacteria were destroyed. In contrast, Daeschlein et al. 45 assessed the ability of larvae to ingest and excrete bacteria and found that within 48 hours viable bacteria could still be found in the gut of larvae. Furthermore, it has recently been reported that the depletion of bacterial quorum-sensing-controlled virulence genes results in an increased uptake of bacteria by larvae 43.

Several antimicrobial molecules have been isolated from L. sericata in the last few years 16, 17, 27, 28, 37-41. For example, a study on the structural characterization and antimicrobial activities of compounds released externally by L. sericata revealed the presence of a diversity of antimicrobial compounds 46. These compounds were categorized into two groups: polypeptides (between 6,466 and 9,025 Da) and small molecules (between 130 and 700 Da). Whilst some of these molecules corresponded well to known insect antimicrobial peptides, such as lucifensin 37, 38 and MAMP 40, other antibacterial molecules present in the secretions had no clear homology to existing analogues, and therefore warranted further investigation. Recently, a <500 Da fraction of larval secretions was shown to be active against many pathogenic strains of bacteria (Staphylococcus sp., Bacillus sp., E. coli, Pseudomonas sp., Proteus sp., Enterococcus sp., Enterobacter sp., etc.), and 12 out of 15 clinical isolates of MRSA 16. The mass and empirical formula of this active antibacterial agent has been accurately determined as C₁₀H₁₆N₆O₉, and the molecule is patented and registered as a novel antibiotic, Seraticin® 47. The molecular structure of Seraticin® is currently being investigated allowing for chemical synthesis. The mode of action, minimal inhibitory concentrations and determination of molecular target(s) are also currently being studied (Nigam Y. et al., unpublished). Thus, the presence of antibacterial molecules present in the secretions of L. sericata has now been universally accepted. For convenience, the antibacterial effects within larvae are summarized in Table 1.

Table 1. The antibacterial and antibiofilm effects of larval secretions

Microorganism	Molecule	Effect	Reference
Planktonic bacteria
Micrococcus luteus, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Enterococcus spp. and Enterobacter spp.	Lucifencin, MAMP, and seraticin	Inhibits bacterial multiplication	Cerovsky et al. 38; Zhang et al. 40; Bexfield et al. 39
Bacterial biofilm formation
Staphylococcus aureus, Pseudomonas aeruginosa	Not identified	Inhibition	Cazander et al. 35; Van der Plas et al. 36
Staphylococcus aureus, Staphylococcus epidermidis	Chymotrypsin	Inhibition	Harris et al. 56
Break down bacterial biofilm
Staphylococcus aureus, Pseudomonas aeruginosa	Not identified	Degradation	Cazander et al. 35; Van der Plas et al. 36
Staphylococcus epidermidis	Chymotrypsin	Degradation	Harris et al. 56
Pseudomonas aeruginosa	DNase	Degradation	Brown et al. 58
Combination with antibiotics
Daptomycin against biofilm-derived Staphylococcus aureus	Not identified	Enhances antimicrobial effect	Van der Plas et al. 54
Gentamicin and flucloxacilin against Staphylococcus aureus	Not identified	Enhances antimicrobial effect	Cazander et al. 55

No effect of larval secretions was found on planktonic Staphylococcus aureus, Streptococcus pyogenes, Enterococcus faecalis, Pseudomonas aeruginosa, Klebsiella oxytoca in the studies from Cazander et al. 35 and Van der Plas et al. 36.

Can antibacterial activity in larvae be induced?

Initial studies suggested that expression of antibacterial molecules present in larval secretions may be inducible rather than constitutive 17, 48. For example, a three- to six-fold increase in antibacterial activity was found with larvae removed from chronic wounds as compared to sterile larvae 17. In agreement, Kawabata et al. 48 showed that infected larvae had greater antibacterial capacities than sterile larvae. These researchers argued that the clinical wound situation would enable larvae in their infected environment to influence the production of their antibacterial activities. However, this hypothesis has not been confirmed in a clinical trial 10. The inducibility of the antibacterial activity in larvae needs to be further investigated in future research.

Larval secretions reduce bacterial biofilms

Adherent bacteria in wounds may form microcolonies that produce a tough and protective layer called a biofilm. Biofilm-associated infections are notoriously difficult to treat; many topical treatments are ineffective and antibiotics often fail to destroy bacteria in the biofilm 49. It has been hypothesized that bacterial biofilms play a major role in wound colonization and infection 50. In agreement, 60% of chronic wound specimens taken from 77 subjects were shown to contain a biofilm, as opposed to 6% of specimens taken from acute wounds 51. Nowadays, it is widely accepted that bacterial biofilms contribute to the chronicity of wounds 22, 49.

In this connection, several researchers have shown that larval secretions disrupt established biofilm 51-53. Moreover, it was found that larval secretions not only break down established biofilms, but also prevent the biofilm formation on abiotic surfaces (polyethylene, surgical stainless steel, and titanium) 52, 53 and biotic surfaces, e.g. dermal pig skin explants 49. Larval secretions degraded biofilms of P. aeruginosa at 10-fold higher concentrations than the effective concentration used to degrade S. aureus biofilms 54. Together, larval secretions display anti-biofilm activities (Table 1), resulting in the release of bacteria from the biofilm thus allowing the bacterial cells exposure to the actions of the immune systems and antibiotics. In this connection, it has been demonstrated that larval secretions do not affect the antibacterial action of many antibiotics and that at high concentrations secretions enhanced the action of several antibiotics, such as daptomycin, gentamicin, and flucloxacillin 54, 55.

