Functional extracellular matrix hydrogel modified with MSC‐derived small extracellular vesicles for chronic wound healing

ObjectivesDiabetic wound healing remains a global challenge in the clinic and in research. However, the current medical dressings are difficult to meet the demands. The primary goal of this study was to fabricate a functional hydrogel wound dressing that can provide an appropriate microenvironment and supplementation with growth factors to promote skin regeneration and functional restoration in diabetic wounds.Materials and MethodsSmall extracellular vesicles (sEVs) were bound to the porcine small intestinal submucosa‐based hydrogel material through peptides (SC‐Ps‐sEVs) to increase the content and achieve a sustained release. NIH3T3 cell was used to evaluate the biocompatibility and the promoting proliferation, migration and adhesion abilities of the SC‐Ps‐sEVs. EA.hy926 cell was used to evaluate the stimulating angiogenesis of SC‐Ps‐sEVs. The diabetic wound model was used to investigate the function/role of SC‐Ps‐sEVs hydrogel in promoting wound healing.ResultsA functional hydrogel wound dressing with good mechanical properties, excellent biocompatibility and superior stimulating angiogenesis capacity was designed and facilely fabricated, which could effectively enable full‐thickness skin wounds healing in diabetic rat model.ConclusionsThis work led to the development of SIS, which shows an unprecedented combination of mechanical, biological and wound healing properties. This functional hydrogel wound dressing may find broad utility in the field of regenerative medicine and may be similarly useful in the treatment of wounds in epithelial tissues, such as the intestine, lung and liver.

Schematic illustration showing synthesis of the SC‐Ps scaffold dressing and nanoscale sEVs loaded SC‐Ps scaffold dressing and the potential application of the dressings in diabetic wound healing and skin reconstruction.     

An alginate hydrogel matrix for the localised delivery of a fibroblast/keratinocyte co-culture

There is significant interest in the development of tissue-engineered skin analogues, which replace both the dermal and the epidermal layer, without the use of animal or human derived products such as collagen or de-epidermalised dermis. In this study, we proposed that alginate hydrogel could be used to encapsulate fibroblasts and that keratinocytes could be cultured on the surface to form a bilayered structure, which could be used to deliver the co-culture to a wound bed, initially providing wound closure and eventually expediting the healing process. Encapsulation of fibroblasts in 2 and 5% w/v alginate hydrogel effectively inhibited their proliferation, whilst maintaining cell viability allowing keratinocytes to grow uninhibited by fibroblast overgrowth to produce a stratified epidermal layer. It was shown that the alginate degradation process was not influenced by the presence of fibroblasts within the hydrogel and that lowering the alginate concentration from 5 to 2% w/v increased the rate of degradation. Fibroblasts released from the scaffold were able to secrete extracellular matrix (ECM) and thus should replace the degrading scaffold with normal ECM following application to the wound site. These findings demonstrate that alginate hydrogel may be an effective delivery vehicle and scaffold for the healing of full-thickness skin wounds.     

The Novelty in Fabrication of Poly Vinyl Alcohol/κ-Carrageenan Hydrogel with <Emphasis Type="Italic">Lactobacillus bulgaricus</Emphasis> Extract as Anti-inflammatory Wound Dressing Agent

Material barrier properties to microbes are an important issue in many pharmaceutical applications like wound dressings. A wide range of biomaterials has been used to manage the chronic inflamed wounds. Eight hydrogel membranes of poly vinyl alcohol (PVA) with κ-carrageenan (KC) and Lactobacillus bulgaricus extract (LAB) have been prepared by using freeze–thawing technique. To evaluate the membranes efficiency as wound dressing agents, various tests have been done like gel fraction, swelling behavior, mechanical properties, etc. The antibacterial activities of the prepared membranes were tested against the antibiotic-resistant bacterial isolates. In addition, the safety usage of the prepared hydrogel was checked on human dermal fibroblast cells. The anti-inflammatory properties of the prepared hydrogel on LPS-PBMC cell inflammatory model were quantified using enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-qPCR). The analysis data of TGA, SEM, gel fraction, and swelling behavior showed changes in properties of prepared PVA\KC\LAB hydrogel membrane than pure PVA hydrogel membrane. The antibacterial activities of the prepared membranes augmented in LAB extract-prepared membranes. Out of the eight used hydrogel membranes, the PVAKC4 hydrogel membrane is the safest one on fibroblast cellular proliferation with a maximum proliferation percentage 97.3%. Also, all the used hydrogel membrane showed abilities to reduce the concentration of IL-2 and IL-8 compared with both negative and positive control. In addition, almost all the prepared hydrogel membrane showed variable abilities to downregulate the expression of TNF-α gene with superior effect of hydrogel membrane KC1. PVA/KC/LAB extract hydrogel membrane may be a promising material for wound dressing application and could accelerate the healing process of the chronic wound because of its antimicrobial and anti-inflammatory properties.     

