| With the increase of traffic accident and other mechanical trauma resulting from the great development of economy construction and modern vehicles, skin crush-avulsion injury has become common in our daily life. Skin crush-avulsion injury differs from standard clear-cut and direct amputations because the injury that causes crushing, shearing, and avulsion, finally resulting in severe macroscopic and microscopic damage. Moreover, the secondary necrosis of flap would make the skin flap which still has blood perfusion during operation gradually become necrosis in 3 to 5 days later. The traditional treatment involves re-attachment of the avulsed skin flap to its original location often cause disfigurement, both functionally and aesthetically. So the therapy of skin crush-avulsion injury has become a major concern in plastic and reconstructive surgery. Therefore, in this study, using a skin crush-avulsion injury model on rat, we investigated the putative protective effects of a newly natriuretic peptide-Vasonatrin peptide (VNP) against tissue damage after skin crush-avulsion injury, and which would provide a new therapy for clinic.This research was based on the skin crush-avulsion injury model on rat, established by our department, and a dorsal random pattern flap 3cm x 9 cm was elevated, which consisted of skin, panniculus carnosus muscle, and submuscular areolar tissue. Then the prepared skin flap was crushed by our crush-injury model machine and repeated the crushing process 3 times to form a rat skin crush-avulsion model. Arteriolar blood flow, functional capillary density, leucocyte adhesion and thrombogenesis of the flap were analyzed by intravital fluorescence microscopy circa the operation. And the results showed that significantly decreased arteriolar blood flow was observed after the crush injury , which resulted in severe alteration of functional capillary density (P<0.01). The impaired microcirculation was associated with thrombogenesis which happened about 30 min after the injury.On day 7 after the operation, the surviving and necrotic regions were clearly demarcated in the flaps. The sham group had the highest survival rate like we had expected and the percentage of survival flap area in VNP treated group was significantly higher than that in the control group(P<0.05). P-selectin, which express on endothelium and platelet, is responsible for the early stages of leukocyte-endothelial interaction and the marker of thrombus formation. L-selectin, on the other hand, constitutively expressed on neutrophils, is necessary for neutrophil–endothelial interaction in the postcapillary venule. In our study, P- and L-selectin expression were intensely increased in the control group but were correspondingly weaker in the VNP group, and that demonstrating VNP can also inhibit the expression of P- and L-selectin (P<0.05). Thus, the usage of VNP in the early stage of skin crush-avulsion injuries may be particularly important for reduction of leukocyte rolling, accumulation and the associated tissue damage. TNF-α, IL-1βand IFN-γare important inflammatory cytokines which involved in many inflammatory responses with widely biological activity, and their levels reflect the severity of inflammation. Malondialdehyde (MDA), whose level is an index of active oxygen radicals. The GSH-PX activities, which is an indicator of Glutathione (GSH), is an important antioxidant. MPO is deposited in neutrophil granules, whose enzyme activity reflect the tissue neutrophil accumulation. The results of our study indicate that levels of certain inflammatory stimuli such as TNF-α, IL-1βand IFN-γwere significantly inhibited by VNP (P<0.05). The function of IFN-γmaybe mainly react locally as the sera IFN-γlevels were relatively stable at each time point while the IFN-γlevels of local tissue fluid changed significantly with time. In the present study, there were statistically marked decline MDA levels and increase GSH-PX activities in the VNP-treated group, and this will support VNP have the antioxidative effect, thus could decrease oxidative injury on cellular structures. And the inhibited MPO activities in the VNP group demonstrate that VNP could alleviate inflammatory response by preventing neutrophil infiltration. Taken together, these facets of the biological activity of VNP are likely to have multiple applications as therapies for inflammatory. Laser Doppler perfusion monitoring showed that VNP markedly improved the blood stream and tissue blood perfusion volume of the distal and central points of the flaps(P<0.05), which affect the survival directly, and the result of histopathological examination corroborated the data.This study suggests that although full-thickness of the avulsed skin flap is injured, it is the microcirculation system that suffers the most serious damage and the process after skin crush-avulsion injury is a multistep, complex series of event. However, VNP could antagonize most of the injury factors. Thus, VNP, which hold the dual role of atrial ANP and CNP in the biological activity, has the potential to be a new therapeutic drug for flap necrosis. As a result of lacking the specific degradation endopeptidase in corpore, VNP could overcome other natriuretic peptide's defects such as fast metabolism, short duration, which has more potential clinical value. |
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