Improvement of Flap Necrosis in a Rat Random Skin Flap Model by In Vivo Electroporation-Mediated HGF Gene Transfer

Celastrol enhances the viability of random-pattern skin flaps by regulating autophagy through the AMPK-mTOR-TFEB axis

In reconstructive and plastic surgery, random-pattern skin flaps (RPSF) are often used to correct defects. However, their clinical usefulness is limited due to their susceptibility to necrosis, especially on the distal side of the RPSF. This study validates the protective effect of celastrol (CEL) on flap viability and explores in terms of underlying mechanisms of action. The viability of different groups of RPSF was evaluated by survival zone analysis, laser doppler blood flow, and histological analysis. The effects of CEL on flap angiogenesis, apoptosis, oxidative stress, and autophagy were evaluated by Western blot, immunohistochemistry, and immunofluorescence assays. Finally, its mechanistic aspects were explored by autophagy inhibitor and Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) inhibitor. On the seventh day after surgery, the survival area size, blood supply, and microvessel count of RPSF were augmented following the administration of CEL. Additionally, CEL stimulated angiogenesis, suppressed apoptosis, and lowered oxidative stress levels immediately after elevated autophagy in ischemic regions; These effects can be reversed using the autophagy inhibitor chloroquine (CQ). Specifically, CQ has been observed to counteract the protective impact of CEL on the RPSF. Moreover, it has also been discovered that CEL triggers the AMPK-mTOR-TFEB axis activation in the area affected by ischemia. In CEL-treated skin flaps, AMPK inhibitors were demonstrated to suppress the AMPK-mTOR-TFEB axis and reduce autophagy levels. This investigation suggests that CEL benefits the survival of RPSF by augmenting angiogenesis and impeding oxidative stress and apoptosis. The results are credited to increased autophagy, made possible by the AMPK-mTOR-TFEB axis activation.

VEGF and Other Gene Therapies Improve Flap Survival-A Systematic Review and Meta-Analysis of Preclinical Studies

Surgical flaps are basic tools in reconstructive surgery. Their use may be limited by ischemia and necrosis. Few therapies address or prevent them. Genetic therapy could improve flap outcomes, but primary studies in this field present conflicting results. This systematic review and meta-analysis aimed to appraise the efficacy of external gene delivery to the flap for its survival in preclinical models. This review was registered with PROSPERO (CRD42022359982). PubMed, Embase, Web of Science, and Scopus were searched to identify studies using animal models reporting flap survival outcomes following any genetic modifications. Random-effects meta-analysis was used to calculate mean differences in flap survival with accompanying 95% CI. The risk of bias was assessed using the SYRCLE tool. Subgroup and sensitivity analyses were performed to ascertain the robustness of primary analyses, and the evidence was assessed using the GRADE approach. The initial search yielded 690 articles; 51 were eventually included, 36 of which with 1576 rats were meta-analyzed. VEGF gene delivery to different flap types significantly improved flap survival area by 15.66% (95% CI 11.80-19.52). Other interventions had smaller or less precise effects: PDGF-13.44% (95% CI 3.53-23.35); VEGF + FGF-8.64% (95% CI 6.94-10.34); HGF-5.61% (95% CI 0.43-10.78); FGF 3.84% (95% CI 1.13-6.55). Despite considerable heterogeneity, moderate risk of bias, and low quality of evidence, the efficacy of VEGF gene therapy remained significant in all sensitivity analyses. Preclinical data indicate that gene therapy is effective for increasing flap survival, but further animal studies are required for successful clinical translation.

Reversible adhesives with controlled wrinkling patterns for programmable integration and discharging

Switchable and minimally invasive tissue adhesives have great potential for medical applications. However, on-demand adherence to and detachment from tissue surfaces remain difficult. We fabricated a switchable hydrogel film adhesive by designing pattern-tunable wrinkles to control adhesion. When adhered to a substrate, the compressive stress generated from the bilayer system leads to self-similar wrinkling patterns at short and long wavelengths, regulating the interfacial adhesion. To verify the concept and explore its application, we established a random skin flap model, which is a crucial strategy for repairing severe or large-scale wounds. Our hydrogel adhesive provides sufficient adhesion for tissue sealing and promotes neovascularization at the first stage, and then gradually detaches from the tissue while a dynamic wrinkling pattern transition happens. The gel film can be progressively ejected out from the side margins after host-guest integration. Our findings provide insights into tunable bioadhesion by manipulating the wrinkling pattern transition.

The therapeutic effect of PEI-Fe3O4/pYr-ads-8-5HRE-cfosp-IFNG albumin nanospheres combined with magnetic fluid hyperthermia on hepatoma

Background

Hepatocellular carcinoma (HCC) is one of the most prevalent and deadly malignant tumors with serious clinical and socioeconomic consequences. Although gene therapy holds great promise in the treatment of hepatoma, its clinical applications are hindered by uncontrolled gene transmission and transcription.

Methods

The pY-ads-8-5HRE-cfosp-IFNG plasmid was constructed and identified by double enzyme digestion and gene sequencing. The expression of pYr-ads-8-5HRE-cfosp-IFNG in HepG2 cells was detected by quantitative PCR. PEI-Fe3O4/pYr-ads-8-5HRE-cfosp-IFNG albumin nanospheres were prepared and characterized. In vitro heating test of magnetic albumin nanospheres in an alternating magnetic field (AMF) was carried out. The therapeutic effect of PEI-Fe3O4/pYr-ads-8-5HRE-cfosp-IFNG albumin nanospheres on hepatocellular carcinoma was investigated by cell and animal experiments. After treatment, mice blood was collected for clinical biochemical analysis and histopathological evaluation of major organs was performed to assess potential adverse effects of treatment.

