The Microvasculature in Cutaneous Wound Healing in the Female Red Duroc Pig Is Similar to That in Human Hypertrophic Scars and Different From That in the Female Yorkshire Pig

Concise Review on Scientific Approaches to Burns and Scars

Burns are large open surgical lesions bathed in virulent pus that result in rupturing of the cutaneous membrane, which has serious consequences such as an extensive loss of proteins, and body fluids, increased chances of infections, and sometimes death. These can be classified based on their penetration levels, i.e., first-degree burns penetrating the epidermis, second-degree burns including both epidermis and dermis, third-degree burns to both layers including the hair follicular cells, sweat glands and various core tissues, fourth-degree burns to adipose tissue, fifth stage burns to muscles, and sixth stage burns to bones. Wound healing/wound repair is a very perplexing process in which the tissues of the affected/burnt area repairs themselves to attain their original form and functionality but develop a scar at the wound site. This article mainly focuses on the algorithms to differentiate various degrees of burns, general first aid approaches to burns and scars, the rationale of treatment of burns, basic mechanisms highlighting the healing processes in humans in terms of free from scar formation as well as with scar formation at their elementary levels including cellular as well as biochemical levels, utility, and progression of pre-clinical data to humans and finally approaches for the improvement of scar formation in man.

Angiogenic gene characterization and vessel permeability of dermal microvascular endothelial cells isolated from burn hypertrophic scar

Hypertrophic scar (HTS) formation is a common challenge for patients after burn injury. Dermal microvascular endothelial cells (DMVECs) are an understudied cell type in HTS. An increase in angiogenesis and microvessel density can be observed in HTS. Endothelial dysfunction may play a role in scar development. This study aims to generate a functional and expression profile of HTS DMVECs. We hypothesize that transcript and protein-level responses in HTS DMVECs differ from those in normal skin (NS). HTSs were created in red Duroc pigs. DMVECs were isolated using magnetic-activated cell sorting with ulex europaeus agglutinin 1 (UEA-1) lectin. Separate transwell inserts were used to form monolayers of HTS DMVECs and NS DMVECs. Cell injury was induced and permeability was assessed. Gene expression in HTS DMVECS versus NS DMVECs was measured. Select differentially expressed genes were further investigated. HTS had an increased area density of dermal microvasculature compared to NS. HTS DMVECs were 17.59% less permeable than normal DMVECs (p < 0.05). After injury, NS DMVECs were 28.4% and HTS DMVECs were 18.8% more permeable than uninjured controls (28.4 ± 4.8 vs 18.8 ± 2.8; p = 0.11). PCR array identified 31 differentially expressed genes between HTS and NS DMVECs, of which 10 were upregulated and 21 were downregulated. qRT-PCR and ELISA studies were in accordance with the array. DMVECs expressed a mixed profile of factors that can contribute to and inhibit scar formation. HTS DMVECs have both a discordant response to cellular insults and baseline differences in function, supporting their proposed role in scar pathology. Further investigation of DMVECs is warranted to elucidate their contribution to HTS pathogenesis.

In Vivo Models for Hypertrophic Scars—A Systematic Review

Backgroundand Objectives: Hypertrophic scars following surgeries or burns present a serious concern for many patients because these scars not only lead to an aesthetical but also to a functional and psychological burden. Treatment of hypertrophic scars is challenging because despite various treatment options, a low level of evidence hinders preference of any specific treatment plan. To properly identify new therapeutic approaches, the use of in vivo models remains indispensable. A gold standard for hypertrophic scars has not been established to date. This review aims at giving a comprehensive overview of the available in vivo models. Materials and Methods: PubMed and CINAHL were queried for currently existing models. Results: Models with mice, rats, rabbits, pigs, guinea pigs and dogs are used in hypertrophic scar research. Rodent models provide the advantage of ready availability and low costs, but the number of scars per animal is limited due to their relatively small body surface, leading to a high number of test animals which should be avoided according to the 3Rs. Multiple scars per animal can be created in the guinea pig and rabbit ear model; but like other rodent models, these models exhibit low transferability to human conditions. Pig models show a good transferability, but are cost-intensive and require adequate housing facilities. Further, it is not clear if a currently available pig model can deliver clinical and histological features of human hypertrophic scars concurrently. Conclusions: None of the analyzed animal models can be clearly recommended as a standard model in hypertrophic scar research because the particular research question must be considered to elect a suitable model.