Clinical trials of amniotic membranes in burn wound care

Four test conditions of increasing complexity were used to evaluate the clinical efficacy of amniotic membranes as biologic dressings on donor sites and burn wounds in children. These were the clean-skin donor-site wound, the uncontaminated shallow partial-thickness burn wound, the bed of freshly excised full-thickness wounds, and the granulating surface of colonized burn wounds. The rate of epithelialization under amniotic membranes was the same as that under 5% scarlet red ointment or 0.5% silver nitrate solution dressings. Preservation of a healthy excised wound bed and maintenance of a low bacterial count in contaminated wounds paralleled the experience with human allograft dressings despite technical difficulties and the absence of vascularization of amniotic membrane and its fragile structure. Tentative conclusions are drawn as to the mechanisms by which biologic dressings exert their beneficial effects.     

Plasma treatments of dressings for wound healing: a review

This review covers the use of plasma technology relevant to the preparation of dressings for wound healing. The current state of knowledge of plasma treatments that have potential to provide enhanced functional surfaces for rapid and effective healing is summarized. Dressings that are specialized to the needs of individual cases of chronic wounds such as diabetic ulcers are a special focus. A summary of the biology of wound healing and a discussion of the various types of plasmas that are suitable for the customizing of wound dressings are given. Plasma treatment allows the surface energy and air permeability of the dressing to be controlled, to ensure optimum interaction with the wound. Plasmas also provide control over the surface chemistry and in cases where the plasma creates energetic ion bombardment, activation with long-lived radicals that can bind therapeutic molecules covalently to the surface of the dressing. Therapeutic innovations enabled by plasma treatment include the attachment of microRNA or antimicrobial peptides. Bioactive molecules that promote subsequent cell adhesion and proliferation can also be bound, leading to the recruitment of cells to the dressing that may be stem cells or patient-derived cells. The presence of a communicating cell population expressing factors promotes healing.     

静电纺丝用作难愈合伤口敷料的研究进展

静电纺丝伤口敷料作为一种新型功能性敷料,具有较大的比表面积、可调控的孔隙率和良好的生物性能,既有益于细胞呼吸,又 可抑制细菌感染伤口,并能促进细胞增殖和加速创面愈合,是未来伤口敷料研发领域发展的新方向。介绍静电纺丝纳米纤维的原理、特点, 重点阐述各类聚合物、生物活性物质在静电纺丝伤口敷料制备中的应用进展。     

Full-thickness human foreskin transplantation onto nude rats as an in vivo model of acute human wound healing

Current wound-healing models do not fully duplicate the in vivo human environment. The feasibility of grafting human full-thickness foreskin onto nude rats, as a model of acute wound healing, was evaluated. Incisions were then created on the grafted skin, and wound healing was evaluated. Full-thickness human skin was obtained after elective circumcision and was grafted subcutaneously onto the dorsal thorax of nude rats. At 10 days after transplantation, graft beds were judged for graft viability, on the basis of gross appearance, texture, and adherence. Full-thickness wounds were then made in the foreskin. Graft wounds were left to close by secondary intention. The wounds were allowed to heal for 7 days. Wounds were excised and tested for breaking stress. Histological evaluations included proliferating cell nuclear antigen, factor VIII, hematoxylin and eosin, and trichrome staining. Twenty grafts were performed, with 100 percent viability. Upon incision, all grafts bled freely, indicating a rich vascular supply and tissue viability. Graft viability was confirmed by the presence of proliferating cells in the parabasal stratum of the epithelium. Furthermore, there was evidence of angiogenesis, as confirmed by staining for factor VIII. Breaking stress was evaluated by tensiometry, 7 days after wounding. Histological evaluations revealed viable grafts and active wound-healing events. Full-thickness human skin can be successfully transplanted onto nude rats, providing a larger, more physiological model of human wound healing. This model closely parallels the in vivo situation, providing a promising model for study of the complex biological processes of acute human wound healing, in a reproducible manner.     

