Reperfusion Injury

A World Update of Progress in Lower Extremity Transplantation: What's Hot and What's Not

ABSTRACT

The field of vascularized composite allotransplantation (VCA) is the new frontier of solid organ transplantation (SOT). VCA spans life-enhancing/life-changing procedures such as upper extremity, craniofacial (including eye), laryngeal, tracheal, abdominal wall, penis, and lower extremity transplants. VCAs such as uterus transplants are life giving unlike any other SOT. Of all VCAs that have shown successful intermediate- to long-term graft survival with functional and immunologic outcomes, lower extremity VCAs have remained largely underexplored. Lower extremity transplantation (LET) can offer patients with improved function compared to the use of conventional prostheses, reducing concerns of phantom limb pain and stump complications, and offer an option for eligible amputees that either fail prosthetic rehabilitation or do not adapt to prosthetics. Nevertheless, these benefits must be carefully weighed against the risks of VCA, which are not trivial, including the adverse effects of lifelong immunosuppression, extremely challenging perioperative care, and delayed nerve regeneration. There have been 5 lower extremity transplants to date, ranging from unilateral or bilateral to quadrimembral, progressively increasing in risk that resulted in fatalities in 3 of the 5 cases, emphasizing the inherent risks. The advantages of LET over prosthetics must be carefully weighed, demanding rigorous candidate selection for optimal outcomes.

DIEP flap perfusion assessment using microdialysis versus Doppler ultrasonography: A comparative study

BACKGROUND

The increasing number of buried free-tissue transfer procedures and the need for an objective method to evaluate vascular complications of free flaps has led to the development of new technologies. Microdialysis has been used to monitor free flaps using interstitial biological markers. Previous uses mainly focused on muscular flaps. Our aim is to compare external Doppler ultrasonography (EDU) evaluation versus microdialysis in the early follow-up of adipocutaneous flaps, and propose an efficient postoperative monitoring protocol.

METHODS

We retrospectively assessed 68 consecutive DIEP flaps (50 patients) performed between January 2019 and March 2021. All flaps received standardized post-operative monitoring using clinical signs, EDU and microdialysis. Glucose and lactate concentrations were assessed using glucose <1 mmol/L and lactate >6 mmol/L as ischemic trend thresholds. We calculated Glucose/Lactate ratio as a new parameter for the assessment of flap viability.

RESULTS

Among all the 68 flaps, two flaps returned to the operative theater when a combination of unsatisfactory microdialysis values and clinical/EDU signs identified vascular impairment; only one developed total flap necrosis. Reoperation rate was 2.94% with an overall flap success rate of 98.53%. External Doppler ultrasonography had 100% sensitivity and 82% specificity, while microdialysis had 100% sensitivity and 100% specificity.

CONCLUSIONS

Microdialysis values proved flap viability sooner than external Doppler ultrasonography, making it an excellent tool for post-operative monitoring. With the appropriate thresholds for glucose and lactate concentrations, and glucose/lactate ratio used as a new parameter, it can help potentially avoiding unnecessary re-explorations, and reducing flap ischemia times.

Pancreatic Ischemia-Reperfusion Injury Following Endovascular Treatment of Symptomatic Celiac and Superior Mesenteric Artery Stenosis

CLINICAL IMPACT

With endovascular therapy becoming the first-line treatment for symptomatic chronic mesenteric ischemia, acute pancreatitis within the context of abdominal ischemia-reperfusion injury may be seen more often in cross-sectional imaging following this kind of interventions and should therefore be kept in mind by the reading physician.

Roxadustat promotes hypoxia-inducible factor-1α/vascular endothelial growth factor signalling to enhance random skin flap survival in rats

Random skin flaps have limited clinical application as a broad surgical reconstruction treatment because of distal necrosis. The prolyl hydroxylase domain-containing protein inhibitor roxadustat (RXD) enhances angiogenesis and reduces oxidative stress and inflammation. This study explored the function of RXD in the survival of random skin flaps. Thirty-six male Sprague-Dawley rats were randomly divided into low-dose RXD group (L-RXD group, 10 mg/kg/2 day), high-dose RXD group (H-RXD group, 25 mg/kg/2 day), and control group (1 mL of solvent, 1:9 DMSO:corn oil). The proportion of surviving flaps was determined on day 7 after surgery. Angiogenesis was assessed by lead oxide/gelatin angiography, and microcirculation blood perfusion was evaluated by laser Doppler flow imaging. Specimens in zone II were obtained, and the contents of superoxide dismutase (SOD) and malondialdehyde (MDA) were measured as indicators of oxidative stress. Histopathological status was evaluated with haematoxylin and eosin staining. The levels of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), and the inflammatory factors interleukin (IL)-1β, IL-6, and tumour necrosis factor-α (TNF-α) were detected by immunohistochemistry. RXD promoted flap survival and microcirculatory blood perfusion. Angiogenesis was detected distinctly in the experimental group. SOD activity increased and the MDA level decreased in the experimental group. Immunohistochemistry indicated that the expression levels of HIF-1α and VEGF were increased while the levels of IL-6, IL-1β, and TNF-α were decreased after RXD injection. RXD promoted random flap survival by reinforcing vascular hyperplasia and decreasing inflammation and ischaemia-reperfusion injury.

Cryopreservation of Animals and Cryonics: Current Technical Progress, Difficulties and Possible Research Directions

The basis of cryonics or medical cryopreservation is to safely store a legally dead subject until a time in the future when technology and medicine will permit reanimation after eliminating the disease or cause of death. Death has been debunked as an event occurring after cardiac arrest to a process where interjecting its progression can allow for reversal when feasible. Cryonics technology artificially halts further damages and injury by restoring respiration and blood circulation, and rapidly reducing temperature. The body can then be preserved at this extremely low temperature until the need for reanimation. Presently, the area has attracted numerous scientific contributions and advancement but the practice is still flooded with challenges. This paper presents the current progression in cryonics research. We also discuss obstacles to success in the field, and identify the possible solutions and future research directions.