Recently, chymotrypsin derived from larval secretions was found to be responsible for the disruption of protein-dependent bacterial biofilm formation mechanisms, and the greatest effect of recombinant chymotrypsin was seen on nascent and established biofilms of S. epidermidis 5179-R1 56. Furthermore, chymotrypsin degrades macromolecules in venous leg ulcer slough, and this activity persists in an environment with intrinsic gelatinase activity, such as a (chronic) wound 57. Besides, anti-biofilm activities may be mediated by a DNAse, which is contained in larval secretions. Of note, both DNA from slough/eschar of venous leg ulcers and bacterial DNA was digested by the purified DNAse 58.

To further verify the potential inducible nature of the expression of molecules with antibiofilm activities within L. sericata secretions, researchers have recently demonstrated that externalized secretions collected from larvae pre-treated with bacteria, dose-dependently prevented the formation, and initiated the breakdown of P. aeruginosa biofilm 59.

To conclude, it appears that larval secretions contain at least two different molecules, chymotrypsin and DNAse, that are able to prevent bacterial biofilm formation and break down established biofilms.

Larval secretions inhibit inflammatory processes

The complement system is part of the innate immune defense, and complement activation plays an important role in the activation of the inflammatory response to injury. Invading organisms or tissue injury activate the complement cascades via three pathways: the classical pathway, the alternative pathway and the lectin pathway 60, 61. The result of activation of any of these pathways is cleavage of central factor C3 into C3a and C3b by C3 convertase. Finally the terminal pathway of the complement system with factors C5b to C9 is reached. These factors form the membrane attack complexes, which form pores in the microbial wall resulting in cell lysis 62, 63.

While complement activation is needed for the tissue healing process, inappropriate complement activation can result in prolonged inflammation and can therefore cause injury and contribute to further tissue damage 60-63. Clinical studies show enhanced levels of complement activating factors in chronic wounds 64-67, and it has been shown that animals with a genetic complement deficiency, or individuals treated with a complement inhibitor, are protected from the symptoms resulting from chronic inflammatory processes 68-71.

Improved healing of chronic, inflamed, or infected wounds is observed when larval therapy is used in clinical practice. Based on the consideration that overactivation of the complement system impairs the wound healing process, it was hypothesized that larval secretions interfered with complement components. An in vitro study investigated the effect of larval secretions on final complement activation in healthy and post-operatively obtained donor sera 15. The principal finding was that all tested secretions clearly reduced complement activation in healthy and immune-activated sera. A dose-dependent correlation between the protein concentrations of secretions and their complement activation reducing effect was shown 15.

The mechanism underlying this observation most probably involves breakdown of individual complement components 15. These findings may explain part of the improved wound healing during larval application and, furthermore, could provide new insights into the role of complement activation in the development and maintenance of chronic wounds. Ultimately, the complement-inhibitor(s) present in larval secretions, that are currently being isolated, could provide a novel treatment modality for diseases, resulting from an (over)active complement system, e.g. (chronic) infections, ischemic-reperfusion injury, and severe inflammatory response syndrome.

Regarding the effect of larvae and their secretions on the cells of the inflammatory response, such as neutrophils, monocytes, and macrophages, Van der Plas et al. focused on the production and release of enzymes, i.e. elastase, and reactive oxygen intermediates, such as hydrogen peroxide, generated by human neutrophils. These products induce tissue damage and thus enhance the inflammatory response 14. The results revealed that larval secretions dose-dependently reduced the production and release of elastase and hydrogen peroxide by neutrophils in response to chemotactic and activating stimuli 14. Moreover, secretions also inhibited the fMLP-induced chemotaxis of neutrophils, indicating that larval secretions may reduce the influx of these inflammatory cells into the sites of infections 14. It was found that secretions did not affect the phagocytosis and intracellular killing of S. aureus and Candida albicans by human neutrophils and monocytes 14, 30. In addition to clearing micro-organisms from infected sites, monocytes and macrophages produce an array of factors mediating the inflammatory response as well as healing the wound. Larval secretions dose-dependently reduced the production of pro-inflammatory cytokines, such as IL-12, TNF-alpha, and MIF, by monocytes and pro-inflammatory macrophages, while enhancing the production of anti-inflammatory cytokines, such as IL-10 14, 30.

In summary, larval secretions break down several complement components which result in a decrease of complement activation 15. Furthermore, secretions reduce multiple neutrophil pro-inflammatory responses 14. The various immunomodulatory effects of larval secretions are summarized in Table 2.

Table 2. Effects of larval secretions on molecules and cells of the immune systems and cells involved in wound repair

Inflammatory component	Molecule	Effect	Reference
Complement system
Classical, alternative, and lectin pathways	Not identified	Inhibition	Cazander et al. 15
Neutrophils
FMLP-induced chemotaxis, elastase release, and hydrogen peroxide production	Not identified	Inhibition	Van der Plas et al. 14
Monocytes
LPS cytokine production	Not identified	Increase in IL-8, IL-10, MCP; no effect on IL-1β, Il-6; decrease in IL-12, TNFα, MIF	Van der Plas et al. 29
LTA cytokine production	Not identified	Decrease in IL-12, TNFα, increase in IL-10	Van der Plas et al. 29
Monocyte-macrophage differentiation	Not identified	Decrease in LPS-stimulated IL-12, TNFα, MIF, MIP-1β, and RANTES; increase in IL-6, IL-8, MCP-1; no effect on IL-10 by type 1 and 2 macrophages; increase in bFGF and VEGF, but not PDGF, by type 2, but not type 1, macrophages	Van der Plas et al.30
Keratinocytes, fibroblasts	Serine proteinase	Enhances fibroblast migration	Horobin et al. 20, 72
Angiogenesis	Small organic compounds, e.g L-histidine, L-valinol, and 3-guanidino-propionic acid	Enhances vascular endothelial cell migration	Bexfield et al. 18
Eschar	Chymotrypsin	Degrades wound eschar	Telford et al. 26 and Pritchard et al. 57
Eschar	DNase	Degrades DNA associated with eschar	Brown et al. 58

No effect of larval secretions was found on phagocytosis and intracellular killing of Candida albicans 14 and Staphylococcus aureus 29.

