Healing Of Partial-thickness Wounds Research Articles

A Standardized Porcine Model for Partial-Thickness Wound Healing Studies: Design, Characterization, Model Validation, and Histological Insights.

Wound healing is a complex process that is still not fully understood despite extensive research. To address this, we aimed to design and characterize a standardized porcine model for the evaluation of wound healing, dressings, cell therapies, and pharmaceutical agents. Using a standardized approach, we examined the wound healing process in 1.2 mm-deep dermatome wounds at defined positions in 11 female pigs. Unlike previous studies that have only described/analyzed selected punch biopsies, we performed and described histological analyses along the complete wound length using quantitative morphometric methods. All animals remained fully healthy following surgery and showed no signs of infection. Our histopathological evaluation using a predetermined grading score and quantitative manual morphometry demonstrated the impact of different tissue sampling methods, sampling sites, and residual dermis thickness on wound healing. Our study presents a reproducible model for wound healing evaluation and demonstrates the usefulness of porcine models for assessing dermal and epidermal wound healing. The use of histological analyses over the complete wound length provides advantages over previous studies, leading to the possibility of a deeper understanding of the wound healing process. This model could potentially facilitate future research on novel wound dressings and local wound healing therapies.

Comparison of the Effectiveness of Lyophilized Amniotic Membranes in the Partial Thickness Wound Healing Process in Mus musculus

Background: Currently, tulle or gentamicin ointment is generally used to prevent wound infections in wound care. Human amniotic membrane has been used in medical fields such as wound care. So far, there is no comparative evidence of the effectiveness of each ingredient. This study aimed to compare the effectiveness of lyophilized amniotic membrane, tulle, and 0.1% gentamicin ointment in the wound healing process. partial thickness on Mus musculus clinically and histologically.
 Methods: This type of research is experimental with a post-test-only control group design. There were 24 rats divided into each group. This research was conducted at the anatomical pathology laboratory, Faculty of Medicine, Universitas Andalas, and INA lab in July - September 2023 using rats (Mus musculus), which were divided into 3 treatment groups and one control group.
 Results: Clinically, lyophilized amniotic membrane, 0.1% gentamicin ointment, and tulle provided better results than controls regarding erythema variables. Histologically, the results showed that the lyophilized amniotic membrane group had the thinnest epidermis and dermis, as well as better histological scores for granulation, fibroblasts, and collagen than the 0.1% gentamicin ointment, tulle, and control groups. In this study, significant differences in effectiveness were found in terms of erythema, skin thickness, granulation, fibroblast, and collagen histological scores, with better results in the lyophilized amniotic membrane group.
 Conclusion: Clinically, lyophilized amniotic membrane, tulle, and 0.1% gentamicin ointment were more effective than controls for wound treatment due to faster reduction in erythema. However, histologically, the lyophilized amniotic membrane was proven to be more effective than tulle, 0.1% gentamicin ointment, and control in terms of epidermis and dermis thickness, granulation level, fibroblasts, and collagen.

Antibacterial and wound healing analysis of gelatin/zeolite scaffolds

In this article, gelatin/copper activated faujasites (CAF) composite scaffolds were fabricated by lyophilisation technique for promoting partial thickness wound healing. The optimised scaffold with 0.5% (w/w) of CAF, G (0.5%), demonstrated pore size in the range of 10–350μm. Agar disc diffusion tests verified the antibacterial role of G (0.5%) and further supported that bacterial lysis was due to copper released from the core of CAF embedded in the gelatin matrix. The change in morphology of bacteria as a function of CAF content in gelatin scaffold was studied using SEM analysis. The confocal images revealed the increase in mortality rate of bacteria with increase in concentration of incorporated CAF in gelatin matrix. Proficient oxygen supply to needy cells is a continuing hurdle faced by tissue engineering scaffolds. The dissolved oxygen measurements revealed that CAF embedded in the scaffold were capable of increasing oxygen supply and thereby promote cell proliferation. Also, G (0.5%) exhibited highest cell viability on NIH 3T3 fibroblast cells which was mainly attributed to the highly porous architecture and its ability to enhance oxygen supply to cells. In vivo studies conducted on Sprague Dawley rats revealed the ability of G (0.5%) to promote skin regeneration in 20 days. Thus, the obtained data suggest that G (0.5%) is an ideal candidate for wound healing applications.

