Acute Wound Fluid Research Articles

Longitudinal Evaluation of Biomarkers in Wound Fluids from Venous Leg Ulcers and Split-thickness Skin Graft Donor Site Wounds Treated with a Protease-modulating Wound Dressing.

Venous leg ulcers represent a clinical challenge and impair the quality of life of patients. This study examines impaired wound healing in venous leg ulcers at the molecular level. Protein expression patterns for biomarkers were analysed in venous leg ulcer wound fluids from 57 patients treated with a protease-modulating polyacrylate wound dressing for 12 weeks, and compared with exudates from 10 acute split-thickness wounds. Wound healing improved in the venous leg ulcer wounds: 61.4% of the 57 patients with venous leg ulcer achieved a relative wound area reduction of ≥ 40%, and 50.9% of the total 57 patients achieved a relative wound area reduction of ≥ 60%. Within the first 14 days, abundances of S100A8, S100A9, neutrophil elastase, matrix metalloproteinase-2, and fibronectin in venous leg ulcer exudates decreased significantly and remained stable, yet higher than in acute wounds. Interleukin-1β, tumour necrosis factor alpha, and matrix metalloproteinase-9 abundance ranges were similar in venous leg ulcers and acute wound fluids. Collagen (I) α1 abundance was higher in venous leg ulcer wound fluids and was not significantly regulated. Overall, significant biomarker changes occurred in the first 14 days before a clinically robust healing response in the venous leg ulcer cohort.

Uncontrolled gelatin degradation in non-healing chronic wounds

To compare matrix metalloproteinase (MMP)-9 and the antiproteinase tissue inhibitor of metalloproteinases (TIMP)-1 in wound fluids and sera from patients with chronic non-healing or acute healing wounds. In addition, the functional consequences on MMP-9 activity and general gelatinase activity were assessed. In this observational study, samples were collected from patients with venous leg ulcers (VLUs), patients with type 2 diabetes with neuropathic foot ulcers (DFUs), and from another cohort of VLU patients with sterile split-thickness skin graft donor sites after autologous skin grafting, serving as healing control wounds. MMP-9 and TIMP-1 concentrations were determined by enzyme-linked immunosorbent assays. MMP-9 and gelatinase activities were determined in wound fluids in subsets of the patients. A total of 24 patients took part in the study. No significant differences in MMP-9 wound fluid levels were found among the three groups. TIMP-1 levels were markedly and significantly lower in the two chronic wound groups resulting in a severely unbalanced MMP-9/TIMP-1 ratio, especially notable in the VLU group and possibly in the elevated endogenous MMP-9 activity (p<0.01) compared with the acute wound fluids. At least 20% of the chronic wound fluids displayed atypical patterns on gelatin zymography and showed high general gelatinase activity that was not inhibited by either TIMP-1 or by a gelatinase inhibitor (AG3340). MMP-9 levels were higher in the sera of the patients with type 2 diabetes. We hypothesise that non-MMP proteinases contribute to matrix destruction in a significant number of chronic wounds. Blocking the excessive MMP-9 activity may be insufficient to normalise wound healing. The reasons and effects of the very low TIMP-1 levels in chronic wounds need further clarification.

Redox Profiling Reveals Clear Differences between Molecular Patterns of Wound Fluids from Acute and Chronic Wounds.

Wound healing is a complex multiphase process which can be hampered by many factors including impaired local circulation, hypoxia, infection, malnutrition, immunosuppression, and metabolic dysregulation in diabetes. Redox dysregulation is a common feature of many skin diseases demonstrated by virtually all cell types in the skin with overproduction of reactive oxygen and nitrogen species. The objective of this study was to characterize the redox environment in wound fluids and sera from patients suffering from chronic leg ulcers (n = 19) and acute wounds (bulla fluids from second degree burns; n = 11) with serum data also compared to those from healthy volunteers (n = 7). Significantly higher concentrations of TNF-α, interleukine-8, vascular endothelial growth factor, and lactate dehydrogenase (measure of cell damage) were found in fluids from chronic wounds compared to acute ones. The extent of protein carbonylation (measure of protein oxidation), lipid peroxidation, and tyrosine nitration (indicator of peroxynitrite production) was similar in acute and chronic wound fluids, while radical scavenging activity and glutathione (GSH) levels were elevated in chronic wound fluids compared to acute wounds. Sera were also assessed for the same set of parameters with no significant differences detected. Nitrotyrosine (the footprint of the potent oxidant peroxynitrite) and poly(ADP-ribose) (the product of the DNA damage sensor enzyme PARP-1) could be detected in wound biopsies. Our data identify multiple signs of redox stress in chronic wounds with notable differences. In chronic wounds, elevations in antioxidant levels/activities may indicate compensatory mechanisms against inflammation. The presence of nitrotyrosine and poly(ADP-ribose) in tissues from venous leg ulcers indicate peroxynitrite production and PARP activation in chronic wounds.