Larval secretions affect fibroblast migration, angiogenesis, and growth factor production

Fibroblasts migrate from the edge of the wound and from the dermis to the wound bed to promote healthy tissue formation. Serine protease activity within larval secretions has a significant effect on the motogenesis of fibroblasts in two-dimensional and three-dimensional cultures, and on keratinocytes 20, 72-75. In addition, it has recently been shown that larval secretions may exert pro-angiogenic effects by activating a key signaling pathway involving PI3K and AKT1 76. It is possible that this signal pathway is also linked to the induction of motogenesis of fibroblasts, given the observation of increased phosphotyrosine expression at the migrating cell front during ex vivo wound healing. Wang et al. 76 showed that human microvascular epidermal cells, which were exposed to larval secretions, significantly increased their migration via the PI3K:AKT1 protein kinase pathway, and that P13K itself was activated by many pro-angiogenic factors. The authors suggest that these observed positive wound healing effects, clinically demonstrable in a wound treated with larvae, may be due, in part, to their role in the activation of this pathway.

In addition, amino acids L-histidine, 3-guanidinopropionic acid, and L-valinol, were recently identified within larval secretions, each exhibiting significant pro-angiogenic effects on a human endothelial cell line 18. Valinol in particular, caused an increase in cell density by 25% after a 48-hour exposure. None of the three amino acids stimulated fibroplasia, confirming that these components did not affect fibroblast growth or motility, but were specifically acting to promote the growth of blood cells 18. Other researchers have also reported the pro-angiogenic activity of larval secretions. Zhang et al. 19 used dried extracts of L. sericata larvae on dermal excision wounds, and showed a significant increase in the up-regulation of VEGF expression (VEGFA mRNA and VEGFA protein expression) after three days of treatment. In agreement, Van der Plas et al. 30 found that larval secretions enhanced the production of growth factors, such as VEGF and bFGF, by monocytes and macrophages. Other researchers too, report that larval secretions enhance the expression of bFGF in ulcers 77. Growth factors in combination with low levels of pro-inflammatory cytokines such as TNF-alpha, are involved in endothelial cell migration and proliferation, which are essential for angiogenesis 78. It appears, therefore, that larval secretions stimulate fibroblast and keratinocyte migration 20, 72, exert pro-angiogenic effects 18, 78, and increase the production of growth factors 19, 30, 78.

Larval secretions influence matrix composition and turn-over

Immediately after injury the coagulation system is activated to stop hemorrhage. Subsequently the fibrinolytic system is triggered to break down clots and other extracellular matrices. Experiments have revealed that blood clot formation is not affected by larval secretions, whereas the secretions enhance the conversion of plasminogen by urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA) into plasmin, which degrades fibrin deposits (Van der Plas MJA, Andersen AS, Nazir S, van Tilburg NH, et al. 2013, unpublished).

In wounds, migrating fibroblasts create a provisional matrix on the wound bed, comprising fibronectin and hyaluron as principal components 31, 32. This provisional matrix is essential for cell migration over the wound bed in a balanced wound. However, in a chronic wound, this matrix may be partially degraded by proteolytic enzymes derived from inflammatory cells such as neutrophils and macrophages 31. Unfortunately, the remaining fibrin deposits (slough) no longer support cell migration and granulation tissue formation and even inhibit these cellular responses. Moreover, slough is a rich source for bacteria. Obviously, molecules within larval secretions such as chymotrypsin 26, 57 together with the enhancing effect of sericase on fibrinolytic system in chronic wounds may promote wound healing by removal of slough.

Bioactive molecules from larvae are being isolated for future therapy

Larvae are successfully used to treat necrotic, sloughly, and infected wounds, either as free-range larvae or larvae contained in a biobag (success ranges from 80% to over 95% in wounds that failed to heal with conventional treatments) 79, 80. Unfortunately, therapy with live larvae is sometimes hampered by the so-called “yuk factor” 81 and the acceptance could be improved by the use of recombinant or synthetically produced bioactive molecules from the larvae and/or larval secretions 82. Of course, possible systemic effects of therapy with such larval derived molecules should be investigated in order to establish whether adverse effects occur. Importantly, no severe side effects, especially no immune reactions, have been reported in relation to larval therapy so far 83. The beneficial effects of larval therapy beyond debridement, in particular the antiseptic, anti-inflammatory and wound healing effects (Fig. 2), should be investigated in clinical trials. Since larval secretions contain many components that may affect the molecules and cells responsible for the poor healing of chronic wounds, isolation, and characterization of the various bio-active molecules is complex. Nevertheless several active components have been identified by others and ourselves (Tables 1 and 2), but many other molecules with beneficial activities within larval secretions still need to be identified and characterized 14, 15, 18, 52, 53, 84. For this purpose, various chromatographic techniques and mass spectrometry, recombinant technology, and synthetic chemistry combined with functional assays have been successful. These strategies should also be instrumental in the identification of other bioactive components within larval secretions. In this connection, we are currently identifying the molecules in larval secretions with antibiofilm activity and those inhibiting the complement pathways. To aid in the identification and production of these potentially therapeutical agents within larval secretions, the transcriptome and genome of L. sericata should be available. Next generation sequencing could produce these data for medicinal larvae. Recently, researchers have reported the transcriptome of L. sericata 85 and this may be helpful in the identification of bioactive proteins within larval secretions. In addition, performing BLAST between the transcriptome and the reads and contigs of the whole body genome of L. sericata should show that all genes expressed in the transcriptome align with a match in the genome. This information assists in de novo assembly of L. sericata's genome.

