“Xenograft” dressing in the treatment of burns

Skin Substitutes and Autograft Techniques: Temporary and Permanent Coverage Solutions

Coverage of burn wounds is crucial to prevent sequalae including dehydration, wound infection, sepsis, shock, scarring, and contracture. To this end, numerous temporary and permanent options for coverage of burn wounds have been described. Temporary options for burn coverage include synthetic dressings, allografts, and xenografts. Permanent burn coverage can be achieved through skin substitutes, cultured epithelial autograft, ReCell, amnion, and autografting. Here, we aim to summarize the available options for burn coverage, as well as important considerations that must be made when choosing the best reconstructive option for a particular patient.

Consensus on the treatment of second-degree burn wounds (2024 edition)

Second-degree burns are the most common type of burn in clinical practice and hard to manage. Their treatment requires not only a consideration of the different outcomes that may arise from the dressing changes or surgical therapies themselves but also an evaluation of factors such as the burn site, patient age and burn area. Meanwhile, special attention should be given to the fact that there is no unified standard or specification for the diagnosis, classification, surgical procedure, and infection diagnosis and grading of second-degree burn wounds. This not only poses great challenges to the formulation of clinical treatment plans but also significantly affects the consistency of clinical studies. Moreover, currently, there are relatively few guidelines or expert consensus for the management of second-degree burn wounds, and no comprehensive and systematic guidelines or specifications for the treatment of second-degree burns have been formed. Therefore, we developed the Consensus on the Treatment of Second-Degree Burn Wounds (2024 edition), based on evidence-based medicine and expert opinion. This consensus provides specific recommendations on prehospital first aid, nonsurgical treatment, surgical treatment and infection treatment for second-degree burns. The current consensus generated a total of 58 recommendations, aiming to form a standardized clinical treatment plan.

New strategies for sterilization and preservation of fresh fish skin grafts

The introduction of fish skin as a biological dressing for treating burns and wounds holds great promise, offering an alternative to existing management strategies. However, the risk of disease transmission is a significant concern. Therefore, this study aimed to examine how established sterilization and preservation procedures affected fish skin grafts' microbiological and histological properties for long-term usage. Lyophilization of the fish skin graft followed by rehydration in normal saline for 15 min did not change the collagen content. Furthermore, gamma irradiation of the lyophilized fish skin graft at different lengths 5, 10, and 25 KGy showed a significant reduction in microbial growth (aerobic bacteria, aerobic yeasts, and fungi) at 15- and 30 days after the irradiation. However, exposure to 10 KGy was found to be the most effective intensity among the different gamma irradiation lengths since it preserved the collagen fiber content and intensity in the lyophilized fish skin grafts at 15- and 30 days after the irradiation. These findings provide efficient preservation and sterilization methods for long-term usage of the fresh Tilapia skin grafts used for biological dressings.

In vitro and in vivo immune assessments of genetically-engineered pig skin grafts in New World (squirrel) monkeys

Half a million patients in the USA alone require treatment for burns annually. Following an extensive burn, it may not be possible to provide sufficient autografts in a single setting. Genetic manipulations (GM) of pigs offer the possibility of reducing primate humoral and cellular rejection of pig skin xenografts and thus extending graft survival. We compared the survival of skin grafts from pigs with 9-GM with that of autografts and allografts in squirrel monkeys. Monitoring for rejection was by (1) macroscopic examination, (2) histopathological examination of skin biopsies, and (3) measurement of anti-monkey and anti-pig IgM and IgG antibodies. Autografts (n = 5) survived throughout the 28 days of follow-up without histopathological features of rejection. Median survival of allografts (n = 6) was 14 days and of pig xenografts (n = 12) 21 days. Allotransplantation was associated with an increase in anti-monkey IgM, but the anticipated subsequent rise in IgG had not yet occurred at the time of euthanasia. Pig grafts were associated with increases in anti-pig IgM and IgG. In all cases, histopathologic features of rejection were similar. 9-GM pig skin xenografts survive at least as long as monkey skin allografts (and trended to survive longer), suggesting that they are a realistic clinical option for the temporary treatment of burns. Although monkeys with pig skin grafts developed anti-pig IgM and IgG antibodies, these did not cross-react with monkey antigens, indicating that a primary 9-GM pig skin graft would not be detrimental to a subsequent monkey skin allograft.

Current state of clinical trials on xenograft

BACKGROUND

Xenotransplantation is a worth investing branch of science, since it aims to fulfil the demand on human cells, tissues and organs. Despite decades of consistent work in preclinical assessments, clinical trials on xenotransplantation are far from reaching the targeted goal. Our study aims to track the characteristics, assess the content and summarize the plan of each trial on skin, beta-island, bone marrow, aortic valve and kidney xenografts, leading to a clear sorting of efforts made in this field.

METHODS

In December 2022, we searched clinicaltrial.gov for interventional clinical trials related to xenograft of skin, pancreas, bone marrow, aortic valve and kidney. A total of 14 clinical trials are included in this study. Characteristics on each trial were gathered. Linked publications were searched using Medline/PubMed and Embase/Scopus. Content of trials was reviewed and summarized.

RESULTS

Only 14 clinical trials met our study's criteria. The majority were completed, and most of the trials' enrolment was between 11 and 50 participants. Nine trials used a xenograft of porcine origin. Six trials targeted skin xenotransplantation, four targeted β-cells, two targeted bone marrow and one trial targeted each of the kidney and aortic valve. The average length of trials was 3.38 years. Four trials were conducted in the United States and two trials in each of Brazil, Argentina and Sweden. Of all the included trials, none had any results provided and only three had published work. Phases I, III, and IV had only one trial each. A total of 501 participants were enrolled in these trials.

CONCLUSION

This study sheds the light on the current state of clinical trials on xenograft. Characteristically, trials on this field are of low number, low enrolment, short duration, few related publications and no published results. Porcine organs are the most used in these trials, and skin is the most studied organ. An extension of the literature is highly needed due to the variety of conflicts mentioned. Overall, this study sheds the light on the necessity of managing research efforts, leading to the initiation of more trials targeting the field of xenotransplantation.

Imaging and Characterization of Oxidative Protein Modifications in Skin

Skin plays an important role in protection, metabolism, thermoregulation, sensation, and excretion whilst being consistently exposed to environmental aggression, including biotic and abiotic stresses. During the generation of oxidative stress in the skin, the epidermal and dermal cells are generally regarded as the most affected regions. The participation of reactive oxygen species (ROS) as a result of environmental fluctuations has been experimentally proven by several researchers and is well known to contribute to ultra-weak photon emission via the oxidation of biomolecules (lipids, proteins, and nucleic acids). More recently, ultra-weak photon emission detection techniques have been introduced to investigate the conditions of oxidative stress in various living systems in in vivo, ex vivo and in vitro studies. Research into two-dimensional photon imaging is drawing growing attention because of its application as a non-invasive tool. We monitored spontaneous and stress-induced ultra-weak photon emission under the exogenous application of a Fenton reagent. The results showed a marked difference in the ultra-weak photon emission. Overall, these results suggest that triplet carbonyl (³C=O^∗) and singlet oxygen (¹O₂) are the final emitters. Furthermore, the formation of oxidatively modified protein adducts and protein carbonyl formation upon treatment with hydrogen peroxide (H₂O₂) were observed using an immunoblotting assay. The results from this study broaden our understanding of the mechanism of the generation of ROS in skin layers and the formation/contribution of various excited species can be used as tools to determine the physiological state of the organism.

