Adenovirus-mediated transforming growth factor-beta ameliorates ischemic necrosis of epigastric skin flaps in a rat model

BACKGROUND: Gene therapy has been recently introduced as a novel approach to treat ischemic tissues by using the angiogenic potential of certain growth factors. We investigated the effect of adenovirus-mediated gene therapy with transforming growth factor-beta (TGF-beta) delivered into the subdermal space to treat ischemically challenged epigastric skin flaps in a rat model. MATERIAL AND METHODS: A pilot study was conducted in a group of 5 animals pretreated with Ad-GFP and expression of green fluorescent protein in the skin flap sections was demonstrated under fluorescence microscopy at 2, 4, and 7 days after the treatment, indicating a successful transfection of the skin flaps following subdermal gene therapy. Next, 30 male Sprague Dawley rats were divided into 3 groups of 10 rats each. An epigastric skin flap model, based solely on the right inferior epigastric vessels, was used as the model in this study. Rats received subdermal injections of adenovirus encoding TGF-beta (Ad-TGF-beta) or green fluorescent protein (Ad-GFP) as treatment control. The third group (n = 10) received saline and served as a control group. A flap measuring 8 x 8 cm was outlined on the abdominal skin extending from the xiphoid process proximally and the pubic region distally, to the anterior axillary lines bilaterally. Just prior to flap elevation, the injections were given subdermally in the left upper corner of the flap. The flap was then sutured back to its bed. Flap viability was evaluated seven days after the initial operation. Digital images of the epigastric flaps were taken and areas of necrotic zones relative to total flap surface area were measured and expressed as percentages by using a software program. RESULTS: There was a significant increase in mean percent surviving area between the Ad-TGF-beta group and the two other control groups (P < 0.05). (Ad-TGF-beta: 90.3 +/- 4.0% versus Ad-GFP: 82.2 +/- 8.7% and saline group: 82.6 +/- 4.3%.) CONCLUSIONS: In this study, the authors were able to demonstrate that adenovirus-mediated gene therapy using TGF-beta ameliorated ischemic necrosis in an epigastric skin flap model, as confirmed by significant reduction in the necrotic zones of the flap. The results of this study raise the possibility of using adenovirus-mediated TGF-beta gene therapy to promote perfusion in random portion of skin flaps, especially in high-risk patients.     

Effect of transfection time on the survival of epigastric skin flaps pretreated with adenovirus encoding the VEGF gene

An experimental study was conducted to investigate the effect of time of adenovirus-mediated vascular endothelial growth factor (VEGF) gene therapy on the viability of epigastric skin flaps. Eighty-four male Sprague-Dawley rats were used. Skin flaps measuring 8 x 8 cm were marked on the ventral abdominal wall. The upper border of the flap was 1 cm above the costal margin, and the lower border was at the pubis and the inguinal fold. The lateral borders of the flap corresponded to the location of the distinct conversion of the thin ventral skin to the thick dorsal skin. Seven sites in the predicted area of necrosis on the outlined skin flaps were chosen for subdermal injections. All injections were administered by an individual who was blinded to the different treatment groups. The rats received either saline (control group I, N = 28) or adenovirus encoding green fluorescent protein (Ad-GFP; group II, N = 28) or Ad-VEGF (group III, N = 28). The epigastric island skin flaps based solely on the right inferior epigastric vessels were elevated either on the same day of injection (day 0 = 12 hours after transfection, N = 7) or on day 3 (N = 7), day 7 (N = 7), or day 14 (N = 7) after subdermal gene therapy. Flaps were sutured back to their native configuration. Flap viability was evaluated on day 7 after surgery. Sections of the flaps were examined histologically after undergoing hematoxylin-eosin staining. There was a significant reduction in mean percentage of necrotic flap area by 56%, 67%, 70%, and 54% in flaps transfected with Ad-VEGF, 12 hours, 3 days, 7 days, and 14 days before flap elevation, respectively ( < 0.05). There was no evidence that the mean percentage of skin necrosis in the Ad-GFP group was different than in the control group ( = 0.26). There was evidence of mild inflammation in flaps pretreated with Ad-GFP and Ad-VEGF compared with the control group. The authors demonstrated that adenovirus-mediated gene therapy of the abdominal skin after subdermal injections was technically feasible. This was demonstrated by the visualization of GFP expression in control experiments using a fluorescence microscope. In this study, adenovirus-mediated VEGF gene therapy promoted epigastric flap survival, which was not related to the time of transfection. These findings raise the possibility that pretreatment with VEGF gene therapy using an adenovirus vector may be applicable in patients at risk for plastic surgery.     

