Ischemia/reperfusion-induced necrosis and apoptosis in the cells isolated from rat skeletal muscle

Multi-omics analysis of renal vein serum with Ischemia-Reperfusion injury

BACKGROUND

Acute kidney injury (AKI) is frequently caused by renal ischemia-reperfusion injury (IRI). Identifying potential renal IRI disease biomarkers would be useful for evaluating AKI severity.

OBJECTIVE

We used proteomics and metabolomics to investigate the differences in renal venous blood between ischemic and healthy kidneys in an animal model by identifying differentially expressed proteins (DEPs) and differentially expressed protein metabolites (DEMs).

METHODS

Nine pairs of renal venous blood samples were collected before and at 20, 40, and 60 min post ischemia. The ischemia time of Group A, B and C was 20,40 and 60 min. The proteome and metabolome of renal venous blood were evaluated to establish the differences between renal venous blood before and after ischemia.

RESULTS

We identified 79 common DEPs in all samples of Group A, 80 in Group B, and 131 in Group C. Further common DEPs among all three groups were Tyrosineprotein kinase, GPR15LG, KAZALD1, ADH1B. We also identified 81, 64, and 83 common DEMs in each group respectively, in which 30 DEMs were further common to all groups. Bioinformatic analysis of the DEPs and DEMs was conducted.

CONCLUSION

This study demonstrated that different pathological processes occur during short- and long-term renal IRI. Tyrosine protein kinase, GPR15LG, Kazal-type serine peptidase inhibitor domain 1, and all-trans-retinol dehydrogenase are potential biomarkers of renal IRI.

The tourniquet's effects on skeletal muscle during total knee arthroplasty

This study investigates the impact of perioperative tourniquet on skeletal muscle cells during total knee arthroplasty (TKA) and its effects on the gene expression of apoptotic, inflammatory, and angiogenic pathways. The randomized controlled trial included 44 patients undergoing TKA. The patients were randomized to undergo surgery with (n = 23) or without (n = 21) tourniquet. The tourniquet was inflated before skin incision and deflated before wound closure in the tourniquet group. Biopsies from the lateral vastus muscle were obtained from both groups before wound closure and 8 weeks after surgery. The messenger ribonucleic acid (mRNA) expression and protein levels of angiopoietin-like 4 (ANGPTL4), Hypoxia-inducible Factor 1α, and Vascular Endothelial Growth Factor Alpha (VEGF-A) in the biopsies were examined by reverse transcription-quantitative polymerase chain reaction and tissue microarray, respectively. Differences in mean values (ΔCt for mRNA expression and staining positivity for protein expression) were compared with t-tests. The apoptotic marker BID and the angiogenic marker VEGF-A were significantly lower in the tourniquet group compared to the control group (p = 0.03, p = 0.047). However, there was a significant upregulation of VEGF-A 8 weeks after surgery in the tourniquet group compared to perioperative biopsies (p = 0.002), indicating persistent changes. A significant upregulation in protein expression of the angiogenic marker ANGPTL4 was found perioperatively in the tourniquet group (p = 0.02). Our results demonstrate that the angiogenic gene expression is significantly altered by the tourniquet, the effects of which might contribute to postoperative interstitial edema, increased pain, and decreased muscle strength. These effects could lead to delayed rehabilitation and ultimately reduced patient satisfaction after TKA.

Protective Effect of Peptide Calcium Channel Blocker Omega-Hexatoxin-Hv1a on Epithelial Cell during Ischemia-Reperfusion Injury

Ischemia-reperfusion injury (IRI) is a common phenomenon that develops both from natural causes and during major operations. Many intracellular processes mediated by calcium ions are involved in the development of IRI. Currently, chemical calcium channel blockers are used but they have a number of limitations. In this article, we study the effect of the omega-hexatoxin-Hv1a peptide toxin, an alternative to chemical calcium channel blockers, on the mechanisms of IRI development in epithelial cell culture. The toxin was produced using solid phase peptide synthesis. IRI was caused by deprivation of glucose, serum and oxygen. The data obtained demonstrate that the omega-hexatoxin-Hv1a toxin in nanomolar concentrations is able to prevent the development of apoptosis and necrosis in epithelial cells by reducing the concentration of calcium, sodium and potassium ions, as well as by delaying rapid normalization of the pH level, affecting the mitochondrial potential and oxidative stress. This toxin can be used as an alternative to chemical calcium channel blockers for preventing tissue and organ IRI due to its low-dose requirement and high bioavailability.

Soluble components from mesenchymal stromal cell processing exert anti-inflammatory effects and facilitate ischemic muscle regeneration

BACKGROUND AIMS

Skeletal muscle regeneration after severe damage is reliant on local stem cell proliferation and differentiation, processes that are tightly regulated by macrophages. Peripheral artery disease is a globally prevalent cardiovascular disease affecting millions of people. Progression of the disease leads to intermittent claudication, subsequent critical limb ischemia and muscle injury. Tissue-derived and ex vivo-expanded mesenchymal stromal cells (MSCs) for skeletal muscle regeneration have been studied, but pre-clinical and clinical results have not been consistent. As a result, the potential therapeutic efficacy and associated repair mechanisms of MSCs remain unclear. Numerous studies have demonstrated the vulnerability of delivered MSCs, with a precipitous drop in cell viability upon transplantation. This has prompted investigation into the therapeutic benefit of apoptotic cells, microvesicles, exosomes and soluble signals that are released upon cell death.

METHODS

In this study, we characterized various components produced by MSCs after cell death induction under different conditions. We discovered anti-inflammatory and pro-regenerative effects produced by cell components following a freeze and thaw (F&T) process on macrophage polarization in vitro. We further investigated the underlying mechanisms of macrophage polarization by those components resulting from severe cell death induction.

RESULTS

We found potent therapeutic effects from F&T-induced cell debris are dependent on the externalization of phosphatidylserine on the plasma membrane. In contrast, effects from the supernatant of F&T-induced cell death primarily depends on the released protein content. We then applied the F&T-induced cell supernatant to an animal model of peripheral artery disease to treat muscle injury caused by severe ischemia. Treatment with the F&T supernatant but not the vulnerable MSCs resulted in significantly improved recovery of muscle function, blood flow and morphology and inflammation resolution in the affected muscles 2 weeks after injury.

CONCLUSIONS

This study validates the therapeutic potential of F&T-induced supernatant obviating the need for a viable population from vulnerable MSCs to treat injury, thus providing a roadmap for cell-free therapeutic approaches for tissue regeneration.

Neutrophil dynamics and inflammaging in acute ischemic stroke: A transcriptomic review

Stroke is among the leading causes of death and disability worldwide. Restoring blood flow through recanalization is currently the only acute treatment for cerebral ischemia. Unfortunately, many patients that achieve a complete recanalization fail to regain functional independence. Recent studies indicate that activation of peripheral immune cells, particularly neutrophils, may contribute to microcirculatory failure and futile recanalization. Stroke primarily affects the elderly population, and mortality after endovascular therapies is associated with advanced age. Previous analyses of differential gene expression across injury status and age identify ischemic stroke as a complex age-related disease. It also suggests robust interactions between stroke injury, aging, and inflammation on a cellular and molecular level. Understanding such interactions is crucial in developing effective protective treatments. The global stroke burden will continue to increase with a rapidly aging human population. Unfortunately, the mechanisms of age-dependent vulnerability are poorly defined. In this review, we will discuss how neutrophil-specific gene expression patterns may contribute to poor treatment responses in stroke patients. We will also discuss age-related transcriptional changes that may contribute to poor clinical outcomes and greater susceptibility to cerebrovascular diseases.

