Large Prefabricated Skin Flaps Based on the Venous System in Rabbits: A Preliminary Study

Protein kinase D1 promotes the survival of random-pattern skin flaps in rats

BACKGROUND

In reconstructive surgery, random skin flaps are commonly used tools to cover skin defects, however, their applicability and size are limited by post-operative complications such as marginal ischemia-reperfusion injury and flap necrosis. Protein kinase D1 (PKD1), a calcium/calmodulin-dependent serine/threonine kinase, is known to induce angiogenesis and has been shown to mitigate ischemia in cardiovascular diseases. However, the role of PKD1 has not been investigated in skin flaps.

METHOD

Seventy-five male Sprague-Dawley rats with skin flaps were randomly divided into three groups: control, PKD1, and CID755673. Seven days following surgery, we assessed the general view and survival rate of the flap using histological analysis. Laser Doppler and lead oxide/gelatin angiography were used to evaluate microcirculation blood flow. Histopathological changes, neovascularization and microvascular density (MVD). were examined and calculated using microscopy after H&E staining. Protein expression levels were determined using immunoblotting and immunohistochemistry techniques.

RESULT

PKD1 significantly improved flap survival by upregulating angiogenic factors VEGF and cadherin5 and increasing antioxidant enzymes SOD, eNOS, and HO1, as well as reducing caspase 3, cytochrome c, and Bax expression, and attenuating IL-1β, IL-6, and TNF-α. In the PKD1 group, PKD1 increased neovascularization, and blood flow and flap survival areas were larger as compared to the control and CID755673 groups.

CONCLUSION

These findings show that PKD1 accelerates angiogenesis, reduces oxidative stress, and impedes apoptosis and inflammation, thus resulting in improved flap survival. Our observations indicated that PKD1 could be a therapeutic target for flap failure treatment.

Differences between novel hybrid mode flaps and traditional perforator flaps at the level of metabolites using LC-MS

The multi-territory perforator flaps are widely used in plastic surgery. However, partial necrosis flap in the potential territory remains a challenge to plastic surgeons. We raised a novel "hybrid nourished mode" (HNM) flap based on the multi-territory deep inferior epigastric perforator (DIEP) flap to improve flap survival. Thirty-two rabbits were randomly divided into DIEP and HNM groups. Untargeted metabolic mechanisms between the DIEP and HNM groups were performed using LC-MS under the filter criteria of fold change >20.0 times or <0.05, and variable importance in projection (VIP) value was set at ≥1, P < 0.05. Between the two groups, flap survival, perfusion, microvasculature, histopathology, and immunohistochemistry of CD31 were assessed on post-operative day 7. We screened 16 different metabolites that mainly participated in biosynthesis of secondary metabolites, aminoacyl transfer RNA biosynthesis, phenylalanine metabolism, arginine and proline metabolism, among others. The results of the HNM flaps were higher than those of the DIEP flaps (P < 0.05) in the aspects of flap survival, flap perfusion, and microvasculature. Compared with the DIEP flaps, HNM has a stronger advantage in tissue metabolism. This study provided us with a better understanding and strong evidence in terms of metabolites on how HNM achieves the survival of large multi-territory perforator flaps.

Current Status of Experimental Animal Skin Flap Models: Ischemic Preconditioning and Molecular Factors

Skin flaps are necessary in plastic and reconstructive surgery for the removal of skin cancer, wounds, and ulcers. A skin flap is a portion of skin with its own blood supply that is partially separated from its original position and moved from one place to another. The use of skin flaps is often accompanied by cell necrosis or apoptosis due to ischemia-reperfusion (I/R) injury. Proinflammatory cytokines, such as nuclear factor kappa B (NF-κB), inhibitor of kappa B (IκB), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and oxygen free radicals are known causative agents of cell necrosis and apoptosis. To prevent I/R injury, many investigators have suggested the inhibition of proinflammatory cytokines, stem-cell therapies, and drug-based therapies. Ischemic preconditioning (IPC) is a strategy used to prevent I/R injury. IPC is an experimental technique that uses short-term repetition of occlusion and reperfusion to adapt the area to the loss of blood supply. IPC can prevent I/R injury by inhibiting proinflammatory cytokine activity. Various stem cell applications have been studied to facilitate flap survival and promote angiogenesis and vascularization in animal models. The possibility of constructing tissue engineered flaps has also been investigated. Although numerous animal studies have been published, clinical data with regard to IPC in flap reconstruction have never been reported. In this study, we present various experimental skin flap methods, IPC methods, and methods utilizing molecular factors associated with IPC.