Comparison of the effectiveness of gene therapy with transforming growth factor-β or extracorporal shock wave therapy to reduce ischemic necrosis in an epigastric skin flap model in rats

The induction of neoangiogenesis by exogenous growth factors in failing skin flaps has recently yielded promising results. Gene transfer with virus vectors has been introduced as a highly capable route of administration for growth factors, such as vascular endothelial growth factor or fibroblast growth factor. Extracorporal shock waves (ESW) deliver energy by means of high amplitudes of sound to the target tissue and have been shown to induce angiogenesis. We compared the effectiveness of gene therapy with adenovirus-mediated transforming growth factor-beta (TGF-beta) and ESW therapy to treat ischemically challenged epigastric skin flaps in a rat model. Thirty male Sprague-Dawley rats were divided into three groups of 10 each with an 8 x 8 cm epigastric skin flap. Rats received either subdermal injections of adenovirus (Ad) encoding TGF-beta (10(8) pfu) or ESW treatment with 750 impulses at 0.15 mJ/mm2. The third group received no treatment and served as a control group. Flap viability was evaluated after 7 days and digital images of the epigastric flaps were taken and areas of necrotic zones relative to total flap surface area calculated. Histologic evaluation and increased angiogenesis were confirmed by CD31 immunohistochemistry. Overall, there was a significant increase in mean percent surviving area in the Ad-TGF-beta group and the ESW group compared to the control group (ESW group: 97.7 +/- 1.8% vs. Ad-TGF-beta: 90.3 +/- 4.0% and control group: 82.6 +/- 4.3%; p < 0.05). Furthermore, in the ESW group mean percent surviving areas were significantly larger than in the Ad-TGF-beta group (ESW group: 97.7 +/- 1.8% vs. Ad-TGF-beta: 90.3 +/- 4.0%; p < 0.05). Flap vascularization was increased by Ad-TGF-beta and ESW with numerous vessels, however, there was no significant difference between the two treatment groups. We conclude that treatment with ESW enhances epigastric skin flap survival significantly more than Ad-TGF-beta treatment and thus represents a modality that is feasible, cost-effective, and less invasive compared to gene therapy with growth factors to improve blood supply to ischemic tissue.     

Comparison of the effectiveness of gene therapy with vascular endothelial growth factor or shock wave therapy to reduce ischaemic necrosis in an epigastric skin flap model in rats.

The effect of gene therapy with adenovirus-mediated (Ad) vascular endothelial growth factor (VEGF) was compared to that of shock wave (SW) therapy on skin flap survival in a rat model, using the epigastric skin flap, based solely on the right inferior epigastric vessels. Thirty male Sprague-Dawley rats were randomly divided into three groups (SW-group, Ad-VEGF-group, and Control-group) of 10 rats each. Immediately after surgery, the SW-group was administered 2500 impulses at 0.15mJ/mm(2), in the Ad-VEGF-group injections were made to the subdermal space whereas the Control-group received no treatment. Flap viability was evaluated on day 7 after the operation. Standardised digital pictures of the flaps were taken and transferred to the computer, and necrotic zones relative to total flap surface area were measured and expressed as percentages. Overall, significantly smaller areas of necrotic zones were noted in the SW-group and the Ad-VEGF-group compared with the Control-group (SW-group: median 2.23% (range: 0-5.1) versus Control-group: median 17.4% (range: 11.8-22.8) (p<0.05); Ad-VEGF-group: median 9.25% (range: 7.6-11.9) versus Control-group: median 17.4% (range: 11.8-22.8) (p<0.05)). Furthermore, in the SW-group, areas of necrotic zones were significantly smaller than in Ad-VEGF-group (SW-group: median 2.23% (range: 0-5.1) versus Ad-VEGF-group: median 9.25% (range: 7.6-11.9) (p<0.05)). We conclude that treatment with SW enhances epigastric skin flap survival significantly more than Ad-VEGF treatment and also represents a feasible and cost effective technique to improve blood supply in ischaemic tissue.     