Therapeutic Targets for Regulating Oxidative Damage Induced by Ischemia-Reperfusion Injury: A Study from a Pharmacological Perspective

Ischemia-reperfusion (I-R) injury is damage caused by restoring blood flow into ischemic tissues or organs. This complex and characteristic lesion accelerates cell death induced by signaling pathways such as apoptosis, necrosis, and even ferroptosis. In addition to the direct association between I-R and the release of reactive oxygen species and reactive nitrogen species, it is involved in developing mitochondrial oxidative damage. Thus, its mechanism plays a critical role via reactive species scavenging, calcium overload modulation, electron transport chain blocking, mitochondrial permeability transition pore activation, or noncoding RNA transcription. Other receptors and molecules reduce tissue and organ damage caused by this pathology and other related diseases. These molecular targets have been gradually discovered and have essential roles in I-R resolution. Therefore, the current study is aimed at highlighting the importance of these discoveries. In this review, we inquire about the oxidative damage receptors that are relevant to reducing the damage induced by oxidative stress associated with I-R. Several complications on surgical techniques and pathology interventions do not mitigate the damage caused by I-R. Nevertheless, these therapies developed using alternative targets could work as coadjuvants in tissue transplants or I-R-related pathologies

Ischemia-Reperfusion Injury in Peripheral Artery Disease and Traditional Chinese Medicine Treatment

Peripheral artery disease (PAD) is a serious public health issue, characterized by circulation disorder of the lower extreme that reduces the physical activity of the lower extremity muscle. The artery narrowed by atherosclerotic lesions initiates limb ischemia. In the progression of treatment, reperfusion injury is still inevitable. Ischemia-reperfusion injury induced by PAD is responsible for hypoxia and nutrient deficiency. PAD triggers hindlimb ischemia and reperfusion (I/R) cycles through various mechanisms, mainly including mitochondrial dysfunction and inflammation. Alternatively, mitochondrial dysfunction plays a central role. The I/R injury may cause cells' injury and even death. However, the mechanism of I/R injury and the way of cell damage or death are still unclear. We review the pathophysiology of I/R injury, which is majorly about mitochondrial dysfunction. Then, we focus on the cell damage and death during I/R injury. Further comprehension of the progress of I/R will help identify biomarkers for diagnosis and therapeutic targets to PAD. In addition, traditional Chinese medicine has played an important role in the treatment of I/R injury, and we will make a brief introduction.

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.

Extracorporeal perfusion - reduced to a one-way infusion

BACKGROUND

Extracorporeal perfusion (EP) is moving into focus of research in reconstructive and transplantation medicine for the preservation of amputates and free tissue transplants. The idea behind EP is the reduction of ischemia-related cell damage between separation from blood circulation and reanastomosis of the transplant. Most experimental approaches are based on a complex system that moves the perfusate in a circular course.

OBJECTIVE AND METHODS

In this study, we aimed to evaluate if a simple perfusion by an infusion bag filled with an electrolyte solution can provide acceptable results in terms of flow stability, oxygen supply and viability conservation for EP of a muscle transplant. The results are compared to muscles perfused with a pump system as well as muscles stored under ischemic conditions after a one-time intravasal flushing with Jonosteril.

RESULTS

With this simple method a sufficient oxygen supply could be achieved and functionality could be maintained between 3.35 times and 4.60 times longer compared to the control group. Annexin V positive nuclei, indicating apoptosis, increased by 9.7% in the perfused group compared to 24.4% in the control group.

CONCLUSIONS

Overall, by decreasing the complexity of the system, EP by one-way infusion can become more feasible in clinical situations.

Inhibitory effect of edaravone on systemic inflammation and local damage in skeletal muscles following long-term ischemia to murine hind limb

PURPOSE

The purpose of this study was to evaluate local and systemic pathology in a murine model of ischemia-reperfusion (I/R) injury induced by long-term application of a tourniquet on the hind limbs and to assess the protective effects of edaravone, a potent systemic scavenger of free radicals, using this model.

METHODS

Sixty C57BL6 mice were divided in two groups, with one group receiving a 3 mg/kg intraperitoneal injection of edaravone and the other group receiving an identical amount of saline 30 min before ischemia under deep anesthesia. The left thigh of each animal was constricted for 4 h with a 4.5-oz. orthodontic rubber band to induce ischemia; 4 h was the critical duration for skeletal muscles. After ischemia, specimens of skeletal muscles, both kidneys, and plasma were collected at 0, 2, 12, 24, 48, and 72 h. Injury to the skeletal muscles and vacuolar degeneration of the kidneys were histologically assessed. Additionally, apoptosis of skeletal muscle cells was assessed by analysis of caspase 3/7 activity and TUNEL staining. Plasma tumor necrosis factor (TNF)-α levels were measured using an enzyme-linked immunosorbent assay kit.

RESULTS

Skeletal muscles exhibited prominent injury of myofibers at 12 h after I/R injury, with clear upregulation of plasma TNF-α expression and histologic evidence of tubular dysfunction of the kidneys. Plasma TNF-α levels declined and histologic renal damage was ameliorated in edaravone-treated mice, but treatment did not protect skeletal muscle following ischemia for 4 h. Nonetheless, compared with group S, expression of the apoptosis marker caspase 3/7 was significantly inhibited in the skeletal hind limb muscles of Ed-group mice affected by reperfusion injury following ischemia for 4 h.

CONCLUSION

The present study demonstrated that edaravone is a potentially useful drug for systemic or local treatment of reperfusion injury resulting from long-term ischemia.

Revascularization and limb salvage following critical limb ischemia by nanoceria-induced Ref-1/APE1-dependent angiogenesis

In critical limb ischemia (CLI), overproduction of reactive oxygen species (ROS) and impairment of neovascularization contribute to muscle damage and limb loss. Cerium oxide nanoparticles (CNP, or 'nanoceria') possess oxygen-modulating properties which have shown therapeutic utility in various disease models. Here we show that CNP exhibit pro-angiogenic activity in a mouse hindlimb ischemia model, and investigate the molecular mechanism underlying the pro-angiogenic effect. CNP were injected into a ligated region of a femoral artery, and tissue reperfusion and hindlimb salvage were monitored for 3 weeks. Tissue analysis revealed stimulation of pro-angiogenic markers, maturation of blood vessels, and remodeling of muscle tissue following CNP administration. At a dose of 0.6 mg CNP, mice showed reperfusion of blood vessels in the hindlimb and a high rate of limb salvage (71%, n = 7), while all untreated mice (n = 7) suffered foot necrosis or limb loss. In vitro, CNP promoted endothelial cell tubule formation via the Ref-1/APE1 signaling pathway, and the involvement of this pathway in the CNP response was confirmed in vivo using immunocompetent and immunodeficient mice and by siRNA knockdown of APE1. These results demonstrate that CNP provide an effective treatment of CLI with excessive ROS by scavenging ROS to improve endothelial survival and by inducing Ref-1/APE1-dependent angiogenesis to revascularize an ischemic limb.

Pyruvate Protects Against Intestinal Injury by Inhibiting the JAK/STAT Signaling Pathway in Rats With Hemorrhagic Shock

BACKGROUND

This study aimed to investigate the role of Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway in protection by peritoneal resuscitation (PR) using pyruvate-peritoneal dialysis solution (PY-PDS) against intestinal injury from hemorrhagic shock (HS) in rats.

MATERIALS AND METHODS

Sixty-four rats were assigned to eight groups: group SHAM; group intravenous resuscitation (VR); groups NS, LA, and PY in which the rats were subjected to HS and PR with normal saline (NS), lactate-peritoneal dialysis solution (LA-PDS), and PY-PDS, respectively, combined with VR; and groups DMSO, RPM, and AG490 in which the rats were subjected to HS and VR with pretreatment of dimethyl sulfoxide (DMSO), rapamycin (RPM), and tyrphostin B42 (AG490).