Inguinal Hernia in Nonhuman Primates: From Asymptomatic to Life-Threatening Events

In this study, a review of available data and literature on the epidemiology and anamnesis of inguinal hernias in nonhuman primates, as well as on their clinical evaluation and surgical management, was conducted. Inguinal hernias are assumed to be relatively common in male nonhuman primates. Clinical signs are usually limited to a visible or palpable mass in the groin region without pain or systemic illness. Most hernias contain omentum. Careful monitoring is an acceptable treatment option for those animals. Size, the danger of incarceration, and the presence of strangulation are important factors when considering surgical repair. A strangulated inguinal hernia is an emergency, requiring prompt surgery to avoid tissue necrosis and death. Imaging techniques, as well as computed tomography (CT), ultrasonography, and magnetic resonance imaging (MRI), provide information about the anatomical characteristics of the suspected region, allowing for a diagnosis and treatment. An inguinal hernia repair can be performed with either open surgery or laparoscopic surgery. The hernia repair can be achieved by mesh or suture. Decisions regarding which repair technique to use depend on the surgeon′s skill level and preference. Complication and recurrence rates are generally low. The most common postsurgical complication is a recurrence of the hernia. Contraceptive measures are not indicated in breeders, as there is no known hereditary component, and the presence of hernia does not appear to affect fertility, nor does it predispose to occurrence, recurrence, or incarceration.

The effect of taxifolin on experimental testicular ischaemia reperfusion injury in rats. A biochemical and histopathological analysis

OBJECTIVES

The aim of the study is to investigate the protective effect of taxifolin (3,5,7,3,4-pentahydroxy flavanone), a strong antioxidant, against testicular I/R injury in rats biochemically and histopathologically.

MATERIALS AND METHODS

50mg/kg taxifolin was administered to taxifolin+testicular torsion-detorsion (TTTD, n-10) group of Albino Wistar male rats by oral gavage. Distilled water .5ml as a solvent was administered to testicular torsion-detorsion (TTD, n-10) and Healthy Control (SG, n-10) groups using the same method. An hour after the administration of taxifolin and distilled water, anaesthesia (ketamine 60mg/kg) was administered to all animal groups. TTD and TTTD group animals were subjected to testicular torsion at 720 degrees for four hours during anaesthesia. At the end of this period, testicular detorsion was applied and perfusion was allowed for four hours. Sham operation was applied to SG group.

RESULTS

Our biochemical experiment results showed that the amount of malondialdehyde (MDA) in testicular tissue of TTD group presented a significant increase compared to SG and TTTD groups whereas total glutathione (tGSH) and superoxide dismutase (SOD) levels decreased. In addition, while TTD group presented severe histopathological damage in germinal epithelium cell and seminiferous tubule, mild damage was observed in TTTD group.

CONCLUSIONS

The results of our experiment indicate that taxifolin could be useful in the treatment of testicular I/R damage.

The effects of amantadine on lung tissue in lower limb ischemia/reperfusion injury model in rats

Background

This study aims to evaluate the effect of amantadine on lung tissue of after lower limb ischemia/reperfusion injury in rats.

Methods

A total of 24 Wistar rats were divided into four equal groups including six rats in each: sham group (Group S), amantadine group (Group A), ischemia/reperfusion group (Group I/R), and ischemia/reperfusion + amantadine group (Group I/R-A). All groups underwent a midline abdominal incision. In Groups I/R and I/R-A, the infrarenal abdominal aorta was clamped for 120 min and, then, reperfused for 120 min after removal of the clamp. Amantadine hydrochloride 45 mg/kg was administered intraperitoneally to the rats of Groups A and Group I/R-A 15 min before surgery. At the end of reperfusion period (240 min), all rats were sacrificed, and their lung tissues were obtained. Lung tissue catalase and superoxide dismutase activities and glutathione S-transferase and malondialdehyde levels were analyzed. Lung tissues were examined histopathologically.

Results

Catalase activity was lower in Groups A, I/R, and I/R-A compared to Group S. Superoxide dismutase activity was higher in Group I/R than Group S. Superoxide dismutase activity in Groups I/R-A and A decreased, compared to Groups S and I/R. Glutathione S-transferase levels decreased in Groups I/R and A, compared to Group S. Glutathione S-transferase levels in Group I/R-A were higher than Groups I/R and A. The highest level of malondialdehyde was found in Group I/R and the lowest level was found in Group I/R-A. According to histopathological examination, infiltration scores were significantly lower in Group S than Groups I/R and I/R-A (p=0.009 and p=0.011, respectively). The alveolar wall thickening scores in Group I/R were also significantly higher than Groups S and Group A (p=0.001 and p=0.001, respectively).

Conclusion

Lung tissue can be affected histopathologically by ischemia/ reperfusion injury and this injury can be reversed by amantadine administration.

Effects of Ischemic Preconditioning and C1 Esterase Inhibitor Administration following Ischemia-Reperfusion Injury in a Rat Skin Flap Model

BACKGROUND

 Ischemia-reperfusion (I/R) injury is a serious condition that can affect the success rate of microsurgical reconstructions of ischemic amputated limbs and complex tissue defects requiring free tissue transfers. The purpose of this study was to evaluate the effects of ischemic preconditioning (IPC) and C1 esterase inhibitor (C1-Inh) intravenous administration following I/R injury in a rat skin flap model.

METHODS

 Superficial caudal epigastric skin flaps (3 cm × 7 cm) were performed on 50 Wistar rats that were randomly divided into five groups. Ischemia was not induced in the control group. All other flaps underwent 8 hours of ischemia prior to revascularization: I/R control group (8-hour ischemia), IPC group (preconditioning protocol + 8-hour ischemia), C1-Inh group (8-hour ischemia + C1-Inh), and IPC + C1-Inh group (preconditioning protocol + 8-hour ischemia + C1-Inh). Survival areas were macroscopically assessed after 1 week of surgery, and histopathological and biochemical evaluations were also measured.

