Skin Flap Survival Research Articles

Biliverdin improved angiogenesis and suppressed apoptosis via PI3K/Akt-mediated Nrf2 antioxidant system to promote ischemic flap survival

Plastic and reconstructive surgeons frequently utilize random skin flap transplantation to repair skin defects. However, the procedure carries a substantial risk of necrosis. Previous research has suggested that Biliverdin (Bv), the main component of Calculus Bovis, possessed potent anti-ischemic properties, making it a potential therapeutic agent for skin flap survival. Hence, in this study, the potential of Bv in promoting flap survival has been comprehensively investigated. Network pharmacology analysis revealed that the pharmacological effects of Bv on ischemic diseases may be attributed to its modulation of various signaling molecules, including the PI3K-Akt pathway. In vitro results demonstrated that Bv treatment significantly promoted angiogenesis in human umbilical vein endothelial cells (HUVEC), even in the presence of H2O2. This was evident by the increased cell proliferation, enhanced migration, and improved tube formation. Bv also effectively attenuated the intracellular generation of reactive oxygen species (ROS) induced by H2O2, which was achieved by suppressing mitochondrial ROS production through the PI3K/Akt-mediated activation of Nrf2/HO-1 signaling pathway. Consequently, Bv treatment led to a significant reduction in apoptosis and an increase in cell viability of HUVEC. Furthermore, in vivo experiment demonstrated that Bv treatment vastly elevated flap survival through enhancing angiogenesis while decreasing oxidative stress and apoptosis, which was comparable to the results of positive control of N-acetylcysteine (Nac). In conclusion, this study not only established a solid foundation for future study on therapeutic potential of Bv, but also proposed a promising treatment approach for enhancing the success rate of flap transplants and other ischemic-related tissue repair.

Quercetin activates autophagy in the distal ischemic area of random skin flaps through Beclin1 to enhance the adaptability to energy deficiency

Random flaps are frequently employed in treating substantial skin abnormalities and in surgical tissue-rebuilding interventions. The random flap technique provides flaps of specific dimensions and contours to fit the surgical incision. However, blood supply deficiency and subsequent ischemia-reperfusion injury can cause severe oxidative stress and apoptosis, eventually leading to distal necrosis, which limits the clinical application of the flap. Quercetin (QUE) is primarily found in the glycoside form in many plant parts, such as stem bark, flowers, leaves, buds, seeds, and fruits. Cellular, animal, and clinical studies have demonstrated the antioxidant, anti-apoptosis, anti-inflammatory, and activation of autophagy properties of QUE. In previous studies, high doses of QUE effectively suppressed the survival of human umbilical vein endothelial cells (HUVECs) stimulated by hydrogen peroxide. However, different concentration gradients of QUE on HUVECs revealed a significant protective effect at a concentration of 10 mM. The protective impact of QUE on HUVECs was evaluated using scratch tests, CCK-8 assays, and EDU assays. Simultaneously, a mouse model of random skin flap was created, and the impact of QUE on skin flap survival was examined by intragastric injection. The QUE group showed a significantly larger survival area of the random flap and higher blood flow intensity compared to the control group. Furthermore, the beneficial effects of QUE were reversed by the autophagy inhibitor 3-MA. Therefore, autophagy plays a significant role in the therapeutic benefits of QUE on flap survival.

Clinical study on anterolateral femoral interregional flap with turbocharge technique in the repair of large limb wounds.