RESULTS

At 2 h after HS and resuscitation, the levels of diamine oxidase, 15-F_2t-isoprostane, thromboxane B₂, and endothelin-1, in the blood and the intestinal mucosal apoptotic index and caspase-3 were lower in groups PY, RPM, and AG490 than in groups VR, NS, LA, and DMSO. Group PY showed lower levels of malondialdehyde and myeloperoxidase and a higher level of superoxide dismutase than groups VR, NS, and LA. Phosphorylated JAK2 and phosphorylated STAT3 levels were lower in groups PY, RPM, AG490, and LA than in groups VR, NS, and DMSO.

CONCLUSIONS

The protection mechanism of PR with PY-PDS combined with VR was related to the inhibition of the JAK/STAT signaling pathway during HS and resuscitation. The process might include suppression of oxidative stress, reduction of neutrophil infiltration, regulation of microcirculation, and inhibition of apoptosis.

Protective effects of epigallocatechin gallate against ischemia reperfusion injury in rat skeletal muscle via activating Nrf2/HO-1 signaling pathway

AIMS

Previous studies have demonstrated that epigallocatechin gallate (EGCG) had certain protective effects on myocardial and renal ischemia reperfusion (I/R) injury. We aimed to research the special effects and underling mechanisms of EGCG on skeletal muscle I/R injury.

MAIN METHOD

We established an experimental rat model of I/R skeletal muscle injury and treated with different doses of EGCG. Hematoxylin eosin staining, TUNEL assay, ELISA, qRT-PCR and Western blotting were used to evaluate the effects of EGCG.

KEY FINDINDS

EGCG significantly improved skeletal muscle function of I/R injury rats. Moreover, EGCG had positive effects on decreasing apoptosis of skeletal muscle tissues, alleviating oxidative stress damage and suppressing the production of inflammatory cytokines. Further, EGCG had positive effects on activating Nrf2/HO-1 signaling pathway.

SIGNIFICANCE

EGCG might be a powerful candidate compound for alleviating I/R injury in rat skeletal muscle.

Chronic intermittent hypobaric hypoxia attenuates skeletal muscle ischemia-reperfusion injury in mice

AIM

The aim of this study was to investigate the protective effect of chronic intermittent hypobaric hypoxia (CIHH) against skeletal muscle ischemia-reperfusion (IR) injury and to determine the underlying mechanism.

MAIN METHODS

C57BL/6 mice were randomly divided into 3 groups: skeletal muscle IR injury group (IR), CIHH pretreatment following IR group (IR + CIHH), and sham operation group (Sham). The skeletal muscle IR injury model was induced by the unilateral application of a tourniquet on a hind limb for 3 h and then releasing it for 24 h. CIHH pretreatment simulating a 5000-m altitude was applied 6 h per day for 28 days. The functional and morphological performance of IR-injured gastrocnemius muscle was evaluated using contraction force, H&E staining, and transmission electron microscopy. IR injury-induced CD68⁺ macrophage infiltration was assessed by immunofluorescence. TNFα levels in serum and muscle were measured by ELISA and western blotting, respectively. Apoptosis was examined by TUNEL staining and Cleaved Caspase-3 protein expression.

KEY FINDINGS

Acute IR injury resulted in reduced contraction tension, morphological destruction, macrophage infiltration, increased TNFα levels, and apoptosis in gastrocnemius muscle. CIHH pretreatment significantly ameliorated contraction function and morphological performance in IR-injured skeletal muscle. In addition, CIHH pretreatment resulted in marked decreases in CD68⁺ macrophage infiltration, TNFα levels, and apoptosis.

SIGNIFICANCE

These data demonstrated that CIHH has a protective effect against acute IR injury in skeletal muscle via inhibition of inflammation and apoptosis.

The Inflammatory Response After Ischemic Stroke: Targeting β2 and β1 Integrins

Ischemic stroke is a leading cause of death and disability with limited therapeutic options. Resulting inflammatory mechanisms after reperfusion (removal of the thrombus) result in cytokine activation, calcium influx, and leukocytic infiltration to the area of ischemia. In particular, leukocytes migrate toward areas of inflammation by use of integrins, particularly integrins β1 and β2. Integrins have been shown to be necessary for leukocyte adhesion and migration, and thus are of immediate interest in many inflammatory diseases, including ischemic stroke. In this review, we identify the main integrins involved in leukocytic migration following stroke (α L β2, αDβ2, α4β1, and α5β1) and targeted clinical therapeutic interventions.

Botulinum toxin type A induces protective autophagy in human dermal microvascular endothelial cells exposed to an in vitro model of ischemia/reperfusion injury

Botulinum toxin type A (BTXA) has been reported to increase the survival of ischemic skin flaps; however, the exact mechanism underlying this effect remains unclear and needs to be further established. The present study aimed to elucidate whether autophagy caused by BTXA functions as a protection mechanism and to identify the mechanisms of its regulation by BTXA in human dermal microvascular endothelial cells (HDMECs) subjected to hypoxia/reoxygenation (H/R)-induced injury. HDMECs were harvested from the upper eyelid tissues of female blepharoplasty patients. HDMECs were exposed to BTXA treatment for 12 h and then subjected to hypoxia for 8 h, followed by reoxygenation for 24 h. Chloroquine diphosphate salt (CQ) was used as an autophagy inhibitor. H/R led to extreme injury to the HDMECs as indicated by the rise in the apoptosis rate, which was significantly attenuated by BTXA pretreatment. The outcomes demonstrated that H/R caused autophagy, as evidenced by a higher type II/type I ratio of light chain 3 (LC3), increased expression of Beclin-1 and increased autophagosome formation. BTXA enhanced autophagy and attenuated apoptosis in a dose-dependent manner, whereas CQ attenuated the BTXA antiapoptotic effects and inhibited the formation of autophagolysosomes, which caused clustering of the LC3-II in cells. In conclusion, autophagy promoted by BTXA serves as a potential protective effect on ischemia/reperfusion injury.

The Antiapoptosis Effect of Geum japonicum Thunb. var. chinense Extracts on Cerebral Ischemia Reperfusion Injury via PI3K/Akt Pathway

Geum japonicum Thunb. var. chinense (GJ) is a type of wild vegetable found in China and other Asian countries; it has been reported that its extracts possess a neuroprotective effect against cerebral ischemia reperfusion (CIR) injury. The aim of this study is to explore the effect GJ extracts on transient focal CIR injury and neurons apoptosis and to clarify its possible underlying mechanisms in vivo. Our results indicated that pretreatment with GJ extracts significantly ameliorated the infarct volume, decreased neurological deficits, lessened neural cells apoptosis, downregulated GFAP activity level, and increased surviving neurons. Moreover, GJ extracts preadministration increased Bcl-2 levels and attenuated the increase in the expressions of Bax and it also lowered the cleaved caspase-3 activity in ischemic cortex tissues which was caused by CIR and increased the expression of PI3K and p-Akt. The above effects of high dose of GJ (GJ-H) group were much better than those of low dose of GJ (GJ-L), which indicated that GJ extracts may be helpful in the suppression of CIR injury with a dose-dependent manner.

Reduced Hypoxia-Related Genes in Porcine Limbs in Ex Vivo Hypothermic Perfusion Versus Cold Storage

BACKGROUND

Ischemia-reperfusion injury remains the major limiting factor for limb replantation and transplantation. Static cold storage (SCS) on ice currently represents the standard mode of preservation but is limited to 6 h of duration. Ex vivo machine perfusion has evolved as a potential alternative to safely extend the duration of ex vivo preservation by providing continuous supply of oxygen and nutrients. This study aims to evaluate underlying molecular mechanisms of both preservation modalities.