Effect of adenovirus-mediated gene transfection of vascular endothelial growth factor on survival of random flaps in rats

Objective: To evaluate the effect of local application of vascular endothelial growth factor ( VEGF ) via adenovirus-mediated gene transfer on survival of full thickness flaps selected randomly in rats.Methods: Thirty Sprague-Dawley rats weighing 480-520 g were used in this study. A dorsal flap (8 cm × 2 cm) in full thickness with the pedicle located at the level of the iliac crest was designed. Then the rats received 1 012 pfu replication-deficient recombinant adenovirus carrying VEGF ( AdCMV-VEGF group, n = 10 ), 1012 pfu recombinant β-galactosidase adenovirus ( AdCMV-Gal group, n = 10) and 1 ml saline (saline group, n = 10), respectively, in the distal two thirds of the proposed flap by means of subdermal injection at 8 different locations. Three days after treatment, the flaps were elevated as originally designed and sutured back in situ. The survival rate of the flaps was evaluated on day 7 after operation.Results: The survival rate of the flaps in the AdCMV-VEGF group increased significantly as     

腺病毒载体介导人VEGF cDNA促进随意型皮瓣成活的实验研究

目的探讨以腺病毒载体局部应用血管内皮细胞生长因子基因对大鼠缺血随意型皮瓣成活的影响。方法30只SD大鼠随机分成3组,每组10只,于鼠背设计蒂在尾侧髂嵴水平的随意型皮瓣,面积为2cm×8cm,A组皮瓣远端23顺皮瓣长轴分10个点真皮下注入1012PFU的携带人血管内皮细胞生长因子基因的腺病毒(AdCMVVEGF),B组同法注入同剂量的携带β半乳糖苷酶基因的腺病毒(AdCMVGal),C组注入1ml的生理盐水,3d后掀起皮瓣并原位缝合,术后7d观察实验结果。结果每组皮瓣成活面积的百分比分别为A组(8591±254)%,B组为(5956±118)%,C组为(6148±109)%,A组成活率显著高于B组和C组,差异有非常显著性意义(P<001),B组与C组比较差异无显著性意义(P>005)。原位杂交、免疫组化显示,应用AdCMVVEGF治疗的成活皮瓣中,VEGF有表达,组织学切片显示,AdCMVVEGF治疗皮瓣中肉芽组织增生,新生血管大量形成。结论以腺病毒为载体局部应用VEGF基因能增加缺血皮瓣的成活面积,该法具有高效的特点。     

大白鼠背部真皮下血管网皮瓣蒂部功能的研究

目的探讨真皮下血管网皮瓣蒂部对皮瓣成活的作用。方法以大白鼠背部真皮下血管网皮瓣为主要研究对象,相同部位的真皮下血管网皮片为对照,设计皮瓣长宽比例为4:1。皮瓣及皮片采用肉眼观察及仪器两种观察手段。将实验动物分为条件不同的3组,以毛发生长为最重要的观察指标。结果对116只大白鼠进行的实验研究,表明各组皮瓣的近端1/4生长良好。结论真皮下血管网皮瓣蒂部供血能力为皮瓣面积的1/4(长宽比为1:1)。     

大白鼠背部真皮下血管网皮瓣蒂部功能的研究

目的探讨真皮下血管网皮瓣蒂部对皮瓣成活的作用。方法以大白鼠背部真皮下血管网皮瓣为主要研究对象,相同部位的真皮下血管网皮片为对照,设计皮瓣长宽比例为４∶１。皮瓣及皮片采用肉眼观察及仪器两种观察手段。将实验动物分为条件不同的３组,以毛发生长为最重要的观察指标。结果对１１６只大白鼠进行的实验研究,表明各组皮瓣的近端１／４生长良好。结论真皮下血管网皮瓣蒂部供血能力为皮瓣面积的１／４（长宽比为１∶１）。     