To compare the clinical outcomes of anterolateral femoral interregional flap with turbocharge technique and traditional anterolateral femoral flap in repair of large limb wounds. Clinical data of 38 patients with large limb surface wound (11 cm×39 cm-16 cm×65 cm) admitted to the Sir Run Run Shaw Hospital, Zhejiang University School of Medicine from May 2018 to May 2022 were retrospectively analyzed. Eighteen patients were treated by anterolateral thigh perforator flap combined with superficial circumflex iliac artery flap (ALTP-SCIAP) with turbocharge technique (interregional flap group); while 20 patients were treated with unilateral or bilateral anterolateral femoral flaps, combined with skin grafting if necessary (traditional anterolateral femoral flap group). The survival of skin flap, repair of donor area, complications and patient satisfaction were compared between the two groups. In interregional flap group, 18 flaps were harvested and transplanted, the flap width, length and the viable area were (9.9±2.0) cm, (44.2±3.5) cm and (343.2±79.9) cm2, respectively. In traditional anterolateral femoral flap group, 29 flaps were harvested and transplanted, the flap width, length and the viable area were (11.0±2.8) cm, (21.7±3.2) cm and (186.4±49.2) cm2, respectively. There were significant differences in the flap length and the viable area between the two groups (t=22.365 and 8.345, both P<0.05). In the interregional flap group, the donor site of flap was closed by direct suture in 11 flaps, by skin retractor assisted suture in 6 flaps, and by skin grafting in one flap. In traditional anterolateral femoral flap group, the donor site of flap was closed by direct suture in 12 flaps, by skin retractor assisted suture in 11 flaps, and by skin grafting in 6 flaps. The skin graft rates of the two groups were 5.6% (1/18) and 20.7% (6/29), respectively (χ2=2.007, P>0.05). The interregional flap group had lower postoperative complications rate (5.6% vs. 35.0%, χ2=4.942, P<0.05) and higher patient satisfaction rate (94.4% vs. 70.0%, χ2=4.448, P<0.05) than traditional anterolateral femoral flap group. Compared with the traditional anterolateral femoral flap, the anterolateral femoral interregional flap with turbocharge technique has a larger flap area, most of the donor areas of the flap can be sutured directly without skin grafting and with less complications and a higher patient satisfaction rate.

Enhancing Skin Flap Survival with Preoperative Carbon Dioxide Fractional Laser Treatment: A Novel Approach in Reconstructive Surgery

Background: Skin flap necrosis remains a significant challenge in reconstructive surgery, predominantly due to insufficient blood supply. Traditional methods like the surgical delay procedure, while effective, are invasive and associated with considerable patient discomfort and health care costs. This study explores the efficacy of Carbon Dioxide Fractional Laser (CDFL) treatment as a novel, less invasive alternative to enhance skin flap survival. Methods: Twenty-nine adult male Sprague-Dawley rats were divided into 2 groups: a CDFL treatment group (n=14) and a control group (n=15). The CDFL group received laser pretreatment 1 week before flap surgery, whereas the control group underwent flap surgery without pretreatment. Flap survival was assessed 7 days postsurgery using indocyanine green fluorescence angiography. In addition, histological analysis was conducted to evaluate tissue integrity, capillary density, and VEGF expression. Results: The CDFL-treated flaps showed significantly increased survival areas compared with controls (P&lt;0.01). Histological evaluation revealed enhanced capillary dilation and increased VEGF expression in the CDFL group (P&lt;0.05). Although capillary density was higher in the CDFL group, it did not reach statistical significance (P=0.052). Conclusion: CDFL pretreatment significantly improves skin flap survival in rats, suggesting potential as a minimally invasive alternative to traditional surgical delay techniques. This approach could offer substantial benefits in reconstructive surgery, reducing patient morbidity and associated costs. Further studies are warranted to confirm these findings in clinical settings.

Erastin promotes random-pattern skin flaps survival by inducing mTORC1-TFEB mediated autophagy

Random-pattern skin flaps are important method for skin reconstruction after defect; however, the distal end of flaps is not easily viable due to inadequate nutrient supply. Erastin is a well-established ferroptosis inducer, but our study found that low-dose of erastin (2 μM) may reduce nutrient deficiency induced cell death in human umbilical vein endothelial cells (HUVECs). RNA-seq analysis suggested that its role was related to autophagy regulation. Follow-up studies have shown that the use of autophagy inhibitors or the knockdown of TFEB in HUVECs can both reduce the anti-apoptotic effect of erastin in HUVECs. Mechanism study demonstrated that erastin can suppress mTORC1 and promote TFEB activity in HUVECs, suggesting that the effect of erastin on the survival of HUVECs under nutrient deprivation conditions is regulated by mTORC1/TFEB. Subsequently, we evaluated the effect of erastin on the survival of random-pattern skin flaps in mice in vivo. On the postoperative day 7, we observed a significant increase in flap survival area, blood perfusion, and microvascular density after erastin treatment; also, erastin treatment showed enhanced autophagy within the ischemic region. In summary, our study demonstrates that low-dose of erastin may suppress cell death in endothelial cells under nutrient deficiency condition, and its effects may relate to the mTORC1-TFEB medicated autophagy regulation, erastin treatment may be a potential therapy for random-pattern skin flaps.

