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Roxadustat (FG-4592) is a specific hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor. We investigated the effects of FG-4592 pretreatment on survival and second choke vessels of multi-territory perforator flaps in rats. In total, 72 rats were divided into two groups (n = 36 each): the experimental (FG-4592) group and the control group. FG-4592 was administered orally as a single dose of 60 mg/kg every other day; the first drug solution was administered to the animals 7 days before the surgical procedure. On postoperative day 7, the surviving flap area was calculated. At 12 h post-surgery, in the second choke zone in the flaps, macrovascular hinges were compared by angiography and imaging, and microvascular changes were assessed by histology. Laser Doppler imaging was used to evaluate flap perfusion at the second choke zone at 12 h and 7 days after surgery. At 7 days after surgery, the flap survival area and perfusion were significantly greater in rats given FG-4592 compared with controls. At 12 h after surgery, the diameter of macrovascular and microvascular vessels, nitric oxide content, perfusion, and the protein levels of HIF-1α and inducible nitric oxide synthase were also significantly greater in FG-4592-treated rats than controls. In conclusion, pretreatment with roxadustat may improve initial flap survival and dilate the second choke zone vessels in a multi-territory perforator flap.

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BACKGROUND: Multi-territory perforator flaps have become the preferred option for the repair and reconstruction of large soft tissue defects. Although methods (e.g., pharmacological agents, mechanical stimulation, and thermal stimulation) were developed to open choke vessels to improve flap survival, the flap necrosis rate is still as high as 28.8%. The authors hypothesized that high-pressure infusion might enhance flap viability by dilating choke arteries intraoperatively in a rat model of multi-territory perforator flap. METHODS: Two-month-old male Sprague-Dawley rats were randomized into two groups (n = 32 each). During the multi-territory perforator flap elevation based on the right superficial epigastric angiosome, one group received continuous high-pressure infusion (mean pressure, 250 mmHg; duration, 1 min) of an isotonic heparin sodium solution (12,500 U/L) via the artery in the pedicle, whereas the other group received no infusion. At 7 days postoperatively, arteriography was performed; endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) expression and microvascular density were evaluated by western blot and histology, respectively; and flap survival was compared. Moreover, intraluminal diameters were examined at 1 day and 7 days postoperatively using hematoxylin and eosin staining, and coagulation function was assessed immediately postoperatively. RESULTS: High-pressure infusion significantly promoted the dilation of choke arteries at 1 day and 7 days postoperatively. It also increased eNOS and VEGF expression, flap survival, and microvascular density. The coagulation function remained unaffected. CONCLUSIONS: High-pressure infusion allowed intraoperative and postoperative dilation of the choke arteries that enhanced the viability of multi-territory perforator flaps in rats.

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BACKGROUNDS: The quantified relationship between perforator diameter and flap length can be supported, and the impact of different strategies of managements of a non-pedicled perforator with two major subfascial divisions on flap survival has never been explored. MATERIALS AND METHODS: This study was divided into two parts. In Part I, 48 Sprague-Dawley rats underwent flap harvesting based on six perforators with a diameter gradient. Then, the flap length and perforator diameter were measured for establishment of an equation. In Part II, 32 rats underwent harvest of a transverse flap based on the right superficial epigastric perforator. In 16 rats the right intermediate iliolumbar perforator was severed in a distal-to-division approach, whereas, in the other 16 rats, it was severed with in a proximal-to-division approach. Necrosis rates and blood perfusion were also compared. RESULTS: The equation y = 13.02 × x + 2.29 could be established between the perforator diameter in the pedicle (x) and the flap length (y) that could be supported with R2=0.8963 and P < 0.001.The transverse flap with a distal-to-division management of the intermediate iliolumbar perforasome was weaker in perfusion and had a necrosis rate of 49±4%, whereas the flap with a proximal-to division management had a significantly stronger perfusion and a lower necrosis rate of 21±2% (P<0.001). CONCLUSIONS: The safe flap length that can be estimated based on a perforator with a known diameter can be calculated using y=13.02× x +2.29. A short segment of the stem of an intermediate perforator with two major subfascial branches should be preserved to augment flap survival.

