Review: ischaemia–reperfusion injury in flap surgery

Effect of surgery on oxidative stress and endogenous tocopherol concentrations in juvenile female dogs

BACKGROUND

Surgery such as ovariectomy causes an inflammatory and oxidative stress. This study was designed to evaluate endogenous tocopherol levels in response to surgical oxidative stress induced by abdominal surgery (ovariectomy) in thirty-two juvenile female dogs. The dogs received meloxicam before surgery (0.2 mg/kg SC) and after surgery (0.1 mg/kg OS every 24 h), 0.03 mg/kg of atropine sulfate (IM), and propofol 4 mg/kg intravenously (IV). General anesthesia was maintained with sevoflurane. Physiological, hematological and biochemical parameters, malondialdehyde (MDA) and α-, δ-, γ-tocopherols were evaluated at baseline, 36 and 48 h after surgery.

RESULTS

The physiological parameters remained within normal ranges. Blood glucose concentration increased, while the albumin levels decreased after surgery. Rescue analgesia was not required. MDA levels increased above the baseline at 36 and 48 h after surgery (P < 0.001). The α-, δ-, and γ-tocopherol concentrations decreased from baseline at 36 and 48 h after surgery (P < 0.001).

CONCLUSIONS

Surgery in juvenile female dogs revealed oxidative, increased MDA concentrations, reduced tocopherol levels, and had a clinically insignificant influence on homeostasis.

Effect of corticosteroids on ischemia-reperfusion injury of deep inferior epigastric perforator flap after re-exploration for anastomosis thrombosis: A prospective randomized trial

Patients undergoing breast reconstruction with the deep inferior epigastric perforator (DIEP) flap are at risk of arterial and venous thrombosis, necessitating flap salvage surgery. However, this carries the risk of ischemia-reperfusion injury (IRI) and potential significant partial or complete flap loss. The objective of this study was to evaluate the potential benefit of corticosteroids in reducing IRI related complications in DIEP flaps that are returned to the operation theater for attempted salvage after venous or arterial failure. A double-blinded prospective randomized study was conducted between January 2012 and January 2023 on patients scheduled for secondary unilateral breast reconstruction using the DIEP flap technique. Patients were included if they developed post-operative venous or arterial flap thrombosis and experienced DIEP flap IRI following operative take-back and anastomosis revision. The treatment group (TG) received a 5-day course of corticosteroids, while the control group (CG) did not receive any specific treatment. Forty-six patients were enrolled in the study. In the CG, two cases of total flap loss and eight cases of partial flap necrosis were observed, while the TG had only 1 case of partial flap necrosis (p < 0.05). The complete resolution of clinical signs of IRI occurred within 13 ± 2.1 days for the TG and 21 ± 3.5 days for the CG (p = 0.00001). The TG had a significantly shorter hospital stay (11.13 ± 0.38 days) compared with the CG (15.47 ± 1.27 days; p < 0.0001). Targeted corticosteroid therapy following a salvage procedure for vascular thrombosis in DIEP flaps has shown promise as an effective treatment for subsequent IRI. This approach may be considered as a viable option for managing IRI in free flaps. However, further studies involving a larger number of patients are required to substantiate our hypothesis.

Fabrication of a tailor-made conductive polyaniline/ascorbic acid-coated nanofibrous mat as a conductive and antioxidant cell-free cardiac patch

Polyaniline (PANI) wasin-situpolymerized on nanofibrous polycaprolactone mats as cell-free antioxidant cardiac patches (CPs), providing electrical conductivity and antioxidant properties. The fabricated CPs took advantage of intrinsic and additive antioxidant properties in the presence of PANI backbone and ascorbic acid as a biocompatible dopant of PANI. The antioxidant nature of CPs may reduce the serious repercussions of oxidative stress, produced during the ischemia-reperfusion (I/R) process following myocardial infarction. The polymerization parameters were considered as aniline (60 mM, 90 mM, and 120 mM), ascorbic acid concentrations ([aniline]:[ascorbic acid] = 3:0, 3:0.5, 3:1, 3:3), and polymerization time (1 h and 3 h). Mainly, the more aniline concentrations and polymerization time, the less sheet resistance was obtained. 1,1 diphenyl-2-picrylhydrazyl (DPPH) assay confirmed the dual antioxidant properties of prepared samples. The advantage of the employedin-situpolymerization was confirmed by the de-doping/re-doping process. Non-desirable groups were excluded based on their electrical conductivity, antioxidant properties, and biocompatibility. The remained groups protected H9c2 cells against oxidative stress and hypoxia conditions. Selected CPs reduced the intracellular reactive oxygen species content and mRNA level of caspase-3 while the Bcl-2 mRNA level was improved. Also, the selected cardiac patch could attenuate the hypertrophic impact of hydrogen peroxide on H9c2 cells. Thein vivoresults of the skin flap model confirmed the CP potency to attenuate the harmful impact of I/R.

Supramolecular Assembly Based on Calix(4)arene and Aggregation-Induced Emission Photosensitizer for Phototherapy of Drug-Resistant Bacteria and Skin Flap Transplantation

Photodynamic therapy as a burgeoning and non-invasive theranostic technique has drawn great attention in the field of antibacterial treatment but often encounters undesired phototoxicity of photosensitizers during systemic circulation. Herein, a supramolecular substitution strategy is proposed for phototherapy of drug-resistant bacteria and skin flap repair by using macrocyclic p-sulfonatocalix(4)arene (SC4A) as a host, and two cationic aggregation-induced emission luminogens (AIEgens), namely TPE-QAS and TPE-2QAS, bearing quaternary ammonium group(s) as guests. Through host-guest assembly, the obtained complex exhibits obvious blue fluorescence in the solution due to the restriction of free motion of AIEgens and drastically inhibits efficient type I ROS generation. Then, upon the addition of another guest 4,4'-benzidine dihydrochloride, TPE-QAS can be competitively replaced from the cavity of SC4A to restore its pristine ROS efficiency and photoactivity in aqueous solution. The dissociative TPE-QAS shows a high bacterial binding ability with an efficient treatment for methicillin-resistant Staphylococcus aureus (MRSA) in dark and light irradiation. Meanwhile, it also exhibits an improved survival rate for MRSA-infected skin flap transplantation and largely accelerates the healing process. Thus, such cascaded host-guest assembly is an ideal platform for phototheranostics research.

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.

Pharmacological and cell-based treatments to increase local skin flap viability in animal models

Local skin flaps are frequently employed for wound closure to address surgical, traumatic, congenital, or oncologic defects. (1) Despite their clinical utility, skin flaps may fail due to inadequate perfusion, ischemia/reperfusion injury (IRI), excessive cell death, and associated inflammatory response. (2) All of these factors contribute to skin flap necrosis in 10-15% of cases and represent a significant surgical challenge. (3, 4) Once flap necrosis occurs, it may require additional surgeries to remove the entire flap or repair the damage and secondary treatments for infection and disfiguration, which can be costly and painful. (5) In addition to employing appropriate surgical techniques and identifying healthy, well-vascularized tissue to mitigate the occurrence of these complications, there is growing interest in exploring cell-based and pharmacologic augmentation options. (6) These agents typically focus on preventing thrombosis and increasing vasodilation and angiogenesis while reducing inflammation and oxidative stress. Agents that modulate cell death pathways such as apoptosis and autophagy have also been investigated. (7) Implementation of drugs and cell lines with potentially beneficial properties have been proposed through various delivery techniques including systemic treatment, direct wound bed or flap injection, and topical application. This review summarizes pharmacologic- and cell-based interventions to augment skin flap viability in animal models, and discusses both translatability challenges facing these therapies and future directions in the field of skin flap augmentation.