A closer examination of atraumatic dressings for optimal healing

The concept that undisturbed wound healing, optimised by dressing choice, improves wound outcomes has become a focal point of consideration when evaluating wound management regimens in recent years. However, little evidence exists related to wound contact layers and the potential detrimental effects of the intimate contact with the wound bed. The aim of this study was to evaluate the effects of atraumatic wound contact dressings on the healing of partial-thickness wounds in comparison to untreated air-exposed wounds. Using an in vivo porcine wound model the handling properties of each dressing in terms of adhesion were analysed. Methods of wound characterisation included histological analysis of granulation tissue formation and epithelialisation and this was correlated with various clinical observations. Differences were found between dressings in terms of adherence to the wound bed and surrounding skin, capacity to retain wound exudates and enhancement of healing.

Interactions of Methicillin Resistant Staphylococcus aureus USA300 and Pseudomonas aeruginosa in Polymicrobial Wound Infection

Understanding the pathology resulting from Staphylococcus aureus and Pseudomonas aeruginosa polymicrobial wound infections is of great importance due to their ubiquitous nature, increasing prevalence, growing resistance to antimicrobial agents, and ability to delay healing. Methicillin-resistant S. aureus USA300 is the leading cause of community-associated bacterial infections resulting in increased morbidity and mortality. We utilized a well-established porcine partial thickness wound healing model to study the synergistic effects of USA300 and P. aeruginosa on wound healing. Wound re-epithelialization was significantly delayed by mixed-species biofilms through suppression of keratinocyte growth factor 1. Pseudomonas showed an inhibitory effect on USA300 growth in vitro while both species co-existed in cutaneous wounds in vivo. Polymicrobial wound infection in the presence of P. aeruginosa resulted in induced expression of USA300 virulence factors Panton-Valentine leukocidin and α-hemolysin. These results provide evidence for the interaction of bacterial species within mixed-species biofilms in vivo and for the first time, the contribution of virulence factors to the severity of polymicrobial wound infections.

Sodium carboxymethylcellulose scaffolds and their physicochemical effects on partial thickness wound healing

This study investigated critical physicochemical attributes of low (LV), medium (MV) and high molecular weight (HV) sodium carboxymethylcellulose (SCMC) scaffolds in partial thickness wound healing. SCMC scaffolds were prepared by solvent-evaporation technique. Their in vitro erosion, moisture affinity, morphology, tensile strength, polymer molecular weight and carboxymethyl substitution, and in vivo wound healing profiles were determined. Inferring from rat wound size, re-epithelialization and histological profiles, wound healing progressed with HV scaffold>LV–MV scaffold>control with no scaffold. The transepidermal water loss (TEWL) from wound of rats treated by control>HV scaffold>LV–MV scaffold. HV scaffold had the highest tensile strength of all matrices and was resistant to erosion in simulated wound fluid. In spite of constituting small nanopores, it afforded a substantial TEWL than MV and LV scaffolds from wound across an intact matrix through its low moisture affinity characteristics. The HV scaffold can protect moisture loss without its excessive accumulation at wound bed which hindered re-epithelialization process. Regulation of transepidermal water movement and wound healing by scaffolds was governed by SCMC molecular weight instead of its carboxymethyl substitution degree or matrix pore size distribution, with large molecular weight HV preferred over lower molecular weight samples.

