Inhibition of c-Jun N-terminal kinase signaling suppresses skin flap apoptosis in a rat ischemia and/or reperfusion model

Systematic review of pathologic markers in skin ischemia with and without reperfusion injury in microsurgical reconstruction: Biomarker alterations precede histological structure changes

BACKGROUND

Ischemia and ischemia-reperfusion injury contribute to partial or complete flap necrosis. Traditionally, skin histology has been used to evaluate morphological and structural changes, however histology does not detect early changes. We hypothesize that morphological and structural skin changes in response to ischemia and IRI occur late, and modification of gene and protein expression are the earliest changes in ischemia and IRI.

METHODS

A systematic review was performed in accordance with PRISMA guidelines. Studies reporting skin histology or gene/protein expression changes following ischemia with or without reperfusion injury published between 2002 and 2022 were included. The primary outcomes were descriptive and semi-quantitative histological structural changes, leukocyte infiltration, edema, vessel density; secondary outcomes were quantitative gene and protein expression intensity (PCR and western blot). Model type, experimental intervention, ischemia method and duration, reperfusion duration, biopsy location and time point were collected.

RESULTS

One hundred and one articles were included. Hematoxylin and eosin (H&E) showed inflammatory infiltration in early responses (12-24 h), with structural modifications (3-14 days) and neovascularization (5-14 days) as delayed responses. Immunohistochemistry (IHC) identified angiogenesis (CD31, CD34), apoptosis (TUNEL, caspase-3, Bax/Bcl-2), and protein localization (NF-κB). Gene (PCR) and protein expression (western blot) detected inflammation and apoptosis; endoplasmic reticulum stress/oxidative stress and hypoxia; and neovascularization. The most common markers were TNF-α, IL-6 and IL-1β (inflammation), caspase-3 (apoptosis), VEGF (neovascularization), and HIF-1α (hypoxia).

CONCLUSION

There is no consensus or standard for reporting skin injury during ischemia and IRI. H&E histology is most frequently performed but is primarily descriptive and lacks sensitivity for early skin injury. Immunohistochemistry and gene/protein expression reveal immediate and quantitative cellular responses to skin ischemia and IRI. Future research is needed towards a universally-accepted skin injury scoring system.

Current Status of Experimental Animal Skin Flap Models: Ischemic Preconditioning and Molecular Factors

Skin flaps are necessary in plastic and reconstructive surgery for the removal of skin cancer, wounds, and ulcers. A skin flap is a portion of skin with its own blood supply that is partially separated from its original position and moved from one place to another. The use of skin flaps is often accompanied by cell necrosis or apoptosis due to ischemia-reperfusion (I/R) injury. Proinflammatory cytokines, such as nuclear factor kappa B (NF-κB), inhibitor of kappa B (IκB), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and oxygen free radicals are known causative agents of cell necrosis and apoptosis. To prevent I/R injury, many investigators have suggested the inhibition of proinflammatory cytokines, stem-cell therapies, and drug-based therapies. Ischemic preconditioning (IPC) is a strategy used to prevent I/R injury. IPC is an experimental technique that uses short-term repetition of occlusion and reperfusion to adapt the area to the loss of blood supply. IPC can prevent I/R injury by inhibiting proinflammatory cytokine activity. Various stem cell applications have been studied to facilitate flap survival and promote angiogenesis and vascularization in animal models. The possibility of constructing tissue engineered flaps has also been investigated. Although numerous animal studies have been published, clinical data with regard to IPC in flap reconstruction have never been reported. In this study, we present various experimental skin flap methods, IPC methods, and methods utilizing molecular factors associated with IPC.

Hydrogen-rich saline reduces tissue injury and improves skin flap survival on a rat hindlimb degloving injury model

BACKGROUND

Degloving injuries represent a challenge in plastic surgery. The aim of this study is to acknowledge the protective effects of hydrogen-rich saline (HRS) solution on a rat hindlimb degloved skin flap.

METHODS

Twenty-one Sprague-Dawley rats were divided into three groups (control, saline and HRS). Degloving injury model was established, and flaps were sutured back following 5 min of ischemia. The control group did not receive any treatment. The saline group received intraperitoneal physiological saline (10 ml/kg) and the HRS group received intraperitoneal HRS solution (10 ml/kg) postoperatively and daily for 5 days after the operation. Skin samples were obtained for histological, immunohistochemical and biochemical evaluations.