Nesfatin-1 regulates the HMGB1-TLR4-NF-κB signaling pathway to inhibit inflammation and its effects on the random skin flap survival in rats

OBJECTIVE

Random skin flaps are often placed by plastic surgeons to treat limb deformities and dysfunction. Nesfatin-1 (NES) is a peptide that exerts angiogenic, anti-inflammatory, and anti-oxidant effects. We assessed the impact of NES on flap survival and the underlying mechanism.

METHODS

We modified the McFarlane random skin flap rat model. Thirty-six male Sprague-Dawley rats were randomly divided into a control group (corn oil solution with DMSO), low-dose group (NES-L at 10 µg/kg/day), and high-dose group (NES-H at 20 µg/kg/day). On day 7 after surgery, average flap survival areas were calculated. Laser Doppler blood flow monitoring and lead oxide/gelatin angiography were used to evaluate blood perfusion and neovascularization, respectively. Flap histopathological status was evaluated by hematoxylin and eosin (H&E) staining. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) were determined. Immunohistochemical techniques were used to evaluate the expression of angiogenetic and inflammatory factors.

RESULTS

In the experimental groups, the mean skin flap survival areas and blood perfusion increased considerably. The SOD activities in the experimental groups increased and the MDA contents decreased. Immunohistochemically, VEGF expression was upregulated in the experimental groups and the expression levels of inflammatory factors decreased markedly.

CONCLUSION

NES inhibited ischemic skin flap necrosis, promoted angiogenesis, and reduced ischemia-reperfusion injury and inflammation. Inhibition of the inflammatory HMGB1-TLR4-NF-κB signal pathway, which reduced flap inflammation and oxidative stress, may explain the enhanced flap survival.

Outcome analysis of free flap reconstruction for head and neck cancer with intraoperative indocyanine green angiography

BACKGROUND

Intraoperative indocyanine green (ICG) angiography is used in free flap surgery to evaluate the patency of vessel anastomosis. This study evaluated the outcomes of intraoperative ICG angiography in free flap surgery for head and neck cancer.

MATERIALS AND METHODS

This was a retrospective study of free flap reconstruction for head and neck cancer performed between 2015 and 2021. The outcomes analyzed were the total flap failure rate, re-exploration rate, and flap salvage rate. Differences in outcomes were compared in patients treated using intraoperative ICG angiography and those treated without.

RESULTS

Of the 520 free flap surgeries in the 486 enrolled patients, 259 cases underwent intraoperative ICG angiography. In this group, there were 10 (3.9%) cases of total flap failure. In the non-ICG group, there were 22 cases (8.4%). There were 35 (13.5%) cases requiring re-exploration in the ICG group and 40 (15.3%) in the non-ICG group. The difference was not statistically significant. The flap salvage rate was 75.8% (25/33) in the ICG group and 51.4% (18/35) in the non-ICG group, which was a significant difference.

CONCLUSION

We found that free flap surgery with intraoperative ICG angiography significantly decreased total flap failure rate and significantly increased salvage rate but did not significantly affect the re-exploration rate.

Procyanidin B2 regulates the Sirt1/Nrf2 signaling pathway to improve random-pattern skin flap survival

Random-pattern skin flaps have been widely used in the reconstruction of damaged tissues. Ischemia-reperfusion injury occurring in the distal regions of the flap is a common issue, which often leads to flap necrosis and restricts its clinical applications. Procyanidin B2 (PB2), a naturally occurring flavonoid in large quantities in various fruits, has been demonstrated to exhibit several significant pharmacological properties. However, the effect of PB2 on flap viability is not clearly known. Here, using Western blot analysis, immunohistochemistry, and immunofluorescence staining, we observed that PB2 significantly reduced oxidative stress and inflammation and enhanced angiogenesis. Mechanically, we provided evidence for the first time that the beneficial effects of PB2 occur through the activation of the Sirt1/Nrf2 signaling pathway. Moreover, co-administration of PB2 and EX527, a selective inhibitor of Sirt1, resulted in down-regulation of the expression of Sirt1, Nrf2, and downstream antioxidants. In summary, our study showed that PB2 might be a novel therapeutic strategy for improving the survival of random-pattern skin flaps.

A new fasciocutaneous flap model identifies a critical role for endothelial Notch signaling in wound healing and flap survival

Flap surgery is a common treatment for severe wounds and a major determinant of surgical outcome. Flap survival and healing depends on adaptation of the local flap vasculature. Using a novel and defined model of fasciocutaneous flap surgery, we demonstrate that the Notch ligand Delta-like 1 (Dll1), expressed in vascular endothelial cells, regulates flap arteriogenesis, inflammation and flap survival. Utilizing the stereotyped anatomy of dorsal skin arteries, ligation of the major vascular pedicle induced strong collateral vessel development by end-to-end anastomosis in wildtype mice, which supported flap perfusion recovery over time. In mice with heterozygous deletion of Dll1, collateral vessel formation was strongly impaired, resulting in aberrant vascularization and subsequent necrosis of the tissue. Furthermore, Dll1 deficient mice showed severe inflammation in the flap dominated by monocytes and macrophages. This process is controlled by endothelial Dll1 in vivo, since the results were recapitulated in mice with endothelial-specific deletion of Dll1. Thus, our model provides a platform to study vascular adaptation to flap surgery and molecular and cellular regulators influencing flap healing and survival.

Therapeutic potential of naringin in improving the survival rate of skin flap: A review

Naringin is the main component of Drynaria. Modern pharmacological studies have shown that naringin has a wide range of pharmacological activities, including antioxidant, anti-inflammatory, anti-apoptotic, anti-ulcer, and anti-osteoporosis effects. Its therapeutic effects have been observed in various clinical models, such as atherosclerosis, cardiovascular diseases, diabetes, neurodegenerative diseases, and rheumatic diseases. This review investigates the pharmacological effects of naringin and the associated mechanisms in improving flap survival. This review will also provide a reference for future rational application of naringin, especially in research to improve flap survival.

Prussian Blue Nanozyme Promotes the Survival Rate of Skin Flaps by Maintaining a Normal Microenvironment

Ischemia-reperfusion (I/R) injury leads to a low success rate of skin flap transplantation in reconstruction surgery, thus requiring development of new treatments. Necroptosis and apoptosis pathways, along with overexpression of reactive oxygen species and pro-inflammatory factors in skin flap transplantation, are deemed as potential therapeutic targets. This study provides a paradigm for nanozyme-mediated microenvironment maintenance to improve the survival rate of the transplanted skin flap. Prussian blue nanozyme (PBzyme) with multiple intrinsic biological activities was constructed and selected for this proof-of-concept study. The prepared PBzyme shows anti-inflammatory, antiapoptotic, antinecroptotic, and antioxidant activities in both in vitro and in vivo models of I/R injured skin flaps. The multiple inhibitory effects of PBzyme maintained a normal microenvironment and thus significantly promoted the survival rate of the I/R injured skin flap (from 37.21 ± 8.205% to 79.61 ± 7.5%). Of note, PBzyme regulated the expression of the characteristic signal molecules of necroptosis, including Rip 1, Rip 3, and pMLKL, indicating that PBzyme may be a therapeutic agent for necroptosis-related diseases. This study shows great prospects for clinical application of PBzyme in the treatment of skin flaps via local administration.

