Improved dorsal random-pattern skin flap survival in rats with a topically applied combination of nonivamide and nicoboxil

Standardization of the Rat Dorsal Random Pattern (McFarlane) Flap Model and Evaluation of the Pharmacological Agents Aiming to Salvage Partial Flap Necrosis: A Systematic Review and a Meta-analysis

INTRODUCTION

Partial flap necrosis is a common complication after surgery. McFarlane flap model has been used for assessment of various agents' effects on random flap survival. The aim of this study was to review the methodology of studies using this flap model and reveal the most successful agents.

MATERIALS AND METHODS

PubMed, Scopus, and Web of Science databases were screened for words "McFarlane flap," "flap survival," and ("flap" and "rat") by using time limits between 1965 and 2019. A total of 71 original articles were reviewed. Dimensions and base (cranial/caudal) of the flap, treatment protocol, follow-up period, and survival rates were extracted. Modified survival rates were calculated. Coefficients of variation of cranial/caudally based control group flaps and most commonly used flap models were calculated to assess interstudy variability.

RESULTS

A total of 165 different treatment regimens were studied. One-hundred twelve regimens (67.9%) were found to increase flap survival. Most common flap dimensions were 9 cm × 3 cm, followed by 10 cm × 3 cm, 8 cm × 2 cm and 6 cm × 2 cm. Studies using caudally based flaps showed less interstudy variability, but survival rates were similar. Pentoxifylline, sildenafil, chlorpromazine, phenoxybenzamine, and phentolamine were reported to be successful in multiple studies.

CONCLUSIONS

There are numerous agents found to be effective for treatment of partial flap necrosis, but further clinical research is needed. To overcome standardization problems, use of commonly used flap dimensions with a caudal base and interpretation of results after 7 days of follow-up seems appropriate.

Comparison of the efficacy of multiple antioxidant and hyperbaric oxygen treatments in the prevention of ischemia and necrosis of local random McFarlane skin flap

OBJECTIVE

The aim of this study was to compare the efficacy of multiple antioxidant (Proxeed Plus (PP) with Carnitine, Selenium, Zinc, Coenzyme Q10, Vitamin C, Folic Acid, Vitamin B12) on local random skin flap healing with the hyperbaric oxygen (HBO) therapy.

METHODS

Fourty rats were equally divided into five groups (Control, PP, HBO, HBO + PP, PP + HBO + PP). Local random McFarlane skin flap was applied to all rats. Following the applications, evaluations were made biochemical (TAS, TOS, OSI, IL-1β, IL-6, TNF-α, TGF-β, VEGF) and histopathological parameters.

RESULTS

Necrosis percentage was found to be lower in the PP + HBO + PP group than all other groups whereas the necrosis percentages of PP and HBO groups were similar. Oxidative stress rates were significantly higher in the control group compared to the other groups whereas it was lower in the PP + HBO + PP group than all other groups. The inflammation parameters were the highest in the control group and the lowest in the PP + HBO + PP group. Growth factors were higher in the PP + HBO + PP group than all other groups. Epithelialization and wound healing were better in the HBO and PP groups than in the control group. The greatest healing, epithelialization and vascularization was seen in the PP + HBO + PP group. The histopathological findings in the PP + HBO + PP group were better in each inner region than in the other groups.

CONCLUSION

Biochemical and histopathological parameters have shown that PP reduces ischemia and necrosis and increases oxygenation in flap healing by providing significant improvement thanks to the multiple molecular structures in its content.

Improved viability of murine skin flaps using a gelatin hydrogel sheet impregnated with bFGF

Basic fibroblast growth factor (bFGF) promotes epithelial cell proliferation and angiogenesis but its clinical applications are limited by its short half-life and low retention. Recently developed gelatin hydrogel sheets able to release physiologically active substances in a controlled manner have the potential to overcome these issues. In this study, the effects of gelatin hydrogel sheets impregnated with bFGF on flap survival and angiogenesis were examined in a murine skin flap model. A flap of 1 × 3 cm was generated on the backs of 60 C57BL/6 mice. The mice were divided into five groups (n = 12/group): Group I, untreated; Group II, treated with a gelatin hydrogel sheet impregnated with saline; Group III, treated with bFGF (50 µg) without sheets; Groups IV and V, treated with gelatin hydrogel sheets impregnated with 50 and 100 µg of bFGF, respectively. On the seventh day after surgery, the flap survival area and vascular network were examined and hematoxylin and eosin and von Willebrand factor staining were used for histological examinations. The flap survival areas were significantly larger in Groups IV and V than in other groups. The area of new vessels was significantly larger in Group IV than in the other groups. In the murine skin flap model, gelatin hydrogel sheets impregnated with bFGF promoted angiogenesis and improved flap survival. These findings support the use of bFGF-impregnated gelatin hydrogel sheets for improving ischemic flap survival in clinical settings.