Electrospun zwitterionic poly(sulfobetaine methacrylate) for nonadherent, superabsorbent, and antimicrobial wound dressing applications

Zwitterionic poly(sulfobetaine methacrylate) (PSBMA) has been well studied for its superhydrophilic and ultralow biofouling properties, making it a promising material for superabsorbent and nonadherent wound dressings. Electrospinning provides multiple desirable features for wound dressings, including high absorptivity due to high surface-area-to-volume ratio, high gas permeation, and conformability to contour of the wound bed. The goal of this work is to develop a fibrous membrane of PSBMA via electrospinning and evaluate its properties related to wound dressing applications. Being superhydrophilic, PSBMA fibers fabricated by a conventional electrospinning method would readily dissolve in water, whereas if cross-linker is added, the formation of hydrogel would prevent electrospinning. A three-step polymerization-electrospinning-photo-cross-linking process was developed in this work to fabricate the cross-linked electrospun PSBMA fibrous membrane. Such electrospun membrane was stable in water and exhibited high water absorption of 353% (w/w), whereas the PSBMA hydrogel only absorbed 81% water. The electrospun membrane showed strong resistance to protein adsorption and cell attachment. Bacterial adhesion studies using Gram negative P. aeruginosa and Gram positive S. epidermidis showed that the PSBMA electrospun membrane was also highly resistant to bacterial adhesion. The Ag(+)-impregnated electrospun PSBMA membrane was shown microbicidal, against both S. epidermidis and P. aeruginosa. Such electrospun PSBMA membrane is ideal for a novel type of nonadherent, superabsorbent, and antimicrobial wound dressing. The superior water absorption aids in fluid removal from highly exudating wounds while keeping the wound hydrated to support healing. Because of the resistance to protein, cell, and bacterial adhesion, the dressing removal will neither cause patients' pain nor disturb the newly formed tissues. The dressing also prevents the attachment of environmental bacteria and offers broad-spectrum antimicrobial activity. It is the first work to develop the water-stable electrospun PSBMA membrane, which has great potential for wound dressing and other applications.     

Wound dressings for a proteolytic-rich environment

Wound dressings have experienced continuous and significant changes over the years based on the knowledge of the biochemical events associated with chronic wounds. The development goes from natural materials used to just cover and conceal the wound to interactive materials that can facilitate the healing process, addressing specific issues in non-healing wounds. These new types of dressings often relate with the proteolytic wound environment and the bacteria load to enhance the healing. Recently, the wound dressing research is focusing on the replacement of synthetic polymers by natural protein materials to delivery bioactive agents to the wounds. This article provides an overview on the novel protein-based wound dressings such as silk fibroin keratin and elastin. The improved properties of these dressings, like the release of antibiotics and growth factors, are discussed. The different types of wounds and the effective parameters of healing process will be reviewed.     

Effect of a Synthetic Dressing Formed on a Burn Wound in Rats: a Comparison of Allografts, Collagen Sheets, and Polyhydroxyethylmethacrylate in the Control of Wound Infection

Allograft dressings to control Pseudomonas wound infections in rats were studied on surgical wounds and escharectomized burn wounds. The effects of allografts were compared with a collagen sheet (Aviderm) and a synthetic dressing, polyhydroxyethylmethacrylate (Hydron), formed on the wound by mixing the polymer and the solvent. The results indicated that infections in surgical wounds were more easily controlled by dressings than similar contaminations in burn wounds. A procedure was described for the formation of a synthetic dressing directly on the wound from a mixture of polymer and solvent. This type of preparation completely filled the wound area and sealed the edges, preventing further contamination, and gave excellent coverage of the wound. With 24 h of coverage of escharectomized burn wounds, allografts provided the best dressing for reduction of wound organisms. At 96 h of coverage, Hydron and Aviderm produce significant reductions in the Pseudomonas resident in the burn wound. The results support the thesis that suitable dressings promote local host defense processes which kill the contaminating bacteria.     