Distal Arterialized Venous Supercharging Improves Perfusion and Survival in an Extended Dorsal Three-Perforasome Perforator Flap Rat Model

BACKGROUND

Perforator flaps are commonly applied for a variety of skin defects. Many strategies (e.g., hyperbaric oxygen and preconditioning) have been investigated to improve flap survival, but a postoperative 2.03 to 18.2 percent flap necrosis frequency remains a major complication. The authors hypothesized that a distal arterialized venous supercharged (DAVS) flap procedure might improve perfusion and survival in an extended three-perforasome perforator flap rat model and rescue flap ischemia intraoperatively.

METHODS

One hundred twenty male Sprague-Dawley rats (200 to 300 g) were divided into the thoracodorsal artery (TDA) flap group and the DAVS flap group (n = 60 per group). An approximately 11 × 2.5-cm2 flap based on the TDA perforasome was designed in the TDA flap. A DAVS flap was designed based on the TDA flap and supercharged by anastomosing the rat caudal artery with the deep circumflex iliac vein. At postoperative times 1, 3, 6, and 12 hours and 1, 3, 5, and 7 days, perfusion and angiography were compared. On day 7, flap viability and angiogenesis were assessed using histology and Western blotting.

RESULTS

The DAVS flap showed a higher survival rate compared with the TDA flap (100 percent versus 81.93 ± 5.38 percent; p < 0.001). All blood flow ratios of deep circumflex iliac artery to TDA perforasome and of choke zone II to choke zone I were higher in the DAVS flap (all p < 0.05). Angiography qualitatively revealed that choke vessels in choke zone II dilated earlier and extensively in the DAVS flap group. CD34+ vessels (68.66 ± 12.53/mm2 versus 36.82 ± 8.99/mm2; p < 0.001) and vascular endothelial growth factor protein level (0.22 ± 0.03 versus 0.11 ± 0.03; p < 0.001) were significantly increased in the DAVS flap group.

CONCLUSIONS

The DAVS procedure improves three-perforasome perforator flap survival and can be used for rescuing flap ischemia intraoperatively. Further study is needed before possible clinical adoption for reconstructive operations.

Trans-Cinnamaldehyde Increases Random Pattern Flap Survival Through Activation of the Nitric Oxide Pathway

Background

The application of random pattern skin flaps is limited in plastic surgery reconstruction due to necrosis. Trans-cinnamaldehyde has antibacterial, anticancer, and antioxidant properties. In this study, we aimed to investigate the effect of trans-cinnamaldehyde on skin flap survival and its possible mechanism regarding nitric oxide.

Materials and Methods

One hundred forty male Sprague-Dawley rats were randomly divided into seven groups (n = 20 each group). After the dorsal flap was raised, different doses of trans-cinnamaldehyde (10, 20, and 30 mg/kg) were immediately given by oral gavage in the three different groups. To assess the possible involvement of the nitric oxide system, N^G-nitro-L-arginine methyl ester (L-NAME, a nonselective nitric oxide synthase inhibitor) was used in this study. All flap samples were incised on postoperative day 7.

Results

Our results showed that flap survival was increased significantly in the 20 mg/kg (P < 0.001) trans-cinnamaldehyde (TC) group compared to the control group or 30 mg/kg TC group. This protective function was restrained by coadministration of L-NAME with 20 mg/kg TC. The results of histopathology, laser Doppler, arteriography mediated with oxide–gelatine, and fluorescent staining all showed a significant increase in capillary count, collagen deposition, angiogenesis, and flap perfusion. Immunohistochemistry results revealed a significant increase in the expression of CD34, eNOS, and VEGF.

Conclusion

Trans-cinnamaldehyde increased flap survival through the nitric oxide synthase pathway and contributed to angiogenesis. A concentration of 20 mg/kg trans-cinnamaldehyde was recommended in this study.

