The Effect of Postconditioning on the Muscle Flap Survival After Ischemia-Reperfusion Injury in Rats

Propionyl-l-carnitine mitigates ischemia-reperfusion injury in rat epigastric island flaps

Background

Ischemia-reperfusion injury presents a substantial concern in various medical scenarios, notably in reconstructive surgery involving tissue flaps. Despite reports on the protective benefits of Propionyl-l-carnitine against ischemia-reperfusion injury, a thorough assessment of its efficacy in epigastric island flap models is currently lacking.

Methods

Sixteen male Sprague-Dawley rats underwent epigastric island flap surgery and were divided into two groups: a Propionyl-l-carnitine group that received intraperitoneal Propionyl-l-carnitine prior to ischemia induction and a sham group that received saline treatment. A comprehensive evaluation was performed including macroscopic, biochemical and histological assessments encompassing measurements of flap survival areas, lipid peroxidation (malondialdehyde), glutathione, myeloperoxidase, nitric oxide and peripheral neutrophil counts.

Results

The Propionyl-l-carnitine group demonstrated significantly increased flap survival areas when compared to the sham group. Administration of Propionyl-l-carnitine led to reduced malondialdehyde levels and elevated glutathione levels indicating a reduction in oxidative stress. Furthermore, the Propionyl-l-carnitine group exhibited lower myeloperoxidase levels, higher nitric oxide levels and reduced peripheral neutrophil counts, suggesting a decrease in the inflammatory response. Histopathological analysis revealed decreased levels of inflammation, necrosis, polymorphonuclear leukocyte infiltration and edema in the Propionyl-l-carnitine group. Additionally, vascularity was enhanced in the Propionyl-l-carnitine group.

Conclusion

This study provides compelling evidence that Propionyl-l-carnitine administration effectively mitigates the deleterious effects of ischemia-reperfusion injury in epigastric island flaps. This is substantiated by the improved flap survival, diminished oxidative stress and inflammation, as well as the enhanced vascularity observed. Propionyl-l-carnitine emerges as a promising therapeutic intervention to enhance tissue flap survival in reconstructive surgery, warranting further exploration through larger-scale investigations.

Protective effects of ischemic postconditioning on skeletal muscle following crush syndrome in the rat

Purpose

To investigate the effect of ischemic postconditioning (IPostC) on skeletal muscle and its optimal protocol.

Methods

This article is about an animal study of rat model of crush syndrome. Sixty rats were randomized into nine different IPostC intervention groups and a control group. The anesthetized rats were subjected to unilateral hindlimb 3-kg compression with a compression device for 6 h, followed by nine different IPostC intervention protocols.

Results

Serum levels of creatine kinase (CK) at 3 h post-crush became 2.3-3.9 times among all 10 groups after crush. At 72 h post-crush, serum CK level was reduced to 0.28-0.53 time in all intervention groups. The creatinine (CREA) level in the control group was elevated to 3.11 times at 3 h post-crush and reduced to1.77 time at 72 h post-crush. The potassium (K+) level in the control group was elevated to 1.65 and 1.41 time at 3 and 72 h post-crush, respectively.

Conclusions

Our IPostC intervention protocols can effectively protect rats from crush-induced elevation of serum CK, CREA, and K+ levels. The timing of IPostC intervention should be as early as possible, to ensure the protective effect.

Pharmacological Activities and Mechanisms of Hirudin and Its Derivatives - A Review

Hirudin, an acidic polypeptide secreted by the salivary glands of Hirudo medicinalis (also known as "Shuizhi" in traditional Chinese medicine), is the strongest natural specific inhibitor of thrombin found so far. Hirudin has been demonstrated to possess potent anti-thrombotic effect in previous studies. Recently, increasing researches have focused on the anti-thrombotic activity of the derivatives of hirudin, mainly because these derivatives have stronger antithrombotic activity and lower bleeding risk. Additionally, various bioactivities of hirudin have been reported as well, including wound repair effect, anti-fibrosis effect, effect on diabetic complications, anti-tumor effect, anti-hyperuricemia effect, effect on cerebral hemorrhage, and others. Therefore, by collecting and summarizing publications from the recent two decades, the pharmacological activities, pharmacokinetics, novel preparations and derivatives, as well as toxicity of hirudin were systematically reviewed in this paper. In addition, the clinical application, the underlying mechanisms of pharmacological effects, the dose-effect relationship, and the development potential in new drug research of hirudin were discussed on the purpose of providing new ideas for application of hirudin in treating related diseases.