Quantitative impact analysis of remote ischemic conditioning and capsaicin application on human skin microcirculation

BACKGROUND

Improvement of skin microcirculation would be beneficial in transplanted tissues and thus, there is a demand for effective, reliable and harmless angiogenic treatments. The aim of this study was to assess the effect of capsaicin application (CA), the remote effect of capsaicin application (REC), the impact of remote ischemic conditioning (RIC), and the impact of combined remote ischemic conditioning with capsaicin application (Comb) on human skin microcirculation.

METHODS

Perfusion changes were assessed using a laser Doppler device (easyLDI, Aimago Lausanne). 30 healthy volunteers were enrolled and divided into two groups: 1) CA and REC: perfusion was assessed on both forearms after application of capsaicin cream on one forearm with an exposure time of 40 minutes. 2) RIC and Comb: perfusion of one forearm was assessed after four cycles of 5 min blood occlusion and 5 min reperfusion using a tourniquet on the contralateral upper arm and application of capsaicin on the ipsilateral forearm. Baseline skin perfusion measurements of both forearms were carried out initially and were used as intra-individual reference.

RESULTS

1) Skin perfusion significantly increased after capsaicin application (CA = +328.3% , p > 0.05). There was no remote skin perfusion change due to capsaicin (REC). 2) RIC significantly improves skin perfusion (RIC = +20.0% , p < 0.05). The combination of RIC and CA does not improve skin perfusion compared to CA alone (Comb).

CONCLUSIONS

The conditioning techniques RIC and CA showed a significant increase in human skin perfusion, CA being superior to RIC. However, the combination of CA and RIC showed no additional improvement potential as compared to CA alone. Furthermore, a remote effect of capsaicin application could not be demonstrated. These results encourage to analyze if the conditioning treatments are also beneficial for transplanted tissue survival.

The Effect of Ozonated Olive Oil on Neovascularizatıon in an Experimental Skin Flap Model

OBJECTIVE

Angiogenesis is an important factor for flap viability. It has been reported that ozonated oil contributed to improved neovascularization in an acute cutaneous wound healing model. This study was undertaken to evaluate the effect of ozonated olive oil on vascular endothelial growth factor (VEGF)-mediated neovascularization of skin flaps in rats.

STUDY DESIGN

A skin flap model was established in 21 rats and evaluated within 3 groups. No treatment was given to the rats in group 1. Olive oil and ozonated olive oil were topically applied (twice daily) to the flap surface for 7 days in groups 2 and 3, respectively. Immunohistochemical staining was performed to analyze the expressions of VEGF and CD34.

RESULTS

The mean numbers of VEGF- and CD34-positive staining microvascular structures were 8.86 (SD, 1.35) and 10.29 (SD, 1.80) in group 1, 15.00 (SD, 1.41) and 15.57 (SD, 1.72) in group 2, and 25.14 (SD, 2.41) and 25.00 (SD, 2.16) in group 3. The VEGF and CD34 expressions in group 3 were significantly higher than those in group 2 (P < .001). Their expressions in group 2 were significantly higher than those in group 1 (P < .001).

CONCLUSIONS

Both ozonated olive oil and olive oil improved neovascularization when they were topically applied on skin flaps. The effect of ozone was more prominent.

Skin Perfusion Changes within 12 h after Axillary Plexus Block

Background/Purpose: An improvement of the blood flow would be beneficial in microvascular upper-extremity reconstruction and in digit replantation. In the present work, skin perfusion changes and their duration due to axillary plexus block were quantified. Methods: The peripheral blood flow of the upper extremities in 20 patients undergoing trapeziectomy under axillary plexus block was analyzed. Results: Laser Doppler spectrophotometry was used to measure perfusion factors over a 12-h period, with the contralateral hand acting as the control. Axillary plexus block produced a significant increase of peripheral oxygen saturation (117 ± 35% vs. control 93 ± 22%, p = 0.019), peripheral blood flow (220 ± 166% vs. 130 ± 77%, p = 0.037), and velocity (164 ± 58% vs. 117 ± 45%, p = 0.011). Conclusion: Axillary plexus block produces an improvement of peripheral tissue oxygen saturation of the upper extremities over the first 6 h after the inception of anesthesia. This suggests a potential benefit especially for critically perfused tissues.

