THE PIG AS A MODEL FOR HUMAN WOUND HEALING

Pregnancy-specific glycoprotein 1 promotes wound closure in animal models

Recombinant human PSG1 administered intradermally at wound margins enhances skin wound healing in the mouse and pig, including in an acute diabetic mouse model. A highly significant effect on wound re-epithelialisation was observed in the pig, and PSG1 treatment of the human HaCaT keratinocyte cell line regulated wound healing-associated genes and enhanced scratch wound closure in cell monolayers in vitro. Clinical use of PSG1 might enhance closure of incisional and traumatic wounds and enhance re-epithelialisation of burn injuries.

Research progress on the role of fascia in skin wound healing

The skin, the human body's largest organ, is perpetually exposed to environmental factors, rendering it vulnerable to potential injuries. Fascia, a vital connective tissue that is extensively distributed throughout the body, fulfils multiple functions, including support, compartmentalization, and force transmission. The role of fascia in skin wound healing has recently attracted considerable attention. In addition to providing mechanical support, fascia significantly contributes to intercellular signalling and tissue repair, establishing itself as a crucial participant in wound healing. This review synthesises the latest advancements in fascia research and its implications for skin wound healing.

Differences in thickness of dermal layers in cranio-caudal anatomic locations in porcine skin wounds: Implications for wound healing studies

The use of the domesticated swine is important for advancing our understanding of healing in human skin due to the architectural similarities in their skin. In swine wound studies, skin thickness may play a role in healing due to the anatomical variation in the thickness of the different skin compartments, such as the dermis and subcutaneous fat, as well as the differences in anatomical location of the wounds. Here, the thickness of different skin compartments were measured in excisional wounds created in different anatomical locations along the cranio-caudal axis. Full-thickness, 2 cm diameter circular excisions were created on the dorsal paravertebral area of pigs. Thickness of the dermal and adipose layers of excised tissues at day 3 post-excision were measured in fixed H&E sections. Wound re-epithelialization was measured on excised day 10 wounds. A significant difference in skin thickness between the cranial wounds compared to the caudal wounds is noted in skin excised down to the landmark of the subcutaneous fascial plane. There were also significant differences in the thickness of the dermal and fat layers. Skin thickness, and the variations of the dermal and fat compartments, and locations of wounds should be taken into consideration in porcine wound studies as they may contribute to alterations in healing in the different locations.

Inter-species differences in wound-healing rate: a comparative study involving primates and rodents

Injuries, which affect survival and biological functioning, are common in the animal kingdom. This study systematically investigated whether the slow wound healing observed in humans is a unique characteristic within the primate order. First, we found no significant difference in wound-healing rates between baboons under experimental conditions and those in their natural environment (0.613 mm d-1). Second, comparisons among four non-human primates (velvet monkeys, Sykes' monkeys, baboons and chimpanzees) revealed no significant differences in wound-healing rates. Furthermore, these rates showed no significant differences compared to those observed in rodents, suggesting a potential commonality in wound-healing rates across diverse animal species. In contrast, human wound-healing rates were found to be markedly slower (0.25 mm d-1), approximately three times slower than those observed in non-human primates. This finding indicates that the slow wound healing observed in humans is not a common characteristic among primate order and highlights the possibility of evolutionary adaptations in humans. Understanding these inter-species differences in wound-healing rates may provide valuable insights into the evolutionary implications of wound healing. This study also underscores the need for further research into the biological processes underlying wound healing in various species.

Novel Robust Needle Tip Design Enables Needle Reuse and Reduced Skin Trauma in Combination With Autoinjector Needle Shields

BACKGROUND

Pen needles and autoinjectors are necessary for millions of patients needing injectable drug treatment but pose economic and environmental burdens. A durable device with a multiuse needle could reduce cost and improve user experience. This study explores a novel robust needle tip (EXP) designed for multiple uses and durability against hooking.

METHOD

Needle robustness was investigated through a structural analysis. Furthermore, EXP and control needles (NF30, NF28) were evaluated in an in-vivo porcine model as pen needles or embedded in autoinjectors to study the resulting increase in skin blood perfusion (SBP). The SBP was assessed by laser speckle contrast analysis (LASCA) of 192 randomized and blinded needle insertions.

RESULTS

Forming a 33 µm hook against a hard surface requires 0.92 N for the NF30 control needle and 5.38 N for EXP. The EXP did not induce more tissue trauma than the NF30. There was a positive relation between needle diameter and SBP (P < .05). Furthermore, the presence of an autoinjector shield and applied force of 10 N was found to significantly reduce SBP for worn EXP needles (P < .05) compared to insertions without autoinjector shield.

CONCLUSIONS

The investigated robust needle EXP is on par with the single-use needle NF30 in terms of tissue trauma, which is further reduced by combining the needle with a needle shield. These results should encourage the innovation and development of durable, reusable injection systems with pharmacoeconomic and environmental value and a simplified and enhanced user experience for patients.

Protection with a collagen wound matrix containing polyhexamethylene biguanide supports innate wound healing in biofilm-infected porcine wounds

Over 90% of chronic wounds have biofilm infections, making the need for inhibiting reformation of biofilm post-debridement paramount to support progression through the normal phases of wound healing. Herein, we describe a porcine wound model infected with methicillin-resistant Staphylococcus aureus (MRSA) and examine the ability of an antimicrobial barrier composed of native type I collagen and polyhexamethylene biguanide (PCMP) to serve as a barrier to protect wounds and support progression through the innate wound healing cascade. Wounds were inoculated with MRSA and allowed to form a biofilm for 72 h, subjected to standard of care sharp debridement, then either left untreated or received PCMP for 5, 10, 15 or 20 days. Wounds were assessed for bioburden, wound closure and expression of genes related to wound healing. Wounds treated with PCMP exhibited statistically lower MRSA levels compared to untreated controls and achieved 90% closure by 2 weeks of treatment. Gene expression analysis demonstrated that by reducing bacterial load, wounds progressed through the innate wound healing cascade, while untreated wounds exhibited a dampening of the immune response. Additionally, for randomly assigned wounds, PCMP was not reapplied at dressing changes to assess the impact of inconsistent wound protection. At all timepoints, a resurgence in bioburden was observed following removal of PCMP if the wounds had not fully closed. This study highlights the value of PCMP as an antimicrobial barrier and the importance of protecting wounds through closure and resolution.

Development of a porcine model of skin and soft-tissue infection caused by Staphylococcus aureus, including methicillin-resistant strains suitable for testing topical antimicrobial agents

BACKGROUND

In view of the ever-increasing representation of Staphylococcus spp. strains resistant to various antibiotics, the development of in vivo models for evaluation of novel antimicrobials is of utmost importance.

METHODS

In this article, we describe the development of a fully immunocompetent porcine model of extensive skin and soft tissue damage suitable for testing topical antimicrobial agents that matches the real clinical situation. The model was developed in three consecutive stages with protocols for each stage amended based on the results of the previous one.

RESULTS

In the final model, 10 excisions of the skin and underlying soft tissue were created in each pig under general anesthesia, with additional incisions to the fascia performed at the base of the defects and immediately inoculated with Staphylococcus aureus suspension. One pig was not inoculated and used as the negative control. Subsequently, the bandages were changed on Days 4, 8, 11, and 15. At these time points, a filter paper imprint technique (FPIT) was made from each wound for semi-quantitative microbiological evaluation. Tissue samples from the base of the wound together with the adjacent intact tissue of three randomly selected defects of each pig were taken for microbiological, histopathological, and molecular-biological examination. The infection with the inoculated S. aureus strains was sufficient during the whole experiment as confirmed by both FPIT and from tissue samples. The dynamics of the inflammatory markers and clinical signs of infection are also described.

CONCLUSIONS

A successfully developed porcine model is suitable for in vivo testing of novel short-acting topical antimicrobial agents.