High-efficient and synergetic antibacterial nanocomposite hydrogel with quaternized chitosan/Ag nanoparticles prepared by one-pot UV photochemical synthesis

Hydrogel dressings have significant advantages such as absorption of tissue exudate, maintenance of proper moist environment, and promotion of cell proliferation. However, facile preparation method and high-efficient antibacterial hydrogel dressings are still a great challenge. In this study, a facile approach to prepare antibacterial nanocomposite hydrogel dressing to accelerate healing was explored. The hydrogels consisted of quaternized chitosan and chemically cross-linked polyacrylamide, as well as silver nanoparticles (AgNPs) stabilized by chitosan. The synthesis of the hydrogels including the formation of AgNPs and polymerization of acrylamide was accomplished simultaneously under UV irradiation in 1 hour without adding initiator. The hydrogels showed favorable tensile strength of ∼100 kPa with elongation at break over 1000% and shear modulus of ∼10⁴ Pa as well as suitable swelling ratio, which were appropriate for wound dressing. The combination of quaternized chitosan and AgNPs exhibited high-efficient and synergetic antibacterial performance with low cytotoxicity. In vivo animal experiments showed that the hydrogel can effectively prevent wound infection and promote wound healing. This study provides a facile method to produce antibacterial hydrogel wound dressing materials.     

Recombinant Lucilia sericata chymotrypsin in a topical hydrogel formulation degrades human wound eschar ex vivo

Larval biotherapy is a debridement tool used in wound management. The mechanism of action involves degradation of eschar by serine proteases including chymotrypsin within the alimentary fluids of first instar Lucilia sericata. With the rationale of obviating some limitations of biotherapy, including cost, complexity of use, and patient reticence, the present study describes a mobile hydrogel formulation containing freeze-dried recombinant L. sericata chymotrypsin designed for topical application. Neither freeze-drying nor formulation into the hydrogel significantly attenuated the measured activity of released enzyme compared to fresh-frozen enzyme in aqueous solution. Gel electrophoresis confirmed qualitatively that the chymotrypsin/hydrogel formulation both with and without supplementary urea at 10% (w) /(v) degraded human chronic wound eschar ex vivo. Mindful that the hallmark of intractability of chronic wounds is aberrant biochemistry, the pH activity profile for the enzyme/hydrogel formulation was compared with exudate pH in chronic wounds of mixed aetiology in a cohort of 48 hospital in-patients. Five patients' wounds were acidic, however, the remainder were predominantly alkaline and coincided with the pH optimum for the insect enzyme. Thus, a recombinant L. sericata chymotrypsin and hydrogel formulation could represent a pragmatic alternative to larval therapy for the management of chronic wounds.     

Control of Surface Wound Infection: Skin Versus Synthetic Grafts

Auto-, iso-, or xenografts of skin and synthetics placed on surface wounds freshly contaminated with Pseudomonas aeruginosa stabilizes the wound bacterial population in rats over a 24-h period. When these wounds contained a bacterial contamination established for 24 h prior to grafting, only skin and the synthetic polyhydroxyethylmethacrylate were effective in lowering the initial bacterial concentration. Polyurethane foam and nylon velour were not effective in the established infection model. Skin placed on a contaminated wound for 2 h or longer appeared to equilibrate with the underlying muscle so that the bacterial count per milligram of skin was similar to that of the muscle. It was suggested that this preparation would be useful to obtain an estimate of surface contamination without biopsy of the infected muscle. Skin grafts in place for 2 h significantly lowered the bacterial count in a wound with an established infection. A second decrease occurred between 4 and 24 h after grafting. Histological studies of contaminated and exposed panniculus muscle showed that leukocytes tend to migrate from the muscle surface to its base. Skin grafts and polyhydroxyethylmethacrylate appear to reverse the white cell migration so that the cells move toward the surface of the muscle with preservation of normal staining characteristics in the muscle. It is suggested that this alteration in cell movement after graft application might modify the white cell function and result in a greater bactericidal activity. Apparently, grafts lower bacterial levels in an established infection by modifying the host response to the surface contamination.     