RESULTS

Inflammation was lower in the HRS compared with saline (p = 0.02) and control (p = 0.004) groups. Edema was lower in the HRS compared with saline (p = 0.02) and control (p = 0.001) groups. Malondialdehyde (MDA) level was lower in the HRS than the control group (p = 0.01). Total antioxidant level was higher in the HRS compared with saline (p = 0.009) and control (p = 0.03) groups. Total oxidant level was lower in the HRS than the control group (p = 0.02). Oxidative stress index was lower in the HRS compared with saline (p = 0.001) and control (p = 0.0001) groups`. Vascular proliferation was higher in the HRS compared with the control group (p = 0.01).

CONCLUSION

Repeated HRS injections after trauma increased the viability of skin flap in rat degloving injury model by decreasing local tissue injury, due to its antioxidant, anti-inflammatory and angiogenic effects.

Ameliorating Effects of β-Glucan on Epigastric Artery Island Flap Ischemia-Reperfusion Injury

BACKGROUND

Ischemia-reperfusion injury has been one of the culprits of tissue injury and flap loss after island flap transpositions. Thus, significant research has been undertaken to study how to prevent or decrease the spread of ischemia-reperfusion injury. Preventive effects of β-glucan on ischemia-reperfusion injury in the kidney, lung, and small intestine have previously been reported. In this study, we present the ameliorating effects of β-glucan on ischemia-reperfusion injury using the epigastric artery island-flap in rats.

MATERIALS AND METHODS

Thirty Wistar-Albino rats were equally divided into three groups: sham, experimental model, and treatment groups. In the sham group, an island flap was elevated and sutured back to the original position without any ischemia. In the experimental model group, the same-sized flap was elevated and sutured back with 8 h of ischemia and consequent 12 h of reperfusion. In the treatment group, 50 mg per kilogram β-glucan was administered to the rats using an orogastric tube for 10 d before the experiment. The same-sized flap is elevated and sutured back to its original position with 8 h of ischemia and 12 h of consequent reperfusion in the treatment group. Tissue biopsies were taken on the first day of the experimental surgery. Tissue neutrophil aggregation and vascular responses were evaluated by histological examinations. Tissue oxidant and antioxidant enzyme levels are evaluated biochemically after tissue homogenization. Topographic follow-up and evaluation of the flaps were maintained, and photographs were taken on the first and seventh day of the experimental surgery.

RESULTS

Topographic flap survival was significantly better in the β-glucan administered group. The neutrophil number, malondialdehyde, and myeloperoxidase levels were significantly lower while glutathione peroxidase and superoxide dismutase levels were significantly higher in the β-glucan administered group respective to the experimental model group.

CONCLUSIONS

Based on the results of our study, we can conclude that β-glucan is protective against ischemia-reperfusion injury. Our study presents the first experimental evidence of such an effect on skin island flaps.

JNK inhibition alleviates oxidative DNA damage, germ cell apoptosis, and mitochondrial dysfunction in testicular ischemia reperfusion injury

The aim of this study is to determine whether the c-Jun N-terminal kinase (JNK) signaling is a regulator of oxidative DNA damage, germ cell apoptosis (GCA), and mitochondrial dysfunction during testicular ischemia reperfusion injury (tIRI) using the JNK inhibitor SP600125. Male Sprague Dawley rats (n = 36) were equally divided into three groups: sham, tIRI only, and tIRI + SP600125 (15 mg/kg). Testicular ischemia was induced for 1 h followed by 4 h of reperfusion prior to animal sacrifice. Spermatogenesis was evaluated by light microscopy, while expression of oxidative stress and GCA-related mRNAs and proteins were evaluated by real-time polymerase chain reaction and colorimetric assays, respectively. Expressions of JNK, p53, and survivin were detected by immunofluorescence (IF) staining. Indicators of mitochondrial dysfunction were examined by western blot analysis and colorimetric assay. In comparison to sham, the tIRI testes showed a significant increase in lipid and protein oxidation products. Oxidative DNA damage was reflected by a significant increase in the number of DNA strand breaks, increased concentration of 8-OHdG, and elevated poly (ADP-ribose) polymerase activity. Spermatogenic damage was associated with the activation of caspase 3 and elevated Bax to Bcl2 ratio. This was also accompanied by a significantly heightened IF expression of the phosphorylated forms of JNK and p53 paralled with the suppression of survivin. Mitochondrial dysfunction was reflected by NAD+ depletion, overexpression of uncoupling protein 2, and increased level of cytochrome c. Such tIRI-induced modulations were all attenuated by SP600125 treatment prior to reperfusion. In conclusion, JNK signaling regulates oxidative DNA damage, GCA, and mitochondrial dysfunction through activation of p53 and suppression of survivin during tIRI.

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.

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.