Comparative Transcriptome Analysis of Superficial and Deep Partial-Thickness Burn Wounds in Yorkshire vs Red Duroc Pigs

Hypertrophic scars are a common negative outcome of deep partial-thickness burn wounds resulting in increased dermal thickness, wound area contracture, and inflammation of the affected area. The red Duroc and Yorkshire porcine breeds are common large animal models for studying dermal wounds due to their structural similarities to human skin; however, the porcine transcriptomic profiles of dermal burn wounds and healing process are not well known. In response, a longitudinal transcriptomic comparative study was conducted comparing red Duroc and Yorkshire superficial and DPT burn wounds to their respective control uninjured tissue. Using next-generation RNA-sequencing, total RNAs were isolated from burn wound tissue harvested at 0, 3, 7, 15, 30, and 60 days post-burn and mRNA-seq and gene expression read counts were generated. Significant differentially expressed genes relative to uninjured tissue were defined and active biological processes were determined using gene set enrichment analyses. Additionally, collagen deposition, α-SMA protein concentration, epidermal and dermal thickness measurements, and wound area changes in response to burn injury were characterized. Overall, the red Duroc pigs, in response to both burn wound types, elicited a more robust and prolonged inflammatory immune response, fibroblast migration and proliferation as well as heightened levels of extracellular matrix modulation relative to respective burn types in the Yorkshire pigs. Collectively, the red Duroc deep partial-thickness burn wounds produce a greater degree of hypertrohic scar like response compared to Yorkshire DPT burn wounds. These findings will facilitate future porcine burn studies down-selecting treatment targets and determining effects of novel therapeutic strategies.

In-depth examination of hyperproliferative healing in two breeds of Sus scrofa domesticus commonly used for research

Background

Wound healing can result in various outcomes, including hypertrophic scar (HTS). Pigs serve as models to study wound healing as their skin shares physiologic similarity with humans. Yorkshire (Yk) and Duroc (Dc) pigs have been used to mimic normal and abnormal wound healing, respectively. The reason behind this differential healing phenotype was explored here.

Methods

Excisional wounds were made on Dc and Yk pigs and were sampled and imaged for 98 days. PCR arrays were used to determine differential gene expression. Vancouver Scar Scale (VSS) scores were given. Re-epithelialization was analyzed. H&E, Mason's trichrome, and immunostains were used to determine cellularity, collagen content, and blood vessel density, respectively.

Results

Yk wounds heal to a "port wine" HTS, resembling scarring in Fitzpatrick skin types (FST) I-III. Dc wounds heal to a dyspigmented, non-pliable HTS, resembling scarring in FST IV-VI. Gene expression during wound healing was differentially regulated versus uninjured skin in 40/80 genes, 15 of which differed between breeds. Yk scars had a higher VSS score at all time points. Yk and Dc wounds had equivalent re-epithelialization, collagen disorganization, and blood vessel density.

Conclusions

Our findings demonstrate that Dc and Yk pigs can produce HTS. Wound creation and healing were consistent among breeds, and differences in gene expression were not sufficient to explain differences in resulting scar phenotype. Both pig breeds should be used in animal models to investigate novel therapeutics to provide insight into a treatment's effectiveness on various skin types.