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Knowledge of facial anatomy is indispensable for dermatologists and plastic surgeons practicing aesthetic medicine, especially for those using fillers, as injection of fillers may be associated with serious complications such as vascular occlusion and blindness. Angiosome and choke vessels play an important role in vascular incidents occurring after filler injections. The objective of this article was to outline the anatomy and pathophysiology of choke vessels, a concept which is not well known to dermatologists.

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BACKGROUND: The present study was designed to investigate the effects of irisin pre-treatment on multi-territory perforator flap survival and blood vessels of Choke II zone in rats and to explore the underlying mechanism. METHODS: Eighty adult Sprague-Dawley (SD) rats were divided into the Irisin group and the saline group (N = 40 each), and subjected to multi-territory perforator flap operations on the left flank. Rats in the irisin group were intraperitoneally injected with irisin (40 ng/kg), and rats in the control group were intraperitoneally injected with normal saline. Seven days after operation, we calculated the surviving flap area was calculated, and measured the density of microvessels, epidermal growth factor and blood flow in Choke II zone. RESULTS: Irisin pre-treatment could improve the flap survival area, increase average density of microvessels and up-regulate the mRNA and protein level of vascular endothelial growth factor, thereby promoting flap angiogenesis. CONCLUSION: Irisin improved flap blood supply and increase the survival rate of multi-territory perforator flap by promoting angiogenesis of flank multi-territory perforator flap survival in Choke II zone.

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Trans-territory perforator flaps are commonly used to reconstruct large defects of the soft tissues. The distal portion of the flap often becomes necrotic, however, as a result of the jeopardised vasculature of choke zone II. The trophic and vascular regenerative properties of bone marrow mesenchymal stem cells (BMSC) seemed to be a promising approach to prevent flaps becoming ischaemic. The purpose of our study is to evaluate the effects of BMSC on the survival of the three-territory perforator flap. The flap model was created based on the deep circumflex iliac vessel in rats. Eighteen rats were distributed, at random, into three groups. Immediately after the flaps were placed, groups were respectively given a single panniculus carnosus injection at choke zone II of either 1×105 (BMSCslow), 1×106 (BMSCshig) BMSC, or phosphate-buffered saline (PBS). On postoperative day seven, we assessed the gross view of the flap and survival. We also evaluated microvessels by histological examination and angiogenesis-related gene expression by quantitative real-time polymerase chain reaction. After high dosage of BMSC, the flap survival rate, diameter and density of microvessels, vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) levels were significantly higher in the BMSC treatment group than the control group. We therefore confirmed the positive effects of BMSC on the survival of multi-territory perforator flaps.

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BACKGROUND: "Choke vessels" are communicating conduits between adjacent perforasomes in the skin. Most researches focus mainly on the arterial aspect of the "choke vessels" and neglect the venous aspect, an imbalance needed to be addressed. MATERIALS AND METHODS: The study was divided into parts I, II, and III. Part I was for observation of the vascular morphological evolution in the choke zone after flap harvest in rats. Part II was for determination of the importance of the dilation of the arterial and venous components of "choke vessels" by preserving the iliolumbar artery (ILA group) or vein (ILV group). A laser Doppler flowmeter and a speckle flow imaging system were adopted for monitoring the hemodynamic impact caused by the different manipulation. Part III was for corroboration of part II by manipulation of other vessels. RESULTS: In part I, the arteries and veins between the iliolumbar and intercostal perforasomes underwent modest dilation, whereas the venules between the veins nearly quadrupled in diameter. In part II, flaps in the ILA group were much more intensive in blood perfusion than flaps in the ILV group. The flap necrosis rate was 0.31 ± 0.07 in the ILV group, being significantly larger than 0.10 ± 0.03 in the ILA group. Part III confirmed that venous superdrainage is less efficacious in reducing flap necrosis than arterial supercharging, in which the position of the additional artery was far more important than the diameter. CONCLUSIONS: The extensive dilation of the venous component of choke vessels makes a more potent compensatory role for venous drainage after flap harvest, indicating arterial supercharging is better in augmenting flap viability than venous superdrainage.

