Skin Graft Survival Research Articles

PRP improves the outcomes of autologous skin graft transplantation on the esophagus by promoting angiogenesis and inhibiting fibrosis and inflammation.

Autologous skin graft (ASG) transplantation is a challenging approach but a promising option for patients to prevent postoperative esophageal stricture. Nonetheless, the current strategies require improvement. We aimed to investigate the effectiveness of the injection of platelet-rich plasma (PRP) before skin graft transplantation for extensive esophageal defects after endoscopic resection. Standardized complete circular endoscopic resection (5 cm in length) was performed in 27 pigs allocated into 3 groups. The artificial ulcers were treated with a fully covered esophageal stent (control group), ASG (ASG group), and submucosal injection of PRP with ASG (PRP-ASG group). Macroscopic evaluation and histological analysis of the remolded esophagus were performed 7, 14, and 28 days after surgery. The macroscopic evaluation indicated that submucosal injection of PRP before transplantation effectively promoted the survival rate of skin grafts and decreased the rate of mucosal contraction compared with those treated with ASG or stent alone. Histological analysis of submucosal tissue showed that this modified strategy significantly promoted wound healing of reconstructed tissues by enhancing angiogenesis, facilitating collagen deposition, and decreasing inflammation and fibrogenesis. These findings suggested that PRP might be used as a biological supplement to increase the esophageal skin graft survival rate and improve submucosal tissue remolding in a clinically relevant porcine model. With extremely low mucosal contraction, this novel combination strategy showed the potential to effectively prevent stenosis in extensive esophageal ulcers.

A retrospective, single-center 4-year review of synthetic polyurethane matrix use in burns and other complex wounds

Here we describe the use of a synthetic polyurethane matrix in the setting of burns and other complex wounds in the largest United States case series to date. A retrospective review was conducted at a verified, regional burn center. All patients greater than 18 years of age who received this matrix between January 2019 and July 2023 were included. A total of 182 patients with 250 wounds were included in this study. Thirty-seven percent were smokers, 23.6 % had diabetes and 5.5 % had peripheral vascular disease. The majority were acute burn wounds (60 %), followed by trauma (24.4 %), chronic wounds (5.6 %), infection (4 %) and donor sites (2 %). Exposed structures included fat (54 %), muscle (30 %), bone (16 %) and tendon (14.4 %). Microbial colonization was present in 143 (57.2 %) of cases: 98 (39.2 %) pre-application and 89 (35.6 %) post application. The incidence of new microbial colonisation post-application was 25.6 %. Infection was present in 117 (46.8 %) cases, 49 (19.6 %) pre-matrix application, 44 (17.6 %) post-matrix application and 24 (9.6 %) pre and post application. Eighteen patients (10 %) died. Median length of stay was 27 days. Median time to matrix implantation was 10 days. Median time from matrix placement to skin grafting was 35 days. Where documented, there were 162 wounds (83.5 %) with > 95 % matrix survival and 136 wounds (82.4 %) with > 95 % skin graft survival even in the setting of adverse factors such as infection, diabetes, or nicotine use. This study demonstrates the robustness of this skin substitute to achieve successful reconstruction even in the setting of adverse patient or wound characteristics.

Adipose-derived stem cells transplantation improves survival and alleviates contraction of skin grafts via promoting macrophages M2 polarization.