The pig as a model system for investigating the recruitment and contribution of myofibroblasts in skin healing

In the skin-healing field, porcine models are regarded as a useful analogue for human skin due to their numerous anatomical and physiological similarities. Despite the widespread use of porcine models in skin healing studies, the initial origin, recruitment and transition of fibroblasts to matrix-secreting contractile myofibroblasts are not well defined for this model. In this review, we discuss the merit of the pig as an animal for studying myofibroblast origin, as well as the challenges associated with assessing their contributions to skin healing. Although a variety of wound types (incisional, partial thickness, full thickness, burns) have been investigated in pigs in attempts to mimic diverse injuries in humans, direct comparison of human healing profiles with regards to myofibroblasts shows evident differences. Following injury in porcine models, which often employ juvenile animals, myofibroblasts are described in the developing granulation tissue at 4 days, peaking at Days 7-14, and persisting at 60 days post-wounding, although variations are evident depending on the specific pig breed. In human wounds, the presence of myofibroblasts is variable and does not correlate with the age of the wound or clinical contraction. Our comparison of porcine myofibroblast-mediated healing processes with those in humans suggests that further validation of the pig model is essential. Moreover, we identify several limitations evident in experimental design that need to be better controlled, and standardisation of methodologies would be beneficial for the comparison and interpretation of results. In particular, we discuss anatomical location of the wounds, their size and depth, as well as the healing microenvironment (wet vs. moist vs. dry) in pigs and how this could influence myofibroblast recruitment. In summary, although a widespread model used in the skin healing field, further research is required to validate pigs as a useful analogue for human healing with regards to myofibroblasts.

Clostridium Collagenase Impact on Zone of Stasis Stabilization and Transition to Healthy Tissue in Burns

Clostridium collagenase has provided superior clinical results in achieving digestion of immediate and accumulating devitalized collagen tissue. Recent studies suggest that debridement via Clostridium collagenase modulates a cellular response to foster an anti-inflammatory microenvironment milieu, allowing for a more coordinated healing response. In an effort to better understand its role in burn wounds, we evaluated Clostridium collagenase’s ability to effectively minimize burn progression using the classic burn comb model in pigs. Following burn injury, wounds were treated with Clostridium collagenase or control vehicle daily and biopsied at various time points. Biopsies were evaluated for factors associated with progressing necrosis as well as inflammatory response associated with treatment. Data presented herein showed that Clostridium collagenase treatment prevented destruction of dermal collagen. Additionally, treatment with collagenase reduced necrosis (HMGB1) and apoptosis (CC3a) early in burn injuries, allowing for increased infiltration of cells and protecting tissue from conversion. Furthermore, early epidermal separation and epidermal loss with a clearly defined basement membrane was observed in the treated wounds. We also show that collagenase treatment provided an early and improved inflammatory response followed by faster resolution in neutrophils. In assessing the inflammatory response, collagenase-treated wounds exhibited significantly greater neutrophil influx at day 1, with macrophage recruitment throughout days 2 and 4. In further evaluation, macrophage polarization to MHC II and vascular network maintenance were significantly increased in collagenase-treated wounds, indicative of a pro-resolving macrophage environment. Taken together, these data validate the impact of clostridial collagenases in the pathophysiology of burn wounds and that they complement patient outcomes in the clinical scenario.