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BACKGROUND: The aim of this study was to explore the hemodynamic and morphological changes of the choke vessels, and to investigate the role of HIF-1α in the flap adaptation to hypoxic and choke vessel transformation after multi-territory perforator flap transplantation. METHODS: Animal model of single pedicle multi-territory perforator flap was established in the back of SD rats and the blood supply characteristics were studied by gelatin-oxide perfusion technique. HE staining and stereomicroscope were used to observe vascular changes. Afterward, the influence of hypoxia on cell proliferation and apoptosis were detected by MTT assay and flow cytometry, respectively. Besides, the expression of HIF-1α, iNOS and VEGF expression of HUVECs under hypoxia were detected by qRT-PCR and Western blot. RESULTS: The results revealed that all the choke vessels immediately began to expand after operation. The day after operation, some of the choke vessels continued to grow and expand, turning into the true anastomosis, while the others gradually dwindled and finally disappeared. Compared with the control group, the day after transplantation, the expression levels of both HIF-1α and iNOS were significantly increased. The only different was that HIF-1α was then maintained a high level, iNOS was significantly decreased aftertimes. What's more, the expression of VEGF was increased to the maximum at 3 days after operation and then decreased. In HUVECs, hypoxia increased the expression of HIF-1α, iNOS and VEGF protein. Besides, it also promoted the proliferation and inhibited the apoptosis. In addition, we also found that hypoxia-induced VEGF and iNOS upregulation is mediated by HIF-1α overexpression and HIF-1α knockout can reverse the effects induced by hypoxia. CONCLUSIONS: We found that HIF-1α may participate in the early vascular dilatation of transregional skin flap by inducing iNOS expression and promoting the reconstruction of choke vessels through increase VEGF expression.

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The authors reviewed the concepts of the axial pattern flap, angiosome and perforasome, and analyzed the anastomosis and hemodynamic characteristics between the angiosome and the perforasome. Results: (1) Axial pattern flaps can be designed either in the angiosome or in perforasome. The difference is the pedicle and vascular axis. (2) The middle perforator should be the first choice as the pedicle for multi-perforators cross-territory flap, and the axial direction of the flap should be the same as that of the source artery. (3) Avoid as much as possible nutrient large flap with small blood vessels, that is, using a perforating vessel as a pedicle to cross-zone support to an angiosome flap. (4) The position of vascular pedicle and venous drainage is more important than the size and number of blood vessels. It is proposed that the transformation and reconstruction of the axial vascular in the multi-perforated cross zone flap to establish a new blood circulation system is a research hotspot and challenges in the study of anatomy. It is necessary to work closely with the surgeons.

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Ischemic necrosis of the surgical flap is a common complication. The behavior of choke vessels has an important role in skin flap survival. However, the mechanism of choke vessel remodeling has remained elusive. The purpose of the present study was to investigate the possible association between inflammatory responses and choke vessel remodeling in the extended perforator flap model in rats. After flap elevation, the animals were randomly divided into three groups (n=6 in each) for tissue analysis at three, five or seven days after flap surgery. Six additional rats served as a control group (no flap elevation). Tissue samples were collected from the choke zone for histological, western blot and PCR analyses. Monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α) as inflammatory cytokines were examined in the present study. Histopathological analysis showed that dilation of choke vessels and increased vessel wall thickness was obvious after flap elevation. It also showed edema, inflammation cell aggregation after the operation. Compared with the control group, the protein and mRNA expression levels of MCP-1 and TNF-α were significantly increased at days 3, 5 and 7 after flap elevation, while reaching a maximum at day 5. These findings indicated that inflammatory responses may have an important role in choke vessel remodeling. MCP-1 and TNF-α may be considered as potential targets for modulating the behavior of choke vessels.