Saphenous Artery Perforator Flaps in Minipigs: Anatomical Study and a New Experimental Model

This study describes the anatomy of the saphenous artery (SA) perforators in minipigs and the development of a new animal model. First, the anatomic characteristics of the SA and perforators in minipigs were examined after latex-lead oxide perfusion. Subsequently, the right hind limbs of 10 minipigs were used to generate capillary perforator flaps (group A; utilizing the SA and 5.5 cm of deep fascia above the knee), while all perforators of the left hind limbs were reserved (group B). Four additional minipigs were used to evaluate SA perforator flaps with capillary perforators plus sarcolemma and a small amount of muscle (group C). Preoperative and postoperative CTA of both hind limbs confirmed that all perforators were ligated in groups A and C. The average length of the SA was 14.86 ± 0.76 mm. The diameters of the SA at initiation, the medial tibial condyle, and the medial malleolus were 1.73 ± 0.15 mm, 1.50 ± 0.12 mm, and 1.30 ± 0.13 mm, respectively. There were 7.09 ± 1.16 perforators per hind limb, with an average diameter of 0.40 ± 0.13 mm (range, 0.10-0.78 mm), and the majority (96.2%) had a diameter >0.2 mm. The survival rates of the flaps in groups A, B, and C were 32 ± 39%, 100%, and 60.2 ± 17%, respectively. The position of the SA in minipigs is constant, its diameter is relatively large, and it has many perforators, allowing it to be used as a reliable model of perforator flaps, including capillary perforator flaps.

The effect of hirudin on antagonisting thrombin induced apoptosis of human microvascular endothelial cells1

Purpose

To investigate whether hirudin exerts its antithrombin action to decrease the ratio of Human Microvascular Endothelial Cells (HMVECs) apoptosis.

Methods

Human microvascular endothelial cells (HMVECs) cultured in the third and fifth generations were used. HMVECs were divided into normal group, thrombin group (T group), natrual hirudin group (H group), thrombin + natrual hirudin group (T + H group), AG490 group, thrombin + AG490 group (T + AG490 group), natrual hirudin + AG490 group (H + AG490 group), thrombin + natural hirudin + AG490 (T + H + AG490 group).Apart from the normal group, the other groups were exposed to the relevant drugs for 24 hours.HMVEC apoptosis was assessed by flow cytometric and double Immunofluorescence of phosphorylation of JAK (P-JAK2) and TUNEL assay.

Results

Compared with the normal group, in thrombin group the HMVECs apoptosis rate were significantly increased (P<0.05).The results indicated that the index of apoptosis and the apoptosis rate were improved in cultures treated by natural hirudin (T + H group), relative to cultures with thrombin only (T group). We found that the index of apoptosis and the apoptosis rate in the AG490 + thrombin group were higher than that in the hirudin + thrombin group (P<0.05). Double Immunofluorescence of p-JAK2 and TUNEL assays showed that cells were double positive for P-JAK2 uptake and TUNEL detection liquid binding.

Conclusion

The natural hirudin and JAK2/STATs signal inhibitor AG490 could block the effects of thrombin. Natural hirudin could attenuate HMVECs apoptosis via antagonizing thrombin and it is suggested that this effect may occur by blocking the JAK2/STATs signaling pathway and this signaling pathways appears to be not the only pathway.