Galectin-1 production is elevated in hypertrophic scar

Upon healing, burn wounds often leave hypertrophic scars (HTSs) marked by excess collagen deposition, dermal and epidermal thickening, hypervascularity, and an increased density of fibroblasts. The Galectins, a family of lectins with a conserved carbohydrate recognition domain, function intracellularly and extracellularly to mediate a multitude of biological processes including inflammatory responses, angiogenesis, cell migration and differentiation, and cell-ECM adhesion. Galectin-1 (Gal-1) has been associated with several fibrotic diseases and can induce keratinocyte and fibroblast proliferation, migration, and differentiation into fibroproliferative myofibroblasts. In this study, Gal-1 expression was assessed in human and porcine HTS. In a microarray, galectins 1, 4, and 12 were upregulated in pig HTS compared to normal skin (fold change = +3.58, +6.11, and +3.03, FDR <0.01). Confirmatory qRT-PCR demonstrated significant upregulation of Galectin-1 (LGALS1) transcription in HTS in both human and porcine tissues (fold change = +7.78 and +7.90, P <.05). In pig HTS, this upregulation was maintained throughout scar development and remodeling. Immunofluorescent staining of Gal-1 in human and porcine HTS showed significantly increased fluorescence (202.5 ± 58.2 vs 35.2 ± 21.0, P <.05 and 276.1 ± 12.7 vs 69.7 ± 25.9, P <.01) compared to normal skin and co-localization with smooth muscle actin-expressing myofibroblasts. A strong positive correlation (R = .948) was observed between LGALS1 and Collagen type 1 alpha 1 mRNA expression. Gal-1 is overexpressed in HTS at the mRNA and protein levels and may have a role in the development of scar phenotypes due to fibroblast over-proliferation, collagen secretion, and dermal thickening. The role of galectins shows promise for future study and may lead to the development of a pharmacotherapy for treatment of HTS.

Small Leucine-Rich Proteoglycans in Skin Wound Healing

Healing of cutaneous wounds is a complex and well-coordinated process requiring cooperation among multiple cells from different lineages and delicately orchestrated signaling transduction of a diversity of growth factors, cytokines, and extracellular matrix (ECM) at the wound site. Most skin wound healing in adults is imperfect, characterized by scar formation which results in significant functional and psychological sequelae. Thus, the reconstruction of the damaged skin to its original state is of concern to doctors and scientists. Beyond the traditional treatments such as corticosteroid injection and radiation therapy, several growth factors or cytokines-based anti-scarring products are being or have been tested in clinical trials to optimize skin wound healing. Unfortunately, all have been unsatisfactory to date. Currently, accumulating evidence suggests that the ECM not only functions as the structural component of the tissue but also actively modulates signal transduction and regulates cellular behaviors, and thus, ECM should be considered as an alternative target for wound management pharmacotherapy. Of particular interest are small leucine-rich proteoglycans (SLRPs), a group of the ECM, which exist in a wide range of connecting tissues, including the skin. This manuscript summarizes the most current knowledge of SLRPs regarding their spatial-temporal expression in the skin, as well as lessons learned from the genetically modified animal models simulating human skin pathologies. In this review, particular focus is given on the diverse roles of SLRP in skin wound healing, such as anti-inflammation, pro-angiogenesis, pro-migration, pro-contraction, and orchestrate transforming growth factor (TGF)β signal transduction, since cumulative investigations have indicated their therapeutic potential on reducing scar formation in cutaneous wounds. By conducting this review, we intend to gain insight into the potential application of SLRPs in cutaneous wound healing management which may pave the way for the development of a new generation of pharmaceuticals to benefit the patients suffering from skin wounds and their sequelae.

Modelling skin wound healing angiogenesis: A review

The occurrence of wounds is a main health concern in Western society due to their high frequency and treatment cost. During wound healing, the formation of a functional blood vessel network through angiogenesis is an essential process. Angiogenesis allows the reestablishment of the normal blood flow, the sufficient exchange of oxygen and nutrients and the removal of metabolic waste, necessary for cell proliferation and viability. Mathematical and computational models provide new tools to improve the healing process. In fact, over the last thirty years, in silico models have been continuously formulated to describe the effect of several biological and mechanical factors in angiogenesis during wound healing. Additionally, with different levels of complexity, these models allow coupling the human skin structure, to distinct cell types and growth factors, to study extracellular matrix composition and to understand its deformation. This paper discusses how in silico models, which are more economical and less time-consuming comparatively to laboratory methodologies, can help test new strategies to promote/optimize angiogenesis. The continuum, cell-based and hybrid mathematical models of wound healing angiogenesis are reviewed in the present paper, in order to identify possible improvements. Accordingly, the development of higher dimension models incorporating multiscale analysis at molecular, cellular and tissue level remains a challenge that future models should consider.