Activating Parkin-dependent mitophagy alleviates oxidative stress, apoptosis, and promotes random-pattern skin flaps survival

The random-pattern skin flap is a crucial technique in reconstructive surgery and flap necrosis caused by ischemia/reperfusion injury is a major postoperative complication. Herein, we investigated the mechanism of mitophagy induced by Melatonin (ML) and its effect on the survival of skin flaps. Our results demonstrated that ML could activate mitophagy, ameliorate oxidative stress and alleviate apoptosis in Tert-Butyl hydroperoxide solution (TBHP)-stimulated human umbilical vein endothelial cells in vitro. Inhibiting ML-induced mitophagy considerably abolished its protective effects. Moreover, knockdown of Parkin by siRNA inhibited ML-induced mitophagy, and subsequently exacerbated oxidative stress and apoptosis. Further study demonstrated that inhibition of AMPK reversed these protective effects of ML and downregulated the expression of TFEB. In the vivo study, ML effectively promoted flap survival by activating mitophagy and subsequently ameliorating oxidative stress and mitigating apoptosis. These results established that ML is a potent agent capable for increasing random-pattern skin flap survival by activating Parkin-dependent mitophagy through the AMPK-TFEB signaling pathway.

The Promising Effect of Topiramate on Random-Pattern Skin Flap Survival in Rats

BACKGROUND

Partial necrosis of skin flaps following plastic and reconstructive surgeries is one of the major problems in these medical interventions. This study was conducted to evaluate the beneficial effects of topiramate an anti-epileptic agent on ischemic random skin flaps.

MATERIALS AND METHODS

Twenty-four Wistar rats were provided and randomly divided into four experimental groups (control group and low-, intermediate- and high-dose treatment groups). A rat random-pattern skin flap model was performed in all groups, and animals in the low-, intermediate- and high-dose experimental groups were administered topiramate intraperitoneally at doses of 25, 50 and 100 mg/kg, respectively, 1 h before raising the flap and once daily for 7 consecutive days after the initial surgical procedure. Control rats received vehicle according to the same schedule. On postoperative day 7 the flap necrotic area was measured, and tissue samples were stained with hematoxylin and eosin for histological analysis. Furthermore, the oxidative stress in flap tissue was assessed by measuring the activity of superoxide dismutase (SOD), glutathione (GSH) level and the content of malondialdehyde (MDA).

RESULTS

Treating animals with 50 and 100 mg/kg topiramate significantly decreased the necrotic flap areas as compared to the control group. Histological studies demonstrated that in intermediate and high dose topiramate groups the inflammatory cell numbers were attenuated and microvessel development were markedly increased. Furthermore, the MDA contents were significantly reduced and GSH levels were significantly increased in these groups as compared to the control group. However, the SOD activity was increased significantly only in high-dose group as compared to the control group.

CONCLUSIONS

These findings indicated that topiramate in doses of 50 and 100 mg/kg increases random skin flap survival.

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Anaesthesia for reconstructive free flap surgery for head and neck cancer

Head and neck cancer surgery presents significant challenges for the anaesthetist. A thorough multidisciplinary preoperative assessment and optimisation of the patient is essential, including nutritional and psychological evaluation. The incidence of a difficult airway is high, and the anaesthetist must be skilled in advanced airway techniques. Surgery is extensive, often requiring reconstructive surgery with either a pedicled or free flap. Detailed knowledge of flap physiology and anatomy is needed, and anaesthesia comprises careful management of mean arterial pressure, fluid administration, temperature control and oxygenation. The Enhanced Recovery after Surgery Society and the Society for Head and Neck Anaesthesia consensus recommendations provide guidance on current best practice. Despite continued debate, it now appears that this constitutes goal-directed fluid therapy, coupled with judicious vasopressor therapy sufficient to achieve an adequate mean arterial pressure. Emerging techniques such as prehabilitation and postoperative near-infrared spectroscopy flap monitoring provide hope of improved outcomes going forward.

Tissue-Protective Mechanisms of Bioactive Phytochemicals in Flap Surgery

Despite careful preoperative planning, surgical flaps are prone to ischemic tissue damage and ischemia–reperfusion injury. The resulting wound breakdown and flap necrosis increase both treatment costs and patient morbidity. Hence, there is a need for strategies to promote flap survival and prevent ischemia-induced tissue damage. Phytochemicals, defined as non-essential, bioactive, and plant-derived molecules, are attractive candidates for perioperative treatment as they have little to no side effects and are well tolerated by most patients. Furthermore, they have been shown to exert beneficial combinations of pro-angiogenic, anti-inflammatory, anti-oxidant, and anti-apoptotic effects. This review provides an overview of bioactive phytochemicals that have been used to increase flap survival in preclinical animal models and discusses the underlying molecular and cellular mechanisms.

Hydrogen-generating Si-based agent protects against skin flap ischemia-reperfusion injury in rats

Hydrogen is effective against ischemia–reperfusion (I/R) injury in skin flaps. However, the difficulty of continuously administering a sufficient amount of hydrogen using conventional methods has been an issue in the clinical application of hydrogen-based therapy. An Si-based agent administered orally was previously shown to continuously generate a large amount of hydrogen in the intestinal environment. In this study, we assessed the effect of the Si-based agent on the inhibition of I/R injury in skin flaps using a rat model. In the I/R groups, the vascular pedicle of the abdominal skin flap was occluded for three hours followed by reperfusion. In the I/R + Si group, the Si-based agent was administered perioperatively. After reperfusion, flap survival rate, blood flow, oxidative stress markers, inflammatory markers/findings, and degree of apoptosis were evaluated. Flap survival rate was significantly higher, and histological inflammation, apoptotic cells, oxidative stress markers, and levels of inflammatory cytokine mRNA and protein expression were significantly lower, in the I/R + Si group compared to the I/R group. The Si-based agent suppressed oxidative stress, apoptosis, and inflammatory reactions resulting from I/R injury, thereby contributing to improvements in skin flap survival.

Effects of Distal Arterial Supercharging and Distal Venous Superdrainage on the Survival of Multiterritory Perforator Flaps in Rats

BACKGROUND

Which one of the two measures, distal arterial supercharging (DAS) and distal venous superdrainage (DVS), is better to enhance flap survival? No consistent conclusions have been reached.

METHODS

All flaps were pedicled on the deep circumflex iliac vessels. Seventy-two healthy male rats were distributed to four groups randomly: DAVS group (distal arteriovenous supercharging group), the thoracodorsal (TD) artery and TD vein were preserved; DAS group (distal arterial supercharging group), the TD vein was ligated; DVS group (distal venous superdrainage group), the TD artery was ligated; control group, the TD artery and TD vein were ligated. Flap survival rate was evaluated on postoperative day 7. Flap angiography was performed to assess vascular changes of the flap. Microvascular density (MVD) was evaluated by hematoxylin and eosin staining, and CD34-positive microvessel density was measured by immunohistochemistry. Vascular endothelial growth factor (VEGF) level was measured by western blot. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) were evaluated using specialized commercial kits.

RESULTS

The mean flap survival rate was increased significantly in DAVS and DAS groups than in DVS and control groups. DAVS and DAS groups had higher flap vascularization, MVD, CD34-positive microvessel density, VEGF expression and SOD level compared to DVS and control groups. DAVS and DAS groups also had lower MDA level relative to DVS and control groups.