Conclusions

Clinical studies (RCTs) have proven the value of larvae as debridement agents 10, 11, while several other beneficial effects of larvae on wounds, including anti-infection, immunomodulation, angiogenesis, and tissue remodeling and regeneration, have been widely reported clinically and supported by numerous in vitro studies 14-20. Several molecules have been isolated from L. sericata larval secretions, such as lucifensin 37, MAMP 40, Seraticin® 47, DNAse 58, chymotrypsin 26, 78, 86, sericase (Van der Plas MJA, Andersen AS, Nazir S, van Tilburg NH, et al., 2013, unpublished) and other bioactive compounds 18, 75. Furthermore, larval secretions contain at least two different molecules that are able to prevent bacterial biofilm formation and break down established biofilms 56, 58. In addition, several molecules within larval secretions decrease complement activation by breaking down individual complement components 15. In terms of wound healing abilities, larval secretions enhance the production of growth factors by monocytes and macrophages in the wound 30. We conclude that together, the actions of these molecules and most likely several others in larval secretions are responsible for the beneficial effects of larval therapy (Fig. 2).

Why do larvae produce molecules that promote healing of hard-to-heal wounds? Larvae secrete an array of enzymes to digest dead tissue and it may well be that these enzymes also break down various host molecules within the wound. In addition, larvae may produce antibacterial molecules to survive in an environment heavily contaminated by bacteria that compete with the larvae for their nutritional source. Moreover, the bacteria may be harmful for larvae 43. By reducing the bacterial load, larvae may not only control the process of decay, but also protect themselves against pathogenic bacteria. In addition, larval survival in wounds may depend on their mechanisms to suppress the host's immune responses, which may itself be detrimental to larvae.

In order to promote larval therapy, to produce therapeutic agents from larval secretions for medical purposes, and to stimulate research into the mechanisms underlying the beneficial actions of larval therapy, the authors joined forces during the first meeting of the European Larval Therapy Research Group earlier this year. This review is the first product from this initiative. Currently, the European Larval Therapy Research Group is focusing on the effective molecules of L. sericata larvae that could be used for treatment of several infectious and inflammatory diseases, including chronic wounds.

Conflict of interest

One of the authors, Dr. W. Jung, works for Biomonde GmbH, Barsbüttel, Germany, a production company of larval products. None of the other authors has any potential conflict of interest related to this manuscript.