SIRT1 activation by pterostilbene attenuates the skeletal muscle oxidative stress injury and mitochondrial dysfunction induced by ischemia reperfusion injury

Ischemia reperfusion (IR) injury is harmful to skeletal muscles and causes mitochondrial oxidative stress. Pterostilbene (PTE), an analogue of resveratrol, has organic protective effects against oxidative stress. However, no studies have investigated whether PTE can protect against IR-related skeletal muscular injury. In this study, we sought to evaluate the protective effect of PTE against IR-related skeletal muscle injury and to determine the mechanisms in this process. Male Sprague-Dawley rats were pretreated with PTE for a week and then underwent limb IR surgery. The IR injury induced segmental necrosis and apoptosis, myofilament disintegration, thicker interstitial spaces, and inflammatory cell infiltration. Furthermore, mitochondrial respiratory chain activity in the muscular tissue was inhibited, methane dicarboxylic aldehyde concentration and myeloperoxidase activity were up-regulated, and superoxide dismutase was down-regulated after IR. However, these effects were significantly inhibited by PTE in a dose-dependent manner. The mechanism underlying IR injury is attributed to the down-regulation of silent information regulator 1 (SIRT1)-FOXO1/p53 pathway and the increase of the Bax/Bcl2 ratio, Cleaved poly ADP-ribose polymerase 1, Cleaved Caspase 3, which can be reversed with PTE. Furthermore, EX527, an SIRT1 inhibitor, counteracted the protective effects of PTE on IR-related muscle injury. In conclusion, PTE has protective properties against IR injury of the skeletal muscles. The mechanism of this protective effect depends on the activation of the SIRT1-FOXO1/p53 signaling pathway and the decrease of the apoptotic ratio in skeletal muscle cells.

The rat groin flap model redesigned for evaluating treatment effects on ischemia-reperfusion injury

BACKGROUND

Although there is a wide application of the rat extended groin flap (epigastric skin flap) in studying different clinical issues, inconsistency arises between studies because many parameters of the extended groin flap have not been well defined.

MATERIALS AND METHODS

The flap is based on the superficial inferior epigastric vessels, which give into a lateral and a medial branch distally. Herein, three steps were taken to redesign this model: First, the ventral vascular anatomy was visualized through an imaging study to determine the flap borders. Second, different ischemic durations were induced on five groups of Lewis rats (n = 5 in each group) by clamping the femoral artery; group 1 (sham group) received no ischemic insult after elevation and was immediately repositioned, and groups 2, 3, 4, and 5 received 12-, 14-, 16-, and 18-hour ischemia, respectively. Percentage of necrosis area was measured after 5 days. Third, the redesigned groin flap model was tested with the ischemic postconditioning for validation.

RESULTS

The flap borders were determined such that both branches of the superficial inferior epigastric vessels were always included to ensure blood supply consistency. As the 14-hour ischemia induced the least variation in necrotic area on rats, it was chosen for further studies. In addition, ischemic postconditioning after 14-hr ischemia resulted in significant reduction of necrosis in this model.

CONCLUSIONS

We have redesigned the extended groin flap model with better-defined borders and consistent vascular anatomy. The ischemia duration was calibrated with predictable necrosis pattern and the practicality was demonstrated. With this model, precise assessment of treatment efficacies on ischemia-reperfusion injury could be achieved in future studies.

Remote Ischemic Conditioning Improves Blood Flow and Oxygen Saturation in Pedicled and Free Surgical Flaps

BACKGROUND

Surgical flaps have become safe and reliable reconstructive tools, but total flap loss rates as high as 25 percent and partial flap loss rates as high as 36 percent have been reported due to insufficient perfusion. Therefore, a reliable, noninvasive, and effective way to improve the microcirculation of surgical flaps is desirable. The aim of this study was to assess the effect of remote ischemic conditioning on the microcirculation of pedicled and free surgical flaps.

METHODS

Thirty patients undergoing free (n = 20) and pedicled (n = 10) tissue transfer were included in this study. Remote ischemic conditioning was applied on the upper extremity for three cycles on postoperative days 1, 5, and 12. Blood flow, tissue oxygen saturation, and relative hemoglobin content were measured by means of a combination of laser Doppler and spectroscopy (O2C device) in the flap and the surrounding tissue. The relative increase compared with baseline measurements was assessed.