Human Umbilical Cord Lining-Derived Epithelial Cells: A Potential Source of Non-Native Epithelial Cells That Accelerate Healing in a Porcine Cutaneous Wound Model

Human umbilical cord lining epithelial cells [CLECs) are naïve in nature and can be ethically recovered from cords that are routinely discarded. The success of using oral mucosal epithelial cells for cornea defects hints at the feasibility of treating cutaneous wounds using non-native CLECs. Herein, we characterized CLECs using flow cytometry (FC) and skin organotypic cultures in direct comparison with skin keratinocytes (KCs). This was followed by wound healing study to compare the effects of CLEC application and the traditional use of human skin allografts (HSGs) in a porcine wound model. While CLECs were found to express all the epidermal cell markers probed, the major difference between CLECs and KCs lies in the level of expression (in FC analysis) as well as in the location of expression (of the epithelium in organotypic cultures) of some of the basal cell markers probed. On the pig wounds, CLEC application promoted accelerated healing with no adverse reaction compared to HSG use. Though CLECs, like HSGs, elicited high levels of local and systemic immune responses in the animals during the first week, these effects were tapered off more quickly in the CLEC-treated group. Overall, the in vivo porcine data point to the potential of CLECs as a non-native and safe source of cells to treat cutaneous wounds.

Biosynthetic cellulose compared to porcine xenograft in the treatment of partial-thickness burns: A randomised clinical trial

AIM

The aim was to compare two dressing treatments for partial-thickness burns: biosynthetic cellulose dressing (BsC) (Epiprotect® S2Medical AB, Linköping, Sweden) and porcine xenograft (EZ Derm®, Mölnlycke Health Care, Gothenburg, Sweden).

METHODS

Twenty-four adults with partial-thickness burns were included in this randomized clinical trial conducted at The Burn Centers in Linköping and Uppsala, Sweden between June 2016 and November 2018. Time to healing was the primary outcome. Secondary outcomes were wound infection, pain, impact on everyday life, length of hospital stay, cost, and burn scar outcome (evaluated with POSAS).

RESULTS

We found no significant differences between the two dressing groups regarding time to healing, wound infection, pain, impact on everyday life, duration of hospital stay, cost, or burn scar outcome at the first follow up. Burn scar outcome at the 12-month follow up showed that the porcine xenograft group patients scored their scars higher on the POSAS items thickness (p = 0.048) and relief (p = 0.050). This difference was, however, not confirmed by the observer.

CONCLUSIONS

The results showed the dressings performed similarly when used in adults with burns evaluated as partial thickness.

Therapeutic Treatment of 2A Grade Burns with Decellularized Bovine Peritoneum as a Xenograft: Multicenter Randomized Clinical Trial

Background and Objectives: Homogeneous and xenogenic bioengineering structures are actively used as wound coatings in treatment of burns and have already shown their effectiveness. Nevertheless, the disadvantage of such dressings is their high cost. This issue is particularly challenging for developing countries in which the incidence of burns is the highest one. With such needs taken into account, the research team developed and clinically tested a new wound coating based on decellularized bovine peritoneum (DBP). Materials and Methods: A multicenter randomized clinical trial was conducted to evaluate DBP. The following variables were considered in the research study: the number of inpatient days, the number of dressing changes, the level of pain experienced during dressing changes, and the condition of wounds at the time of the follow-up examination. Results: The research involved 68 participants. It was found that the patients who were treated with a DBP experienced less pain with less changes of dressings. However, the number of inpatient days and wound healing failed to demonstrate statistically significant difference compared to the control group. Conclusions: In the given research, DBP showed efficacy in improving patients' quality of life by reducing pain and the number of dressings' changes. However, when comparing this research study with the studies of other animal-derived wound coverings, there were a number of differences and limitations in the parameters. Thus, the results requires further study for a greater comparability of data. Given the above, we expect that DBP will become an inexpensive and effective treatment for burns in developing countries.

Successful Treatment Outcomes for Partial Thickness Burns by Innovative Bovine Peritoneum Dressing

In the world practice of treating burns, acellular matrices have been used for quite a long time. However, the budget for treating one burn patient in Kazakhstan does not exceed $1000. This amount does not cover the costs for procurement of foreign-made xenograft dressings. Because the cattle breeding sector is very well-developed in the country, a domestic xenograft is produced by decellularization and sterilization of the cattle peritoneum, which costs only $10. This case report outlines how we used this matrix in a patient with partial thickness burns. A 45-year-old woman was admitted to the burn department with second stage burns on her back and right shoulder. The burn area comprised 10%, according to the Lund Browder chart. Once formal consent was obtained from the patient, an occlusive dressing was applied from the decellularized cattle peritoneum. Good adhesion of the dressing to the wound bed was noted. The patient was discharged from the hospital on the tenth day. It took 23 days to reach complete epithelialization. No adverse effects were noted. We believe that further studies conducted by our research team will allow this innovative, low-cost, easy-to-apply biologic dressing to be widely used in the therapeutic treatment of burns.

Lipid mediator profiles of burn wound healing: Acellular cod fish skin grafts promote the formation of EPA and DHA derived lipid mediators following seven days of treatment

The use of acellular fish skin grafts (FSG) for the treatment of burn wounds is becoming more common due to its beneficial wound healing properties. In our previous study we demonstarted that FSG is a scaffold biomaterial that is rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) conjugated to phosphatidylcholines. Here we investigated whether EPA and DHA derived lipid mediators are influenced during the healing of burn wounds treated with FSG. Deep partial and full thickness burn wounds (DPT and FT, respectively) were created on Yorkshire pigs (n = 4). DPT were treated with either FSG or fetal bovine dermis while FT were treated either with FSG or cadaver skin initially and followed by a split thickness skin graft. Punch biopsies were collected on days 7, 14, 21, 28 and 60 and analyzed in respect of changes to approximately 45 derivatives of EPA, DHA, arachidonic acid (AA), and linoleic acid (LA) employing UPLC-MS/MS methodology. Nine EPA and DHA lipid mediators, principally mono-hydroxylated derivatives such as 18-HEPE and 17-HDHA, were significantly higher on day 7 in the DPT when treated with FSG. A similar but non-significant trend was observed for the FT. The results suggest that the use of FSG in burn wound treatment can alter the formation of EPA and DHA mono hydroxylated lipid mediators in comparison to other grafts of mammalian origin. The differences observed during the first seven days after treatment indicates that FSG affects the early stages of wound healing.