References

1 Sherman RA, Hall MJR, Thomas S. 2000. Medicinal maggots: an ancient remedy for some contemporary afflictions. Annu Rev Entomol 45: 55–81.
10.1146/annurev.ento.45.1.55
CAS PubMed Web of Science® Google Scholar
2 Steenvoorde P, Jukema GN. 2004. The antimicrobial activity of maggots: in-vivo results. J Tissue Viability 14: 97–101.
10.1016/S0965-206X(04)43005-8
CAS PubMed Google Scholar
3 Wollina U, Liebold K, Schmidt WD, Hartmann M, et al. 2002. Biosurgery supports granulation and debridement in chronic wounds – clinical data and remittance spectroscopy measurement. Int J Dermatol 41: 635–9.
10.1046/j.1365-4362.2002.01354.x
CAS PubMed Web of Science® Google Scholar
4 Fleischmann W, Grassberger M, Sherman RA. 2003. A Handbook of Maggots-Assisted Wound Healing. New York: Thieme.
Google Scholar
5 Larrey DJ. 1832. Observations on wounds, and their complications by erysipelas, gangrene and tetanus etc. Translated from the French by EF Rivinus, Philadelphia Key, Mielke and Biddle.
Google Scholar
6 Donnelly J. 1998. Wound healing – from poultices to maggots. A short synopsis of wound healing throughout the ages. Ulster Med J 67: 47–51.
PubMed Google Scholar
7 Baer WS. 1931. The treatment of chronic osteomyelitis with the maggot (larva of the blow fly). J Bone Joint Surg Am 13: 438–75.
Google Scholar
8 Chain E, Florey HW, Gardner AD, Heatley HG, et al. 1940. Penicillin as a chemotherapeutic agent. Lancet 2: 226–8.
10.1016/S0140-6736(01)08728-1
CAS Web of Science® Google Scholar
9 Sherman RA, Pechter EA. 1988. Maggot therapy: a review of the therapeutic applications of fly larvae in human medicine, especially for treating osteomyelitis. Med Vet Entomol 2: 225–30.
10.1111/j.1365-2915.1988.tb00188.x
CAS PubMed Web of Science® Google Scholar
10 Dumville JC, Worthy G, Bland JM, Cullum N, et al. 2009. Larval therapy for leg ulcers: randomised controlled trial (VenUS II). Br Med J 338: b773.
PubMed Web of Science® Google Scholar
11 Opletalová K, Blaizot X, Mourgeon B, Chêne Y, et al. 2012. Maggot therapy for wound debridement. A randomized multicentre trial. Arch Dermatol 148: 432–8.
10.1001/archdermatol.2011.1895
PubMed Web of Science® Google Scholar
12 Zarchi K, Jemec GB. 2012. The efficacy of maggot debridement therapy – a review of comparative clinical trials. Int Wound J 9: 469–77.
10.1111/j.1742-481X.2011.00919.x
PubMed Web of Science® Google Scholar
13 Hall S. 2010. A review of maggot debridement therapy to treat chronic wounds. Br J Nurs 19: S26, S28–31.
10.12968/bjon.2010.19.Sup5.77705
PubMed Google Scholar
14 Van der Plas MJA, van der Does AM, Baldry M, Dogterom-Ballering HCM, et al. 2007. Maggot secretions/excretions inhibit multiple neutrophil pro-inflammatory responses. Microb Infect 9: 507–14.
10.1016/j.micinf.2007.01.008
CAS PubMed Web of Science® Google Scholar
15 Cazander G, Schreurs MWJ, Renwarin L, Dorresteijn C, et al. 2012. Maggot excretions affect the human complement system. Wound Rep Regen 20: 879–86.
10.1111/j.1524-475X.2012.00850.x
CAS PubMed Web of Science® Google Scholar
16 Bexfield A, Bond AE, Roberts EC, Dudley E, et al. 2008. The antibacterial activity against MRSA strains and other bacteria of a <500 Da fraction from maggot excretions/secretions of Lucilia sericata (Diptera: Calliphoridae). Microbes Infect 10: 325–33.
10.1016/j.micinf.2007.12.011
PubMed Web of Science® Google Scholar
17 Huberman L, Gollop N, Mumcuoglu KY, Block C, et al. 2007. Antibacterial properties of whole body extracts and haemolymph of Lucilia sericata maggots. J Wound Care 16: 123–7.
10.12968/jowc.2007.16.3.27011
CAS PubMed Google Scholar
18 Bexfield A, Bond AE, Morgan C, Wagstaff J, et al. 2010. Amino acid derivatives from Lucilia sericata excretions/secretions may contribute to the beneficial effects of maggots therapy via increased angiogenesis. Br J Dermatol 162: 554–62.
10.1111/j.1365-2133.2009.09530.x
CAS PubMed Web of Science® Google Scholar
19 Zhang Z, Wang S, Diao Y, Zhang J, et al. 2010. Fatty acid extracts from Lucilia sericata larvae promote murine cutaneous wound healing by angiogenic activity. Lipids Health Dis 9: 24.
10.1186/1476-511X-9-24
CAS PubMed Web of Science® Google Scholar
20 Horobin AJ, Shakesheff KM, Pritchard DI. 2005. Maggots and wound healing: An investigation of the effects of secretions form Lucilia sericata larvae upon the migration of human dermal fibroblasts over a fibronectin coated surface. Wound Repair Regen 13: 422–33.
10.1111/j.1067-1927.2005.130410.x
PubMed Web of Science® Google Scholar
21 Schultz GS, Sibbald G, Falanga V, Ayello EA, et al. 2003. Wound bed preparation: a systematic approach to wound management. Wound Rep Regen 11: S1–27.
10.1046/j.1524-475X.11.s2.1.x
PubMed Web of Science® Google Scholar
22 Leaper DJ, Schultz G, Carville K, Fletcher J, et al. 2012. Extending the TIME concept: what have we learned in the past 10 years? Int Wound J 9: 1–19.
10.1111/j.1742-481X.2012.01097.x
PubMed Web of Science® Google Scholar
23 Gottrup F, Jørgensen B. 2011. Maggot debridement: an alternative method for debridement. Eplasty 11: 290–302.
Google Scholar
24 Gilead L, Mumcuoglu KY, Ingber A. 2012. The use of maggot debridement therapy in the treatment of chronic wounds in hospitalized and ambulatory patients. J Wound Care 21: 78–85.
10.12968/jowc.2012.21.2.78
CAS PubMed Web of Science® Google Scholar
25 Thomas S. 2010. Surgical Dressings and Wound Management. Cardiff, SouthWales: Medetec, p. 563–32.
Google Scholar
26 Telford G, Brown AP, Seabra RA, Horobin AJ, et al. 2010. Degradation of eschar from venous leg ulcers using a recombinant chymotrypsin from Lucilia sericata. Br J Dermatol 163: 523–31.
10.1111/j.1365-2133.2010.09854.x
CAS PubMed Web of Science® Google Scholar
27 Kerridge A, Lappin-Scott H, Stevens JR. 2005. Antibacterial properties of larval secretions of the blowfly Lucilia sericata. Med Vet Entomol 19: 333–7.
10.1111/j.1365-2915.2005.00577.x
CAS PubMed Web of Science® Google Scholar
28 Jaklic D, Lapanje A, Zupancic K, Smrke D, et al. 2008. Selective antimicrobial activity of maggots against pathogenic bacteria. J Med Microbiol 57: 617–25.
10.1099/jmm.0.47515-0
PubMed Web of Science® Google Scholar
29 Van der Plas MJ, Baldry M, van Dissel JT, Jukema GN, et al. 2009. Maggot secretions suppress pro-inflammatory responses of human monocytes through elevation of cyclic AMP. Diabetologia 52: 1962–70.
10.1007/s00125-009-1432-6
CAS PubMed Web of Science® Google Scholar
30 Van der Plas MJA, van Dissel JT, Nibbering PH. 2009. Maggots secretions skew monocyte-macrophage differentiation away from a pro-inflammatory to a pro-angiogenic type. PLoS One 4: e8071.
10.1371/journal.pone.0008071
CAS PubMed Web of Science® Google Scholar
31 Eming SA, Krieg T, Davidson JM. 2007. Inflammation in wound repair: molecular and cellular mechanisms. J Invest Dermatol 127: 514–25.
10.1038/sj.jid.5700701
