Improvement of skin paddle survival by application of vascular endothelial growth factor in a rat TRAM flap model

Effect of adipose-derived mesenchymal stem cells on the viability of the transverse rectus abdominis myocutaneous flap in rats

INTRODUCTION

The Transverse Rectus Abdominis Myocutaneous (TRAM) flap is used for breast reconstruction, but involves the risk of necrosis. Adipose tissue-derived mesenchymal Stem Cells (ADSCs) can be used to stimulate neovascularization and reduce the risk of TRAM flap necrosis.

AIM

Determine the effect of ADSCs on TRAM flap viability in rats.

METHODS

Twenty-four Wistar-EPM rats were distributed into three groups (n = 8). A right caudal pedicled TRAM flap was performed in all the animals and was the only procedure performed in Group TRAM. The additional procedures of intradermal injection of α-MEM culture medium and intradermal injection of α-MEM containing ADSCs labeled with a fluorescent marker were performed in Groups α-MEM and α-MEM-SC, respectively. The percentage of flap necrosis was determined, and the level of neovascularization and distribution of stem cells in the TRAM flap was assessed using immunohistochemical analysis and fluorescence microscopy, respectively.

RESULTS

The percentage of necrosis observed in Group α-MEM-SC was lower than that observed in Groups TRAM and α-MEM, namely 23.36 % vs. 50.42 % and 53.57 %, respectively (p < 0.05). In Zone IV of the flap, the number of vessels was greater in Group α-MEM-SC than in the other groups (p < 0.05). Multiple stem cells were observed in the four zones of the flap in Group α-MEM-SC. No stem cells were observed in Groups TRAM or α-MEM.

CONCLUSION

ADSCs increased TRAM flap viability and the number of vessels in Zone IV of the flap in rats.

Pharmacological Effects of Fasudil on Flap Survival in a Rodent Model

BACKGROUND

Necrosis of the perforator flap is a critical problem. Fasudil, an inhibitor of Rho-associated coiled-coil containing kinase, has antiapoptosis activity and attenuates oxidative stress in many diseases. We characterized the effects of fasudil through intraperitoneal injection on perforator flap survival and identified its possible mechanism.

METHODS AND MATERIALS

Rats were divided into a control group (without surgery), a flap group (only surgery), and a fasudil group (surgery plus fasudil). Perforator flaps were made on the backs of the rats. The expression of vascular endothelial growth factor, the protein kinase B (PKB/Akt), endothelial nitric oxide synthase, Bax, Bcl-2, Beclin-1, P62, and LC3 II/LC3 I was determined by Western blot at day 3 after surgery. Nitric oxide (NO) components, superoxide dismutase, and malondialdehyde were also measured at day 3. The survival rate and laser Doppler perfusion imaging were performed at day 7 after surgery.

RESULT

The group with fasudil treatment exhibited the higher survival rates and angiogenesis levels. Fasudil also induced the activation of Akt/eNOS/NO pathway detected by the Western blot and NO expression kit. Furthermore, Western blot results showed fasudil-attenuated apoptosis through a raised Bcl-2/Bax rate and enhanced autophagy levels through raised beclin-1, decreased p62, and the elevated rate of LC3 II/LC3 I. Finally, fasudil increased superoxide dismutase and decreased malondialdehyde.

CONCLUSIONS

In conclusion, fasudil treatment decreased necrosis of perforator flaps possibly by affecting the Akt/eNOS/NO pathway, attenuating apoptosis and activating autophagy.

Intra-arterial injection of human adipose-derived stem cells improves viability of the random component of axial skin flaps in nude mice

BACKGROUND

Skin flap necrosis is a common postoperative complication in reconstructive surgery. Recent evidence suggests that subcutaneously injected adipose-derived stem cells (ASCs) increase the viability of random skin flaps. Here, we examined whether intra-arterial human ASC administration could improve random component survival of axial skin flaps in nude mice.

METHODS

Human ASCs isolated from a healthy volunteer by liposuction were injected into nude mice through the right femoral artery at a low (1 × 10³ cells), medium (1 × 10⁴ cells), or high (1 × 10⁵ cells) dose. After ASC infusion, right superficial inferior epigastric vessels were ligated to create unipedicled superficial inferior epigastric artery (SIEA) flap with random extension.

RESULTS

Flap survival was higher in mice from all three ASC-treated groups, and particularly the medium-dose group was 30% better, than in the control group. Histological examination demonstrated a significantly higher vascular density in the axial skin flap in nude mice treated with the medium ASC dose than in control mice. PKH26-labeled ASCs were identified in skin flaps of ASC-treated mice; some endothelial cells exhibited positive staining for human HLA-A. Compared to the control group, mice in ASC-treated groups had higher vascular endothelial growth factor levels and lower tumor necrosis factor α, interferon γ, and interleukin-6 levels.

CONCLUSIONS

Intra-arterial human ASC administration increased the survival of axial skin flaps by attenuating inflammatory reactions and enhancing neovascularization. Intra-arterial ASC administration might yield a higher rate of these cells and of engraftment in the skin flaps. This approach may have a therapeutic role in increasing flap survival.

An injectable thermosensitive hydrogel for sustained release of apelin-13 to enhance flap survival in rat random skin flap

With the advantage of handy process, random pattern skin flaps are generally applied in limb reconstruction and wound repair. Apelin-13 is a discovered endogenous peptide, that has been shown to have potent multiple biological functions. Recently, thermosensitive gel-forming systems have gained increasing attention as wound dressings due to their advantages. In the present study, an apelin-13-loaded chitosan (CH)/β-sodium glycerophosphate (β-GP) hydrogel was developed for promoting random skin flap survival. Random skin flaps were created in 60 rats after which the animals were categorized to a control hydrogel group and an apelin-13 hydrogel group. The water content of the flap as well as the survival area were then measured 7 days post-surgery. Hematoxylin and eosin staining was used to evaluate the flap angiogenesis. Cell differentiation 34 (CD34) and vascular endothelial growth factor (VEGF) levels were detected by immunohistochemistry and Western blotting. Tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were assessed by enzyme linked immunosorbent assays (ELISAs). Oxidative stress was estimated via the activity of tissue malondialdehyde (MDA) and superoxide dismutase (SOD). Our results showed that CH/β-GP/apelin-13 hydrogel could not only reduce the tissue edema, but also improve the survival area of flap. CH/β-GP/apelin-13 hydrogel also upregulated levels of VEGF protein and increased mean vessel densities. Furthermore, CH/β-GP/apelin-13 hydrogel was shown to significantly inhibit the expression of TNF-α and IL-6, along with increasing the activity of SOD and suppressing the MDA content. Taken together, these results indicate that this CH/β-GP/apelin-13 hydrogel may be a potential therapeutic way for random pattern skin flap.