Evaluating the pro-survival potential of apoptotic bodies derived from 2D- and 3D- cultured adipose stem cells in ischaemic flaps

In the realm of large-area trauma flap transplantation, averting ischaemic necrosis emerges as a pivotal concern. Several key mechanisms, including the promotion of angiogenesis, the inhibition of oxidative stress, the suppression of cell death, and the mitigation of inflammation, are crucial for enhancing skin flap survival. Apoptotic bodies (ABs), arising from cell apoptosis, have recently emerged as significant contributors to these functions. This study engineered three-dimensional (3D)-ABs using tissue-like mouse adipose-derived stem cells (mADSCs) cultured in a 3D environment to compare their superior biological effects against 2D-ABs in bolstering skin flap survival. The findings reveal that 3D-ABs (85.74 ± 4.51) % outperform 2D-ABs (76.48 ± 5.04) % in enhancing the survival rate of ischaemic skin flaps (60.45 ± 8.95) % (all p < 0.05). Mechanistically, they stimulated angiogenesis, mitigated oxidative stress, suppressed apoptosis, and facilitated the transition of macrophages from M1 to M2 polarization (all p < 0.05). A comparative analysis of microRNA (miRNA) profiles in 3D- and 2D-ABs identified several specific miRNAs (miR-423-5p-up, miR30b-5p-down, etc.) with pertinent roles. In summary, ABs derived from mADSCs cultured in a 3D spheroid-like arrangement exhibit heightened biological activity compared to those from 2D-cultured mADSCs and are more effective in promoting ischaemic skin flap survival. These effects are attributed to their influence on specific miRNAs.

Spermidine Exerts Protective Effects in Random-Pattern Skin Flap Survival in Rats: Possible Involvement of Inflammatory Cytokines, Nitric Oxide, and VEGF.

Distal necrosis and inflammation are two of the most common health consequences of random-pattern skin flaps survival (SFS). Anti-inflammatory effects of spermidine have been identified in various studies. On the other hand, considering the involvement of the nitric oxide molecule in the spermidine mode of action and also its role in skin tissue function, we analyzed the possible effects of spermidine on the SFS and also, potential involvement of nitrergic pathway and inflammatory cytokine in these phenomena. Each rat was pretreated with either a vehicle (control) or various doses of spermidine (0.5, 1, 3, 5, 10 and 30 mg/kg) and then was executed a random-pattern skin flap paradigm. Also, spermidine at the dose of 5 mg/kg was selected and one group rats received spermidine 20 min prior to surgery and one additional dose 1 day after operation. Then, 7 days after operations, interleukin (IL)-6, tumor necrosis factor (TNF)-α, interferon-gamma (IFN-γ), and nitrite levels were inquired in the tissue samples by ELIZA kit. Vascular endothelial growth factor expression was assessed by DAPI staining and fluorescent microscopes. The concentrations of three polyamines, including spermidine, spermine, and cadaverine, were analyzed using HPLC. Pretreatment with spermidine 5 mg/kg improved SFS considerably in microscopic skin H&E staining analysis and decreased the percentage of necrotic area. Moreover, spermidine exerted promising anti-inflammatory effects via the modulation of nitric oxide and reducing inflammatory cytokines. Spermidine could improve skin flaps survival, probably through the nitrergic system and inflammation pathways. This preclinical study provides level III evidence for the potential therapeutic effects of spermidine on SFS in rats, based on the analysis of animal models. Further studies are needed to confirm these findings in clinical settings. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

β-Caryophyllene promotes the survival of random skin flaps by upregulating the PI3K/AKT signaling pathway