CONCLUSION

DAS is more conducive to improving the survival rate of the multiterritory perforator flap compared to DVS, mainly by enhancing angiogenesis and preventing ischemia-reperfusion (I/R) injury.

Liberal versus Modified Intraoperative Fluid Management in Abdominal-flap Breast Reconstructions. A Clinical Study

Background:

The outcome of reconstructive microsurgery is influenced by the intraoperative anesthetic regimen. The aim of this study was to compare the impact on the intra- and postoperative complication rates of our modified fluid management (MFM) protocol with a previously used liberal fluid management protocol in abdominal-flap breast reconstructions.

Methods:

This retrospective study analyzed adverse events related to secondary unilateral abdominal-flap breast reconstructions in two patient cohorts, one with a liberal fluid management protocol and one with a MFM protocol. In the MFM protocol, intravenous fluid resuscitation was restricted and colloid use was minimized. Both noradrenaline and propofol were implemented as standard in the MFM protocol. The primary endpoints were surgical and medical complications, as observed intraoperatively or postoperatively, during or shortly after the hospital stay.

Results:

Of the 214 patients included in the study, 172 patients followed the MFM protocol. Prior radiotherapy was more frequent in the MFM protocol. Surgical procedures to achieve venous superdrainage were more often used in the MFM cohort. Intraoperative as well as postoperative complications occurred significantly more frequently in the liberal fluid management cohort and were specifically associated with partial and total flap failures. Prior radiotherapy, additional venous drainage, or choice of inhalation agent did not have an observable impact on outcome.

Conclusions:

The incidence of adverse events during and after autologous breast reconstructive procedures was reduced with the introduction of an MFM protocol. Strict intraoperative fluid control combined with norepinephrine and propofol was both beneficial and safe.

Protective effects of sodium ferulate on flap transplantation via anti-inflammatory modulation and oxidative stress inhibition

Ischemia-reperfusion injury (IRI) has brought attention to flap failure in reconstructive surgery. To improve the prognosis of skin transplantation, we performed experimental IRI by surgical obstruction of blood flow and used sodium ferulate (SF) to prevent IRI in rats. After SF treatment, the morphological and histological changes of the skin flaps were observed by H&E and Masson's trichrome staining. We also detected the expression levels of COX-1, HO-1, and Ki67 by immunohistochemical and western blot analysis. Moreover, enzyme-linked immunosorbent assay was used to identify the content of tumor necrosis factor (TNF)-α, myeloperoxidase (MPO), malondialdehyde (MDA), and nitric oxide (NO) in peripheral blood and skin tissue. Compared with the model group, SF treatment significantly improved the recovered flap area (%) and promoted collagen synthesis. Cyclooxygenase-2 (COX-2) expression was significantly inhibited by heme oxygenase-1 (HO-1) induction after SF treatment. Furthermore, SF significantly inhibited the levels of TNF-α in peripheral blood, MPO and MDA in the skin tissue, and the increased synthesis of NO. Our results showed the protective effects of SF on IRI after flap transplantation and we believe that the protective effects of SF was closely related to the alleviation of the inflammatory response and the inhibition of the oxidative stress injury.

Protective Effect of Hydrogen Gas on Mouse Hind Limb Ischemia-Reperfusion Injury

BACKGROUND

The aim of this study was to investigate the mechanism of hydrogen gas on hind limb IR injury.

METHODS

Male C57BL/6 mice were randomly divided into three groups: sham group (Sham), ischemia-reperfusion group (IR), IR plus H₂ inhalation group (IR + H₂). IR was induced by interrupting hind limb blood flow for 3h, followed by 4h of reperfusion, and H₂ was administered by inhalation throughout the reperfusion process. Our data show that H₂ inhalation could significantly decrease the infarct-affected tissue volume (P < 0.05), attenuate the degree of morphological injury (P < 0.05), and suppress the level of oxidative stress damage (P < 0.05), compared with the IR group. In exploring the underlying mechanisms, we found that hydrogen could markedly mitigate the degree of IR-induced ER stress and apoptosis (P < 0.05). Additionally, hydrogen could markedly inhibit the IR injury by modulating the phosphorylated c-Jun N-terminal kinase (JNK) signaling pathway (P < 0.05).

CONCLUSIONS

Taken together, these results revealed the protective effect of hydrogen gas on hind limb ischemia reperfusion injury on mice by attenuating oxidative stress, impairing ER stress and apoptosis, and its ability to modulate JNK signaling pathway.

Apigenin enhances viability of random skin flaps by activating autophagy

Random skin flap is widely used in plastic surgery. However, flap necrosis caused by ischemia-reperfusion injury limits its clinical applications. Apigenin, a naturally occurring flavonoid mainly derived from plants, facilitates flap survival. In this study, we explored the effects of apigenin on flap survival and the underlying mechanisms. A total of 54 mice having a dorsal random flap model were randomly divided into control, apigenin, and apigenin +3-methyladenine groups. These groups were treated with dimethyl sulfoxide solution, apigenin, and apigenin +3-methyladenine, respectively. The animals were then euthanized to assess angiogenesis, apoptosis, oxidative stress, and autophagy levels through histological and protein analyses. Apigenin promotes survival of the skin flap area and reduces tissue edema. In addition, apigenin enhanced angiogenesis, attenuated apoptosis, alleviated oxidative stress, and activated autophagy. Interestingly, 3-methyladenine reversed the effects of apigenin on flap survival, angiogenesis, apoptosis, and oxidative stress through inhibition of autophagy. The findings of this study show that apigenin promotes angiogenesis, inhibits cell apoptosis, and lowers oxidative stress by mediating autophagy, thus the improving survival rate of random skin flaps.

Positive Effect of Andrographolide Induced Autophagy on Random-Pattern Skin Flaps Survival

Random-pattern skin flap replantation is generally used in the reconstruction of surgical tissues and covering a series of skin flap defects. However, ischemia often occurs at the flap distal parts, which lead to flap necrosis. Previous studies have shown that andrographolide (Andro) protects against ischemic cardiovascular diseases, but little is known about the effect of Andro on flap viability. Thus, our study aimed to building a model of random-pattern skin flap to understand the mechanism of Andro-induced effects on flap survival. In this study, fifty-four mice were randomly categorized into the control, Andro group, and the Andro+3-methyladenine group. The skin flap samples were obtained on postoperative day 7. Subsequently, the tissue samples were underwent a series of evaluations such as changes in the appearance of flap tissue, the intensity of blood flow, and neovascularization density of skin flap. In our study, the results revealed that Andro enhanced the viability of random skin flaps by enhancing angiogenesis, inhibiting apoptosis, and reducing oxidative stress. Furthermore, our results have also demonstrated that the administration of Andro caused an elevation in the autophagy, and these remarkable impact of Andro were reversed by 3-methyladenine (3-MA), the most common autophagy inhibitor. Together, our data proves novel evidence that Andro is a potent modulator of autophagy capable of significantly increasing random-pattern skin flap survival.

Preclinical efficacy of stem cell therapy for skin flap: a systematic review and meta-analysis

Background

A skin flap is one of the most critical surgical techniques for the restoration of cutaneous defects. However, the distal necrosis of the skin flap severely restricts the clinical application of flap surgery. As there is no consensus on the treatment methods to prevent distal necrosis of skin flaps, more effective and feasible interventions to prevent skin flaps from necrosis are urgently needed. Stem therapy as a potential method to improve the survival rate of skin flaps is receiving increasing attention.