RESULTS

Blood flow increased significantly in controls on all 3 postoperative days (p < 0.05 for all). In free flaps, tissue oxygen saturation improved significantly on postoperative days 1 and 12 and blood flow improved significantly on postoperative days 5 and 12 (p < 0.05). In pedicled flaps, blood flow and tissue oxygen saturation increased on postoperative day12, but not significantly.

CONCLUSIONS

Remote ischemic conditioning is a safe, inexpensive, fast, and reliable method to improve the microcirculation of surgical flaps. Further research is warranted to see whether such an improvement translates into improved flap survival, but it is likely.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Edaravone enhances the viability of ischemia/reperfusion flaps

The purpose of the experiment was to study the efficacy of edaravone in enhancing flap viability after ischemia/reperfusion (IR) and its mechanism. Forty-eight adult male SD rats were randomly divided into 3 groups: control group (n=16), IR group (n=16), and edaravone-treated IR group (n=16). An island flap at left lower abdomen (6.0 cm×3.0 cm in size), fed by the superficial epigastric artery and vein, was created in each rat of all the three groups. The arterial blood flow of flaps in IR group and edaravone-treated IR group was blocked for 10 h, and then the blood perfusion was restored. From 15 min before reperfusion, rats in the edaravone-treated IR group were intraperitoneally injected with edaravone (10 mg/kg), once every 12 h, for 3 days. Rats in the IR group and control group were intraperitoneally injected with saline, with the same method and frequency as the rats in the edaravone-treated IR group. In IR group and edaravone-treated IR group, samples of flaps were harvested after reperfusion of the flaps for 24 h. In the control group, samples of flaps were harvested 34 h after creation of the flaps. The content of malondialdehyde (MDA) and activity of superoxide dismutase (SOD) were determined, and changes in organizational structure and infiltration of inflammatory cells were observed by hematoxylin-eosin (HE) staining, apoptotic cells of vascular wall were marked by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, and the apoptotic rate of cells in vascular wall was calculated. The ultrastructural changes of vascular endothelial cells were observed by transmission electron microscopy (TEM). Seven days after the operation, we calculated the flap viability of each group, and marked vessels of flaps by immunohistochemical staining for calculating the average number of subcutaneous vessels. The results showed that the content of MDA, the number of multicore inflammatory cells and apoptotic rate of cells in vascular wall in the edaravone-treated IR group were significantly lower than those in the IR group. The activity of SOD, flap viability and average number of subcutaneous vessels in the edaravone-treated IR group were significantly higher than those in the IR group. All the differences were statistically significant. The ultrastructure injury of vascular endothelial cells in the edaravone-treated IR group was slighter than that in IR group. It was concluded that edaravone can significantly enhance IR flap viability and protect flap vessels, which is related to scavenging oxygen free radicals, reducing the consumption of SOD, reducing the extent of lipid peroxidation and inflammation, and protecting functional structure of vessels in the early stages of reperfusion.

Combination of ischemic preconditioning and postconditioning can minimise skin flap loss: experimental study

OBJECTIVES

Ischaemic preconditioning and postconditioning, which consist of one or a series of short ischaemic events. This study aimed to determine the efficiency of post-conditioning a flap in the minimisation of flap loss after a preconditioned skin flap.

METHODS

The rats were divided into five groups: sham group, control group, pre-con group, post-con group, and pre + post-con group. On postoperative days 3 and 7, the entire flaps along with the margins of necrosis were traced onto transparent sheets. The areas of intact skin and tissue were recorded.