Improvement of multiterritory perforator flap survival supported by a hybrid perfusion mode: A novel strategy and literature review

Perforator flaps have been widely used in clinical Settings, however, unexpected necrosis was still commonly encountered in the distal portions of multiterritory flaps known as Choke zone III. In this study, we introduced a novel hybrid perfusion technique which is different from the established one of arterial supercharging or venous superdrainage to improve multiterritory flap survival with success. In order to ensure the entire flap survival of multiterritory flaps extending to choke zone III, a "hybrid perfusion" mode by anastomosing a distal vein of the flap with a recipient artery was carried out in two cases based on our previous basic study. In addition, a systematic literature review regarding the established microsurgical assistant techniques of arterial supercharging and venous superdrainage techniques were performed. Both flaps survived uneventfully. At a minimal follow-up of six months, both patients were satisfied with the results. This novel hybrid perfusion technique provides a simple new concept in solving partial necrosis of multiterritory flaps. Further practice is guaranteed for better understanding this unconventional attempt.

Effects of arterial blood supply and venous return on multi-territory perforator flap survival

This study aimed to design arterial ischemic and venous congested areas on the same multi-territory perforator flap, assessing the effects of arterial blood supply and venous return on flap survival. Totally 68 rats were randomly divided into the experimental (Exp) and control (Con) groups. In the Exp group, flaps were based on left superficial epigastric artery and right superficial epigastric vein. In the Con group, flaps were based on the left superficial epigastric artery and vein. Immediate postoperative ink-gelatin angiography, epidermal metabolite levels detection, tissue edema measurement, survival rate evaluation in half of the flaps and average microvessel density assessment were performed. Blood in the Exp group flowed through most angiosomes, but only flowed around pedicled vessels in the Con group; metabolite levels of left halves in the Con and Exp groups were comparable with those of right halves. Angiosomes with high water contents occurred in the Exp group. Survival rates of left halves in the Con and Exp groups were higher than those of right halves, and more microvessels were found in the left ventral areas of both groups compared with the right ventral area in the Exp group. These findings revealed that on the same multi-territory perforator flap, arterial blood supply, affected by venous return, is a prerequisite for flap survival.

The feasibility and survival mechanism of a large free flap supported by a novel hybrid perfusion mode

OBJECTIVES

In this study, we presented a novel hybrid perfusion mode in an attempt to provide a new strategy to improve the survival of an extended large flap and discuss its possible mechanisms.

MATERIALS AND METHODS

A 14 × 10 cm flap was designed on the rabbit abdomen. Ninety-six rabbits were randomly divided into three groups based on the flap perfusion mode: control group I (CON 1, physiological perfusion mode with bilateral deep inferior epigastric vascular pedicles intact), control group II (CON 2, physiological perfusion mode with single deep inferior epigastric vascular pedicle intact), hybrid nourished group (physiological perfusion as in CON 2 combined with arterialized venous nonphysiological perfusion mode, referred to as a hybrid perfusion mode). Flap survival, status of vascular perfusion, microvasculature, histopathology, expression of CD34, eNOs, VEGF and metabolic status of the flaps by LC-MS were assessed in each group.

RESULTS

The results of "hybrid nourished" flaps were similar to the traditional flaps in terms of flap survival, level of vascular perfusion and microvasculature except the status of metabolites.

CONCLUSIONS

The feasibility of this novel hybrid perfusion mode will greatly extend the indications of flap transfer and efficiently improve the survival reliability of large flaps. In a sense, this mode will be an ideological emancipation for the field of flap surgery.

Unconventional Perfusion Flaps in the Experimental Setting: A Systematic Review and Meta-Analysis

Supplemental Digital Content is available in the text.

Background:

Unconventional perfusion flaps offer multiple potential advantages compared with traditional flaps. Although there are numerous experimental articles on unconventional perfusion flaps, the multiple animal species involved, the myriad vascular constructions used, and the frequently conflicting data reported make synthesis of this information challenging. The main aim of this study was to perform a systematic review and meta-analysis of the literature on the experimental use of unconventional perfusion flaps, to identify the best experimental models proposed and to estimate their global survival rate.

Methods:

The authors performed a systematic review and meta-analysis of all articles written in English, French, Italian, Spanish, and Portuguese on the experimental use of unconventional perfusion flaps and indexed to PubMed from 1981 until February 1, 2017.

Results:

A total of 68 studies were found, corresponding to 86 optimized experimental models and 1073 unconventional perfusion flaps. The overall unconventional perfusion flap survival rate was 90.8 percent (95 percent CI, 86.9 to 93.6 percent; p < 0.001). The estimated proportion of experimental unconventional perfusion flaps presenting complete survival or nearly complete survival was 74.4 percent (95 percent CI, 62.1 to 83.7 percent; p < 0.001). The most commonly reported animal species in the literature were the rabbit (57.1 percent), the rat (26.4 percent), and the dog (14.3 percent). No significant differences were found in survival rates among these species, or among the diverse vascular patterns used.

