Protective effects of dexmedetomidine on the survival of random flaps

Emodin activates autophagy to suppress oxidative stress and pyroptosis via mTOR-ULK1 signaling pathway and promotes multi-territory perforator flap survival

BACKGROUND

Multi-territory perforator flap reconstruction has been proven effective in treating large skin and soft tissue defects in clinical settings. However, in view of that the multi-territory perforator flap is prone to partial postoperative necrosis, increasing its survival is the key to the success of reconstruction. In this study, we aimed to clarify the effect of emodin on multi-territory perforator flap survival.

METHODS

Flap survival was assessed by viability area analysis, infrared laser imaging detector, HE staining, immunohistochemistry, and angiography. Western blotting, immunofluorescence assays, and real-time fluorescent quantitative PCR were performed to detect the indicators of oxidative stress, pyroptosis and autophagy.

RESULTS

After emodin treatment, the multi-territory perforator flap showed a significantly increased survival rate, which was shown to be closely related to the inhibition of oxidative stress and pyroptosis and enhanced autophagy. Meanwhile, the use of autophagy inhibitor 3 MA was found to reverse the inhibitory effects of emodin on oxidative stress and pyroptosis and weaken the improving effect of emodin on flap survival, suggesting that autophagy plays a critical role in emodin-treated flaps. Interestingly, our mechanistic investigations revealed that the positive effect of emodin on multi-territory perforator flap was attributed to the mTOR-ULK1 signaling pathway activation.

CONCLUSIONS

Emodin can inhibit oxidative stress and pyroptosis by activating autophagy via the mTOR-ULK1 pathway, thereby improving the multi-territory perforator flap survival.

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.

Saxagliptin promotes random skin flap survival

BACKGROUND

Flap necrosis is a common issue encountered in clinical flap transplantation surgery. Here, we assessed the effects of saxagliptin, a dipeptidyl peptidase-4 inhibitor, on flap survival and explored the underlying mechanisms.

METHODS

A dorsal McFarlane flap model was established in 36 rats, which were randomly divided into a high-dose saxagliptin (HS) group (saxagliptin, 30 mg/kg/day, n = 12), low-dose saxagliptin (LS) group (saxagliptin, 10 mg/kg/day, n = 12), and control group (n = 12). On day 7, flap survival was examined by eye in six rats from each group, along with determination of blood perfusion by laser Doppler flowmetry and angiogenesis by angiography. The remaining rats were sacrificed for harvesting of flap tissue. The status of the flap tissue was examined histopathologically by staining with hematoxylin and eosin (H&E). Oxidative stress was evaluated by determination of superoxide dismutase (SOD) activity and malonaldehyde (MDA) content. Gasdermin D (GSDMD), vascular endothelial growth factor (VEGF), tumor necrosis factor-α (TNF-α), NOD-like receptor pyrin domain containing 3 (NLRP3), interleukin (IL)-6, IL-18, Toll-like receptor 4 (TLR4), IL-1β, caspase-1, and nuclear factor-κB (NF-κB) expression were detected by immunohistochemical analysis.

RESULTS

The experimental group exhibited a larger area of flap survival, with more blood perfusion and neovascularization and better histopathological status than the control group. The degree of oxidative stress and the levels of NF-κB, TLR4, proinflammatory cytokines, and pyroptosis-associated protein were decreased in the experimental group, while the VEGF level was increased in a saxagliptin dose-dependent manner.

CONCLUSION

Saxagliptin promotes random skin 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.

Protein kinase D1 promotes the survival of random-pattern skin flaps in rats

BACKGROUND

In reconstructive surgery, random skin flaps are commonly used tools to cover skin defects, however, their applicability and size are limited by post-operative complications such as marginal ischemia-reperfusion injury and flap necrosis. Protein kinase D1 (PKD1), a calcium/calmodulin-dependent serine/threonine kinase, is known to induce angiogenesis and has been shown to mitigate ischemia in cardiovascular diseases. However, the role of PKD1 has not been investigated in skin flaps.

METHOD

Seventy-five male Sprague-Dawley rats with skin flaps were randomly divided into three groups: control, PKD1, and CID755673. Seven days following surgery, we assessed the general view and survival rate of the flap using histological analysis. Laser Doppler and lead oxide/gelatin angiography were used to evaluate microcirculation blood flow. Histopathological changes, neovascularization and microvascular density (MVD). were examined and calculated using microscopy after H&E staining. Protein expression levels were determined using immunoblotting and immunohistochemistry techniques.

RESULT

PKD1 significantly improved flap survival by upregulating angiogenic factors VEGF and cadherin5 and increasing antioxidant enzymes SOD, eNOS, and HO1, as well as reducing caspase 3, cytochrome c, and Bax expression, and attenuating IL-1β, IL-6, and TNF-α. In the PKD1 group, PKD1 increased neovascularization, and blood flow and flap survival areas were larger as compared to the control and CID755673 groups.

