Aprotinin in ischemia-reperfusion injury: flap survival and neutrophil response in a rat skin flap model

Eco-Friendly Preparation of Epoxy-Rich Graphene Oxide for Wound Healing

Despite the ever-growing endangerment caused by the multidrug resistance (MDR) of bacteria, the development of effective antibacterial materials still remains a global challenge. Current antibiotic therapies cannot simultaneously inactivate bacteria and accelerate wound healing. This study aimed to originally separate the intercalation of MnO₃⁺ and the oxidation processes to synthesize epoxy-rich graphene oxide (erGO) nanofilms via an eco-friendly synthetic route, which possessed low density and large lamellar distribution and was rich in epoxide. Importantly, the MnO₃⁺ could be separated from the product and recycled for preparing the next generation of erGO nanofilms, which was quite economical and eco-friendly. The erGO nanofilm was capable of successfully inhibiting Gram-negative bacteria and even had excellent growth-inhibitory effects on Gram-positive bacteria including multidrug resistance (MDR) bacteria, as evidenced by antibacterial phenomena. Additionally, the erGO nanofilm with high ^•C density formed from epoxide exerted excellent antibacterial effects through tight membrane wrapping and induction of lipid peroxidation. The wound-healing property of the erGO nanofilm was evaluated via treatments of wounds infected by Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), which not only killed bacteria but also accelerated wound healing in mice with a skin infection. The novel erGO nanofilm with dual antimicrobial mechanisms might serve as a promising multifunctional antimicrobial agent for medical wound dressing with high biocompatibility.

The Vasodilator Effect of a Cream Containing 10% Menthol and 15% Methyl Salicylate on Random-Pattern Skin Flaps in Rats

Background

It is still difficult to prevent partial or full-thickness flap necrosis. In this study, the effects of a cream containing menthol and methyl salicylate on the viability of randompattern skin flaps were studied.

Methods

Forty female Sprague-Dawley rats were divided into two equal groups. Caudally based dorsal random-pattern skin flaps were elevated, including the panniculus carnosus. In the study group, 1.5 mL of a cream containing menthol and methyl salicylate was applied to the skin of the flap, and saline solution (0.9%) was used in the control group. Upon completion of the experiment, flap necrosis was analyzed with imaging software and radionuclide scintigraphy. Histopathological measurements were made of the percentage of viable flaps, the number of vessels, and the width of the panniculus carnosus muscle.

Results

According to the photographic analysis, the mean viable flap surface area in the study group was larger than that in the control group (P=0.004). According to the scintigrams, no change in radioactivity uptake was seen in the study group (P>0.05). However, a significant decrease was observed in the control group (P=0.006). No statistically significant differences were observed between the groups in terms of the percentage of viable flaps, the number of vessels, or the width of the panniculus carnosus muscle (P>0.05).

Conclusions

Based on these results, it is certain that the cream did not reduce the viability of the flaps. Due to its vasodilatory effect, it can be used as a component of the dressing in reconstructive operations where skin perfusion is compromised.

Comparison of the effects of systemic sildenafil, tadalafil, and vardenafil treatments on skin flap survival in rats

OBJECTIVE

The most important issue in flap surgery is flap viability. This study aimed to compare the effects of most commonly used phosphodiesterase type 5 (PDE5) inhibitors on flap survival.

METHODS

A 3 × 9 cm flap was elevated from the dorsum of 32 Wistar albino rats. In the control group, saline was administered 2 hours before the flap elevation and continued for 2 days after the surgery. In the sildenafil, tadalafil, and vardenafil groups, the related drug was administered. Blood flow in the flaps was monitored with laser Doppler flowmetry. On postoperative day 7, flaps were photographed and biopsies were obtained.

RESULTS

The ratios of flap necrosis area in the tadalafil, sildenafil, and vardenafil groups were lower than that in the control group, but without significant difference (p = 0.077). Histopathological evaluation revealed no significant difference among the groups.

CONCLUSION

The ratio of flap necrosis area tended to be lower in the groups receiving oral PDE5 inhibitors than in the control group, although not statistically significant. The role of PDE5 inhibitors needs to be evaluated in larger studies before a conclusion can be made regarding their effects on flap viability.

Bilirubin provides perforator flap protection from ischaemia-reperfusion injury in a rat model: a preliminary result

The use of bilirubin, a well-known and powerful antioxidant, has gained popularity in recent years because of its role in the prevention of ischaemic heart disease in patients with Gilbert's syndrome. We investigate the effects of bilirubin on ischaemia-reperfusion (I/R) injury using a rat perforator flap model. Forty-eight rats were randomly divided into two groups: experimental (bilirubin) group (n = 24) and control group (n = 24). In each group, elevated bilateral deep inferior epigastric perforator (DIEP) flaps were created. The right (no ischaemia side) and left (ischaemia side) DIEP flaps were separated according to the presence of ischaemia induction. Ischaemia was induced in anaesthetised rats by perforator clamping for 15 or 30 minutes. After surgery, the flap survival was assessed daily on postoperative days 0 to 5, and overall histological changes of DIEP flaps above the perforator were analysed at postoperative day 5. The flap survival rate in the bilirubin group was significantly higher than that in the control group at the ischaemia side following perforator clamping for 15 or 30 minutes (93·42 ± 4·48% versus 89·63 ± 3·98%, P = 0·002; and 83·96 ± 4·23% versus 36·46 ± 6·38%, P < 0·001, respectively). The difference in flap survival between the two groups was the most prominent on the ischaemic side following 30 minutes of perforator clamping. From a morphologic perspective, pre-treatment with bilirubin was found to alleviate perforator flap necrosis caused by I/R injury in this experimental rat model.