大白鼠背部真皮下血管网皮瓣蒂部功能的研究

目的 探讨真皮下血管网皮瓣蒂部对皮瓣成活的作用。方法 以大白鼠背部真皮下血管网皮瓣为主要研究对象,相同部位的真皮下血管网皮片为对照,设计皮瓣长宽比例为4：1。皮瓣及皮片采用肉眼观察及仪器两种观察手段。将实验动物分为条件不同的3组,以毛发生长为最重要的观察指标。结果 对116只大白鼠进行的实验研究,表明各组皮瓣的近端1／4生长良好。结论 真皮下血管网皮瓣蒂部供血能力为皮瓣面积的1／4（长宽比为1：1）。     

Enhancement of ischemic flap survival by prefabrication with transfer of exogenous PDGF gene

Treatment of skin flaps by means of gene therapy has been introduced recently as a novel approach to enhance viability of ischemic skin flaps. Transfer of the platelet-derived growth factor (PDGF) to enhance survival of the ischemic skin flap has not been explored. In this study, the authors investigated the effect of the transfer of the PDGF cDNA on survival and vascularity of the ischemic random flap in a rat model, and compared the effects of PDGF gene therapy to those of vascular endothelial growth factor (VEGF) gene therapy. A total of 45 adult Sprague-Dawley rats were randomly divided into four groups. The PDGF gene therapy group (n=10) received the plasmid containing the PDGF cDNA with liposome injected to the dermis of the flap. A saline control group (n=10) received physiologic saline only, and the vector control group (n=10) received liposome plus vector without the PDGF gene segment. In the fourth group (n=15), the VEGF gene was transferred to the flap. Seven days later, a dorsal random flap including the injection area was raised. One rat each from the saline and vector control groups died during the study period and were excluded. The viability of the flap and vascularity within the flaps were assessed 7 days after flap elevation. The PDGF plasmid-treated flaps had significantly greater survival area (60.8+/-7.8 percent) compared with the flaps treated with saline (52.3+/-5.0 percent) and those treated with liposome and vector (50.7+/-5.9 percent). PDGF gene therapy had effects on survival of the flap similar to VEGF gene therapy (57.6+/-5.2 percent, after transfer of VEGF cDNA). Neovascularization with the flap tissues was confirmed by immunohistochemical staining of von Willebrand factor, a marker specific for angiogenesis. The number of newly-formed blood vessels in the transgenic flaps was significantly greater than that of the vessels in the flaps receiving the saline. The findings of this study indicate that transfer of the PDGF cDNA effectively enhances neovascularization of the ischemic skin flap and increases the viability of the flap, and transfer of the PDGF gene is as efficient as transfer of the VEGF gene in improving viability of the skin flap. This study suggests that PDGF gene therapy may be a novel strategy for the treatment of ischemic skin flaps.     

The effects of VEGF on survival of a random flap in the rat: examination of various routes of administration.

The purpose of the present study was to determine the effects of vascular endothelial growth factor (VEGF) on survival of a full thickness random pattern, McFarlane musculocutaneous flap in the rat. In addition, this study examined a number of different methods of VEGF delivery in an attempt to determine the most effective route of administration. A 2 x 8 cm full thickness dorsal flap with the pedicle remaining attached at the anterior end was elevated in 72 male Sprague-Dawley rats. The rats were randomised into six groups and immediately received the following treatment: Group I (n = 12): systemic VEGF injection into the femoral vein (50 microg/ml); Group II (n = 10): multiple systemic VEGF injections at 0, 24 and 48 h post flap elevation (50 microg/ml); Group III (n = 12): subdermal VEGF injection into the flap (1 microg/ml); Group IV (n = 12): subfascial VEGF injections into the recipient bed (1 microg/ml); Group V (n = 10): topical VEGF onto the recipient bed (1 microg/ml); Group VI (n = 16): control group with no treatment. Following 5 days recovery, the area of flap survival was measured. Mean flap survival ranged from 91% in Group II to 78% in Group V, and was significantly greater in all experimental groups (P< 0.001 for Groups I-IV and P< 0.05 for Group V) as compared to the control group (mean survival of 66%). The only significant difference between the experimental groups was between the mean survival in Group II and Group V (P< 0. 05). Histological analysis demonstrated a qualitatively greater amount of granulation tissue and neovascularisation in the experimental groups. These results support the notion that VEGF rescues tissue at risk of hypoxic damage by inducing angiogenesis, and the use of growth factors such as VEGF holds promise as a method of increasing skin viability.     