CONCLUSION

These findings show that PKD1 accelerates angiogenesis, reduces oxidative stress, and impedes apoptosis and inflammation, thus resulting in improved flap survival. Our observations indicated that PKD1 could be a therapeutic target for flap failure treatment.

Fibroblast Growth Factor 9 Inhibited Apoptosis in Random Flap via the ERK1/2-Nrf2 Pathway to Improve Tissue Survival

BACKGROUND

The application of random pattern skin flaps is limited in plastic surgery reconstruction due to necrosis. Fibroblast growth factor 9 (FGF9) was reported to exert a protective effect against myocardial damage and cerebral ischemia injury, but the impact of FGF9 in random flap survival is still unclear. In this study, we used a mouse model of random flaps to verify that FGF9 can directly increase flap survival area and blood flow intensity by promoting angiogenesis.

MATERIALS AND METHODS

In total, 84 male C57BL/6 mice weighing between 22 and 25 g were randomly divided into three groups (n = 28 each group). After skin flap operation, one group served as a control, a treatment group received FGF9, and a treatment group received FGF9+U0126. All flap samples were incised on postoperative day 7.

RESULTS

Our results showed that flap survival was significantly increased in the FGF9 group compared with that in the control group. This protective function was restrained by U0126. The results of histopathology, laser Doppler, and fluorescent staining all showed significant increases in capillary count, collagen deposition, and angiogenesis. FGF9 also significantly increased the expression of antioxidant stress proteins SOD1, eNOS, HO-1, vascular marker proteins CD31, VE cadherin, and pericyte marker protein PDGFRβ. Western blot showed that the phosphorylation degree of ERK1/2 increased after FGF9 treatment, and the expression of Nrf2, a downstream factor, was u-regulated. Western blot and immunofluorescence results of apoptosis-related proteins cleaved caspase-3, BAX, and Bcl2 showed that FGF9 inhibited apoptosis. ERK inhibitor U01926 reduced the beneficial effects of FGF9 on skin flap survival, including promoting angiogenesis, and showing antiapoptosis and antioxidative stress activities.

CONCLUSIONS

Exogenous FGF9 stimulates angiogenesis of random flap and survival of tissue. the impact of FGF9 is closely linked to the prevention of oxidative stress mediated by ERK1/2-Nrf2. In the function of FGF9 in promoting effective angiogenesis, there may be a close interaction in the FGF9-FGFR-PDGFR-ERK-VE cadherin pathway. In particular, PDGFR and VE cadherin may interact.

Oxidative stress-induced endothelial cells-derived exosomes accelerate skin flap survival through Lnc NEAT1-mediated promotion of endothelial progenitor cell function

Background

Flap transplantation is commonly used in reconstructive surgery. A prerequisite for skin flap survival is sufficient blood supply. However, such approaches remain unclear. This study aimed to explore the underlying mechanisms of exosomes derived from human umbilical vascular endothelial cells (HUVECs) exposed to oxidative stress on endothelial progenitor cells (EPCs) and their subsequent influence on the survival of skin flaps.

Methods

HUVECs were treated with various concentrations of H₂O₂ to establish an oxidative stress model. To investigate the effects of H₂O₂-HUVEC-Exos and HUVEC-Exos, Cell Counting Kit-8, tube formation, invasion assays, and quantitative real-time polymerase chain reaction (qRT-PCR) were performed in EPCs. Microarray analysis was used to reveal the differentially expressed long non-coding RNAs (lncRNAs) in the H₂O₂-HUVEC-Exos and HUVEC-Exos. In addition, gene silencing and western blotting were employed to determine the mechanism behind lncRNA nuclear enrichment enriched transcript 1 (Lnc NEAT1) in EPCs. Further, a rat skin flap model was used to determine the role of the exosomes in skin flap survival in vivo.

Results

HUVECs were stimulated with 100 μmol/L H₂O₂ for 12 h to establish an oxidative stress model. H₂O₂-HUVEC-Exos promoted the proliferation, tube formation, and invasion of EPCs and remarkably increased skin flap survival compared to the HUVEC-Exos and control groups. Sequencing of exosome RNAs revealed that the Lnc NEAT1 level was dramatically increased in the H₂O₂-HUVEC-Exos, leading to activation of the Wnt/β-catenin signaling pathway. Comparatively, knockdown of Lnc NEAT1 in HUVEC-Exos and H₂O₂-HUVEC-Exos significantly inhibits the angiogenic capacity of EPCs, reduced the survival area of skin flap and downregulated the expression levels of Wnt/β-catenin signaling pathway proteins, whereas Wnt agonist partly reversed the negative effect of NEAT1 downregulation on EPCs through the Wnt/β-catenin signaling pathway.