Tissue Engineering of the Microvasculature

The ability to generate new microvessels in desired numbers and at desired locations has been a long-sought goal in vascular medicine, engineering, and biology. Historically, the need to revascularize ischemic tissues nonsurgically (so-called therapeutic vascularization) served as the main driving force for the development of new methods of vascular growth. More recently, vascularization of engineered tissues and the generation of vascularized microphysiological systems have provided additional targets for these methods, and have required adaptation of therapeutic vascularization to biomaterial scaffolds and to microscale devices. Three complementary strategies have been investigated to engineer microvasculature: angiogenesis (the sprouting of existing vessels), vasculogenesis (the coalescence of adult or progenitor cells into vessels), and microfluidics (the vascularization of scaffolds that possess the open geometry of microvascular networks). Over the past several decades, vascularization techniques have grown tremendously in sophistication, from the crude implantation of arteries into myocardial tunnels by Vineberg in the 1940s, to the current use of micropatterning techniques to control the exact shape and placement of vessels within a scaffold. This review provides a broad historical view of methods to engineer the microvasculature, and offers a common framework for organizing and analyzing the numerous studies in this area of tissue engineering and regenerative medicine. © 2019 American Physiological Society. Compr Physiol 9:1155-1212, 2019.

Photobiomodulation with polychromatic light increases zone 4 survival of transverse rectus abdominis musculocutaneous flap

OBJECTIVE

The aim of this study was to evaluate the effect of relatively novel approach of application of polychromatic light waves on flap survival of experimental musculocutaneous flap model and to investigate efficacy of this modality as a delay procedure to increase vascularization of zone 4 of transverse rectus abdominis musculocutaneous (TRAM) flap.

METHODS

Twenty-one Wistar rats were randomized and divided into 3 experimental groups (n = 7 each). In group 1 (control group), after being raised, the TRAM flap was sutured back to its bed without any further intervention. In group 2 (delay group), photobiomodulation (PBM) was applied for 7 days as a delay procedure, before elevation of the flap. In group 3 (PBM group), the TRAM flap was elevated, and PBM was administered immediately after the flap was sutured back to its bed for therapeutic purpose. PBM was applied in 48 hours interval from 10 cm. distance to the whole abdominal wall both in groups 2 and 3 for one week. After 7 days of postoperative follow-up, as the demarcation of necrosis of the skin paddle was obvious, skin flap survival was further evaluated by macroscopic, histological and microangiographic analysis.

RESULTS

The mean percentage of skin flap necrosis was 56.17 ± 23.68 for group 1, 30.92 ± 17.46 for group 2 and 22.73 ± 12.98 for group 3 PBM receiving groups 2 and 3 revealed less necrosis when compared to control group and this difference was statistically significant. Vascularization in zone 4 of PBM applied groups 2 and 3 was higher compared to group 1 (P = 0.001). Acute inflammation in zone 4 of group 1 was significantly higher compared to groups 2 and 3 (P = 0.025). Similarly, evaluation of zone 1 of the flaps reveled more inflammation and less vascularization among the samples of the control group (P = 0.006 and P = 0.007, respectively). Comparison of PBM receiving two groups did not demonstrate further difference in means of vascularization and inflammation density (P = 0.259).

CONCLUSION

Application of PBM in polychromatic fashion enhances skin flap survival in experimental TRAM flap model both on preoperative basis as a delay procedure or as a therapeutic approach. Lasers Surg. 51:538-549, 2019. © 2019 Wiley Periodicals, Inc.

Effect of Electroacupuncture at The Zusanli Point (Stomach-36) on Dorsal Random Pattern Skin Flap Survival in a Rat Model

BACKGROUND

Random skin flaps are commonly used for wound repair and reconstruction. Electroacupuncture at The Zusanli point could enhance microcirculation and blood perfusion in random skin flaps.

OBJECTIVE

To determine whether electroacupuncture at The Zusanli point can improve the survival of random skin flaps in a rat model.

MATERIALS AND METHODS

Thirty-six male Sprague Dawley rats were randomly divided into 3 groups: control group (no electroacupuncture), Group A (electroacupuncture at a nonacupoint near The Zusanli point), and Group B (electroacupuncture at The Zusanli point). McFarlane flaps were established. On postoperative Day 2, malondialdehyde (MDA) and superoxide dismutase were detected. The flap survival rate was evaluated, inflammation was examined in hematoxylin and eosin-stained slices, and the expression of vascular endothelial growth factor (VEGF) was measured immunohistochemically on Day 7.

RESULTS

The mean survival area of the flaps in Group B was significantly larger than that in the control group and Group A. Superoxide dismutase activity and VEGF expression level were significantly higher in Group B than those in the control group and Group A, whereas MDA and inflammation levels in Group B were significantly lower than those in the other 2 groups.

CONCLUSION

Electroacupuncture at The Zusanli point can effectively improve the random flap survival.

Effects of High-Voltage Electrical Stimulation in Improving the Viability of Musculocutaneous Flaps in Rats

BACKGROUND

The musculocutaneous flap of the transverse rectus abdominis muscle is a technique used for breast reconstruction, and one of the complications of this procedure is tissue necrosis. The objective of the study is to determine the effect of high-voltage electrical stimulation (HVES) in the transverse rectus abdominis muscle flap in rats.

METHODS

Fourteen rats underwent surgery for obtaining the flap. The rats were distributed into 2 homogeneous groups: group 1 underwent both surgery and the use of HVES, whereas group 2 underwent just the surgery (control). Electrical stimulation was applied immediately after surgery and for 2 consecutive days. The percentage of necrotic area was analyzed using the Image J software, and blood flow was assessed by infrared thermography in different regions of the flap, divided into 4 zones according to the proximity of the pedicle of the inferior epigastric artery.

RESULTS

The results were analyzed using a Student t test, where group 1 experienced a necrotic area of 26.2%, and group 2 had an area of 54.5%. Regarding the temperature, the 2 groups showed increase in the minimum and maximum temperature on the fourth postoperative day.