Harnessing Manuka Honey: A Natural Remedy for Accelerated Burn Wound Healing in a Porcine Model

Backgrounds: Burn injuries present significant medical challenges due to their complexity in healing and potential for severe scarring. This study evaluates the efficacy of Manuka honey in accelerating burn wound healing compared to conventional antibiotic ointments. Methods: Using a porcine model resembling human skin, nine Landrace breed female pigs with standardized deep dermal burns were treated with either Manuka honey in alginate or a combination of antibiotic ointments. Wound healing was assessed through macroscopic evaluation, a histopathological analysis, and immunohistochemical staining over a 60-day period. Results: Our findings indicate that the Manuka honey treatment was associated with significantly increased collagen density in the treated wounds compared to the control group (p < 0.05). The immunohistochemical analysis revealed lower macrophage activity (Iba1 staining) and a reduction in Ki67 expression on days 10 and 17 in the Manuka honey group, suggesting a more rapid transition toward tissue remodeling. The quantitative analysis showed a trend toward delayed epithelialization and increased inflammation in the control group, while wounds treated with Manuka honey exhibited faster reepithelialization and improved epidermal regeneration. However, additional studies are required to further assess collagen fiber organization and overall dermal architecture. Conclusions: These findings support the potential of Manuka honey as a beneficial treatment for burn wound healing, with evidence of enhanced reepithelialization and collagen deposition. Further research, including clinical trials, is necessary to fully elucidate its role in clinical practice and optimize treatment protocols.

Comprehensive transcriptomic analysis of myostatin-knockout pigs: insights into muscle growth and lipid metabolism

Pigs are a vital source of protein worldwide, contributing approximately 43% of global meat production. Recent genetic advancements in the myostatin (MSTN) gene have facilitated the development of double-muscling traits in livestock. In this study, we investigate the transcriptomic profiles of second-generation MSTN-knockout (MSTN-/-) pigs, generated through CRISPR/Cas9 gene editing and somatic cell nuclear transfer (SCNT). Using RNA sequencing, we compared the transcriptomic landscapes of muscle tissues from MSTN-/- pigs and wild-type (WT) counterparts. The sequencing yielded an average unique read mapping rate of 86.7% to the Sus scrofa reference genome. Our analysis revealed 15,142 differentially expressed genes (DEGs), including 121 novel genes, with 2554 genes upregulated and 1629 downregulated in the MSTN-/- group relative to the wild-type group. Notable transcriptomic changes were identified in genes associated with muscle development, lipid metabolism, and other physiological processes. These findings provide valuable insights into the molecular consequences of MSTN inactivation, with potential applications in the optimization of livestock breeding and advancements in biomedical research.

CD163, a novel receptor for TNF, was revealed in situ by proximity ligation assay

Cytokine therapy utilizes cytokines to enhance the immune system to fight diseases. These strategies rely on advanced knowledge, including the communication between cytokines and their receptors. In situ, cytokine-receptor interactions are typically analyzed by co-localization using immunolabeling. Our study compared co-localization using the Proximity Ligation Assay (PLA), a recently developed in situ protein-protein interaction technique. In an inflamed porcine lung model, we demonstrated the efficacy of PLA in detecting interactions between tumor necrosis factor (TNF) and its receptors TNFR1 and TNFR2. Additionally, the CD163 receptor was identified as a novel partner of TNF. Furthermore, the combination of immunolabeling and PLA offered additional insights, particularly, the internalization of TNF following its binding with CD163 in macrophages. Our work focused on in situ interactions of TNF with macrophages TNF receptors and suggested exciting perspectives for further understanding and application of cytokine-based therapies.

Development of an experimental heterogeneous burn wound model

BACKGROUND

Many research-based burn models rely on creating homogenous burns that are subsequently studied and treated. However, the majority of burn wounds sustained - and in particular those that are combat-related - are heterogeneous in nature, with varying degrees of severity intermixed throughout the entire wound, creating a complex debridement and overall treatment plan. The purpose of this study was to develop a clinically relevant heterogeneous porcine burn wound model.

MATERIALS AND METHODS

This study consisted of 3 anesthetized pigs with up to 6 heterogeneous 10 cm x 10 cm burn wounds. The burns were created using a thermocouple device with a square plate (5 cm x 5 cm) heated to 100 °C applied to the skin at constant pressure. The device was applied for a duration between 2-20 s for each burn segment to create burns of varying severity (superficial, partial-thickness, and full-thickness). Each heterogeneous burn wound consisted of 4 separate 5 cm x 5 cm burns, each with different and randomized burn times. Macroscopic images of the burns were obtained on days 0, 1, and 3. A punch biopsy was collected from each burn segment (1 of each depth) to determine the burn depth on day 0. On day 3, after euthanasia, all of the burns were harvested to give a cross-sectional view of the burn.

RESULTS

Histology demonstrated that heterogeneous burns were created and burn progression was evident during the 3-day follow-up time. The depth of the burn wound significantly correlated with the burn time. By day 3, the 20-second burn wound had the deepest depth at 1003 ± 67 µm while the 2-second burn wound had the shallowest depth of burn at 258 ± 19 µm. Burn heterogeneity was also demonstrated with laser speckle image analysis. By day 3, the superficial blood flow for 20, 15, 12, 9, and 6 s burn times was below 85 AU. The 2 s burn mean flux (138 ± 48 AU) was noticeably different from other groups and well above the intact skin values (102 ± 4 AU). It was also shown that on day 3, at least 1 burn for each burn time resulted in identifiable infection via macroscopic imaging.

CONCLUSIONS

The heterogeneity of burn wounds creates a clinical challenge. This model will help to create burns that are more similar to the heterogeneous burn wounds that are seen in clinical practice and will help further research efforts in treating burns.

Peripherally mediated opioid combination therapy in mouse and pig

The concomitant epidemics of chronic pain and opioid misuse in the United States have led to a call for novel analgesics with limited abuse potential. Previously, we have shown that co-delivery of a novel combination targeting both μ- and δ-opioid receptors in the peripheral and central nervous systems can produce synergistic analgesia. Loperamide, a peripherally restricted μ-opioid agonist, and oxymorphindole, a δ-opioid receptor partial agonist, synergize in multiple mouse models of hyperalgesia. We predicted this effect would generalize across species and therefore assessed this combination for analgesic synergy in a mouse model of post-incisional hypersensitivity. In mice, oxymorphindole and loperamide displayed significant analgesic synergy. Similar synergy was observed with N-benzyl-oxymorphindole and loperamide. In cross-bred pigs, we compared the analgesic effects of either morphine alone or the combination of oxymorphindole and loperamide or the combination of N-benzyl-oxymorphindole and loperamide. Both combinations showed increased potency as compared to morphine sulfate and effectively reduced hypersensitivity following injury without side effects. From these data we conclude that the combination of oxymorphindole and loperamide or the combination of N-benzyl-oxymorphindole and loperamide reverse incisional hyperalgesia, likely by acting in the periphery, in a large animal model without adverse effects on respiration or heart rate. PERSPECTIVE: This article presents novel opioid combinations, the μ-opioid agonist loperamide with a δ-opioid agonist, either oxymorphindole (OMI) or N-benzyl-oxymorphindole (BOMI), that relieve pain in mice and pigs without adverse side effects. These therapies could help clinicians manage pain in patients while reducing overall opioid burden and limiting side effects.

Design and validation of a preclinical model for oral commissure and lower eyelid thermal injury

INTRODUCTION

Oral commissure stenosis and lower eyelid ectropion from burns are functionally impairing and challenging to treat. Evaluation of various treatment modalities is limited by a lack of preclinical models. Described is a method for inducing controlled, titratable oral commissure and lower eyelid burns in swine for future treatment research.

METHODS

Burn wounds 3 cm in diameter were applied to the lower eyelid and oral commissure of seven anesthetized Yorkshire swine for 10, 15, 20, or 30 s at 100 °C with a custom designed thermocouple-controlled burn device and observed for 3, 30, or 90 days. Tissue underwent laser speckle imaging (LSI) to assess vascular perfusion and histologic analysis after harvest. Statistical comparisons were calculated using Wilcoxon rank-sum tests.