CAS PubMed Web of Science® Google Scholar
32 Gill SE, Parks WC. 2008. Metalloproteinases and their inhibitors: regulators of wound healing. Int J Biochem Cell Biol 40: 1334–47.
10.1016/j.biocel.2007.10.024
CAS PubMed Web of Science® Google Scholar
33 Wolcott RD, Kennedy JP, Dowd SE. 2009. Regular debridement is the main tool for maintaining a healthy wound bed in most chronic wounds. J Wound Care 18: 54–6.
10.12968/jowc.2009.18.2.38743
CAS PubMed Google Scholar
34 Simmons S. 1935. A bactericidal principle in excretions surgical maggots which destroys important etiological agents of pyrogenic infections. J Bacteriol 30: 253–67.
CAS PubMed Web of Science® Google Scholar
35 Cazander G, van Veen KEB, Bernards AT, Jukema GN. 2009. Do maggots have an influence on the bacterial growth? A study on the susceptibility of strains of five different bacterial species to maggots of Lucilia sericata. J Tissue Viability 18: 80–7.
10.1016/j.jtv.2009.02.005
CAS PubMed Google Scholar
36 Van der Plas MJA, Jukema GN, Wai SW, Dogterom-Ballering HCM, et al. 2008. Maggot excretions/secretions are differentially effective against biofilms of Staphylococcus aureus and Pseudomonas aeruginosa. J Antimicrob Chemother 61: 117–22.
10.1093/jac/dkm407
CAS PubMed Web of Science® Google Scholar
37 Cerovsky V, Zdarek J, Fucık V, Monincova L, et al. 2010. Lucifensin, the long-sought antimicrobial factor of medicinal maggots of the blowfly Lucilia sericata. Cell Mol Life Sci 67: 455–66.
10.1007/s00018-009-0194-0
CAS PubMed Web of Science® Google Scholar
38 Cerovsky V, Slaninova J, Fucik V, Monincova L, et al. 2011. Lucifensin, a novel insect defensin of medicinal maggots: synthesis and structural study. Chembiochem 12: 1352–61.
10.1002/cbic.201100066
CAS PubMed Web of Science® Google Scholar
39 Bexfield A, Nigam Y, Thomas S, Ratcliffe NA. 2004. Detection and partial characterisation of two antibacterial factors from the excretions/secretions of the medicinal maggot Lucilia sericata and their activity against methicillin-resistant Staphylococcus aureus (MRSA). Microbes Infect 6: 1297–304.
10.1016/j.micinf.2004.08.011
CAS PubMed Web of Science® Google Scholar
40 Zhang Z, Wang J, Zhang B, Liu H, et al. 2013. Activity of antibacterial protein from maggots against Staphylococcus aureus in vitro and in vivo. Int J Mol Med 31: 1159–65.
10.3892/ijmm.2013.1291
CAS PubMed Web of Science® Google Scholar
41 Arora S, Sing LC, Baptista C. 2009. Antibacterial activity of Lucilia cuprina maggot extracts and its extraction techniques. Int J Insect Biol 9: 43–8.
Google Scholar
42 Andersen AS, Sandvang D, Schnorr KM, Kruse T, et al. 2010. A novel approach to the antimicrobial activity of maggot debridement therapy. J Antimicrob Chemother 65: 1646–54.
10.1093/jac/dkq165
CAS PubMed Web of Science® Google Scholar
43 Andersen AS, Joergensen B, Bjarnsholt T, Johansen H, et al. 2010. Quorum-sensing-regulated virulence factors in Pseudomonas aeruginosa are toxic to Lucilia sericata maggots. Microbiology 156: 400–7.
10.1099/mic.0.032730-0
CAS PubMed Web of Science® Google Scholar
44 Mumcuoglu KY, Miller J, Mumcuoglu M, Friger M, et al. 2001. Destruction of bacteria in the digestive tract of the maggot of Lucilia sericata (Diptera: Calliphoridae). J Med Entomol 38: 161–3.
10.1603/0022-2585-38.2.161
CAS PubMed Web of Science® Google Scholar
45 Daeschlein G, Mumcuoglu KY, Assadian O, Hoffmeister B, et al. 2007. In vitro antibacterial activity of Lucilia sericata maggot secretions. Skin Pharmacol Physiol 20: 112–5.
10.1159/000097983
CAS PubMed Web of Science® Google Scholar
46 Kruglikova AA, Chernysh SI. 2011. Antimicrobial compounds from the excretions of surgical maggots, Lucilia sericata (Meigen) (Diptera, Calliphoridae). Entomol Rev 91: 813–9.
10.1134/S0013873811070013
Google Scholar
47 Nigam Y, Dudley E, Bexfield A, Bond AE, et al. 2010. The physiology of wound healing by the medicinal maggot, Lucilia sericata. Adv Insect Physiol 39: 39–81.
10.1016/B978-0-12-381387-9.00002-6
Web of Science® Google Scholar
48 Kawabata T, Mitsui H, Yokota K, Ishino K, et al. 2010. Induction of antibacterial activity in larvae of the blowfly Lucilia sericata by an infected environment. Med Vet Entomol 24: 375–81.
10.1111/j.1365-2915.2010.00902.x
CAS PubMed Web of Science® Google Scholar
49 Cowan LJ, Stechmiller JK, Phillips P, Yang Q, et al., 2013. Chronic wounds, biofilm and use of medicinal larvae. Ulcers 2013: 1–7.
10.1155/2013/487024
Google Scholar
50 Davies SC, Ricotti C, Cazzaniga A, Welsh E, et al. 2007. Microscopic and physiologic evidence for biofilm-associated wound colonization in vivo. Wound Rep Regen 16: 23–9.
10.1111/j.1524-475X.2007.00303.x
Web of Science® Google Scholar
51 James GA, Swogger E, Wolcott R, DeLancey Pulcini E, et al. 2008. Biofilms in chronic wounds. Wound Rep Regen 16: 37–44.
10.1111/j.1524-475X.2007.00321.x
PubMed Web of Science® Google Scholar
52 Cazander G, van de Veerdonk MC, Vandenbroucke-Grauls CMJE, Schreurs MWJ, et al. 2010. Maggot excretions inhibit biofilm formation on biomaterials. Clin Orthop Relat Res 468: 2789–96.
10.1007/s11999-010-1309-5
PubMed Web of Science® Google Scholar
53 Harris LG, Bexfield A, Nigam Y, Rohde H, et al. 2009. Disruption of Staphylococcus epidermidis biofilms by medicinal maggot Lucilia sericata excretions/secretions. Int J Artif Organs 32: 555–64.
10.1177/039139880903200904
CAS PubMed Web of Science® Google Scholar
54 Van der Plas MJA, Dambrot C, Dogterom-Ballering HCM, Kruithof S, et al. 2010. Combinations of maggot excretions/secretions and antibiotics are effective against Staphylococcus aureus biofilms and the bacteria derived therefrom. J Antimicrob Chemother 65: 917–23.
10.1093/jac/dkq042
CAS PubMed Web of Science® Google Scholar
55 Cazander G, Pawiroredjo JS, Vandenbroucke-Grauls CM, Schreurs MW, et al. 2010. Synergism between maggot excretions and antibiotics. Wound Repair Regen 18: 637–42.
10.1111/j.1524-475X.2010.00625.x
PubMed Web of Science® Google Scholar
56 Harris L, Nigam Y, Sawyer J, Mack D, et al. 2013. Lucilia sericata chymotrypsin disrupts protein adhesin-mediated staphylococcal biofilm formation. Appl Environ Microbiol 79: 1393–5.
10.1128/AEM.03689-12
CAS PubMed Web of Science® Google Scholar
57 Pritchard DI, Brown AP. 2013. Degradation of MSCRAMM target macromolecules in VLU slough by Lucilia sericata chymotrypsin 1 (ISP) persists in the presence of tissue gelatinase activity. Int Wound J in press, doi: 10.1111/iwj.12124.
10.1111/iwj.12124
PubMed Web of Science® Google Scholar
58 Brown A, Horobin A, Blount DG, Hill PJ, et al. 2012. Blow fly Lucilia sericata nuclease digests DNA associated with wound slough/eschar and with Pseudomonas aeruginosa biofilm. Med Vet Entomol 26: 432–9.
10.1111/j.1365-2915.2012.01029.x
CAS PubMed Web of Science® Google Scholar
59 Jiang K-C, Sun X-J, Wang W, Liu L, et al. 2012. Excretions/secretions from bacteria-pretreated maggot are more effective against Pseudomonas aeruginosa biofilms. PLoS One 7: e49815.