RESULTS

The flap necrosis area and percentage of necrosis were calculated for each animal. The necrotic area percentage of the control group was found to be significantly higher than those of the other groups on Days 3 and 7 (p = 0.01 and p = 0.03, respectively). The necrotic area percentage of the pre-con group was significantly higher than the pre + post-con group on Day 7 (p = 0.01). VEGFR-3 expression was observed at a rate of more than 50% in the post-con group. The presence of a protective effect in the late period was separately investigated by immunohistochemical staining of VEGFR-3 in the proliferating vessels. The necrotic areas was reduced in the flaps of the pre-con, post-con, and pre + post-con groups and the combined preconditioning and postconditioning group has reduced necrotic area compared to preconditioning of the skin flap.

CONCLUSION

The protective effect was observed on day 7 for combined ischaemic preconditioning and postconditioning. The presence of a protective effect in the late period was separately investigated by immunohistochemical staining of VEGFR-3 in the proliferating vessels.

Natural Hirudin Increases Rat Flap Viability by Anti-Inflammation via PARs/p38/NF-κB Pathway

The present study aimed to evaluate the effect of natural hirudin on rat random skin flap viability and to determine the mechanism. Forty-eight rats were randomly divided into 2 groups. After the dorsal skin flap operation (3 cm × 10 cm in size), subcutaneous injections of 6 ATU hirudin were administered to group H (n = 24) every 12 h, while group C (n = 24) received an equal volume of 0.9% normal saline. Six rats from each group were euthanized 1, 2, 4, and 7 days after the operation. A full skin sample was collected from these rats to measure the p38-mitogen-activated protein kinase (p38-MAPK), phospho-p38- (Pp38-) MAPK, nuclear factor-κB (NF-κB) p65, phosphor-NF-κB (pNF-κB) p65, tumour necrosis factor- (TNF-) α, interleukin- (IL-) 6, and intercellular adhesion molecule- (ICAM-) 1 levels via western blot (WB) assays. The results showed that flap viability was significantly higher in the hirudin-treated group, which showed a reduced inflammatory response compared with the control group. The Pp38/p38, pNF-κB p65/NF-κB p65, TNF-α, IL-6, and ICAM-1 levels in the hirudin-treated group were lower than those in the control group. The results demonstrated that hirudin could improve random skin flap viability and suggested that this effect maybe occurs by blocking the thrombin/proteinase-activated receptors (PARs)/p38/NF-κB signalling pathway, thus decreasing the inflammatory response.

Upper extremity ischemia is superior to lower extremity ischemia for remote ischemic conditioning of antero-lateral thigh cutaneous blood flow

Remote ischemic conditioning (RIC) is known to improve microcirculation in various settings, but little is known about the impact of the amount of ischemic tissue mass or the limb itself. Since ischemia and subsequent necrosis of flaps is one of the most dreaded complications in reconstructive surgery, adjuvant methods to improve microcirculation are desirable. We therefore performed a randomized trial to compare the effect of arm versus leg ischemia for RIC of the cutaneous microcirculation of the antero-lateral thigh. Forty healthy volunteers were randomized to undergo 5 min of ischemia of either the upper or lower extremity, followed by 10 min of reperfusion.Ischemia was induced by a surgical tourniquet applied to the proximal limb, which was inflated to 250 mmHg for the upper and 300 mgHg for the lower extremity. This cycle was repeated a total of three times. Cutaneous microcirculation was assessed by combined laser doppler spectrophotometry on the antero-lateral aspect of the thigh to measure cutaneous blood flow (BF), relative hemoglobin content (rHb), and oxygen saturation (StO2). Baseline measurements were performed for 10 min, after which the ischemia/reperfusion cycles were begun. Measurements were performed continuously and were afterwards pooled to obtain a mean value per minute. Both groups showed significant increases in all three measured parameters of cutaneous microcirculation after three cycles of ischemia/reperfusion when compared to baseline (BF: 95.1% (P < 0.001) and 27.9% (P = 0.002); rHb: 9.4% (P < 0.001) and 5.9% (P < 0.001), StO2: 8.4% (P = 0.045) and 9.4% (P < 0.001). When comparing both groups, BF was significantly higher in the arm group (P = 0.019 after 11 min., P = 0.009 after 45 min). In conclusions, both ischemic conditioning of the upper and lower extremity is able to improve cutaneous BF on the ALT donor site. However, RIC of the upper extremity seems to be a superior trigger for improvement of cutaneous BF.