CONCLUSION

The HVES appeared to have a positive influence on the viability of the flap.

Application of Epineural Sheath as a Novel Approach for Fat Volume Maintenance

INTRODUCTION

Various methods have been suggested to improve fat graft survival and decrease graft loss. The exact mechanism of fat graft survival is still unclear, and new strategies are needed to further investigate it.

MATERIALS AND METHODS

The efficacy of epineural sheath in fat volume maintenance was tested in rat model. Five experimental groups were created: group 1, fat graft without any coverage; group 2, epineural sheath tube alone; group 3, epineural sheath tube filled with fat graft; group 4, fat graft mixed with minced epineural sheath without any coverage; and group 5, fat graft covered with the epineural sheath patch. All grafts were implanted into the dorsal subcutaneous region and were followed for up to 12 weeks, when samples were harvested for hematoxylin and eosin and immunostaining for vascular endothelial growth factor expression and perilipin evaluation of fat viability.

RESULTS

In groups 1 and 4, over 25% of graft loss was observed at first week, over 50% at third week, and 100% at sixth week postimplantation. The weight of fat graft within the epineural sheath tube and the weight of epineural tube (ET) alone were maintained up to 12 weeks postimplantation. The weight of fat graft within the epineural patch was maintained up to 6 weeks, but 50% of weight loss was observed between 6 and 12 weeks. Structure of the epineural sheath tubes and patches was intact, and no leakage of fat graft was observed. Based on hematoxylin and eosin staining, normal structure and integrity of the fat graft within the ET were preserved up to 12 weeks postimplantation. Characteristic adipocyte morphology was confirmed by perilipin staining, showing viable fat cells in groups 3 and 5 at 12 weeks. Increased vascular endothelial growth factor expression was observed in groups 2, 3, 4, and 5.

CONCLUSIONS

Both, the ETs and epineural patches maintained 100% and 50% of fat graft weight at 12 weeks postimplantation, respectively. These results were confirmed by histology and immunostaining showing viable adipocytes within the epineural patches (6 weeks) and tubes (12 weeks). These results are encouraging and justify further evaluation of fat volume maintenance in preclinical large animal model in preparation to clinical application.

Laser photobiomodulation (830 and 660 nm) in mast cells, VEGF, FGF, and CD34 of the musculocutaneous flap in rats submitted to nicotine

The aim of this study was to investigate the effect of laser photobiomodulation (PBM) on the viability of the transverse rectus abdominis musculocutaneous (TRAM) flap in rats subjected to the action of nicotine. We evaluated 60 albino Wistar rats, divided into six groups of ten animals. Group 1 (saline) underwent the surgical technique to obtain a TRAM flap; group 2 (laser 830 nm) underwent the surgical technique and was irradiated with a laser 830 nm; group 3 (laser 660 nm) underwent the surgical technique and was irradiated with a laser 660 nm; group 4 was treated with nicotine subcutaneously (2 mg/kg/2×/day/4 weeks) and underwent surgery; group 5 (nicotine + laser 830 nm) was exposed to nicotine, underwent the surgical technique, and was irradiated with a laser 830 nm; group 6 (nicotine + laser 660 nm) was exposed to nicotine, underwent the surgical technique, and was irradiated with a laser 660 nm. The application of PBM occurred immediately after surgery and on the two following days. The percentage of necrosis was assessed using the AxioVision® software. The number of mast cells (toluidine blue staining) was evaluated, and immunohistochemistry was performed to detect vascular endothelial growth factor expression (anti-VEGF-A), fibroblasts (anti-basic FGF), and neoformed vessels (anti-CD34). PBM with a wavelength of 830 nm increased the viability of the TRAM flap, with a smaller area of necrosis, increased number of mast cells, and higher expression of VEGF and CD34. PBM increases the viability of musculocutaneous flaps treated with to nicotine.

Use of Systemic Rosmarinus Officinalis to Enhance the Survival of Random-Pattern Skin Flaps

BACKGROUND

Skin flaps are commonly used in soft-tissue reconstruction; however, necrosis can be a frequent complication. Several systemic and local agents have been used in attempts to improve skin flap survival, but none that can prevent flap necrosis have been identified.

AIMS

This study aims to determine whether the use of systemic Rosmarinus officinalis (R. officinalis) extract can prevent flap necrosis and improve skin flap recovery.

STUDY DESIGN

Animal experimentation.

METHODS

Thirty-five Wistar albino rats were divided in five groups. A rectangular random-pattern flaps measuring 8×2 cm was elevated from the back of each rat. Group I was the control group. In Group II, 0.2 ml of R. officinalis oil was given orally 2h before surgery. R. officinalis oil was then applied orally twice a day for a week. In Group III, R. officinalis oil was given orally twice a day for one week before surgery. At the end of the week, 0.2 mL of R. officinalis oil was given orally 2 h before surgery. In Group IV, 0.2 mL of R. officinalis oil was injected subcutaneously 2 h before surgery. After the surgery, 0.2 mL R. officinalis oil was injected subcutaneously twice a day for one week. In Group V, 0.2 mL R. officinalis oil was injected subcutaneously twice a day for one week prior to surgery. At the end of the week, one last 0.2 mL R. officinalis oil injection was administered subcutaneously 2 h before surgery. After the surgery, 0.2 mL R. officinalis oil was injected subcutaneously twice a day for one week.

RESULTS

The mean percentage of viable surface area was significantly greater (p<0.05) in Groups II, III, IV, and V as compared to Group I. Mean vessel diameter was significantly greater (p<0.05) in Groups II, III, IV, and V as compared to Group I.

CONCLUSION

We have determined that, in addition to its anti-inflammatory and anti-oxidant effects, R. officinalis has vasodilatory effects that contribute to increased skin flap survival.