Extracorporal shock wave may enhance skin flap survival in an animal model.

Several methods have been used in an attempt to increase blood supply and tissue perfusion in ischemic tissues. The authors investigated the effect of extracorporal shock wave (ESW) treatment on compromised skin flaps. For this purpose, the epigastric skin flap model in rats, based solely on the right inferior epigastric vessels was used. Twenty male Sprague-Dawley rats were divided into two groups (ESW-group, Control group) of 10 rats each. The ESW-group was administered 2500 impulses at 0.15 mJ/mm(2) immediately after surgery, whereas, the control group received no treatment. Flap viability was evaluated on day 7 after the operation. Standardised digital pictures of the flaps were taken and transferred to the computer, and necrotic zones relative to total flap surface area were measured and expressed as percentages. Overall, there was a significant reduction in the surface area of the necrotic zones of the flaps in the ESW group compared to the control group (ESW group: 2.2+/-1.9% versus control: 17.4+/-4.4% (p < 0.01). In this study, the authors demonstrated that treatment with ESW enhanced epigastric skin flap survival, as confirmed by the significant reduction of necrotic flap zones. ESW treatment seems to represent a feasible and cost effective method to improve blood supply in ischemic tissue.     

The Effects of Tadalafil on Axial-Pattern Skin Flap Survival in Rats

BACKGROUND Pharmacologic augmentation to mimic the delay phenomenon that increases skin flap survival has been studied extensively. Tadalafil is a phosphodiesterase V inhibitor that is used for treatment of erectile dysfunction by enhancing vascular smooth muscle relaxation.
OBJECTIVE The aim of this study was to investigate the effects of local injection of tadalafil in enhancing axial-pattern skin flap survival in rats.
MATERIALS AND METHODS Twenty Sprague-Dawley rats were used and a McFarlane-type caudally based axial-pattern skin flap was designed on the dorsum of the rat (2 × 9 cm). Rats were divided into two groups: the treatment group and the control group. Tadalafil 10 mg/kg/day was injected to the distal flap area of the treatment group for 3 days, and normal saline was injected for the control group. On Postoperative Day 7, necrotic flap area was measured and compared, and angiograms of the skin flaps were obtained in the two groups.
RESULTS In the treatment group, the mean necrotic area was 21.9±6.4%, and in the control group, 37.7±5.9%. There was a statistically significant increase of skin flap survival in the treatment group ( p =.001). Angiography also showed vasodilation of the choke vessels between adjacent angiosomes to form true anastomosis in the treatment group.
CONCLUSION The results demonstrate that the use of local injection of tadalafil to failing skin flaps increases the survival of axial-pattern flaps in rats.     

真皮下血管网皮瓣蒂部的作用

考察真皮下血管网皮瓣的蒂部作用。方法用健康，白色家猪的实验，按自身相互对照原则在动物躯干两侧分别设计真皮下血管网皮瓣，传统皮瓣动物模型。通过两组皮瓣成过程的大体观察，及皮瓣ＥＣＴ检查核素分布情况的比较方法进行研究。     

Shock wave therapy reduces necrotic flap zones and induces VEGF expression in animal epigastric skin flap model