Comparing different postconditioning cycles after ischemia reperfusion injury in the rat skin flap

Ischemic postconditioning is a useful manipulation to reduce the undesirable effects of ischemia-reperfusion (I/R) injury. The beneficial results of this phenomenon against I/R injury have been seen in several flap models. However, there are no published works comparing different postconditioning (post-con) cycles in skin flaps. In this study, we investigated the effectiveness of different post-con cycles in a skin flap model. Epigastric island flap (6 × 3 cm) model which was based on the left superficial epigastric artery and vein was used, and complete 6 hours of ischemia was generated by occlusion of the pedicle. Forty male Wistar rats were allocated into 5 groups (n = 8 in each group). Group 1 (sham group): the elevated skin flap was repositioned without an episode of ischemia. Group 2 (control group): skin flap was elevated and 6 hours of complete ischemia was induced by clamping the pedicle. Group 3 (post-con 1): After ischemia, post-con was performed by 6 cycles of 15 seconds of repeated I/R periods. Group 4 (post-con 2): After ischemia, post-con was performed by 6 cycles of 30 second of repeated I/R periods. Group 5 (post-con 3): After ischemia, post-con was performed by 6 cycles of 60 second of repeated I/R periods. Flap viability was assessed 1 week after the surgical procedure, the necrotic area of the skin flap was measured using image analysis on the computer. The area of flap necrosis was statistically significant between the control and post-con group 4 and group 5, and no statistically significant difference was obtained between the control and post-con group 3. Groups 4 and 5 demonstrated lesser area of flap necrosis than the control group and group 4 was superior to group 5. The results revealed that the post-con applied by means of 6 cycles of 30 seconds yields the best protection against I/R injury in the rat skin flap model.

Protective effect of hydrogen-rich saline on ischemia/reperfusion injury in rat skin flap

OBJECTIVE

Skin damage induced by ischemia/reperfusion (I/R) is a multifactorial process that often occurs in plastic surgery. The mechanisms of I/R injury include hypoxia, inflammation, and oxidative damage. Hydrogen gas has been reported to alleviate cerebral I/R injury by acting as a free radical scavenger. Here, we assessed the protective effect of hydrogen-rich saline (HRS) on skin flap I/R injury.

METHODS

Abdominal skin flaps of rats were elevated and ischemia was induced for 3 h; subsequently, HRS or physiological saline was administered intraperitoneally 10 min before reperfusion. On postoperative Day 5, flap survival, blood perfusion, the accumulation of reactive oxygen species (ROS), and levels of cytokines were evaluated. Histological examinations were performed to assess inflammatory cell infiltration.

RESULTS

Skin flap survival and blood flow perfusion were improved by HRS relative to the controls. The production of malondialdehyde (MDA), an indicator of lipid peroxidation, was markedly reduced. A multiplex cytokine assay revealed that HRS reduced the elevation in the levels of inflammatory cytokines, chemokines and growth factors, with the exception of RANTES (regulated on activation, normal T-cell expressed and secreted) growth factor. HRS treatment also reduced inflammatory cell infiltration induced by I/R injury.

CONCLUSIONS

Our findings suggest that HRS mitigates I/R injury by decreasing inflammation and, therefore, has the potential for application as a therapy for improving skin flap survival.

Hydrogen sulfide reduces neutrophil recruitment in hind-limb ischemia-reperfusion injury in an L-selectin and ADAM-17-dependent manner

BACKGROUND

Reperfusion following ischemia leads to neutrophil recruitment into injured tissue. Selectins and β2-integrins regulate neutrophil interaction with the endothelium during neutrophil rolling and firm adhesion. Excessive neutrophil infiltration into tissue is thought to contribute to ischemia-reperfusion injury damage. Hydrogen sulfide mitigates the damage caused by ischemia-reperfusion injury. This study's objective was to determine the effect of hydrogen sulfide on neutrophil adhesion receptor expression.