RESULTS

Subdermal extension was noted in oral commissure and lower eyelid burns with contact time of 20 s or greater. Wound area progressively contracted from post-operative day (POD) 0 to 90 in both sites, but this was not statistically significant based on contact time or burn site (p > 0.20). Burns of 20-30 s demonstrated increased neutrophil influx for oral commissure injuries (p < 0.01) and leukocyte and macrophage influx for lower eyelid injuries (p = 0.02). Degree of vascular congestion increased with 20-30 second burns in both the oral commissure (p = 0.015) and lower eyelid (p = 0.04). Normalized LSI readings showed increased speckle size in both oral commissure (4.0-fold increase, p < 0.01) and lower eyelid (3.2-fold increase, p < 0.01) burns on POD 90 compared to pre-injury. No change in oral or ocular function was noted in any of the groups (p = 0.96).

CONCLUSION

Oral commissure and lower eyelid burns create scars which may be modified by burn duration. This model may evaluate a therapeutic's ability to limit functional impairment from burns.

Pig Model to Test Tissue Engineered Skin

Tissue engineering of skin is a field with high research activities and major importance for wound healing, especially following burn injuries. Animal models enable to test tissue engineered skin as well as different types of cells in a realistic setting. Although there are several challenges in working with pigs, it is a good model because of its similarity to the human skin and a comparable wound regeneration. Here, we explain our routinely used methods for using pig models to test tissue engineered skin in burn injuries.

Transplantation of Autologous Dermo-Epidermal Skin Substitutes in a Pig Model

Due to its similarity of skin anatomy and physiology, the pig appears to be a well-suited animal model for pre-clinical studies of skin analogue transplantations. The choice of the location of the skin defect and appropriate post-operative measures are essential for the protection of the transplanted graft. This protocol describes in detail a porcine skin transplantation model including peri- and postoperative measures taken to improve and refine the studies outcome.

The Wound Reporting in Animal and Human Preclinical Studies (WRAHPS) Guidelines

Preclinical studies for wound healing disorders are an essential step in translating discoveries into therapies. Also, they are an integral component of initial safety screening and gaining mechanistic insights using an in vivo approach. Given the complexity of the wound healing process, existing guidelines for animal testing do not capture key information due to the inevitable variability in experimental design. Variations in study interpretation are increased by complexities associated with wound aetiology, wounding procedure, multiple treatment conditions, wound assessment, and analysis, as well as lack of acknowledgement of limitation of the model used. Yet, no standards exist to guide reporting crucial experimental information required to interpret results in translational studies of wound healing. Consistency in reporting allows transparency, comparative, and meta-analysis studies and avoids repetition and redundancy. Therefore, there is a critical and unmet need to standardise reporting for preclinical wound studies. To aid in reporting experimental conditions, The Wound Reporting in Animal and Human Preclinical Studies (WRAHPS) Guidelines have now been created by the authors working with the Wound Care Collaborative Community (WCCC) GAPS group to provide a checklist and reporting template for the most frequently used preclinical models in support of development for human clinical trials for wound healing disorders. It is anticipated that the WRAHPS Guidelines will standardise comprehensive methods for reporting in scientific manuscripts and the wound healing field overall. This article is not intended to address regulatory requirements but is intended to provide general guidelines on important scientific considerations for such studies.

Jet injection through microneedles for large volume subcutaneous delivery

Subcutaneous (SC) drug delivery offers several advantages over intravenous (IV) delivery including: self-administration, improved patient experience, and reduced treatment costs. Unfortunately, each SC delivery is currently limited to ∼ 2.25 mL with IV administration required when the delivery volume exceeds this value. In this work, we explore a new technique for large volume subcutaneous drug delivery that uses microneedles to break through the epidermis then forms the liquid drug into many small jets that penetrate past the ends of the microneedles and into the subcutaneous (or muscle) tissue. By performing multiple simultaneous injections, this delivery approach avoids the volume limitations of SC delivery, and thus may be able to greatly increase the volume we can deliver to this space. Here, we present a novel multi-jet prototype that forms seven simultaneous jets through 30G needles that have been shortened to have an exposed length of just ∼ 1mm. The jet speed, shape, and volume of jets formed through these microneedles are measured to assess the consistency of jet production through the microneedles. We then perform jet injections of volumes up to 3.9 mL into ex vivo porcine tissue. The results demonstrate the successful delivery (>95 %) of 3.9 mL in just 0.3 s using jet injection performed through microneedles. This volume is almost double the maximum volume of current autoinjectors and the perceived limit for subcutaneous injection (2.25 mL). We also find that jet speeds of 70 m/s and below do not achieve complete delivery of 3.9 mL with our prototype system, and that the addition of microneedles leads to more consistent large volume delivery than equivalent needle-free injections. These results demonstrate the promise of multi-jet injection through microneedles to accommodate volumes much greater than current autoinjectors, and thus potentially allow patient self-administration in many more delivery applications.

The efficacy of a nitric oxide-releasing formulation on nares isolated Methicillin-Resistant Staphylococcus aureus in porcine wound infection model

Background

The colonization of Staphylococcus aureus (SA) acquired in nosocomial infections may develop acute and chronic infections such as Methicillin-Resistant Staphylococcus aureus (MRSA) in the nose. As a commensal microorganism with the ability to form a biofilm, SA can dwell on the skin, nostrils, throat, perineum, and axillae of healthy humans. Nitric oxide (NO) is an unstable gas with various molecular functions and has antimicrobial properties which are converted into many potential treatments.

Methods

Methicillin-Resistant Staphylococcus aureus MRSA BAA1686 isolated from nasal infection was used in a porcine wound infection model. Deep partial-thickness wounds (10mm x 7mm x 0.5mm) were made on three animals using a specialized electrokeratome. All wounds were inoculated and then covered with polyurethane film dressings for biofilm formation. After 48 hours, three wounds were recovered from each animal for baseline enumeration. The remaining wounds were randomly assigned to six treatment groups and treated once daily. The treatment groups are as follows: NO topical ointments concentrations of 0.3, 0.9 and 1.8%, Vehicle Ointment, Mupirocin 2%, and Untreated Control. Microbiological recoveries were conducted on day 4 and day 7.

Results

The greatest efficacy observed from the NO formulations against MRSA BAA1686 was the 1.8% concentration. This agent was able to reduce more than 99% of bacterial counts when compared to Baseline, Vehicle Ointment, and Untreated Control wounds on both assessment days. Mupirocin 2% was the overall best treatment against MRSA BAA1686 on both assessment days, with a significant reduction (p ≤ 0.05) of 4.70 ± 0.13 Log CFU/mL from day 4 to day 7.

Conclusions

Overall, the positive control Mupirocin 2% was the most effective in eliminating MRSA BAA1686 throughout the study. This experiment demonstrated a downward trend from the highest concentration of NO topical ointment formulations to the lowest concentrations on both assessment days (0.3% - 1.8%). Out of all NO topical ointments, the highest concentration (1.8%) was the most effective with the potential to be an alternative treatment against a MRSA nasal strain biofilm.

A microenvironment-modulating dressing with proliferative degradants for the healing of diabetic wounds

Diabetic wounds are usually entangled in a disorganized and self-perpetuating microenvironment and accompanied by a prolonged delay in tissue repair. Sustained and coordinated microenvironment regulation and tissue regeneration are key to the healing process of diabetic wounds, yet they continue to pose a formidable challenge. Here we report a rational double-layered dressing design based on chitosan and a degradable conjugated polymer polydiacetylene, poly(deca-4,6-diynedioic acid) (PDDA), that can meet this intricate requirement. With an alternating ene-yne backbone, PDDA degrades when reacting with various types of reactive oxygen species (ROS), and more importantly, generates proliferative succinic acid as a major degradant. Inheriting from PDDA, the developed PDDA-chitosan double layer dressing (PCD) can eliminate ROS in the microenvironment of diabetic wounds, alleviate inflammation, and downregulate gene expression of innate immune receptors. PCD degradation also triggers simultaneous release of succinic acid in a sustainable manner, enabling long-term promotion on tissue regeneration. We have validated the biocompatibility and excellent performance of PCD in expediting the wound healing on both diabetic mouse and porcine models, which underscores the significant translational potential of this microenvironment-modulating, growth-promoting wound dressing in diabetic wounds care.