Methods

This review followed the recommendations from the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statements. Twenty studies with 500 animals were included by searching Web of Science, EMBASE, PubMed, and Cochrane Library databases, up until October 8, 2020. Moreover, the references of the included articles were searched manually to obtain other studies. All analyses were conducted using Review Manager V.5.3 software.

Results

Meta-analysis of all 20 studies demonstrated stem cell treatment has significant effects on reducing necrosis of skin flap compared with the control group (SMD: 3.20, 95% CI 2.47 to 3.93). Besides, subgroup analysis showed differences in the efficacy of stem cells in improving the survival rate of skin flaps in areas of skin flap, cell type, transplant types, and method of administration of stem cells. The meta-analysis also showed that stem cell treatment had a significant effect on increasing blood vessel density (SMD: 2.96, 95% CI 2.21 to 3.72) and increasing the expression of vascular endothelial growth factor (VEGF, SMD: 4.34, 95% CI 2.48 to 6.1).

Conclusions

The preclinical evidence of our systematic review indicate that stem cell-based therapy is effective for promoting early angiogenesis by up regulating VEGF and ultimately improving the survival rate of skin flap. In summary, small area skin flap, the administration method of intra-arterial injection, ASCs and MSCs, and xenogenic stem cells from humans showed more effective for the survival of animal skin flaps. In general, stem cell-based therapy may be a promising method to prevent skin flap necrosis.

Effect of intravenous lidocaine on ischemia-reperfusion injury in DIEP microsurgical breast reconstruction. A prospective double-blind randomized controlled clinical trial

BACKGROUND

Ischemia-reperfusion injury in free flaps is associated with tissue damage and is one of the main factors causing flap failure in reconstructive microsurgery. The aim of this study is to assess whether any ischemia-reperfusion injury takes place during a microsurgical flap reconstruction as seen through the levels of malondialdehyde (MDA) and superoxide dismutase, biomarkers of oxidative stress, and to analyze the effect of lidocaine in this process.

METHODS

Twenty-four patients operated for immediate breast reconstruction using the Deep Inferior Epigastric Perforator free flap technique were divided into two groups: one group was treated with a lidocaine intravenous perfusion and the other group with a saline perfusion. MDA and superoxide dismutase (SOD) levels were measured at several points before, during, and after surgery.

RESULTS

There was an increase in MDA levels in both groups, but the lidocaine group experienced a decrease during reperfusion. On the other hand, we observed a rise in SOD levels in both groups, but a decrease during reperfusion in the placebo group. However, these differences between groups were not statistically significant.

CONCLUSIONS

The decreased SOD activity and increased MDA content in our research prove a redox imbalance and high reactive oxygen species levels in flaps, indicating that tissues experience ischemia-reperfusion injury during microsurgical reconstruction. Lidocaine may have a protective effect in free flap surgery, but our results were not statistically significant, so further studies will be required.

Effects of Ischemic Preconditioning and C1 Esterase Inhibitor Administration following Ischemia-Reperfusion Injury in a Rat Skin Flap Model

BACKGROUND

 Ischemia-reperfusion (I/R) injury is a serious condition that can affect the success rate of microsurgical reconstructions of ischemic amputated limbs and complex tissue defects requiring free tissue transfers. The purpose of this study was to evaluate the effects of ischemic preconditioning (IPC) and C1 esterase inhibitor (C1-Inh) intravenous administration following I/R injury in a rat skin flap model.

METHODS

 Superficial caudal epigastric skin flaps (3 cm × 7 cm) were performed on 50 Wistar rats that were randomly divided into five groups. Ischemia was not induced in the control group. All other flaps underwent 8 hours of ischemia prior to revascularization: I/R control group (8-hour ischemia), IPC group (preconditioning protocol + 8-hour ischemia), C1-Inh group (8-hour ischemia + C1-Inh), and IPC + C1-Inh group (preconditioning protocol + 8-hour ischemia + C1-Inh). Survival areas were macroscopically assessed after 1 week of surgery, and histopathological and biochemical evaluations were also measured.

RESULTS

 There were no significant differences in flap survival between the treatment groups that were suffering 8 hours of ischemia and the control group. A significant increase in neovascularization and lower edema formation were observed in the IPC group compared with that in the I/R group. Biochemical parameters did not show any significant differences.

CONCLUSION

 Intravenous administration of C1-Inh did not significantly modulate I/R-related damage in this experimental model, but further research is needed. On the other hand, IPC reduces tissue damage and improves neovascularization, confirming its potential protective effects in skin flaps following I/R injury.

Pharmacological Effects of Fasudil on Flap Survival in a Rodent Model

BACKGROUND

Necrosis of the perforator flap is a critical problem. Fasudil, an inhibitor of Rho-associated coiled-coil containing kinase, has antiapoptosis activity and attenuates oxidative stress in many diseases. We characterized the effects of fasudil through intraperitoneal injection on perforator flap survival and identified its possible mechanism.

METHODS AND MATERIALS

Rats were divided into a control group (without surgery), a flap group (only surgery), and a fasudil group (surgery plus fasudil). Perforator flaps were made on the backs of the rats. The expression of vascular endothelial growth factor, the protein kinase B (PKB/Akt), endothelial nitric oxide synthase, Bax, Bcl-2, Beclin-1, P62, and LC3 II/LC3 I was determined by Western blot at day 3 after surgery. Nitric oxide (NO) components, superoxide dismutase, and malondialdehyde were also measured at day 3. The survival rate and laser Doppler perfusion imaging were performed at day 7 after surgery.

RESULT

The group with fasudil treatment exhibited the higher survival rates and angiogenesis levels. Fasudil also induced the activation of Akt/eNOS/NO pathway detected by the Western blot and NO expression kit. Furthermore, Western blot results showed fasudil-attenuated apoptosis through a raised Bcl-2/Bax rate and enhanced autophagy levels through raised beclin-1, decreased p62, and the elevated rate of LC3 II/LC3 I. Finally, fasudil increased superoxide dismutase and decreased malondialdehyde.

CONCLUSIONS

In conclusion, fasudil treatment decreased necrosis of perforator flaps possibly by affecting the Akt/eNOS/NO pathway, attenuating apoptosis and activating autophagy.

Detrimental Effect of Sitagliptin Induced Autophagy on Multiterritory Perforator Flap Survival

Multiterritory perforator flap survival is commonly applied in surgical tissue reconstructions and covering of large skin defects. However, multiple risk factors such as ischemia, reperfusion injury, and apoptosis after reconstructive surgeries cause necrosis in distal parts with outcomes ranging from poor aesthetic appearance to reconstructive failure. A few studies have reported that sitagliptin (Sit) promotes angiogenesis and inhibits apoptosis. However, little is known about Sit-induced autophagy especially on the flap model. Therefore, our study investigated the effect of Sit and its induced autophagy on the perforator flap survival. Ninety male Sprague-Dawley rats were randomly separated into control, Sit, and Sit+3-methyladenine group. Results revealed that Sit significantly promoted flap survival by enhancing angiogenesis, reducing oxidative stress, and attenuating apoptosis. In addition, flap survival was further improved after co-administration with 3-methyladenine to inhibit autophagy. Overall, our results established that Sit has positive effects in promoting survival of multiterritory perforator flap. Sit-induced autophagy was detrimental for flap survival and its inhibition may further improve flap survival.