Fibromodulin reduces scar size and increases scar tensile strength in normal and excessive-mechanical-loading porcine cutaneous wounds

Hypertrophic scarring is a major postoperative complication which leads to severe disfigurement and dysfunction in patients and usually requires multiple surgical revisions due to its high recurrence rates. Excessive-mechanical-loading across wounds is an important initiator of hypertrophic scarring formation. In this study, we demonstrate that intradermal administration of a single extracellular matrix (ECM) molecule-fibromodulin (FMOD) protein-can significantly reduce scar size, increase tensile strength, and improve dermal collagen architecture organization in the normal and even excessive-mechanical-loading red Duroc pig wound models. Since pig skin is recognized by the Food and Drug Administration as the closest animal equivalent to human skin, and because red Duroc pigs show scarring that closely resembles human proliferative scarring and hypertrophic scarring, FMOD-based technologies hold high translational potential and applicability to human patients suffering from scarring-especially hypertrophic scarring.

Autologous adipose-derived regenerative cell therapy modulates development of hypertrophic scarring in a red Duroc porcine model

Background

Effective prevention and treatment of hypertrophic scars (HTSs), a common consequence of deep-partial thickness injury, remain a significant clinical challenge. Previous studies from our group have shown that autologous adipose-derived regenerative cells (ADRCs) represent a promising approach to improve wound healing and, thereby, impact HTS development. The purpose of this study was to assess the influence of local delivery of ADRCs immediately following deep-partial thickness cutaneous injury on HTS development in the red Duroc (RD) porcine model.

Methods

Bilateral pairs of deep-partial thickness excisional wounds (2 mm depth; 58 cm² area) were created using an electric dermatome on RD pigs (n = 12). Autologous ADRCs were isolated from the inguinal fat pad and then sprayed directly onto the wound at a dose of 0.25 × 10⁶ viable cells/cm². The paired contralateral wound received vehicle control. Wound healing and development of HTS were assessed over 6 months using digital imaging, quantitative measurement of skin hardness and pigmentation, and histology.

Results

Data showed that ADRC treatment led to reduced scar hyperpigmentation compared to control (p < 0.05). Using the Durometer, at 2 and 6 months post-injury, skin hardness was 10–20% lower in ADRCs-treated wounds compared to control vehicle (p < 0.05). A similar trend was observed with the skin fibrometer.

ADRC treatment promoted more normal collagen organization, improvement in the number of rete ridges (p < 0.01), longer elastic fiber length (p < 0.01), and reduced hypervascularity (blood vessel density; p < 0.05). ADRC treatment was associated with modulation of IL-6 expression within the wound/scar with upregulation 2 weeks after injury (wound healing phase) and downregulation at 2 months (early scarring phase) post-treatment compared to control

Conclusions

These findings support the potential therapeutic value of autologous ADRC administration for reduction of HTS development following deep-partial cutaneous injury.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0704-1) contains supplementary material, which is available to authorized users.

Dermal Remodeling of Burn Scar by Fractional CO2 Laser

BACKGROUND

Ablative CO2 fractional lasers have recently been introduced for burn scar treatment because of pronounced clinical outcomes with fewer treatment sessions than nonablative fractional laser.

OBJECTIVE

This study was conducted to observe clinical as well as histologic changes of burn scars after treatment with CO2 fractional laser.

MATERIALS AND METHODS

Eleven patients (one female and 10 males, aged 31-59 years) with skin phototypes III to V with burn scars received 10 sessions of fractional CO2 laser treatments (UltraPulse(®) Encore; Lumenis, Santa Clara, CA, USA) over an average 5-week interval. Two passes were performed using the following parameters: deep FX mode, 12.5-30 mJ, with a density setting of 5-10 %. Clinical evaluations by three blinded dermatologists were obtained at baseline and at 6 months after the final treatment via photographs using the Vancouver scar scale (VSS). Skin biopsies were done on four patients before and after treatment.