Full-thickness skin grafts are widely used in plastic and reconstructive surgery. The main limitation of skin grafting is the poor textural durability and associated contracture, which often needs further corrective surgery. Excessive inflammation is the main reason for skin graft contractions, which involve overactivation of myofibroblasts. These problems have prompted the development of new therapeutic approaches, including macrophage polarization modulation and stem cell-based therapies. Currently, adipose-derived stem cells (ASCs) have shown promise in promoting skin grafts survival and regulating macrophage phenotypes. However, the roles of ASCs on macrophages in decreasing skin grafts contraction remain unknown. Rat adipose-derived stem cells (rASCs) were isolated from rat inguinal adipose tissues. Full-thickness skin graft model was constructed on male rats divided into control group and rASCs treatment group. Skin graft was assessed for concentration, elasticity modulus and stiffness. Rat bone marrow-derived macrophages (rBMDMs) were isolated from rat femurs, and subsequent RT-qPCR and coculture assays were carried out to explore the cellular mechanisms. Immunohistochemical and immunofluorescence staining were used to verify mechanisms in vivo. In vivo results showed that after injection of ASCs, improved texture, increased survival and inhibited contraction of skin grafts were seen. Vascularization was also improved as illustrated by laser perfusion image and vascular endothelial growth factor (VEGF) concentration. Histological analysis revealed that ASCs injection significantly reduced expression of pro-inflammatory cytokines (TNF-a, IL-1β) and increased expression of anti-inflammatory (IL-10) and pro-healing cytokines (IGF-1). At cellular level, after co-culturing with rASCs, rat bone marrow derived macrophages (rBMDMs) favored M2 polarization even under inflammatory stimulus. ASCs treatment enhanced vascularization via angiogenic cytokines secretion and alleviated inflammatory environment in skin grafts by driving M2 macrophages polarization, which improved survival and decreased skin grafts contraction. Our work showed that ASCs transplantation can be harnessed to enhance therapeutic efficacy of skin grafting in cutaneous defects treatment.

Study of the Influencing Factors and their Predictive Value of Skin Graft Take in Early Excision and Grafting in Severe Burns: A Prospective Study

Abstract Background Burn injury is one of the most life-threatening traumas worldwide especially in developing countries. After severe burns, the patients suffer from loss of multiple functions of skin, such as fluid loss, and high infection rate with burn sepsis and septic shock. Objective To investigate the various factors that affect the survival rate of skin grafts in early excision and grafting procedures (from 3rd to 7th day after burn) in patients with severe burns. Patients and Methods This Prospective cohort study was done in Ain Shams University Burn Center attached to Plastic, burn and maxillofacial department during the period from May 2021 to May 2022. Results Analysis was performed on 75 individuals who had early burnt skin excised and early skin graft coverage. Two patient groups were analyzed, in the form of good skin graft take >70% in 45 patients, and poor skin graft take < 70% in 30 cases, based on the survival rate of the skin graft post operatively. Conclusion The univariate analysis and repeated measurement showed that burn intensity, the post-operative sepsis, the neutrophil lymphocytic ratio on day 3 (NLR3) in the poor skin graft take group were significantly higher than those in the good skin graft take group, while the estimated albumin levels in perioperative period and the estimated pre-albumin levels in perioperative period were higher in the good skin graft take group. Receiver operating characteristic curve showed that NLR3, the estimated albumin levels and pre-albumin levels in perioperative period had a good predictive value for the survival of skin grafts. The estimated albumin levels ≤3.18 gm/dl, estimated pre-albumin ≤23.9 mg/dl, and NLR3 ≥ 12 were independent risk factors for graft take in perioperative period.

Continuous negative-pressure wound therapy improves the survival rate of skin grafts and shortens the time required for skin graft survival.

The effectiveness of negative-pressure wound therapy (NPWT) in skin graft fixation has been demonstrated in several clinical studies. However, in vitro and in vivo studies on skin graft fixation with NPWT have been scarce. In this in vivo study, we aimed to determine whether NPWT fixation enhances skin graft survival and how it contributes to improving skin graft survival biologically. We harvested skin from the bilateral abdominal wall of 88 mice after anesthetizing them. Full-thickness skin grafts (FTSGs) were performed on contralateral harvest sites, and grafts were fixed using NPWT (continuous and intermittent modes), conventional compression methods, and wrapping with polyurethane foam as a control group. On days 5 and 10 of grafting, the survival rates of the FTSGs were evaluated. Immunohistopathological analysis and measurement of the expression levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2), and epidermal growth factor (EGF) were performed. The survival rates of FTSG in the continuous NPWT group were significantly higher than those in the other groups. The number of capillaries in the dermis was significantly higher in the continuous NPWT group than in the other groups. In the wound bed, VEGF levels were significantly higher in both NPWT groups than in the other groups. Continuous NPWT increases the survival rate of FTSGs and shortens the duration of skin graft survival.