Effects of diammonium glycyrrhizinate on random skin flap survival in rats: An experimental study

Partial necrosis of skin flaps continues to restrict the survival of local skin flaps following plastic and reconstructive surgeries. The aim of the present study was to investigate the effects of diammonium glycyrrhizinate (DG), a salt of glycyrrhetinic acid that has been widely used in the therapy of chronic hepatitis and human immunodeficiency virus infection, on random skin flap survival in rats. McFarlane flaps were established in 60 male Sprague-Dawley rats randomly divided into three groups. Group I served as the control group and was injected with saline (10 mg/kg) once per day. Group II and group III were the experimental groups, and were injected with 10 mg/kg DG once and twice per day, respectively. On day 7, the survival area of the flap was measured. Tissue samples were stained with hematoxylin and eosin and immunohistochemically evaluated. Tissue edema, neutrophil density, superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels were evaluated. The mean survival areas of the flaps of group II were significantly larger when compared with those of group I (P<0.05), and the rats of group III exhibited significantly higher survival areas than group II (P<0.05). Histologic and immunohistochemical evaluation showed that microvessel development and the expression level of vascular endothelial growth factor were higher in the two experimental groups than in the control group. Furthermore, SOD activity was significantly increased (P<0.05), while the neutrophil density and MDA level were significantly reduced (P<0.05) in group II when compared with group I. Significant differences between group II and group III with regard to SOD activity and MDA level were also observed (P<0.05). Thus, DG may have a dose-dependent effect on promoting the survival of random skin flaps.

Combination of ischemic preconditioning and postconditioning can minimise skin flap loss: experimental study

OBJECTIVES

Ischaemic preconditioning and postconditioning, which consist of one or a series of short ischaemic events. This study aimed to determine the efficiency of post-conditioning a flap in the minimisation of flap loss after a preconditioned skin flap.

METHODS

The rats were divided into five groups: sham group, control group, pre-con group, post-con group, and pre + post-con group. On postoperative days 3 and 7, the entire flaps along with the margins of necrosis were traced onto transparent sheets. The areas of intact skin and tissue were recorded.

RESULTS

The flap necrosis area and percentage of necrosis were calculated for each animal. The necrotic area percentage of the control group was found to be significantly higher than those of the other groups on Days 3 and 7 (p = 0.01 and p = 0.03, respectively). The necrotic area percentage of the pre-con group was significantly higher than the pre + post-con group on Day 7 (p = 0.01). VEGFR-3 expression was observed at a rate of more than 50% in the post-con group. The presence of a protective effect in the late period was separately investigated by immunohistochemical staining of VEGFR-3 in the proliferating vessels. The necrotic areas was reduced in the flaps of the pre-con, post-con, and pre + post-con groups and the combined preconditioning and postconditioning group has reduced necrotic area compared to preconditioning of the skin flap.

CONCLUSION

The protective effect was observed on day 7 for combined ischaemic preconditioning and postconditioning. The presence of a protective effect in the late period was separately investigated by immunohistochemical staining of VEGFR-3 in the proliferating vessels.

Role of adipose-derived stromal cells in pedicle skin flap survival in experimental animal models

The use of skin flaps in reconstructive surgery is the first-line surgical treatment for the reconstruction of skin defects and is essentially considered the starting point of plastic surgery. Despite their excellent usability, their application includes general surgical risks or possible complications, the primary and most common is necrosis of the flap. To improve flap survival, researchers have used different methods, including the use of adipose-derived stem cells, with significant positive results. In our research we will report the use of adipose-derived stem cells in pedicle skin flap survival based on current literature on various experimental models in animals.

The effect of adipose stromal vascular fraction on transverse rectus abdominis musculocutaneous flap: an experimental study

BACKGROUND

Transverse rectus abdominis musculocutaneous (TRAM) flap is one of the options in reconstruction after breast cancer surgery for breast reconstruction. Tissue necrosis often occurs in the third and fourth perfusion zones of the flap. A study was planned to find out the effects of adipose stromal vascular fraction (SVF) cells on viability of TRAM flap and the experimental model was designed to be applicable in clinical practice.

METHODS

Right inferior epigastric artery pedicled, 5 × 2.5 cm sized TRAM flap was used as a flap model in 30 rats in three groups (group 1: sham; group 2: phosphate-buffered saline (PBS); group 3: SVF cell injected). The viability of the flaps were assessed on the postoperative 7th day with photographs and software for the calculations.

RESULTS

The mean viable flap percentage to total flap area was recorded as 51.8% ± 11.19, 49.5% ± 10.30, 82.3% ± 9.56, in group 1, group 2, and group 3, respectively (p < 0.05). The mean capillary density was noted as 5.15 ± 0.56, 4.37 ± 0.58, and 12.40 ± 1.17 in groups 1, 2, and 3, respectively (p < 0.05). The fibrosis gradient indicated no difference between the groups (p > 0.05). The in-vivo differentiation of SVF cells to endothelial cells was noted. The blood VEGF levels showed a marked increase in the experimental group (p < 0.05).

CONCLUSION

The adipose SVF cells were found out to improve the TRAM flap viability and decrease necrosis, especially in zone 3 and 4.

Improvement in autologous human fat transplant survival with SVF plus VEGF-PLA nano-sustained release microspheres

Early neovascularization is important for autologous fat transplant survival. SVF cells are ideal seed cells. Both vascular endothelial growth factor (VEGF) and SVF cells can promote neovascularization. However, the half-life (about 50 min) of VEGF is too short to sustain an adequate local concentration. We have investigated whether VEGF-polylactic acid (PLA) nano-sustained release microspheres plus SVF cells can improve neovascularization and survival of transplanted fat tissues. SVF cells were harvested and constructed VEGF-PLA nano-sustained release microspheres in vitro. Human fat tissues was mixed with SVF cells plus VEGF-PLA, SVF cells alone or Dulbecco's modified Eagle's medium as the control. These three mixtures were injected into random sites in 18 nude mice. Two months later, the transplants were weighed and examined histologically; and capillaries were counted to quantify neovascularization. Hematoxylin-eosin (HE) and anti-VEGF stains were applied to reveal cell infiltration. The mean wet weight of fat in the SVF plus VEGF-PLA, SVF alone, and control transplants were 0.18 ± 0.013 g, 0.16 ± 0.015 g, and 0.071 ± 0.12 g, respectively; the differences between groups were statistically significant. More vessels were present in the SVF plus VEGF-PLA transplants than in the other two types. Transplants mixed with SVF cells also had an acceptable density of capillaries. Histological analysis revealed that both the SVF plus VEGF-PLA and SVF alone transplants, but not the control transplants, were composed of adipose tissue, and had less fat necrosis and less fibrosis than control specimens. SVF plus VEGF-PLA transplants had significantly greater capillary density and VEGF expression than the other two transplant groups. Thus transplanted fat tissue survival and quality can be enhanced by the addition of VEGF-PLA nano-sustained release microspheres plus SVF cells.