Effects of Kaurenoic Acid and Arginine on Random Skin Flap Oxidative Stress, Inflammation, and Cytokines in Rats

BACKGROUND

Kaurenoic acid (KA), a diterpene extracted from copaíba oil-resin, is known to have potent antioxidant and anti-inflammatory properties. L-Arginine (LA) is an amino acid and a nitrogenous precursor for the synthesis of nitric oxide (NO). NO paper in wound healing has already been well documented. The aim of this study was to investigate the protective effects of LA and KA against ischemia reperfusion injury in a randomized skin flap model in rats.

METHODS

A modified McFarlane flap model measuring 2.5 wide × 8 cm long was established in 36 anesthetized rats and evaluated within 3 groups: group control, group L-arginine, and group kaurenoic acid. Each group was subdivided into two subgroups (T1 and T2, n = 6 each). Samples were collected 24 h (T1)/48 h (T2) postoperatively for oxidative stress (glutathione), as non-protein thiols, malondialdehyde (MDA), NO2, inflammation [myeloperoxidase (MPO)], and cytokines TNF-α and IL-1β assays.

RESULTS

KA promoted a significant decrease of TNF-α and IL-1 expression and MPO activity at T1/T2 time points. NSGH levels increased significantly in KA-treated rats, while MDA levels decreased significantly in the same rats. Arginine promoted a significant decrease in MDA levels at the T1 time point and a significant increase in non-protein thiols concentrations at T1/T2 time points. NO2 concentration also decreased at the T1 time point.

CONCLUSIONS

KA may attenuate the oxidative stress and the inflammation, thereby reducing tissue damage induced by ischemia/reperfusion in rats subjected to dorsal skin flaps.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors http://www.springer.com/00266.

The effects of epinephrine and dobutamine on skin flap viability in rats: a randomized double-blind placebo-controlled study

BACKGROUND

Intraoperative reduction in arterial pressure may cause hypoperfusion of skin flaps, which may increase the risk of flap failure. There is no international consensus regarding the use of vasoactive or inotropic agents to restore or maintain flap perfusion. The purpose of this study was to evaluate the effects of the intraoperative administration of epinephrine and dobutamine on axial-pattern skin flap survival in rats.

METHODS

Fifty-four Sprague Dawley rats were randomized into three groups (n = 18). A tubed axial-pattern skin flap was performed. Animals were randomized to receive an intraperitoneal injection of epinephrine 0.1 mg/kg, dobutamine 0.3 mg/kg, or saline (0.5 ml). The rats were euthanized after 7 days and the viable area of the flap was compared between the groups using a digital imaging and computer software.

RESULTS

Seven rats/flaps were excluded from the study due to autocannibalism (n = 3), postoperative tracheal obstruction (n = 2), anesthesia-induced respiratory arrest (n = 1), and abnormal behavior requiring euthanization (n = 1). The mean flap survival was 46% ± 9% in the saline group (n = 17), 41% ± 9% in the epinephrine group (n = 14) (p = 0.088 compared to the saline group), and 54% ± 9% in the dobutamine group (n = 16) (p = 0.02 compared to the saline group and p = 0.001 compared to the epinephrine group).

CONCLUSIONS

Intraoperative intraperitoneal injection of dobutamine improves skin flap survival in rats, whereas intraperitoneal epinephrine tends to decrease skin flap survival.

Overexpressed HIF-2α in Endothelial Cells Promotes Vascularization and Improves Random Pattern Skin Flap Survival

BACKGROUND

The local skin flap procedure is very useful for reconstruction. However, flap necrosis caused by circulatory failure can occur at its distal portion. Hypoxia-inducible factors (HIFs) in endothelial cells (ECs) help to maintain ECs and promote vascularization, and HIF-2α is abundantly expressed in ECs. However, the mechanisms of action of HIF-2α in ECs are not yet fully understood. The aim of this study was to evaluate the in vivo effects of overexpression of HIF-2α in ECs on skin flap survival.