RESULTS

 There were no significant differences in flap survival between the treatment groups that were suffering 8 hours of ischemia and the control group. A significant increase in neovascularization and lower edema formation were observed in the IPC group compared with that in the I/R group. Biochemical parameters did not show any significant differences.

CONCLUSION

 Intravenous administration of C1-Inh did not significantly modulate I/R-related damage in this experimental model, but further research is needed. On the other hand, IPC reduces tissue damage and improves neovascularization, confirming its potential protective effects in skin flaps following I/R injury.

Modulation of Nitric Oxide Bioavailability Attenuates Ischemia-Reperfusion Injury in Type II Diabetes

BACKGROUND

Diabetes mellitus increases the susceptibility of free tissue transplantations to ischemia-reperfusion injury. The aim of this study was to enhance nitric oxide (NO) bioavailability through exogenous NO synthase and the substrate L-arginine to attenuate ischemia reperfusion-induced alterations in a type 2 diabetes rodent model.

MATERIAL AND METHODS

Sixty-four Wistar rats were divided into 8 experimental groups. Type 2 diabetes was established over 3 months with a combination of a high-fat diet and streptozotocin. A vascular pedicle isolated rat skin flap model that underwent 3 h of ischemia was used. At 30 min before ischemia, normal saline, endothelial NOSs (eNOSs), inducible NOSs, neuronal NOSs (1 and 2 IU), and L-arginine (50 mg/kg body weight) were administered by intravenous infusion alone or in combination. Ischemia-reperfusion-induced alterations were measured 5 days after the operation.

RESULTS

The three isoforms of NOS significantly increased the flap vitality rate (VR) between 20% and 28% as compared to the control group (3%). Sole L-arginine administration increased the VR to 33%. The combination of L-arginine with NOS resulted in a further increase in flap VRs (39%-50%). Best results were achieved with the combination of eNOS and L-arginine (50%). An increase in enzyme dosage led to decreased VRs in all NOS isoforms alone and even in combination with L-arginine.

CONCLUSION

Modulation of NO bioavailability through the exogenous application of NOSs and L-arginine significantly attenuated ischemia-reperfusion-induced alterations in a type 2 diabetic skin flap rat model. The combination of enzyme and substrate result in the highest VRs. Higher enzyme dosage seems to be less effective. This pharmacological preconditioning could be an easy and effective interventional strategy to support the conversion of L-arginine to NO in ischemic and in type 2 diabetic conditions.

Pharmaceutical Preconditioning With Nitric Oxide Synthase and L-Arginine in Ischemic Tissues

BACKGROUND

Nitric oxide (NO) is a multifunctional signaling molecule involved in regulating vascular tone and tissue oxygenation. It is also an important cytoprotective agent against ischemia-reperfusion injury (IRI). Enhancing NO bioavailability via exogenous NO synthases (NOSs) and L-arginine promotes conversation to NO, circumventing the problem of nonfunctioning NOSs under hypoxic and acidic conditions. In this study, the authors evaluated the therapeutic efficacy of neuronal, inducible, and endothelial NOS and L-arginine on reperfusion-induced skin flap alterations.

METHODS

The vascular pedicle isolated rat skin flap model was used and underwent 3 hours of ischemia. At 30 minutes before ischemia, normal saline, endothelial-, inducible-, and neuronal NOSs (1/2 IU) and L-arginine (100 mg/kg body weight) were administered by means of intravenous infusion. The IRI-induced alterations were measured 5 days after the operation.

RESULTS

The 3 isoforms of NOS increased the flap vitality rate (VR) from 10% to 23% compared with the control group. L-Arginine treatment also increased the VR by approximately 15%. The combination of L-arginine with NOS resulted in even higher flap VRs. The best results could be achieved with the combination of endothelial NOS (2 IU) and L-arginine.

CONCLUSIONS

Modulation of NO bioavailability via exogenous application of NOSs and L-arginine significantly improved VRs in a skin flap rat model. This pharmacologic preconditioning has the potential to attenuate IRI-induced alterations in skin flaps.

Rip 1-dependent endothelial necroptosis participates in ischemia-reperfusion injury of mouse flap

BACKGROUND

Ischemia reperfusion injury plays an important role in free flap necrosis. However, the detailed mechanism is not clear, and effective methods for improving the survival rate of skin flap are still lacking.

OBJECTIVE

To investigate the regulation and functional link between necroptosis and ischemia-reperfusion injury of mouse flap.

METHODS

We established a mouse ischemia-reperfusion injury flap model and a cell Oxygen Glucose Deprivation (OGD) model intervened with Necrostatin-1. The mouse flap tissues were harvested in vivo for histological immunofluorescence analysis and western blotting analyses. The HUVECs cells with various treatments in vitro were assessed by using Transwell assay, tube formation assay, cell counting kit-8 analysis and flow cytometry. A Rip3-knockout cell line and a TNFR1-knockout cell line were generated from HUVEC cells using the CRISPR-Cas9 technology and were subsequently used to explore the related mechanisms.

RESULTS

The expression of p-Rip3 is positive in both mouse and cell culture models. When necroptosis is completely or partially inhibited in vivo, damaged tissues are repaired with better efficiency. The cells treated with Necrostatin-1 in vitro exhibit faster migration, proliferation and better tube formation. Deficiency of TNFR1 can block the necroptosis pathway by blocking the phosphorylation of Rip3 in HUVEC OGD/ROG model. Meanwhile, the levels of APJ, HIF-1α, and VEGF are reduced when necroptosis is inhibited by Necrostatin-1.

CONCLUSION

TNFR1 mediates Rip1/Rip3 in ischemia-reperfusion injury. Inhibition of necroptosis attenuates the ischemia-reperfusion injury of flap and may enhance hypoxic tolerance of HUVECs and vascular homeostasis through regulation of the HIF-1α signaling pathways.