Results

Double enzyme digestion and gene sequencing showed that the pY-ads-8-5HRE-cfosp-IFNG plasmid was constructed successfully. QPCR results showed that the IFNγ transcript level in the PEI-Fe3O4/pYr-ads-8-5HRE-cfosp-IFNG group was higher than that in the PEI-Fe3O4/pYr-ads-8-cfosp-IFNG group after being treated with hypoxia (P<0.05). TEM revealed that the self-prepared PEI-Fe3O4/pYr-ads-8-5HRE-cfosp-IFNG albumin nanospheres exhibit an approximately spherical or elliptical shape. The hydrodynamic size of the albumin nanospheres was 139.7 nm. The maximum temperature of 0.25 mg/mL solution is stable at about 44°C, which is suitable for tumor thermal therapy without damaging normal tissues. The relative cell inhibition rate of the radiation-gene therapy and MFH combination group was higher than that of other control groups in CCK8 experiment. (P<0.05) Flow cytometry showed that the apoptosis rate and necrosis rate of the combined treatment group were 42.32% and 35.73%, respectively, higher than those of the other groups. (P<0.05) In animal experiments, the mass and volume inhibition rates of the combined treatment group were 66.67% and 72.53%, respectively, higher than those of other control groups. (P<0.05) Clinical biochemical analysis and histopathological evaluation showed no abnormality.

Conclusions

The results indicated the successful construction of the radiation-induced plasmid and demonstrated that the hypoxia enhancer could augment the expression of INFγ in a hypoxia environment. Gene therapy combined with magnetic fluid hyperthermia (MFH) has exhibited excellent outcomes in both cell and animal studies. Our experiments demonstrated that the PEI-Fe3O4/pYr-ads-8-5HRE-cfosp-IFNG albumin nanospheres system is a comprehensive treatment method for hepatoma, which can effectively combine immune genre therapy with hyperthermia.

Sinomenine promotes flap survival by upregulating eNOS and eNOS-mediated autophagy via PI3K/AKT pathway

Large skin defects and surgical tissue reconstructions are frequently covered utilizing random flaps. The flap has the advantage of being designed according to the size and shape of a surgical wound. However, the necrosis of the distal part of the flap restricts the clinical application of flaps. Sinomenine (SIN) is the major active component of sinomenium acutum. SIN has been demonstrated to inhibit oxidative stress and stimulate autophagy in a cell, animal, and clinical studies. The protective and proliferative effects of sinomenium on HUVECs were evaluated by scratched test, CCK-8, and EDU assays. For the flap survival, we established a mouse random pattern flap model and observed the effects of SIN injected intraperitoneally. The survival area and blood flow intensity of the flap in sinomenium group were significantly increased compared to the control group. Our results demonstrate that SIN promotes flap survival. Sinomenium enhances eNOS expression in the flap and reduces the level of oxidative stress, promotes autophagy flux increase, reduces apoptosis, and promotes angiogenesis. Having a therapeutic benefit of SIN, Autophagy inhibitor 3-MA shows its critical role by reversing the beneficial effects of SIN, and the nitric oxide synthase inhibitor l-NAME both stimulated HUVECs that explore the relationship between autophagy flux and nitric oxide synthase. Furthermore, the mechanism in our study reveals the changes in the signal pathway of PI3K/AKT, the protective effect of SIN during antioxidant activity, the activation of eNOS through PI3K/AKT signaling pathway affects autophagy through the eNOS system, and promote the random flap survival.

Berberine promotes the viability of random skin flaps via the PI3K/Akt/eNOS signaling pathway

Random skin flaps are often used in reconstruction operations. However, flap necrosis is still a common postoperative complication. Here, we investigated whether berberine (C₂₀ H₁₉ NO₅ , BBR), a drug with antioxidant activity, improves the survival rate of random flaps. Fifty-four rats were divided into three groups: control, BBR and BBR + _L -NAME groups (_L -NAME, _L -N^G -Nitro-arginine methyl ester). The survival condition and the percentage of survival area of the flaps were evaluated on the seventh day after surgery. After animals were sacrificed, angiogenesis, apoptosis, oxidative stress and inflammation levels were assessed by histological and protein analyses. Our findings suggest that berberine promotes flap survival. The level of angiogenesis increased; the levels of oxidative stress, inflammation and apoptosis decreased; the levels of phosphoinositide 3-kinase (PI3K), phospho-Akt (p-Akt) and phospho-endothelial nitric oxide synthase (p-eNOS) increased in the flap tissue; and _L -NAME reversed the effects of berberine on random skin flaps. Statistical analysis showed that the BBR group results differed significantly from those of the control and the BBR + _L -NAME groups (p < .05). Our results confirm that berberine is an effective drug for significantly improving the survival rate of random skin flaps by promoting angiogenesis, inhibiting inflammation, attenuating oxidative stress, and reducing apoptosis through the PI3K/Akt/eNOS signaling pathway.

