S. Langer

Host defense peptides in wound healing.

Host defense peptides are effector molecules of the innate immune system. They show broad antimicrobial action against gram-positive and -negative bacteria, and they likely play a key role in activating and mediating the innate as well as adaptive immune response in infection and inflammation. These features make them of high interest for wound healing research. Non-healing and infected wounds are a major problem in patient care and health care spending. Increasing infection rates, growing bacterial resistance to common antibiotics, and the lack of effective therapeutic options for the treatment of problematic wounds emphasize the need for new approaches in therapy and pathophysiologic understanding. This review focuses on the current knowledge of host defense peptides affecting wound healing and infection. We discuss the current data and highlight the potential future developments in this field of research.

Extracorporeal shock waves improve angiogenesis after full thickness burn

OBJECTIVE Extensive wounds of burn patients remain a challenge due to wound infection and subsequent septicemia. We wondered whether extracorporeal shock wave application (ESWA) accelerates the healing process. The aim of the study was to analyze microcirculation, angiogenesis and leukocyte endothelium interaction after burns by using ESWA with two types of low intensity. METHODS Full-thickness burns were inflicted to the ears of hairless mice (n=51; area: 1.3 mm(2)). The mice were randomized into five groups: (A) low-energy shock waves after burn injury (0.04 mJ/mm(2)); (B) very low-energy shock waves after burn injury (0.015 mJ/mm(2)); (C) mice received burns but no ESWA (control group); (D) mice without burn were exposed to low-energy shock waves; (E) mice without burns and with no shock wave application. Intravital fluorescent microscopy was used to assess microcirculatory parameters, angiogenesis and leukocyte behavior. ESWA was performed on day 1, 3 and 7 (500 shoots, 1 Hz). Values were obtained straight after and on days 1, 3, 7 and 12 post burn. RESULTS Group A showed accelerated angiogenesis (non-perfused area at day 12: 5.3% vs. 9.1% (group B) and 12.6% (group C), p=0.005). Both shock wave groups showed improved blood flow after burn compared to group C. Shock waves significantly increased the number of rolling leukocytes compared to the non-ESWA-treated animals (group D: 210.8% vs. group E: 83.3%, p=0.017 on day 7 and 172.3 vs. 90.9%, p=0.01 on day 12). CONCLUSION Shock waves have a positive effect on several parameters of wound healing after burns, especially with regard to angiogenesis and leukocyte behaviour. In both ESWA groups, angiogenesis and blood flow outmatched the control group. Within the ESWA groups the higher intensity (0.04 mJ/mm(2)) showed better results than the lower intensity group. Moreover, shock waves increased the number of rolling and sticking leukocytes as a part of an improved metabolism.

Influence of anti-inflammatory and vasoactive drugs on microcirculation and angiogenesis after burn in mice

OBJECTIVE The treatment of burns remains a challenge. Besides the administration of physiological saline, local disinfection and symptomatic medications, no causal therapy is known to accelerate angiogenesis and wound healing. The aim of this study was to investigate the influences of dilatative and anti-inflammatory acting drugs on microcirculation, angiogenesis and leukocyte behavior, which had shown positive effects in former burn studies. METHODS The ears of male hairless mice (n=47) were inflicted with full thickness burns using a hot air jet. Then the affects of five intraperitoneal injections of either acetylsalicylic acid (ASA), isosorbide dinitrate, prostaglandin E1 (PGE1) or sodium chloride (each administered to one of four corresponding study groups), on microcirculation, leukocyte-endothelial interaction and angiogenesis were investigated over a 12 day period using intravital fluorescent microscopy. RESULTS Angiogenesis was slightly improved by PGE1 (0.3 vs. 1.3% non-perfused area in other groups on day 12, p=0.029). Additionally, blood flow increased and rolling leukocytes decreased compared to other groups. The ASA-group showed best functional vessel density and lowest leukocyte-adhesion. The often described posttraumatic expansion of tissue damage could not be observed in either group. CONCLUSION Prostaglandin E1 improved angiogenesis, increased the blood flow and reduced the number of rolling leukocytes. ASA had positive influences on functional vessel density, edema formation and the number of sticking leukocytes. However, it reduced the blood flow. Overall, out of all the drugs tested, prostaglandin seems to have the greatest positive impact on microcirculation and angiogenesis in burns.