Protective effects of HO-1 pathway on lung injury subsequent to limb ischemia reperfusion

Limb ischemia reperfusion (LIR) can activate endogenous cytoprotective mechanisms by generating specific proteins against reperfusion injury in remote organs. The present study investigated the roles of heme oxygenase-1 (HO-1) pathway and the molecular mechanisms underlying the regulation of this pathway on lung injury following LIR. LIR was induced by ischemia for 4 hours followed by reperfusion for 6 hours (LIR 6 hours) or 16 hours (LIR 16 hours) in male Sprague-Dawley rats. HO-1 inducer cobalt protoporphyrin (Copp) or HO-1 inhibitor zinc protoporphyrin (Znpp) was intravenously injected 24 hours before ischemia. The animals were randomly divided into nine groups, including normal control, LIR 6 hours, LIR 16 hours, Copp, Copp + LIR 6 hours, Copp + LIR 16 hours, and Znpp, Znpp+ LIR 6 hours, and Znpp + LIR 16 hours groups (each group included four samples). Lung injury was examined through histopathology. Quantitative real-time PCR, immunohistochemistry and Western blot were applied to detect the mRNA and protein levels of HO-1, Nrf2, and Bach1. Our study showed that LIR induced Nrf2 upregulation but Bach1 downregulation to promote HO-1 expression in lung tissues. Activation of HO-1 pathway by Copp potentially enhanced Nrf2 expression but inhibition of the pathway by Znpp promoted Bach1 expression. Inducer of HO-1 pathway, Copp injection improved the lung injury. Nevertheless, Znpp injection aggravated the lung injury following LIR. Our findings suggested that activated HO-1 pathway might exert protective effects on the lung injury following LIR.

Graft-implanted, enzyme responsive, tacrolimus-eluting hydrogel enables long-term survival of orthotopic porcine limb vascularized composite allografts: A proof of concept study

Background

Currently, patients receiving vascularized composite allotransplantation (VCA) grafts must take long-term systemic immunosuppressive therapy to prevent immunologic rejection. The morbidity and mortality associated with these medications is the single greatest barrier to more patients being able to receive these life-enhancing transplants. In contrast to solid organs, VCA, exemplified by hand or face transplants, allow visual diagnosis of clinical acute rejection (AR), directed biopsy and targeted graft therapies. Local immunosuppression in VCA could reduce systemic drug exposure and limit adverse effects. This proof of concept study evaluated, in a large animal forelimb VCA model, the efficacy and tolerability of a novel graft-implanted enzyme-responsive, tacrolimus (TAC)—eluting hydrogel platform, in achieving long-term graft survival.

Methods

Orthotopic forelimb VCA were performed in single haplotype mismatched mini-swine. Controls (n = 2) received no treatment. Two groups received TAC hydrogel: high dose (n = 4, 91 mg TAC) and low dose (n = 4, 49 mg TAC). The goal was to find a dose that was tolerable and resulted in long-term graft survival. Limbs were evaluated for clinical and histopathological signs of AR. TAC levels were measured in serial blood and skin tissue samples. Tolerability of the dose was evaluated by monitoring animal feeding behavior and weight.

Results

Control limbs underwent Banff Grade IV AR by post-operative day six. Low dose TAC hydrogel treatment resulted in long-term graft survival time to onset of Grade IV AR ranging from 56 days to 93 days. High dose TAC hydrogel also resulted in long-term graft survival (24 to 42 days), but was not well tolerated.

Conclusion

Graft-implanted TAC-loaded hydrogel delays the onset of Grade IV AR of mismatched porcine forelimb VCA grafts, resulting in long term graft survival and demonstrates dose-dependent tolerability.

Voluntary running protects against neuromuscular dysfunction following hindlimb ischemia-reperfusion in mice

Ischemia-reperfusion (IR) due to temporary restriction of blood flow causes tissue/organ damages under various disease conditions, including stroke, myocardial infarction, trauma, and orthopedic surgery. In the limbs, IR injury to motor nerves and muscle fibers causes reduced mobility and quality of life. Endurance exercise training has been shown to increase tissue resistance to numerous pathological insults. To elucidate the impact of endurance exercise training on IR injury in skeletal muscle, sedentary and exercise-trained mice (5 wk of voluntary running) were subjected to ischemia by unilateral application of a rubber band tourniquet above the femur for 1 h, followed by reperfusion. IR caused significant muscle injury and denervation at neuromuscular junction (NMJ) as early as 3 h after tourniquet release as well as depressed muscle strength and neuromuscular transmission in sedentary mice. Despite similar degrees of muscle atrophy and oxidative stress, exercise-trained mice had significantly reduced muscle injury and denervation at NMJ with improved regeneration and functional recovery following IR. Together, these data suggest that endurance exercise training preserves motor nerve and myofiber structure and function from IR injury and promote functional regeneration. NEW & NOTEWORTHY This work provides the first evidence that preemptive voluntary wheel running reduces neuromuscular dysfunction following ischemia-reperfusion injury in skeletal muscle. These findings may alter clinical practices in which a tourniquet is used to modulate blood flow.

Effects of SB202190 on expression levels of IL-6 and NF-κB in flap ischemia-reperfusion injury

The aim of the current study was to investigate the effect of SB202190, a specific inhibitor of p38 MAPK signaling pathway, on the expression levels of IL-6 and NF-κB in flap ischemia-reperfusion injury. Healthy Sprague-Dawley rats were randomly divided into four groups of 12 each. For the ischemia-reperfusion group, the flap was constructed and then sutured after 8 h of ischemia. For the saline group, rats were intraperitoneally infused with saline at regular intervals after flap ischemia-reperfusion. For the inhibitor group, rats were intraperitoneally infused with SB202190 at regular intervals after flap ischemia-reperfusion. For the control group, the flap was constructed and then sutured immediately. The flap survival rate of each group was measured after 7 days. The concentration of IL-6 in serum was measured by ELISA kit. The mRNA and protein expression levels of IL-6 and NF-κB in the flap were measured using RT-PCR and western blot analysis, respectively. In the ischemia-reperfusion group and the saline group, the flap survival rates were much lower than that in the control group (P<0.05). By contrast, the mRNA and protein expression levels of IL-6 and NF-κB in the flap and the concentration of IL-6 in serum were much higher (P<0.05). In the inhibitor group, the flap survival rate was significantly higher than those in the ischemia-reperfusion and saline groups (P<0.05). By contrast, the concentration of IL-6 in serum and the mRNA and protein expression levels of NF-κB and IL-6 in the flap were significantly decreased (P<0.05). The results show that, SB202190 played a role in the protection of the flap by reducing the inflammatory response in flap ischemia-reperfusion injury.

