Deep Partial-thickness Wounds Research Articles

Functional genomics unique to week 20 post wounding in the deep cone/fat dome of the Duroc/Yorkshire porcine model of fibroproliferative scarring.

BackgroundHypertrophic scar was first described over 100 years ago; PubMed has more than 1,000 references on the topic. Nevertheless prevention and treatment remains poor, because 1) there has been no validated animal model; 2) human scar tissue, which is impossible to obtain in a controlled manner, has been the only source for study; 3) tissues typically have been homogenized, mixing cell populations; and 4) gene-by-gene studies are incomplete.Methodology/Principal FindingsWe have assembled a system that overcomes these barriers and permits the study of genome-wide gene expression in microanatomical locations, in shallow and deep partial-thickness wounds, and pigmented and non-pigmented skin, using the Duroc(pigmented fibroproliferative)/Yorkshire(non-pigmented non-fibroproliferative) porcine model. We used this system to obtain the differential transcriptome at 1, 2, 3, 12 and 20 weeks post wounding. It is not clear when fibroproliferation begins, but it is fully developed in humans and the Duroc breed at 20 weeks. Therefore we obtained the derivative functional genomics unique to 20 weeks post wounding. We also obtained long-term, forty-six week follow-up with the model.Conclusions/Significance1) The scars are still thick at forty-six weeks post wounding further validating the model. 2) The differential transcriptome provides new insights into the fibroproliferative process as several genes thought fundamental to fibroproliferation are absent and others differentially expressed are newly implicated. 3) The findings in the derivative functional genomics support old concepts, which further validates the model, and suggests new avenues for reductionist exploration. In the future, these findings will be searched for directed networks likely involved in cutaneous fibroproliferation. These clues may lead to a better understanding of the systems biology of cutaneous fibroproliferation, and ultimately prevention and treatment of hypertrophic scarring.

Effect of skin autograft with different thickness on the transdifferentiation of fibroblasts after deep partial thickness burn in rats

To investigate the effect of thin split-thickness skin, inter-mediate thickness skin and full-thickness skin autograft on the differentiation of fibroblasts into myofibroblasts in rats after deep partial thickness burn. A total of 40 SD rats were divided randomly into two groups (Group A & Group B, n = 20 each). In Group A, tissue samples were collected at Day 2 after skin-grafting while Day 7 in Group B. In each group, every rat was scalded to cause deep partial thickness wound with an area of 10% of total body surface. The wounds received eschar shaving instantly coupled with skin-autograft, covering with thin split-thickness skin, inter-mediate thickness skin and full-thickness skin respectively. Meanwhile the control wound on the same rat was scalded only. Then the expression of α-SMA was detected by immunohistochemistry in each wound. And the numbers of myofibroblasts (α-SMA positive cells) and fibroblasts (negative cells) were counted to calculate the conversion ratio of myofibroblasts. In Group A, the conversion ratios of myofibroblasts of control, thin split-thickness skin autograft, inter-mediate thickness skin and full-thickness skin groups were (76.3 ± 3.3)%, (69.8 ± 1.6)%, (57.5 ± 1.6)% and (44.7 ± 1.7)% respectively. In Group B, the ratios were (72.9 ± 6.1)%, (63.6 ± 4.7)%, (50.2 ± 1.6)% and (32.3 ± 1.2)% respectively. The ratio was higher in control group than that in any other one (P < 0.01). There was statistic difference between thin split-thickness skin, inter-mediate thickness skin and full-thickness skin autograft groups (P < 0.05). A direct association may exist between the conversion ratio of myofibroblasts and the application of skin-grafting in rats after deep partial thickness scalding. It is probably related with varying degrees of scar contracture in the long-term.

Method for Autologous Single Skin Cell Isolation for Regenerative Cell Spray Transplantation with Non-Cultured Cells

There is a therapeutic gap for patients with deep partial thickness wounds (Grade IIb) of moderate size that were initially not treated with split- or mesh grafting to avoid overgrafting, but developed delayed wound healing around two weeks after injury--at which time grafting is typically not indicated anymore. Delayed wound healing is often associated with esthetically unsatisfactory results and sometimes functional problems. An innovative cell isolation method for cell spray transplantation at the point of care, which eliminates cell culture prior to treatment, was implemented for this population of burn patients in our center. Autologous skin cell spray transplantation was initiated by taking healthy skin. The dermal/epidermal layers were separated using enzymatic digestion with 40 min dispase application, followed by 15 min trypsin application for basal kerationcyte isolation, 7 min cell washing by centrifugation, followed by transferring the cells for spraying into Ringer lactate solution. The procedure was performed on site in a single session immediately following the biopsy. After sharp wound debridement, cells were immediately transplanted by deposition with a cell sprayer for even distribution of the cell suspension. Eight patients were treated (mean age 30.3 years, mean burn total body surface area 14%, mean Abbreviated Burn Severity Index (5 points). The mean time to complete re-epithelialization was 12.6 days. All patients exhibited wound healing with improved esthetic and functional quality. Our initial experience for the use of non-cultured cells using a two-enzyme approach with cell washing suggests shortened time for wound closure, suggesting that the method may potentially avoid longer-term complications.