METHODS

Human neutrophils were either left untreated or incubated in 20 μM hydrogen sulfide and/or 50 μg/ml pharmacologic ADAM-17 inhibitor TAPI-0; activated by interleukin-8, fMLP, or TNF-α; and labeled against P-selectin glycoprotein ligand-1, leukocyte function associated antigen-1, Mac-1 α, L-selectin, and β2-integrin epitopes CBRM1/5 or KIM127 for flow cytometry. Cohorts of three C57BL/6 mice received an intravenous dose of saline vehicle or 20 μM hydrogen sulfide with or without 50 μg/ml TAPI-0 before unilateral tourniquet-induced hind-limb ischemia for 3 hours followed by 3 hours of reperfusion. Bilateral gastrocnemius muscles were processed for histology before neutrophil infiltration quantification.

RESULTS

Hydrogen sulfide treatment significantly increased L-selectin shedding from human neutrophils following activation by fMLP and interleukin-8 in an ADAM-17-dependent manner. Mice treated with hydrogen sulfide to raise bloodstream concentration by 20 μM before ischemia or reperfusion showed a significant reduction in neutrophil recruitment into skeletal muscle tissue following tourniquet-induced hind-limb ischemia-reperfusion injury.

CONCLUSIONS

Hydrogen sulfide administration results in the down-regulation of L-selectin expression in activated human neutrophils. This leads to a reduction in neutrophil extravasation and tissue infiltration and may partially account for the protective effects of hydrogen sulfide seen in the setting of ischemia-reperfusion injury.

Combination of hypoxic preconditioning and postconditioning does not induce additive protection of ex vivo human skeletal muscle from hypoxia/reoxygenation injury

We previously demonstrated that hypoxic preconditioning (HPreC) or postconditioning (HPostC) protected ex vivo human skeletal muscle from hypoxia/reoxygenation injury. Here, we investigated if combined HPreC and HPostC could convey additive protection. Human rectus abdominis muscle strips were cultured in normoxic Krebs buffer for 5 hours (control) or in 3 hours hypoxic/2 hours normoxic buffer (treatment groups). HPreC and HPostC were induced by 1 cycle of 5 minutes hypoxia/5 minutes reoxygenation immediately before or after 3 hours hypoxia, respectively. Muscle injury, viability, and adenosine triphosphate (ATP) synthesis were assessed by measuring lactate dehydrogenase release, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide reduction, and ATP content, respectively. Hypoxia/reoxygenation caused lactate dehydrogenase to increase and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide reduction and ATP content to decrease (P < 0.05; n = 7). HPreC, HPostC, and combination of both were equally effective in protection of muscle from hypoxia/reoxygenation injury. Atractyloside (5 × 10 M), a mitochondrial permeability transition pore opener, abolished the protective effect of HPreC or HPostC. We conclude that HPreC and HPostC protect ex vivo human skeletal muscle against hypoxia/reoxygenation injury by closing the mitochondrial permeability transition pore. For that reason, they are equally effective and do not demonstrate an additive effect. Moreover, the potent effect of HPostC indicates ischemic postconditioning as an effective clinical intervention against reperfusion injury in autogenous skeletal muscle transplantation and replantation surgery.

Skeletal muscle post-conditioning by diazoxide, anti-oxidative and anti-apoptotic mechanisms