Effects of traditional Chinese medicine Shuxuetong injection on random skin flap survival in rats

Background. A Shuxuetong injection is traditionally used in Chinese medicine to treat “blood stasis and stagnation” (yu xue yu zhi). We investigated the effect of such injection on the survival of random skin flaps. Methods. McFarlane flaps were established in 60 rats divided into two groups. Postoperative celiac injections were given to both groups for 7 days. Shuxuetong was injected into the test group, and saline was injected into controls. On day 7, tissues were stained with H&E (hematoxylin-eosin) stain, immunohistochemically evaluated, and the expression levels of xanthine oxidase were determined. Result. The mean area of flap survival in the test group was significantly higher than in controls. Expression of vascular endothelial growth factor and superoxide dismutase, and microvessel development, were markedly increased in the test group, and the malondialdehyde level was reduced. Conclusion. Shuxuetong promotes random skin flap survival.

In situ transverse rectus abdominis myocutaneous flap: a rat model of myocutaneous ischemia reperfusion injury

Free tissue transfer is the gold standard of reconstructive surgery to repair complex defects not amenable to local options or those requiring composite tissue. Ischemia reperfusion injury (IRI) is a known cause of partial free flap failure and has no effective treatment. Establishing a laboratory model of this injury can prove costly both financially as larger mammals are conventionally used and in the expertise required by the technical difficulty of these procedures typically requires employing an experienced microsurgeon. This publication and video demonstrate the effective use of a model of IRI in rats which does not require microsurgical expertise. This procedure is an in situ model of a transverse abdominis myocutaneous (TRAM) flap where atraumatic clamps are utilized to reproduce the ischemia-reperfusion injury associated with this surgery. A laser Doppler Imaging (LDI) scanner is employed to assess flap perfusion and the image processing software, Image J to assess percentage area skin survival as a primary outcome measure of injury.

Tissue engraftment of hypoxic-preconditioned adipose-derived stem cells improves flap viability

Adipose-derived stem cells (ASCs) have the ability to release multiple growth factors in response to hypoxia. In this study, we investigated the potential of ASCs to prevent tissue ischemia. We found conditioned media from hypoxic ASCs had increased levels of vascular endothelial growth factor (VEGF) and enhanced endothelial cell tubule formation. To investigate the effect of injecting rat ASCs into ischemic flaps, 21 Lewis rats were divided into three groups: control, normal oxygen ASCs (10(6) cells), and hypoxic preconditioned ASCs (10(6) cells). At the time of flap elevation, the distal third of the flap was injected with the treatment group. At 7 days post flap elevation, flap viability was significantly improved with injection of hypoxic preconditioned ASCs. Cluster of differentiation-31-positive cells were more abundant along the margins of flaps injected with ASCs. Fluorescent labeled ASCs localized aside blood vessels or throughout the tissue, dependent on oxygen preconditioning status. Next, we evaluated the effect of hypoxic preconditioning on ASC migration and chemotaxis. Hypoxia did not affect ASC migration on scratch assay or chemotaxis to collagen and laminin. Thus, hypoxic preconditioning of injected ASCs improves flap viability likely through the effects of VEGF release. These effects are modest and represent the limitations of cellular and growth factor-induced angiogenesis in the acute setting of ischemia.

Effect of preoperative subcutaneous platelet-rich plasma and fibrin glue application on skin flap survival

BACKGROUND

The aim of this study was to compare the effects of preoperative subcutaneous platelet-rich plasma and fibrin glue administration on skin flap survival.

METHODS

One week before surgery; saline, platelet-rich plasma, fibrin glue, and thrombin solutions were applied under rat skin flap areas in Groups I, II, III, and IV, respectively. Unipedicled epigastric flaps were elevated in the first three groups but could not be elevated in Group IV because of preoperative abdominal skin necrosis. Necrotic area measurements, microangiography, and histological and immunohistochemical evaluations were performed.

RESULTS

Platelet-rich plasma reduced the percentage of necrotic area when compared to other groups. Histologically and microangiographically an increased number of arterioles were observed in the platelet-rich plasma group. Thrombin (when used alone) caused abdominal skin necrosis. Increased expression of VEGF and PDGF was found in all platelet-rich plasma-treated flaps. There was no significant difference between groups with respect to TGF-β3 staining intensity.

CONCLUSION

In this study preoperative administration of platelet-rich plasma mimicked the pharmacological delay effect and enhanced flap survival. Individual use of thrombin was found to be unsuitable in flap surgery.

LEVEL OF EVIDENCE I

This journal requires that authors assign a level of evidence to each article.

Vascular endothelial growth factor expression following ischemic conditioning of the gastric conduit

The partial devascularization of the stomach, necessary for esophageal reconstruction with a gastric conduit, impairs microcirculation in the anastomotic region of the gastric fundus. Ischemic conditioning of the gastric tube is considered as a possible approach to improve microcirculation in the gastric mucosa. The aim of this study was to investigate whether ischemic conditioning induces neo-angiogenesis in the gastric fundus by expression of vascular endothelial growth factor (VEGF). Twenty patients with an esophageal carcinoma scheduled for esophagectomy and gastric reconstruction were included. To compare VEGF expression before and after ischemic conditioning, preoperative endoscopic biopsies were taken from the gastric fundus. The surgical procedure consisted of two separate steps, the complete gastric mobilization including partial devascularization of the stomach and after a delay of 4-5 days high transthoracic esophagectomy with intrathoracic gastric reconstruction (Ivor-Lewis procedure). The second tissue sample was obtained from the donut of the stapled esophagogastrostomy. For further work-up, preoperative biopsies and the gastric donuts were fixed in liquid nitrogen. Preoperative and intraoperative VEGF expression was measured by quantitative real-time reverse transcription-polymerase chain reaction (VEGF×100/β-actin) and results were compared using Wilcoxon test for paired samples. In all 40 specimens, a distinct expression of VEGF could be detected. Comparing the level of VEGF expression of the preoperative biopsies and postoperative tissue sample, no significant difference could be demonstrated following ischemic conditioning. In this model of ischemic conditioning with delayed reconstruction of 4-5 days, no induction of neo-angiogenesis could be demonstrated by measurement of VEGF expression.

Improvement of a long random skin flap survival by application of vascular endothelial growth factor in various ways of local administration in a rat model

Background:

Vascular endothelial growth factor (VEGF) is a heparin-binding glycoprotein which plays a significant role in angiogenesis and vascular permeability. The effect of various ways of local administration of VEGF on random skin flap survival was studied, using flaps with a relatively high length (L) to width (W) ratio (5:1).