METHODS

We assessed molecular changes in amputated porcine forelimbs stored on ice at 4°C for 2 h (n = 2) and limbs perfused with Perfadex solution at 10°C for 2 h (n = 3) or 12 h (n = 3) before replantation. Muscle biopsies were examined for histological changes and gene expression levels using H&E staining and a hypoxia-related PCR gene array, respectively.

RESULTS

Histology revealed only minor differences between the ice (SCS) and perfusion groups after 2 h of preservation, with decreased muscle fiber disruption in the perfusion groups compared with the ice (SCS) group. Perfused limbs demonstrated downregulation of genes coding for glycolytic pathways and glucose transporters after 2 h and 12 h when compared with SCS after 2 h. Similarly, genes that induce angiogenesis and those that are activated on DNA damage were downregulated in both perfusion groups as compared with SCS.

CONCLUSIONS

Perfusion of porcine limbs resulted in less activation of hypoxia-related gene families when compared with SCS. This may indicate a state more closely resembling physiological conditions during perfusion and potentially limiting ischemic injury. Our study confirms ex vivo perfusion for up to 12 h as a viable alternative for preservation of vascularized composite tissues.

Tissue conservation for transplantation

Pathophysiological changes that occur during ischemia and subsequent reperfusion cause damage to tissues procured for transplantation and also affect long-term allograft function and survival. The proper preservation of organs before transplantation is a must to limit these injuries as much as possible. For decades, static cold storage has been the gold standard for organ preservation, with mechanical perfusion developing as a promising alternative only recently. The current literature points to the need of developing dedicated preservation protocols for every organ, which in combination with other interventions such as ischemic preconditioning and therapeutic additives offer the possibility of improving organ preservation and extending it to multiple times its current duration. This review strives to present an overview of the current body of knowledge with regard to the preservation of organs and tissues destined for transplantation.

Soft-tissue damage during total knee arthroplasty: Focus on tourniquet-induced metabolic and ionic muscle impairment

PURPOSE

Advantages of tourniquet use in TKA include benefits for surgeons and patients, varying from a bloodless operation site to a reduced intervention time. The time under ischemia and the reperfusion period are crucial phases for affected soft-tissue, most commonly the extensor mechanism.

CASE REPORTS

documented its impact on soft-tissue, ranging from necrotic muscle damage to systemic inflammation. Recently, research regarding tourniquet application patterns discuss clinical outcome parameters in the context of soft-tissue damage, excluding the underlying pathophysiological mechanisms.

METHODS

This review summarizes the molecular aspects of soft-tissue damage occurring during tourniquet application in TKA with special focus on ischemia/reperfusion injury. Recent meta-analyses and original trials were reviewed for data on muscle damage and are presented.

CONCLUSION

Although underlying pathomechanisms are well known and presented, clinical orthopedic research has so far not addressed this issue. In context of physical training, positive effects regarding postoperative recovery might be possible if more attention is paid to prepare involved muscle preoperatively to TKA (prehabilitation).

[Skeletal muscle ischemia-reperfusion and ischemic conditioning pathophysiology-clinical applications for the vascular surgeon]

Ischemia-reperfusion, which is characterized by deficient oxygen supply and subsequent restoration of blood flow, can cause irreversible damage to tissue. The vascular surgeon is daily faced with ischemia-reperfusion situations. Indeed, arterial clamping induces ischemia, followed by reperfusion when declamping. Mechanisms underlying ischemia-reperfusion injury are complex and multifactorial. Increases in cellular calcium and reactive oxygen species, initiated during ischemia and then amplified upon reperfusion are thought to be the main mediators of reperfusion injury. Mitochondrial dysfunction also plays an important role. Extensive research has focused on increasing skeletal muscle tolerance to ischemia-reperfusion injury, especially through the use of ischemic conditioning strategies. The purpose of this review is to focus on the cellular responses associated with ischemia-reperfusion, as well as to discuss the effects of ischemic conditioning strategies. This would help the vascular surgeon in daily practice, in order to try to improve surgical outcome in the setting of ischemia-reperfusion.

Inhibition of coagulation proteases Xa and IIa decreases ischemia-reperfusion injuries in a preclinical renal transplantation model

Coagulation is an important pathway in the pathophysiology of ischemia-reperfusion injuries. In particular, deceased after circulatory death (DCD) donors undergo a no-flow period, a strong activator of coagulation. Hence, therapies influencing the coagulation cascade must be developed. We evaluated the effect of a new highly specific and effective anti-Xa/IIa molecule, with an integrated innovative antidote site (EP217609), in a porcine preclinical model mimicking injuries observed in DCD donor kidney transplantation. Kidneys were clamped for 60 minutes (warm ischemia), then flushed and preserved for 24 hours at 4°C in University of Wisconsin (UW) solution (supplemented or not). EP217609-supplemented UW solution (UW-EP), compared with unfractionated heparin-supplemented UW solution (UW-UFH) or UW alone (UW). A mechanistic investigation was conducted in vitro: addition of EP217609 to endothelial cells during hypoxia at 4°C in the UW solution inhibited thrombin generation during reoxygenation at 37°C in human plasma and reduced tumor necrosis factor alpha, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 messenger RNA cell expressions. In vivo, function recovery was markedly improved in the UW-EP group. Interestingly, levels of thrombin-antithrombin complexes (reflecting thrombin generation) were reduced 60 minutes after reperfusion in the UW-EP group. In addition, 3 months after transplantation, lower fibrosis, epithelial-mesenchymal transition, inflammation, and leukocyte infiltration were observed. Using this new dual anticoagulant, anti-Xa/IIa activity during kidney flush and preservation is protected by reducing thrombin generation at revascularization, improving early function recovery, and decreasing chronic lesions. Such an easy-to-deploy clinical strategy could improve marginal graft outcome.

Effect of PpIX photoproducts formation on pO2 measurement by time-resolved delayed fluorescence spectroscopy of PpIX in solution and in vivo

The measurement of Protoporphyrin IX delayed fluorescence lifetime is a minimally invasive method for monitoring the levels of oxygen in cells and tissues. The excitation of Protoporphyrin IX during this measurement can lead to the formation of photoproducts in vitro and in vivo. The influence of their luminescence on the measured Protoporphyrin IX delayed fluorescence lifetimes was studied in solution and in vivo on the Chick's chorioallantoic membrane (CAM) model under various oxygen enriched air conditions (0mmHg, 37mmHg and 155mmHg). The presence of photoproducts disturbs such measurements since the delayed fluorescence emission of some of them spectrally overlaps with that of Protoporphyrin IX. One possible way to avoid this obstacle is to detect Protoporphyrin IX's delayed fluorescence lifetime in a very specific spectral range (620-640nm). Another possibility is to excite Protoporphyrin IX with light doses much lower than 10J/cm², quite possibly as low as a fraction 1J/cm² at 405nm. This leads to an increased accuracy of pO₂ detection. Furthermore, this method allows combination of diagnosis and therapy in one step. This helps to improve detection systems and real-time identification of tissue respiration, which is tuned for the detection of PpIX luminescence and not its photoproducts.

Chronology of mitochondrial and cellular events during skeletal muscle ischemia-reperfusion

Peripheral artery disease (PAD) is a common circulatory disorder of the lower limb arteries that reduces functional capacity and quality of life of patients. Despite relatively effective available treatments, PAD is a serious public health issue associated with significant morbidity and mortality. Ischemia-reperfusion (I/R) cycles during PAD are responsible for insufficient oxygen supply, mitochondriopathy, free radical production, and inflammation and lead to events that contribute to myocyte death and remote organ failure. However, the chronology of mitochondrial and cellular events during the ischemic period and at the moment of reperfusion in skeletal muscle fibers has been poorly reviewed. Thus, after a review of the basal myocyte state and normal mitochondrial biology, we discuss the physiopathology of ischemia and reperfusion at the mitochondrial and cellular levels. First we describe the chronology of the deleterious biochemical and mitochondrial mechanisms activated by I/R. Then we discuss skeletal muscle I/R injury in the muscle environment, mitochondrial dynamics, and inflammation. A better understanding of the chronology of the events underlying I/R will allow us to identify key factors in the development of this pathology and point to suitable new therapies. Emerging data on mitochondrial dynamics should help identify new molecular and therapeutic targets and develop protective strategies against PAD.