New techniques and recommendations in the management of free flap surgery for head and neck defects in cancer patients

Free flap surgery is the gold standard surgical treatment for head and neck defects in cancer patients. Outcomes have improved considerably, probably due to recent advances in surgical techniques. In this article, we review improvements in the parameters traditionally used to optimize hematocrit levels and body temperature and to prevent vasoconstriction, and describe the use of cardiac output-guided fluid management, a technique that has proved useful in other procedures. Finally, we review other parameters used in free flap surgery, such as clotting/platelet management and nutritional optimization.

Increase of major complications with a longer ischemia time in breast reconstruction with a free deep inferior epigastric perforator (DIEP) flap

Background

The deep inferior epigastric artery perforator (DIEP) flap is one of the most used free flaps for postmastectomy breast reconstruction. Prolonged ischemia can result in (partial) flap loss. The aim of this study was to evaluate the association between ischemia time and postoperative complications of DIEP flap breast reconstruction.

Methods

A retrospective study of all patients who received a breast reconstructionwith aDIEP flap atMaastricht University Medical Center in theNetherlands, between January 2010 and June 2017 (n = 677). The flaps were divided into two groups: flaps with an ischemia time less than 60 min and those with 60 min or more. Recipient site complications, in particular major complications equal to re-exploration, and partial or total flap loss were the primary outcome measures.

Results

In 23.9% of the 677 included DIEP flaps, the ischemia time was 60 min or longer. Within this group, a complication of the recipient site occurred in 30.9% of the flaps. A major complication occurred in 17.3% of the flaps with 60 min or more ischemia time.With regard to the flaps with less than 60-min ischemia time, a complication occurred in 22.1% of the cases of which 8.9%would be considered amajor complication. A significant association was found between ischemia time and major complications on univariate (p value = 0.003) and multivariate analyses (p value = 0.016).

Conclusions

This study demonstrates that an ischemia time less than 60 min is associated with a significantly lower risk of major recipient site complications compared to an ischemia time of 60 min or more.

Level of evidence: Level III, therapeutic, risk/prognostic study.

Effect of short-term ischemia on microcirculation and wound healing of adipocutaneous flaps in the rat

PURPOSE

Composite flaps used in reconstructive surgery may intra- and postoperatively suffer from hypoperfusion and/or ischemia-reperfusion influencing wound healing. We aimed to follow-up the effect of ischemia on adipocutaneous flaps' wound healing and microcirculation.

METHODS

In anesthetized rats groin flaps were formed bilaterally. In Control group the flaps were repositioned and sutured back. In Ischemia-Reperfusion (I/R) group before repositioning and suturing the flap pedicles were clamped for 60 minutes. Laser Doppler (LD) fluxmetry and temperature probes were applied on the cranial, central and caudal flap regions before/after preparation and ischemia, re-suturing, and on the 1st-3rd-5th-7th-14th postoperative days, before the final examinations and biopsies for histology.

RESULTS

Flaps' skin temperature quickly recovered after repositioning. LD values were lower in the I/R group, reaching a significant level by the 3rd postoperative day, and remained lowered till the 14th day. The magnitude of alterations differed in the flap regions. Histologically normal wound healing process was seen, except for some I/R flaps, where hypertrophized mammary glands were found.

CONCLUSIONS

Short-term ischemia could influence flap microcirculation and wound healing, and may result in hypertrophized mammary glands. Laser Doppler could be used to evaluate intra- and postoperative microcirculatory changes and may have significance in predicting complications.

Dietary Nitrate Protects Against Skin Flap Ischemia-Reperfusion Injury in Rats via Modulation of Antioxidative Action and Reduction of Inflammatory Responses

Dietary nitrate, found abundant in green vegetables, can be absorbed into the blood and be converted to nitric oxide (NO) in the body. Dietary nitrate has been proved to have many positive physiological functions in the body. Here, we evaluated the therapeutic effects of dietary nitrate on skin flap recovery following ischemia reperfusion (IR). Wistar rats were pretreated with nitrate from one week prior to ischemia to the end of reperfusion. It was found that oral administration of nitrate increased serum nitrate and nitrite levels, protected cells from apoptosis, and attenuated flap tissue edema. In the meantime, the oxidative stress marker malondialdehyde was reduced, while the activities of antioxidant enzymes were restored after nitrate treatment. Moreover, the macrophage and neutrophil infiltration in the flap was significantly attenuated by nitrate supplementation, as were the pro-inflammatory cytokines. In sum, we found that oral administration of nitrate can attenuate skin flap IR injury through the regulation of oxidative stress and inflammatory response.

Intra-arterial injection of human adipose-derived stem cells improves viability of the random component of axial skin flaps in nude mice

BACKGROUND

Skin flap necrosis is a common postoperative complication in reconstructive surgery. Recent evidence suggests that subcutaneously injected adipose-derived stem cells (ASCs) increase the viability of random skin flaps. Here, we examined whether intra-arterial human ASC administration could improve random component survival of axial skin flaps in nude mice.

METHODS

Human ASCs isolated from a healthy volunteer by liposuction were injected into nude mice through the right femoral artery at a low (1 × 10³ cells), medium (1 × 10⁴ cells), or high (1 × 10⁵ cells) dose. After ASC infusion, right superficial inferior epigastric vessels were ligated to create unipedicled superficial inferior epigastric artery (SIEA) flap with random extension.

RESULTS

Flap survival was higher in mice from all three ASC-treated groups, and particularly the medium-dose group was 30% better, than in the control group. Histological examination demonstrated a significantly higher vascular density in the axial skin flap in nude mice treated with the medium ASC dose than in control mice. PKH26-labeled ASCs were identified in skin flaps of ASC-treated mice; some endothelial cells exhibited positive staining for human HLA-A. Compared to the control group, mice in ASC-treated groups had higher vascular endothelial growth factor levels and lower tumor necrosis factor α, interferon γ, and interleukin-6 levels.

CONCLUSIONS

Intra-arterial human ASC administration increased the survival of axial skin flaps by attenuating inflammatory reactions and enhancing neovascularization. Intra-arterial ASC administration might yield a higher rate of these cells and of engraftment in the skin flaps. This approach may have a therapeutic role in increasing flap survival.

Intraluminal fluid infusion in a rat jejunum ischemia/reperfusion model is associated with improved tissue perfusion and less mucosal damage

OBJECTIVE

This study used an experimental model mimicking early postoperative enteral feeding after the transfer of free jejunal flap and tested the hypothesis that jejunal infusion with dextrose or saline is associated with improved tissue perfusion and/or less mucosal damage after ischemia/reperfusion (IR) injury.

METHODS

Thirty-five male Sprague Dawley rats were randomly divided into five groups: sham group (no IR and no intraluminal infusion); IR control group (IR but not intraluminal infusion); IR plus intraluminal 0.9% NaCl infusion or 5% dextrose or 10% dextrose infusion groups. A jejunal segment of each rat was isolated. The animals had jejunal ischemia for 40 min, reperfusion, and intestinal infusion on the basis of their allocation. Jejunal tissue perfusion was measured with laser Doppler flowmetry at one hour and two hours after reperfusion, after which the animals were sacrificed and tissue samples were obtained for the scoring of histological damage at superficial and cryptic epithelium, villus structure, and inflammatory cell infiltration and tissue nitric oxide (NO), interleukin (IL)-1, IL-6, and matrix metalloproteinase-1 (MMP) level measurements.