10.1371/journal.pone.0049815
CAS PubMed Web of Science® Google Scholar
60 Neher MD, Weckbach S, Flierl MA, Huber-Lang MS, et al. 2011. Molecular mechanisms of inflammation and tissue injury after major trauma – is complement the ‘bad guy?’ J Biomed Sci 18: 1–6.
10.1186/1423-0127-18-90
CAS PubMed Web of Science® Google Scholar
61 Trouw LR, Daha MR. 2011. Role of complement in innate immunity and host defense. Immunol Lett 138: 35–7.
10.1016/j.imlet.2011.02.014
CAS PubMed Web of Science® Google Scholar
62 Markiewski MM, Lambris JD. 2007. Biological perspectives. The role of complement in inflammatory diseases from behind the scenes into the spotlight. Am J Pathol 171: 715–27.
10.2353/ajpath.2007.070166
CAS PubMed Web of Science® Google Scholar
63 Cazander G, Jukema GN, Nibbering PH. 2012. Complement activation and inhibition in wound healing. Clin Develop Immunol 2012: 1–14.
10.1155/2012/534291
CAS Web of Science® Google Scholar
64 Balslev E, Thomsen HK, Danielsen L, Sheller J, et al. 1999. The terminal complement complex is generated in chronic leg ulcers in the absence of protectin (CD59). APMIS 107: 997–1004.
10.1111/j.1699-0463.1999.tb01502.x
CAS PubMed Web of Science® Google Scholar
65 Schmidtchen A. 2000. Degradation of antiproteinases, complement and fibronectin in chronic leg ulcers. Acta Dermato-Venereol 80: 179–84.
10.1080/000155500750042925
CAS PubMed Web of Science® Google Scholar
66 Van de Goot F, Krijnen PAJ, Begieneman MPV, Ulrich MMW, et al. 2009. Acute inflammation is persistent locally in burn wounds: a pivotal role for complement and C-reactive protein. J Burn Care Res 30: 274–80.
10.1097/BCR.0b013e318198a252
PubMed Web of Science® Google Scholar
67 Machens HG, Pabst A, Dreyer M, Gliemroth J, et al. 2006. C3a levels and occurrence of subdermal vascular thrombosis are age-related in deep second-degree burn wounds. Surgery 139: 550–5.
10.1016/j.surg.2005.09.001
PubMed Web of Science® Google Scholar
68 Yeh CG, Marsh HC, Jr, Carson GR, Berman L, et al. 1991. Recombinant soluble human complement receptor type 1 inhibits inflammation in the reversed passive Arthus reaction in rats. J Immunol 146: 250–6.
CAS PubMed Web of Science® Google Scholar
69 Mulligan SM, Yeh CG, Rudolph AR, Ward PA. 1992. Protective effects of soluble CR1 in complement- and neutrophil-mediated tissue injury. J Immunol 148: 1479–85.
10.4049/jimmunol.148.5.1479
CAS PubMed Web of Science® Google Scholar
70 Henze U, Lennartz A, Hafemann B, Goldmann C, et al. 1997. The influence of the C1-inhibitor BERINERT® and the protein-free haemodialysate ACTIHAEMYL20%® on the evolution of the depth of scald burns in a porcine model. Burns 23: 473–7.
10.1016/S0305-4179(97)00019-3
CAS PubMed Web of Science® Google Scholar
71 Begieneman MPV, Kubat B, Ulrich MMW, Hahn NE, et al. 2012. Prolonged C1 inhibitor administration improves local healing of burn wounds and reduces myocardial inflammation in a rat burn wound model. J Burn Care Res 33: 544–51.
10.1097/BCR.0b013e31823bc2fc
PubMed Web of Science® Google Scholar
72 Horobin AJ, Shakesheff KM, Pritchard DI. 2006. Promotion of human dermal fibroblast migration, matrix remodeling and modification of fibroblast morphology within a novel 3D model by Lucilia sericata larval secretions. J Invest Dermatol 126: 1410–8.
10.1038/sj.jid.5700256
CAS PubMed Web of Science® Google Scholar
73 Chambers L, Woodrow S, Brown AP, Harris PD, et al. 2003. Degradation of extracellular matrix components by defined proteinases from the greenbottle larva Lucilica sericata used for the clinical debridement of non-healing wounds. Br J Dermatol 148: 14–23.
10.1046/j.1365-2133.2003.04935.x
CAS PubMed Web of Science® Google Scholar
74 Horobin AJ, Shakesheff KM, Woodrow S, Robinson C, et al. 2003. Maggots and wound healing: an investigation of the effects of secretions from Lucilia sericata larvae upon interactions between human dermal fibroblasts and extracellular matrix components. Br J Dermatol 148: 923–33.
10.1046/j.1365-2133.2003.05314.x
CAS PubMed Web of Science® Google Scholar
75 Smith AG, Powis RA, Pritchard DI, Britland ST. 2006. Greenbottle (Lucilia sericata) larval secretions delivered from a prototype hydrogel wound dressing accelerate the closure of model wounds. Biotechnol Prog 22: 1690–6.
10.1021/bp0601600
CAS PubMed Web of Science® Google Scholar
76 Wang SY, Wang K, Xin Y, Lv DC. 2010. Maggot excretions/secretions induces human microvascular endothelial cell migration through AKT1. Mol Biol Rep 37: 2719–25.
10.1007/s11033-009-9806-x
CAS PubMed Web of Science® Google Scholar
77 Distler JH, Hirth A, Kurowska-Stolarska M, Gay RE, et al. 2003. Angiogenic and angiostatic factors in the molecular control of angiogensis. Quart J Nucl Med 47: 149–61.
CAS PubMed Web of Science® Google Scholar
78 Sunderkotter C, Steinbrink K, Goebeler M, Bhardwaj R, et al. 1994. Macrophages and angiogenesis. J Leukocyte Biol 55: 410–22.
10.1002/jlb.55.3.410
CAS PubMed Web of Science® Google Scholar
79 Thomas S, Jones M, Shutler S, Andrews A. 1996. All you need to know about maggots. Nursing Times 92: 63–76.
PubMed Google Scholar
80 Steenvoorde P, van Doorn LP, Jacobi CE, Oskam J. 2007. Maggot debridement therapy in the palliative setting. Am J Hosp Palliat Care 24: 308–10.
10.1177/1049909107302300
PubMed Google Scholar
81 Steenvoorde P, Buddingh TJ, van Engeland A, Oskam J. 2005. Maggot therapy and the “yuk” factor: an issue for the patient? Wound Repair Regen 13: 350–2.
10.1111/j.1067-1927.2005.130319.x
PubMed Web of Science® Google Scholar
82 Pritchard DI, Telford G, Diab M, Low W. 2012. Expression of a cGMP compatible Lucilia sericata insect serine proteinase debridement enzyme. Biotechnol Prog 28: 567–72.
10.1002/btpr.1516
CAS PubMed Web of Science® Google Scholar
83 Cazander G, Gottrup F, Jukema GN. 2009. Maggot therapy for wound healing: clinical relevance, mechanisms of action and future prospects. J Wound Technol 5: 18–23.
Google Scholar
84 Telford G, Brown AP, Rich A, English JS, et al. 2012. Wound debridement potential of glycosidaes of the wound-healing maggot, Lucilia sericata. Med Vet Entomol 26: 291–9.
10.1111/j.1365-2915.2011.01000.x
CAS PubMed Web of Science® Google Scholar
85 Sze S-H, Dunham JP, Carey B, Chang PL, et al. 2012. A de novo transcriptome assembly of Lucilia sericata (Diptera: Calliphoridae) with predicted alternative splices, single nucleotide polymorphisms and transcript expression estimates. Insect Mol Biol 21: 205–11.
10.1111/j.1365-2583.2011.01127.x
CAS PubMed Web of Science® Google Scholar
86 Telford G, Brown AP, Kind A, English JS, et al. 2011. Maggot chymotrypsin I from Lucilia sericata is resistant to endogenous wound protease inhibitors. Br J Dermatol 164: 192–6.
10.1111/j.1365-2133.2010.10081.x
CAS PubMed Web of Science® Google Scholar