Assessing viability of extracorporeal preserved muscle transplants using external field stimulation: a novel tool to improve methods prolonging bridge-to-transplantation time

Preventing ischemia-related cell damage is a priority when preserving tissue for transplantation. Perfusion protocols have been established for a variety of applications and proven to be superior to procedures used in clinical routine. Extracorporeal perfusion of muscle tissue though cumbersome is highly desirable since it is highly susceptible to ischemia-related damage. To show the efficacy of different perfusion protocols external field stimulation can be used to immediately visualize improvement or deterioration of the tissue during active and running perfusion protocols. This method has been used to show the superiority of extracorporeal perfusion using porcine rectus abdominis muscles perfused with heparinized saline solution. Perfused muscles showed statistically significant higher ability to exert force compared to nonperfused ones. These findings can be confirmed using Annexin V as marker for cell damage, perfusion of muscle tissue limits damage significantly compared to nonperfused tissue. The combination of extracorporeal perfusion and external field stimulation may improve organ conservation research.

Influence of glutathione-S-transferase (GST) inhibition on lung epithelial cell injury: role of oxidative stress and metabolism

Oxidant-mediated tissue injury is key to the pathogenesis of acute lung injury. Glutathione- S-transferases (GSTs) are important detoxifying enzymes that catalyze the conjugation of glutathione with toxic oxidant compounds and are associated with acute and chronic inflammatory lung diseases. We hypothesized that attenuation of cellular GST enzymes would augment intracellular oxidative and metabolic stress and induce lung cell injury. Treatment of murine lung epithelial cells with GST inhibitors, ethacrynic acid (EA), and caffeic acid compromised lung epithelial cell viability in a concentration-dependent manner. These inhibitors also potentiated cell injury induced by hydrogen peroxide (H2O2), tert-butyl-hydroperoxide, and hypoxia and reoxygenation (HR). SiRNA-mediated attenuation of GST-π but not GST-μ expression reduced cell viability and significantly enhanced stress (H2O2/HR)-induced injury. GST inhibitors also induced intracellular oxidative stress (measured by dihydrorhodamine 123 and dichlorofluorescein fluorescence), caused alterations in overall intracellular redox status (as evidenced by NAD+/NADH ratios), and increased protein carbonyl formation. Furthermore, the antioxidant N-acetylcysteine completely prevented EA-induced oxidative stress and cytotoxicity. Whereas EA had no effect on mitochondrial energetics, it significantly altered cellular metabolic profile. To explore the physiological impact of these cellular events, we used an ex vivo mouse-isolated perfused lung model. Supplementation of perfusate with EA markedly affected lung mechanics and significantly increased lung permeability. The results of our combined genetic, pharmacological, and metabolic studies on multiple platforms suggest the importance of GST enzymes, specifically GST-π, in the cellular and whole lung response to acute oxidative and metabolic stress. These may have important clinical implications.

Hydrogen-rich saline attenuates ischemia-reperfusion injury in skeletal muscle

BACKGROUND

To investigate the potential beneficial effect of hydrogen-rich saline (HRS) in ischemia-reperfusion (IR) injury of skeletal muscle.

METHODS

Three experimental groups were established in male Sprague-Dawley rats: (1) sham group, (2) IR with normal saline group, (3) and IR with HRS group. A rat model of skeletal muscle IR injury was induced by 3-h tourniquet occlusion on its left hind limb and 4-h reperfusion. Normal saline and HRS (1.0 mL/100 g) were administered intraperitoneally at 10 min before reperfusion, respectively. Muscle and serum samples were analyzed for detecting the levels of myeloperoxidase (MPO), superoxide dismutase (SOD), malondialdehyde (MDA), and hydroxyl radical (•OH). Muscle samples were assessed by wet/dry rate, hematoxylin and eosin histologic assessment, Bcl2, Bax, cytochrome C, LC3B, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling, and electron microscopy.

RESULTS

The wet/dry ratio increased significantly in the IR group (P < 0.01 compared with that in the sham group) and decreased significantly in IR with HRS groups (4.12 ± 0.14 versus 4.12 ± 0.14, P < 0.01 compared with that in the IR group). Muscle tissues and serum of the IR group had significantly increased levels of MPO, MDA, •OH content, and decreased SOD activities compared with the sham group (P < 0.01). The activity of SOD in the IR with HRS group was greatly elevated compared with that in the IR group (295.028 ± 9.288 versus 249.190 ± 5.450 in muscle tissues; 91.627 ± 2.604 versus 73.4045 ± 6.487 in serum; P < 0.01), whereas the levels of MPO, MDA, and •OH content were clearly reduced (MPO: 0.5649 ± 0.0724 versus 1.0984 ± 0.0824 in muscle tissues; 0.7257 ± 0.1232 versus 1.3147 ± 0.0531 in serum. MDA: 4.457 ± 0.650 versus 7.107 ± 0.597 in muscle tissues; 2.531 ± 0.434 versus 4.626 ± 0.237 in serum. •OH: 16.451 ± 0.806 versus 19.871 ± 0.594 in muscle tissues; 500.212 ± 7.387 versus 621.352 ± 7.591 in serum, P < 0.01). The integrated optical density of positive amethyst staining increased significantly in the IR group (P < 0.01 compared with that in the sham group) and decreased significantly in IR with HRS group (928.79 ± 234.537 versus 3005.972 ± 83.567, P < 0.01 compared with that in the IR group). Muscle tissues of the IR group had significantly increased levels of Bax, cytochrome C, LC3B content, and decreased Bcl2 activities compared with those in the sham group (P < 0.01). The activity of Bcl2 in the IR with HRS group was greatly elevated compared with that in the IR group (0.2635 ± 0.0704 versus 0.1242 ± 0.0662; P < 0.01), whereas the levels of Bax, cytochrome C, and LC3B content were clearly reduced (Bax: 0.3103 ± 0.0506 versus 0.5122 ± 0.0148; cytochrome C: 0.4194 ± 0.1116 versus 0.8127 ± 0.0166; LC3B: 0.5884 ± 0.0604 versus 1.3758 ± 0.0319; respectively, P < 0.01).

CONCLUSIONS

HRS seems to be effective in attenuating IR injury in skeletal muscle via its antioxidant, anti-apoptosis, and anti-autophagy effect.

Kidney graft outcome using an anti-Xa therapeutic strategy in an experimental model of severe ischaemia-reperfusion injury

BACKGROUND

Deceased after cardiac death donors represent an important source of organs to reduce organ shortage in transplantation. However, these organs are subjected to more ischaemia-reperfusion injury (IRI). Reducing IRI by targeting coagulation is studied here in an experimental model.

METHODS

The effect of an anti-Xa compound (fondaparinux) was evaluated using an autotransplanted kidney model in pigs. Kidneys were clamped for 60 min (warm ischaemia) and then preserved for 24 h at 4 °C in University of Wisconsin solution (UW). The anti-Xa compound was injected intravenously before warm ischaemia and used during cold storage, and its effects were compared with those of intravenous injection of unfractionated heparin (UFH) before warm ischaemia and use during cold storage, or use of UW alone during cold storage.