Adoptive Cell Therapy in Mice Sensitized to a Grass Pollen Allergen.

The proportion of patients with type I allergy in the world population has been increasing and with it the number of people suffering from allergic symptoms. Recently we showed that prophylactic cell therapy employing allergen-expressing bone marrow (BM) cells or splenic B cells induced allergen-specific tolerance in naïve mice. Here we investigated if cell therapy can modulate an established secondary allergen-specific immune response in pre-immunized mice. We sensitized mice against the grass pollen allergen Phl p 5 and an unrelated control allergen, Bet v 1, from birch pollen before the transfer of Phl p 5-expressing BM cells. Mice were conditioned with several combinations of low-dose irradiation, costimulation blockade, rapamycin and T cell-depleting anti-thymocyte globulin (ATG). Levels of allergen-specific IgE and IgG1 in serum after cell transfer were measured via ELISA and alterations in cellular responses were measured via an in vitro proliferation assay and transplantation of Phl p 5+ skin grafts. None of the tested treatment protocols impacted Phl p 5-specific antibody levels. Transient low-level chimerism of Phl p 5+ leukocytes as well as a markedly prolonged skin graft survival were observed in mice conditioned with high numbers of Phl p 5+ BMC or no sensitization events between the day of cell therapy and skin grafting. The data presented herein demonstrate that a pre-existing secondary allergen-specific immune response poses a substantial hurdle opposing tolerization through cell therapy and underscore the importance of prophylactic approaches for the prevention of IgE-mediated allergy.

Tetrahedral framework nucleic acids’ role in facilitating chronic diabetic wound repair via the endoplasmic reticulum-mitochondrial pathway

Under diabetic circumstances, keratinocytes are constantly exposed to hyperglycaemic micromilieu, leading to disrupted differentiation and increased chronic wound susceptibility during to sustained endoplasmic reticulum (ER) stress (ERS) and mitochondrial dysfunction during hyperglycaemia. As mitochondrial respiratory chain activity is a primary generator of intracellular reactive oxygen species (ROS), we postulated that tFNAs could potentially boost mitochondrial function and energy metabolism in the presence of oxidative stress. To this end, we first explored the ER-mitochondrial (ER-MITO) axis-associated intracellular transportation of tetrahedral framework nucleic acids (tFNAs). tFNAs are transported to the ER and mitochondria via caveolae-mediated endocytosis, thereby regulating the ER-MITO axis. Additionally, tFNAs reduce ERS by downregulating PERK-ATF 4-CHOP, thereby stabilising mitochondrial dynamics, improving energy metabolism, maintaining membrane potential polarisation, and scavenging generated reactive oxygen species to counteract oxidative stress during hyperglycaemia. Consequently, tFNAs restore cell proliferation, migration, and differentiation and enhance chronic wound healing and skin graft survival. Furthermore, tFNAs repaired the diabetic skin mechanical barrier, underscoring their versatility of ER-MITO axis modulation. Overall, this study highlights the importance of tFNAs in ER-MITO axis modulation and a novel therapeutic approach for chronic diabetic wound healing.

Management of Immobile Scalp Skin Tumors and Analysis of Skin Graft Survival on Burred Calvaria.