Acute and Chronic Wound Fluid Inversely Influence Wound Healing in an in-Vitro 3D Wound Model

If a wound progressively heals or the healing process is impaired is basically influenced by the surrounding milieu. This is reflected by the wound fluid. Its specific composition triggers the migration, proliferation and differentiation of dermal and epidermal cells which so far was not sufficiently examined in 2D cell culture models. The influence of the different wound entities was analyzed on a newly implemented three dimensional in-vitro model, which improved the transferability to the in-vivo situation. The influence of pooled wound fluids from patients suffering from acute or chronic wounds were investigated within a time period of 10 days after wound application. Histological and immunohistochemical analyses were performed addressing the impact of AWF and CWF on regeneration, such as cell proliferation, fibroblast activity and cell migration. AWF slightly stimulated fibroblast migration while CWF inhibited their activation and migration. The CXCR4- immunopositive population was continuously decreased compared to the control and AWF treatment. The expression of FAP was enhanced under AWF and medium. In keratinocytes CWF massively stimulated cell proliferation initiating on day six after injury. The presence of 10% CWF inhibited fibroblast activation and migration and induced the degradation of the collagen matrix. Keratinocytes were stimulated to proliferate, resulting in healing inhibiting hyperplasia. Transferred to human wounds, no effective wound closure would be achieved because of the de-regulation of pro-proliferative and migration-stimulating factors and a degraded extracellular matrix. This newly implemented 3D study model represents a novel appropriate in-vitro system for studying healing mechanisms and potential therapeutic applications.

Monitoring wound healing in a 3D wound model by hyperspectral imaging and efficient clustering.

Wound healing is a complex and dynamic process with different distinct and overlapping phases from homeostasis, inflammation and proliferation to remodelling. Monitoring the healing response of injured tissue is of high importance for basic research and clinical practice. In traditional application, biological markers characterize normal and abnormal wound healing. Understanding functional relationships of these biological processes is essential for developing new treatment strategies. However, most of the present techniques (in vitro or in vivo) include invasive microscopic or analytical tissue sampling. In the present study, a non-invasive alternative for monitoring processes during wound healing is introduced. Within this context, hyperspectral imaging (HSI) is an emerging and innovative non-invasive imaging technique with different opportunities in medical applications. HSI acquires the spectral reflectance of an object, depending on its biochemical and structural characteristics. An in-vitro 3-dimensional (3-D) wound model was established and incubated without and with acute and chronic wound fluid (AWF, CWF), respectively. Hyperspectral images of each individual specimen of this 3-D wound model were assessed at day 0/5/10 in vitro, and reflectance spectra were evaluated. For analysing the complex hyperspectral data, an efficient unsupervised approach for clustering massive hyperspectral data was designed, based on efficient hierarchical decomposition of spectral information according to archetypal data points. It represents, to the best of our knowledge, the first application of an advanced Data Mining approach in context of non-invasive analysis of wounds using hyperspectral imagery. By this, temporal and spatial pattern of hyperspectral clusters were determined within the tissue discs and among the different treatments. Results from non-invasive imaging were compared to the number of cells in the various clusters, assessed by Hematoxylin/Eosin (H/E) staining. It was possible to correlate cell quantity and spectral reflectance during wound closure in a 3-D wound model in vitro.