Intravital Pathophysiologic Comparison of Frostbite and Burn Injury in a Murine Model

BACKGROUND The breakdown of skin microcirculation and the leukocyte-endothelium interaction are assumed to play key roles in the pathophysiology of burn and frostbite injuries. Available data on frostbite and burn injuries were collected using different experimental models and setups, which limits direct comparisons of these thermal traumata significantly. To determine pathophysiologic similarities and differences, two comparable in vivo frostbite and burn models were used to assess microcirculatory and angiogenetic changes in burn and frostbite injuries. MATERIALS AND METHODS Either deep partial thickness no-touch burns or frostbite injuries were inflicted to the ears of hairless mice (n = 40) by a hot or cold gas jet (117.0 ± 2.1°C for 1 s and -195.8 ± 2.7°C for 1.5 s, respectively) resulting in a necrotic, nonperfused area of about 1.56 ± 0.28 mm2. Intravital fluorescent microscopy was used in combination with fluorescent dyes in order to assess the microcirculation, angiogenesis, and leukocyte-activity over a 12-d period. RESULTS The angiogenesis occurred significantly faster after frostbite than after burn (16.4% ± 4.5% versus 30.6% ± 2.8% nonperfused area, compared with the baseline value on d 7 (P = 0.009)). The loss of functional vessel density was significantly more pronounced after frostbite (57.6% ± 2.2% versus 89.2% ± 4.9% (P < 0.001)). However, the area recovered faster. The edema formation, as a parameter for endothelial integrity, was significantly more pronounced and lasted longer after frostbite, compared with the burn injury, and reached its maximum level on d 7 after trauma (162.4% ± 4.2% versus 142.% ± 5.9%; P = 0.007). In contrast to the rolling leukocytes, which showed the same increase on d 1 and then a subsequent decrease in both groups, the number of adherent leukocytes after the burn was markedly higher on d 1 (480% versus 167%; P = 0.001) but decreased much faster. The number of adherent leukocytes after frostbite remained significantly higher than those of the burn group during the entire observation. CONCLUSION The comparison of analogous intravital burn and frostbite models indicates that despite the similarities, decisive microcirculatory differences in extension and recovery from these two types of thermal trauma exist.

Improved Neovascularization of PEGT/PBT Copolymer Matrices in Response to Surface Modification by Biomimetic Coating

PEGT/PBT (polyethylene glycol terephthalate/polybutylene terephthalate) copolymer matrices with three different surface coatings [calcium-phosphate (Ca-P), collagen, and gas plasma] were placed into dorsal skinfold chambers of 24 balb/c mice. Untreated PEGT/PBT matrices served as the controls. The basal surfaces of the implants directly contacted the striated skin muscle. Neovascularization of the implants was analyzed by intravital fluorescence microscopy. Microcirculatory observations were performed in the surrounding skin muscle, at the border zone of the implant, and in the center of the implant. The functional vessel density (FVD; mm/mm2), as the length of perfused microvessels per observation area, was measured by computer-assisted analysis. The FVD served as the parameter of neovascularization. At the end of the protocol, histological observation of hematoxylin/eosin-standard-stained sections was performed by light microscopy. The FVD in the center of the implant on day 8 was only observed in gas-plasma-coated (8.8 ± 10.2 mm/mm2) and Ca-P-coated implants (0.8 ± 2.0 mm/mm2). None of the other groups showed perfused microvessels in the center of the implant on day 8 (p < 0.05). The FVD values in the center of the gas-plasma-coated and the Ca-P-coated implants were 20.7 ± 8.2 and 19.2 ± 15.5 mm/mm2 as compared with 7.1 ± 17.4 and 7.7 ± 5.9 mm/mm2 for collagen-coated and untreated implants on day 16. The histological examination confirmed the profound microvascular ingrowth into the matrix pores of the gas-plasma-treated and the Ca-P-coated copolymer matrices in the center of the implants. The study showed that the ingrowth of microvessels into PEGT/PBT matrices can be accelerated by Ca-P coating and gas plasma treatment in the dorsal skinfold chamber in mice.

Resektionsgrenzen bei Weichgewebssarkomen der Extremitäten

Negative surgical margins (R0 resection) play a key role in the prevention of local recurrences of soft tissue sarcoma of the extremities in the multimodal therapy concept. The prognostic relevance for long-term survival is still under dispute. Despite the fact that numerous recommendations and guidelines have existed for over 100 years, strong evidence-based data from prospective randomized studies are still not available today. These studies should include parameters like tumor localization, subtype and biological aggressiveness. Recommendations as to surgical therapy diverge considerably. They range from amputation and compartment resection to centimetre and millimetre surgical margins. The present article analyses currently available data and definitions and discusses the impact on functional restriction, lymph drainage, local recurrence and the perioperative irradiation field. In the absence of surgical standards, it is doubtful whether existing studies and multicenter trials currently underway are valid. Close co-operation between surgeon and pathologist is imperative to further substantiate the significance of histological examinations and resection margins.