The Dreaded 3-Minute Wait: Does It Really Prevent Operating Room Fires? The IGNITE Trial

INTRODUCTION

Operating room fires can have devastating consequences and as such must be prevented. There exists a paucity of literature requiring further elucidation regarding manufacturer recommendations of a predefined waiting period prior to patient draping after using alcohol-based surgical antiseptics, in order to reduce the risk of operating room fires.

METHODS

This was further investigated by exposing two common alcohol-based surgical antiseptics to electrosurgery and open flames at various power settings and time intervals in an ex vivo porcine model. The simulated surgical site was prepped following manufacturer recommendations and exposed to monopolar electrosurgery at low and high power, using both PURE CUT and COAGULATION modes, and open flame, at 15-s increments after application.

RESULTS

While using PURE CUT mode at both low and high power, no ignition was observed on hairless surgical sites prepped with ChloraPrep® at any time point. However, use of COAGULATION mode at both low and high powers resulted in ignition consistently out to 1-min post-application. Additionally, if the prepped area subjectively appeared wet, especially with pooling of the antiseptic, both COAGULATION mode and open flame caused ignition. Dry time was found to be about 59 s for both prep solutions. It was also observed that the amount of pressure directly correlated with the amount of prep dispersed and increased dry times.

CONCLUSION

In conclusion, our data suggest an average dry time of less than 1-min, with ignition only observed when the antiseptic was visibly wet. Ignition did not occur on hairless skin with electrocautery on CUT mode using ChloraPrep at any time point. Additionally, ignition on hair-bearing skin was not observed past 3 min, with current manufacturer recommendations stating 1 h wait time for hair-bearing skin. Arbitrarily waiting a specific predetermined dry time until patient draping, as recommended by the manufacturers, may be unnecessary and lead to hours' worth of time wasted each year. Ongoing research will further investigate the utility of drying the antiseptic after application and its affect on not only preventing ignition but also antimicrobial efficacy.

Coblation Versus Surgical Debridement Against MRSA Infection in Wounds With Shrapnel: A Preliminary Study

INTRODUCTION

Debridement plays a critical role in wound management. In addition to removing necrotic tissue, debridement can eliminate bacteria frequently harbored within the tissue. This study evaluated a novel debridement method that uses plasma-based radiofrequency technology to remove tissue and bacteria. Coblation is a technology that uses radiofrequency energy to excite the electrolytes in a conductive medium, such as saline, to create a precisely focused plasma. This plasma field contains highly energized particles that possess sufficient energy to break tissue molecular bonds, causing the tissue to dissolve at relatively low temperatures (typically 40 °C to 70 °C).

MATERIALS AND METHODS

Eighteen deep dermal wounds measuring 22 mm × 22 mm × 3 mm deep were created on pigs. Wounds were inoculated with methicillin-resistant Staphylococcus aureus USA300 (MRSA USA300) in combination with shrapnel and then covered with a polyurethane dressing for 24 hours. Wounds were then randomly assigned to one of the 3 treatment groups: (1) Coblation, (2) surgical debridement, and (3) no debridement. Wounds were biopsied on days 0, 5, 9, and 12, and specimens were processed for MRSA counts using selective media. Statistical analysis was performed using IBM SPSS statistics 27 using one-way ANOVA.

RESULTS

Comparison between coblation and surgical debridement showed a decrease in bacterial count in all assessment times. The lowest bacterial count in all assessment times was observed in wounds debrided with coblation showing a statistically significant (P ≤ .05) decrease in more than 2 Log CFU/g on days 0, 5, and 9 compared to no debridement. On day 12, coblation-debrided wounds exhibited 6.10 ± 0.22 Log CFU/g, and this value represents 99.99% of reduction compared with non-debrided wounds (P ≤ .05). More than 96% of reduction (P ≤ .05) resulted in wounds treated with coblation compared with surgically debrided.

CONCLUSIONS

Reducing MRSA bacterial infection counts, especially of biofilm-associated organisms, in combination with shrapnel may have important clinical implications, especially for the military personnel. Further research into the use of this technology in wound management is warranted.

Bacteriophage-cocktail hydrogel dressing to prevent multiple bacterial infections and heal diabetic ulcers in mice

Bacteriophage (phage) has been reported to reduce the bacterial infection in delayed-healing wounds and, as a result, aiding in the healing of said wounds. In this study we investigated whether the presence of phage itself could help repair delayed-healing wounds in diabetic mice. Three strains of phage that target Salmonella enterica, Escherichia coli, and Pseudomonas aeruginosa were used. To prevent the phage liquid from running off the wound, the mixture of phage (phage-cocktail) was encapsulated in a porous hydrogel dressing made with three-dimensional printing. The phage-cocktail dressing was tested for its phage preservation and release efficacy, bacterial reduction, cytotoxicity with 3T3 fibroblast, and performance in repairing a sterile full-thickness skin wound in diabetic mice. The phage-cocktail dressing released 1.7%-5.7% of the phages embedded in 24 h, and reduced between 37%-79% of the surface bacteria compared with the blank dressing (p <.05). The phage-cocktail dressing exhibited no sign of cytotoxicity after 3 days (p <.05). In vivo studies showed that 14 days after incision, the full-thickness wound treated with a phage-cocktail dressing had a higher wound healing ratio compared with the blank dressing and control (p <.01). Histological analysis showed that the structure of the skin layers in the group treated with phage-cocktail dressing was restored in an orderly fashion. Compared with the blank dressing and control, the repaired tissue in the phage-cocktail dressing group had new capillary vessels and no sign of inflammation in its dermis, and its epidermis had a higher degree of re-epithelialization (p <.05). The slow-released phage has demonstrated positive effects in repairing diabetic skin wounds.

Tissue expansion mitigates radiation-induced skin fibrosis in a porcine model

Tissue expansion (TE) is the primary method for breast reconstruction after mastectomy. In many cases, mastectomy patients undergo radiation treatment (XR). Radiation is known to induce skin fibrosis and is one of the main causes for complications during post-mastectomy breast reconstruction. TE, on the other hand, induces a pro-regenerative response that culminates in growth of new skin. However, the combined effect of XR and TE on skin mechanics is unknown. Here we used the porcine model of TE to study the effect of radiation on skin fibrosis through biaxial testing, histological analysis, and kinematic analysis of skin deformation over time. We found that XR leads to stiffening of skin compared to control based on a shift in the transition stretch (transition between a low stiffness and an exponential stress-strain region characteristic of collagenous tissue) and an increase in the high modulus (modulus computed with stress-stretch data past the transition point). The change in transition stretch can be explained by thicker, more aligned collagen fiber bundles measured in histology images. Skin subjected to both XR+TE showed similar microstructure to controls as well as similar biaxial response, suggesting that physiological remodeling of collagen induced by TE partially counteracts pro-fibrotic XR effects. Skin growth was indirectly assessed with a kinematic approach that quantified increase in permanent area changes without reduction in thickness, suggesting production of new tissue driven by TE even in the presence of radiation treatment. Future work will focus on the detailed biological mechanisms by which TE counteracts radiation induced fibrosis. STATEMENT OF SIGNIFICANCE: Breast cancer is the most prevalent in women and its treatment often results in total breast removal (mastectomy), followed by reconstruction using tissue expanders. Radiation, which is used in about a third of breast reconstruction cases, can lead to significant complications. The timing of radiation treatment remains controversial. Radiation is known to cause immediate skin damage and long-term fibrosis. Tissue expansion leads to a pro-regenerative response involving collagen remodeling. Here we show that tissue expansion immediately prior to radiation can reduce the level of radiation-induced fibrosis. Thus, we anticipate that this new evidence will open up new avenues of investigation into how the collagen remodeling and pro-regenerative effects of tissue expansion can be leverage to prevent radiation-induced fibrosis.