Surgeons face challenges associated with adherent cutaneous scalp malignancy. Traditional general anesthetic excision involves periosteal removal and burring of the outer table of the calvaria for deep margin clarity and tissue reconstruction. Research on this practice is limited, and graft survival in burr-treated bones is underexplored. This study aimed to assess the clinical margin accuracy for immobile scalp malignancies, identify deep-invading malignancy types, and evaluate graft survival in burr-treated calvariae. It compares split-thickness grafts (STSGs) and full-thickness grafts (FTSGs). Twelve fixed scalp malignancies were excised under anesthesia, allowing immediate STSG or FTSG for defect reconstruction. Postsurgery, graft take, malignancy type, and margin clearance were evaluated. Histopathological diagnosis identified seven squamous cell carcinomas, two melanomas, one basal cell carcinoma, one adenocarcinoma, and one metastatic squamous cell carcinoma. Deep margins ranged from 0 to 0.9 mm, and peripheral margins ranged from 0 to 15 mm. The graft take was 100% in eight cases, with total failure in two cases, and 75%-90% in two cases. The five STSGs had 100% take and 90% take. The three FTSGs had 100%, 75%, and two failed. Clinical examination effectively gauges the tumor fixation depth, but large lesions may require imaging. Most deep-invading tumors were SCCs. STSGs performed better on burr-treated Calvaria than FTSGs.

Efficacy of hydrosurgical eschar excision following MEEK microskin grafting in patients with massive burns: A retrospective study of a single center

IntroductionOne of the most common traumatic injuries, burn injuries lead to at least 180,000 deaths each year worldwide. Massive burns result in severe tissue loss and increase the rate of infection. Eschar excision with skin grafting is the gold standard of treatments for massive burns. Retaining dermis tissue is the key to ensuring the survival of skin grafts and rapidly closing exposed tissues. Traditional eschar excision with Humby or Weck knife controls the depth of excision until the dermis, but ensuring the accuracy of excision is challenging. Hydrosurgery minimizes damage to uninjured tissues during the removal of necrotic tissues. A foot pedal is used to adjust debridement depth for precise debridement. To figure out the clinical advantages and risks of using hydrosurgery in treating massive burns, this study has been conducted. MethodForty-two patients with massive burns and total body surface area (TBSA) of > 30% were treated at the First Affiliated Hospital of Anhui Medical University from May 2020 to January 2023. They underwent hydrosurgical eschar excision with MEEK microskin graft (n = 23) or tangential excision with MEEK microskin graft (n = 19). ResultNo statistically significant differences (p > 0.05) in the following demographics were found between the two groups: age, weight, TBSA, deep-partial-thickness burn, gender, inhalation injury, shock, excision area, and MEEK ratio. By contrast, statistically significant differences in per unit area of operation time, per unit area of operation spending, hospitalization cost, hospitalization duration, wound-healing time, skin graft survival, and scar quality were found between hydrosurgical excision group with MEEK microskin graft and conventional excision group with MEEK microskin graft. ConclusionThe hydrosurgical excision system showed better clinical effects for patients with massive burns.

A humanized IL-2 mutein expands Tregs and prolongs transplant survival in preclinical models.

Long-term organ transplant survival remains suboptimal, and life-long immunosuppression predisposes transplant recipients to an increased risk of infection, malignancy, and kidney toxicity. Promoting the regulatory arm of the immune system by expanding Tregs may allow immunosuppression minimization and improve long-term graft outcomes. While low-dose IL-2 treatment can expand Tregs, it has a short half-life and off-target expansion of NK and effector T cells, limiting its clinical applicability. Here, we designed a humanized mutein IL-2 with high Treg selectivity and a prolonged half-life due to the fusion of an Fc domain, which we termed mIL-2. We showed selective and sustainable Treg expansion by mIL-2 in 2 murine models of skin transplantation. This expansion led to donor-specific tolerance through robust increases in polyclonal and antigen-specific Tregs, along with enhanced Treg-suppressive function. We also showed that Treg expansion by mIL-2 could overcome the failure of calcineurin inhibitors or costimulation blockade to prolong the survival of major-mismatched skin grafts. Validating its translational potential, mIL-2 induced a selective and sustainable in vivo Treg expansion in cynomolgus monkeys and showed selectivity for human Tregs in vitro and in a humanized mouse model. This work demonstrated that mIL-2 can enhance immune regulation and promote long-term allograft survival, potentially minimizing immunosuppression.

A Model to Study Wound Healing Over Exposed Avascular Structures in Rodents With a 3D-Printed Wound Frame.