The effect of extracorporeal shock wave (ESW) therapy on skin flap survival and growth factor expression was investigated in a rat model using epigastric skin flap. Treatment and control groups each contained 20 animals. ESW effectively enhanced epigastric skin flap survival by significant reduction of areas of necrotic zones. At day 7 after the operation, necrotic zones of 4.2% were found in the ESW-treated group compared with 18.3% in the control group ( P < 0.01). Concomitantly, in tissue samples adjacent to the necrosis areas, increased vascular endothelial growth factor expression was observed in the ESW-treated animals (median 84.5%, range 57.4 to 94.5%) compared with the control group (median 46.7%, range 29.1 to 93.1%; P < 0.1). However, for expression of basic fibroblast growth factor, no difference was found between the two groups. The authors conclude that the success of the shock wave treatment may partly be due to modulation of growth factor expression.     

Subdermal nitrous oxide delivery increases skin microcirculation and random flap survival in rats

Random skin flaps are essential tools in reconstructive surgery. In this study, we investigated the effect of subdermal nitrous oxide (N₂O) application on random flap survival. In this experimental study, we used 21 female rats in three groups. In the N₂O and air groups, gases were administrated under the proposed dorsal flap areas daily for seven days. Following the treatment period, flaps were raised and inserted back into their place from the dorsal skin. In the control group, the flaps were elevated and inserted back to their place without any pretreatment. Calculation of necrotic flap areas, histological examination and microangiography was performed to evaluate the results 7 days after the flap surgery. The average of necrotic flap area in the N₂O, air and control group was 13.45%, 37.67% and 46.43%, respectively. (N₂O vs air p?=?.044; N₂O vs control p?=?.003). The average number of capillary formations identified in the histological analysis was 7.0?±?1.58, 3.75?±?2.36 and 4.4?±?0.54 in the N₂O, air and control group, respectively. (N₂O vs air p?=?.017; N₂O vs control p?=?.037). The average number of capillary structures identified in the angiography images were 6.3?±?1.52, 1.6?±?1.15 and 1.3?±?0.57 in the N₂O, air and control group, respectively. (N₂O vs air p?=?.04; N₂O vs control p?=?.02). We conclude that subdermal N₂O application increases random flap survival through an increase in the skin microcirculation and could be promising for future clinical applications.     

The effect of pentoxifylline on venous flap survival

An experimental study was performed to determine whether the survival area of a flap can be increased using pentoxifylline in a single-pedicled venous skin flap in the rat. Epigastric island venous skin flaps measuring 1.5Ƕ.5 cm were constructed bilaterally. The experimental group received intraperitoneal injections of pentoxifylline 25 mg/kg daily for 7 days following the operation. This study shows the pentoxifylline had no beneficial effect on single-pedicled venous island skin flap viability in the rat model.     

Effect of Human Placental Extract Treatment on Random-Pattern Skin Flap Survival in Rats

Background: Human placental extract (HPE), prepared from the placentas of healthy, postpartum females, displays various physiological activities, including antioxidative properties. In this study, a dorsal skin flap model was used to investigate the effect of HPE on flap viability in rats. Materials and methods: Forty male Sprague-Dawley rats underwent random-pattern skin flap surgeries. The animals were randomly divided among a control group and three treatment groups (localized injection (LI), 10 mg/kg/d localized HPE injections; low-dose treatment (LT), 10 mg/kg/d systemic HPE injections; high-dose treatment (HT), 40 mg/kg/d systemic HPE injections). Surviving skin flap areas were measured 7 days after surgery and tissue samples were stained with hematoxylin and eosin; vascular endothelial growth factor expression was determined immunohistochemically. To evaluate the antioxidant and antiapoptotic effects of HPE, malondialdehyde, glutathione peroxidase, and caspase-3 levels were examined. Results: Seven days after surgery, HPE-treated animals had significantly reduced necrotic areas, rats receiving the highest HPE dose demonstrated the greatest flap survival. In the HPE groups, the histopathological scores were lower than for the control group. Immunohistochemistry showed markedly more numerous vascular endothelial growth factor-positive cells in the HT group than in the C group. Malondialdehyde levels were significantly lower and glutathione peroxidase levels were higher in the HT group than in the C group. HPE treatment significantly inhibited apoptosis by lowering caspase-3 activity. Conclusions: HPE treatment yielded positive effects on flap survival, due to its antioxidant and antiapoptotic properties. These results suggest a new therapeutic approach for enhancing flap viability and accelerating wound repair.     