Comparative pharmacokinetics of porcine and human anti-influenza hemagglutinin monoclonal antibodies in outbred pigs and minipigs

Assessing the pharmacokinetics of monoclonal antibodies (mAbs) in relevant animal models is essential for designing improved formulations and developing mAb delivery platforms. We have established the pig, a large natural host animal for influenza with many similarities to humans, as a robust model for testing the therapeutic efficacy of anti-influenza mAbs and evaluating mAb delivery platforms. Here, we compared the pharmacokinetic characteristics of two anti-influenza hemagglutinin mAbs, human 2-12C and porcine pb27, in Göttingen minipigs and Landrace × Large White outbred pigs. Minipigs offer the advantage of a more stable weight, whereas outbred pigs are more readily available but exhibit rapid growth. Outbred pigs and minipigs showed similar pharmacokinetics and a similar porcine pb27 half-life (half-life of 15.7 days for outbred pigs and 16.6 days for minipigs). In contrast, the half-life of human 2-12C was more rapid in two of the minipigs but not in the outbred pigs, correlating with the development of antidrug antibodies in the two minipigs. Our results demonstrate that both outbred pigs and minipigs are appropriate models for pharmacokinetic studies and the evaluation of mAb delivery platforms, potentially bridging the gap between small animals and human trials.

ANTIMICROBIAL WOUND DRESSINGS FOR FULL-THICKNESS INFECTED BURN WOUNDS

ABSTRACT

Infection of wounds delays healing, increases treatment costs, and leads to major complications. Current methods to manage such infections include antibiotic ointments and antimicrobial wound dressings, both of which have significant drawbacks, including frequent reapplication and contribution to antimicrobial resistance. In this work, we developed wound dressings fabricated with a medical-grade polyurethane coating composed of natural plant secondary metabolites, cinnamaldehyde, and alpha-terpineol. Our wound dressings are easy to change and do not adhere to the wound bed. They kill gram-positive and -negative microbes in infected wounds due to the Food and Drug Administration-approved for human consumption components. The wound dressings were fabricated by dip coating. Antimicrobial efficacy was determined by quantifying the bacteria colonies after a 24 h of immersion. Wound healing and bacterial reduction were assessed in an in vivo full-thickness porcine burn model. Our antimicrobial wound dressings showed a > 5-log reduction (99.999%) of different gram-positive and gram-negative bacteria, while maintaining absorbency. In the in vivo porcine burn model, our wound dressings were superior to bacitracin in decreasing bacterial burden during daily changes, without interfering with wound healing. Additionally, the dressings had a significantly lower adhesion to the wound bed. Our antimicrobial wound dressings reduced the burden of clinically relevant bacteria more than commercial antimicrobial wound dressings. In an in vivo infected burn wound model, our coatings performed as well or better than bacitracin. We anticipate that our wound dressings would be useful for the treatment of various types of acute and chronic wounds.

Postsurgical tactile-evoked pain: a role for brain-derived neurotrophic factor-tropomyosin receptor kinase B-dependent novel tactile corpuscles

Introduction

Millions of people undergo surgical procedures each year with many developing postsurgical pain. Dynamic allodynia can arise when, for example, clothing brushing close to the surgical site elicits pain. The allodynia circuits that enable crosstalk between afferent tactile inputs and central pain circuits have been studied, but the peripheral tactile drive has not been explored.

Objective

Investigate the innervation of the skin in the rat plantar hindpaw skin-muscle incision model.

Results

Incision increased epidermal thickness and cell layers and reduced intraepidermal nerve fibre density, identified with PGP9.5 immunostaining. Strikingly, Collagen IV immunostaining revealed the development of dermal protrusions, oriented towards the incision site, that were reminiscent of the dermal papillae that exist in glabrous footpads. S100 immunostaining for lamellar Schwann cells revealed the presence of novel tactile corpuscles (S100-positive bulb) within incision-induced putative dermal papillae. The occurrence of these novel tactile corpuscles coincided with behavioural observations of dynamic allodynia. Tactile corpuscles require brain-derived neurotrophic factor- tropomyosin receptor kinase B (BDNF-TrkB) signalling to form during development, and an increase in BDNF-immunostaining intensity was observed close to the incision site. Local acute administration of TrkB-Fc, to block BDNF-TrkB signalling, reduced, by approximately 50%, both tactile corpuscle size (S100+ bulb area) and dynamic allodynia.

Conclusion

Surgery induces the development of novel tactile corpuscles in the incision surround, in a BDNF-TrKB-dependent manner, that contributes to postsurgical tactile-evoked pain.

The Impact of the Number and Duration of Treatments With a 1064 nm Diode Laser on Adipocyte Apoptosis: Implications for Noninvasive Fat Reduction Strategies

Background

Noninvasive treatment with a 1064 nm diode laser, generating hypodermal temperatures between 42 and 47 °C, induces adipocyte cell death, offering a solution to reduce fat in problematic areas.

Objectives

The objective of the authors of this study is to determine whether a 15 min treatment provides similar efficacy as the standard 25 min treatment.

Methods

Pigs underwent a 15 or 25 min 1064 nm laser treatment on 6 × 6 cm areas of abdominal skin. Single treatments were administered 14 or 28 days before biopsy, whereas dual treatments were performed at both 14 and 28 days prebiopsy. Hematoxylin and TUNEL staining were used to detect histological changes and apoptosis in harvested skin tissue.

Results

Pig skin subjected to a 25 min diode laser treatment exhibited nearly twice the apoptotic counts in the hypodermis compared with the 15 min treatment (10.5 vs 5.7) at 28 days following treatment. The degree of apoptosis increased with time following the treatment, with nearly twice the apoptosis counts at 28 days than at 14 days following a single 25 min treatment (10.5 vs 5.8). When testing 1 vs 2 treatments, 2 treatments (28 and 14 days before harvesting the tissue) did not result in significantly higher apoptosis than 1 treatment 28 days before harvesting. Apoptosis was primarily localized to adipocytes in the hypodermis and the dermis/hypodermis junction. There were no adverse side effects in the animals.

Conclusions

The degree of apoptosis following a 1064 nm laser treatment was proportional to the treatment duration. The 25 min treatment produced significantly more apoptosis than the 15 min treatment. The process of apoptosis continued over several weeks.

Level of Evidence 4 Therapeutic

Commercial Silver-Based Dressings: In Vitro and Clinical Studies in Treatment of Chronic and Burn Wounds

Chronic wounds are a major health problem because of delayed healing, causing hardships for the patient. The infection present in these wounds plays a role in delayed wound healing. Silver wound dressings have been used for decades, beginning in the 1960s with silver sulfadiazine for infection prevention for burn wounds. Since that time, there has been a large number of commercial silver dressings that have obtained FDA clearance. In this review, we examine the literature involving in vitro and in vivo (both animal and human clinical) studies with commercial silver dressings and attempt to glean the important characteristics of these dressings in treating infected wounds. The primary presentation of the literature is in the form of detailed tables. The narrative part of the review focuses on the different types of silver dressings, including the supporting matrix, the release characteristics of the silver into the surroundings, and their toxicity. Though there are many clinical studies of chronic and burn wounds using silver dressings that we discuss, it is difficult to compare the performances of the dressings directly because of the differences in the study protocols. We conclude that silver dressings can assist in wound healing, although it is difficult to provide general treatment guidelines. From a wound dressing point of view, future studies will need to focus on new delivery systems for silver, as well as the type of matrix in which the silver is deposited. Clearly, adding other actives to enhance the antimicrobial activity, including the disruption of mature biofilms is of interest. From a clinical point of view, the focus needs to be on the wound healing characteristics, and thus randomized control trials will provide more confidence in the results. The application of different wound dressings for specific wounds needs to be clarified, along with the application protocols. It is most likely that no single silver-based dressing can be used for all wounds.

Histological Changes of Porcine Animal Skin with Micro-focused Ultrasound

BACKGROUND

As a noninvasive alternative therapy, microfocused ultrasound (MFU) has become a research hotspot in recent years for its potential to enhance skin laxity. While several clinical studies have explored the effects of MFU on improving skin laxity, there is limited literature available on the histological changes resulting from MFU treatments. It has been established that the skin structure and composition of the Bama miniature pigs closely resembles that of humans, including collagen content, type I collagen distribution, and elastin distribution.

METHODS

This study primarily focuses on examining the histological alterations in the skin tissue of Bama miniature pigs following MFU application. We also selected some typical clinical photographs of patients treated with MFU and compared the clinical effects with histological changes observed in porcine skin. The MFU device utilized in this study incorporates ultra-pulse technology and large focal area technology.