Soft tissue defects with exposed avascular structures require reconstruction with well-vascularized tissues. Extensive research is ongoing to explore tissue engineered products that provide durable coverage. However, there is a lack of controlled and affordable testbeds in the preclinical setting to reflect this challenging clinical scenario. We aimed to address this gap in the literature and develop a feasible and easily reproducible model in rodents that reflects an avascular structure in the wound bed. We created 20 × 20 mm full thickness wounds on the dorsal skin of Lewis rats and secured 0.5-mm-thick silicone sheets of varying sizes to the wound bed. A 3D-printed wound frame was designed to isolate the wound environment. Skin graft and free flap survival along with exposure of the underlying silicone was assessed. Rats were followed for 4 weeks with weekly dressing changes and photography. Samples were retrieved at the endpoint for tissue viability and histologic analysis. The total wound surface area was constant throughout the duration of the experiment in all groups and the wound frames were well tolerated. The portion of the skin graft without underlying silicone demonstrated integration with the underlying fascia and a histologically intact epidermis. Gradual necrosis of the portion of the skin graft overlying the silicone sheet was observed with varying sizes of the silicone sheet. When the size of the silicone sheet was reduced from 50% of the wound surface area, the portion surviving over the silicone sheet increased at the 4-week timepoint. The free flap provided complete coverage over the silicone sheet. We developed a novel model of rodent wound healing to maintain the same wound size and isolate the wound environment for up to 4 weeks. This model is clinically relevant to a complex wound with an avascular structure in the wound bed. Skin grafts failed to completely cover increasing sizes of the avascular structure, whereas the free flap was able to provide viable coverage. This cost-effective model will establish an easily reproducible platform to evaluate more complex bioengineered wound coverage solutions.

Application of a meshed artificial dermal scaffold and negative-pressure wound therapy in the treatment of full-thickness skin defects: a prospective in vivo study.

Artificial dermal scaffolds (ADSs) have great value in repairing deep skin defects. However, problems such as unsatisfactory angiogenesis and local dropsy or empyema often occur, resulting in delayed or even failed wound healing. Negative pressure wound therapy (NPWT) is an effective therapy to promote wound healing or shorten wound bed preparation time. Studies on whether it can improve the effects of ADSs have never been interrupted, and no consensus has been reached. In this study, an improved ADS was prepared by mesh technology, physicochemical experiments were conducted, cell adhesion and proliferation were assessed with the meshed ADS, and in vivo experiments were conducted to investigate the effects of meshed ADS or ADS combined with NPWT in repairing full-thickness skin defects. The results showed that the meshed ADS showed through-layer channels arranged in parallel longitudinal and transverse intersections. The cell experiments confirmed the good cytocompatibility. The in vivo experiments showed that there were no differences in the take rate or contraction of grafted skin among all experiment groups. The meshed ADS exhibited good histocompatibility, and there were no differences in tissue inflammation, dermal angiogenesis, or degradation among all groups. In addition, necrosis, dropsy, or empyema of the dermal scaffold were found in all experiment groups except for the meshed ADS + NPWT group, which showed better wound repair results, including fewer scaffold-related complications and satisfactory skin graft survival and wound contraction. In conclusion, this novel meshed ADS, which has a regular through-layer mesh structure and possesses stable physicochemical properties and good biocompatibility, combined with NPWT can ensure adequate subdermal drainage and reduce the risk of scaffold-related complications, thereby improving the quality and efficiency of wound repair, promoting a broader application of biomaterials, and helping physicians and readers implement more effective wound management.

A case series describing combined negative pressure wound therapy and split-thickness skin graft as a method of sterilizing and closing midline laparotomy wounds near ostomies.