Materials and Methods:

An 1.5 × 7.5 cm dorsal skin flap with the pedicle orientated, centered, and remaining attached between the lower angles of the scapulae was elevated in 45 Wistar rats in different phases, depending on the group. Rats were divided in five groups of nine. In group A, injections of saline were administered, in equally divided spaces, into flap's fascia and transposed to a created skin defect. In group B, injections of VEGF were applied subdermally, in equally divided spaces, within the limits of a predesigned flap, a week prior to flap dissection and transposition. In group C, injections of VEGF were applied into a recipient bed's fascia just before flap raising and transposition. In group D, injections of VEGF were applied subdermally, only in the distal third of the flap and then the flap was transposed to a recipient area. Finally, in group E, injections of VEGF were applied in the flap intrafascially and in equally divided spaces and then again, the flap was transposed to a recipient area. A week after final flap raising and positioning, rats were euthanatised and flaps were excised. Specimens were photographed, measured, put in formalin 10% and were sent for histological and image analysis.

Results:

Mean flap survival percentage was 35.4% in group A, and 33.7% in group B. In groups C and D, the mean survival area was 56.3% and 80.4%, respectively. In group E, the mean flap survival percentage was 28.3%. Histological analysis demonstrated increased angiogenesis in groups C and D.

Conclusions:

VEGF application improved skin flap survival when injected subdermally in the distal third of a random skin flap or into the fascia of a recipient area even though the length-to-width ratio was high.

Importance of mesenchymal stem cells in autologous fat grafting: a systematic review of existing studies

Autologous fat grafting (lipofilling) enables repair and augmentation of soft tissues and is increasingly used both in aesthetic and reconstructive surgery. Autologous fat has several advantages, including biocompatibility, versatility, natural appearance, and low donor site morbidity. The main limitation is unpredictable graft resorption, which ranges from 25%-80%, probably as a result of ischaemia and lack of neoangiogenesis. To obviate these disadvantages, several studies have searched for new ways of increasing the viability of the transplanted tissue. One promising approach has been to enrich the fat graft with adipose tissue-derived mesenchymal stem cells (ASC) before transplantation. We have reviewed original studies published on fat transplantation enriched with ASC. We found four murine and three human studies that investigated the subject after a sensitive search of publications. In the human studies, so-called cell assisted lipotransfer (CAL) increased the ASC concentration 2-5 times compared with non-manipulated fat grafts, which caused a questionable improvement in survival of fat grafts, compared with that of traditional lipofilling. In contrast, in two of the murine studies ASC-concentrations were increased 1250 and 6250 times, respectively, by ASC ex vivo expansion, which resulted in considerably improved fat transplant survival as well as quality. This effect of high-level enrichment with ASC is thought to have been caused by paracrine signalling, cellular differentiation, or both. The surgical and tissue handling techniques used in lipofilling are well proved, but the added effect of high-level enrichment with ex vivo expanded ASC still needs to be investigated properly in human lipofilling studies, combined with a thorough follow up and matched control groups. In conclusion, ASC-enriched lipofilling theoretically has the potential for transforming lipofilling from a relatively unpredictable intervention into one in which the resorption rate, quality of tissue, and safety can be predicted, and possibly superior to prosthetic implantation.

Improvement of the skin flap survival with the bone marrow-derived mononuclear cells transplantation in a rat model

Partial necrosis of skin flaps remains a significant problem in plastic and reconstructive surgery. In this study we attempted to evaluate the effect of bone marrow-derived mononuclear cells (BM-MNCs) transplantation on improvement of skin flap survival in a rat random pattern skin flap model. Thirty Wistar rats were divided into three groups with each consisting of 10 rats. BM-MNCs and the adipose-derived stem cells (ADSCs) were transplanted into the subcutaneous tissue in the area where the flap would be dissected. The flaps were then raised two days after cells transplantation. The animals receiving the preoperative Dulbecco's Modified Eagle Medium (DMEM) treatment were used as the controls. On the 7th postoperative day, the survival areas of flaps were measured and tissues were collected for examinations. The results showed that the mean survival areas were 46.33 +/- 13.46% in the ADSCs group and 50.06 +/- 13.82% in the BM-MNCs group as the percentages of the total skin flaps, which were significantly higher than that in the control group (26.33 +/- 7.14%) (P < 0.05). Histological analysis showed increased neovascularization in the flap treated with BM-MNCs when compared with ADSCs transplantation. Survival BM-MNCs and ADSCs were detected in the flap tissues. Higher levels of the basic fibroblast growth factor (bFGF) and vascular endothelium growth factor (VEGF) were found in the BM-MNCs transplantation group (P < 0.05). The findings from this study demonstrated that preoperative treatment with BM-MNCs transplantation could promote neovascularization and improve flap survival. These effects of BM-MNCs on flap survival were comparable with ADSCs transplantation, but without necessity of in vitro cells expansion.

Role of Growth Factors in Improved Skin Flap Viability Caused by Phosphodiesterase-5 Inhibitor

Flap necrosis is one of the major complications of reconstructive surgery and sildenafil citrate has been shown to decrease flap necrosis in preclinical animal models. However, the mechanisms underlying sildenafil's therapeutic efficacy are not known. As with other phosphodiesterase 5 selective inhibitors, sildenafil causes vasodilation and enhanced blood flow. In addition, sildenafil can also alter gene expression. This study is designed to test the hypothesis that increased expression of angiogenic growth factors may be responsible for therapeutic efficacy of sildenafil. A modified McFarlane flap measuring 3 X 10 cm was created on the dorsal skin of male Sprague-Dawley rats. For growth factor expression experiment, rats were administered either vehicle or sildenafil 10 mg/Kg intraperitoneal (IP). Ribonucleic acid (RNA) extracted from skin flap was analyzed to assess the messenger ribonucleic acid (mRNA) levels of different angiogenic growth factors. For skin flap viability experiment, fibrin film impregnated with vehicle, fibroblast growth factor (FGF) (5.0 μg) or vascular endothelial growth factor (VEGF) (2.0 μg) was applied to the wound. The skin flap was then returned to its native position and stapled in place. Total affected area (area of necrosis and blood flow stasis) of each rat on postoperative day 14 was analyzed with orthogonal polarization spectral imaging. Daily systemic treatment with sildenafil significantly ( P < 0.05) increased the expression of FGF1 and FGF Receptor 3 on postoperative day 3 by 5.08- and 4.78-fold, respectively. In addition, sildenafil increased the expression of VEGF-A, VEGF-B, and VEGF-C by 2.66-, 2.02-, and 2.00-fold, respectively. Subcutaneous treatment with FGF but not VEGF-A tended to decrease total affected area in rats. These data demonstrate that sildenafil altered the expression of FGF and VEGF. Altered expression of growth factors may be, at least partly, responsible for the beneficial effects of sildenafil citrate on skin viability.