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.

A Study on the Effects of the Use of Propofol in Experimental Model Inferior Epigastric Island Flap on Ischemia-Reperfusion Injury

Problems concerning vascular blood flow are the most frequently encountered ones after flap applications. The flap tissue starts to develop ischemia in patients with a vascular blood flow insufficiency. And reperfusion starts in those patients in whom the ischemia is temporary, triggering an ischemia-reperfusion injury depending on the duration of the ischemia. The aim of this study was to evaluate the effect of propofol, which is an anesthetic agent known to have an antioxidant effect and a free radical scavenging feature on the ischemia-reperfusion injury created on an experimental epigastric island flap.Thirty Sprague-Dawley rats were used in the study. The rats were divided into 3 groups of 10 rats each. Inferior epigastric artery-based abdominal flaps were prepared in all the groups. In group 1 (sham), the flap was elevated but no ischemia was applied. In groups 2 (control) and 3 (propofol), the flap was exposed to ischemia for 2 hours after it was elevated. All the rats were sacrificed and biochemical and histopathological assessments were made on the tissue samples taken on the 14th day. As a result of a comparison between the groups, the flap viability rates and the superoxide dismutase, total antioxidant capacity, and catalase values were found to be significantly higher (P < 0.001) in the propofol group while the malondialdehyde and total oxidative stress values were lower (P < 0.001). Based on the data obtained from the present study, the use of propofol was observed to have a protective effect against ischemia-reperfusion injuries in flap surgeries.

Prolonged Cold Ischemia Time Results in Local and Remote Organ Dysfunction in a Murine Model of Vascularized Composite Transplantation

Vascularized composite allotransplantation (VCA) is a viable reconstructive option for complex tissue defects. Although grafts with a large muscular component may be uniquely susceptible to ischemia-reperfusion (I/R) syndrome, the safe cold ischemia time in VCA has not been established. We investigated the effects of cold ischemia on innate immune response and recipient survival in a murine orthotopic hindlimb transplantation model. Surprisingly, mice receiving grafts exposed to 6 h or longer of cold storage demonstrated reduced survival and massive elevations in serum creatinine, blood urea nitrogen, and creatine kinase, compared with 1 h of cold storage recipients. This was accompanied by progressive increase in macrophage and neutrophil cell infiltration in muscle biopsy specimens, altered platelet endothelial cell adhesion molecule-1 expression, and ultimate renal injury. Multiplex immunoassay analysis identified 21 cytokines in serum and 18 cytokines in muscle biopsy specimens that are likely essential in the complex response to I/R-triggered injury in VCA. In conclusion, this study, in a mouse model of orthotopic hindlimb transplantation, is the first to document that prolonged cold ischemia triggers progressive I/R injury with vascular endothelial damage and may lead to irrecoverable local and remote organ damage. These experimental findings are important in guiding future therapies for human VCA recipients.

Chlorogenic Acid Enhances Abdominal Skin Flap Survival Based on Epigastric Artery in Nondiabetic and Diabetic Rats

Previous studies showed that chlorogenic acid (CGA) accelerates wound healing via its antioxidant activity. We aimed to investigate the effect of CGA in an experimental epigastric abdominal skin flap model in nondiabetic and diabetic rats. Rats were firstly divided into 2 groups: nondiabetic and diabetic. Diabetes was induced by streptozotocin. Then, 4 subgroups were created for each group: vehicle as well as 0.2 mg/0.5 mL, 1 mg/0.5 mL, and 5 mg/0.5 mL CGA treatments. Right epigastric artery-based abdominal skin flaps were elevated and sutured back into their original position. Chlorogenic acid or vehicle was injected once into the femoral arteries by leaving the epigastric artery as the single artery feeding the flaps during the injection. On postoperative day 7, flap survivals were evaluated, and the rats were killed. Distal flap tissues were collected for histopathological and biochemical assays. Chlorogenic acid showed greater flap survival in both nondiabetic and diabetic rats. Capillary density was increased, and necrosis was reduced in the CGA-treated rats. Chlorogenic acid decreased malondialdehyde levels as well as increased reduced glutathione and superoxide dismutase levels in the flap tissues. This study showed that CGA significantly improved flap survival by its antioxidant activities with intra-arterial local injections.

Ischaemia-reperfusion injury and hyperbaric oxygen pathways: a review of cellular mechanisms

Ischaemia-induced tissue injury has wide-ranging clinical implications including myocardial infarction, stroke, compartment syndrome, ischaemic renal failure and replantation and revascularization. However, the restoration of blood flow produces a 'second hit' phenomenon, the effect of which is greater than the initial ischaemic event and characterizes ischaemia-reperfusion (IR) injury. Some examples of potential settings of IR injury include: following thrombolytic therapy for stroke, invasive cardiovascular procedures, solid organ transplantation, and major trauma resuscitation. Pathophysiological events of IR injury are the result of reactive oxygen species (ROS) production, microvascular vasoconstriction, and ultimately endothelial cell-neutrophil adhesion with subsequent neutrophil infiltration of the affected tissue. Initially thought to increase the amount of free radical oxygen in the system, hyperbaric oxygen (HBO) has demonstrated a protective effect on tissues by influencing the same mechanisms responsible for IR injury. Consequently, HBO has tremendous therapeutic value. We review the biochemical mechanisms of ischaemia-reperfusion injury and the effects of HBO following ischaemia-reperfusion.