RESULTS

Following the standard operating procedures provided by the manufacturer, different handles were used in different skin area of pigs. Biopsies were obtained immediately after treatment and 1 month after treatment. Significant histological changes were observed in the Bama miniature pigs skin, including collagen contraction and fragmentation, dilation and congestion of superficial dermal capillaries immediately after MFU treatment; dermal thickening, increased thickness and density of collagen fibers, elevated levels of elastin and type I collagen, as well as thickened fiber septa in the adipose layer 1 month later. These histological results corresponded to clinical findings in human, such as facial redness and swelling immediately after treatment, and improvement in facial relaxation after approximately 1 month after treatment.

CONCLUSION

Collectively, these histological findings provide valuable evidence supporting the clinical application of MFU for enhancing skin laxity.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. 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 effect of anatomic location on porcine models of burn injury and wound healing

Porcine models are frequently used for burn healing studies; however, factors including anatomic location and lack of standardised wound methods can impact the interpretation of wound data. The objectives of this study are to examine the influence of anatomical locations on the uniformity of burn creation and healing in porcine burn models. To optimise burn parameters on dorsal and ventral surfaces, ex vivo and in situ euthanized animals were first used to examine the location-dependence of the burn depth and contact time relationship. The location-dependent healing in vivo was then examined using burn and excisional wounds at dorsal, ventral, caudal and cranial locations. Lactate dehydrogenase (LDH) and H&E were used to assess burn depth and wound re-epithelialization. We found that burn depth on the ventral skin was significantly deeper than that of the dorsal skin at identical thermal conditions. Compared with burns created ex vivo, burns created in situ immediately post-mortem were significantly deeper in the ventral location. In live animals, 2 out of 12 burn wounds were fully re-epithelialized after 14 days in contrast to complete re-epithelialization of all excisional wounds. Among the burn wounds, those at the cranial-dorsal site exhibited faster healing than at the caudal-dorsal site. This study showed that anatomical location is an important consideration for the consistency of burn depth creation and healing. These data support symmetric localization of treatment and control for comparative assessment of burn healing in porcine models to prevent misinterpretation of results and increase the translatability of findings to humans.

OxInflammation Affects Transdifferentiation to Myofibroblasts, Prolonging Wound Healing in Diabetes: A Systematic Review

Skin wounds, primarily in association with type I diabetes mellitus, are a public health problem generating significant health impacts. Therefore, identifying the main pathways/mechanisms involved in differentiating fibroblasts into myofibroblasts is fundamental to guide research into effective treatments. Adopting the PRISMA guidelines, this study aimed to verify the main pathways/mechanisms using diabetic murine models and analyze the advances and limitations of this area. The Medline (PubMed), Scopus, and Web of Science platforms were used for the search. The studies included were limited to those that used diabetic murine models with excisional wounds. Bias analysis and methodological quality assessments were undertaken using the SYRCLE bias risk tool. Eighteen studies were selected. The systematic review results confirm that diabetes impairs the transformation of fibroblasts into myofibroblasts by affecting the expression of several growth factors, most notably transforming growth factor beta (TGF-beta) and NLRP3. Diabetes also compromises pathways such as the SMAD, c-Jun N-terminal kinase, protein kinase C, and nuclear factor kappa beta activating caspase pathways, leading to cell death. Furthermore, diabetes renders the wound environment highly pro-oxidant and inflammatory, which is known as OxInflammation. As a consequence of this OxInflammation, delays in the collagenization process occur. The protocol details for this systematic review were registered with PROSPERO: CRD42021267776.

Structural and molecular characteristics of weight-bearing volar skin can be reconstituted by micro skin tissue column grafting

For patients with lower limb amputations, prostheses are immensely helpful for mobility and the ability to perform job-related or recreational activities. However, the skin covering the amputation stump is typically transposed from adjacent areas of the leg and lacks the weight-bearing capacity that is only found in the specialized skin covering the palms and soles (a.k.a. volar skin). As a result, the skin tissue in direct contact with the prosthesis frequently breaks down, leading to the development of painful sores and other complications that limit, and often preclude, the use of prostheses. Transplanting volar skin onto amputation stumps could be a solution to these problems, but traditional skin transplantation techniques cause substantial morbidity at the donor site, such as pain and scarring, which are especially problematic for volar skin given the critical functional importance of the volar skin areas. We previously developed the technology to collect and engraft full-thickness skin tissue while avoiding long-term donor site morbidity, by harvesting the skin in the form of small (~0.5 mm diameter) cores that we termed "micro skin tissue columns" (MSTCs), so that each donor wound is small enough to heal quickly and without clinically appreciable scarring or other long-term abnormalities. The goal of this study was to establish whether a similar approach could be used to confer the structural and molecular characteristics of volar skin ectopically to other skin areas. In a human-to-mouse xenograft model, we show the long-term persistence of various human plantar MSTC-derived cell types in the murine recipient. Then in an autologous porcine model, we harvested MSTCs from the bottom of the foot and transplanted them onto excision wounds on the animals' trunks. The healing processes at both the donor and graft sites were monitored over 8 weeks, and tissue samples were taken to verify volar-specific characteristics by histology and immunohistochemistry. The volar donor sites were well-tolerated, healed rapidly, and showed no signs of scarring or any other long-term defects. The graft sites were able to maintain volar-specific histologic features and expression of characteristics protein markers, up to the 8-week duration of this study. These results suggest that MSTC grafting could be a practical approach to obtain autologous donor volar skin tissue, confer volar skin characteristics ectopically to nonvolar skin areas, improve the load-bearing capacity of amputation stump skin, and ultimately enhance mobility and quality-of-life for lower limb amputees.

The rat as an animal model in chronic wound research: An update

The increasing global prevalence of chronic wounds underscores the growing importance of developing effective animal models for their study. This review offers a critical evaluation of the strengths and limitations of rat models frequently employed in chronic wound research and proposes potential improvements. It explores these models in the context of key comorbidities, including diabetes, venous and arterial insufficiency, pressure-induced blood flow obstruction, and infections. Additionally, the review examines important wound factors including age, sex, smoking, and the impact of anesthetic and analgesic drugs, acknowledging their substantial effects on research outcomes. A thorough understanding of these variables is crucial for refining animal models and can provide valuable insights for future research endeavors.

Development of a Wound Epithelialization Healing Model: Reducing the Impact of Contraction Healing on the Wound Surface

Animal experiments are important in trauma-related studies because they simulate in vivo effects. Rodents are a good choice for preparing trauma models; however, contractile healing in rodents results in a healing pattern that differs considerably from that in humans. Therefore, this study developed a new rodent model that avoids contractile healing of the skin around the wound using an anticontraction ring, and the skin in the wound's center remains intact and acts as a source for epithelialized diffusion healing. Cell proliferation, migration, revascularization, and collagen secretion did not differ between the novel and conventional full-skin defect trauma models. However, the healing rate at various stages significantly differed between the 2 groups owing to differences in the healing patterns. And without effective treatment, the experimental group cannot heal. The stabilities of the novel and conventional methods were good regardless of operator or batch. In summary, this new animal trauma model provides a stable experimental environment similar to that in humans, which may promote trauma-related research.

Pectin-honey hydrogel to prevent laparotomy surgical site infection in horses: A pilot study

Surgical site infection (SSI) is a common complication after celiotomy in horses, leading to increased morbidity and costs. Increased concern about antibiotic resistance justifies evaluation of alternative preventive approaches, such a Manuka honey which has displayed antimicrobial properties. Pectin-Honey Hydrogels (PHH), composed by Manuka honey and pectin provide a moist wound environment and microbial growth inhibition. The aim of the study was to evaluate the effectiveness of PHHs in preventing SSI in horses subjected to emergency laparotomy. Horses undergoing laparotomy were evaluated. Horses were randomly divided into two groups: Group 1 received PHH application onto the sutured linea alba before skin closure, while Group 2 received no treatment. Horses with postoperative antimicrobial administration or survival of less than 5 days were excluded. The incidence of SSIs was reported as percentages and compared between groups. Out of 44 horses enrolled in the study, only thirty-six were ultimately included. Exclusions occurred either due to death before 5 days postoperatively (2 horses) or the administration of postoperative antimicrobials (6 horses). The median length of hospitalization was 9 days (range 8-14 days). The overall occurrence of SSI was 19.4 %. One out of eighteen horses (5.5 %) in Group 1 and 6 out of 18 (33.3 %) horses in Group 2 developed SSI. Group 2 had an 8.5-fold increased risk of SSI (p = 0.035, OR = 8.5, 95 % CI. 0.9-80.07). No macroscopically visible adverse reactions were associated with PHH. PHH placed at the abdominal incision during surgery was safe and reduced the prevalence of SSI in horses.