Aggregation of thrombin-derived C-terminal fragments as a previously undisclosed host defense mechanism

Effective control of endotoxins and bacteria is crucial for normal wound healing. During injury, the key enzyme thrombin is formed, leading to generation of fibrin. Here, we show that human neutrophil elastase cleaves thrombin, generating 11-kDa thrombin-derived C-terminal peptides (TCPs), which bind to and form amorphous amyloid-like aggregates with both bacterial lipopolysaccharide (LPS) and gram-negative bacteria. In silico molecular modeling using atomic resolution and coarse-grained simulations corroborates our experimental observations, altogether indicating increased aggregation through LPS-mediated intermolecular contacts between clusters of TCP molecules. Upon bacterial aggregation, recombinantly produced TCPs induce permeabilization of Escherichia coli and phagocytic uptake. TCPs of about 11 kDa are present in acute wound fluids as well as in fibrin sloughs from patients with infected wounds. We noted aggregation and colocalization of LPS with TCPs in such fibrin material, which indicates the presence of TCP-LPS aggregates under physiological conditions. Apart from identifying a function of proteolyzed thrombin and its fragments, our findings provide an interesting link between the coagulation system, innate immunity, LPS scavenging, and protein aggregation/amyloid formation.

Clinical efficacy of dressings for treatment of heavily exuding chronic wounds

The treatment of chronic ulcers is a complex issue and presents an increasing problem for caregivers everywhere. This is especially true in Germany, where more than 4 million chronic wounds are treated each year. Therapeutic decisions must be patient-centered and reflect wound etiology, localization, and healing status. The practice of using the same wound dressing during the entire healing period is no longer reasonable. Instead, multiple types of dressings may be needed for a single wound over its healing trajectory. Selection of the most appropriate dress- ing should be based on wound phase, depth, signs of infection, and level of exudate. Moisture balance is critical in wound care; dryness will hamper epithelial cell migration while excessive generation of fluid causes maceration at the wound margins. Hence, exudate management is a key issue in chronic wound therapy, particularly given that exudate from chronic wounds has a composition different from that of acute wound fluid. Several studies have shown that exudates from non-healing wounds contain significantly elevated levels of protease activity, increased formation of free radicals, and abundant amounts of proinflammatory cytokines, while concentra - tions of growth factors and protease inhibitors are markedly decreased. Application of dressings that remove and sequester excess amounts of wound fluid may not only help in restoring the correct balance of moisture, but also support the wound healing process by preventing tissue deterioration caused by abundant protease activity. Several types of dressings, such as hydrogels, hydrocolloids, alginates, hydrofibers, foams, and superabsorbent dressings, are reviewed here

The role of SDF-1 in homing of human adipose-derived stem cells.

One of the putative pathophysiological mechanisms of chronic wounds is a disturbed homing of stem cells. In this project, the stromal cell-derived factor 1 (SDF-1)/C-X-C chemokine receptor (CXCR) 4 and SDF-1/CXCR7 pathway were focused in human adipose-derived stem cells (ASCs). ASCs were incubated with acute (AWF) or chronic wound fluid (CWF) to analyze their effects by quantitative real-time polymerase chain reaction (SDF-1, CXCR4, CXCR7, TIMP3), enzyme-linked immunosorbent assay (SDF-1 in WFs and supernatant), and transwell migration assay with/without antagonization. Whereas SDF-1 amounted 73.5 pg/mL in AWF, it could not be detected in CWF. Incubation with AWF led to a significant enhancement (129.7 pg/mL vs. 95.5 pg/mL), whereas CWF resulted in a significant reduction (30 pg/mL vs. 95.5 pg/mL) of SDF-1 in ASC supernatant. The SDF-1 receptor CXCR7 was detected on ASCs. AWF but not CWF significantly induced ASC migration, which was inhibited by CXCR4 and CXCR7 antagonists. Expressions of SDF-1, CXCR4, and CXCR7 were significantly stimulated by AWF while TIMP3 expression was reduced. In conclusion, an uncontrolled inflammation in the chronic wound environment, indicated by a reduced SDF-1 expression, resulted in a decreased ASC migration. A disturbed SDF-1/CXCR4 as well as SDF-1/CXCR7 pathway seems to play an important role in the impaired healing of chronic wounds.