Efficacy of the postoperative management after microsurgical free tissue transfer

INTRODUCTION

The physical and medical postoperative measures after free flap reconstruction vary substantially between surgical units. The objective of this review was to identify the postoperative measures which proved a significant positive effect on free flap survival.

METHOD

A review was conducted in the MEDLINE database on the English and French literature.

RESULTS AND DISCUSSION

Twenty-eight articles were retained. A meta-analysis of 4984 patients who were given antithrombotics (viz. antiplatelets and anticoagulants) postoperatively found that these treatments were of no significant benefit to free flap survival and increased the risk of postoperative hematoma. Postoperative transfusions did not favor free flap survival and were associated with a higher incidence of medical complications. Preoperative anemia was a risk factor for free flap failure. Blood pressure control, vasodilators, antioxidants, corticotherapy, oxygen therapy, and prolonged immobilization were of no proven benefit.

CONCLUSION

No postoperative therapy, whether drug-based or not, has been shown to have a significant positive effect on free flap survival.

Does Remote Ischaemic Preconditioning Protect Kidney and Cardiomyocytes After Coronary Revascularization? A Double Blind Controlled Clinical Trial

OBJECTIVE

To investigate efficacy of remote ischaemic preconditioning on reducing kidney injury and myocardial damage after coronary artery bypass grafting surgery (CABG).

BACKGROUND

Ischaemic preconditioning of a remote organ reduces ischaemia-reperfusion injury of kidney and myocardium after CABG.

METHOD

To reduce myocardial damage and kidney injury by applying Remote Ischaemic Preconditioning we recruited 100 consecutive patients undergoing elective coronary artery bypass grafting surgery. We applied three cycles of lower limb tourniquet, inflated its cuff for 5 minutes in study group or left un-inflated (sham or control group) before the procedure. The primary outcome was serum creatinine, creatinine clearance and troponin-I Levels at time 0, 6, 12, 24 and 48 h. Secondary outcomes were serum C-reactive protein, inotrope score, ventilation time and ICU stay. Data's were analyzed by MedCalc (MedCalc Software bvba, Acacialaan, Belgium). We compared the two group by student t test, chi-square and Mann-Whitney tests.

RESULTS

The two groups were not statistically different in terms of age, gender, smoking habits, drug use, hypertension, hyperlipidemia and diabetes mellitus. This study showed a higher CRP level in study group comparing with control group (P=0.003), creatinine clearance was slightly higher in study group specially 24 h after procedure but was not statistically significant (p=0.11). Troponin-I level was significantly lower in study group (p=0.001).

CONCLUSION

This study showed a lower Troponin-I level in study group which suggest a cardio-myocyte protective function of RIPC. It also showed slightly lower Creatinine clearance in control group, gap between two group increases significantly 24 hours after procedure which may suggest a potential kidney protection by RIPC. Serum CRP level was higher in study group. A multi-center randomized controlled trial with a longer time for creatinine clearance measurement may show the potential effectiveness of this non-invasive inexpensive intervention on reducing kidney injury after CABG.

Protective effect of telomerase-based 16-mer peptide vaccine (GV1001) on inferior epigastric island skin flap survivability in ischaemia-reperfusion injury rat model

BACKGROUND

Ischaemia-reperfusion injury (IRI) results in oxidative damage and a profound inflammatory reaction, leading to cell death. GV 1001 is a telomerase-based 16-mer peptide vaccine developed against cancer. However, it has also been reported to possess antioxidant and anti-inflammatory properties. The aim of this study was to determine if GV 1001 can reduce the negative effects caused by IRI in a rat skin flap model owing to its anti-oxidant and anti-inflammatory properties.

MATERIALS AND METHODS

In order to evaluate the effect of GV 1001, 5 × 5 cm² inferior epigastric artery based island skin flaps were dissected in 39 8-week-old Sprague-Dawley rats weighing 220-270 g. The rats were divided into three groups: (I) non-ischaemic group; (II) IRI with saline; and (III) IRI with 10 mg GV 1001 treatment. Drugs were administered intra-muscularly directly before and after ischaemia. Flap survival area, neutrophil infiltration, cytokine levels (interleukin [IL]-1, IL-6, and tumour necrosis factor-α), malondialdehyde (MDA) level, and superoxide dismutase (SOD) activity were measured. Flap survivability was analysed at 7 days after surgery.

RESULTS

Flap survival area was significantly larger in group III than in group II. Cytokine release level was also significantly lower in group III. Neutrophil infiltration grade, MDA level, and SOD activity slightly decreased in Group III; however, the changes were not statistically significant.

CONCLUSION

These results imply that GV 1001 exerts a protective effect against IRI through antioxidant effects, reducing reactive oxygen species, and suppressing the inflammatory cascade.

Early risk prognosis of free-flap transplant failure by quantitation of the macrophage colony-stimulating factor in patient plasma using 2-dimensional liquid-chromatography multiple reaction monitoring-mass spectrometry

Although great success of microvascular free-flap transplantation surgery has been achieved in recent years, between 1.5% and 15% of flaps are still lost due to vascular occlusion. The clinical challenge remains to salvage a transplant in the case of vascular complications. Since flap loss is devastating for the patient, it is of utmost importance to detect signs of complications or of conspicuities as soon as possible. Rescue success rates highly depend on early revision. In this study, we collected blood samples during transplantation surgery from either the contributory artery or the effluent vein of the flap and applied a targeted mass spectrometry-based approach to quantify 24 acute phase proteins, cytokines, and growth factors in 63 plasma samples from 21 hospitalized patients, generating a dataset with 9450 protein concentration values. Biostatistical analyses of the targeted plasma protein concentrations in all 63 plasma samples showed that venous concentrations of macrophage colony-stimulating factor (M-CSF) provided the highest accuracy for discriminating patients with either clinical conspicuities or complications from control individuals. Using 21.33 ng/mL of M-CSF as the diagnostic threshold when analyzing venous blood plasma samples, the assay obtained a sensitivity of 0.93 and a specificity of 0.85 with an area under the curve value of 0.902 in the receiver operating characteristic analysis. Overall, our results indicate that M-CSF is a potential molecular marker for early risk prognosis of free-flap transplant failure.