Accelerated flap prefabrication with vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) is a potent promoter of angiogenesis that has been shown to enhance revascularization of ischemic tissues, including skin flaps. This study was designed to investigate the value of a single topical application of recombinant human VEGF to accelerate flap viability in a rat model of a non-ischemic prefabricated flap. Prefabricated flaps were created in 48 Sprague-Dawley rats. An autologous tail artery loop was anastomosed to the femoral artery and vein, and implanted subcutaneously in the lower abdomen. Flaps were divided into two groups of 24 each. At the time of loop implantation the control group received 0.9 percent NaCl or a 16 percent vol/wet polyvinyl alcohol (PVA) solution: the treatment group received VEGF in 0.9 percent NaCl or VEGF in PVA. The PVA gel was used to facilitate topical application In each group, 3- x 4-cm flaps nurtured by the tail artery pedicle were elevated and resutured into place after 3, 4, and 5 weeks. The percentage of surviving skin of each flap was determined by planimetry 7 days after flap elevation. Mean skin survival areas at 3, 4, and 5 weeks were control group 0 percent. 8 percent and 17.5 percent; and VEGIF-treated group, 6 percent, 40 percent, and 66.7 percent respectively VEGF significantly improved flap survival by 5 weeks (p = 0.02). These results suggest that VEGF can accelerate maturation of prefabricated flaps. This approach could expand the application of flap prefabrication as a resource for reconstructive surgery.     

Gene therapy with adenovirus-mediated VEGF enhances skin flap prefabrication

We investigated the feasibility in rats of enhancing skin-flap prefabrication with subdermal injections of adenovirus-encoding vascular endothelial growth factor (Ad-VEGF). The left saphenous vascular pedicle was used as a source for vascular induction. A peninsular abdominal flap (8 x 8 cm) was elevated as distally based, keeping the epigastric vessels intact on both sides. After the vascular pedicle was tacked underneath the abdominal flap, 34 rats were randomly divided into three groups according to treatment protocol. The implantation site around the pedicle was injected with Ad-VEGF in group I (n = 10), with adenovirus-encoding green fluorescent protein (Ad-GFP) in control group I (n = 14), and with saline in control group II (n = 10). All injections were given subdermally at four points around the implanted vessel by an individual blinded to the treatment protocol. The peninsular flap was sutured in its place, and 4 weeks later, an abdominal island flap based solely on the implanted vessels was elevated. The prefabricated island flap was sutured back, and flap viability was evaluated on day 7. Skin specimens were stained with hematoxylin and eosin for histological evaluation. In two rats from each group, microangiography was performed to visualize the vascularity of the prefabricated flaps. There was a significant increase in survival of prefabricated flaps in the Ad-VEGF group compared to the control groups: Ad-VEGF, 88.9 +/- 6.1% vs. Ad-GFP, 65.6 +/- 9.4% (P < 0.05) and saline, 56.0 +/- 3.4% (P < 0.05). Sections from four prefabricated flaps treated with Ad-GFP revealed multiple sites of shiny deposits of green fluorescent protein around the area of local administration 1 day and 3 weeks after gene therapy. Histological examination done under high-power magnification (x400) with a light microscope revealed increased vascularity and mild inflammation surrounding the implanted vessel in all groups. However, we were unable to demonstrate any significant quantitative difference with respect to vascularity and inflammatory infiltrates in prefabricated flaps treated with Ad-VEGF compared with controls. Microangiographic studies showed increased vascularity around the implanted pedicle, which was similar in all groups. However, vascularization was distributed in a larger area in the prefabricated flaps treated with Ad-VEGF. In this study, the authors demonstrated that adenovirus-mediated VEGF gene therapy increased the survival of prefabricated flaps, suggesting that it may allow prefabrication of larger flaps and have the potential to reduce the time required for flap maturation.