BackgroundFlap transplantation is a widely used plastic repair technique in surgical procedures, aimed at addressing skin defects resulting from diverse wounds and diseases. However, due to the insufficient blood supply after flap surgery, the occurrence of ischemia-reperfusion injury, and an excessive sterile inflammatory response, flaps frequently develop complications (e.g., partial or complete ischemic necrosis). These complications have adverse effects on wound healing and repair. β-Caryophyllene (BCP) is a bicyclic sesquiterpene that is widely present in plants. It mitigates oxidative stress and inflammatory responses, demonstrates neuroprotective and analgesic properties, and serves a protective function in organs or tissues subjected to ischemia-reperfusion injury. However, no study has confirmed whether BCP can be used in the field of flap transplantation to improve the flap survival rate. MethodsTo assess the impact of BCP on random flap survival, we constructed a modified McFarlane random flap model on the rat. After 7 consecutive days of gavage with different doses of BCP, we measured the survival area ratio, angiogenesis, blood perfusion, tissue inflammation level, apoptosis-related protein levels, and the PI3K/AKT signaling pathway expression of the random flap. ResultsBCP treatment increased the survival area of the flap in a dose-dependent manner after random flap transplantation in rats. BCP mainly promoted the formation of tissue blood vessels, improved flap blood perfusion, limited the local inflammatory response, and reduced apoptosis. In addition, we demonstrated that BCP works primarily by promoting the PI3K/AKT signaling expression while enhancing the phosphorylation of AKT. Administration of wortmannin, a selective inhibitor of PI3K, eliminated the effects of BCP. ConclusionBCP can promote the survival of random flaps by upregulating the PI3K/AKT signaling pathway, increasing tissue blood perfusion, and limiting the inflammatory response and apoptosis.

Protective effects of the bioactive peptide from maggots against skin flap ischemia‒reperfusion injury in rats

Ischemia‒reperfusion (I/R) injury is a frequently observed complication after flap surgery, and it affects skin flap survival and patient prognosis. Currently, there are no proven safe and effective treatment options to treat skin flap I/R injury. Herein, the potential efficacies of the bioactive peptide from maggots (BPM), as well as its underlying mechanisms, were explored in a rat model of skin flap I/R injury and LPS- or H2O2-elicited RAW 264.7 cells. We demonstrated that BPM significantly ameliorated the area of flap survival, and histological changes in skin tissue in vivo. Furthermore, BPM could markedly restore or enhance Nrf2 and HO-1 levels, and suppress the expression of pro-inflammatory cytokines, including TLR4, p-IκB, NFκB p65, p-p65, IL-6, and TNF-α in I/R-injured skin flaps. In addition, BPM treatment exhibited excellent biocompatibility with an adequate safety profile, while it exhibited superior ROS-scavenging ability and the upregulation of antioxidant enzymes in vitro. Mechanistically, the above benefits related to BPM involved the activation of Nrf2/HO-1 and suppression of TLR4/NF-κB pathway. Taken together, this study may provide a scientific basis for the potential therapeutic effect of BPM in the prevention of skin flap I/R injury and other related diseases.

The effect of dapsone on skin flap survival depends on modulation of inflammatory response and VEGF expression

The random-pattern skin flap is a common method used for reconstructing skin defects. However, flap ischemia necrosis remains a significant challenge in plastic surgery. Strategies aimed at reducing persistent inflammation and promoting blood supply through angiogenesis have been identified as crucial for improving flap survival. Dapsone, a chemotherapeutic agent known for its anti-inflammatory properties through multiple pathways, is of interest in this regard. This study aims to investigate the effect of dapsone on random-pattern flap survival in rats, along with its impact on inflammation and angiogenesis. The ischemia/reperfusion (I/R) injury rat models were created using a caudal-based dorsal skin flap with delayed I/R. Twenty-four male Sprague Dawley rats were divided into control, sham, and two treatment groups receiving dapsone at doses of 12.5 mg/kg/day and 5 mg/kg/day, respectively. On the 7th post-operative day, flap survival was evaluated. Neutrophil infiltration and ulceration were measured through microscopic examination, and interleukin (IL)-8 levels through enzyme-linked immunosorbent assay. Expression levels of vascular endothelial growth factor (VEGF) and tumor necrosis factor-alpha (TNF-&amp;alpha;) were determined using an immunohistochemistry (IHC) array. The findings revealed an increased flap survival on day 7 post-operation following systemic administration of dapsone for 5 consecutive days. Dapsone at both dosages significantly reduced the ulcer thickness, neutrophil infiltration, and IL-8 levels. The IHC results revealed that VEGF expression was significantly higher in the treatment groups compared to the control group. Moreover, TNF-&amp;alpha; expression was significantly lower in the treatment groups compared to the control group. In conclusion, we confirmed that treatment with dapsone promotes skin flap survival, and this effect aligned with a reduction in persistent inflammation and the enhancement of VEGF. Nonetheless, more studies are required to elucidate the precise anti-inflammatory mechanism of dapsone in I/R injuries.