Pretreatment with diazoxide, K(ATP) channel opener, increases tissue tolerance against ischemia reperfusion (IR) injury. In clinical settings pretreatment is rarely an option therefore we evaluated the effect of post-ischemic treatment with diazoxide on skeletal muscle IR injury. Rats were treated with either saline, diazoxide (K(ATP) opener; 40 mg/kg) or 5-hydroxydecanoate (5-HD; mitochondrial K(ATP) inhibitor; 40 mg/kg) after skeletal muscle ischemia (3 h) and reperfusion (6, 24 or 48 h). Tissue contents of malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) activities, Bax and Bcl-2 protein expression and muscle histology were determined. Apoptosis was examined (24 and 48 h) after ischemia. IR induced severe histological damage, increased MDA content and Bax expression (24 and 48 h; p < 0.01) and decreased CAT and SOD activities (6 and 24 h, p < 0.01 and 48 h, p < 0.05), with no significant effect on Bcl-2 expression. Diazoxide reversed IR effects on MDA (6 and 24 h; p < 0.05), SOD (6 and 24 h; p < 0.01) and CAT (6 and 48 h, p < 0.05 and 24 h p < 0.01) and tissue damage. Diazoxide also decreased Bax (24 and 48 h; p < 0.05) and increased Bcl-2 protein expression (24 and 48 h; p < 0.01). Post-ischemic treatment with 5-HD had no significant effect on IR injury. Number of apoptotic nuclei in IR and 5-HD treated groups significantly increased (p < 0.001) while diazoxide decreased apoptosis (p < 0.01). The results suggested that post-ischemic treatment with diazoxide decrease oxidative stress in acute phase which modulates expression of apoptotic proteins in the late phase of reperfusion injury. Involvement of KATP channels in this effect require further evaluations.

Expression of inducible nitric oxide synthase in muscle flaps treated with ischemic postconditioning

BACKGROUND/OBJECTIVE

Preconditioning has been considered promising for the treatment of ischemic flaps. In this study, the therapeutic effect of postconditioning was compared with that of preconditioning during ischemia/reperfusion (I/R) injury, and a role of inducible nitric oxide synthase (iNOS) in postconditioning treatment was also explored.

METHODS

Sixty rats were randomly divided into four groups with 15 rats in each group. Ischemic injury was induced in a rat's gracilis muscle flap model. Preconditioning and postconditioning were performed respectively on the flaps in the pre-con group and the post-con group. No treatment was given to the flaps in the control group, and flaps without I/R injury were used as a sham control. Muscle viability ratio, histology, and gene expression of iNOS were examined at different time intervals (3, 12, and 18 h).

RESULTS

A significantly higher survival ratio was observed in both the pre-con group (78.98 ± 3.39, 62.74 ± 3.7, and 54.42 ± 4.45 %) and the post-con group (77.42 ± 4.14, 59.74 ± 6.67, and 49.52 ± 4.13 %) than the control group (45.22 ± 3.69, 42.44 ± 3.76, and 33.2 ± 3.29 %) at 3, 12, and 18 h postoperatively (P < 0.05). There was no statistical difference between the pre-con group and the post-con group (P > 0.05). Histological examination showed delayed and attenuated tissue damage in both the pre-con group and the post-con group when compared to that of the control group. A higher expression of iNOS was observed in both the pre-con group and the post-con group than the control group and the sham group (P < 0.05).

CONCLUSIONS

Significant improvement of flap survival could be achieved by both preconditioning and postconditioning treatments; however, better protection could be provided by preconditioning. The higher expression of iNOS may play an important role in the therapeutic effect of postconditioning during I/R injury.

Effects of natural and recombinant hirudin on superoxide dismutase, malondialdehyde and endothelin levels in a random pattern skin flap model

We have assessed the anti-inflammatory, anti-oxidative and anti-coagulant effects of locally applied natural and recombinant hirudin in a random skin flap rat model. Thirty Wistar rats with venous congested skin flaps were randomly divided into two treatment groups and a control group to receive subcutaneous injections of natural hirudin (6 U), recombinant hirudin (6 U) or physiological saline, respectively. Superoxide dismutase, malondialdehyde and endothelin levels as well as flap survival rates of the skin flaps were measured after surgery. Compared to the control group, the treatment groups had significant higher superoxide dismutase levels and lower malondialdehyde and endothelin levels in the skin flaps. The surviving areas of the flaps were larger in the treatment groups than the control group. Our results demonstrated that hirudin could improve skin flap survival through its anti-inflammatory, anti-oxidative and anti-coagulant activities.