A serum amyloid P‐binding hydrogel speeds healing of partial thickness wounds in pigs

During wound healing, some circulating monocytes enter the wound, differentiate into fibroblast-like cells called fibrocytes, and appear to then further differentiate into myofibroblasts, cells that play a key role in collagen deposition, cytokine release, and wound contraction. The differentiation of monocytes into fibrocytes is inhibited by the serum protein serum amyloid P (SAP). Depleting SAP at a wound site thus might speed wound healing. SAP binds to some types of agarose in the presence of Ca(2+). We found that human SAP binds to an agarose with a K(D) of 7 x 10(-8) M and a B(max) of 2.1 microg SAP/mg wet weight agarose. Mixing this agarose 1 : 5 w/v with 30 microg/mL human SAP (the average SAP concentration in normal serum) in a buffer containing 2 mM Ca(2+) reduced the free SAP concentration to approximately 0.02 microg/mL, well below the concentration that inhibits fibrocyte differentiation. Compared with a hydrogel dressing and a foam dressing, dressings containing this agarose and Ca(2+) significantly increased the speed of wound healing in partial thickness wounds in pigs. This suggests that agarose/Ca(2+) dressings may be beneficial for wound healing in humans.

018 Role of the Receptor CXCR3 and its Ligand in Wound Healing

We find that the ELR-negative CXC chemokines, CXCL10 (IP-10) and CXCL11(IP-9), expressed during wound repair, with IP-9 being produced by redifferentiated keratinocyte. Immunohistochemical analysis for IP-9 on human full thickness wound tissues collected from day 5 confirmed that IP-9 is a wound response protein. We have shown in in vitro coculture systems that IP-9 can serve as an autocrine factor promoting motility in keratinocyte while limiting motility in dermal fibroblasts. These effects occur via modulation of the intracellular proteases calpain isoforms that regulate cell adhesion during motility. Thus, the function of these chemokines in vivo is not obvious. To probe this, we have explored wound repair in mice lacking the receptor for these ligands, CXCR3. Quantitative analysis of IP-9 expression in wounds of these mice collected from day 2 to day 20 showed a significant increase in IP-9 levels in CXCR3-/- mice compared to wild type, which is expected if receptor-mediated feedback attenuation is lost. Full and partial thickness wound healing experiments on these mice showed a significant delay in CXCR3-/- mice when compared to wild type. Histochemical analysis of tissues collected from both full and partial thickness wounds demonstrated differences in epithelialization, granulation tissue formation, and angiogenesis in CXCR3-/- mice when compared to wild type. Collagen, the major extracellular matrix protein organization were analyzed by trichrome and picrosirus red staining methods. We are also examining the effect of this lost receptor on promotility signaling from EGF receptors. These in vivo and in vitro studies confirm the pathophysiologic role of the chemokines IP-9 and IP-10 and their cognate receptor CXCR3 during wound repair.

A reproducible laser-wounded skin equivalent model to study the effects of aging in vitro.

Skin aging involves both chronological and photoaging processes. The effects of these processes are often overlapping and include changes in both the stratified epithelium and the fibroblast-rich dermis. Wound healing is frequently delayed with aging and can result in scarring. A skin equivalent model can be used to study the role of cells and the extracellular matrix in the process of wound healing. Current studies using this model employ a full-thickness wound placed atop a nonwounded dermis to mimic a partial-thickness wound. However, a true reproducible partial-thickness wound model has yet to be described. In this study, we investigated whether a laser-wounded skin equivalent would be a useful partial-thickness wound healing model. Three lasers were compared for the ability to generate a reproducible wound: an erbium-YAG, a high-powered excimer, and a low-powered excimer laser. Reepithelialization ability was tested using newborn and adult skin keratinocytes, adult esophageal keratinocytes, and cdk4-overexpressing newborn keratinocytes. Keratinocyte compartmentalization and basement membrane formation were assessed by immunofluorescence. The erbium-YAG and high-powered excimer laser cut reproducible wounds but left the remaining surface either discolored due to thermal damage and/or ragged; keratinocytes were unable to migrate into the wound area. The low-powered excimer laser cut reproducible wounds, leaving the cut surface intact and visibly unaltered; keratinocytes reepithelialized the wound in a collagenase-dependent manner within 3 days; and return of compartmentalization and basement membrane occurred within 14 days. The laser-wounded skin equivalent is an adjustable, reproducible partial-thickness wound model where keratinocyte biology akin to in vivo can be studied, and will be useful to study the effects of aging on wound healing.