Effects of limonin treatment on the survival of random skin flaps in mice

Random skin flap is commonly used in plastic and reconstructive surgery, however, distal part of skin flap often occurs ischemia and necrosis. Limonin, with bioactivities of anti-inflammation, anti-apoptosis and anti-oxidative stress, may be effective for skin flap survival. In our study, random flap model was performed in mice to explore the role of limonin in the survival of skin flap. On postoperative day 7, the necrosis of skin flaps was observed, while visualization of blood flow below the tissue surface was detected through Laser Doppler blood flow imaging (LDBFI). Then flap tissues were acquired to assess and levels of angiogenesis, apoptosis and oxidative stress. The results showed that limonin decreased necrosis and edema of skin flaps compared with the control group, with more blood flow in the flap under LDBFI detection. Limonin treatment also increased the mean vessels density, elevated the expression levels of angiogenic proteins (matrix metallopeptidase 9, vascular endothelial growth factor, Cadherin5) and antioxidant proteins [superoxide dismutase 1 (SOD1), endothelial nitric oxide synthase, heme oxygenase], and reduced the expression of apoptotic factors (BAX, CYC, Caspase3). In summary, limonin could effectively enhance the survival of random skin flap, the potential mechanism may attribute to the induction of angiogenesis, and inhibition of apoptosis and oxidative stress.

Exosomes Derived from Bone Marrow Mesenchymal Stem Cells Alleviate Ischemia-Reperfusion Injury and Promote Survival of Skin Flaps in Rats

Free tissue flap transplantation is a classic and important method for the clinical repair of tissue defects. However, ischemia-reperfusion (IR) injury can affect the success rate of skin flap transplantation. We used a free abdomen flap rat model to explore the protective effects of exosomes derived from bone marrow mesenchymal stem cells (BMSCs-exosomes) against the IR injury of the skin flap. Exosomes were injected through the tail vein and the flaps were observed and obtained on day 7. We observed that BMSCs-exosomes significantly reduced the necrotic lesions of the skin flap. Furthermore, BMSCs-exosomes relieved oxidative stress and reduced the levels of inflammatory factors. Apoptosis was evaluated via the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and Western blot analysis of Bax, Bcl-2. Simultaneously, BMSCs-exosomes promoted the formation of new blood vessels in the IR flap, as confirmed by the increased expression level of VEGFA and the fluorescence co-staining of CD31 and PCNA. Additionally, BMSCs-exosomes considerably increased proliferation and migration of human umbilical vein endothelial cells and promoted angiogenesis in vitro. BMSCs-exosomes could be a promising cell-free therapeutic candidate to reduce IR injury and promote the survival of skin flaps.

The Use of Infrared Thermography in Determining Timing for Early Pedicle Division of the Preexpanded Bipedicled Visor Flap after Ischemic Preconditioning

Background

The preexpanded bipedicled visor flap, supported by the bilateral superficial temporal vessels, stands as an ideal choice for upper and lower lip reconstruction in males. However, the bilateral tissue bridges after flap transfer caused patients significant cosmetic deformity and psychological burden. Early division of bilateral pedicles reduced the length of hospitalization and expenses. In this study, infrared thermography (IRT) was used to guide the early pedicle division after ischemic preconditioning.

Methods

This study retrospectively analyzed patients who underwent preexpanded bipedicled visor flap surgery from April 2018 to October 2021. Pedicle division was scheduled at two weeks postflap transfer. Ischemic preconditioning was initiated 3-5 days in advance by repeatedly clamping both pedicles. The temperature alteration of the flap and the temperature difference compared to the normal adjacent tissue were evaluated by IRT. The division surgery was not scheduled until the perfusion assessment indicated adequate. This comprised of subjective examination and indocyanine green angiography. The threshold of temperature difference to determine the pedicle division was analyzed based on the temperature changes between the clamps.

Results

A total of 8 male patients successfully conducted the pedicle division without any complications. The delay period after ischemic preconditioning ranged from 14 to 19 days (average 16 days). Through ischemic preconditioning training, the average temperature of the flap gradually increased from 31.85 ± 0.36°C to 33.89 ± 0.50°C, and the temperature difference with the normal surrounding tissues decreased from 2.89 ± 0.30°C to 1.15 ± 0.46°C (95% confidence interval (1.5, 0.8)). The temperature difference stayed unchanged after pedicle division.

Conclusion

Ischemic preconditioning shortens the perioperative period to pedicle division. Monitoring the temperature change reflects the revascularization between the flap and the recipient site, thus guiding the pedicle division. The temperature difference less than 1.5°C after clamping both pedicles can be set as the safe threshold for pedicle division.

Prevention of necrosis in ischemic skin flaps using hydrogel of Rhizophora mangle

INTRODUCTION

Necrosis in ischemic cutaneous flaps (ISF) is a type of surgical failure more feared among surgical complications. Currently, synthetic drugs are applied during the treatment of necrosis in ISF and although several substances show improvement in viability, some require application at high systemic doses, which can produce important side effects. Therefore, the search for natural substances with fewer side effects is constant. The use of medicinal plants that stimulate angiogenesis is commonly mentioned in previous studies and in this case Rhizophora mangle L. (R. mangle) highlights that among its main compounds have tannins and flavonoids that are very chemically reactive in various biological activities. This study aimed to associate a natural hydrogel to the 5% extract of R. mangle and to evaluate its potential in the prevention of tissue necrosis in distal portions of ISF in rats, using the model proposed by Macfarlane, et al. (1965).

METHODS

Ischemic skin flaps were made in the thin dorsal skin area of 28 Wistar rats and divided into 4 groups, group A: received only saline, group B where the aqueous extract of R. mangle was applied, group C received the 1.5% hydrogel of xanthan gum (XG) + placebo and group D was applied the hydrogel associated with 5% R. mangle extract. Morphometric analyses of the areas of tissue necrosis were performed from photographic records using the software Photoshop® and ImageJ®. In addition, 5 photomicrographs were taken from each histological sample of each animal for histomorphometric analysis that obtained the count of fibroblasts and blood vessels.

RESULTS

The mean percentage of necrotic areas was: group (A) - 50,66%, group (B) - 40,49%, group (C) - 37,44% and group (D) - 34,25%. The statistical analysis, using the Kruskal-Wallis test, showed a significant difference (p < 0.001).