RESULTS

All patients showed clinical improvement in their scars with significant decrease in VSS. Histologic findings showed the changes in the upper dermis with newly formed dermal papilla. This characteristic upper dermis change was presented as improvement in surface smoothness and skin tension clinically. Postinflammatory hyperpigmentation and itching sensation were the most common adverse effects.

CONCLUSION

Burn scar treatment by fractional CO2 laser is effective by forming new collagen fibers mainly in the upper dermis.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The physical and physiological effects of vacuum massage on the different skin layers: a current status of the literature

Vacuum massage is a non-invasive mechanical massage technique performed with a mechanical device that lifts the skin by means of suction, creates a skin fold and mobilises that skin fold. In the late 1970s, this therapy was introduced to treat traumatic or burn scars. Although vacuum massage was invented to treat burns and scars, one can find very little literature on the effects of this intervention. Therefore, the aim of this review is to present an overview of the available literature on the physical and physiological effects of vacuum massage on epidermal and dermal skin structures in order to find the underlying working mechanisms that could benefit the healing of burns and scars. The discussion contains translational analysis of the results and provides recommendations for future research on the topic. An extended search for publications was performed using PubMed, Web of Science and Google Scholar. Two authors independently identified and checked each study against the inclusion criteria. Nineteen articles were included in the qualitative synthesis. The two most reported physical effects of vacuum massage were improvement of the tissue hardness and the elasticity of the skin. Besides physical effects, a variety of physiological effects are reported in literature, for example, an increased number of fibroblasts and collagen fibres accompanied by an alteration of fibroblast phenotype and collagen orientation. Little information was found on the decrease of pain and itch due to vacuum massage. Although vacuum massage initially had been developed for the treatment of burn scars, this literature review found little evidence for the efficacy of this treatment. Variations in duration, amplitude or frequency of the treatment have a substantial influence on collagen restructuring and reorientation, thus implying possible beneficial influences on the healing potential by mechanotransduction pathways. Vacuum massage may release the mechanical tension associated with scar retraction and thus induce apoptosis of myofibroblasts. Suggestions for future research include upscaling the study design, investigating the molecular pathways and dose dependency, comparing effects in different stages of repair, including evolutive parameters and the use of more objective assessment tools.

Ablative CO2 fractional resurfacing in treatment of thermal burn scars: an open-label controlled clinical and histopathological study

INTRODUCTION

Burn scars can cause permanent disfiguring problems with limited treatments available.

OBJECTIVES

To assess and correlate the clinical and histopathological effects of fractional CO2 laser on thermal burns in a controlled study.

METHODS

Fifteen patients 11 with hypertrophic and four with keloidal scars received three CO2 fractional laser sessions every 4-6 weeks. Half of the scar was untreated as a control. Clinical evaluation by Vancouver, PSOAS scores, and photography before, monthly, and 3 months after the last laser session was performed. Ten patients were evaluated histopathologically by standard H&E, Masson trichrome, and Elastica von Gieson special stains.

RESULTS

Hypertrophic scars (HTSs) showed textural improvement and a significant decrease of Vancouver, POSAS observer, and patient scores by the end of follow-up period in the laser-treated area (P = 0.011, 0.017 and 0.018, respectively) unlike keloidal scars. Histopathology revealed significant decrease in scar thickness in HTSs only (P < 0.001) as well as a significant decrease in collagen bundle thickness and density in the upper dermis in both types of scars.

CONCLUSIONS

Fractional CO2 laser is a possible safe and effective modality for the treatment of hypertrophic burn scars with improvement achieved both clinically and histopathologically.