RESULTS

At 1 h of reperfusion, IR plus 5% dextrose and 10% dextrose groups both had significantly higher perfusion rates than the IR control group (384.8 ± 26.7 and 462.4 ± 44.7 versus 270.3 ± 34.2 PU, respectively, p < 0.05 for both). These differences were maintained at 2 h of reperfusion (p < 0.05 for both). Saline infusion, however, resulted in improved tissue perfusion only at the early phase of reperfusion. Intraluminal infusion with dextrose solution, either 5% or 10%, was associated with higher tissue NO, IL-1, and IL-6 levels than that in the sham group (p < 0.05 for all). In addition, intraluminal infusion of any fluid resulted in less severe histological damage (8.1 ± 0.9 versus 5.8 ± 1.0, 5.4 ± 0.9, and 5.2 ± 1.9, for IR plus saline, 5% dextrose and 10% dextrose groups, respectively, p < 0.05 for all).

CONCLUSIONS

Intraluminal infusion of fluids, particularly dextrose solutions, may be protective against IR injury as demonstrated by improved tissue perfusion and less histological damage. In addition, increases in tissue NO, IL-1, and IL-6 levels in association with dextrose infusion may be explained by the activation of pro-inflammatory and anti-inflammatory protective pathways. These support early enteral feeding after free jejunum flap transfers; however, further studies are warranted.

Betulinic Acid Enhances the Viability of Random-Pattern Skin Flaps by Activating Autophagy

Random-pattern skin flap replantation is commonly used to repair skin defects during plastic and reconstructive surgery. However, flap necrosis due to ischemia and ischemia-reperfusion injury limits clinical applications. Betulinic acid, a plant-derived pentacyclic triterpene, may facilitate flap survival. In the present study, the effects of betulinic acid on flap survival and the underlying mechanisms were assessed. Fifty-four mice with a dorsal random flap model were randomly divided into the control, betulinic acid group, and the betulinic acid + 3-methyladenine group. These groups were treated with dimethyl sulfoxide, betulinic acid, and betulinic acid plus 3-methyladenine, respectively. Flap tissues were acquired on postoperative day 7 to assess angiogenesis, apoptosis, oxidative stress, and autophagy. Betulinic acid promoted survival of the skin flap area, reduced tissue edema, and enhanced the number of microvessels. It also enhanced angiogenesis, attenuated apoptosis, alleviated oxidative stress, and activated autophagy. However, its effects on flap viability and angiogenesis, apoptosis, and oxidative stress were reversed by the autophagy inhibitor 3-methyladenine. Our findings reveal that betulinic acid improves survival of random-pattern skin flaps by promoting angiogenesis, dampening apoptosis, and alleviating oxidative stress, which mediates activation of autophagy.

Necroptosis was found in a rat ischemia/reperfusion injury flap model

Background:

Necroptosis is a new form of cell death that has been identified as a third pathway causing cell death. In this study, necrostatin-1 (Nec-1) was used to determine whether necroptosis exists in a rat ischaemia/reperfusion injury flap model.

Methods:

In this study, twenty male Sprague-Dawley rats were divided randomly into two groups: a control group (CTL group) and a Nec-1 group. Each abdominal skin flap underwent 3 h of ischaemia and then reperfusion. Fifteen minutes before and after reperfusion, phosphate buffer saline (PBS) was administered intraperitoneally to the CTL group, while Nec-1 was administered intraperitoneally to the Nec-1 group. Twenty-four hours after reperfusion, the whole flap was divided equally into 54 sections. Flap blood perfusion was measured. One sample was taken randomly from each row. Morphological changes, apoptosis, receptor-interacting protein-1 (RIP-1) expression and caspase-3 activity were observed and detected. The measurements between the two groups were compared with the independent t-test, and a P value of <0.05 was considered statistically significant.

Results:

Compared to flaps in the CTL group, flaps in the Nec-1 group showed longer survival rates, better blood perfusion and less inflammatory infiltration. The total flap area considered to have survived was 70.88 ± 10.28% in the CTL group, whereas 80.56 ± 5.40% of the area was found to be living in the Nec-1 group (Nec-1 vs. CTL, t = –2.624, P < 0.05). For some rows, there were significant differences in cell apoptosis between the two groups, the apoptosis index (AI) in rows “9 cm”, “7 cm”, “6 cm” and “5 cm” was significantly lower in the Nec-1 group than that in the CTL group (Nec-1 vs. CTL, P < 0.05). RIP-1 expression was much lower in the Nec-1 group than that in the CTL group in rows “5 cm” to “9 cm” (Nec-1 vs. CTL, P < 0.05). No significant differences in caspase-3 activity were found.

Conclusion:

According to the results, necroptosis was present in a rat abdominal ischaemia/reperfusion injury flap model.

Effects of bradykinin on the survival of multiterritory perforator flaps in rats

Background

Bradykinin, a vasoactive peptide, has many biological functions. For example, it accelerates angiogenesis. Thus, we studied the effects of bradykinin on the survival of perforator flaps.

Methods

Averagely, 50 male Sprague–Dawley rats were divided into control and bradykinin groups and underwent procedures to the multiterritory perforator flap. Areas of flap survival were tested 7 days later. Flap perfusion was evaluated by laser Doppler imaging. We assessed the extent of autophagy by determining LC3-II/I, Beclin 1, and p62. Flap angiogenesis was assessed by immunohistochemistry and H&E staining. We measured the level of vascular endothelial growth factor (VEGF) protein using western blot. We assessed oxidative stress by measuring the activity of superoxide dismutase (SOD) and malondialdehyde (MDA) levels. The apoptotic index was also evaluated by western blot, and we determined nitric oxide (NO) production using an NO assay kit.

Results

The bradykinin group exhibited significantly larger areas of flap survival, higher blood supply, and more neovascularization. The bradykinin group also had higher SOD activity, higher VEGF expression and NO content, and reduced MDA compared to the control group. Rats treated with bradykinin also had lower levels of apoptosis and autophagy relative to the control group.

Conclusion

Our results suggest that bradykinin promotes the survival of multiterritory perforator flaps by increasing angiogenesis, promoting the release of NO, suppressing apoptosis, reducing oxidative stress, and inhibiting autophagy.

Ischemia-reperfusion injury in a rat microvascular skin free flap model: A histological, genetic, and blood flow study

Ischemia reperfusion injury is associated with tissue damage and inflammation, and is one of the main factors causing flap failure in reconstructive microsurgery. Although ischemia-reperfusion (I/R) injury is a well-studied aspect of flap survival, its biological mechanisms remain to be elucidated. To better understand the biological processes of ischemia reperfusion injury, and to develop further therapeutic strategies, the main objective of this study was to identify the gene expression pattern and histological changes in an I/R injury animal model. Fourteen rats (n = 7/group) were randomly divided into control or ischemia-reperfusion group (8 hours of ischemia). Microsurgical anastomoses were objectively assessed using transit-time-ultrasound technology. Seven days after surgery, flap survival was evaluated and tissue samples were harvested for anatomopathological and gene-expression analyses.The I/R injury reduced the survival of free flaps and histological analyses revealed a subcutaneous edema together with an inflammatory infiltrate. Interestingly, the Arginase 1 expression level as well as the ratio of Arginase 1/Nitric oxide synthase 2 showed a significant increase in the I/R group. In summary, here we describe a well-characterized I/R animal model that may serve to evaluate therapeutic agents under reproducible and controlled conditions. Moreover, this model could be especially useful for the evaluation of arginase inhibitors and different compounds of potential interest in reconstructive microsurgery.