Laser‐mediated fixation of collagen‐based scaffolds to dermal wounds

Collagen scaffolds are popular for the reconstitution of dermal equivalents. Usually, these scaffolds are fixed with sutures or staples and in many cases these devices have to be removed in a second procedure. Laser-mediated tissue welding in a wet environment is a potential alternative for collagen scaffold fixation and may be advantageous to suture, staple, and tissue glue fixation. Welding was performed with a continuous-wave diode laser system emitting radiation at a wavelength of 968 nm. Tensile strength after fixation to porcine skin and laser parameters were determined in vitro. In vivo, 24 excisional deep partial thickness wounds were created on flanks of two Goettingen mini pigs and covered with collagen scaffolds. These were randomized and fixated with either (1) staples, (2) fibrin glue, or (3) laser-mediated welding. Tissue biopsies for histological analysis were periodically performed and analyzed for wound healing progression, epidermal thickness, and extracellular matrix formation. Biomechanical stability after laser welding was time dependent. A dwell time of up to 10 seconds led to a strong bonding with a tensile strength of more than 30 g. In vivo, the wound healing process was macroscopically comparable in all groups and showed no significant differences. Microscopic analysis determined a more progressed and quicker wound closure in both the laser and staples group compared to the fibrin glue fixated scaffold. Laser-mediated fixation led to a significantly reduced epidermal thickness when compared with stapling or fibrin glue (P < 0.05). Laser tissue welding is a feasible approach for temporary fixation of collagen scaffolds to the wound bed. It improves wound healing properties and may lead to faster wound healing and cosmetically better scarring. Laser tissue welding is thus a very interesting and promising alternative to currently established fixation methods in a single step, no touch procedure.

The effect of a keratin-based dressing on the epithelialization of deep partial thickness wounds

The effect of a keratin-based dressing on the epithelialization of deep partial thickness wounds

Behandlung der Verbrennungswunde in der Praxis – Welche Kriterien dienen der Einschätzung der Wunde?

Burn injuries are a common trauma. Burn injuries to the skin are divided according their depth into erythema, superficial partial thickness, deep partial thickness and full thickness wounds. Superficial partial thickness wounds are characterized by intense pain and a positive blanching test. Superficial partial thickness wounds of up to 10 % total body surface area can be treated as out-patients. Large burns and those at critical areas like hand, face and genitalia should be treated in surgical departments or may require treatment at specialized burn centers. Superficial partial thickness burns are treated topically with antimicrobial ointments or wound dressings. It is of major importance to avoid desiccation of the wound bed. Reepithelialization should be completed by day 14. Infection of the wound or a non-healing wound makes surgical intervention necessary. In the case of postburn scarring silicon dressings and compression garments are necessary.

Behandlung der Verbrennungswunde in der Praxis – Welche Kriterien dienen der Einschätzung der Wunde?

Die kutane Verbrennung stellt eine häufige Verletzung dar. Verbrennungen werden bezüglich der Verbrennungstiefe in 1-, 2a-, 2b-, 3- und 4-gradige Verbrennungen eingeteilt. 2a-gradige Verbrennungen, die nur bis in die oberflächlichen Anteile der Dermis reichen und durch erhebliche Schmerzen und positive Rekapilarisierung erkennbar sind, werden konservativ behandelt. Großflächige Verbrennungen (> 15 %-2a-gradig bei Erwachsenen) und Verbrennungen an speziellen Lokalisationen (Gesicht, Hände, Genitale) sind jedoch stationär zu behandeln. Die konservative Behandlung wird mit topischen Salben und Wundauflagen durchgeführt. Ein Austrocknen des Wundgrundes ist zu vermeiden. Die Reepithelisierung sollte nach 14 Tagen abgeschlossen sein. Infizierte Wunden oder eine ausbleibende Heilung machen eine operative Intervention notwendig. Eine Nachbehandlung mit Narbenpflege und Kompression kann auch bei konservativ behandelten zweitgradigen Verbrennungswunden notwendig sein.