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Objective To investigate the effects of DMOG on the microcirculation of the choke-area and the survival of the cross-boundary flap in rats via tail vein injection.Methods Rats with ischemic three-territory perforator flaps on the dorsum were treated with DMOG at a dosage of 40 mg/kg body weight via tail vein injection at 1 day before surgery(day-1),the time of surgery(day 0),1 day after surgery(day 1),2 days after surgery(day 2) and 3 days after surgery(day 3).Control group received sterile saline at the same time points and same dosage via tail vein injection.① Draw materials from the choke-area at day 1,day 3 and day 7,HE stain was used to compare the diameter size of the artery and vein at the same site.② Western blotting to check the expression of PCNA and HIF-1α,ELISA to detect the content of PCNA,HIF-1α,SDF-1α and VEGF at day 7.③At day 7,measure the survival area of the flap and observe the vessel of the flap by lead oxide-gelatine technique.Results ① There was a greater survival rate of (96.3 ± 5.1)％ in the treatment group than in the control group with (73.9 ± 5.8)％ at day 7 (P ＜ 0.05).② The diameter size of the arterioles and venules were dilated in both groups until postoperative days 7.But the treatment group was more expanded than the control group at day 3(2.20 ± 0.26 vs.1.50 ± 0.20,P ＜ 0.05) and day 7(3.67 ± 0.35 vs.2.03 ± 0.15,P ＜ 0.05).③ The skin expression of PCNA and HIF-1α in the treatment group were greater than the control group(P ＜ 0.05) at day 7.④ The content of skin PCNA in the treatment group and control group were(8.95 ± 0.71) ng/mg and (4.15 ± 0.72) ng/mg,HIF-1α were(5.04 ± 0.50)ng/mg and (2.98 ± 0.29) ng/mg,SDF-1α were (2.91 ± 0.61) ng/mg and (1.39 ± 0.62) ng/mg,and VEGF were(2.17 ± 0.41) ng/mg and (0.95 ± 0.44) ng/mg,respectively.The treatment group was greater than the control group (P ＜ 0.05).Conclusion DMOG can improve the microcirculation of the choke area,and then increase the survival of the perforator skin flaps in rats via tail vein injection.

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Objective To establish a mouse ’ s cross-territory ear flap that enables chronic , in-vivo observation of the change of vascular morphology .Methods 30 ICR mice, weighing 25~40 g, were used for this study .Commercial depilatory cream was used to first remove the hair of the mice , after which the vascular pattern in the ears was investigated . According to the observation of the vascular pattern in the mouse ’ s ear, the eye scissors were used the sever the outer 2/3 of the base of the ear , in which process a ear ’ s flap based on a vascular pedicle but crossed three vascular territories was created.After the creation of the flap , the mice were placed on an automatic controlled movable machine with the ear ’ s flaps spread over a customized Plexiglas .Then the flaps were photographed under the stereoscope ( ×25) at the following time points:1,2,3,5,7,10,14,21,30 d.the necrosis of the flap, and the morphological change of the vessels within theflap were analyzed .Results The ICR mouse ’ s ear was supplied three angiosomes , which were respectively named as the cephalic , median and caudal angiosomes from inside out .Five days after the flap’s creating, necrotic rate of(15 ±7)%was developed .The choke vessels between the medial and median angiosomes expanded rapidly in diameter , reaching the plateau 10d after flap creation, resulting the dilated choke veins and arteries at their peak being 3.9 ±0.5 and 3.5 ±0.7, respectively, than their initial sizes.The diameter of the choke veins began to shrink at approximately 10d, stabilizing after 21d.The diameter of the choke arteries plateaued and stabilized at around 10d.Conclusion ①after harvest of extended flap, the dilation of veins seemed to passive , whereas the dilation of arteries seemed to active;②the number of the choke vessels between the dynamic and potential territories that are involved in dilation and extent of the dilation are much smaller than that of the choke vessels between the anatomic and dynamic territories;③the mouse ’ s ear flap is an excellent model of further study of mechanism underlining the dilation of choke vessels and for the screening of vasoactive drugs that augment the survival of the large flap .