RESULTS

At 3 months after transplantation, anti-Xa treatment improved recovery of renal function and chronic serum creatinine levels compared with UW and UFH (mean(s.e.m.) 89(4), 250(4) and 217(8) µmol/l respectively). The anti-Xa treatment also reduced fibrosis, and decreased tissue expression of markers of the epithelial-mesenchymal transition compared with UW and UFH. Cleaved protease-activated receptor 2 was overexpressed in the UW group compared with the anti-Xa and UFH groups. Leucocyte infiltrates were decreased in the anti-Xa group compared with the UW and UFH groups. Macrophage invasion was also decreased by anticoagulation treatment.

CONCLUSION

Peritransplant anticoagulation therapy was beneficial to graft outcome, in both the acute and chronic phases. Moreover, specific inhibition of coagulation Xa protease further protected kidney grafts, with better recovery and decreased expression of chronic lesion markers. Surgical relevance The increasing use of marginal donors highlights the importance of organ quality in transplantation. Renal ischaemia-reperfusion injury (IRI), which includes a deleterious activation of coagulation, plays a central role in determining graft quality and outcome. Using an established porcine renal autotransplantation preclinical model with high clinical relevance, the benefits of anticoagulation therapy using an antifactor Xa molecule were evaluated. Peritransplantion anticoagulation treatment, specifically with an anti-Xa compound, protected marginal kidney grafts, improving functional recovery and reducing chronic lesions. This study demonstrates the benefits of anticoagulation therapy at the time of organ collection, particularly for marginal organs, encountered in cases of extended criteria and deceased after circulatory death donors. This anticoagulation strategy could be an important addition to current donor and organ management protocols in order to limit IRI and improve outcome.

Lidocaine-induced ASC apoptosis (tumescent vs. local anesthesia)

BACKGROUND

The purpose for the present study was to determine which anesthetic method, local anesthesia versus tumescent, is superior for liposuction in terms of adipose-derived stem cell (ASC) survival in lipoaspirate; which component, lidocaine versus lidocaine with epinephrine, in anesthetic solutions could affect ASC survival; and which mechanism, necrosis versus apoptosis, is involved in lidocaine-induced ASC death.

METHODS

Human lipoaspirates were harvested using standard liposuction technique. Individuals scheduled for liposuction on bilateral body areas gave consent and were included in the study. On one area, liposuction was conducted under local anesthesia with lidocaine/epinephrine. On the contralateral area, liposuction was accomplished with tumescent wetting solution containing lidocaine/epinephrine. Lipoaspirates were processed for the isolation of stromal vascular fraction (SVF). ASC survival was determined by the number of adherent ASCs after 24 h of SVF culture. Lidocaine dose-response (with or without epinephrine) on cultured ASCs was examined. Lidocaine-induced ASC apoptosis and necrosis was determined by Annexin V-FITC/Propidium Iodide (PI) assay and analyzed by flow cytometry.

RESULTS

All of the participants were female adults. The average age was 45 ± 4.0 years (±SEM) and the average BMI was 28 ± 1.0 (±SEM). Lipoaspirate samples (n = 14) treated by local anesthesia (n = 7/group) or tumescent anesthesia (n = 7/group) were investigated. Liposuction sites were located in the hip or thigh. The average number of adherent ASCs was 1,057 ± 146 k in the local anesthesia group, which was significantly lower than the 1,571 ± 111 k found in the tumescent group (P = 0.01). ASC survival was significantly lower in the lidocaine group and in a dose-dependent manner as compared to the correspondent PBS controls (P < 0.05 or P < 0.01). ASC survival was significantly lower in both the lidocaine and lidocaine with epinephrine groups when compared to PBS controls. Annexin/PI assay showed that ASC apoptosis (but not necrosis) in the lidocaine group was significantly higher than that in the corresponding PBS control (P = 0.026).

CONCLUSIONS

Tumescent anesthesia is the superior method for liposuction with respect to ASC preservation compared to local anesthesia. Lidocaine could cause significant ASC apoptosis.

Sildenafil citrate protects skeletal muscle of ischemia-reperfusion injury: immunohistochemical study in rat model

PURPOSE

To investigate the effect of sildenafil citrate (SC) on skeletal muscle ischemia-reperfusion (IR) injury in rats.

METHODS

Adult male Wistar rats were randomized into three groups: vehicle-treated control (CTG), sildenafil citrate-treated (SCG), and sham group (SG). CTG and SCG had femoral artery occluded for 6 hours. Saline or 1 mg/kg of SC was given 5.5 hours after occlusion. SG had a similar procedure without artery occlusion. Soleus muscle samples were acquired 4 or 24h after the reperfusion. Immunohistochemistry caspase-3 analysis was used to estimate apoptosis using the apoptotic ratio (computed as positive/negative cells). Wilcoxon rank-sum or Kruskal-Wallis tests were used to assess differences among groups.

RESULTS

Eighteen animals were included in the 4h reperfusion groups and 21 animals in the 24h reperfusion groups. The mean apoptotic ratio was 0.18 ± 0.1 for the total cohort; 0.14 ± 0.06 for the 4h reperfusion groups and 0.19 ± 0.08 for the 24h groups (p<0.05). The SCG had lower caspase-3 ratio compared to the control groups at the 24h reperfusion time point (p<0.05).

CONCLUSION

Sildenafil citrate administration after the onset of the ischemic injury reduces IR-induced cellular damage in skeletal muscle in this rat hindlimb ischemia model.

The effect of lipoaspirates cryopreservation on adipose-derived stem cells

BACKGROUND

Autologous fat grafting has gained popularity, particularly with the discovery of adipose-derived stem cells (ADSC). The possibility of freezing lipoaspirates (LA) for later use has intriguing clinical potential. However, the effect of LA cryopreservation on ADSC is unclear.

OBJECTIVES

The authors explore the effect of LA cryopreservation on ADSC viability.

METHODS

Human LA (n = 8) were harvested using a standard technique. Lipoaspirate samples were either processed immediately as fresh LA (A) or stored at -20°C and then at -80°C for 30 days with (B) or without (C) freezing medium. Stromal vascular fraction (SVF) was separated from adipocytes and either cultured to obtain purified ADSC or processed for the isolation of 3 distinct ADSC subpopulations (CD90(+)/CD45(-), CD105(+)/CD45(-), and CD34(+)/CD31(-)). Apoptosis and necrosis were determined by an annexin V/propidium iodide assay and quantified by flow cytometry. The capability of ADSC for long-term proliferation and differentiation was also examined.

RESULTS

There were no significant differences in the apoptosis and necrosis of adipocytes, SVF, or ADSC between groups A and B. However, cell viability in SVF and ADSC was significantly compromised in group C as compared with group B (P < .01) due to higher ADSC apoptosis but not necrosis. The viable ADSC isolated from fresh or frozen LA were cultured for more than 20 passages and demonstrated similar patterns and speed of proliferation with strong capability to differentiate, evidenced by cell doubling time and positive staining with Oil Red O (Sigma-Aldrich, St Louis, Missouri) and alkaline phosphatase.

CONCLUSIONS

Lipoaspirates cryopreservation had a significant impact on ADSC apoptosis but not on ADSC necrosis, proliferation, or differentiations. Freezing medium provides significant protection against ADSC apoptosis.

Analysis for apoptosis and necrosis on adipocytes, stromal vascular fraction, and adipose-derived stem cells in human lipoaspirates after liposuction

BACKGROUND

Adipose-derived stem cells have become the most studied adult stem cells. The authors examined the apoptosis and necrosis rates for adipocyte, stromal vascular fraction, and adipose-derived stem cells in fresh human lipoaspirates.