Perspective from developers: Tissue-engineered products for skin wound healing

Tissue-engineered products (TEPs) are at the forefront of developmental medicines, precisely where monoclonal antibodies and recombinant cytokines were 30 years ago. TEPs development for treating skin wounds has become a fast-growing field as it offers the potential to find novel therapeutic approaches for treating pathologies that currently have limited or no effective alternatives. This review aims to provide the reader with the process of translating an idea from the laboratory bench to clinical practice, specifically in the context of TEPs designing for skin wound healing. It encompasses historical perspectives, approved therapies, and offers a distinctive insight into the regulatory framework in Brazil. We explore the essential guidelines for quality testing, and nonclinical proof-of-concept considering the Brazilian Network of Experts in Advanced Therapies (RENETA) and International Standards and Guidelines (ICH e ISO). Adopting a multifaceted approach, our discussion incorporates scientific and industrial perspectives, addressing quality, biosafety, non-clinical viability, clinical trial and real-word data for pharmacovigilance demands. This comprehensive analysis presents a panoramic view of the development of skin TEPs, offering insights into the evolving landscape of this dynamic and promising field.

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.

Plantar Skin Exhibits Altered Physiology, Constitutive Activation of Wound-Associated Phenotypes, and Inherently Delayed Healing

Wound research has typically been performed without regard for where the wounds are located on the body, despite well-known heterogeneities in physical and biological properties between different skin areas. The skin covering the palms and soles is highly specialized, and plantar ulcers are one of the most challenging and costly wound types to manage. Using primarily the porcine model, we show that plantar skin is molecularly and functionally more distinct from nonplantar skin than previously recognized, with unique gene and protein expression profiles, broad alterations in cellular functions, constitutive activation of many wound-associated phenotypes, and inherently delayed healing. This unusual physiology is likely to play a significant but underappreciated role in the pathogenesis of plantar ulcers as well as the last 25+ years of futility in therapy development efforts. By revealing this critical yet unrecognized pitfall, we hope to contribute to the development of more effective therapies for these devastating nonhealing wounds.

Modeling Wound Chronicity In Vivo: The Translational Challenge to Capture the Complexity of Chronic Wounds

In an aging society with common lifestyle-associated health issues such as obesity and diabetes, chronic wounds pose a frequent challenge that physicians face in everyday clinical practice. Therefore, nonhealing wounds have attracted much scientific attention. Several in vitro and in vivo models have been introduced to deepen our understanding of chronic wound pathogenesis and amplify therapeutic strategies. Understanding how wounds become chronic will provide insights to reverse or avoid chronicity. Although choosing a suitable model is of utmost importance to receive valuable outcomes, an ideal in vivo model capturing the complexity of chronic wounds is still missing and remains a translational challenge. This review discusses the most relevant mammalian models for wound healing studies and provides guidance on how to implement the hallmarks of chronic wounds. It highlights the benefits and pitfalls of established models and maps out future avenues for research.

Adipose-derived stem cells in diabetic foot care: Bridging clinical trials and practical application

Diabetic foot ulcers (DFUs) pose a critical medical challenge, significantly im-pairing the quality of life of patients. Adipose-derived stem cells (ADSCs) have been identified as a promising therapeutic approach for improving wound healing in DFUs. Despite extensive exploration of the mechanical aspects of ADSC therapy against DFU, its clinical applications remain elusive. In this review, we aimed to bridge this gap by evaluating the use and advancements of ADSCs in the clinical management of DFUs. The review begins with a discussion of the classification and clinical management of diabetic foot conditions. It then discusses the current landscape of clinical trials, focusing on their geographic distribution, reported efficacy, safety profiles, treatment timing, administration techniques, and dosing considerations. Finally, the review discusses the preclinical strategies to enhance ADSC efficacy. This review shows that many trials exhibit biases in study design, unclear inclusion criteria, and intervention protocols. In conclusion, this review underscores the potential of ADSCs in DFU treatment and emphasizes the critical need for further research and refinement of therapeutic approaches, with a focus on improving the quality of future clinical trials to enhance treatment outcomes and advance the field of diabetic wound care.

Cold atmospheric plasma is bactericidal to wound-relevant pathogens and is compatible with burn wound healing

Burn wound healing can be significantly delayed by infection leading to increased morbidity and hypertrophic scarring. An optimal antimicrobial agent would have the ability to kill bacteria without negatively affecting the host skin cells that are required for healing. Currently available products provide antimicrobial coverage, but may also cause reductions in cell proliferation and migration. Cold atmospheric plasma is a partially ionized gas that can be produced under atmospheric pressure at room temperature. In this study a novel handheld Aceso Plasma Generator was used to produce and test Aceso Cold Plasma (ACP) in vitro and in vivo. ACP showed a potent ability to eliminate bacterial load in vitro for a number of different species. Deep partial-thickness and full-thickness wounds that were treated with ACP after burning, after excision, after autografting, and at days 5, 7, and 9 did not show any negative effects on their wound healing trajectories. On par with in vitro analysis, bioburden was decreased in treated wounds vs. control. In addition, metrics of hypertrophic scar such as dyschromia, elasticity, trans-epidermal water loss (TEWL), and epidermal and dermal thickness were the same between the two treatment groups.It is likely that ACP can be used to mitigate the risk of bacterial infection during the phase of acute burn injury while patients await surgery for definitive closure. It may also be useful in treating wounds with delayed re-epithelialization that are at risk for infection and hypertrophic scarring. A handheld cold plasma device will be useful in treating all manner of wounds and surgical sites in order to decrease bacterial burden in an efficient and highly effective manner without compromising wound healing.

The Goettingen minipig as an experimental model in wound-healing studies

Background

Deep dermal wounds in extensive burns and chronic wound-healing disorders represent a significant medical problem and require a high level of therapy to reduce the risk of infection and other long-term consequences, such as amputation. A better understanding of the wound-healing processes is essential, and animal models are indispensable to fundamental research.

Objective

This study aimed to provide a transparent protocol and prove the effectiveness of an in vivo porcine model using Goettingen minipigs for wound-healing studies.

Material and methods

Thirteen female Goettingen minipigs were kept in species-appropriate housing and were treated according to the German law for the protection of animals. The study was performed with permission from the local ethical review committee of animal welfare. The experimental procedure for studying dermal regeneration in 102 full-thickness wounds through clinical observation and histological analysis, focusing on neodermal formation, is described in detail.

Results

The Goettingen minipig model proved to be suitable in wound-healing studies. The dermal regeneration was evident and viewable without wound contamination or any rejection reaction. The histological evaluations were also reliable and clearly presented the optimized wound healing of deep dermal wounds using the different therapeutic approaches.

Conclusion

Given the great clinical need for alternative or complementary therapies, we considered the Goettingen minipig trial a reliable, ethically justifiable, effective, and reproducible in vivo model for wound-healing studies.

A chromosome-level genome of Chenghua pig provides new insights into the domestication and local adaptation of pigs

As a country with abundant genetic resources of pigs, the domestication history of pigs in China and the adaptive evolution of Chinese pig breeds at different latitudes have rarely been elucidated at the genome-wide level. To fill this gap, we first assembled a high-quality chromosome-level genome of the Chenghua pig and used it as a benchmark to analyse the genomes of 272 samples from three genera of three continents. The divergence of the three species belonging to three genera, Phacochoerus africanus, Potamochoerus porcus, and Sus scrofa, was assessed. The introgression of pig breeds redefined that the migration routes were basically from southern China to central and southwestern China, then spread to eastern China, arrived in northern China, and finally reached Europe. The domestication of pigs in China occurred ∼12,000 years ago, earlier than the available Chinese archaeological domestication evidence. In addition, FBN1 and NR6A1 were identified in our study as candidate genes related to extreme skin thickness differences in Eurasian pig breeds and adaptive evolution at different latitudes in Chinese pig breeds, respectively. Our study provides a new resource for the pig genomic pool and refines our understanding of pig genetic diversity, domestication, migration, and adaptive evolution at different latitudes.