METHODS

A random pattern skin flap (1.0 × 3.0 cm) was elevated on the dorsum of transgenic mice (Tg mice) with EC-specific HIF-2α conditional overexpression and wild-type littermate control mice (n = 6). Flap survival was evaluated on postoperative day 7. Tissue samples from the skin flaps were harvested and analyzed using Western blotting, quantitative reverse transcriptase-polymerase chain reaction, and immunohistochemistry.

RESULTS

The HIF-2α mRNA and protein levels were significantly increased in the Tg mice when compared with control mice. Tg mice had significantly increased skin flap survival areas (72.0% ± 2.7%) when compared with wild-type mice (45.7% ± 1.1%). Moreover, histological examination revealed an increase in the subcutaneous blood vessel counts in the Tg mice.

CONCLUSIONS

Specific overexpression of HIF-2α in ECs promoted vascularization and enhanced skin flap survival in vivo in a mouse model.

The role of androgens on hypoxia-inducible factor (HIF)-1α-induced angiogenesis and on the survival of ischemically challenged skin flaps in a rat model

BACKGROUND

Effects of androgens on angiogenesis are controversial. Hypoxia-inducible factor (HIF)-1α promotes expression of vascular endothelial growth factor (VEGF) that stimulates angiogenesis.

PURPOSE

This study investigates whether androgens stabilize HIF-1α in endothelial cells, and androgen depletion decreases VEGF concentrations and skin flap survival.

MATERIALS AND METHODS

Male human umbilical vein endothelial cells (HUVECs) were exposed to dihydrotestosterone (DHT) and HIF-1α expression was measured. In male Wistar rats, standardized proximally based random pattern dorsal skin flaps (3 × 9 cm) were raised 4 weeks after orchiectomy and sham operation, respectively (n = 10, each). Flap VEGF concentrations (immunohistochemistry), perfusion (Laser Doppler), and viability (digital planimetry) were measured.

RESULTS

DHT induced HIF-1α expression in HUVECs. Androgen depletion induced decreased VEGF expression (P = 0.003), flap perfusion (P < 0.05), and survival (44.4% ± 5.2%) compared to controls (35.5% ± 4.5%; P = 0.003).

CONCLUSION

In vitro, androgens may stimulate HIF-1α under normoxic conditions. In rats, androgen depletion decrease VEGF expression and flap survival.

Dimethyloxalylglycine stabilizes HIF-1α in cultured human endothelial cells and increases random-pattern skin flap survival in vivo

BACKGROUND

The goal of this study was to evaluate in vitro and in vivo the effects of up-regulation of the proangiogenic hypoxia inducible factor (HIF)-1α induced by dimethyloxalylglycine on endothelial cell cultures and on skin flap survival.

METHODS

Human umbilical vein endothelial cell cultures were exposed to hypoxic conditions, to dimethyloxalylglycine, and to cobalt chloride for up to 24 hours. Expression of HIF-1α and vascular endothelial growth factor (VEGF) in cell culture media was analyzed. In vivo, 20 male Wistar rats were assigned randomly to either the treatment group (dimethyloxalylglycine intraperitoneal injection, n = 10) or the control group (saline intraperitoneal injection, n = 10). A dorsal skin flap was raised in all animals and sutured back into place. Flap survival was evaluated on postoperative day 7 by laser Doppler and digital planimetry.

RESULTS

In vitro treatment of human umbilical vein endothelial cells during a 24-hour period showed a significant elevation of VEGF expression with dimethyloxalylglycine exposure (92 ± 35 pg/mg total cellular protein) or hypoxia exposure (88 ± 21 pg/mg total cellular protein) compared with controls (23 ± 10 pg/mg total cellular protein) (p < 0.05 for both). In vivo experiments showed a significant decrease of flap necrosis in the treatment group animals versus controls (35.95 ± 5.03 percent versus 44.42 ± 5.18 percent, p < 0.05). The laser Doppler evaluation revealed significantly increased blood flow in the proximal two-thirds of the flap in the treatment group compared with the control group (p < 0.05).

CONCLUSION

Dimethyloxalylglycine treatment significantly increases VEGF and HIF-1α expression in endothelial cell cultures and enhances skin flap survival in vivo in a rat model.