METHODS

Human lipoaspirate (n = 8) was harvested using a standard liposuction technique. Stromal vascular fraction cells were separated from adipocytes and cultured to obtain purified adipose-derived stem cells. A panel of stem cell markers was used to identify the surface phenotypes of cultured adipose-derived stem cells. Three distinct stem cell subpopulations (CD90/CD45, CD105/CD45, and CD34/CD31) were selected from the stromal vascular fraction. Apoptosis and necrosis were determined by annexin V/propidium iodide assay and analyzed by flow cytometry.

RESULTS

The cultured adipose-derived stem cells demonstrated long-term proliferation and differentiation evidenced by cell doubling time and positive staining with oil red O and alkaline phosphatase. Isolated from lipoaspirates, adipocytes exhibited 19.7 ± 3.7 percent apoptosis and 1.1 ± 0.3 percent necrosis; stromal vascular fraction cells revealed 22.0 ± 6.3 percent of apoptosis and 11.2 ± 1.9 percent of necrosis; stromal vascular fraction cells had a higher rate of necrosis than adipocytes (p < 0.05). Among the stromal vascular fraction cells, 51.1 ± 3.7 percent expressed CD90/CD45, 7.5 ± 1.0 percent expressed CD105/CD45, and 26.4 ± 3.8 percent expressed CD34/CD31. CD34/CD31 adipose-derived stem cells had lower rates of apoptosis and necrosis compared with CD105/CD45 adipose-derived stem cells (p < 0.05).

CONCLUSIONS

Adipose-derived stem cells had a higher rate of apoptosis and necrosis than adipocytes. However, the extent of apoptosis and necrosis was significantly different among adipose-derived stem cell subpopulations.

Pretreatment with brain natriuretic peptide reduces skeletal muscle mitochondrial dysfunction and oxidative stress after ischemia-reperfusion

Brain natriuretic peptide (BNP) reduces the extent of myocardial infarction. We aimed to determine whether BNP may reduce skeletal muscle mitochondrial dysfunctions and oxidative stress through mitochondrial K(ATP) (mK(ATP)) channel opening after ischemia-reperfusion (IR). Wistar rats were assigned to four groups: sham, 3-h leg ischemia followed by 2-h reperfusion (IR), pretreatment with BNP, and pretreatment with 5-hydroxydecanoic acid, an mK(ATP) channel blocker, before BNP. Mitochondrial respiratory chain complex activities of gastrocnemius muscles were determined using glutamate-malate (V(max)), succinate (V(succ)), and N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride ascorbate (V(TMPD/asc)). Apoptosis (Bax-to-Bcl2 mRNA ratio and caspase-3 activity) and oxidative stress (dihydroethidium staining) were also assessed. Compared with the sham group, IR significantly decreased V(max), reflecting complex I, II, and IV activities (-36%, 3.7 ± 0.3 vs. 5.8 ± 0.2 μmol O(2)·min(-1)·g dry wt(-1), P < 0.01), and V(TMPD/asc), reflecting complex IV activity (-37%, 8.6 ± 0.8 vs. 13.7 ± 0.9 μmol O(2)·min(-1)·g dry wt(-1), P < 0.01). IR increased Bax-to-Bcl2 ratio (+57%, 1.1 ± 0.1 vs. 0.7 ± 0.1, P < 0.05) and oxidative stress (+45%, 9,067 ± 935 vs. 6,249 ± 723 pixels, P > 0.05). BNP pretreatment reduced the above alterations, increasing V(max) (+38%, P < 0.05) and reducing Bax-to-Bcl2 ratio (-55%, P < 0.01) and oxidative stress (-58%, P < 0.01). BNP protection against deleterious IR effects on skeletal muscles was abolished by 5-hydroxydecanoic acid. Caspase-3 activities did not change significantly. Conversely, BNP injected during ischemia failed to protect against muscle injury. In addition to maintaining the activity of mitochondrial respiratory chain complexes and possibly decreasing apoptosis, pretreatment with BNP protects skeletal muscle against IR-induced lesions, most likely by decreasing excessive production of radical oxygen species and opening mK(ATP) channels.

Mitochondria-derived superoxide links to tourniquet-induced apoptosis in mouse skeletal muscle

Our previous study has reported that superoxide mediates ischemia-reperfusion (IR)-induced necrosis in mouse skeletal muscle. However, it remains poorly understood whether IR induces apoptosis and what factors are involved in IR-induced apoptosis in skeletal muscle. Using a murine model of tourniquet-induced hindlimb IR, we investigated the relationship between mitochondrial dysfunction and apoptosis in skeletal muscle. Hindlimbs of C57/BL6 mice were subjected to 3 h ischemia and 4 h reperfusion via placement and release of a rubber tourniquet at the greater trochanter. Compared to sham treatment, tourniquet-induced IR significantly elevated mitochondria-derived superoxide production, activated opening of mitochondrial permeability transition pore (mPTP), and caused apoptosis in the gastrocnemius muscles. Pretreatment with a superoxide dismutase mimetic (tempol, 50 mg/kg) or a mitochondrial antioxidant (co-enzyme Q₁₀, 50 mg/kg) not only decreased mitochondria-derived superoxide production, but also inhibited mPTP opening and apoptosis in the IR gastrocnemius muscles. Additionally, an inhibitor of mPTP (cyclosporine A, 50 mg/kg) also inhibited both mPTP opening and apoptosis in the IR gastrocnemius muscles. These results suggest that mitochondria-derived superoxide overproduction triggers the mPTP opening and subsequently causes apoptosis in tourniquet-induced hindlimb IR.

Online oxygen measurements in ex vivo perfused muscle tissue in a porcine model using dynamic quenching methods

INTRODUCTION

Transplantation of autologous free tissue flaps is the best applicable technique for treating large and complex tissue defects and still has one major failure criterion. Tissue--and in particular muscle tissue--is strongly sensitive to ischemia, thus after a critical period of oxygen depletion the risk of a partial or total flap loss is high.

MATERIALS AND METHODS

For that reason a miniaturized ex vivo perfusion system has been developed, that supplies the tissue during operational delays. The purpose of this study was to determine the oxygenation levels during such a perfusion using different perfusates and therefore to objectify if a complementary oxygenation unit is required to improve perfusion quality. The oxygen levels of the tissue, as well of the perfusate, were measured by using minimal invasive optical oxygen sensors that are based on dynamic quenching. The ex vivo perfused tissue was the porcine rectus abdominis muscle.

RESULTS

Results show, that during perfusion with heparinized crystalloid fluid (Jonosteril) and heparinized autologous whole blood, additional oxygenation of the perfusion reactor led to different ex vivo oxygen tissue saturations, which can be detected by dynamic quenching.

CONCLUSION

Dynamic quenching methods are a promising and valuable technique to perform online oxygen measurements in ex vivo perfused muscle tissue in a porcine model.

Affirmative effects of iloprost on apoptosis during ischemia-reperfusion injury in kidney as a distant organ

OBJECTIVE

Apoptosis and its regulatory mechanisms take part in renal ischemia-reperfusion (I/R) injury which can result in acute renal failure and the inhibition of the caspase is considered as a new therapeutic strategy. In this context, we investigated the antiapoptotic and cytoprotective effects of iloprost, a prostacyclin analog, in kidney as a distant organ.

METHODS

Wistar albino rats were randomized into five groups (n = 12 in each) as sham, ischemia, I/R, iloprost (10 μg kg(-1)), and I/R + iloprost (10 μg kg(-1)). A 4 h reperfusion procedure was carried out after 4 h of ischemia. Caspase-8 was evaluated for death receptor-induced pathways, whereas caspase-9 was evaluated for mitochondria-dependent pathways and caspase-3 was investigated for overall apoptosis. Superoxide dismutase (SOD) enzyme activity and nitrite content as an indicator of nitric oxide (NO) production were also analyzed in kidney tissues.