117 Can Platelet-Rich Plasma Gels Enhance Epithelization of Deep Partial Thickness Wounds?

Background: Platelets are a rich source of proteins and growth factors that are instrumental in the initiation and modulation of tissue repair. The clinical use of crude platelet preparations has been around for decades. However, the use of autologous platelet gel (APG) for the treatment of wounds has become familiar practice in only the past 10 years. Platelet gels have been associated with accelerated vascular ingrowth, increased fibroblastic proliferation, and accelerated collagen production.x3 Objective: The purpose of this study was to examine the effects of APG using a porcine wound healing model. Methods: Platelet rich plasma (PRP) was obtained using a fully automated, easy-to-use devise. APG was created from PRP and autologous thrombin. Deep partial thickness wounds were created on specific pathogen-free pigs. Wounds were either treated with APG and covered with a polyurethane dressing, were treated only with a polyurethane dressing, or were left untreated. Wounds were assessed for epithelization using a well-established salt-split technique. Results: Wounds treated with APG enhanced the rate of epithelization as compared to both polyurethane and untreated controls. Conclusions: This study shows that an autologous platelet rich gel can stimulate and enhance epithelization of deep partial thickness wounds. Additional preclinical and clinical studies that examine mechanisms of action are warranted.

093 Myofibroblasts in Female Red Duroc Pig Scars

Introduction: Myofibroblasts are a subtype of fibroblasts, which appear temporally during wound healing. Young hypertrophic scar contains a large number of myofibroblasts and the number declines over time. It has been shown that deep partial-thickness wounds on the female, red Duroc pig heal with thick scars, which is similar to hypertrophic scar. As part of our validation of the Duroc model of hypertrophic scarring, we evaluated myofibroblasts in wounds on the Duroc pigs. Methods: Superficial (0.015″ to 0.030″) and deep (0.045″ to 0.060″) wounds were created on the backs of 12 Durocs. Biopsies were taken at weeks 1, 2, 4, 15, and 21 postwounding. Samples were analyzed by immunochemical staining for alpha smooth muscle actin (a-SMA, for myofibroblasts) and heat-shock protein (HSP47, for fibroblasts). HSP47 positive cells were counted at 40X and the fraction of a-SMA positive cells out of fibroblasts was evaluated at 10X. Statistical significance was calculated with the Kruskal-Wallis test. Results: The counts of HSP47 and a-SMA positive cells are shown in the table below. In brief, in deep wounds most of the HSP47 positive cells were a-SMA positive at 1 and 2 weeks but this declined rapidly thereafter. In shallow wounds there were far fewer cells positive for a-SMA and the decline was even more rapid. 1W 2W 4W 15W 21W Number Shallow 105 ± 22 151 ± 59 106 ± 23 57 ± 20 44 ± 4 HSP47 Deep 524 ± 45 449 ± 35 231 ± 73 108 ± 30 55 ± 8 P value <0.05 <0.05 <0.05 <0.05 Percent Shallow 23% 3% 0 0 0 a-SMA Deep 90% 74% 10% 0 0 P value <0.05 <0.05 Conclusions: a-SMA positive fibroblasts (myofibroblasts) are present in deep Duroc wounds and the temporal pattern is similar to that reported for human hypertrophic scar. This further validates the female red Duroc model of human hypertrophic scarring.

Construction, application and biosafety of silver nanocrystalline chitosan wound dressing

A novel wound dressing composed of nano-silver and chitosan was fabricated using a nanometer and self-assembly technology. Sterility and pyrogen testing assessed biosafety, and efficacy was evaluated using Sprague–Dawley rats with deep partial-thickness wounds. Silver sulfadiazine and chitosan film dressings were used as controls. At intervals wound areas were measured, wound tissues biopsied and blood samples taken. Compared with the controls, the silver nanocrystalline chitosan dressing significantly ( p < 0.01) increased the rate of wound healing and was associated with silver levels in blood and tissues lower than levels associated with the silver sulfadiazine dressing ( p < 0.01). Sterility and pyrogen tests of the silver nanocrystalline chitosan dressing were negative. Thus this dressing should have wide application in clinical settings.