Reactive Oxygen Species Scavenging Injectable Hydrogel Potentiates the Therapeutic Potential of Mesenchymal Stem Cells in Skin Flap Regeneration.

Cell-based therapies offer tremendous potential for skin flap regeneration. However, the hostile microenvironment of the injured tissue adversely affects the longevity and paracrine effects of the implanted cells, severely reducing their therapeutic effectiveness. Here, an injectable hydrogel (nGk) with reactive oxygen species (ROS) scavenging capability, which can amplify the cell viability and functions of encapsulated mesenchymal stem cells (MSCs), is employed to promote skin flap repair. nGk is formulated by dispersing manganese dioxide nanoparticles (MnO2 NPs) in a gelatin/κ-carrageenan hydrogel, which exhibits satisfactory injectable properties and undergoes a sol-gel phase transition at around 40 °C, leading to the formation of a solid gel at physiological temperature. MnO2 NPs enhance the mechanical properties of the hydrogel and give it the ability to scavenge ROS, thus providing a cell-protective system for MSCs. Cell culture studies show that nGk can mitigate the oxidative stress, improve cell viability, and boost stem cell paracrine function to promote angiogenesis. Furthermore, MSC-loaded nGk (nGk@MSCs) can improve the survival of skin flaps by promoting angiogenesis, reducing inflammatory reactions, and attenuating necrosis, providing an effective approach for tissue regeneration. Collectively, injectable nGk has substantial potential to enhance the therapeutic benefits of MSCs, making it a valuable delivery system for cell-based therapies.

Effects of systemically administered tramadol hydrochloride on random pattern skin flap survival in rats

Aim: Tramadol is a weak centrally acting opioid analgesic with µ-opioid receptor agonist effects. It has been explored for its analgesic efficacy through various in-vitro and in-vivo studies. The skin, as the body’s largest organ and the protector barrier, is vulnerable to injuries and wounds that can cause significant challenges due to pain, economic burdens and psychological implications. Successful healing of wound involves complex processes and it is influenced by factors such as angiogenesis and nitric oxide levels. This study investigates the effects of tramadol on wound healing in experimental ischemic wound models in rats. Material and Methods: Two 6 mm ischemic wound models were created on the backs of 30 male Wistar Albino rats, with wound areas cut along the long edges and a sterile silicone material placed between the panniculus carnosus fascia and paraspinosus muscle. Rats were randomized into Tramadol, Control, and Sham groups. The wounds were imaged using a "SONY ILCE-7" camera on days 0, 3, 6, 10, and 14. Wound areas and healing percentages were calculated from the images and recorded for statistical purposes. After 14 days, the animals were sacrificed under general anesthesia for histopathological examination of tissue samples. CD31 and VEGF antibodies were used to evaluate the density and morphology of vascular structures. Results: Tramadol administration accelerated the healing of wound surface area. Significant differences were found between groups in terms of inflammation, and data recorded in CD34, CD31, and VEGF-stained preparations. Conclusion: The study found that tramadol positively contributes to wound healing in the acute phase of ischemic wounds by affecting various processes.

Progress in the study of mechanisms and pathways related to the survival of random skin flaps.

The clinical application of random flaps in wound repair has been a topic of discussion. Random flaps are prone to necrosis due to the lack of well-defined vascular blood supply during transfer surgery. Their clinical utility is restricted, financial and psychological burdens is imposed on patients due to this limitation. The survival of random skin flaps depends on factors such as ischemia-reperfusion injury, oxidative stress, local inflammatory response, and neovascularization. This review aims to provide an overview of the evidence supporting the use of random flaps in clinical practice. In addition, this review explores the impact of different medications on signaling pathways within the flap's local microcirculation and investigates the interconnections between these pathways.