An Octyl-2-Cyanoacrylate Formulation Speeds Healing of Partial-Thickness Wounds

BACKGROUND Occlusive dressings have been known to accelerate the rate of healing. Every year new dressings are being introduced in the marketplace. OBJECTIVE The purpose of this study was to evaluate the effect of a new octyl-2-cyanoacrylate liquid dressing as compared to two over-the-counter bandages on partial-thickness wounds. Performance parameters were epithelialization, erythema, scab formation, material adherence, hemostasis, and infection. METHOD Eight pigs with a total of 645 partial-thickness wounds were assigned to one of the following treatments: liquid dressing, standard bandage, hydrocolloid bandage, or untreated air exposed. RESULT The liquid bandage enhanced the rate of epithelialization and was the only treatment to provide complete hemostasis, reduced scab formation, and did not induce an irritant response (erythema) or infection. CONCLUSION The liquid bandage is an easy to use material that stops bleeding (instantaneous hemostasis) while enhancing healing of partial-thickness wounds.

Expression of Thrombomodulin and Consequences of Thrombomodulin Deficiency during Healing of Cutaneous Wounds

Thrombomodulin is a cell surface anticoagulant that is expressed by endothelial cells and epidermal keratinocytes. Using immunohistochemistry, we examined thrombomodulin expression during healing of partial-thickness wounds in human skin and full-thickness wounds in mouse skin. We also examined thrombomodulin expression and wound healing in heterozygous thrombomodulin-deficient mice, compound heterozygous mice that have <1% of normal thrombomodulin anticoagulant activity, and chimeric mice derived from homozygous thrombomodulin-deficient embryonic stem cells. In both human and murine wounds, thrombomodulin was absent in keratinocytes at the leading edge of the neoepidermis, but it was expressed strongly by stratifying keratinocytes within the neoepidermis. No differences in rate or extent of reepithelialization were observed between wild-type and thrombomodulin-deficient mice. In chimeric mice, both thrombomodulin-positive and thrombomodulin-negative keratinocytes were detected within the neoepidermis. Compared with wild-type mice, heterozygous and compound heterozygous thrombomodulin-deficient mice exhibited foci of increased collagen deposition in the wound matrix. These findings demonstrate that expression of thrombomodulin in keratinocytes is regulated during cutaneous wound healing. Severe deficiency of thrombomodulin anticoagulant activity does not appear to alter reepithelialization but may influence collagen production by fibroblasts in the wound matrix.

Effect of ultraviolet radiation—induced inflammation on epidermal wound healing

To examine the influence of ultraviolet radiation, a potent inducer of interleukin-1 and other growth factors, on the rate of epidermal migration, we used a porcine model of wound healing. Wounds were treated in one of the following treatment groups: (1) two minimal erythema doses of ultraviolet radiation once daily for 2 days before wounding, (2) two minimal erythema doses of ultraviolet radiation once daily for 2 days before wounding followed with continuous treatment until all wounds were 100% epithelized, (3) or no ultraviolet radiation treatment until healing was complete. Using a macroscopic salt-split technique, we examined epidermal specimens macroscopically for epithelialization. Treatment both before and after ultraviolet radiation significantly enhanced epithelialization when compared with non-ultraviolet radiation-treated control wounds. These experiments show that ultraviolet radiation treatment can augment the rate of healing of partial-thickness wounds.