Hyperglycemia is associated with lower levels of urokinase-type plasminogen activator and urokinase-type plasminogen activator receptor in wound fluid

AimsWounds in patients with hyperglycemia show impaired healing. Plasminogen activation is crucial in several overlapping phases of wound healing process. In this study, we aimed i) to compare acute wound fluid in patients with hyperglycemia and normoglycemia, ii) to focus on the elements of plasminogen activation in the wound fluid, and iii) to determine if the acute wound fluid characteristics are associated with surgical site infections. MethodsIn a cohort of 54 patients, a closed suction drain was placed in the wound above the anterior abdominal wall fascia under the skin in order to collect postoperative acute wound fluid samples for 3 following days after colorectal surgery. Patients were classified as normoglycemic (n=25) or hyperglycemic (n=29; 17 with type 2 diabetes and 12 with stress induced hyperglycemia). Surgical site infection was defined according to the Centers for Disease Control criteria. The levels of urokinase-type plasminogen activator (uPA), urokinase-type plasminogen activator receptor (uPAr), plasminogen activator inhibitor-1 (PAI-1), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and fibroblast growth factor-1 (FGF-1) were measured in the wound fluid. ResultsCompared to normoglycemic subjects, patients with hyperglycemia had significantly lower levels of uPA and uPAr in the wound fluid despite similar or even higher circulating levels. There was no significant difference in IL-1β, TNF-α, PAI-1 and FGF-1 levels. In the whole study population, the wound fluid levels of uPA and uPAr were negatively correlated with circulating glucose levels. No difference was detected in the wound fluid characteristics of patients with and without surgical site infection. ConclusionPatients with hyperglycemia exhibit decreased levels of uPA and uPAr in the wound fluid, suggesting a local failure in plasminogen activation at the wound site.

Acute and chronic wound fluids influence keratinocyte function differently

Wound healing requires a proper functioning of keratinocytes that migrate, proliferate and lead to a competent wound closure. Impaired wound healing might be due to a disturbed keratinocyte function caused by the wound environment. Basically, chronic wound fluid (CWF) differs from acute wound fluid (AWF). The aim of this study was to analyse the effects of AWF and CWF on keratinocyte function. We therefore investigated keratinocyte migration and proliferation under the influence of AWF and CWF using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] test and scratch assay. We further measured the gene expression by qRT-PCR regarding growth factors and matrixmetalloproteinases (MMPs) involved in regeneration processes. AWF had a positive impact on keratinocyte proliferation over time, whereas CWF had an anti-proliferative effect. Keratinocyte migration was significantly impaired by CWF in contrast to an undisturbed wound closure under the influence of AWF. MMP-9 expression was strongly upregulated by CWF compared with AWF. Keratinocyte function was significantly impaired by CWF. An excessive induction of MMP-9 by CWF might lead to a permanent degradation of extracellular matrix and thereby prevent wounds from healing.

Biomolecular signatures of diabetic wound healing by structural mass spectrometry.

Wound fluid is a complex biological sample containing byproducts associated with the wound repair process. Contemporary techniques, such as immunoblotting and enzyme immunoassays, require extensive sample manipulation and do not permit the simultaneous analysis of multiple classes of biomolecular species. Structural mass spectrometry, implemented as ion mobility-mass spectrometry (IM-MS), comprises two sequential, gas-phase dispersion techniques well suited for the study of complex biological samples because of its ability to separate and simultaneously analyze multiple classes of biomolecules. As a model of diabetic wound healing, poly(vinyl alcohol) sponges were inserted subcutaneously into nondiabetic (control) and streptozotocin-induced diabetic rats to elicit a granulation tissue response and to collect acute wound fluid. Sponges were harvested at days 2 or 5 to capture different stages of the early wound-healing process. Utilizing IM-MS, statistical analysis, and targeted ultraperformance liquid chromatography analysis, biomolecular signatures of diabetic wound healing have been identified. The protein S100-A8 was highly enriched in the wound fluids collected from day 2 diabetic rats. Lysophosphatidylcholine (20:4) and cholic acid also contributed significantly to the differences between diabetic and control groups. This report provides a generalized workflow for wound fluid analysis demonstrated with a diabetic rat model.