Enzyme‐assisted formation of hybrid biopolymer hydrogels incorporating active phenolic nanospheres

Advances in development of nanocomposite gels that provide localized delivery of pharmaceuticals for treatment of chronic wounds are being highly pursued. To design such materials, the use of natural polymers is recommendable due to their intrinsic biocompatibility and biodegradability. Moreover, the use of biocatalytic approaches for composite assembling is preferred compared to harsh chemical cross‐linking reagents. In this study, HRP catalyzed cross‐linking of hydrogels from aqueous solution of thiolated chitosan to in situ incorporated sonochemically synthesized epigallocatechin gallate nanospheres (EGCG NSs). The potential of the generated NSs for chronic wound treatment was evaluated by assessing their antibacterial properties and inhibitory effect on myeloperoxidase and collagenase—major enzymes of inflamed chronic wounds. The EGCG NSs displayed better antibacterial and antienzymatic properties compared to the EGCG in solution. Also, the NSs were incorporated into hydrogels without affecting their integrity and were released intact in a sustained manner (during 6 days). The cytotoxicity assay confirmed the compatibility of the hybrid material with human fibroblasts that suffered less than 10% decrease in viability during 24 h. Release of functional phenolic NSs and good compatibility of the composite hydrogel with cells suggested its potential application in chronic wound management.     

The lactate conundrum in wound healing: Clinical and experimental findings indicate the requirement for a rapid point-of-care diagnostic

The increasing prevalence of chronic wounds has significant financial implications for nations with advanced healthcare provision. Although the diseases that predispose to hard‐to‐heal wounds are recognized, their etiology is less well understood, partly because practitioners in wound management lack specialized diagnostic support. Prognostic indicators for healing may be inherent to wound biochemistry but remain invisible under routine clinical investigation; lactate is an example of this. In this study, lactate concentration in exudate obtained from 20 patients undergoing wound management in hospital was variable but in some cases approached or exceeded 20 mM. In vitro viability studies indicated that fibroblasts and endothelial cells tolerated low levels of lactate (1–10 mM), but cell viability was severely compromised by high lactate concentrations (=20 mM). Scratched monolayer experiments revealed that cell migration was affected earlier than viability in response to increasing lactate dose, and this was shown by immunocytochemistry to be associated with cytoskeletal disruption. A prototype enzyme‐based colorimetric assay for lactate generating a color change that was rapid in the context of clinical practise, and capable of functioning within a gel vehicle, was developed with point‐of‐care dipstick applications in mind. A randomized single‐blinded trial involving 30 volunteers and using a color chart to calibrate the assay demonstrated that lactate concentration could be reliably estimated with 5 mM precision; this suggesting that “physiological” and “pathological” lactate concentration could be distinguished. The present data suggest that a dipstick‐type colorimetric assay could comprise a viable diagnostic tool for identifying patients at‐risk from high‐wound lactate. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 28: 917–924, 2012     

Accelerated healing of full-thickness skin wounds in a wet environment

Full-thickness skin wounds are preferably allowed to heal under controlled hydration dressings such as hydrocolloids. It was hypothesized that a wet (liquid) environment rather than a dry or moist one would accelerate the wound healing process. We compared skin repair by secondary intention in full-thickness skin wounds in wet (saline), moist (hydrocolloid), and dry (gauze) conditions in an established porcine wound healing model. The study included three animals with a total of 70 wounds layered in a standardized fashion on the back of young Yorkshire pigs. Twelve days after wounding, 0 percent of dry, 20 percent of moist, and 86 percent of saline-treated wounds were completely reepithelialized (p values = 0.0046 and 0.027 for saline wounds compared with dry and moist wounds, respectively). The accelerated healing was caused at least in part by faster contraction in wet wounds (p value < 0.005 compared with that of other groups 9 and 12 days after wounding). Development of granulation tissue was faster in moist conditions than it was for dry and wet wounds. The thickness and number of cell layers of the newly formed epidermis were greater in dry and wet wounds than in moist ones. It was concluded that these full-thickness porcine skin wounds healed faster in a wet environment than in a moist one. Dry wounds healed more slowly than moist wounds. The basic mechanisms of skin wound repair were influenced by the treatment modality as demonstrated by the observed differences in granulation tissue formation, reepithelialization, and rate of wound contraction.     

An in situ collagen-HA hydrogel system promotes survival and preserves the proangiogenic secretion of hiPSC-derived vascular smooth muscle cells

Human-induced pluripotent stem cell-derived vascular smooth muscle cells (hiPSC-VSMCs) with proangiogenic properties have huge therapeutic potential. While hiPSC-VSMCs have already been utilized for wound healing using a biomimetic collagen scaffold, an in situ forming hydrogel mimicking the native environment of skin offers the promise of hiPSC-VSMC mediated repair and regeneration. Herein, the impact of a collagen type-I-hyaluronic acid (HA) in situ hydrogel cross-linked using a polyethylene glycol-based cross-linker on hiPSC-VSMCs viability and proangiogenic paracrine secretion was investigated. Our study demonstrated increases in cell viability, maintenance of phenotype and proangiogenic growth factor secretion, and proangiogenic activity in response to the conditioned medium. The optimally cross-linked and functionalized collagen type-I/HA hydrogel system developed in this study shows promise as an in situ hiPSC-VSMC carrier system for wound regeneration.     