Cultured Keratinocyte Sheets Enhanced Spontaneous Re-Epithelialization in a Dermal Explant Model of Partial-Thickness Wound Healing

An in vitro model for partial-thickness cutaneous wound healing is described in which the influence of variables present in vivo, such as blood-borne factors and inflammatory cells, is eliminated. Dermal sheets of porcine skin are maintained in culture at the air-liquid interface in serum-free medium, and re-epithelialization from the keratinocytes of the hair infundibula can be studied. Dermal sheets of different thicknesses harvested from various depths were first evaluated for viability and regenerative potential in serum-supplemented medium. Mid-dermal explants, 20/1000 inch thick, showed the greatest epithelial outgrowth from the appendigeal keratinocytes and the longest viability in vitro. Explants of this type were used in all subsequent experiments. The effects of growth factors on re-epithelialization of the explants were studied in a serum-free environment. Epidermal growth factor, cholera toxin, bombesin, and insulin-like growth factor alone and in various combinations were applied to the explant surface in aqueous solutions by micropipette. Outgrowth was assessed by computerized morphometric analysis (RS/1 program by BBN) at days four and eight. Among all factors tested, cholera toxin alone and in combination with insulin-like growth factor produced the greatest epithelial outgrowth. Nevertheless, topical applications of growth factors failed to induce complete re-epithelialization within the experimental time frame. In contrast, explants to which cultured human keratinocyte sheets were topically applied regenerated a confluent and regularly stratified epidermis within 6 d.

Effect of shock waves on the healing of partial-thickness wounds in piglets

During the last 20 years, the role of various physical factors in wound healing has been widely studied and recognized. With the use of shock waves for the treatment of urolithiasis, a new mechanical medium has been introduced into medicine. The influence of shock waves on the reepithelialization of partial-thickness wounds was studied in four Yorkshire piglets by a quantitative morphometric method. Wounds were inflicted either in intact skin (three pigs) or in skin irradiated with 1500 rads to achieve delayed healing. A significant enhancement in normal or delayed healing was found with low-dose treatment (10 SW at 14 kV). High-dose application of shock waves (100 SW at 18 kV) resulted in inhibition of the rate of reepithelialization of the wounds. Shock waves of intermediate energies were without effect. The stimulating effect of low-energy shock waves coincides with significantly increased vascularization of the upper dermis and thicker layer of the newly formed epithelial cells covering the wound.

A new porous polyetherurethane wound covering

A polyetherurethane (PEU) wound covering with non-interconnected micropores up to approximately 5 microns has been prepared by means of a phase inversion process. This highly elastic, very thin (15-20 microns), pliable wound covering showed good, immediate adherence to wet wound surfaces and high water vapor permeability, but was impermeable to bacteria. In guinea pigs epidermal wound healing of partial-thickness wounds under PEU wound coverings was accelerated compared with uncovered controls and an occlusive wound covering, OpSite. Water in liquid form or wound exudate could not leak through the PEU covering, but its high water vapor permeability induced concentration of the wound exudate into a jellylike clot layer, which apparently accelerated reepithelialization. The main conclusion from a clinical study on 20 donor sites was that the use of the PEU covering reduced pain, besides prevention of fluid retention. No differences in epithelialization were seen in comparison to tulle gras-treated wounds.

Comparison of an Occlusive and a Semi-occlusive Dressing and the Effect of the Wound Exudate upon Keratinocyte Proliferation

Three consecutive studies were performed in 58 patients evaluating the effect of occlusion on the healing of partial-thickness wounds. Mirror-image donor sites were covered with the occlusive hydrocolloid dressing (HCD) (DuoDerm) and compared to fine mesh gauze, and the HCD was subsequently compared to a semi-occlusive dressing of polyurethane film, (Op-site). In addition, partial-thickness burn wounds were covered with the HCD and the remaining burn wound was treated with silver sulfadiazine. The donor sites and burn wounds treated with HCD healed significantly faster than those covered with fine mesh gauze or silver sulfadiazine (p less than 0.001) and with less pain. The HCD and polyurethane film were equivalent. There were no clinical infections with the wounds that were occluded. The exudate collected beneath the DuoDerm and Op-site on donor sites was added to the tissue culture system and resulted in a modest increase in keratinocyte proliferation. However, the exudate from burn wounds under HCD resulted in a marked increase in cell proliferation (p less than 0.001).