RESULTS

Caspases-3, -8, and -9 were all significantly elevated in both ischemia and I/R groups compared to the sham group; however, treatment with iloprost reduced caspases-3, -8, and -9. SOD enzyme activity was attenuated by iloprost when compared to ischemic rats. The different effects of NO were found which change according to the present situation in ischemia, I/R, and treatment with iloprost.

CONCLUSIONS

These findings suggested that iloprost prevents apoptosis in both receptor-induced and mitochondria-dependent pathways in renal I/R injury and it may be considered as a cytoprotective agent for apoptosis. Understanding the efficiency of iloprost on the pathways for cell death may lead to an opportunity in the therapeutic approach for renal I/R injury.

Gene expression analysis of ischaemia and reperfusion in human microsurgical free muscle tissue transfer

The aim of this study was to analyse various gene expression profiles of muscle tissue during normoxia, ischaemia and after reperfusion in human muscle free flaps, to gain an understanding of the occurring regulatory, inflammatory and apoptotic processes on a cellular and molecular basis. Eleven Caucasian patients with soft tissue defects needing coverage with microsurgical free muscle flaps were included in this study. In all patients, the muscle samples were taken from free myocutaneous flaps. The first sample was taken before induction of ischaemia in normoxia (I), another one after ischaemia (II), and the last one was taken after reperfusion (III). The samples were analysed using DNA-microarray, real-time-quantitative-PCR and immunohistochemistry. DNA-microarray analysis detected multiple, differentially regulated genes when comparing the different groups (I–III) with statistical significance. Comparing ischaemia (II) versus normoxia (I) educed 13 genes and comparing reperfusion (III) versus ischaemia (II) educed 19 genes. The comparison of reperfusion (III) versus normoxia (I) yielded 100 differentially regulated genes. Real-time-quantitative-PCR confirmed the results of the DNA-microarrays for a subset of four genes (CASP8, IL8, PLAUR and S100A8). This study shows that ischaemia and reperfusion induces alterations on the gene expression level in human muscle free flaps. Data may suggest that the four genes CASP8, IL8, PLAUR and S100A8 are of great importance in this context. We could not confirm the DNA-microarry and real-time-quantitative-PCR results on the protein level. Finally, these findings correspond with the surgeon’s clinical experience that the accepted times of ischaemia, generally up to 90 min., are not sufficient to induce pathophysiological processes, which can ultimately lead to flap loss. When inflammatory and apoptotic proteins are expressed at high levels, flap damage might occur and flap loss is likely. The sole expression on mRNA level might explain why flap loss is unlikely.

Extracorporeal perfusion of free muscle flaps in a porcine model using a miniaturized perfusion system

INTRODUCTION

The development of techniques in transplantation medicine--including various aspects--has made extraordinary progress within the past three decades. However, the transplantation of free tissue flaps with the common problem of limited ischemia time frames remains an area in which the understanding of mechanism during ischemia and reperfusion is still limited. Thus, similar to other organ transplantations, the prolongation of ischemic time and the possibility to perform an ex vivo perfusion is desirable. The purpose of this study was to create a closed and steady ex vivo perfusion system in order to analyze the possibility of using a miniaturized perfusion system for free muscle flaps that could also be clinically used for other solid organ transplantation.

MATERIALS AND METHODS

The rectus abdominis muscles of six german pigs were used in the study. Each of these free muscle flaps was perfused for a period of 2 h using a pulsatile and closed pump perfusion system by cannulating the arterial and venous vessels of the flap pedicle. During the ex vivo perfusion parameters such as arterial and venous pressures were measured continuously.

RESULTS

A total of six ex vivo, closed and steady perfusions have been successfully performed. The optimal arterial flow rate of ex vivo perfusion of rectus abdominis muscle flaps was evaluated to be 10 ml/min. The constant measurement of arterial (46 ± 13 mmHg) and venous (-1 ± 1 mmHg) pressure in this ex vivo setting showed steady parameters during a period for up to 2 h.

CONCLUSION

The data of this study indicate that the ex vivo perfusion of free muscle flaps is technically feasible and a closed and steady circulation is manageable for a period of up to 2 h.

Poloxamer 188 protects against ischemia-reperfusion injury in a murine hind-limb model

BACKGROUND

Ischemia-reperfusion injury can activate pathways generating reactive oxygen species, which can injure cells by creating holes in the cell membranes. Copolymer surfactants such as poloxamer 188 are capable of sealing defects in cell membranes. The authors postulated that a single-dose administration of poloxamer 188 would decrease skeletal myocyte injury and mortality following ischemia-reperfusion injury.

METHODS

Mice underwent normothermic hind-limb ischemia for 2 hours. Animals were treated with 150 microl of poloxamer 188 or dextran at three time points: (1) 10 minutes before ischemia; (2) 10 minutes before reperfusion; and (3) 2 or 4 hours after reperfusion. After 24 hours of reperfusion, tissues were analyzed for myocyte injury (histology) and metabolic dysfunction (muscle adenosine 5'-triphosphate). Additional groups of mice were followed for 7 days to assess mortality.

RESULTS

When poloxamer 188 treatment was administered 10 minutes before ischemia, injury was reduced by 84 percent, from 50 percent injury in the dextran group to 8 percent injury in the poloxamer 188 group (p < 0.001). When administered 10 minutes before reperfusion, poloxamer 188 animals demonstrated a 60 percent reduction in injury compared with dextran controls (12 percent versus 29 percent). Treatment at 2 hours, but not at 4 hours, postinjury prevented substantial myocyte injury. Preservation of muscle adenosine 5'-triphosphate paralleled the decrease in myocyte injury in poloxamer 188-treated animals. Poloxamer 188 treatment significantly reduced mortality following injury (10 minutes before, 75 percent versus 25 percent survival, p = 0.0077; 2 hours after, 50 percent versus 8 percent survival, p = 0.032).

CONCLUSION

Poloxamer 188 administered to animals decreased myocyte injury, preserved tissue adenosine 5'-triphosphate levels, and improved survival following hind-limb ischemia-reperfusion injury.

Melatonin attenuates I/R-induced mitochondrial dysfunction in skeletal muscle

BACKGROUND

Our recent studies have shown that ischemia/reperfusion (I/R) produces significant necrosis and apoptosis in the cells of skeletal muscle. Our previous studies also demonstrated that melatonin provides significant protection against superoxide generation, endothelial dysfunction, and cell death in the skeletal muscle after I/R. Mitochondria are essential for cell survival, because of their roles as ATP producers as well as regulators of cell death. However, the efficacy of melatonin on I/R-induced mitochondrial dysfunction in the skeletal muscle in vivo has not been demonstrated in the literature.

MATERIALS AND METHODS

Vascular pedicle isolated rat gracilis muscle model was used. After 4 h of ischemia followed by 24 h of reperfusion, gracilis muscle was harvested, and mitochondrial as well as cytosolic fractions were isolated. Mitochondrial dysfunction was determined by the alteration of mitochondrial membrane potential and the release of the proapoptotic protein, cytochrome c. Three groups were designed; sham I/R, I/R-V (I/R with vehicle), and I/R-Mel (I/R with melatonin). Melatonin or vehicle was given intravenously 10 min prior to reperfusion and 10 min after reperfusion.

RESULTS

We found that the capability of uptake of fluorescent JC-1 dye in skeletal muscle cells was substantially improved in I/R-Mel group compared with I/R-V group. Melatonin significantly inhibited the outflow of cytochrome c from mitochondria to cytoplasm, which was demonstrated in the I/R-V group.

CONCLUSIONS

Melatonin significantly attenuates I/R-induced mitochondrial dysfunction, such as the depolarization of mitochondrial membrane potential and the release of the proapoptotic protein, cytochrome c, from the mitochondria.