Endothelial Phospholipase Cγ2 Improves Outcomes of Diabetic Ischemic Limb Rescue Following VEGF Therapy

Therapeutic vascular endothelial growth factor (VEGF) replenishment has met with limited success for the management of critical limb-threatening ischemia. To improve outcomes of VEGF therapy, we applied single-cell RNA sequencing (scRNA-seq) technology to study the endothelial cells of the human diabetic skin. Single-cell suspensions were generated from the human skin followed by cDNA preparation using the Chromium Next GEM Single-cell 3' Kit v3.1. Using appropriate quality control measures, 36,487 cells were chosen for downstream analysis. scRNA-seq studies identified that although VEGF signaling was not significantly altered in diabetic versus nondiabetic skin, phospholipase Cγ2 (PLCγ2) was downregulated. The significance of PLCγ2 in VEGF-mediated increase in endothelial cell metabolism and function was assessed in cultured human microvascular endothelial cells. In these cells, VEGF enhanced mitochondrial function, as indicated by elevation in oxygen consumption rate and extracellular acidification rate. The VEGF-dependent increase in cell metabolism was blunted in response to PLCγ2 inhibition. Follow-up rescue studies therefore focused on understanding the significance of VEGF therapy in presence or absence of endothelial PLCγ2 in type 1 (streptozotocin-injected) and type 2 (db/db) diabetic ischemic tissue. Nonviral topical tissue nanotransfection technology (TNT) delivery of CDH5 promoter-driven PLCγ2 open reading frame promoted the rescue of hindlimb ischemia in diabetic mice. Improvement of blood flow was also associated with higher abundance of VWF+/CD31+ and VWF+/SMA+ immunohistochemical staining. TNT-based gene delivery was not associated with tissue edema, a commonly noted complication associated with proangiogenic gene therapies. Taken together, our study demonstrates that TNT-mediated delivery of endothelial PLCγ2, as part of combination gene therapy, is effective in diabetic ischemic limb rescue.

Effect of topical application of platelet-rich plasma on chronic venous leg ulcerations

Wound products that reliably support healing of chronic leg ulcers remain a huge unmet need in clinical practice. Due to the lack of standardized comparable protocols and different systems for platelet-rich plasma (PRP) preparation, there is limited data on healing rates in chronic venous ulcers. In our case series with a total of seven chronic leg ulcers in four patients, we investigated the healing rates based on standardized digital photographs of chronic venous ulcers after application of topical PRP using a digital imaging software. In 5 out of 7 ulcers, the PRP-treated wound half showed faster healing as compared the control half of the wound. In this case series, PRP-treated sides of chronic venous leg ulcers showed a tendency for accelerated healing as compared to nontreated collateral wound side. Our data support the evaluation of topical PRP treatment in the management of chronic venous leg ulcers.

Quantifying the Effect of Topical Nitroglycerin on Random Pattern Flap Perfusion in a Rodent Model: An Application of the ViOptix Intra.Ox for Dynamic Flap Perfusion Assessment and Salvage

BACKGROUND

Near-infrared spectroscopy can detect changes in tissue oxygenation postoperatively that predict flap necrosis. The authors hypothesized that this technology can be applied along with topical nitroglycerin to measure an improvement in tissue oxygenation that correlates with tissue salvage.

METHODS

Dorsal, random pattern flaps measuring 10 × 3 cm were raised using Sprague-Dawley rats. Tissue oxygenation was measured after flap elevation in 10 locations using the ViOptix Intra.Ox. Animals were divided into three groups that received 30 mg of topical nitroglycerin daily, twice-daily, or not at all. Oxygenation measurements were repeated on postoperative day 1 and animals were euthanized on day 7 and evaluated for tissue necrosis.

RESULTS

Tissue necrosis was greatest in controls (51.3 mm) compared to daily (28.8 mm) and twice-daily nitroglycerin (18.8 mm; p = 0.035). Three flap perfusion zones were identified: healthy (proximal, 50 mm), necrotic (distal, 20 mm), and watershed. Immediate postoperative tissue oxygenation was highest in healthy tissue (57.2 percent) and decreased to 33.0 and 19.3 percent in the watershed and necrotic zones, respectively (p < 0.001). One day after treatment with nitroglycerin, oxygenation in the healthy zone did not increase significantly (mean difference, -1.5 percent). The watershed (17.8 percent; p < 0.001) and necrotic zones (16.3 percent; p <0.001) did exhibit significant improvements that were greater than those measured in control tissues (7.9 percent; both p < 0.001).

CONCLUSIONS

Serial perfusion assessment using the ViOptix Intra.Ox measured a significant improvement in flap oxygenation after treatment with topical nitroglycerin. Within the watershed area of the flap, this increase in tissue oxygenation was associated with the salvage of ischemic tissue.