Initial Experience Combining Negative Pressure Wound Therapy With Autologous Skin Cell Suspension and Meshed Autografts

The success of autologous split-thickness skin grafts (STSGs) in the treatment of full-thickness burns is often dependent on the dressing used to secure it. Tie-over bolsters have been used traditionally; however, they can be uncomfortable for patients and preclude grafting large areas in one definitive operation. Negative pressure wound therapy (NPWT) is used as an alternative to bolster dressings and may afford additional wound healing benefits. In our center, NPWT has become the dressing of choice for securing STSGs. While the RECELL® system is being used in conjunction with STSGs, it is currently unknown whether autologous skin cell suspensions (ASCS) can be used with NPWT. This report is a retrospective chart review of nine patients treated in this manner. All wounds were almost completely re-epithelialized within 14 days, and their healing was as expected. Wound healing trajectories are shown. There were no significant complications in these patients. This dressing technique can be considered as an option when using ASCS and widely meshed STSG.

Clinical Impact of Cryopreservation on Split Thickness Skin Grafts in the Porcine Model

Vital, genetically engineered, porcine xenografts represent a promising alternative to human cadaveric allografts (HCA) in the treatment of severe burns. However, their clinical value would be significantly enhanced if preservation and long-term storage-without the loss of cellular viability-were feasible. The objective of this study was to examine the direct impact of cryopreservation and the length of storage on critical in vivo and in vitro parameters, necessary for a successful, potentially equivalent substitute to HCA. In this study, vital, porcine skin grafts, continuously cryopreserved for more than 7 years were compared side-by-side to otherwise identically prepared skin grafts stored for only 15 minutes. Two major histocompatibility complex (MHC)-controlled donor-recipient pairs received surgically created deep-partial wounds and subsequent grafting with split-thickness porcine skin grafts, differentiated only by the duration of storage. Clinical and histological outcomes, as well as quantification of cellular viability via a series of 3-4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT) assays, were assessed. No statistically significant differences were observed between skin grafts cryopreserved for 15 minutes vs 7 years. Parametric distinctions between xenografts stored for short- vs long-term durations could not be ascertained across independent clinical, histological, or in vitro evaluative methods. The results of this study validate the ability to reliably preserve, store, and retain the essential metabolic activity of porcine tissues after cryopreservation. Plentiful, safe, and readily accessible inventories of vital xenografts represent an advantageous solution to numerous limitations associated with HCA, in the treatment of severe burns.

Utility of Porcine-Derived Xenograft as an Adjunct to Split-Thickness Skin Grafting in Lower-Extremity Wounds

OBJECTIVE

Porcine-derived xenograft biological dressings (PXBDs) are occasionally used to prepare chronic wound beds for definitive closure before split-thickness skin grafts (STSGs). We sought to determine whether PXBD influences rate of STSG take in lower-extremity wounds.

METHODS

Lower-extremity wounds treated with STSGs were retrospectively reviewed. Patients were included in one of two groups: wound bed preparation with PXBD before STSG or no preparation. Patients were excluded if they received wound bed preparation via another method. Patient demographics, comorbidities, wound history, wound bed preparation, and 30- and 60-day outcomes were collected.

RESULTS

There was no difference in healing outcomes between the PXBD (n = 27) and no preparation (n = 39) groups. At 30- and 60-day follow-up, percentage of STSG take was not significantly different between groups (77.9% versus 79.0%, P30 = .818; 82.2% versus 80.9%, P60 = .422). Mean wound sizes at these follow-up periods were not different (4.4 cm2 versus 5.1 cm2, P30 = .902; 1.2 cm2 versus 1.1 cm2, P60 = .689). The PXBD group had a higher mean ± SD hemoglobin A1c level (8.3 ± 3.5 versus 6.9 ± 1.6; P = .074) and age (64.9 ± 12.8 years versus 56.3 ± 11.9 years; P = .007) versus the no preparation group.

CONCLUSIONS

Application of PXBDs for wound bed preparation had no effect on wound healing compared with no wound bed preparation. The two groups varied only by mean age and hemoglobin A1c level. The PXBD may be beneficial, but these results call for randomized controlled trials to determine the true impact of PXBDs on wound healing. In addition, PXBDs may have utility outside of clinically oriented outcomes, and future work should address patient-reported outcomes and pain scores with this adjunct.

Porcine Xenograft and Epidermal Fully Synthetic Skin Substitutes in the Treatment of Partial-Thickness Burns: A Literature Review

Background and Objectives: Porcine xenografts have been used successfully in partial thickness burn treatment for many years. Their disappearance from the market led to the search for effective and efficient alternatives. In this article, we examine the synthetic epidermal skin substitute Suprathel^® as a substitute in the treatment of partial thickness burns. Materials and Methods: A systematic review following the PRISMA guidelines has been performed. Sixteen Suprathel^® and 12 porcine xenograft studies could be included. Advantages and disadvantages between the treatments and the studies’ primary endpoints have been investigated qualitatively and quantitatively. Results: Although Suprathel had a nearly six times larger TBSA in their studies (p < 0.001), it showed a significantly lower necessity for skin grafts (p < 0.001), and we found a significantly lower infection rate (p < 0.001) than in Porcine Xenografts. Nonetheless, no significant differences in the healing time (p = 0.67) and the number of dressing changes until complete wound healing (p = 0.139) could be found. Both products reduced pain to various degrees with the impression of a better performance of Suprathel^® on a qualitative level. Porcine xenograft was not recommended for donor sites or coverage of sheet-transplanted keratinocytes, while Suprathel^® was used successfully in both indications. Conclusion: The investigated parameters indicate that Suprathel^® to be an effective replacement for porcine xenografts with even lower subsequent treatment rates. Suprathel^® appears to be usable in an extended range of indications compared to porcine xenograft. Data heterogeneity limited conclusions from the results.

Validation of Three Different Sterilization Methods of Tilapia Skin Dressing: Impact on Microbiological Enumeration and Collagen Content

Tilapia fish skin has demonstrated promise as a stable and practical biological dressing to be used in wound and burn management. However, the appropriate sterilization technique of the Tilapia fish skin is crucial before its clinical application. The standard sterilization technique must eliminate harmful pathogens but maintain the structural and biochemical properties that could compromise the dressing function. This study investigated and compared the efficiency of three sterilizing agents; chlorhexidine gluconate 4% (CHG), povidone iodine 10% (PVP-I), and silver nanoparticles (25 μg/mL) (AgNPs), at three different times (5, 10, and 15 min) on Tilapia fish skin based on the microbial count, histological and collagen properties. Among the sterilization procedures, AgNPs showed rapid and complete antimicrobial activity, with a 100% reduction in microbial growth of the fish skin throughout the treated times. Furthermore, AgNPs did not impair the cellular structure or collagen fibers content of the fish skin. However, CHG and PVP-I caused alterations in the collagen content. This study demonstrated that the AgNPs treatment of Tilapia fish skin provided sterile skin while preserving the histological properties and structural integrity. These findings provide an efficient and quick sterilization method suitable for Tilapia fish skin that could be adopted as a biological dressing.