Tetrahydropalmatine promotes random skin flap survival in rats via the PI3K/AKT signaling pathway

Ethnopharmacological relevanceFlap necrosis is the most common complication after flap transplantation, but its prevention remains challenging. Tetrahydropalmatine (THP) is the main bioactive component of the traditional Chinese medicine Corydalis yanhusuo, with effects that include the activation of blood circulation, the promotion of qi, and pain relief. Although THP is widely used to treat various pain conditions, its impact on flap survival is unknown. Aim of the studyTo explore the effect and mechanism of THP on skin flap survival. Materials and methodsIn this study, we established a modified McFarlane flap model, and the flap survival rate was calculated after 7 days of THP treatment. Angiogenesis and blood perfusion were evaluated using lead oxide/gelatin angiography and laser Doppler, respectively. Flap tissue obtained from zone II was evaluated histopathologically, by hematoxylin and eosin staining, and in assays for malondialdehyde content and superoxide dismutase activity. Immunofluorescence was performed to detect interleukin (IL)-6, tumor necrosis factor (TNF)-α, hypoxia-inducible factor (HIF)-1α, Bcl-2, Bax, caspase-3, caspase-9, SQSTM1/P62, Beclin-1, and LC3 expression, and Western blot to assess PI3K/AKT signaling pathway activation and Vascular endothelial growth factor (VEGF) expression. The role played by the autophagy pathway in flap necrosis was examined using rapamycin, a specific inhibitor of mTOR. ResultsExperimentally, THP improved the survival rate of skin flaps, promoted angiogenesis, and improved blood perfusion. THP administration reduced the inflammatory response, oxidative stress, and apoptosis in addition to inhibiting autophagy via the PI3K/AKT/mTOR pathway. Rapamycin partially reversed these effects. ConclusionTHP promotes skin flap survival via the PI3K/AKT signaling pathway.

Novel Noninvasive Hybrid Flap Preconditioning (HFP) Surpasses Surgical Delay in the Murine Model.

Ischemic necrosis in the distal portion of the flap is a challenging complication in plastic surgery. We hypothesize a novel hybrid flap preconditioning (HFP) device combining foam-mediated external suction and non-surgical delay can promote skin flap survival better than surgical delay. Twenty-eight mouse were divided into four groups. Control group: a 4*1.5 dorsal flap was made with no preconditioning. Surgical delay (SD) group: surgical delay was made 7 days before flap elevation. Foam-mediated external suction (FMES) group: foam-mediated external suction at -100mmHg was employed 5 hours per day for 6 days, and the flap was elevated on the seventh day. Hybrid Flap Preconditioning (HFP) group: silicone strips was applied along the contour of the foam interface. Same negative pressure protocol was used as the FMES group. Seven days after flap elevation, macroscopic, histologic, and Western blot analyses were performed. The flap survival rate was 46.25% (8.12%) in the control group, 68.72% (7.00%) in the SD group, 57.03% (8.17%) in the FMES group and 80.66% (3.27%) in the HFP group. Immunohistologic analysis of CD 31+ cell in distal end of viable tissue procured seven days after flap elevation showed a significantly higher angiogenesis in SD group and HFP group. Western Blot results showed an increased expression of VEGF in SD group and HFP group. We have developed and fabricated a novel hybrid flap precondition (HFP) device combining foam-mediated external suction and non-surgical delay. The concept of HFP is proved to promote flap survival better than surgical delay.

Chronic Cinacalcet improves skin flap survival in rats: the suggested role of the nitric oxide pathway.

Cinacalcet is a calcimimetic medicine that has been used to treat secondary hyperparathyroidism and parathyroid cancer. Various studies have proposed the positive role of calcium and its receptor in skin wound healing. Furthermore, Cinacalcet interacts with other skin repair-related mechanisms, including inflammation and nitric oxide pathways. The present study evaluated the effect of Cinacalcet on the random-pattern skin flap survival. Eighty-four Wistar male rats were used. Multiple doses of Cinacalcet (30, 3, 1, 0.3, and 0.05 mg/kg) were used in 3 different routes of administration before the surgery. Histopathological evaluations, quantitative assessment of IL-6, TNF-α, and nitric oxide (NO), and the expression of calcium-sensing receptor (CaSR) and E-cadherin were evaluated in the skin tissue. To assess the role of NO, a NO synthase inhibitor, N-nitro-L-arginine methyl ester hydrochloride (L-NAME), was used, and histopathological effects were investigated. Cinacalcet pretreatment at the IP chronic 1 mg/kg dose significantly increased the skin flap survival rate and enhanced the NO tissue level compared to the control. However, the administration of L-NAME abolished its protective effects. IP Chronic 1 mg/kg of Cinacalcet could also decline the levels of IL-6 and TNF-α and also increase the expression of CaSR and E-cadherin in the flap tissue compared with the control group. Chronic Cinacalcet at 1 mg/kg could improve skin flap survival, probably mediated by the CaSR, NO, and inflammation-related pathways.