Efficacy of Combined in-vivo Electroporation-Mediated Gene Transfer of VEGF, HGF, and IL-10 on Skin Flap Survival, Monitored by Label-Free Optical Imaging: A Feasibility Study

Preventing surgical flaps necrosis remains challenging. Laser Doppler imaging and ultrasound can monitor blood flow in flap regions, but they do not directly measure the cellular response to ischemia. The study aimed to investigate the efficacy of synergistic in-vivo electroporation-mediated gene transfer of interleukin 10 (IL-10) with either hepatocyte growth factor (HGF) or vascular endothelial growth factor (VEGF) on the survival of a modified McFarlane flap, and to evaluate the effect of the treatment on cell metabolism, using label-free fluorescence lifetime imaging. Fifteen male Wistar rats (290–320 g) were randomly divided in three groups: group-A (control group) underwent surgery and received no gene transfer. Group-B received electroporation mediated hIL-10 gene delivery 24 h before and VEGF gene delivery 24 h after surgery. Group-C received electroporation mediated hIL-10 gene delivery 24 h before and hHGF gene delivery 24 h after surgery. The animals were assessed clinically and histologically. In addition, label-free fluorescence lifetime imaging was performed on the flap. Synergistic electroporation mediated gene delivery significantly decreased flap necrosis (P = 0.0079) and increased mean vessel density (P = 0.0079) in treatment groups B and C compared to control group-A. NADH fluorescence lifetime analysis indicated an increase in oxidative phosphorylation in the epidermis of the group-B (P = 0.039) relative to controls. These findings suggested synergistic in-vivo electroporation-mediated gene transfer as a promising therapeutic approach to enhance viability and vascularity of skin flap. Furthermore, the study showed that combinational gene therapy promoted an increase in tissue perfusion and a relative increase in oxidative metabolism within the epithelium.

Ivermectin Increases Random-Pattern Skin Flap Survival in Rats: The Novel Role of GABAergic System

BACKGROUND

Ivermectin (IVM) was first used as an antiparasitic agent; however, the role of this drug evolved into a broad spectrum. Many mechanisms have been proposed, including interaction with the GABAergic system. Considering the presence of GABA receptor in the skin tissue and its role in ischemia-reperfusion I/R injury, we aimed to evaluate the effect of IVM through GABA receptors on random-pattern skin flap survival.

METHODS

Sixty Wistar male rats were used. Multiple doses of IVM (0.01, 0.05, 0.2, and 0.5 mg/kg) were injected intraperitoneally before the surgery. Baclofen (selective GABAB agonist) and bicuculline (selective GABAA antagonist) were administered in combination with IVM to assess the role of the GABAergic system. Histopathological evaluations, immunohistochemical staining, quantitative assessment of IL-1β and TNFα, and the expression of GABAA α1 subunit and GABAB R1 receptors were evaluated in the skin tissue.

RESULTS

IVM 0.05 mg/kg could significantly increase flap survival compared with the control group (P < 0.001). Subeffective dose of baclofen (0.1 mg/kg) had synergistic effect with the subeffective dose of IVM (0.01 mg/kg) (P < 0.001), whereas bicuculline 1 mg/kg reversed the effect of IVM (0.05 mg/kg) (P < 0.001). IVM 0.05 mg/kg could also decrease the IL-1β and TNFα levels and increase the expression of GABAA α1 subunit and GABAB R1 receptors in the flap tissue compared with the control group.

CONCLUSIONS

IVM could improve skin flap survival, probably mediated by the GABAergic pathway. Both GABAA and GABAB receptors are involved in this process. This finding may repurpose the use of old drug, "Ivermectin."

"Pingpong racket" flap model for evaluating flap survival

BACKGROUND

Random skin flap is widely used to repair tissue defects; however, it is often accompanied by ischemia and necrosis of the distal flap due to inferior axial vascularity. Even though different drugs, biomaterials, and stem cell therapies have been developed to improve the survival of random flap, evaluating the promotion of flap survival remains a big challenge. Based on successful clinical practice, we designed a "Pingpong racket" shape flap in the rat. Without the predetected blood vessels procedure, the "pingpong racket" flap provides a preferable option to evaluate the function of drugs and biomaterials in promoting flap survival.

MATERIALS AND METHODS

"Pingpong racket" dorsal flaps with different pedicle lengths were developed in the rats. The survival area was evaluated by digital photography and computer-assisted analysis. The quantitative survival area was considered a useful indicator for analyzing drugs' applicability in improving skin flap survival.

RESULTS

A new model with a pedicle width of 1 cm and a flap diameter of 3 cm, in which the length of the pedicle could be tuned, was established. No iliolumbar vessels passed through the pedicle. The necrosis ratio ( round ) of the flap was 29.88% in the 2 cm long pedicle, 74.69% in the 3 cm long pedicle, 95.52% in the 4 cm long pedicle, and in the 5 cm long pedicle; necrotic area could be found in both the round part and in the pedicle.

CONCLUSION

The new 3 cm long pedicle flap is suitable for evaluating the drugs for promoting skin flap survival. Rat dorsal "Pingpong racket" flap can be easily handled, thus avoiding blood vessels' detection. The flap could achieve comparable results to clinical and alleviate the negative influence of the flap's longitudinal contraction. Besides, it is intuitive and aesthetically pleasing.

Hyperoxygenated solution improves tissue viability in an avulsion injury flap model

BACKGROUND

Management of avulsion injuries remains a challenge due to necrosis. The aim of the present study is to create an experimental model reproducing an avulsion injury and investigate the effects of hyperoxygenated solution (HOS), a method of oxygen delivery that has been widely used in the therapy of ischaemia-hypoxia diseases, on avulsion injury flap survival in rats.

METHODS

Forty male rats were divided into four groups (n = 10 each). Dorsal random pattern flaps measuring 3 × 9 cm, including the panniculus carnosus, were elevated and run over by the skin avulsion model machine, and the flaps were then sutured into their original places. The sham+HOS and avulsion+HOS groups received intravenous HOS (20 ml/kg) each day for 7 days after the operation. The sham+saline and avulsion+saline groups received intravenous saline solution (20 ml/kg) each day for 7 days after the operation. Percutaneous O₂ pressure (TcpO₂) measurement_, serial examinations of skin flap blood perfusion, skin flap survival evaluation and histopathology were performed to assess the efficacy of HOS on avulsion injury.