Use of Tilapia Skin as a Xenograft for Pediatric Burn Treatment: A Case Report

Burns represent the fifth most common cause of nonfatal childhood injuries in the world. The Nile tilapia skin (Oreochromis niloticus) is widely available in Brazil and demonstrated, in previous studies, noninfectious microbiota, morphological structure similar to that of human skin, and good outcomes when used as a xenograft for treatment of experimental burns in rats. A 3-year-old boy was admitted to a burn treatment center in Fortaleza, Brazil, with scalds in the left side of the face, neck, anterior thorax, abdomen, and left arm. Involvement of 18% of total body surface area with superficial partial thickness burns was calculated. After local Institutional Review Board approval and written permission from the patient's legal caregiver were obtained, application of tilapia skin as an occlusive dressing was performed. Good adherence of tilapia skin to the wound bed was detected. The patient was discharged from the hospital with a total of 10 days required for the complete re-epithelialization of his superficial partial thickness burn. No adverse effects were noted. We believe that further studies conducted by our researchers will allow this innovative, low-cost, widely available and easy to apply biomaterial to firm itself as a relevant option in the therapeutic arsenal of pediatric burns, producing significant social and financial impact for the health system.

Lyophilised tilapia skin as a xenograft for superficial partial thickness burns: a novel preparation and storage technique

Despite a considerable decrease in its incidence worldwide, burns remain the fourth most common type of trauma. The majority of burns are small, with 75% of injuries treated on an outpatient basis. Tilapia skin, as a biological material, has been suggested as an option for the management of burn wounds. After good results were obtained with the use of a glycerolised version of tilapia skin in burned children and adults, it was hypothesised that similar outcomes could be achieved with the use of a lyophilised version of tilapia skin. We report the case of a 33-year-old female patient with scalds to the upper abdomen, and both breasts, arms and forearms. Involvement of 10% of total body surface area with superficial partial thickness burns was calculated. The good adherence of tilapia skin to the wound bed, a 10-day period for complete re-epithelialisation of the wounds and the absence of side effects suggested that the lyophilised version of tilapia skin is effective for burn treatment. Compared with glycerolisation, lyophilisation is thought to permit extended storage of sterile tissue and decreased costs related to distribution and transport, but further studies are needed to confirm this.

High porous electrospun poly(ε-caprolactone)/gelatin/MgO scaffolds preseeded with endometrial stem cells promote tissue regeneration in full-thickness skin wounds: An in vivo study

In the current study, electrospun poly(ε-caprolactone)-gelatin (PCL-Gel) fibrous scaffolds containing magnesium oxide (MgO) particles and preseeded with human endometrial stem cells (hEnSCs) were developed to use as wound care material in skin tissue engineering applications. Electrospun fibers were fabricated using PCL-Gel (1:1 [wt/wt]) with different concentrations of MgO particles (1, 2, and 4 wt%). The fibrous scaffolds were evaluated regarding their microstructure, mechanical properties, surface wettability, and in vitro and in vivo performances. The full-thickness excisional wound model was used to evaluate the in vivo wound healing ability of the fabricated scaffolds. Our findings confirmed that the wounds covered with PCL-Gel fibrous scaffolds containing 2 wt% MgO and preseeded with hEnSCs have nearly 79% wound closure ability while sterile gauze showed 11% of wound size reduction. Our results can be employed for biomaterials aimed at the healing of full-thickness skin wounds.

Pediatric Burn Treatment Using Tilapia Skin as a Xenograft for Superficial Partial-Thickness Wounds: A Pilot Study

This study aims to evaluate the efficacy of Nile tilapia skin as a xenograft for the treatment of partial-thickness burn wounds in children. This is an open-label, monocentric, randomized phase II pilot study conducted in Fortaleza, Brazil. The study population consisted of 30 children between the ages of 2 and 12 years with superficial "partial-thickness" burns admitted less than 72 hours from the thermal injury. In the test group, the tilapia skin was applied. In the control group, a thin layer of silver sulfadiazine cream 1% was applied. Tilapia skin showed good adherence to the wound bed, reducing the number of dressing changes required, the amount of anesthetics used, and providing benefits for the patients and also for healthcare professionals, by reducing the overall work load. The number of days to complete burn wound healing, the total amount of analgesics required throughout the treatment, burn improvement on the day of dressing removal, and pain throughout the treatment were similar to the conventional treatment with silver sulfadiazine. Thus, tilapia skin can be considered an effective and low-cost extra resource in the therapeutic arsenal of pediatric superficial partial thickness burns.

Vital, Porcine, Gal-Knockout Skin Transplants Provide Efficacious Temporary Closure of Full-Thickness Wounds: Good Laboratory Practice-Compliant Studies in Nonhuman Primates

Vital, genetically engineered porcine skin transplants have long been regarded as a promising treatment option for severe burn wounds. The objective of this two-part, preclinical study was to evaluate the ability of vital, split-thickness skin xenotransplants derived from designated pathogen-free, alpha 1,3 galactosyltransferase knockout miniature swine to provide temporary wound closure of full-thickness wound defects intended to model severe and extensive, deep partial- and full-thickness burn wounds. In part 1 of the study, four full-thickness wound defects were introduced in four cynomolgus macaques recipients and, then engrafted with two xenografts and two allografts to achieve temporary wound closure. On POD-15, autografts were used to achieve definitive wound closure and were observed until POD-22. In part 2 of the study, four additional subjects each received two full-thickness wound defects, followed by two xenografts to achieve temporary wound closure, and were observed postoperatively for 30 days without further intervention. All grafts were assessed for signs of adherence to the wound bed, vascularity, and signs of immune rejection via gross clinical and histological methods. Xenograft and allograft comparators were equivalent in part 1, and later autografts were otherwise indistinguishable. In part 2, all xenotransplants demonstrated adherence, vascularity, and survival until POD-30. These were unexpected results that exceed previously published findings in similar models. Furthermore, the ensuing GLP-study report directly supported regulatory clearance, permitting a phase I clinical trial. This solution holds great promise as an alternative to human cadaver allograft, the current standard of care for the treatment of severe burns.