Negative pressure wound therapy (NPWT) promotes wound sterilization, improves tissue granulation, and ensures appropriate wound healing. Its potential in contaminated abdominal procedures is still under study, but the results are promising. This research provides insight into the use of NPWT for the effective preparation of laparotomy wounds in close proximity to ostomies. It also demonstrates the application of NPWT systems for successful skin graft take under these conditions. The authors describe 3 cases in the burn unit of an academic hospital in the northeastern United States treated successfully with a combination of NPWT and skin grafting to manage open abdominal laparotomy wounds in close proximity to ostomies. NPWT improved skin graft survival by promoting the creation of a clean base, which is important for ensuring appropriate skin graft take, and strengthening the bond between the graft and the recipient wound bed. Despite these successful results, evidence in this area is still mixed and would benefit from further studies in the field.

Granulation-embedded autologous skin grafting improves healing chronic wounds at high altitudes: a pilot study.

The management of chronic wounds presents a challenge for surgeons. In this pilot study, the authors established a novel auto-grafting approach for chronic wounds and evaluated its efficacy. The objective of this pilot study was to observe the clinical efficacy of granulation-embedded skin grafting for the treatment of chronic wounds at high altitudes. The data of 45 patients with chronic wounds were obtained from the medical records of the Yushu People's Hospital. Patients were divided into stamp skin-grafting and granulation-embedded skin-grafting groups. Skin graft survival rate, wound coverage rate, and wound-healing time were observed and recorded. The length of hospital stay and 1% total body surface area (TBSA) treatment cost were compared. Significant differences were noted in skin graft survival rate (94% ± 3% vs 86% ± 3%, P < .01), wound coverage rate on postoperative day 7 (61% ± 16% vs 54% ± 18%, P < .01), and wound-healing times (23 ± 2.52 days vs 31 ± 3.61 days, P < .05). The length of hospital stay and 1% TBSA treatment cost were significantly reduced in the granulation-embedded skin grafting group (P < .05). Granulation-embedded skin grafting can improve the healing of chronic wounds at high altitudes. These findings provide a new approach to the clinical treatment of chronic wounds.

Galectin-9 contributes to the survival of fully allogeneic skin grafts by modulating effector T cells and Tregs imbalance.

Allogeneic skin transplantation is an important clinical treatment for many diseases. Although Galectin-9 demonstrates multifaceted roles in modulating immune cell homeostasis and inflammation, its precise impact on balancing effector T cells and Tregs during allogeneic skin transplantation remains uncertain. This work was performed to evaluate the modulation of the survival time of allogeneic skin grafts by Gal-9 and to explore the critical mechanism involved in this process. Skin graft transplantation was conducted using C57BL/6 and BALB/c mice. Additionally, the levels of IL-2, IFN-γ, IL-4, and IL-17A were measured. Hematoxylin and eosin staining assay was performed to analyze the pathological conditions of skin grafts of experiment mice. The results revealed that Gal-9 noticeably prolonged the survival of the allogeneic skin graft and ameliorated the damage caused by acute immune rejection. Furthermore, Gal-9 resulted in selective reduction of effectors T cells such as Th1, and Th17. Simultaneously, Gal-9 didn't attenuate the protective function for allograft, which alleviated the immune rejection caused by abnormal immune imbalance. Gal-9 exhibited a therapeutic effect on the allogeneic skin graft by selectively reducing CD4+TIM-3+ T effector cells and inducing a shift from a Th1 to an anti-inflammatory Th2 response. Furthermore, Gal-9 did not attenuate the protective function. Our present study may represent a novel therapeutic candidate for modulating effector T cells and Tregs imbalance-based therapy of allograft transplantation.

Blockade of Common Gamma Chain Cytokine Signaling with REGN7257, an Interleukin 2 Receptor Gamma (IL2RG) Monoclonal Antibody, in Combination with Costimulatory Blockers Delayed Skin Graft Rejection in Mice