RESULTS

Compared to the avulsion+saline groups, TcpO₂ was significantly higher in the avulsion+HOS groups at 15, 30 and 60 min after infusion (P < 0.05). The blood perfusion of flaps in the avulsion+HOS group was higher than in the avulsion+saline group (P < 0.05). The survival rate was higher in the avulsion+HOS group than in the avulsion+saline group (P < 0.05), and the histopathology assays supported the data.

CONCLUSION

We succeeded in developing an avulsion injury model and demonstrated that HOS could improve the survival of the avulsion injury flaps in rats by effectively increasing the local oxygen content and blood perfusion and ameliorating inflammatory damage.

FGF21 augments autophagy in random-pattern skin flaps via AMPK signaling pathways and improves tissue survival

Random-pattern skin flap is commonly used for surgical tissue reconstruction due to its ease and lack of axial vascular limitation. However, ischemic necrosis is a common complication, especially in distal parts of skin flaps. Previous studies have shown that FGF21 can promote angiogenesis and protect against ischemic cardiovascular disease, but little is known about the effect of FGF21 on flap survival. In this study, using a rat model of random skin flaps, we found that the expression of FGF21 is significantly increased after establishment skin flaps, suggesting that FGF21 may exert a pivotal effect on flap survival. We conducted experiments to elucidate the role of FGF21 in this model. Our results showed that FGF21 directly increased the survival area of skin flaps, blood flow intensity, and mean blood vessel density through enhancing angiogenesis, inhibiting apoptosis, and reducing oxidative stress. Our studies also revealed that FGF21 administration leads to an upregulation of autophagy, and the beneficial effects of FGF21 were reversed by 3-methyladenine (3MA), which is a well-known inhibitor of autophagy, suggesting that autophagy plays a central role in FGF21’s therapeutic benefit on skin flap survival. In our mechanistic investigation, we found that FGF21-induced autophagy enhancement is mediated by the dephosphorylation and nuclear translocation of TFEB; this effect was due to activation of AMPK-FoxO3a-SPK2-CARM1 and AMPK-mTOR signaling pathways. Together, our data provides novel evidence that FGF21 is a potent modulator of autophagy capable of significantly increasing random skin flap viability, and thus may serve as a promising therapy for clinical use.

Trehalose promotes the survival of random-pattern skin flaps by TFEB mediated autophagy enhancement

Random-pattern skin flaps are commonly used and valuable tools in reconstructive surgery, however, post-operative random skin flap necrosis remains a major and common complication. Previous studies have suggested that activating autophagy, a major pathway for degradation of intracellular waste, may improve flap survival. In this study, we investigated whether trehalose, a novel and potent autophagy activator, improves random skin flap viability. Our results demonstrated that trehalose significantly improves viability, augments blood flow, and decreases tissue edema. Furthermore, we found that trehalose leads to increased angiogenesis, decreased apoptosis, and reduced oxidative stress. Using immunohistochestry and western blot, we demonstrated that trehalose augments autophagy, and that inhibition of autophagy augmentation using 3MA significantly blunted the aforementioned benefits of trehalose therapy. Mechanistically, we showed that trehalose’s autophagy augmentation is mediated by activation and nuclear translocation of TFEB, which may be due to inhibition of Akt and activation of the AMPK-SKP2-CARM1 signaling pathway. Altogether, our results established that trehalose is a potent agent capable for significantly increasing random-pattern skin flap survival by augmenting autophagy and subsequently promoting angiogenesis, reducing oxidative stress, and inhibiting cell death.

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.

Enhanced Survival and Accelerated Perfusion of Skin Flap to Recipient Site Following Administration of Human α1-Antitrypsin in Murine Models

Objective: Skin flaps are routinely used in reconstructive surgery yet remain susceptible to ischemia and necrosis. Distant flaps require lengthy time to detach causing patient discomfort. Human α1-antitrypsin (hAAT) is a clinically available serum glycoprotein. hAAT was shown to support mature vessel formation and enhance tissue survival following ischemia-reperfusion injuries. The purpose of the presented study was to examine the effect of hAAT on skin flap survival and distant "tube" flap perfusion through its recipient site. Approach: Random-pattern skin flaps were performed on mice treated with clinical-grade hAAT using three unique routes of administration (transgenic, i.p. and s.c. infiltration); necrotic area and tissue perfusion were assessed. Blockade of vascular endothelial growth factor (VEGF) and nitric oxide synthase (NOS) were used to explore aspects of mechanism of action. A distant tube flap model was performed to examine time to perfusion. Results: hAAT-treated mice displayed approximately two-fold smaller necrotic flap areas versus controls across all hAAT administration routes. Flaps displayed greater perfusion as early as 3 days postsurgery (64.6% ± 4.0% vs. 43.7% ± 1.7% in controls; p = 0.007). hAAT-mediated flap survival was prominently NOS dependent, but only partially VEGF dependent. Finally, distant flaps treated with hAAT displayed significantly earlier perfusion versus controls (mean 9.6 ± 1.6 vs. 13.1 ± 1.0 days; p = 0.0005). Innovation: The established safety record of hAAT renders it an attractive candidate toward improving skin flap surgery outcomes, particularly during VEGF blockade. Conclusions: hAAT treatment enhances survival and accelerates perfusion of skin flaps in animal models in a NOS-dependent manner, partially circumventing VEGF blockade. Further mechanistic studies are required.

Basic concepts, current evidence, and future potential for gene therapy in managing cutaneous wounds

OBJECTIVE

Several studies have investigated the role of gene therapy in the healing process. The aim of this review is to explain the gene delivery systems in wound area.