Innovative Burn Treatment Using Tilapia Skin as a Xenograft: A Phase II Randomized Controlled Trial

Skin substitutes are considered a useful alternative for occlusive dressings in the treatment of superficial burns as they reduce the frequency of dressing replacement. This phase II randomized controlled trial aimed to evaluate the efficacy of Nile tilapia (Oreochromis niloticus) skin as an occlusive xenograft dressing for the treatment of burn wounds in humans. In order to assess the use of tilapia skin, the following variables were evaluated: number of days for wound healing, the number of times the occlusive dressing was changed, use of anesthetics or analgesics, pain assessment using the Visual Analogue Scale, and evaluation of burn improvement on the day of dressing removal. In total, 62 participants completed the study. It was found that in participants treated with tilapia skin, complete reepithelialization occurred in significantly fewer days; reported pain intensity was lower (study arms B and C), the amount of anesthetics/analgesics required was lower (study arms B and C), and the necessity of dressing changes was significantly reduced in comparison with volunteers treated with silver sulfadiazine. In our study, the tilapia skin xenograft showed good efficacy as an occlusive biological dressing for burn wound treatment in humans.

Topical Delivery of Immunosuppression to Prolong Xenogeneic and Allogeneic Split-Thickness Skin Graft Survival

Cadaveric skin allograft is the current standard of treatment for temporary coverage of large burn wounds. Porcine xenografts are viable alternatives but undergo α-1,3-galactose (Gal)-mediated hyperacute rejection and are lost by post-operative day (POD) 3 because of naturally occurring antibodies to Gal in primate recipients. Using baboons, we previously demonstrated that xenografts from GalT-KO swine (lacking Gal) provided wound coverage comparable with allografts with systemic immunosuppression. In this study, we investigate topical immunosuppression as an alternative to prolong xenograft survival. Full-thickness wounds in baboons were created and covered with xenogeneic and allogeneic split-thickness skin grafts (STSGs). Animals were treated with slow-release (TyroSphere-encapsulated) topical formulations (cyclosporine-A [CSA] or Tacrolimus) applied 1) directly to the STSGs only, or 2) additionally to the wound bed before STSG and 1). Topical CSA did not improve either xenograft or allograft survival (median: treated grafts = 12.5 days, control = 14 days; P = 0.27) with similar results when topical Tacrolimus was used. Pretreatment of wound beds resulted in a significant reduction of xenograft survival compared with controls (10 vs 14 days; P = 0.0002), with comparable results observed in allografts. This observation was associated with marked reduction of inflammation on histology with Tacrolimus and not CSA. Prolongation of allograft and xenograft survival after application to full-thickness wound beds was not achieved with the current formulation of topical immunosuppressants. Modulation of inflammation within the wound bed was effective with Tacrolimus pretreatment before STSG application and may serve as a treatment strategy in related fields.

Small Diameter Xenogeneic Extracellular Matrix Scaffolds for Vascular Applications

Currently, despite the success of percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG) remains among the most commonly performed cardiac surgical procedures in the United States. Unfortunately, the use of autologous grafts in CABG presents a major clinical challenge as complications due to autologous vessel harvest and limited vessel availability pose a significant setback in the success rate of CABG surgeries. Acellular extracellular matrix (ECM) scaffolds derived from xenogeneic vascular tissues have the potential to overcome these challenges, as they offer unlimited availability and sufficient length to serve as "off-the-shelf" CABGs. Unfortunately, regardless of numerous efforts to produce a fully functional small diameter xenogeneic ECM scaffold, the combination of factors required to overcome all failure mechanisms in a single graft remains elusive. This article covers the major failure mechanisms of current xenogeneic small diameter vessel ECM scaffolds, and reviews the recent advances in the field to overcome these failure mechanisms and ultimately develop a small diameter ECM xenogeneic scaffold for CABG. Impact Statement Currently, the use of autologous vessel in coronary artery bypass graft (CABG) is common practice. However, the use of autologous tissue poses significant complications due to tissue harvest and limited availability. Developing an alternative vessel for use in CABG can potentially increase the success rate of CABG surgery by eliminating complications related to the use of autologous vessel. However, this development has been hindered by an array of failure mechanisms that currently have not been overcome. This article describes the currently identified failure mechanisms of small diameter vascular xenogeneic extracellular matrix scaffolds and reviews current research targeted to overcoming these failure mechanisms toward ensuring long-term graft patency.

Superiority of silver-foam over porcine xenograft dressings for treatment of scalds in children: A prospective randomised controlled trial

AIM

Our aim was to compare two different regimens for the treatment of children with partial-thickness scalds. These were treated with either a porcine xenograft (EZderm^®, Mölnlycke Health Care, Gothenburg, Sweden) or a silver-foam dressing (Mepilex^® Ag, Mölnlycke Health Care, Gothenburg, Sweden).

METHODS

We organised a prospective randomised clinical trial that included 58 children admitted between May 2015 and May 2018 with partial-thickness scalds to The Burn Centre in Linkoping, Sweden. The primary outcome was time to healing. Secondary outcomes were pain, need for operation, wound infection, duration of hospital stay, changes of dressings, and time taken.

RESULTS

The patients treated with silver-foam dressing had a significantly shorter healing time. The median time to 97% healing for this group was 9 (7-23) days compared to 15 (9-29) days in the porcine xenograft group (p = 0.004). The median time to complete healing for the silver-foam group was 15 (9-29) days and for the porcine xenograft group 20.5 (11-42) days (p = 0.010). Pain, wound infection, duration of hospital stay, and the proportion of operations were similar between the groups. Number of dressing changes and time for dressing changes were lower in the silver-foam dressing group (p = 0.03 for both variables).

CONCLUSIONS

We compared two different treatments for children with partial-thickness scalds, and the data indicate that wound healing was faster, fewer dressing changes were needed, and dressing times were shorter in the silver-foam group.

Three Years' Experience of a Novel Biosynthetic Cellulose Dressing in Burns

Objective: The use of porcine xenograft (PX) is widely spread in burn care. However, it may cause immunologic responses and other ethical and cultural considerations in different cultures. Therefore, there is a need for alternatives. The aim of this work is to test a novel biosynthetic cellulose dressing (Epiprotect^®) on burn patients.

Approach: Charts from 38 patients with superficial burns (SBs) (n = 18) or excised burns (n = 20) that got biosynthetic cellulose dressing instead of PX at a national burn center during 3 years were reviewed. Time to healing, length of stay, and wound infection were extracted from the medical records.

Results: SBs hospitalization time was 11 days comparable to PXs reported by others. In the excised group, median duration of hospital stay was 35 days. Time to healing was 28 days. Seven wound infections were confirmed in the superficial group (39%) and 11 infections in the excised group (61%). Patients with superficial wounds reported pain relief on application.

Innovation: A dressing (17 × 21 cm) consisting of biosynthetic cellulose replacing PX.

Conclusion: Outcome of treatment of SBs or temporary coverage of excised deep burns with biosynthetic cellulose is comparable to treatment with PX. However, biosynthetic cellulose has benefits such as providing pain relief on application and ethical or cultural issues with the material is nonexistent.