Therapeutic application of extracellular vesicles in acute and chronic renal injury

A new cell-to-cell communication system was discovered in the 1990s, which involves the release of vesicles into the extracellular space. These vesicles shuttle bioactive particles, including proteins, mRNA, miRNA, metabolites, etc. This particular communication has been conserved throughout evolution, which explains why most cell types are capable of producing vesicles. Extracellular vesicles (EVs) are involved in the regulation of different physiological processes, as well as in the development and progression of several diseases. EVs have been widely studied over recent years, especially those produced by embryonic and adult stem cells, blood cells, immune system and nervous system cells, as well as tumour cells. EV analysis from bodily fluids has been used as a diagnostic tool for cancer and recently for different renal diseases. However, this review analyses the importance of EVs generated by stem cells, their function and possible clinical application in renal diseases and kidney transplantation.

Effect of dexmedetomidine on acute lung injury in experimental ischemia-reperfusion model

PURPOSE

Ischemia-reperfusion injury is one of the consequences of tourniquet application for extremity surgery. The aim of the study was to establish the effect of dexmedetomidine on the acute lung injury following lower extremity experimental ischemia-reperfusion model in rats.

METHODS

Twenty-eight Wistar-Albino breed Rats were recruited after Ethics Committee approval and allocated into 4 groups, each with 7 subjects. Group 1 (SHAM) received only anesthesia. Group 2 (IR) had experienced 3h of ischemia and 3h of reperfusion using left lower extremity tourniquet after anesthesia application. Groups 3 (D-50) and 4 (D-100) had undergone the same procedures as in the Group 2, except for receiving 50 and 100mg·kg^-1, respectively, dexmedetomidine intraperitoneally 1h before the tourniquet release. Blood samples were obtained for the analysis of tumor necrosing factor-α and interleukin-6. Pulmonary tissue samples were obtained for histological analysis.

RESULTS

No significant difference regarding blood tumor necrosing factor-α and interleukin-6 values was found among the groups, whereas pulmonary tissue injury scores revealed significant difference. Histological scores obtained from the Group 2 were significantly higher from those in the Groups 1, 3 and 4 with p-values 0.001 for each comparison. Moreover, Group 1 scores were found to be significantly lower than those in the Groups 3 and 4 with p-values 0.001 and 0.011, respectively. No significant difference was observed between the Groups 3 and 4.

CONCLUSION

Dexmedetomidine is effective in reduction of the experimental ischemia-reperfusion induced pulmonary tissue injury in rats, formed by extremity tourniquet application.

Hydroxylated chalcones with dual properties: Xanthine oxidase inhibitors and radical scavengers

In this study, we evaluated the abilities of a series of chalcones to inhibit the activity of the enzyme xanthine oxidase (XO) and to scavenge radicals. 20 mono- and polyhydroxylated chalcone derivatives were synthesized by Claisen-Schmidt condensation reactions and then tested for inhibitory potency against XO, a known generator of reactive oxygen species (ROS). In parallel, the ability of the synthesized chalcones to scavenge a stable radical was determined. Structure-activity relationship analysis in conjunction with molecular docking indicated that the most active XO inhibitors carried a minimum of three hydroxyl groups. Moreover, the most effective radical scavengers had two neighboring hydroxyl groups on at least one of the two phenyl rings. Since it has been proposed previously that XO inhibition and radical scavenging could be useful properties for reduction of ROS-levels in tissue, we determined the chalcones' effects to rescue neurons subjected to ROS-induced stress created by the addition of β-amyloid peptide. Best protection was provided by chalcones that combined good inhibitory potency with high radical scavenging ability in a single molecule, an observation that points to a potential therapeutic value of this compound class.

Mass spectrometric characterization of limited proteolysis activity in human plasma samples under mild acidic conditions

We developed a limited proteolysis assay for estimating dynamics in plasma-borne protease activities using MALDI ToF MS analysis as readout. A highly specific limited proteolysis activity was elicited in human plasma by shifting the pH to 6. Mass spectrometry showed that two singly charged ion signals at m/z 2753.44 and m/z 2937.56 significantly increased in abundance under mild acidic conditions as a function of incubation time. For proving that a provoked proteolytic activity in mild acidic solution caused the appearance of the observed peptides, control measurements were performed (i) with pepstatin as protease inhibitor, (ii) with heat-denatured samples, (iii) at pH 1.7, and (iv) at pH 7.5. Mass spectrometric fragmentation analysis showed that the observed peptides encompass the amino acid sequences 1-24 and 1-26 from the N-terminus of human serum albumin. Investigations on peptidase specificities suggest that the two best candidates for the observed serum albumin cleavages are cathepsin D and E. Reproducibility, robustness, and sensitivity prove the potential of the developed limited proteolysis assay to become of clinical importance for estimating dynamics of plasma-borne proteases with respect to associated pathophysiological tissue conditions.

Echinochrome a increases mitochondrial mass and function by modulating mitochondrial biogenesis regulatory genes

Echinochrome A (Ech A) is a natural pigment from sea urchins that has been reported to have antioxidant properties and a cardio protective effect against ischemia reperfusion injury. In this study, we ascertained whether Ech A enhances the mitochondrial biogenesis and oxidative phosphorylation in rat cardio myoblast H9c2 cells. To study the effects of Ech A on mitochondrial biogenesis, we measured mitochondrial mass, level of oxidative phosphorylation, and mitochondrial biogenesis regulatory gene expression. Ech A treatment did not induce cytotoxicity. However, Ech A treatment enhanced oxygen consumption rate and mitochondrial ATP level. Likewise, Ech A treatment increased mitochondrial contents in H9c2 cells. Furthermore, Ech A treatment up-regulated biogenesis of regulatory transcription genes, including proliferator-activated receptor gamma co-activator (PGC)-1α, estrogen-related receptor (ERR)-α, peroxisome proliferator-activator receptor (PPAR)-γ, and nuclear respiratory factor (NRF)-1 and such mitochondrial transcription regulatory genes as mitochondrial transcriptional factor A (TFAM), mitochondrial transcription factor B2 (TFB2M), mitochondrial DNA direct polymerase (POLMRT), single strand binding protein (SSBP) and Tu translation elongation factor (TUFM). In conclusion, these data suggest that Ech A is a potentiated marine drug which enhances mitochondrial biogenesis.