RESULTS

Ninety-two studies were included and comprehensively overviewed. We described the importance of viral vectors such as adenoviruses, adeno-associated viruses, and retroviruses, and conventional non-viral vectors such as naked DNA injections, liposomes, gene gun, electroporation, and nanoparticles in achieving high-level expression of genes. Application of viral transfection, liposomal vectors, and electroporation were the main gene delivery systems. Genes encoding for growth factors or cytokines have been shown to result in a better wound closure in comparison to application of the synthetic growth factors. In addition, a combination of stem cell and gene therapy has been found an effective approach in regeneration of cutaneous wounds.

CONCLUSIONS

This article gives an overview of the methods and investigations applied on gene therapy in wound healing. However, clinical investigations need to be undertaken to gain a better understanding of gene delivery technologies and their roles in stimulating wound repair.

Therapeutic potential of pravastatin for random skin flaps necrosis: involvement of promoting angiogenesis and inhibiting apoptosis and oxidative stress

Background: Random skin flap is frequently used in plastic and reconstructive surgery, but its distal part often occurs ischemia and necrosis. Pravastatin (Prava) with bioactivities of pro-angiogenesis, anti-apoptosis and anti-oxidative stress, may be beneficial for flap survival. Materials and methods: A modified McFarlane flap model was performed in Sprague-Dawley rats. The animals were divided into the Control and Prava groups and treated as follows: the Prava group was injected intraperitoneally with 2 mg/kg Prava for consecutive 7 days, and the Control group received an equal volume of vehicle daily. On day 7, the necrosis skin flaps were observed, while visualization of blood flow below the tissue surface was performed by Laser Doppler blood flow imaging (LDBFI). Then animals were euthanized, and levels of angiogenesis, apoptosis and oxidative stress were analyzed. Results: Prava decreased necrosis and edema of skin flaps compared with the Control group, with more blood flow in the flap under LDBFI. Prava treatment increased the mean vessels density, elevated the expression levels of angiogenic proteins (matrix metallopeptidase 9, vascular endothelial growth factor, Cadherin5) and antioxidant proteins (superoxide dismutase 1 (SOD1), endothelial nitric oxide synthase, heme oxygenase), and decreased the expression of apoptotic factors (BAX, CYC, Caspase3). In addition, malondialdehyde content was reduced, and glutathione level and SOD activity were increased in the skin flaps after treatment with Prava. Conclusion: Prava promotes survival of random skin flap through induction of angiogenesis, and inhibition of apoptosis and oxidative stress.

Metformin Promotes the Survival of Random-Pattern Skin Flaps by Inducing Autophagy via the AMPK-mTOR-TFEB signaling pathway

Random-pattern skin flaps are widely used to close defects in reconstructive and plastic surgeries; however, they are vulnerable to necrosis, particularly in the distal portion of the flap. Here, we examined the effects of metformin on flap survival and the mechanisms underlying these effects. Following metformin treatment, the survival area, blood flow, and number of microvessels present in skin flaps were increased on postoperative day 7, whereas tissue edema was reduced. In addition, metformin promoted angiogenesis, inhibited apoptosis, relieved oxidative stress, and increased autophagy in areas of ischemia; these effects were reversed by autophagy inhibitors 3-methyladenine (3MA) or chloroquine (CQ). Either 3MA or CQ reversed the metformin-induced increase in flap viability. Moreover, metformin also activated the AMPK-mTOR-TFEB signaling pathway in ischemic areas. Inhibitions of AMPK via Compound C (CC) or AMPK shRNA adeno-associated virus (AAV) vector resulted in the downregulation of the AMPK-mTOR-TFEB signaling pathway and autophagy level in metformin-treated flaps. Taken together, our findings suggest that metformin improves the survival of random-pattern skin flaps by enhancing angiogenesis and suppressing apoptosis and oxidative stress. These effects result from increased autophagy mediated by activation of the AMPK-mTOR-TFEB signaling pathway.

Bioactive nanoparticle-based formulations increase survival area of perforator flaps in a rat model

BACKGROUND

Distal flap necrosis is a frequent complication of perforator flaps. Advances in nanotechnology offer exciting new therapeutic approaches. Anti-inflammatory and neo-angiogenic properties of certain metal oxides within the nanoparticles, including bioglass and ceria, may promote flap survival. Here, we explore the ability of various nanoparticle formulations to increase flap survival in a rat model.

MATERIALS AND METHODS

A 9 x 3 cm dorsal flap based on the posterior thigh perforator was raised in 32 Lewis rats. They were divided in 4 groups and treated with different nanoparticle suspensions: I-saline (control), II-Bioglass, III-Bioglass/ceria and IV-Zinc-doped strontium-substituted bioglass/ceria. On post-operative day 7, planimetry and laser Doppler analysis were performed to assess flap survival and various samples were collected to investigate angiogenesis, inflammation and toxicity.

RESULTS

All nanoparticle-treated groups showed a larger flap survival area as compared to the control group (69.9%), with groups IV (77,3%) and II (76%) achieving statistical significance. Blood flow measurements by laser Doppler analysis showed higher perfusion in the nanoparticle-treated flaps. Tissue analysis revealed higher number of blood vessels and increased VEGF expression in groups II and III. The cytokines CD31 and MCP-1 were decreased in groups II and IV.

CONCLUSIONS

Bioglass-based nanoparticles exert local anti-inflammatory and neo-angiogenic effects on the distal part of a perforator flap, increasing therefore its survival. Substitutions in the bioglass matrix and trace metal doping allow for further tuning of regenerative activity. These results showcase the potential utility of these nanoparticles in the clinical setting.