Citing Literature

Volume35, Issue12

December 2013

Pages 1083-1092

Multiple actions of Lucilia sericata larvae in hard-to-heal wounds

Larval secretions contain molecules that accelerate wound healing, reduce chronic inflammation and inhibit bacterial infection

Abstract

Abbreviations

Introduction

Larvae influence wound bed preparation

Cellular and biochemical processes regulate physiological wound healing

How is wound healing disturbed in chronic wounds?

Which beneficial actions do Lucilia sericata larvae and their secretions show in vitro?

Larvae produce antibacterial factors

Can antibacterial activity in larvae be induced?

Larval secretions reduce bacterial biofilms

Larval secretions inhibit inflammatory processes

Larval secretions affect fibroblast migration, angiogenesis, and growth factor production

Larval secretions influence matrix composition and turn-over

Bioactive molecules from larvae are being isolated for future therapy

Conclusions

Conflict of interest

References

Citing Literature

Figures

References

Information

About Wiley Online Library

Help & Support

Opportunities

Connect with Wiley

Multiple actions of Lucilia sericata larvae in hard-to-heal wounds

Larval secretions contain molecules that accelerate wound healing, reduce chronic inflammation and inhibit bacterial infection

Abstract

Abbreviations

Introduction

Larvae influence wound bed preparation

Cellular and biochemical processes regulate physiological wound healing

How is wound healing disturbed in chronic wounds?

Which beneficial actions do Lucilia sericata larvae and their secretions show in vitro?

Larvae produce antibacterial factors

Can antibacterial activity in larvae be induced?

Larval secretions reduce bacterial biofilms

Larval secretions inhibit inflammatory processes

Larval secretions affect fibroblast migration, angiogenesis, and growth factor production

Larval secretions influence matrix composition and turn-over

Bioactive molecules from larvae are being isolated for future therapy

Conclusions

Conflict of interest

References

Citing Literature

Figures

References

Related

Information