Improvement of the survival of human autologous fat transplantation by using VEGF-transfected adipose-derived stem cells

BACKGROUND

The efficacy of autologous fat transplantation is reduced by fat absorption and fibrosis due to fat necrosis. Enhanced transplant neovascularization early after transplantation may reduce these outcomes. The authors asked whether cell and concomitant gene therapy using adipose-derived stem cells transduced with vascular endothelial growth factor (VEGF) improves fat transplant neovascularization and survival.

METHODS

Human adipose-derived stem cells were expanded ex vivo for three passages, labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine (DiI), and transduced with VEGF or left untransduced. Human fat tissues were then mixed with the DiI-labeled VEGF-transduced adipose-derived stem cells, the DiI-labeled adipose-derived stem cells, the known vascularization-promoting agent insulin, or medium alone, and 18 nude mice were injected subcutaneously with all four preparations, with each of the four designated spots receiving one of these four mixtures in a random fashion. Six months later, transplanted tissue volume and histology were evaluated and neovascularization was quantified by counting the capillaries.

RESULTS

Control transplant survival was 27.1 +/- 8.2 percent, but mixture with the VEGF-transduced and VEGF-untransduced stem cells significantly increased transplant survival (74.1 +/- 12.6 percent and 60.1 +/- 17.6 percent, respectively). Insulin was less effective (37.7 +/- 6.9 percent). Histological analysis revealed both types of transplants consisted predominantly of adipose tissue, unlike the control transplants, and had significantly less fat necrosis and fibrosis. The VEGF-transduced, adipose-derived stem cell-treated transplants had significantly higher capillary density than the other transplants and bore DiI-double-positive and CD31-double-positive cells (i.e., adipose-derived stem cell-derived endothelial cells).

CONCLUSION

Adipose-derived stem cells together with VEGF transduction can enhance the survival and quality of transplanted fat tissues.

Angiogenesis and plastic surgery

SUMMARY

Angiogenesis, the formation of new blood vessels from an existing vascular bed, is a normal physiological process which also underpins many--apparently unrelated--pathological states. It is an integral factor in determining the success or failure of many procedures in plastic and reconstructive surgery. As a result, the ability to control the process would be of great therapeutic benefit. To appreciate the potential benefits and limitations of recent advances in our understanding of angiogenesis, it is important to comprehend the basic physiology of blood vessel formation. This review aims to summarise current knowledge of the way in which angiogenesis is controlled and to look at how disordered vessel development results in pathology relevant to plastic surgery. Through this we hope to provide a comprehensive overview of the recent advances in angiogenesis as they relate to plastic surgery, particularly the promotion of flap survival, tendon healing, nerve regeneration, fracture healing and ulcer treatments.

Improved viability of random pattern skin flaps through the use of adipose-derived stem cells

BACKGROUND

Flap necrosis caused by inadequate blood supply is a common postoperative complication in reconstructive surgery. Because a putative stem cell population within the adipose tissue has been found to possess angiogenic potential, the authors sought to determine whether these cells might selectively induce neovascularization and increase the viability of random pattern skin flaps.

METHODS

Adipose-derived stem cells were isolated from the inguinal fat pads of ICR mice and expanded ex vivo for three passages. After the elevation of cranially based random pattern skin flaps (3 cm long and 1 cm wide), 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine (DiI)-labeled adipose-derived stem cells were then injected into the pedicle base (group A) or 1.5 cm distal to the pedicle (group B). Medium containing no adipose-derived stem cells, mature adipocytes, or basic fibroblast growth factor were injected in three other control groups separately (n = 10 for each group). Millimetric measurements were taken at postoperative day 7 for evaluation of flap viability. Specimens were harvested for histologic analyses.

RESULTS

Adipose-derived stem cells led to a statistically significant increase in flap viability in both group A and group B compared with the control and the adipocyte groups. Histologic examination also demonstrated a statistically significant increase in capillary density in both group A and group B. Moreover, some of the endothelial cells were stained positively for DiI.

CONCLUSIONS

These findings suggest that adipose-derived stem cells have a potential for enhancing the blood supply of random pattern skin flaps. This mechanism might be both the direct differentiation of adipose-derived stem cells into endothelial cells and the indirect effect of angiogenic growth factor released from adipose-derived stem cells.

Mesenchymal stem cells transduced by vascular endothelial growth factor gene for ischemic random skin flaps

BACKGROUND

Vascular endothelial growth factor (VEGF) plays an important role in inducing angiogenesis. Mesenchymal stem cells may have the potential for differentiation into several types of cells, including vascular endothelial cells. In this study, the authors explored the feasibility of applying mesenchymal stem cells transduced by the VEGF gene to the treatment of ischemic random skin flaps.

METHODS

Mesenchymal stem cells were isolated from Sprague-Dawley rat bone marrow and cultured in vitro. Plasmid pcDNA3.1(-)/VEGF165 containing the VEGF gene was transduced into the mesenchymal stem cells by liposome. The mesenchymal stem cells were stained with chloromethyl-1-1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanineperchlorate before the transplantation. Thirty rats were randomized into three groups. Groups A, B, and C were injected with mesenchymal stem cells transduced with pcDNA3.1(-)/VEGF165 plasmid, mesenchymal stem cells, and medium only, respectively. On the fourth day after injection, random dorsal skin flaps measuring 9 x 2 cm were elevated. The survival, neovascularization, and blood flow recovery of the flaps were detected.

RESULTS

VEGF-transduced mesenchymal stem cells expressed VEGF highly in vitro and in vivo. Transplanted mesenchymal stem cells survived and incorporated into the capillary networks in the ischemic rat flaps. The viability measurements showed an increased percentage flap survival in group A (83.1 +/- 2.6 percent) as compared with either group B (66.4 +/- 6.1 percent) or group C (51.5 +/- 7.5 percent) (p < 0.01). The capillary density and the blood perfusion of the flaps in the experimental group were significantly higher than those in the other two groups (p < 0.01).