The protective effect of aprotinin and alpha-tocopherol on ischemia-reperfusion injury of the rat liver

BACKGROUND

Liver injury caused by ischemia-reperfusion (I/R) processes is a complication of hepatic resection surgery and transplantation, particularly using grafts from marginal donors. Despite improvements in organ preservation and advances in surgical techniques, I/R injury remains a significant clinical problem. In this study, we investigated whether aprotinin provided protection against the adverse effects of I/R injury in liver tissue.

METHODS

Forty rats were randomized into four groups (n = 10): group I: (control group) I/R + no medication; group II: sham-operated group + no medication or I/R; group III: I/R + aprotinin; group IV: I/R + alpha-tocopherol. Malondialdehyde (MDA) was measured in the liver tissue and superoxide dismutase (SOD), catalase (CAT), aspartate aminotransferase (AST), alanine aminotransferase (ALT), as well as lactate dehydrogenase (LDH) in rat serum.

RESULTS

Administration of aprotinin and alpha-tocopherol before I/R resulted in significant reductions of MDA levels compared to the I/R alone group (group I; P = .01 and P < .01, respectively). Administration of aprotinin or alpha-tocopherol prior to I/R resulted in significant increases in SOD and CAT levels compared with the I/R group (P < .05 each). Compared to the I/R group, significant decreases in plasma AST, ALT, and LDH levels were observed both in the aprotinin and in the alpha-tocopherol group (P < .05). Histological evaluation revealed the injury grade to be relatively lower among groups III and IV compared to group I.

DISCUSSION

In conclusion, rat hepatic structures in aprotinin and alpha-tocopherol administered groups were well protected. Therefore, aprotinin may provide protection against the adverse effects of I/R injury in liver transplantation.

The protective effect of melatonin on ischemia-reperfusion injury in the groin (inferior epigastric) flap model in rats

Inadequate blood perfusion and ischemia-reperfusion (I/R) injury in the surgical skin flap are believed to be the major factors that cause harmful changes within the tissue and vasculature, resulting in flap necrosis. Reactive oxygen radical species (ROS), in part, are believed to play an important role in this injury. Melatonin, in many physiological conditions, has been shown to have direct and indirect antioxidative effects and free-radical-scavenging properties. Therefore, it may have a beneficial effect on I/R-induced flap injury. In this study, the possible protective effects of melatonin were investigated in I/R injury of rat epigastric (axial pattern) flaps. Ischemia was achieved for 12 h by occlusion of inferior epigastric artery. Melatonin or vehicle was administered 1 h before flap elevation and was continued for 6 days after ischemia. I/R injury elevated malondialdehyde (MDA), an end product of lipid peroxidation, and nitric oxide (NO) levels while the glutathione (GSH) content was reduced. Myeloperoxidase (MPO) activity, which is known to be related to tissue neutrophil accumulation, was found to be statistically higher in the I/R group when compared with the sham group. Administration of melatonin significantly decreased MDA, NO and MPO levels and elevated the GSH content. Moreover, melatonin reduced the flap necrosis area, which was determined using a planimetric method. In conclusion, melatonin, a potent scavenger of free radicals, plays a major role in preventing the inferior epigastric arterial I/R-induced flap necrosis, based on planimetric flap survival and biochemical results. The beneficial effects of melatonin in I/R injury implies the involvement of free radicals in flap damage.

Age-dependent changes of postischemic reperfusion in rat skin

Ischemia-reperfusion plays a certain role in causing skin damage associated with pressure sores. In this study, changes in cutaneous hemodynamics during reperfusion were investigated in young and older rats. After cessation of 1-hour or 2-hour ischemia, the skin blood flow increased transiently (postischemic hyperemia) and quickly returned to the baseline in young and older rats. After 4-hour ischemia, however, the postischemic hyperemia was reduced in both groups, and the skin blood flow decreased below the baseline for a few hours in older rats. The skin blood flow tolerated well the repeated exposures to 1-hour ischemia in both groups. In 2-hour ischemia experiments, the postischemic hyperemia was preserved after the second ischemic period in young rats but not in older rats. These results suggest that the tolerance of skin microcirculation to ischemia-reperfusion may decrease with increasing age.

Arterial blood flow and microcirculatory changes in the rat groin flap after ischemia provocation by electrical stimulation of the artery

An island groin flap based on the inferior epigastric vessels was raised in 10 rats in order to monitor simultaneous ischemic changes in arterial blood flow and skin microcirculation induced by electrical stimulation of the feeding artery. A modified laser Doppler perfusion system recorded blood flow in the epigastric artery and in the skin microcirculation of the flap before and for 40 min after the experimentally induced ischemia. Sections of the stimulated segment of the vessel were obtained at the end of the experimental procedure for histological analysis to determine the extent of endothelial changes, if any. Artery blood flow and the flap microcirculation decreased significantly immediately after stimulation, both slowly increasing to prestimulation levels after 30 min. Artery perfusion was quicker than microcirculation to recover to the baseline value, indicating that reperfusion of larger vessels could involve mechanisms fundamentally different from those active in the resolution of ischemia at the capillary level. Histological artery examination revealed no significant endothelial damage at the stimulation site, thus demonstrating that electrical stimulation induces reproducible ischemia without visible endothelial damage. The differential effects on the feeding artery and on capillary perfusion indicate recruitment of several different mechanisms.