Pharmacologic overview of systemic chlorogenic acid therapy on experimental wound healing

Chlorogenic acid (CGA) is a well-known natural antioxidant in human diet. To understand the effects of CGA on wound healing by enhancing antioxidant defense in the body, the present study sought to investigate the potential role of systemic CGA therapy on wound healing and oxidative stress markers of the skin. We also aimed to understand whether chronic CGA treatment has side effects on pivotal organs or rat bone marrow during therapy. Full-thickness experimental wounds were created on the backs of rats. CGA (25, 50, 100, 200 mg/kg) or vehicle was administered intraperitoneally for 15 days. All rats were sacrificed on the 16th day. Biochemical, histopathological, and immunohistochemical examinations were performed. Possible side effects were also investigated. The results suggested that CGA accelerated wound healing in a dose-dependent manner. CGA enhanced hydroxyproline content, decreased malondialdehyde and nitric oxide levels. and elevated reduced glutathione, superoxide dismutase, and catalase levels in wound tissues. Epithelialization, angiogenesis, fibroblast proliferation, and collagen formation increased by CGA while polymorph nuclear leukocytes infiltration decreased. CGA modulated matrix metalloproteinase-9 and tissue inhibitor-2 expression in biopsies. Otherwise, high dose of CGA increased lipid peroxidation of liver and kidney without affecting the heart and muscle samples. Chronic CGA increased micronuclei formation and induced cytotoxicity in the bone marrow. In conclusion, systemic CGA has beneficial effects in improving wound repair. Antioxidant, free radical scavenger, angiogenesis, and anti-inflammatory effects of CGA may ameliorate wound healing. High dose of CGA may induce side effects. In light of these observations, CGA supplementation or dietary CGA may have benefit on wound healing.

Enhancing Nitric Oxide Bioavailability via Exogen Nitric Oxide Synthase and L-Arginine Attenuates Ischemia-Reperfusion-Induced Microcirculatory Alterations

BACKGROUND

Nitric oxide (NO) is an important cytoprotective agent against ischemia and reperfusion injury (IRI). Enhancing NO bioavailability via exogen NO synthases (NOSs) and L-arginine promotes conversation to NO, circumventing the problem of nonfunctioning NOSs under hypoxic and acidic conditions. In this study, the authors evaluated the therapeutic efficacy of endothelial, inducible and neuronal NOS, and L-arginine on reperfusion-induced microcirculatory alterations and hemodynamic adverse effects in the microvasculature of skeletal muscle.

METHODS

Vascular pedicle isolated rat cremaster model was used that underwent 2 hours of warm ischemia followed by 1 hour of reperfusion. At 30 minutes before ischemia, normal saline (control group with/without ischemia), endothelial-, inducible-, and neuronal NOSs (2 IE) and L-arginine (50 mg/kg BW) were administered systemically (IV). Ischemia-reperfusion-induced microcirculatory alterations were measured after 1 hour of reperfusion. Mean arterial blood pressure and heart frequency were measured throughout the experiment to determine hemodynamic adverse effects.

RESULTS

The isoforms of NOSs and L-arginine attenuated ischemia-reperfusion-induced vasoconstriction, improved red blood cell velocity, capillary flow, and leukocyte adherence to the endothelium wall. Hemodynamics was stable throughout the experiment.

CONCLUSIONS

Enhancing NO bioavailability via exogen application of NOSs and L-arginine significantly attenuated ischemia-reperfusion-induced microcirculatory alterations in the microvasculature of skeletal muscle. Significant hemodynamic adverse effects were not present, thus demonstrating this approach might be useful for therapeutic intervention. This "pharmacologic preconditioning" could be an easy and effective interventional strategy to uphold conversation of L-arginine to NO under ischemic conditions.

Improved wound healing of postischemic cutaneous flaps with the use of bone marrow-derived stem cells

OBJECTIVES/HYPOTHESIS

To determine if the intravascular delivery of mesenchymal stem cells improves wound healing and blood perfusion to postischemic cutaneous flap tissues.

STUDY DESIGN

Randomized controlled study.

METHODS

A murine model of a cutaneous flap was created based on the inferior epigastric vessels. Mice (n = 14) underwent 3.5 hours of ischemia followed by reperfusion. Bone marrow stromal cells (BMSCs) 1 × 10(6) were injected intravenously. Wound healing was then assessed measuring percent flap necrosis, flap perfusion, and tensile strength of the flap after a period of 14 days. Localization of BMSCs was determined with radiolabeled and fluorescent labeled BMSCs.

RESULTS

Postischemic cutaneous flap tissues treated with BMSCs demonstrated significantly less necrosis than control flaps (P <0.01). Beginning on postoperative day 5, BMSC-treated flaps demonstrated greater blood perfusion than untreated flaps (P <0.01). Tensile strength of BMSC-treated cutaneous flaps was significantly higher (P <0.01), with a mean strength of 283.4 ± 28.4 N/m than control flaps with a mean of 122.4 ± 23.5 N/m. Radiolabeled BMSCs localized to postischemic flaps compared to untreated tissues (P = 0.001). Fluorescent microscopy revealed incorporation of BMSCs into endothelial and epithelial tissues of postischemic flaps.

CONCLUSIONS

This study demonstrates that the intravascular delivery of BMSCs increases wound healing and promotes flap survival following ischemia-reperfusion injury of cutaneous tissue flaps.