There is a current medical need to identify innovative maintenance therapies to prevent allograft rejection in solid organ transplantation. During transplant rejection, recipient immune cells identify a grafted organ as foreign and attack it: CD4 + T cells orchestrate transplant rejection by recruiting a range of effector cells responsible for the damage of rejection including CD8 + T cells, NK cells, B cells and macrophages. These pathogenic immune cell responses can be driven by cytokines of the common gamma chain (γ c) cytokine family (IL2, IL4, IL7, IL9, IL15, and IL21). γ c cytokines signal through their corresponding receptors, expressed primarily on immune cells, that share a common coreceptor, interleukin 2 receptor subunit gamma (IL2RG) that is required for signaling. To understand the role of γ c cytokines in driving transplant rejection, we generated REGN7257, a fully human IL2RG monoclonal antibody that inhibits γ c cytokine-induced signaling, and we tested its ability to suppress allogeneic immune cell responses in a mouse model of skin graft rejection when delivered as a monotherapy and in combination with mycophenolate mofetil (MMF) or T cell costimulatory pathway blockers. In this model, recipient B6/129 (mixed background) Il2rg hu/hu mice were transplanted with tail skin from BALB/cJ donor mice. Graft survival was analyzed using a log rank Mantel-Cox test to detect statistically significant differences across groups (*=p&amp;lt;0.033; **= p&amp;lt;0.002; ***=p&amp;lt;0.0002; ****=p&amp;lt;0.0001). In a mouse model of skin graft rejection, γ c cytokine signaling blockade with REGN7257 given as maintenance immunosuppression effectively improved overall graft survival (Median Survival Time [MST] IL2RG=13) compared to mice that received a control antibody (MST CTRL=9 [****vs IL2RG Ab]), and with similar efficacy to that observed with the calcineurin inhibitor tacrolimus (MST TAC=12.5 [**vs control, n.s. vs IL2RG Ab]). In treatment combination experiments, while monotherapy treatment with the antiproliferative agent MMF was not as efficient as REGN7257 at delaying skin graft rejection (MST MMF=10 [*vs control] and MST IL2RG=12 [*vs MMF]), simultaneous blockade of cell proliferation and γ c cytokine signaling conferred an advantage over monotherapies (MST MMF+IL2RG=15.5 [****vs control, **vs IL2RG Ab]). Similarly, induction therapy consisting of γ c cytokine signaling blockade followed by maintenance immunosuppression using the CTLA4-Ig fusion protein abatacept, significantly improved overall skin graft survival (MST IL2RG+CTLA4=19.5 [****vs control]) compared to REGN7257 induction only (MST IL2RG=11 [****vs control and combo]) or abatacept maintenance only (MST CTLA4=10 [*vs control, ****vs combo]). Finally, maintenance immunosuppression combining blocking of γc cytokine signaling together with blocking of both CD28 and CD40L costimulatory signals prolonged skin graft survival better than any combination therapies of only 2 pathway blockers (MST TRIPLE=26 [**vs control] and MST DOUBLE=16-21 [n.s.-** vs triple]). Overall, our study showed that γ c cytokine blockade could potentially be an alternative to calcineurin inhibitor-based regimens to prevent rejection by specifically targeting immune cells. Our data also highlighted the inherent complexity of effector mechanisms and pathways involved in allograft rejection and showed that prolonged allograft survival requires simultaneous blockade of multiple T cell activating signals, including inhibition of cytokine signaling and costimulatory signals. These data provide evidence of γ c cytokines as key drivers of allogeneic immune cell responses during acute transplant rejection, offering a potentially novel strategy for the management of transplant patients.

The effects of topical mafenide acetate application on skin graft survival in bacterial contaminated wounds