Acute and chronic wound fluids inversely influence adipose‐derived stem cell function: molecular insights into impaired wound healing

Wound healing is a complex biological process that requires a well-orchestrated interaction of mediators as well as resident and infiltrating cells. In this context, mesenchymal stem cells play a crucial role as they are attracted to the wound site and influence tissue regeneration by various mechanisms. In chronic wounds, these processes are disturbed. In a comparative approach, adipose-derived stem cells (ASC) were treated with acute and chronic wound fluids (AWF and CWF, respectively). Proliferation and migration were investigated using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test and transwell migration assay. Gene expression changes were analysed using quantitative real time-polymerase chain reaction. AWF had a significantly stronger chemotactic impact on ASC than CWF (77·5% versus 59·8% migrated cells). While proliferation was stimulated by AWF up to 136·3%, CWF had a negative effect on proliferation over time (80·3%). Expression of b-FGF, vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 was strongly induced by CWF compared with a mild induction by AWF. These results give an insight into impaired ASC function in chronic wounds. The detected effect of CWF on proliferation and migration of ASC might be one reason for an insufficient healing process in chronic wounds.

Cytoskeletal protein Flightless (Flii) is elevated in chronic and acute human wounds and wound fluid: neutralizing its activity in chronic but not acute wound fluid improves cellular proliferation

Chronic non-healing wounds form a medical need which will expand as the population ages and the obesity epidemic grows. Whilst the complex mechanisms underlying wound repair are not fully understood, remodelling of the actin cytoskeleton plays a critical role. Elevated expression of the actin cytoskeletal protein Flightless I (Flii) is known to impair wound outcomes. To determine if Flii is involved in the impaired healing observed in chronic wounds, its expression in non-healing human wounds from patients with venous leg ulcers was determined and compared to its expression in acute wounds and unwounded skin. Increased expression of Flii was observed in both chronic and acute wounds with wound fluid and plasma also containing secreted Flii protein. Inflammation is a key aspect of wound repair and fluorescence-activated cell sorting (FACS) analysis revealed Flii was located in neutrophils within the blood and that it co-localised with CD16+ neutrophils in chronic wounds. The function of secreted Flii was investigated as both chronic wound fluid and Flii have previously been shown to inhibit fibroblast proliferation. To determine if the inhibitory effect of wound fluid was due in part to the presence of Flii, wound fluids were depleted of Flii using Flii-specific neutralizing antibodies (FnAb). Flii depleted chronic wound fluid no longer inhibited fibroblast proliferation, suggesting that Flii may contribute to the inhibitory effect of chronic wound fluid on fibroblast function. Application of FnAbs to chronic wounds may therefore be a novel approach used to improve the local environment of non-healing wounds and potentially improve healing outcomes.

Moisture in wound healing: exudate management

Wound exudate can have a significant impact on patient's quality of life and delay wound healing. It is also challenging for clinicians and can be costly in terms of clinical time and dressing cost. Understanding the difference between acute and chronic wound fluid is essential in order for clinicians to select the most appropriate treatment for their patients. Good patient assessment is the starting point for successful management and should include assessment of the patient, their wound and the type and amount of exudate. The management pathway should aim to address contributory factors, improve the patient's quality of life, optimise the wound bed and ensure the correct level of moisture at the wound bed. Dressings and topical negative pressure therapy are the main option for managing exudates and selection should be based on their clinical and cost effectiveness. A structured approach to exudate assessment and management as outlined in this article will help to reduce complications such delayed wound healing, prolonged treatment and patient suffering.