Commercially available topical platelet-derived growth factor as a novel agent to accelerate burn-related wound healing

The authors investigated whether the application of platelet-derived growth factor (PDGF) to donor site wounds would speed healing in a porcine model. In a red duroc pig model, three wounds that were 3 inches × 3 inches were created with a dermatome (0.06-inch depth) on one side of two different animals. These wounds were digitally and laser Doppler (LDI) imaged and biopsied immediately pre- and postwound creation and every 2 days for 2 weeks. A set of identical wounds were subsequently created on the opposite side of the same animals and treated with topical PDGF (becaplermin gel 0.01%, 4 g/wound) immediately on wounding. PDGF-treated wounds were imaged and biopsied as above. Digital images of wounds were assessed for epithelialization by clinicians using an ordinal scale. Perfusion units (PU) were evaluated by LDI. Wound healing was evaluated by hematoxylin and eosin histological visualization of an epithelium and intact basement membrane. First evidence of partial epithelialization was seen in control and PDGF-treated wounds within 7.7 ± 1.4 and 6.4 ± 1.1 days postwounding, respectively (P=.03). Completely epithelialized biopsies were seen in control and PDGF-treated wounds at 11.7 ± 2.6 and 9.6 ± 1.5 days, respectively (P=.02). Clinician evaluation of digital images showed that on day 9, control wounds were, on average, 48.3 ± 18.5% epithelialized vs 57.2 ± 20.2% epithelialized for PDGF-treated wounds. At day 16, control wounds showed an average of 72.9 ± 14.6% epithelialization and PDGF-treated wounds showed an average of 90 ± 11.8%epithelialization. Overall, PDGF-treated wounds had statistically significantly higher scores across all timepoints (P=.02). Average perfusion units as measured by LDI were similar for control and PDGF-treated wounds at time of excision (225 ± 81and 257 ± 100, respectively). On day 2 postwounding, average PU for control wounds were 803 and were 764 for PDGF-treated wounds. Control wounds maintained higher PU values compared with PDGF-treated wounds at all time points and returned to excision PU values by day 12.2 ± 1.1 postwounding. PDGF-treated wounds reached the same values by day 9.7 ± 2.3 (P=.03). The authors conclude that topical PDGF speeds time to epithelialization of partial-thickness wounds in a porcine model as evidenced by histology, clinical appearance, and time to return to prewounding vascularity.

A polarized multispectral imaging system for quantitative assessment of hypertrophic scars

Hypertrophic scars (HTS) are a pathologic reaction of the skin and soft tissue to burn or other traumatic injury. Scar tissue can cause patients serious functional and cosmetic issues. Scar management strategies, specifically scar assessment techniques, are vital to improve clinical outcome. To date, no entirely objective method for scar assessment has been embraced by the medical community. In this study, we introduce for the first time, a novel polarized multispectral imaging system combining out-of-plane Stokes polarimetry and Spatial Frequency Domain Imaging (SFDI). This imaging system enables us to assess the pathophysiology (hemoglobin, blood oxygenation, water, and melanin) and structural features (cellularity and roughness) of HTS. To apply the proposed technique in an in vivo experiment, dermal wounds were created in a porcine model and allowed to form into scars. The developed scars were then measured at various time points using the imaging system. Results showed a good agreement with clinical Vancouver Scar Scale assessment and histological examinations.

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

BACKGROUND

Hypertrophic 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 FINDINGS

We 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/SIGNIFICANCE

1) 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.

Surgical approaches to create murine models of human wound healing

Wound repair is a complex biologic process which becomes abnormal in numerous disease states. Although in vitro models have been important in identifying critical repair pathways in specific cell populations, in vivo models are necessary to obtain a more comprehensive and pertinent understanding of human wound healing. The laboratory mouse has long been the most common animal research tool and numerous transgenic strains and models have been developed to help researchers study the molecular pathways involved in wound repair and regeneration. This paper aims to highlight common surgical mouse models of cutaneous disease and to provide investigators with a better understanding of the benefits and limitations of these models for translational applications.