BackgroundInfection related skin graft loss still remains as a common problem even with the use of systemic antibiotics. Mafenide acetate (Sulfamylon) is a topical antimicrobial agent with a wide spectrum of antimicrobial activity. Since mafenide acetate has the ability to penetrate the burn eschar, it was preferred in the treatment of infected full-thickness skin grafts. We investigated the effects of topical Mafenide acetate application on graft survival in an experimental model of contaminated wound beds in rats. Materials and methodsTwenty-eight male Wistar albino rats were included in the study. A full-thickness skin graft (FTSG) was harvested from the back region and the wound bed was inoculated with Pseudomonas aeruginosa. The same FTSG was sutured in place. Rats were divided into 4 groups. In groups 1 and 2, wound care was performed with gauze and hydrofiber dressings respectively. In groups 3 and 4, Mafenide acetate soaked hydrofiber and Mafenide acetate soaked gauze dressings were used respectively. The dressings were closed for 4 days in all groups. The rats in groups 1 and 2 received dressing changes every day. The dressing of the rats in group 3 was changed once every two days. The dressing of the rats in group 4 was changed twice a day. ResultsIn groups 3 and 4, the graft survival rates decreased significantly from day 7 to day 14 in all groups. Histologically, detachment at the dermoepidermal junction, disorganization of collagen along with increased numbers of fibroblasts and a decrease in graft adhesion to the wound bed were determined in Mafenide acetate-treated groups. ConclusionIn rats treated with Mafenide acetate, graft survival was higher on day 7 and gradually decreased towards day 14. Application of a 2.5% solution of Mafenide acetate longer than 7 days on inoculated skin grafts in a rat model causes significant cytotoxicity and graft loss.

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.

Exosomes derived from LPS-preconditioned bone marrow-derived MSC modulate macrophage plasticity to promote allograft survival via the NF-κB/NLRP3 signaling pathway

ObjectivesThis study investigated whether exosomes from LPS pretreated bone marrow mesenchymal stem cells (LPS pre-MSCs) could prolong skin graft survival.MethodsThe exosomes were isolated from the supernatant of MSCs pretreated with LPS. LPS pre-Exo and rapamycin were injected via the tail vein into C57BL/6 mice allografted with BALB/c skin; graft survival was observed and evaluated. The accumulation and polarization of macrophages were examined by immunohistochemistry. The differentiation of macrophages in the spleen was analyzed by flow cytometry. For in vitro, an inflammatory model was established. Specifically, bone marrow-derived macrophages (BMDMs) were isolated and cultured with LPS (100 ng/ml) for 3 h, and were further treated with LPS pre-Exo for 24 h or 48 h. The molecular signaling pathway responsible for modulating inflammation was examined by Western blotting. The expressions of downstream inflammatory cytokines were determined by Elisa, and the polarization of macrophages was analyzed by flow cytometry.ResultsLPS pre-Exo could better ablate inflammation compared to untreated MSC-derived exosomes (BM-Exo). These loaded factors inhibited the expressions of inflammatory factors via a negative feedback mechanism. In vivo, LPS pre-Exo significantly attenuated inflammatory infiltration, thus improving the survival of allogeneic skin graft. Flow cytometric analysis of BMDMs showed that LPS pre-Exo were involved in the regulation of macrophage polarization and immune homeostasis during inflammation. Further investigation revealed that the NF-κB/NLRP3/procaspase-1/IL-1β signaling pathway played a key role in LPS pre-Exo-mediated regulation of macrophage polarization. Inhibiting NF-κB in BMDMs could abolish the LPS-induced activation of inflammatory pathways and the polarization of M1 macrophages while increasing the proportion of M2 cells.ConclusionLPS pre-Exo are able to switch the polarization of macrophages and enhance the resolution of inflammation. This type of exosomes provides an improved immunotherapeutic potential in prolonging graft survival.

Two-Pronged Microbe Delivery of Nitric Oxide and Oxygen for Diabetic Wound Healing.

Chronic inflammation and hypoxia in the microenvironment of diabetic foot ulcers (DFUs) can result in sustained vascular impairment, hindering tissue regeneration. While both nitric oxide and oxygen have been shown to promote wound healing in DFUs through anti-inflammatory and neovascularization, there is currently no available therapy that delivers both. We present a novel hydrogel consisting of Weissella and Chlorella, which alternates between nitric oxide and oxygen production to reduce chronic inflammation and hypoxia. Further experiments indicate that the hydrogel accelerates wound closure, re-epithelialization, and angiogenesis in diabetic mice and improves the survival of skin grafts. This dual-gas therapy holds promise as a potential treatment option for the management of diabetic wounds.