Effects of Copaifera langsdorffii Desf. on ischemia-reperfusion of randomized skin flaps in rats

BACKGROUND

Copaíba oil is an oleoresin obtained from the Copaiffera langsdorffii genus (Leguminoseae). It is widely used in folk medicine as an antiinflammatory, healing, and antiseptic agent. Comparative pharmacologic studies between different species of copaíba oils are scarce.

METHODS

The protective effect of Copaiffera langsdorffii was evaluated on an experimental model of random skin flaps on rat dorsums.

RESULTS

Seventy-two Wistar rats (average weight = 216.8 g) were divided randomly into four equal groups (saline control, vehicle control, GT200-Test 1, and GT400-Test 2). A caudally based rectangular flap, 2.5-8.0 cm in size, was elevated on the back of the rat using McFarlane's method. The flap was sutured back into its original place. Copaifera and control drugs (saline and Tween 80) were administered by gavage 24, 12, and 2 h prior to the beginning of the experiment followed by daily doses for the next 7 days. To observe the effects of Copaifera, laboratory analyses included plasma and tissue levels of tiobarbituric acid-reactive substances (TBARS) and reduced glutathione (GSH) and tissue levels of myeloperoxidase (MPO).

CONCLUSION

The oil-resin of copaíba presents discrete antilipoperoxidation action, intense antioxidant action, and antiinflammatory activity during the ischemia and reperfusion of randomized cutaneous flaps. The effects of ischemia-reperfusion are complex and substances capable of increasing the tolerance of tissue to those effects by reducing the production or neutralizing the action of free radicals are needed.

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 x 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.

Oral administration of nicorandil enhances the survival of ischemic skin flaps in rats

Nicorandil has an anti-apoptotic effect on ischemic myocardium through the activation of ATP-sensitive potassium (K(ATP)) channel. We tested the hypothesis that oral administration of nicorandil had a protective effect on ischemic skin flaps. A cranially based skin flap measuring 3x7 cm in full thickness was made on the back of rats. The rats were divided into a control group and 8 nicorandil groups (group 1-8) according to different doses and timings of administration. On day 7 at 5 cm, groups 1 to 6 (10 or 30 mg/kg twice per day for 3 days starting at 24 h before, 0.5 h before or 0.5 h after the operation) showed significantly higher blood perfusion change rate (73.3+/-2.9%-79.1+/-4.1% vs. 25.9+/-8.6%, P<0.01), and significantly higher survival rate (68.8+/-4.8-75.2+/-8.2% vs. 47.0+/-2.8%, P<0.05) than the control group. Many more surviving blood vessels were also observed in these groups. In contrast, no significant effects were found either in group 7 (30 mg/kg twice per day for 3 days starting 24 h after the operation) or group 8 (30 mg/kg once at 0.5 h after the operation). We did not find an angiogenic effect of nicorandil in vitro. Therefore, our results confirmed that the oral administration of nicorandil could protect tissues from necrosis in ischemic skin flaps. In addition, its protective effect depends on the time of first administration and the duration.

Effect of sildenafil citrate on viability of flaps: an experimental study in rats

Various pharmacological agents have been used to try and elucidate the pathophysiology of ischaemia and necrosis of flaps. Their most important disadvantage is the need for relatively high doses given systemically, which increases the risk of potential side effects. Topical or local agents are more useful. Sildenafil citrate, the specific inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE 5) was studied as an antianginal drug during the late 1980s, but is now used for its effect on erectile function in men. Sildenafil citrate causes dilatation of peripheral arteries and veins and the inhibition of the thrombus-forming ability of platelets in vivo. Our study was designed to test the efficacy of sildenafil citrate on the viability of flaps.