Beneficial Effect of U-74389 G and Sildenafil in An Experimental Model of Flap Ischemia/Reperfusion Injury in Swine. Histological and Biochemical Evaluation of the Model

Purpose of the study: Tissue reconstruction after burns, tumor excisions, infections or injuries is a frequent surgical challenge to avoid Ischemia-reperfusion injury. Lazaroids and sildenafil, through their mechanisms of action, have been studied for their protective effects on various organs subjected to IRI. In this study, we aimed to evaluate the therapeutic potential of U-74389G and sildenafil in a swine model of ischemia and reperfusion injury of latissimus dorsi flap. Materials and methods: Forty-two Landrace male pigs, weighing 28-35 kg, were equally (n = 6) randomized into the following groups: (a) Group I: control, (b) Group II: administration of U-74389G after ischemia, (c) Group III: administration of sildenafil after ischemia, (d) Group IV: administration of U-74389G and sildenafil after ischemia, (e) Group V: administration of U-74389G prior to ischemia, (f) Group VI: administration of sildenafil prior to ischemia, and (g) Group VII: administration of U-74389G and sildenafil prior to ischemia. Blood and tissue sampling was conducted before ischemia, 15 and 30 min after occlusion, 30, 60, 90, and 120 min after reperfusion. Results: Statistically significant reduction (p < 0.05) was detected in lymphocytes and polymorphonuclear leukocytes concentrations as well as in the appearance of edema after histopathologic evaluation of the ischemic tissue, especially in the groups of combined treatment. Measurements of malondialdeyde and tumour necrosis factor alpha in tissues revealed a significant decrease (p < 0.001) of these markers in the treatment groups when compared to the control, particularly in the latest estimated timepoints. Conclusions: The synergistic action of U-74389G and sildenafil seems protective and promising in cases of flap IRI during tissue reconstruction surgery.

Effect of Human Placental Extract Treatment on Random-Pattern Skin Flap Survival in Rats

Background: Human placental extract (HPE), prepared from the placentas of healthy, postpartum females, displays various physiological activities, including antioxidative properties. In this study, a dorsal skin flap model was used to investigate the effect of HPE on flap viability in rats. Materials and methods: Forty male Sprague-Dawley rats underwent random-pattern skin flap surgeries. The animals were randomly divided among a control group and three treatment groups (localized injection (LI), 10 mg/kg/d localized HPE injections; low-dose treatment (LT), 10 mg/kg/d systemic HPE injections; high-dose treatment (HT), 40 mg/kg/d systemic HPE injections). Surviving skin flap areas were measured 7 days after surgery and tissue samples were stained with hematoxylin and eosin; vascular endothelial growth factor expression was determined immunohistochemically. To evaluate the antioxidant and antiapoptotic effects of HPE, malondialdehyde, glutathione peroxidase, and caspase-3 levels were examined. Results: Seven days after surgery, HPE-treated animals had significantly reduced necrotic areas, rats receiving the highest HPE dose demonstrated the greatest flap survival. In the HPE groups, the histopathological scores were lower than for the control group. Immunohistochemistry showed markedly more numerous vascular endothelial growth factor-positive cells in the HT group than in the C group. Malondialdehyde levels were significantly lower and glutathione peroxidase levels were higher in the HT group than in the C group. HPE treatment significantly inhibited apoptosis by lowering caspase-3 activity. Conclusions: HPE treatment yielded positive effects on flap survival, due to its antioxidant and antiapoptotic properties. These results suggest a new therapeutic approach for enhancing flap viability and accelerating wound repair.

Beneficial effect of botulinum toxin A on secondary ischaemic injury of skin flaps in rats

Botulinum toxin A (BTX-A) protects against primary ischaemia of skin flaps, but its effect on secondary ischaemia is unknown. We induced secondary arterial or venous ischaemia in skin flaps of 32 Wistar rats, and tested the effectiveness of BTX injected subcutaneously 12hours before the flap was raised. The animals were divided into two groups of 16 (arterial or venous). Eight animals in each group were then treated with saline 1ml (control), and eight with BTX-A 5 IU (treatment). Ischaemia and necrosis were assessed after five days. There was no significant difference in necrosis between the two treatments in either group, but the amount of ischaemia did differ significantly (p=0.031 in the artetial ishcemia and p=0.015 in the venous ischemia group). BTX helped to salvage poor reperfusion in secondary ischaemia of skin flaps.

Detrimental effect of Hypoxia-inducible factor-1α-induced autophagy on multiterritory perforator flap survival in rats

Hypoxia-inducible factor-1α (HIF-1α) plays a key role in angiogenesis, improves flap survival, and activates autophagy. The effect of HIF-1α-induced autophagy is still debatable. Thus, we investigated the effect of HIF-1α-induced autophagy on multiterritory perforator flap survival. In this study, 99 male Sprague-Dawley rats received multiterritory perforator flap procedure and were divided into three groups with 33 each. The dimethyloxalylglycine (DMOG) plus 3-methyladenine (3-MA) group received intraperitoneal injection of DMOG (40 mg/kg) and 3-MA (10 mg/kg). The DMOG group and control group received comparative DMOG and saline respectively. On postoperative day (POD) 7, HIF-1α’s activities of flap survival and perfusion improvement were confirmed in DMOG group, however, its positive effects were further enhanced by co-administration of autophagy inhibitor, 3-MA. On POD 1, vascular endothelial growth factor, mean microvascular density and blood perfusion were not affected by HIF-1α up-regulation or autophagy inactivation. However, HIF-1α-induced autophagy augments apoptosis and oxidative stress. The increased level of apoptosis and oxidative stress was reversed by 3-MA and resulted in further flap survival improvement. In conclusion, HIF-1α-induced autophagy has a detrimental effect on multiterritory perforator flap survival and the flap survival was determined by the combined effects of ischemia and reperfusion injury.

Impact of groin flap ischemia-reperfusion on red blood cell micro-rheological parameters in a follow-up study on rats

BACKGROUND

Flap hypoperfusion or ischemia-reperfusion (I/R) may occur during preparation-transposition procedures and by postoperative thrombotic complications. Behind the microcirculatory disturbances micro-rheological alterations are also supposed.

OBJECTIVE

We aimed to investigate the groin flap I/R with following-up micro-rheological parameters.

METHODS

Anesthetized rats were subjected to Control or I/R groups. Groin flaps were prepared bilaterally, pedicled on the superficial epigastric vessels. In Control group the flaps were re-sutured after one hour, while in I/R group microvascular clips were applied on the pedicles for 60 minutes, then the flaps were repositioned. Besides daily wound control, before the operation and on the 1st, 3rd, 5th, 7th and 14th postoperative days blood samples were collected for testing red blood cell (RBC) deformability (rotational ektacytometry) and aggregation (light-transmission aggregometry).

RESULTS

RBC deformability significantly worsened by the 3rd-7th postoperative day in I/R group. RBC aggregation enhanced significantly by the 1st day, in I/R group it remained elevated on the 3rd day as well. In a complicated case with unilateral flap necrosis, RBC deformability and aggregation worsening was outlined from its group (base, 1st, 3rd day).

CONCLUSION

Wound healing affected micro-rheological parameters in the early postoperative period. Flap I/R exacerbated the alterations. The parameters markedly worsened in case of flap necrosis.