Thermal damage to the skin from 8.2 and 95 GHz microwave exposures in swine

A study of burn thresholds from superficially penetrating radio-frequency (RF) energy at 8.2 and 95 GHz for swine skin was conducted. The study determined the thresholds for superficial, partial-thickness, and full-thickness burn severities after 5 seconds of exposure at power densities of 4-30 W/cm2and 2-15 W/cm2at 8.2 and 95 GHz, respectively. There were significant differences in he burn thresholds at the different severities between the two frequencies due to the large difference in energy penetration depths. Biopsies were collected from each burn site at 1, 24, 72, and 168 hr post exposure. Each sample was assessed by a burn pathologist against 20 histological factors to characterize the damage resulting from these RF overexposures. A one-dimensional, layered digital phantom that utilized realistic values for dielectric and thermal properties was used to explain some observed thresholds. The results of the heating and cooling response of the animal model and histology scores of each exposure are provided to enhance future efforts at simulation of RF overexposures and to establish damage thresholds.

Nano oxygen chamber by cascade reaction for hypoxia mitigation and reactive oxygen species scavenging in wound healing

Hypoxia, excessive reactive oxygen species (ROS), and impaired angiogenesis are prominent obstacles to wound healing following trauma and surgical procedures, often leading to the development of keloids and hypertrophic scars. To address these challenges, a novel approach has been proposed, involving the development of a cascade enzymatic reaction-based nanocarriers-laden wound dressing. This advanced technology incorporates superoxide dismutase modified oxygen nanobubbles and catalase modified oxygen nanobubbles within an alginate hydrogel matrix. The oxygen nano chamber functions through a cascade reaction between superoxide dismutase and catalase, wherein excessive superoxide in the wound environment is enzymatically decomposed into hydrogen peroxide, and this hydrogen peroxide is subsequently converted into oxygen by catalase. This enzymatic cascade effectively controls wound inflammation and hypoxia, mitigating the risk of keloid formation. Concurrently, the oxygen nanobubbles release oxygen continuously, thus providing a sustained supply of oxygen to the wound site. The oxygen release from this dynamic system stimulates fibroblast proliferation, fosters the formation of new blood vessels, and contributes to the overall wound healing process. In the rat full-thickness wound model, the cascade reaction-based nano oxygen chamber displayed a notable capacity to expedite wound healing without scarring. Furthermore, in the pilot study of porcine full-thickness wound healing, a notable acceleration of tissue repair was observed in the conceived cascade reaction-based gel treated group within the 3 days post-surgery, which represents the proliferation stage of healing process. These achievements hold significant importance in ensuring the complete functional recovery of tissues, thereby highlighting its potential as a promising approach for enhancing wound healing outcomes.

Highly Resilient Noncovalently Associated Hydrogel Adhesives for Wound Sealing Patch

The development of hydrogel adhesives with high mechanical resilience and toughness remains a challenging task. Hydrogels must exhibit high mechanical resilience to withstand the inevitable movement of the human body while simultaneously demonstrating strong wet tissue adhesion and appropriate toughness to hold and seal damaged tissues; However, tissue adhesion, toughness, and mechanical resilience are typically negatively correlated. Therefore, this paper proposes a highly resilient double-network (DN) hydrogel wound-sealing patch that exhibits a well-balanced combination of tissue adhesion, toughness, and mechanical resilience. The DN structure is formed by introducing covalently and non-covalently crosslinkable dopamine-modified crosslinkers and physically interactable linear poly(vinyl imidazole) (PVI). The resulting hydrogel adhesive exhibits high toughness and mechanical resilience due to the presence of a DN involving reversible physical intermolecular interactions such as hydrogen bonds, hydrophobic associations, cation-π interactions, π-π interactions, and chain entanglements. Moreover, the hydrogel adhesive achieves strong wet tissue adhesion through the polar hydroxyl groups of dopamine and the amine group of PVI. These mechanical attributes allow the proposed adhesive to effectively seal damaged tissues and promote wound healing by maintaining a moist environment.

Adjuvants in cutaneous vaccination: A comprehensive analysis

Skin is the body's largest organ and serves as a protective barrier from physical, thermal, and mechanical environmental challenges. Alongside, the skin hosts key immune system players, such as the professional antigen-presenting cells (APCs) like the Langerhans cells in the epidermis and circulating macrophages in the blood. Further, the literature supports that the APCs can be activated by antigen or vaccine delivery via multiple routes of administration through the skin. Once activated, the stimulated APCs drain to the associated lymph nodes and gain access to the lymphatic system. This further allows the APCs to engage with the adaptive immune system and activate cellular and humoral immune responses. Thus, vaccine delivery via skin offers advantages such as reliable antigen delivery, superior immunogenicity, and convenient delivery. Several preclinical and clinical studies have demonstrated the significance of vaccine delivery using various routes of administration via skin. However, such vaccines often employ adjuvant/(s), along with the antigen of interest. Adjuvants augment the immune response to a vaccine antigen and improve the therapeutic efficacy. Due to these reasons, adjuvants have been successfully used with infectious disease vaccines, cancer immunotherapy, and immune-mediated diseases. To capture these developments, this review will summarize preclinical and clinical study results of vaccine delivery via skin in the presence of adjuvants. A focused discussion regarding the FDA-approved adjuvants will address the experiences of using such adjuvant-containing vaccines. In addition, the challenges and regulatory concerns with these adjuvants will be discussed. Finally, the review will share the prospects of adjuvant-containing vaccines delivered via skin.

The Immunomodulatory effect of exosomes in diabetes: a novel and attractive therapeutic tool in diabetes therapy

Exosomes carry proteins, metabolites, nucleic acids and lipids from their parent cell of origin. They are derived from cells through exocytosis, are ingested by target cells, and can transfer biological signals between local or distant cells. Therefore, exosomes are often modified in reaction to pathological processes, including infection, cancer, cardiovascular diseases and in response to metabolic perturbations such as obesity and diabetes, all of which involve a significant inflammatory aspect. Here, we discuss how immune cell-derived exosomes origin from neutrophils, T lymphocytes, macrophages impact on the immune reprogramming of diabetes and the associated complications. Besides, exosomes derived from stem cells and their immunomodulatory properties and anti-inflammation effect in diabetes are also reviewed. Moreover, As an important addition to previous reviews, we describes promising directions involving engineered exosomes as well as current challenges of clinical applications in diabetic therapy. Further research on exosomes will explore their potential in translational medicine and provide new avenues for the development of effective clinical diagnostics and therapeutic strategies for immunoregulation of diabetes.

Bringing innovative wound care polymer materials to the market: Challenges, developments, and new trends

The development of innovative products for treating acute and chronic wounds has become a significant topic in healthcare, resulting in numerous products and innovations over time. The growing number of patients with comorbidities and chronic diseases, which may significantly alter, delay, or inhibit normal wound healing, has introduced considerable new challenges into the wound management scenario. Researchers in academia have quickly identified promising solutions, and many advanced wound healing materials have recently been designed; however, their successful translation to the market remains highly complex and unlikely without the contribution of industry experts. This review article condenses the main aspects of wound healing applications that will serve as a practical guide for researchers working in academia and industry devoted to designing, evaluating, validating, and translating polymer wound care materials to the market. The article highlights the current challenges in wound management, describes the state-of-the-art products already on the market and trending polymer materials, describes the regulation pathways for approval, discusses current wound healing models, and offers a perspective on new technologies that could soon reach consumers. We envision that this comprehensive review will significantly contribute to highlighting the importance of networking and exchanges between academia and healthcare companies. Only through the joint of these two actors, where innovation, manufacturing, regulatory insights, and financial resources act in harmony, can wound care products be developed efficiently to reach patients quickly and affordably.