Systemic allopurinol administration reduces malondialdehyde, interleukin 6, tumor necrosis factor α, and increases vascular endothelial growth factor in random flap Wistar rats exposed to nicotine.

Smoking poses a risk to flap viability, with nicotine being a major contributor to the formation of free radicals. Allopurinol, known for its antioxidant properties, has been shown to enhance tissue survival in ischemic conditions by reducing the production of reactive oxygen species (ROS). This study aims to assess the impact of allopurinol on the viability and success of skin flaps in Wistar rats exposed to nicotine. This study examined skin flap survival in nicotine-exposed rats treated with allopurinol. Twenty-eight rats were separated into two groups. During 1 month of nicotine exposure, the treatment group received systemic allopurinol 7 days before and 2 days after the flap procedure, while the control group received no allopurinol. Pro-angiogenic factors, proinflammatory factors, anti-inflammatory factors, and oxidative markers were assessed on the 7th day after the flap procedure using enzyme-linked immunosorbent assay method. Macroscopic flap viability was evaluated on the 7th day using Image J photos. As an oxidative marker, malondialdehyde levels were significantly lower in rats given allopurinol than in controls (P &lt; 0.001). The levels of interleukin 6 and tumor necrosis factor α, as markers of inflammatory factors, were significantly lower in the group of rats given allopurinol compared to controls (P &lt; 0.001). The level of angiogenesis in rats given allopurinol, measured by vascular endothelial growth factor levels, was also higher in the treatment group compared to controls (P &lt; 0.001). Macroscopically, the percentage of distal flap necrosis in Wistar rats given allopurinol was lower and statistically significant compared to controls (P &lt; 0.001). Xanthine oxidoreductase is part of a group of enzymes involved in reactions that produce ROS. Allopurinol, as an effective inhibitor of the xanthine oxidase enzyme, can reduce oxidative stress by decreasing the formation of ROS. This reduction in oxidative stress mitigates the risk of ischemic-reperfusion injury effects and significantly increases the viability of Wistar rat flaps exposed to nicotine.

Neuregulin-1, a member of the epidermal growth factor family, mitigates STING-mediated pyroptosis and necroptosis in ischaemic flaps

Abstract Background Ensuring the survival of the distal end of a random flap during hypoperfusion (ischaemia) is difficult in clinical practice. Effective prevention of programmed cell death is a potential strategy for inhibiting ischaemic flap necrosis. The activation of stimulator of interferon genes (STING) pathway promotes inflammation and leads to cell death. The epidermal growth factor family member neuregulin-1 (NRG1) reduces cell death by activating the protein kinase B (AKT) signalling pathway. Moreover, AKT signalling negatively regulates STING activity. We aimed to verify the efficacy of NRG1 injection in protecting against flap necrosis. Additionally, we investigated whether NRG1 effectively enhances ischemic flap survival by inhibiting pyroptosis and necroptosis through STING suppression. Methods A random-pattern skin flap model was generated on the backs of C57BL/6 mice. The skin flap survival area was determined. The blood supply and vascular network of the flap was assessed by laser Doppler blood flow analysis. Cluster of differentiation 34 immunohistochemistry (IHC) and haematoxylin and eosin (H&amp;E) staining of the flap sections revealed microvessels. Transcriptome sequencing analysis revealed the mechanism by which NRG1 promotes the survival of ischaemic flaps. The levels of angiogenesis, oxidative stress, necroptosis, pyroptosis and indicators associated with signalling pathways in flaps were examined by IHC, immunofluorescence and Western blotting. Packaging adeno-associated virus (AAV) was used to activate STING in flaps. Results NRG1 promoted the survival of ischaemic flaps. An increased subcutaneous vascular network and neovascularization were found in ischaemic flaps after the application of NRG1. Transcriptomic gene ontology enrichment analysis and protein level detection indicated that necroptosis, pyroptosis and STING activity were reduced in the NRG1 group. The phosphorylation of AKT and forkhead box O3a (FOXO3a) were increased after NRG1 treatment. The increased expression of STING in flaps induced by AAV reversed the therapeutic effect of NRG1. The ability of NRG1 to phosphorylate AKT-FOXO3a, inhibit STING and promote flap survival was abolished after the application of the AKT inhibitor MK2206. Conclusions NRG1 inhibits pyroptosis and necroptosis by activating the AKT-FOXO3a signalling pathway to suppress STING activation and promote ischaemic flap survival.