Conclusion:

These data do not differ significantly from those reported regarding the use of unconventional perfusion flaps in human medicine, suggesting that rabbit, rat, and canine experimental unconventional perfusion flap models may adequately mimic the clinical application of unconventional perfusion flaps.

Allogenic endothelial progenitor cell transplantation increases flap survival through an upregulation of eNOs and VEGF on venous flap survival in rabbits

BACKGROUND

Endothelial progenitor cells (EPCs) are one type of bone marrow hematopoietic stromal cells which play a vital role in neovascularization and tissue repair. In this study, we investigated whether EPCs promote flap survival in a rabbit venous model.

MATERIALS AND METHODS

EPCs were customized from CHI Scientific, Inc, China. Thirty-six rabbits were randomly assigned to either the sham group (n = 12), the control group (n = 12) or the EPC transplantation group (n = 12). A 10 × 6 cm venous flap was created on the rabbit abdomen. Both the EPC transplantation and control groups had the same volume of EPCs-PBS (phosphate buffered saline) and PBS on postoperative day 1. Flap survival, blood flow, histopathology, expression of endothelial nitric oxide synthase (eNOs) and Vascular Endothelial Growth Factor (VEGF) were detected on postoperative day 10.

RESULTS

Cellular immunofluorescence assay positively confirmed that the EPCs were undergoing differentiation. The survival rate of the flap in the EPC transplantation group was 58.4 ± 7.1%, which was significantly higher than that of the control group (4.8 ± 3.4%) (p<0.01). Histological examination revealed that the EPC transplantation group had higher microvessel density, fewer inflammatory cells, and a higher expression of eNOs and VEGF. Significantly increased blood flow perfusion was seen in the EPC transplantation group using laser Doppler imaging. The Western Blot technique revealed that the expression of eNOs and VEGF in the EPC transplantation group were both significantly higher than those in the control group.

CONCLUSION

This study demonstrated that EPC transplantation improved venous flap survival in rabbits. The present findings may provide insight into the promotion of venous flap survival in clinical practice in the future.

The complicated role of venous drainage on the survival of arterialized venous flaps

The arterialized venous flap (AVF) has been gradually popularized in clinical settings; however, its survival is still inconsistent and the role of venous drainage remains elusive. In this study, we aimed to investigate the role of venous drainage on the flap survival of arterialized venous flaps. An arterialized venous flap was outlined symmetrically in the rabbit abdomen. The arterial perfusion flap with a unilateral vascular pedicle was taken as the control group and three other experimental groups (I, II and III) were designed based on the number of drainage veins (n = 1, 2 and 3 in the three groups, respectively). Compared with the control group, significant venous congestion was noted in all the experimental groups and the most severe one was seen in group I; while no statistical difference was observed between groups II and III. Similar results regarding blood perfusion state, epidermal metabolite levels and flap survival status were obtained among the three groups. These findings suggested that venous drainage is vital in the survival of the flap, but unlike in the arterial perfusion flaps, the problem of venous congestion can only be partially solved by increasing the number of draining veins. Further studies are warranted to gain insight into this complicated issue.

Laryngotracheal reconstruction with a prefabricated fasciocutaneous free flap for recurrent papillary thyroid carcinoma

BACKGROUND

Prefabricated composite free flaps have been described as a technique for reconstruction of laryngotracheal defects.

METHODS

We present a 74-year-old woman with recurrent papillary thyroid carcinoma (PTC) who was initially treated with thyroidectomy, tracheal resection, and subsequent vocal cord medialization. The patient's recurrent disease was treated with partial laryngectomy and reconstruction using a prefabricated composite free flap. A 2-stage procedure was performed using conchal cartilage to create a prefabricated radial forearm free flap.

RESULTS

The patient's airway was successfully reconstructed with preservation of speech and swallow function.

CONCLUSION

This case provides further evidence supporting the use of prefabricated free flaps in airway reconstruction and the ability to obtain successful outcomes in a patient with multiple prior surgeries in the operative field and requiring adjuvant external beam radiation therapy. © 2016 Wiley Periodicals, Inc. Head Neck 38: E2512-E2514, 2016.