Reduction of skin flap necrosis by transdermal application of buflomedil bound to liposomes

Ischemic tissue injury in the dorsal skinfold chamber of the mouse: a skin flap model to investigate acute persistent ischemia

Despite profound expertise and advanced surgical techniques, ischemia-induced complications ranging from wound breakdown to extensive tissue necrosis are still occurring, particularly in reconstructive flap surgery. Multiple experimental flap models have been developed to analyze underlying causes and mechanisms and to investigate treatment strategies to prevent ischemic complications. The limiting factor of most models is the lacking possibility to directly and repetitively visualize microvascular architecture and hemodynamics. The goal of the protocol was to present a well-established mouse model affiliating these before mentioned lacking elements. Harder et al. have developed a model of a musculocutaneous flap with a random perfusion pattern that undergoes acute persistent ischemia and results in ~50% necrosis after 10 days if kept untreated. With the aid of intravital epi-fluorescence microscopy, this chamber model allows repetitive visualization of morphology and hemodynamics in different regions of interest over time. Associated processes such as apoptosis, inflammation, microvascular leakage and angiogenesis can be investigated and correlated to immunohistochemical and molecular protein assays. To date, the model has proven feasibility and reproducibility in several published experimental studies investigating the effect of pre-, peri- and postconditioning of ischemically challenged tissue.

A Random-Pattern Skin-Flap Model in Streptozotocin Diabetic Rats

BACKGROUND

Flap operations are frequently performed in diabetic patients. Nevertheless, we could find no experimental study examining diabetes mellitus's effect on the flaps' survival. For this reason, we designed this study as a random-pattern skin-flap model of diabetic rats in 1999.

METHODS

We used 72 rats weighing about 200 g each. The animals were divided into 2 groups, 1 experimental (diabetic) and 1 control (nondiabetic). Following their diabetic periods, we elevated the rats' modified McFarlane flaps and measured their viable flap areas.

RESULTS

The mean percentage of the flap area surviving was 51.40% in the 2-week experimental group. It was 48.20% in the 4-week experimental group and 36.70% in the 8-week experimental group. The mean percentage of flap area surviving was 65.87% in the united control group (the total of all control groups). The mean surviving skin-flap area in the united control group was significantly higher than in the 4- and 8-week experimental groups. Moreover, the mean surviving flap area in the 8-week experimental group was significantly lower than in the 2-week and 4-week experimental groups.

CONCLUSIONS

Our study demonstrated that a 4-week diabetic duration for rats is sufficient to observe diabetes' deleterious effects on the flaps' viability. These effects were significantly established, however, after 8 weeks of diabetes. To obtain definitive results, at least 8 weeks of diabetic duration are preferred for similar studies.

Effect of Polyvinylpyrrolidone-Iodine Liposomal Hydrogel on Wound Microcirculation in SKH1-hr Hairless Mice

AIM

Polyvinylpyrrolidone-iodine liposomal hydrogel (PVP-ILH) is a hydrogel formulation based on polyvinylpyrrolidone-iodine (PVP-I) and liposomes. The beneficial effects of PVP-ILH on wound healing have been previously shown. The aim of this study was to investigate the effects of topically applied PVP-ILH on wound microcirculation.

MATERIALS AND METHODS

Experiments were performed on wounds in male SKH1-hr hairless mice (n = 48). Mice were randomized into five treatment groups: mice treated with polyacrylic acid (PAA) and PAA 1:10 as well as PVP-ILH and PVP-ILH 1:10. Mice treated with sodium chloride served as control. Immediately as well as 3, 7, and 14 days after wounding, intravital fluorescent microscopy (IFM) was performed to determine wound surface area and standard microcirculatory parameters.

RESULTS

Topically administered PVP-ILH reduced wound size significantly faster compared to controls. Standard microcirculatory parameters, e.g. functional capillary density (FCD) and plasma leakage, showed no differences. FCD increases in all groups after wound creation. Using PVP-ILH, a trend towards higher FCD was observed.

CONCLUSION

The wound model in hairless mice in combination with IFM is suitable to qualitatively assess wound microcirculation over a period of 2 weeks even after topical application of pigmented ointments. PVP-ILH showed a positive effect on dermal wound healing and wound microcirculation.

Evolution of ischemic tissue injury in a random pattern flap: A new mouse model using intravital microscopy

BACKGROUND

Dissection of random pattern flaps may cause microcirculatory dysfunction and ischemia, which jeopardize wound healing due to impaired tissue viability. The aim of this study was to develop an in vivo model that enables continuous monitoring of the interplay between microcirculatory dysfunction, ischemia, and tissue injury by intravital microscopy.

MATERIALS AND METHODS

A laterally based random pattern skin flap (15 x 11 mm) including the panniculus carnosus was raised in the back of mice and fixed into a dorsal skinfold chamber (n = 10). Arteriolar blood flow, functional capillary density, number of apoptotic cells, and area of tissue necrosis were analyzed by intravital fluorescence microscopy in the proximal, middle, and distal part of the flap at day 1, 3, 5, and 7 after surgery. Chamber preparations without flap harvesting served as controls (n = 6).

RESULTS

At day 1, the distal part of the flap showed a decreased arteriolar blood flow (266 +/- 124 pl/s versus controls: 1418 +/- 351 pl/s; P < 0.05), which resulted in severe alteration of functional capillary density (43 +/- 11 cm/cm2 versus 270 +/- 7 cm/cm2; P < 0.001). The impaired microcirculation was associated with apoptotic cell death (277 +/- 50 cells/mm2 versus 50 +/- 5 cells/mm2; P < 0.05). Microcirculatory dysfunction persisted over 7 days, and, finally, resulted in 49 +/- 3% flap necrosis.

CONCLUSIONS

This new model enables repetitive and simultaneous in vivo microscopic evaluation of microvascular hypoperfusion, apoptosis, and tissue necrosis in a random pattern flap. By the use of gene-targeted mice, it bears great potential to analyze distinct mechanisms of flap failure. It further represents an ideal tool to study novel protective strategies, including induction of angiogenesis, heat shock proteins, and HIF-1alpha.

Influência do buflomedil em retalhos cutâneos isquêmicos: estudo experimental em ratos

Drogas vasoativas têm sido empregadas na tentativa de aumentar a viabilidade de retalhos cutâneos isquêmicos. O objetivo desse estudo foi avaliar os efeitos da droga vasoativa, buflomedil, na prevenção da isquemia de retalhos cutâneos em ratos. Utilizaram-se 20 ratos machos, que foram divididos em um grupo experimento (B) e um grupo controle (A). No grupo B foi administrado buflomedil na dose de 3mg/kg, via intraperitoneal a cada 12 horas por 2 dias antes da cirurgia e por 7 dias após a cirurgia. Utilizou-se um modelo de retalho cutâneo abdominal de 9 x 4cm com base cefálica. A avaliação consistiu na fluxometria a laser do retalho em pontos pré-determinados com leitura no pré e pós-operatório imediato e no 7.º dia de pós-operatório. Realizou-se análise planimétrica da área total do retalho, da área vascularizada e da área nécrotica no 7.º dia de pós-operatório. Observou-se presença de necrose inferior do retalho em todos os animais nos dois grupos. A análise estatística dos resultados obtidos não demonstrou na planimetria diferença significante entre os grupos controle e experimental. A fluxometria não apresentou diferença significante, em relação a média dos pontos, entre os dois grupos. Conclui-se que o buflomedil não é capaz de diminuir a necrose em retalhos cutâneos isquêmicos de ratos, da forma como utilizada neste experimento.