Triplet Excited Carbonyls and Singlet Oxygen Formation During Oxidative Radical Reaction in Skin

The skin is the largest organ in the body and is consistently exposed to aggressive environmental attacks (biological/physical/chemical, etc.). Reactive oxygen species (ROS) are formed during the normal oxidative metabolism which enhances to a lethal level under stress conditions referred to as oxidative stress. While, under normal conditions, cells are capable of dealing with ROS using non-enzymatic and enzymatic defense system, it can lead to a critical damage to cell system via the oxidation of cellular components under stress condition. Lipid peroxidation is a well-established mechanism of cellular injury in all kinds of organisms and it is often used as an indicator of oxidative stress in cells and tissues. In the presence of metal ions, ROS such as hydrogen peroxide (H₂O₂) produces highly reactive hydroxyl radical (HO^•) via Fenton reaction. In the current study, we have used the porcine skin (intact pig ear/skin biopsies) as an ex vivo/in vitro model system to represent human skin. Experimental results have been presented on the participation of HO^• in the initiation of lipid peroxidation and thereby leading to the formation of reactive intermediates and the formation of electronically excited species eventually leading to ultra-weak photon emission (UPE). To understand the participation of different electronically excited species in the overall UPE, the effect of a scavenger of singlet oxygen (¹O₂) on photon emission in the visible and near-infrared region of the spectrum was measured which showed its contribution. In addition, measurement with interference filter with a transmission in the range of 340-540 nm reflected a substantial contribution of triplet carbonyls (³L=O^∗) in the photon emission. Thus, it is concluded that during the oxidative radical reactions, the UPE is contributed by the formation of both ³L=O^∗ and ¹O₂. The method used in the current study is claimed to be a potential tool for non-invasive determination of the physiological and pathological state of human skin in dermatological research.

Skin xenotransplantation: Historical review and clinical potential

Half a million patients in the USA alone require treatment for burns annually. Following an extensive burn, it may not be possible to provide sufficient autografts in a single setting. Pig skin xenografts may provide temporary coverage. However, preformed xenoreactive antibodies in the human recipient activate complement, and thus result in rapid rejection of the graft. Because burn patients usually have some degree of immune dysfunction and are therefore at increased risk of infection, immunosuppressive therapy is undesirable. Genetic engineering of the pig has increased the survival of pig heart, kidney, islet, and corneal grafts in immunosuppressed non-human primates from minutes to months or occasionally years. We summarize the current status of research into skin xenotransplantation for burns, with special emphasis on developments in genetic engineering of pigs to protect the graft from immunological injury. A genetically-engineered pig skin graft now survives as long as an allograft and, importantly, rejection of a skin xenograft is not detrimental to a subsequent allograft. Nevertheless, currently, systemic immunosuppressive therapy would still be required to inhibit a cellular response, and so we discuss what further genetic manipulations could be carried out to inhibit the cellular response.

Split-thickness skin grafting: early outcomes of a clinical trial using different graft thickness

OBJECTIVE

In clinical practice, split-thickness skin graft (STSG) transplantation remains the gold standard for covering large skin defects. Currently, there is no consensus on the optimal thickness of skin grafts. The purpose of our study was to compare the early healing processes of recipient and donor wounds after STSG transplantation using grafts of different thickness.

METHOD

This prospective, randomised clinical trial included 84 patients that underwent STSG transplantation surgery for post-burn, post-traumatic or postoperative skin defects. Patients were randomised to receive a skin graft of either 0.2mm, 0.3mm or 0.4mm thickness. After skin transplantation, the wound healing parameters of both the recipient and donor wounds were evaluated after three days, one week, two weeks and one month.

RESULTS

The greatest mean epithelialisation scores and highest rate of complete wound epithelialisation were identified in the recipient and donor wounds of the 0.2mm transplant group, at all time points. When the recipient wound pain scores were evaluated, the greatest visual analogue scale (VAS) values were found in the 0.2mm transplant group. The opposite result was found for the donor wound, where the highest VAS scores were identified in the 0.4mm transplant group. There were no significant differences, at any follow-up period, when wound secretion, erythema, swelling, localised warmth and fluctuation were compared.

CONCLUSION

The early healing of recipient wounds after STSG transplantation with grafts of various thickness differed considerably, especially regarding wound epithelialisation and pain.

Stem cells, niches and scaffolds: Applications to burns and wound care

The importance of skin to survival, and the devastating physical and psychological consequences of scarring following reparative healing of extensive or difficult to heal human wounds, cannot be disputed. We discuss the significant challenges faced by patients and healthcare providers alike in treating these wounds. New state of the art technologies have provided remarkable insights into the role of skin stem and progenitor cells and their niches in maintaining skin homeostasis and in reparative wound healing. Based on this knowledge, we examine different approaches to repair extensive burn injury and chronic wounds, including full and split thickness skin grafts, temporising matrices and scaffolds, and composite cultured skin products. Notable developments include next generation skin substitutes to replace split thickness skin autografts and next generation gene editing coupled with cell therapies to treat genodermatoses. Further refinements are predicted with the advent of bioprinting technologies, and newly defined biomaterials and autologous cell sources that can be engineered to more accurately replicate human skin architecture, function and cosmesis. These advances will undoubtedly improve quality of life for patients with extensive burns and difficult to heal wounds.

Even Better Than the Real Thing? Xenografting in Pediatric Patients with Scald Injury

This article reviews a single burn center experience with porcine xenografts to treat pediatric scald injuries, over a 10-year period. The authors compare xenografting to autografting, as well as wound care only, and provide outcome data on length of stay, incidence of health care-associated infections, and need for reconstructive surgery.

Use of Porcine Xenografts in Dermatology Surgery: The Mayo Clinic Experience

BACKGROUND

Knowledge regarding the use of xenografts in cutaneous surgery is limited.

OBJECTIVE

We sought to better understand the utility, outcomes, and complications of porcine xenograft applications in cutaneous surgery.

METHODS AND MATERIALS

A single center, retrospective study of patients with porcine xenograft applications was completed. Characteristics of tumors, surgical procedures, resulting wound beds, follow-up care, and final length of follow-up were determined, and statistical analysis was conducted.

RESULTS

Of 225 porcine xenograft placements in 220 patients, the majority of tumors were nonmelanoma skin cancers (89%) and similarly divided between the head (excepting nose/ear), nose, ear, and extremities. Both Mohs and standard excision resulted in a 5.7 cm mean area of surgical defect, with the majority closed by porcine xenograft only (84.1%), and healing by secondary intention (97.3%). The area of surgical defect and topical antibiotics contributed to increased length of time to final follow-up.

CONCLUSION

The data represent the largest series of biologic dressings in cutaneous surgery and demonstrate the applicability and safety of porcine xenografts. We recommend consideration of porcine xenografts in the appropriate clinical context, to augment secondary intention.