Therapeutic improvement of scarring: mechanisms of scarless and scar-forming healing and approaches to the discovery of new treatments

Scarring in the skin after trauma, surgery, burn or sports injury is a major medical problem, often resulting in loss of function, restriction of tissue movement and adverse psychological effects. Whilst various studies have utilised a range of model systems that have increased our understanding of the pathways and processes underlying scar formation, they have typically not translated to the development of effective therapeutic approaches for scar management. Existing treatments are unreliable and unpredictable and there are no prescription drugs for the prevention or treatment of dermal scarring. As a consequence, scar improvement still remains an area of clear medical need. Here we describe the basic science of scar-free and scar-forming healing, the utility of pre-clinical model systems, their translation to humans, and our pioneering approach to the discovery and development of therapeutic approaches for the prophylactic improvement of scarring in man

Near-infrared photoinactivation of bacteria and fungi at physiologic temperatures

We examined a laser system (870 and 930 nm), employing wavelengths that have exhibited cellular photodamage properties in optical traps. In vitro, with 1.5 cm diameter flat-top projections (power density of 5.66 W cm(-2)), at physiologic temperatures, we achieved photoinactivation of Staphylococcus aureus, Escherichia coli, Candida albicans and Trichophyton rubrum. Using nonlethal dosimetry, we measured a decrease in trans-membrane potentials (DeltaPsimt and DeltaPsip) and an increase in reactive oxygen species (ROS) generation in methicillin-resistant S. aureus (MRSA), C. albicans and human embryonic kidney cells. We postulate that these multiplexed wavelengths cause an optically mediated mechano-transduction of cellular redox pathways, decreasing DeltaPsi and increasing ROS. The cellular energetics of prokaryotic and fungal pathogens, along with mammalian cells, are affected in a similar manner when treated with these multiplexed wavelengths at the power densities employed. Following live porcine thermal tolerance skin experiments, we then performed human pilot studies, examining photodamage to MRSA in the nose and fungi in onychomycosis. No observable damage to the nares or the nail matrix was observed, yet photodamage to the pathogens was achieved at physiologic temperatures. The selective aspect of this near-infrared photodamage presents the possibility for its future utilization in human cutaneous antimicrobial therapy.

Connexin43 carboxyl-terminal peptides reduce scar progenitor and promote regenerative healing following skin wounding

AIM

Gap-junctional connexin43 (Cx43) has roles in multiple aspects of skin wound healing - including scarring. The aim here was to study the effects of a cell-permeant peptide from the Cx43 carboxyl-terminus (CT) on scarring and regeneration following cutaneous injury.

MATERIALS & METHODS

The effects of Cx43 CT peptide were studied in mouse and pig models of cutaneous injury. The parameters assessed included neutrophil density, wound closure, granulation, regeneration and skin tensile properties.

RESULTS

Cx43 CT-peptide prompted decreases in area of scar progenitor tissue and promoted restoration of dermal histoarchitecture and mechanical strength following wounding of skin. These changes in healing were preceded by peptide-induced reduction in inflammatory neutrophil infiltration and alterations in the organization of epidermal Cx43, including increased connexon aggregation.

CONCLUSION

Cx43 CT peptide promotes regenerative healing of cutaneous wounds and may have applications in tissues other than skin, including heart, cornea and spinal cord.

A porcine model of full-thickness burn, excision and skin autografting

Acute burn wounds often require early excision and adequate coverage to prevent further hypothermia, protein and fluid losses, and the risk of infection. Meshed autologous skin grafts are generally regarded as the standard treatment for extensive full-thickness burns. Graft take and rate of wound healing, however, depend on several endogenous factors. This paper describes a standardized reproducible porcine model of burn and skin grafting which can be used to study the effects of topical treatments on graft take and re-epithelialization. Procedures provide a protocol for successful porcine burn wound experiments with special focus on pre-operative care, anesthesia, burn allocation, excision and grafting, postoperative treatment, dressing application, and specimen collection. Selected outcome measurements include percent area of wound closure by planimetry, wound assessment using a clinical assessment scale, and histological scoring. The use of this standardized model provides burn researchers with a valuable tool for the comparison of different topical drug treatments and dressing materials in a setting that closely mimics clinical reality.