Cellular sources and inducers of cytokines present in acute wound fluid

Acute wounds contain many biological active molecules, including several cytokines and growth factors. However, the cellular sources of each molecule, as well as the stimuli inducing them, are poorly characterized. We quantified the levels of 27 cytokines, chemokines, and growth factors in acute wound fluid in a luminex-based assay. The acute wound fluid contained particularly high levels of IL-6 and IL-8, as well as elevated levels of MCP-1, IL-1RA, PDGF, IP-10, IFN-γ, and TNF-α. Surprisingly, the amounts of IL-1β and IL-10 were relatively low. To characterize the cellular sources of these molecules, we analyzed supernatants from monocytes, neutrophils, keratinocytes, fibroblasts, and endothelial cells stimulated with pro- and anti inflammatory cytokines, and different Toll-like receptor (TLR) ligands. The different cell types showed overlapping but distinct patterns of production of signal molecules, as well as sensitivity to ligands. Among pro-inflammatory cytokines, IL-1β was the most potent inducer of signal molecule production. Furthermore, keratinocytes and endothelial cells were in particular responsive to the Toll-like receptor-3 ligand poly I:C. New interactions between cytokines and growth factors were revealed, which may have important roles in wound healing, including IL-1β-induced IFN-γ and IL-10-induced VEGF.

Immunodepletion of high-abundant proteins from acute and chronic wound fluids to elucidate low-abundant regulators in wound healing

BackgroundThe process of wound healing consists of several well distinguishable and finely tuned phases. For most of these phases specific proteins have been characterized, although the underlying mechanisms of regulation are not yet fully understood. It is an open question as to whether deficits in wound healing can be traced back to chronic illnesses such as diabetes mellitus. Previous research efforts in this field focus largely on a restricted set of marker proteins due to the limitations detection by antibodies imposes. For mechanistic purposes the elucidation of differences in acute and chronic wounds can be addressed by a less restricted proteome study. Mass spectrometric (MS) methods, e.g. multi dimensional protein identification technology (MudPIT), are well suitable for this complex theme of interest. The human wound fluid proteome is extremely complex, as is human plasma. Therefore, high-abundant proteins often mask the mass spectrometric detection of lower-abundant ones, which makes a depletion step of such predominant proteins inevitable.FindingsIn this study a commercially available immunodepletion kit was evaluated for the detection of low-abundant proteins from wound fluids. The dynamic range of the entire workflow was significantly increased to 5-6 orders of magnitude, which makes low-abundant regulatory proteins involved in wound healing accessible for MS detection.ConclusionThe depletion of abundant proteins is absolutely necessary in order to analyze highly complex protein mixtures such as wound fluids using mass spectrometry. For this the used immunodepletion kit is a first but important step in order to represent the entire dynamic range of highly complex protein mixtures in the future.

Bioresponsive Dextrin−rhEGF Conjugates: In Vitro Evaluation in Models Relevant to Its Proposed Use as a Treatment for Chronic Wounds

We recently developed a bioresponsive dextrin-recombinant human epidermal growth factor (rhEGF) conjugate as a polymer therapeutic with potential for use in the promotion of tissue repair. The aim of these studies was to use patient-derived wound fluid and fibroblasts to evaluate its potential for further development as a treatment for chronic wounds, such as venous leg ulceration, a growing clinical challenge in the aging population. First, the levels of EGF (ELISA assay), alpha-amylase and elastase (enzyme assays) were measured in patient-derived acute and chronic wound fluid. EGF was detected in acute, but not in chronic wound fluid. alpha-Amylase concentrations were higher in acute (188 IU/L), compared to chronic wound fluid (52 IU/L), but both were in the range of human serum levels. Although elastase was present in chronic wound fluid (2.1 +/- 1.2 RFU/min), none was detected in acute wound fluid. Dextrin-rhEGF incubation in chronic wound fluid led to endogenous alpha-amylase-mediated release of rhEGF (ELISA) that was maximal at 48 h. When the migration of HaCaT keratinocytes and of human fibroblasts (isolated from patient-matched, normal skin and chronic dermal wounds) was studied in vitro using the scratch wound assay, enhanced cell migration was observed in response to both free rhEGF and alpha-amylase-activated dextrin-rhEGF conjugate compared to controls. In addition, fibroblasts displayed increased proliferation (normal dermal fibroblasts approximately 160%; chronic wound fibroblasts approximately 140%) following incubation (72 h) with dextrin-rhEGF that had been exposed to physiological levels of alpha-amylase (93 IU/L). These results suggest further preclinical in vivo evaluation of dextrin-rhEGF is warranted to determine whether conjugate pharmacokinetics and rhEGF liberation into such a complex and aggressive environment can still lead to bioactivity.