Why do skin grafts fail?

Fibrin is shown to be the agent responsible for the adherence of biological dressings and of autografts to wounds. Its presence is associated with graft success, and its absence with graft failure. The results suggest that the deposition of fibrin provides the basis for the anti-bacterial actions of biological dressings and for the sterilization of the wound under adherent autografts. The total number of bacteria per gram of tissue in the wound, though important, is not critical to the result of skin grafting. The mechanism by which different organisms cause grafts to fail is by the production of plasmin and proteolytic enzymes which dissolve the important fibrin scaffold--thus ensuring their own survival. Thus, it is the levels of these (and the numbers of organisms efficient in producing them) which cause success or failure of applied skin grafts.     

Hydrolytically degradable poly(ethylene glycol) hydrogel scaffolds as a cell delivery vehicle: Characterization of PC12 cell response

The central nervous system (CNS) has a low intrinsic potential for regeneration following injury and disease, yet neural stem/progenitor cell (NPC) transplants show promise to provide a dynamic therapeutic in this complex tissue environment. Moreover, biomaterial scaffolds may improve the success of NPC‐based therapeutics by promoting cell viability and guiding cell response. We hypothesized that a hydrogel scaffold could provide a temporary neurogenic environment that supports cell survival during encapsulation, and degrades completely in a temporally controlled manner to allow progression of dynamic cellular processes such as neurite extension. We utilized PC12 cells as a model cell line with an inducible neuronal phenotype to define key properties of hydrolytically degradable poly(ethylene glycol) hydrogel scaffolds that impact cell viability and differentiation following release from the degraded hydrogel. Adhesive peptide ligands (RGDS, IKVAV, or YIGSR), were required to maintain cell viability during encapsulation; as compared to YIGSR, the RGDS, and IKVAV ligands were associated with a higher percentage of PC12 cells that differentiated to the neuronal phenotype following release from the hydrogel. Moreover, among the hydrogel properties examined (e.g., ligand type, concentration), total polymer density within the hydrogel had the most prominent effect on cell viability, with densities above 15% w/v leading to decreased cell viability likely due to a higher shear modulus. Thus, by identifying key properties of degradable hydrogels that affect cell viability and differentiation following release from the hydrogel, we lay the foundation for application of this system towards future applications of the scaffold as a neural cell delivery vehicle. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1255–1264, 2013     

A prospective, blinded, randomized, controlled clinical trial of topical negative pressure use in skin grafting

Topical negative pressure has been demonstrated to improve graft take in a number of noncomparative studies. This study aimed to assess whether split-thickness skin graft take is improved qualitatively or quantitatively with topical negative pressure therapy compared with standard bolster dressings. A blinded, prospective, randomized trial was conducted of 22 adult inpatients of Liverpool Hospital between July of 2001 and July of 2002 who had wounds requiring skin grafting. After grafting, each wound half was randomized to receive either a standard bolster dressing or a topical negative pressure dressing. Skin graft assessment was performed at 2 weeks by a single observer blinded to the randomization. Two patients were lost to follow-up and were excluded from the study. There were 20 patients (12 men and eightwomen) in the study group. The median patient age was 64 years (range, 27 to 88 years), and the mean wound size was 128 cm2 (range, 35 to 450 cm2). The wound exposed subcutaneous fat in eight patients, muscle in six patients, paratenon in four patients, and deep fascia in two patients. At 2 weeks, wounds that received a topical negative pressure dressing had a greater degree of epithelialization in six cases (30 percent), the same degree of epithelialization in nine cases (45 percent), and less epithelialization in five cases (25 percent) compared with their respective control wounds. Graft quality following topical negative pressure therapy was subjectively determined to be better in 10 cases (50 percent), equivalent in seven cases (35 percent), and worse in three cases (15 percent). Although the quantitative graft take was not significant, the qualitative graft take was found to be significantly better with the use of topical negative pressure therapy (p < 0.05). Topical negative pressure significantly improved the qualitative appearance of split-thickness skin grafts as compared with standard bolster dressings.