Nanomedicines and gene therapy for the delivery of growth factors to improve perfusion and oxygenation in wound healing

Oxygen plays a key role in wound healing, and hypoxia is a major cause of wound healing impairment; therefore, treatments to improve hemodynamics and increase wound oxygenation are of particular interest for the treatment of chronic wounds. This article describes the roles of oxygen and angiogenesis in wound healing as well as the tools used to evaluate tissue oxygenation and perfusion and then presents a review of nanomedicines and gene therapies designed to improve perfusion and oxygenation and accelerate wound healing.

The Delay Phenomenon: Is One Surgical Delay Technique Superior?

Background:

Surgical delay remains a common method for improving flap survival. However, the optimal surgical technique has not been determined. In this article, we compare flap perfusion, viable surface area, and flap contraction of 2 surgical delay techniques.

Methods:

Male Sprague-Dawley rats were divided into 3 groups. In the incisional surgical delay group (n = 9), a 9 × 3 cm dorsal flap was incised on 3 sides without undermining, leaving a cranial pedicle. In the bipedicle surgical delay group (BSD, n = 9), a 9 × 3 cm dorsal flap was incised laterally and undermined, leaving cranial and caudal pedicles. Control group (n = 16) animals did not undergo a delay procedure. Ten days following surgical delay, all flaps for all groups were raised, leaving a cranial pedicle. A silicone sheet separated the flap and the wound bed. On postoperative day (POD) 7, viable surface area was determined clinically. Contraction compared to POD 0 was measured with ImageJ software. Perfusion was measured with Laser Doppler Imaging. The Kruskal-Wallis with Dunn’s multiple comparisons test was performed for group comparisons.

Results:

BSD preserved significantly more viable surface area on POD 7 (13.7 ± 4.5 cm²) than Control (8.7 ± 1.8 cm²; P = 0.01). BSD also showed significantly less contraction (21.0% ± 13.5%) than Control (45.9% ± 19.7%; P = 0.0045). BSD and incisional surgical delay showed significantly increased perfusion compared with Control on POD 0 (P = 0.02 and 0.049, respectively), which persisted on POD 3. This trend resolved by POD 7.

Conclusion:

BSD showed improved early perfusion, increased viable surface area, and reduced contraction compared to control, suggesting that BSD is the superior flap design for preclinical modeling.

Hepatocyte growth factor (HGF) optimizes oral traumatic ulcer healing of mice by reducing inflammation

OBJECTIVE

To evaluate the influence of overexpression HGF on the healing of traumatic ulcer of oral mucosa of mice.

MATERIAL AND METHODS

Mice were divided into two groups: wild type C57BL6(WT) and HGF high expression transgenic (HGF-Tg) mice. Traumatic ulcer of all mice were made by number 15 scalpel blade. Mice were sacrificed after 5days and the inflammation score and expression of TNFα, IFNγ, c-Met, apoptosis (TUNEL) and 40 serum inflammation cytokines were estimated.

RESULTS

HGF-Tg mice presented a lower inflammation score (p=0.011), Serum TNFα expression in HGF-Tg ulcers is 1.3 times than WT ulcer and the difference is statistical significance (t test, p=0.003). Serum c-Met protein in HGF-Tg mice were significantly higher than WT mice (t test, p=0.004). No statistical difference was observed in the serum IFNγ between WT ulcer and HGF-Tg ulcer (t test, p=0.268). TNFα positive cytoplasm expression cells in connective tissue of HGF-Tg mice is significantly lower than that of WT group (t test, p=0.029). C-Met positive cytoplasm expression cells in both epithelium and connective tissue of HGF-Tg group is significantly higher than that of WT group (t test, p=0.040, p=0.000). Samples in HGF-Tg group showed a lower number of positive cells of epithelium TUNEL staining compared with that in the WT group (t test, p=0.035).

CONCLUSIONS

HGF exhibited anti-inflammatory potential in oral traumatic ulcer through the reduction of epithelial apoptosis, connective tissue TNFα expression and induction of c-Met expression.

Efficacy of In Vivo Electroporation-Mediated IL-10 Gene Delivery on Survival of Skin Flaps

Despite advances in understanding the underlying mechanisms of flap necrosis and improvement in surgical techniques, skin flap necrosis after reconstructive surgery remains a crucial issue. We investigated the efficacy of electroporation-mediated IL-10 gene transfer to random skin flap with an aim to accelerate wound healing and improve skin flap survival. Nine male Wistar rats (300-330 g) were divided in two groups (a) control group (n = 5), only surgery no gene transfer, and (b) experimental group, received electroporation-mediated IL-10 gene transfer 24 h before the surgery as prophylaxis (n = 4). Random skin flap (McFarlane) was performed in both groups. Planimetry, Laser Doppler imaging, and immunohistochemistry were used to evaluate the effect of IL-10 gene transfer between study groups at day 7. Electroporation-mediated IL-10 gene transfer decreased percentage of flap necrosis (p value = 0.0159) and increased cutaneous perfusion compared to the control group (p value = 0.0159). In addition, Spearman's rank correlation showed a significant negative correlation between percentage of flap necrosis and Laser Index (p value = 0.0083, r -0.83, respectively). Furthermore, significantly higher mean CD31⁺ vessel density was detected in the experimental group compared to the control group (p value = 0.0159). Additionally, semi-quantitative image analysis showed lower inflammatory cell count in experimental group compared to control group (p value = 0.0317). In vivo electroporation-mediated IL-10 gene transfer reduced necrosis, enhanced survival and vascularity in the ischemic skin flap.