New Innovations for Deep Partial-Thickness Burn Treatment with ACell MatriStem Matrix

Objective: Burn injuries remain a large financial burden on the healthcare system. According to CDC statistics (2010), nonfatal and hospitalized burns in the U.S. cost $1.8 billion for an annual incidence of ∼486,000 cases. To date, no technique proves to be the ideal therapy of deep partial-thickness burns. In this study, we review a trial usage of ACell (ACell, Inc.) wound matrix on deep partial-thickness burns. Approach: Burn patients were admitted through the Vanderbilt Emergency Department. Three were consented to receive ACell therapy. Each patient suffered extremity burns, to which ACell MatriStem matrix was applied. Time to epithelialization and healing was monitored up to 1 month postintervention. Results: ACell MatriStem matrix use in deep partial-thickness burns enabled healing by 29 days on average without requiring autografts. The average total body surface area (TBSA) of injury was 7.2% with average TBSA treated with ACell equal to 2.5%. All burn sites underwent re-epithelialization after 5.6 days on average (range 4-7 days). Average length of stay after ACell placement totaled 2 days. All patients fully healed without the need for subsequent grafting or contracture development. No postoperative complications were noted. Innovation: To the extent of our knowledge, this is one of the first reported series to utilize ACell MatriStem product in deep partial-thickness extremity burns. Conclusion: Despite numerous products currently available for burn reconstruction, no one product embodies all the characteristics of an ideal graft. ACell biological extracellular matrix scaffolding appears promising, allowing for healing without use of an autograft.

Future Prospects for Scaffolding Methods and Biomaterials in Skin Tissue Engineering: A Review

Over centuries, the field of regenerative skin tissue engineering has had several advancements to facilitate faster wound healing and thereby restoration of skin. Skin tissue regeneration is mainly based on the use of suitable scaffold matrices. There are several scaffold types, such as porous, fibrous, microsphere, hydrogel, composite and acellular, etc., with discrete advantages and disadvantages. These scaffolds are either made up of highly biocompatible natural biomaterials, such as collagen, chitosan, etc., or synthetic materials, such as polycaprolactone (PCL), and poly-ethylene-glycol (PEG), etc. Composite scaffolds, which are a combination of natural or synthetic biomaterials, are highly biocompatible with improved tensile strength for effective skin tissue regeneration. Appropriate knowledge of the properties, advantages and disadvantages of various biomaterials and scaffolds will accelerate the production of suitable scaffolds for skin tissue regeneration applications. At the same time, emphasis on some of the leading challenges in the field of skin tissue engineering, such as cell interaction with scaffolds, faster cellular proliferation/differentiation, and vascularization of engineered tissues, is inevitable. In this review, we discuss various types of scaffolding approaches and biomaterials used in the field of skin tissue engineering and more importantly their future prospects in skin tissue regeneration efforts.

The use of porcine xenografts in patients with toxic epidermal necrolysis

INTRODUCTION

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) can be challenging to treat due to pain with wound care and ongoing fluid loss. The purpose of this study is to determine the role of porcine xenograft as a modality for wound coverage.

MATERIAL AND METHODS

A retrospective review from 2006 to 2014 was performed at a regional burn center on all patients admitted with the diagnosis of SJS (<10% TBSA involvement), SJS/TEN overlap (10-30% TBSA involvement), and TEN (>30% TBSA involvement). Patients who received porcine xenograft had physiologic and biochemical parameters compared in the 24h before and after graft placement. In addition, xenograft patients were compared to historical controls that received traditional wound care which included silver impregnated dressings. Outcomes and variables collected included intravenous fluid given, urine output, pain scores (1-10), pain medication for wound care, biochemical markers, skin infections, hospital length of stay, and mortality.

RESULTS

Eight patients had placement of a porcine xenograft. Median age was 50 years (IQR 41, 66) and 2 were male. Median % TBSA affected was 76 (IQR 64, 80). The median amount of fluid (ml/kg/day/%TBSA) administered decreased from 1.45 (IQR 1.03, 1.78) to 0.9 (IQR 0.65, 1.08) after xenograft placement (p=0.02). The median amount of intravenous fluid (ml/kg/day/%TBSA) administered in the treatment group and historical control group was 0.9 (IQR 0.65, 1.08) and 0.8 (IQR 0.7, 1.47) respectively (p=0.72). The median amount of urine output (ml/kg/day) in the treatment group and historical control group was 34.2 (IQR 22, 44.38) and 22 (IQR 11.25, 38.13) respectively (p=0.17). Pain scores significantly decreased from 5.5 (IQR 2.5, 8.25) pre-xenograft to 2.8 (IQR 0.75, 4) post-xenograft placement (p=0.03). There was a significant difference in pain scores between the treatment group and historical control group, 2.8 (IQR 0.75, 4) and 6 (IQR 5, 8) respectively (p=0.02). Each study patient underwent moderate sedation for wound care prior to xenograft placement and one study patient required one moderate sedation for wound care after xenograft placement. One patient in the xenograft placement group was diagnosed with a cutaneous infection compared to 4 patients in the historical control group (p=0.63). The mortality was 12.5% in each group.

CONCLUSIONS

Placement of a porcine xenograft in patients with SJS, SJS/TEN overlap, or TEN is associated with a significant reduction in intravenous fluid use, pain scores, and pain medication. Further study with larger sample sizes is warranted to evaluate for statistically significant differences in outcomes after porcine xenograft placement for SJS, SJS/TEN overlap or TEN.

Novel expansion techniques for skin grafts

The quest for skin expansion is not restricted to cover a large area alone, but to produce acceptable uniform surfaces, robust engraftment to withstand mechanical shear and infection, with a minimal donor morbidity. Ease of the technique, shorter healing period and reproducible results are essential parameters to adopt novel techniques. Significant advances seen in four fronts of autologous grafting are: (1) Dermal-epidermal graft expansion techniques, (2) epidermal graft harvests technique, (3) melanocyte-rich basal cell therapy for vitiligo and (4) robust and faster autologous cell cultures. Meek's original concept that the sum of perimeter of smaller grafts is larger than the harvested graft, and smaller the graft size, the greater is the potential for regeneration is witnessed in newer modification. Further, as graft size becomes smaller or minced, these micrografts can survive on the wound bed exudate irrespective of their dermal orientation. Expansion produced by 4 mm × 4 mm sized Meek micrografts is 10-folds, similarly 0.8 mm × 0.8 mm size micrografts produce 100-fold expansion, which becomes 700-fold with pixel grafts of 0.3 mm × 0.3 mm size. Fractional skin harvest is another new technique with 700 μ size full thickness graft. These provide instant autologous non-cultured graft to cover extensive areas with similar quality of engraftment surface as split skin grafts. Newer tools for epidermal blister graft harvest quickly, with uniform size to produce 7-fold expansions with reproducible results. In addition, donor area heals faster with minimal scar. Melanocyte-rich cell suspension is utilised in vitiligo surgery tapping the potential of hair root melanocytes. Further advances in the cell culture to reduce the cultivation time and provide stronger epidermal sheets with dermal carrier are seen in trials.