Sequential transplantation of exosomes and BMSCs pretreated with hypoxia efficiently facilitates perforator skin flap survival area in rats

Bone marrow mesenchymal stem cells (BMSC) are promising candidates for the treatment of trans-territory perforator flap necrosis. However, the low retention and survival rate of engrafted BMSCs limit their therapeutic efficacy. Strategies either modifying BMSCs or alleviating the inflammatory environment may solve this problem. Thus, we aimed to explore the therapeutic efficacy of sequential transplantation of exosomes and hypoxia pretreated BMSCs on flap necrosis. After the perforator flap model was created, the exosomes derived from BMSCs were injected immediately into choke zone II followed by transplantation of hypoxia pretreated BMSCs on Day 2. Gross view was performed to assess the flap survival, enzyme-linked immunosorbent assay was performed to evaluate the inflammatory factor level, microvessel number was assessed and quantitative polymerase chain reaction (qPCR) was performed to assess angiogenesis. We found that exosome delivery significantly reduced inflammatory cytokines levels on Day 1 and Day 3 and promoted the engrafted BMSCs’ survival on Day 7. After combining with transplantation of hypoxia pretreated BMSCs, the flap survival rate and the angiogenesis-related gene expression were significantly higher than in the other three groups; the von Willebrand factor (vWF) vascular diameter and vWF vascular count were significantly higher than in the phosphate buffered saline (PBS) group. Thus, we concluded that sequential transplantation of exosomes and BMSCs combinatorially pretreated with hypoxia further facilitated flap survival. This sequential transplantation approach provides novel insights into the clinical treatment of flap necrosis.

L-Borneol promotes skin flap survival by regulating HIF-1α/NF-κB pathway

Ethnopharmacological relevanceThe clinical application of skin flaps in surgical reconstruction is frequently impeded by the occurrence of distant necrosis. L-Borneol exhibits myogenic properties in traditional Chinese medicine and is used in clinical settings to promote wound healing and conditions such as stroke. Nevertheless, the precise mechanism by which borneol exerts its protective effects on skin flap survival remains unclear. Aim of the studyTo explore the potential of L-borneol to promote skin flap survival and elucidate the underlying mechanisms. Materials and methodsThirty-six male Sprague–Dawley rats were randomly divided into three groups: a high-dose (200 mg/kg L-borneol per day), a low-dose (50 mg/kg/day), and control group (same volume of solvent). In each rat, a modified rectangular McFarlane flap model measuring 3 × 9 cm was constructed. Daily intragastric administration of L-borneol or solvent was performed. The flap was divided into three square sections of equal size, namely Zone I (the proximal zone), Zone II (the intermediate zone), and Zone III (the distal zone). The survival rate was quantified, and the histological state of each flap was evaluated on the seventh day following the surgical procedure. The assessment of angiogenesis was conducted using lead oxide/gelatin angiography, whereas the evaluation of blood flow in the free flap was performed using laser Doppler flow imaging. Superoxide dismutase activity was detected using the water-soluble tetrazolium salt-8 method. The quantities of vascular endothelial growth factor, interleukin (IL)-1β, IL-6, and tumour necrosis factor-α were determined using immunohistochemistry. The levels of nuclear transcription factor-κB, hypoxia-inducible factor-1, B-cell lymphoma-2 (BCL-2), and BCL-2-associated X (BAX) were determined by Western blotting technique. ResultsFlap survival rate significantly improved and neutrophil recruitment and release were enhanced after treatment with the compound. Angiogenesis was promoted. L-borneol protected against oxidative stress by increasing superoxide dismutase activity and decreasing malondialdehyde content. It downregulated the hypoxia-inducible factor nuclear transcription factor-κB pathway, leading to the inhibition of several inflammatory factors. Simultaneously, it facilitated the expression of vascular endothelial growth factor and BCL-2. ConclusionThe study shows that L-borneol may promote skin flap survival by inhibiting HIF-1α/NF-κB pathway.