CONCLUSION

VEGF-transduced mesenchymal stem cells can increase ischemic flap neovascularization and augment the surviving areas.

Selective Percutaneous Desiccation of the Perforators with Radiofrequency for Strategic Transfer of Angiosomes in a Sequential Four-Territory Cutaneous Island Flap Model

BACKGROUND

Research in prevention of partial flap necrosis has recently concentrated on extending the safe length of a flap by ligating vessels of known territories. To advance this approach one step further, the authors decided to reveal the least invasive surgical strategy for transfer of angiosomes.

METHODS

The study was arranged into three experiments. In the first experiment (n = 17 rabbits), a cutaneous island flap model spanning four adjacent vascular territories was developed. In the second experiment (n = 15 rabbits), the flap model was used to test the possibility of desiccating those vessels supplying the angiosomes to be captured percutaneously with radiofrequency. The delay procedures were performed by means of minimal skin incisions, and the flaps were elevated after a 2-week delay period. In the third experiment, the effectiveness of selective interference of these pedicles was compared to minimize the number of target vessels for successful transfer of angiosomes.

RESULTS

The mean surviving area of the new flap model was 63 +/- 2 percent. The mean surviving flap area was 97 +/- 3 percent for the endoscopy equivalent technique and 94 +/- 4 percent for radiofrequency delay. The results were statistically insignificant between these two groups. In experiment 3, comparison of the results yielded a statistically insignificant difference for flap survival area among all four of the groups.

CONCLUSIONS

An alternative flap model is introduced for future investigation of the vascular delay process. Percutaneous desiccation of the perforators with radiofrequency was found to be a reliable method, and selective desiccation of the perforator(s) was as efficient as destruction of all vascular sources other than the pedicle.

Improved survival of rat ischemic cutaneous and musculocutaneous flaps after VEGF gene transfer

When harvesting microsurgical flaps, the main goals are to obtain as much tissue as possible based on a single vascular pedicle and a reliable vascularization of the entire flap. These aims being in contrast to each other, microsurgeons have been looking for an effective way to enhance skin and muscle perfusion in order to avoid partial flap loss in reconstructive surgery. In this study we demonstrate the efficacy of VEGF 165 delivered by an Adeno-Associated Virus (AAV) vector in two widely recognized rat flap models. In the rectus abdominis myocutaneous flap, intramuscular injection of AAV-VEGF reduced flap necrosis by 50%, while cutaneous delivery of the same amount of vector put down the epigastric flap's ischemia by >40%. Histological evidence of neoangiogenesis (enhanced presence of CD31-positive capillaries and alpha-Smooth Muscle Actin-positive arteriolae) confirmed the therapeutic effect of AAV-VEGF on flap perfusion.

Efficacy and mechanism of adenovirus-mediated VEGF-165 gene therapy for augmentation of skin flap viability

Skin ischemic necrosis due to vasospasm and/or insufficient vascularity is the most common complication in the distal portion of the skin flap in reconstructive surgery. This project was designed to test our hypothesis that preoperative subdermal injection of adenoviral vectors encoding genes for vascular endothelial growth factor-165 (Ad.VEGF-165) or endothelial nitric oxide (NO) synthase (Ad.eNOS) effectively augments skin viability in skin flap surgery and that the mechanism of Ad.VEGF-165 gene therapy involves an increase in synthesis/release of the angiogenic and vasodilator factor NO. PBS (0.5 ml) or PBS containing Ad.VEGF-165, Ad.eNOS, or adenovirus (Ad.Null) was injected subdermally into the distal half of a mapped rat dorsal skin flap (4 × 10 cm) 7 days preoperatively, and skin flap viability was assessed 7 days postoperatively. Local subdermal gene therapy with 2 × 107–2 × 1010 plaque-forming units of VEGF-165 increased skin flap viability compared with PBS- or Ad.Null-injected control ( P < 0.05). Subdermal Ad.VEGF-165 and Ad.eNOS gene therapies were equally effective in increasing skin flap viability at 5 × 108 plaque-forming units. Subdermal Ad.VEGF-165 therapy was associated with upregulation of eNOS protein expression, Ca2+-dependent NOS activity, synthesis/release of NO, and increase in capillary density and blood flow in the distal portion of the skin flap. Injection of the NOS inhibitor Nω-nitro-l-arginine (15 mg/kg im), but not the cyclooxygenase inhibitor indomethacin (5 mg/kg im), 45 min preoperatively completely abolished the increase in skin flap blood flow and viability induced by Ad.VEGF-165 injected subdermally into the mapped skin flap 7 days preoperatively. We have demonstrated for the first time that 1) Ad.VEGF-165 and Ad.eNOS mapped skin flap injected subdermally into the mapped skin flap 7 days preoperatively are equally effective in augmenting viability in the rat dorsal skin flap compared with control, 2) the mechanism of subdermal Ad.VEGF-165 gene therapy in augmenting skin flap viability involves an increase in NO synthesis/release downstream of upregulation of eNOS protein expression and Ca2+-dependent NOS activity, and 3) the vasodilating effect of NO may predominantly mediate subdermal Ad.VEGF gene therapy in augmenting skin flap blood flow and viability.

Improvement of Venous Flap Survival by Application of Vascular Endothelial Growth Factor in a Rat Model

Expression of vascular endothelial growth factor (VEGF) in the venous flap and the effect of exogenous VEGF on survival of the venous flap were studied in rats. A 4- x 4-cm groin type 2 venous skin flap was used in the study. In part 1, biopsies were taken from the flap at 0, 6, 12, 24, and 48 hours after the flaps were raised. VEGF gene expression was measured. In part 2, exogenous VEGF (1 microg/mL) was injected subdermally into the flaps in 10 rats before the flaps were replaced. Flaps that received a saline injection were used as the control. Skin paddle survival was measured on postoperative day 7. The results showed that VEGF expression was significantly increased at 24 and 48 hours after venous flap elevation (P < 0.05). Injection of exogenous VEGF to the flap significantly improved survival of the flap (73% of the flap) when compared with the control, which had a 39% mean percent survival (P < 0.05). We conclude that VEGF expression was increased in the venous flap. Administration of exogenous VEGF significantly improved survival of the venous flap.