Making sense of hypertrophic scar: a role for nerves

Healed partial thickness wounds including burns and donor sites cause hypertrophic scar formation and patient discomfort. For many patients with hypertrophic scars, pruritus is the most distressing symptom, which leads to wound excoriation and chronic wound formation. In spite of the clinical significance of abnormal innervation in scars, the nervous system has been largely ignored in the pathophysiology of hypertrophic scars. Evidence that neuropeptides contribute to inflammatory responses to injury include inflammatory cell chemotaxis, cytokine and growth factor production. The neuropeptide substance P, which is released from nerve endings after injury, induces inflammation and mediates angiogenesis, keratinocyte proliferation, and fibrogenesis. Substance P activity is tightly regulated by neutral endopeptidase (NEP), a membrane bound metallopeptidase that degrades substance P at the cell membrane. Altered substance P levels may contribute to impaired cutaneous healing responses associated with diabetes mellitus or hypertrophic scar formation. Topical application of exogenous substance P or an NEP inhibitor enhances wound closure kinetics in diabetic murine wounds suggesting that diabetic wounds have insufficient substance P levels to promote a neuroinflammatory response necessary for normal wound repair. Conversely, increased nerve numbers and neuropeptide levels with reduced NEP levels in human and porcine hypertrophic scar samples suggest that excessive neuropeptide activity induces exuberant inflammation in hypertrophic scars. Given these observations about the role of neuropeptides in cutaneous repair, neuronal modulation of repair processes at two extremes of abnormal wound healing, chronic non-healing ulcers in type II diabetes mellitus and hypertrophic scars in deep partial thickness wounds, may provide therapeutic targets.

Investigating the depth of thermal burns in elephants

Histological examination of burn injuries in elephants revealed that the depth was not as severe as expected from clinical observation. Although the actual burn depth was deep, the thickness of elephant skin, especially the dermis, resulted in the lesions being classified as less severe than expected. Examination of skin samples from selected areas showed that most lesions were either superficial (1st degree) or superficial partial-thickness (superficial 2nd degree) burns with the occasional deep partial thickness (deep 2nd degree) wound. These lesions however, resulted in severe complications that eventually led to the death of a number of the elephants.

Treatment of deep partial thickness burns by a single dressing of porcine acellular dermal matrix

To explore the effect of one dressing of porcine acellular dermal matrix on deep partial thickness burns. From January 1997 to January 2004, sixty-seven cases of deep partial thickness total burned surface area (TBSA) from 50% to 90% burn wound were treated by a single dressing of porcine acellular dermal matrix (the porcine acellular dermal matrix group). Ten cases of deep partial thickness burned patients with the same TBSA treated by exposure method served as the exposure method group. The healing time of the wound was observed. The patients were followed up for 3 months to 2 years, and the scar proliferation was observed. The deep partial-thickness wound would be healed without dressing change in the porcine acellular dermal matrix group, and the average healing time was (12.2 +/- 2.6) days. The average healing time of the exposure method group was (27.4 +/- 3.5) days. Follow up of the patients within 3 months to 2 years showed that scar proliferation in the porcine acellular dermal matrix group was much less than that in the exposure method group, even no scar proliferation was observed in some patients. Without tangential excision, autografting and dressing change, a single dressing of porcine acellular dermal matrix on deep partial thickness burn wound could shorten the healing time and inhibit scar proliferation.

Severe Burns as a Consequence of Seizure while Showering: Risk Factors and Implications for Prevention

Severe Burns as a Consequence of Seizure while Showering: Risk Factors and Implications for Prevention

Acceleration of Wound Healing by Gelatin Film Dressings with Epidermal Growth Factor

We examined in vivo efficiency of a gelatin film sheet with epidermal growth factor (EGF) for a novel therapeutic device for cutaneous wound repair. NIH3T3 fibroblasts and PAM212 keratinocytes proliferated when the cells were incubated with the homogenate of EGF containing gelatin sheets, indicating that the gelatin sheet retained biologic activity of EGF in the process of sheet formation. To evaluate therapeutic effects, the EGF containing gelatin sheets or control sheets were applied onto partial-thickness skin wounds made on dorsa of hairless dogs. Wound closure in wounds treated with EGF containing gelatin sheets was accelerated when compared to that of wounds treated with control sheets, exhibiting earlier reepithelialization of the epidermis and highly regulated repair of extracellular matrix in the dermis. Therefore, we concluded that the gelatin film is a useful material to keep EGF stable and the EGF containing sheet has the ability to become an efficient therapeutic agent for superficial or deep partial-thickness wounds in the skin.

Cultured epidermal autograft and the treatment of the massive burn injury.