Surface modification by glow discharge gasplasma treatment improves vascularization of allogenic bone implants.

Sufficient induction of blood vessel ingrowth decisively influence transplant functionality. In this study, microvascular response to transplants of surface modified bone substitutes were assessed in vivo. The surface modification of allogenic bone substitutes (dehydrated human femoral head) was achieved in a double‐conductive low‐pressure gasplasma reactor (Ar2/O2, 13.65 MHz, 1,000 W, 5 Pa). The modified bone substitutes (n = 10) as well as untreated bone substitutes serving as controls (n = 10) were placed into the dorsal skinfold chamber of female balb/c mice (n = 10). Dynamic assessment of microcirculatory parameters was performed using intravital fluorescence microscopy during an implantation period of 10 days. The angiogenic response was found markedly accelerated in gasplasma‐treated bone. Compared to untreated implants, the gasplasma‐activated bone substitutes showed significantly higher microvascular density on days 5 and 10. The quantification of the microvascular diameters, red blood cell velocity, and microvascular permeability displayed stable perfusion and vascular integrity of the newly developed blood vessels throughout the 10‐day observation period. The surface activation via cold low‐pressure glow discharge gasplasma supports the vascular integration of allogenic bone by earlier induction of the angiogenesis.

Clinical Safety and Efficacy of a Novel Thermoreversible Polyhexanide-Preserved Wound Covering Gel

Background: An ideal topical formulation for wound therapy does not exist. The aim of this study was to develop a novel improved therapeutic option for the treatment of acute and chronic wounds. Methods: A transparent wound gel which is in a liquid state below and in a gel state at or above room temperature was developed. Forty-four patients were included in this open randomized controlled single-center study. Flammazine™ served as control in the treatment of skin graft donor sites. Wounds were assessed for time of dressing change and overall satisfaction of patients and health care providers. The data were analyzed using the nonparametric Mann-Whitney test. Results: The wound gel proved to be superior in comparison with Flammazine with respect to wound assessment (p = 0.002), staining (p = 0.007), leaking (p = 0.032) and smell (p = 0.034). Flammazine showed favorable results regarding the parameters dehydration of the dressings (p = 0.012) and wound adherence (p = 0.005). The evaluation of the overall dressing change process showed no significant differences. Conclusion: The thermoreversible wound gel containing polyhexanide allows for good handling and wound assessment. This study demonstrated a high satisfaction level of patient and health care providers, and the wound gel proved an effective alternative to commonly used treatments.

Enhanced neovascularization of dermis substitutes via low-pressure plasma-mediated surface activation

PURPOSE The effect of cold low-pressure plasma treatment on neovascularization of a dermis substitute was evaluated in a mouse model. MATERIAL AND METHODS Collagen-elastin matrices (Matriderm(®)) were used as scaffolds. Low-pressure argon/hydrogene plasma-treated scaffolds were transplanted into the dorsal skinfold chambers of balb/c mice (group 1, n=10). Untreated scaffolds served as controls (group 2, n=10). Intravital fluorescence microscopy was performed within the border zone of the scaffolds on days 1, 5 and 10. Functional vessel density (FVD), vessel diameter, intervascular distance, microvascular permeability, and leukocyte-endothelium interaction were analyzed. RESULTS An increase of FVD associated with a reduction of the intervascular distance was observed. Statistical analysis revealed that the functional vessel density in the border zone of the scaffolds was significantly enhanced in the plasma-treated group compared to controls. For group 1, an increase of FVD from 282±8 cm/cm(2) on days 5 to 315±8 cm/cm(2) on day 10 was observed. Whereas values of 254±7 cm/cm(2) on day 5 and 275±13 cm/cm(2) on day 10 have resulted in group 2 (mean±S.E.M., Students t-test, p<0.05). CONCLUSION The surface treatment by cold low-pressure plasma intensifies the angiogenesis and accelerates the neovascularization of collagen-elastin matrix.

Photoplanimetric evaluation and impedance measurement of split-thickness skin grafts: a new model for objective wound-healing assessment in clinical trials

Purpose: The objective assessment of wound healing is a challenging task especially in the context of clinical trials. Because the clinical evaluation of wounds and the wound‐healing quality is often influenced by the subjective view of the physician, there is great need for a reliable, quantitative and objective wound model that would help to obtain statistically useful data. Here, we present a wound model and non‐invasive analysis techniques to evaluate human wound healing. The model described was used in a clinical trial on 167 patients treated with a new wound therapeutic agent.