Conclusions

Exosomes derived from HUVECs stimulated by oxidative stress significantly promoted the pro-angiogenic ability of EPCs through the Wnt/β-catenin signaling pathway mediated by Lnc NEAT1 and hence enhanced random flap survival in vivo. Therefore, the application of H₂O₂-HUVEC-Exos may serve as an alternative therapy for improving random skin flap survival.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03013-9.

Rivastigmine Regulates the HIF-1α/VEGF Signaling Pathway to Induce Angiogenesis and Improves the Survival of Random Flaps in Rats

Random skin flaps are frequently used to repair skin damage. However, the ischemic and hypoxic necrosis limits their wider application. Rivastigmine, a carbamate cholinesterase inhibitor (ChEI), has also been shown to reduce ischemia–reperfusion injury (IRI) and inflammation. This study was performed to examine the effect of rivastigmine on flap survival. Sixty male Sprague–Dawley rats with a modified McFarland flap were randomly divided into three groups: control group, 1 ml of solvent (10% DMSO + 90% corn oil); low-dose rivastigmine group (Riv-L), 1.0 mg/kg; and high-dose rivastigmine group (Riv-H), 2.0 mg/kg. All rats were treated once a day. On day 7, the skin flap survival area was measured. After staining with hematoxylin and eosin (H&E), the pathological changes and microvessel density (MVD) were examined. The expression of inflammatory factors IL-1β and IL-18, CD34, hypoxia-inducible factor-1α (HIF-1α), and vascular endothelial growth factor (VEGF) was examined by immunohistochemical staining. The malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were examined to determine the degree of oxidative stress. Lead oxide/gelatin angiography showed neovascularization and laser Doppler blood flowmetry showed the blood filling volume. Rivastigmine significantly increased the flap survival area and improved neovascularization. CD34, VEGF, and HIF-1α expression were increased, These changes were more pronounced in the Riv-H group. Treatment with rivastigmine reduced the level of MDA, improved SOD activity, and reduced expression of IL-1β and IL-18. Our results indicate that Rivastigmine can increase angiogenesis and significantly improve flap survival.

Notoginseng Triterpenes Inhibited Autophagy in Random Flaps via the Beclin-1/VPS34/LC3 Signaling Pathway to Improve Tissue Survival

Random flaps are widely used in tissue reconstruction, attributed to the lack of vascular axial limitation. Nevertheless, the distal end of the flap is prone to necrosis due to the lack of blood supply. Notoginseng triterpenes (NTs) are the active components extracted from Panax notoginseng, reducing oxygen consumption and improving the body’s tolerance to hypoxia. However, their role in random flap survival has not been elucidated. In this study, we used a mouse random skin flap model to verify that NT can promote cell proliferation and migration and that increasing blood perfusion can effectively improve the survival area of a skin flap. Our study also showed that the autophagy of random flaps after NT treatment was activated through the Beclin-1/VPS34/LC3 signaling pathway, and the therapeutic effect of NT significantly decreased after VPS34 IN inhibited autophagy. In conclusion, we have demonstrated that NT can significantly improve the survival rate of random flaps through the Beclin-1/VPS34/LC3 signaling pathway, suggesting that it might be a promising clinical treatment option.

Effects of Apigenin Treatment on Random Skin Flap Survival in Rats

Random skin flaps are often used in plastic surgery, but the complications of marginal flap ischemia and necrosis often limit their wider clinical application. Apigenin (Api) is a flavonoid found in various fruits and vegetables. Api has been shown to promote angiogenesis, as well as reduce oxidative stress, membrane damage, and inflammation. In this study, we assessed the effects of Api treatment on random skin flap survival. Dorsal McFarlane skin flaps were transplanted into rats, which were randomly divided into three groups: control (normal saline), low-dose Api (20 mg/kg), and high-dose Api (50 mg/kg). Seven days after the surgery, the activity of superoxide dismutase (SOD) and the level of malondialdehyde (MDA) were measured. Histological analyses were performed to determine flap survival and tissue edema. H&E staining was performed to assess the histopathological changes in skin flaps, and the levels of microvascular density (MVD) were determined. Laser doppler flowmetry was used to assess microcirculation blood flow. Flap angiography was performed by injection of lead oxide/gelatin. The expression levels of vascular endothelial growth factor (VEGF), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interlukin-1β (IL-lβ) were evaluated by immunohistochemistry. Rats in the high-dose Api group exhibited higher average flap survival area, microcirculatory flow, increased SOD activity, and higher VEGF expression levels compared with the other two groups. Furthermore, the levels of MDA and pro-inflammatory cytokines were significantly decreased in rats treated with high-dose Api. Our findings suggest the potential usefulness of Api in preventing skin flap tissue necrosis.