A novel dermal matrix generated from burned skin as a promising substitute for deep-degree burns therapy

The extensive skin defects induced by severe burns are dangerous and can be fatal. Currently, the most common therapy is tangential excision to remove the necrotic or denatured areas of skin, followed by skin grafting. Xenogeneic dermal substitutes, such as porcine acellular dermal matrix (ADM), are typically used to cover the burn wounds, and may accelerate wound healing. It is assumed that burned skin that still maintains partial biological activity may be recycled to construct an autologous acellular dermal matrix, termed 'deep‑degree burned dermal matrix (DDBDM)'. In theory, DDBDM may avoid the histoincompatibility issues associated with foreign or xenogeneic dermal matrices, and reduce therapy costs by making full use of discarded skin. In the present study, the collagens within prepared DDBDM were thickened, disorganized and partially fractured, however, they still maintained their reticular structure and tensile strength (P<0.01). Through microarray analysis of the cytokines present in ADM and DDBDM, it was determined that the DDBDM did not produce excessive levels of harmful burn toxins. Following 4 weeks of subcutaneous implantation, ADM and DDBDM were incompletely degraded and maintained good integrity. No significant inflammatory reaction or rejection were observed, which indicated that ADM and DDBDM have good histocompatibility. Therefore, DDBDM may be a useful material for the treatment of deep‑degree burns.

Gingival Mesenchymal Stem Cell (GMSC) Delivery System Based on RGD-Coupled Alginate Hydrogel with Antimicrobial Properties: A Novel Treatment Modality for Peri-Implantitis

PURPOSE

Peri-implantitis is one of the most common inflammatory complications in dental implantology. Similar to periodontitis, in peri-implantitis, destructive inflammatory changes take place in the tissues surrounding a dental implant. Bacterial flora at the failing implant sites resemble the pathogens in periodontal disease and consist of Gram-negative anaerobic bacteria including Aggregatibacter actinomycetemcomitans (Aa). Here we demonstrate the effectiveness of a silver lactate (SL)-containing RGD-coupled alginate hydrogel scaffold as a promising stem cell delivery vehicle with antimicrobial properties.

MATERIALS AND METHODS

Gingival mesenchymal stem cells (GMSCs) or human bone marrow mesenchymal stem cells (hBMMSCs) were encapsulated in SL-loaded alginate hydrogel microspheres. Stem cell viability, proliferation, and osteo-differentiation capacity were analyzed.

RESULTS

Our results showed that SL exhibited antimicrobial properties against Aa in a dose-dependent manner, with 0.50 mg/ml showing the greatest antimicrobial properties while still maintaining cell viability. At this concentration, SL-containing alginate hydrogel was able to inhibit Aa growth on the surface of Ti discs and significantly reduce the bacterial load in Aa suspensions. Silver ions were effectively released from the SL-loaded alginate microspheres for up to 2 weeks. Osteogenic differentiation of GMSCs and hBMMSCs encapsulated in the SL-loaded alginate microspheres were confirmed by the intense mineral matrix deposition and high expression of osteogenesis-related genes.

CONCLUSION

Taken together, our findings confirm that GMSCs encapsulated in RGD-modified alginate hydrogel containing SL show promise for bone tissue engineering with antimicrobial properties against Aa bacteria in vitro.

Evaluation of Antimicrobial and Healing Activities of Frog Skin on Guinea Pigs Wounds

Background:

Frog skin secretions have potentials against a wide spectrum of bacteria. Also, frog skin compositions have healing properties.

Objectives:

The aim of this study was to investigate the antibacterial potentials along with healing properties of frog skin Rana ridibunda, a species which thoroughly lives in Iran marshes, as a biological dressing on wounds.

Materials and Methods:

In this study, excisional wounds, dressed with frog skin, were compared between experimental and control groups of guinea pigs. In the experimental groups, wounds were dressed with the dermal (FS) and epidermal (RFS) sides of fresh frog R. ridibunda skin, while only usual cotton gauze covered the wounds of the control group. Furthermore, microbial samples were taken on different days (0, 3, 5, and 7 days post injury) to count the number of the colony-forming units. Additionally, the microbial penetration test was performed on frog skin and then the progression of wound closure was evaluated.

Results:

In the microbial studies, the bacterial load considerably declined in the wounds treated with FS and RFS compared with the control wounds. On day 7 post injury, the numbers of the colony-forming units for the FS, RFS, and control groups were 6.75, 105, and 375, respectively. In the penetration test, fresh frog skin showed to be a bacterial resistant dressing. The results revealed that the rate of wound closure in the experimental groups significantly was accelerated in comparison with that in the control group.

Conclusions:

Our results demonstrated the antimicrobial properties of frog skin as a wound dressing, which has antimicrobial effects per se. This biological dressing shows promise as an effective biological wound dressing insofar as not only is it capable of resisting microbes and accelerating wound healing but also it is cost-effective and easy to use.

Microporous dermal-mimetic electrospun scaffolds pre-seeded with fibroblasts promote tissue regeneration in full-thickness skin wounds

Electrospun scaffolds serve as promising substrates for tissue repair due to their nanofibrous architecture and amenability to tailoring of chemical composition. In this study, the regenerative potential of a microporous electrospun scaffold pre-seeded with dermal fibroblasts was evaluated. Previously we reported that a 70% collagen I and 30% poly(Ɛ-caprolactone) electrospun scaffold (70:30 col/PCL) containing 160 μm diameter pores had favorable mechanical properties, supported fibroblast infiltration and subsequent cell-mediated deposition of extracellular matrix (ECM), and promoted more rapid and effective in vivo skin regeneration when compared to scaffolds lacking micropores. In the current study we tested the hypothesis that the efficacy of the 70:30 col/PCL microporous scaffolds could be further enhanced by seeding scaffolds with dermal fibroblasts prior to implantation into skin wounds. To address this hypothesis, a Fischer 344 (F344) rat syngeneic model was employed. In vitro studies showed that dermal fibroblasts isolated from F344 rat skin were able to adhere and proliferate on 70:30 col/PCL microporous scaffolds, and the cells also filled the 160 μm pores with native ECM proteins such as collagen I and fibronectin. Additionally, scaffolds seeded with F344 fibroblasts exhibited a low rate of contraction (~14%) over a 21 day time frame. To assess regenerative potential, scaffolds with or without seeded F344 dermal fibroblasts were implanted into full thickness, critical size defects created in F344 hosts. Specifically, we compared: microporous scaffolds containing fibroblasts seeded for 4 days; scaffolds containing fibroblasts seeded for only 1 day; acellular microporous scaffolds; and a sham wound (no scaffold). Scaffolds containing fibroblasts seeded for 4 days had the best response of all treatment groups with respect to accelerated wound healing, a more normal-appearing dermal matrix structure, and hair follicle regeneration. Collectively these results suggest that microporous electrospun scaffolds pre-seeded with fibroblasts promote greater wound-healing than acellular scaffolds.