Protease and pro-inflammatory cytokine concentrations are elevated in chronic compared to acute wounds and can be modulated by collagen type I in vitro

Physiological wound repair is a highly regulated, complex process, which leads to formation of new tissue after injury. However, the healing process is not perfect and healing impairments can occur. Delayed healing and formation of chronic wounds has been linked to the excessive production of proteolytic enzymes leading to reduced amounts of growth factors and successive destruction of the extracellular matrix. It has been implied that there is an alteration in the normal control mechanisms regulating the levels of these enzymes. The study presented provides data on the concentration of proteases and cytokines in wound fluid from chronic when compared with acute wounds. Levels of proteases such as PMN elastase, matrix metalloproteinases-2 (MMP-2), and MMP-13 were found to be profoundly elevated in chronic when compared with acute wound fluids. In addition, concentrations of IL-1beta, IL-6, and IL-8 were shown to be significantly higher in chronic than in acute wounds. Furthermore, the ability of a wound dressing, consisting of bovine collagen type I, to bind pro-inflammatory cytokines was investigated. Collagen type I was able to bind significant amounts of the pro-inflammatory cytokines in vitro. Thus, it should be able to establish a more physiological wound milieu in vivo and promote healing.

166 The Role of Serine Proteases and their Inhibitors in Chronic Wounds

The role of proteases in chronic wounds has been the subject of many investigations in recent years. These studies have reported biochemical differences between chronic and acute wound fluids and have shown that elevated levels of proteases, in particular the matrix metalloproteinases are abundant in chronic wounds. While this has led to the hypothesis that the chronic wound environment is hostile and not conducive to wound repair, it is still unknown whether this is due to a direct or indirect defect in protease regulation or their inhibitors. We hypothesize that an excess of proteases, specifically the serine proteases present in chronic wounds, are primarily responsible for this hostile wound environment. These proteases degrade endogenous growth factors, reducing their efficacy and delaying healing. In this study, fluid and tissue from chronic and acute wounds were collected over a 24-hour period. Using ELISA, samples were assessed for protease activity (specifically elastase and typsin-like enzymes), their inhibitors and growth factors. Our results show that serine proteases, predominantly elastase, were significantly elevated in the chronic wound fluids. The serpins designed to control these proteases were not up-regulated when compared to the acute controls, resulting in excessive proteolytic activity. An increase in serine protease production without an increase in their serpins is thought to result in a reduction in growth factors, an effect, which was also observed in the chronic wound samples. This work indicates that there is an imbalance in the ratio of inhibitor to enzyme, due to an up regulation of protease production in chronic wounds. We also conclude that misregulation of serine proteases may be responsible for the observed excessive degradation of the extracellular matrix and growth factors in these chronic wounds.

073 Effect of Advanced Wound Therapies on Fibroblast Proliferation in Acute Wound Fluid

Wound repair is described as a delicately balanced and well-orchestrated progression of events, which ultimately results in healing in the majority of acute cases. However, time taken to complete healing can vary greatly between patients and any alteration in this physiological process could delay healing further. Thus, a wound treatment, which facilitates healing independent of wound type and in patients where healing is compromised or impeded, would be extremely advantageous. Previous studies suggest a beneficial role for biomaterials such as collagen/ORC in modifying the chronic wound environment; however, their effect on the acute wound environment is unknown. While it is generally accepted that acute wounds heal at an optimum rate due to a positive wound environment, we wanted to determine if current advanced wound healing treatments could augment or impact this healing rate. In this study we evaluated the effect of advanced wound therapies in the presence of acute wound fluid on human dermal fibroblast proliferation. We hypothesize that an enhanced effect on fibroblast proliferation in the presence of acute wound fluid may be indicative of a beneficial effect in the treatment of acute wounds. Results demonstrate that of the wound treatments tested only collagen/ORC containing therapies exhibited a positive effect on fibroblast proliferation in the presence of acute wound fluid. We conclude, therefore, that collagen/ORC biomaterials, already shown to be beneficial in the treatment of chronic wounds, may also be a valuable therapy in the treatment of acute wounds.