As a rule, adult and pediatric patients with thermal injuries that involve more than 90% total body surface area (TBSA) burn have poor prognoses. Even for patients who are 5 to 34 years old with a 70% TBSA burn, the mortality rate is 80%. Lack of autologous donor skin, which is essential for permanent wound closure, is the major problem. Recent advances in growth of cultured epidermal autograft (CEA) have allowed closure of full- and partial-thickness burns; in approximately 3 weeks, a 2 cm2 biopsy specimen will produce enough CEA to cover a pediatric patient. Since 1989, we have used this product on nine patients; the average age was 39, and the average TBSA burn was 70% (range, 44% to 93%). We report our approach to use of CEA in six of these patients, including topical applications of 1% silver sulfadiazine and excision of full- and deep partial-thickness wounds within 2 weeks of injury. Temporary closure was achieved with cadaver allograft. "Take" of the allograft forecasted take of CEA. The total operative time of CEA placement was decreased by a two-step technique that obviates repeating debridement: the technique consists of debriding and grafting with allograft, then removing it at the time of CEA placement. CEA take is best on early granulation tissue or freshly excised wounds. Early excision of burn eschar, temporary wound closure with cadaveric allograft and Biobrane (Winthrop Pharmaceuticals, Wound Care Div., Fountain Valley, Calif.), and permanent closure with CEA may improve survival rates among patients with massive burn wounds. CEA is a tremendous asset to the management of massive burn injuries.

Cultured epidermal autografts

In the early 1950s Billingham and Reynolds 1 demonstrated that epidermal sheets and epidermal cell suspensions obtained after trypsinization could be used to cover superficial wounds in experimental animals. Subsequent experiments in the late 1960s and early 1970s by Karasek. 2 Karasek and Charlton, 3 Freeman and co-workers, 4 and Igel et al. 5 proposed that epidermal cells grown in tissue culture could feasibly be transplanted onto wounds and that such cells would continue to grow and differentiate in vivo. In the late 1970s, Rheinwald and Green 6 and Green et al. 7 developed a system of culturing difficult-to-grow keratinocytes on lethally irradiated fibroblasts derived from a well-known mouse line (3T3). This technique for growing keratinocytes in culture made it possible to successfully grow and expand relatively small numbers of these cells into multilayered epithelium suitable for grafting. Growing keratinocytes in the absence of feeder layers, collagen substrates, or adhesive glycoproteins was achieved in 1979 by Eisinger and colleagues. 8 Keratinocytes could be grown into differentiated multilayered epidermal sheets provided that the pH of the culture medium was decreased (≅ 5.6) and the seeding density was optimal (2.5 × 10 5 cells/cm 2). In 1980, Eisinger et al. 9 demonstrated that cultured epidermal autografts could be used to cover deep partial-thickness wounds on dogs, pigs, and mice. Although it has been demonstrated that cultured epidermal autografts can be successfully transplanted onto partial-thickness wounds, there is very little, if any, objective data evaluating their potential effect on the healing process. This study was undertaken to evaluate objectively and to compare (1) the effect of epidermal autografts (grown on 3T3 feeder layers or on plastic) and wound occlusion on the healing of controlled partial-thickness wounds and (2) the effect of epidermal autografts. a collagen matrix (with or without keratinocytes), and occlusion alone on the healing and contraction of full-thickness wounds in swine.

Permeability of thermally damaged skin V: Permeability over the course of maturation of a deep partial-thickness wound

The permeability of eschar is an important factor governing rational approaches to topical control of burn wound sepsis. Previous work has shown the burn wound to have a highly variable permeability immediately after burning depending on the manner of burning. But the burn is also a dynamic wound and its physical state changes during the process of maturation. The present studies are an early attempt to characterize wound permeability as a function of maturation. Hairless mice were burned dorsally for 15 seconds on a metal surface maintained at 80°C. The time and temperature conditions were chosen to effect a deep partial-thickness to full-thickness injury on the animal. Mice were sacrificed daily post burn over a 2-week period and the permeabilities of 3H-methanol and 14C-butanol through the excised eschar were measured. The eschar permeability coefficients were directly compared to permeability coefficients for the same compounds found with abdominal skin sections taken concurrently from each animal. It was observed that the branding initially caused a 50 per cent increase in the permeability of methanol and a 300–400 per cent increase in the permeability of butanol. These factors held over the first 4 to 5 days of maturation. Thereafter permeabilities tended to increase, gradually at first, but accelerating to a maximum which was observed at approximately 10 days. At the maximum, methanol's permeability was 20 times and butanol's 12 times their normal values. For both compounds permeability of eschar decreased past the maximum until termination of the studies at 14 days.