Improved Flap Viability With Site-Specific Delivery of Sildenafil Citrate Using Fibrin Glue

Sildenafil is a cyclic guanosine-specific phosphodiesterase type 5 (PD-5) inhibitor that is widely used for erectile dysfunction. Potent and competitive inhibition of PD-5 enhances levels of cyclic guanosine monophosphate (cGMP). Fibrin glue-apart from tissue fixation-has been used for slow release of drugs. In this study, local delivery of Sildenafil citrate with fibrin glue was accomplished to improve random flap survival. Fifty Wistar rats were randomized into 5 groups, and a standardized dorsal random-pattern skin flap was elevated in each rat. In Group I (n = 10), the base of the flap was divided, making it a "graft" control to study the graft effect. In Group II (n = 10), a thin Silastic sheet was used to separate the flap from the underlying vascular bed, and no pharmacologic treatment was given. In Group III (n = 10), only 0.5 mL of fibrin glue was applied to the flap donor site. In Group IV (n = 10), 2.5 mg of sildenafil citrate mixed in 0.5 mL of fibrin glue was applied to donor site of the flap, whereas 10 mg of sildenafil citrate mixed in 0.5 mL of fibrin glue was applied in Group V (n = 10). Area of flap survival was evaluated on postoperative seventh day. Total necrosis of all of the flaps was observed in "graft" control group (Group I). Sildenafil and fibrin glue groups (Group IV and V) resulted in a statistically significant decrease in flap necrosis compared with Groups II and III (P < 0.0001). A statistically significant difference could not be documented between Group II and Group III (P > 0.0001). The decrease in skin necrosis was statistically significant in Group V compared with Group IV (P < 0.0001). Histologic examination revealed significantly increased vascular density in Groups IV and V compared with Groups II and III (P < 0.0001), whereas a significant difference could not be documented between Groups IV and V (P > 0.0001) and between Groups II and III (P > 0.0001). In view of these results, topical sildenafil application seems to improve flap survival in random-pattern skin flaps in dose-dependent manner.

Comparison of the effectiveness of gene therapy with transforming growth factor-beta 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.

Preconditioning of the rat random-pattern skin flap: modulation by opioids

Opioid receptors have been implicated in protecting several organ systems from ischaemic events. The authors have studied the effects of opioid receptors on random-pattern skin flap survival. Sixty-nine male Sprague-Dawley rats were used. Bipedicled dorsal skin flaps (2 x 8 cm) were elevated at the midline. Different doses of morphine (0.01, 0.1, 1 and 5 mg/flap) were administered locally in the cranial half of the flap and systemically through intraperitoneal injections (5 and 10 mg/kg). In another experiment, 0.4 mg/flap of naloxone was injected followed by 5 mg/flap injection of morphine to determine whether the effect of morphine is receptor mediated. The role of the opioid receptors in the ischaemic preconditioning (IPC) phenomenon was investigated by administration of naloxone (0.4 mg/flap) 1 h before clamping the cranial pedicle for 20 min followed by 40 min of reperfusion. Appropriate control groups were included. The cranial pedicle was cut 2 h after saline or drug administration in all groups and flap survival area was evaluated on the seventh postoperative day. Local administration of morphine in higher doses (1 and 5 mg/flap) significantly reduced the amount of flap necrosis when compared to that of the control cohort (P < 0.05). Naloxone abolished this protective effect of morphine. Furthermore naloxone significantly decreased the anti-ischaemic effect of the IPC. Systemic administrations of morphine had no significant effect on flap survival area in compare with the control group.

Dual Synergistic Effect: The Effect of Dexamethasone Plus Carnitine on Skin Flap Survival

Dexamethasone has well-known useful effects in dealing with the progression of necrosis. Carnitine is an endogenous cofactor, for having a regulatory action on the energy flow from different oxidative sources. The aim of this study was to determine whether combined local dexamethasone and systemic carnitine administration would result in an additive enhancement of skin flap survival in the rat model. A rectangular (3 cm x 11 cm) dorsal random skin flap was elevated on the rats and then sutured back into its original site with separate sutures. Overall, 40 rats were allocated randomly into 4 groups: Group 1 (control group, n = 10), group 2 (Dexamethasone group, n = 10, 2.5 mg/kg), group 3 (carnitine group, n = 10, 100 mg/kg), group 4 (dexamethasone plus carnitine group, n = 10).The mean flap survival area was 57.50 +/- 5.2% (mean survival area +/- SD) in control group (group 1), 71.5 +/- 4.8% in the dexamethasone group (group 2), 73.0 +/- 5.5% in the carnitine group (group 3), 85.30 +/- 6.1% in the dexamethasone plus carnitine group (group 4). In conclusion, based on the findings of this experimental study, the synergistic effect of carnitine and dexamethasone on skin flap viability is determined.

Adenovirus-mediated transforming growth factor-β ameliorates ischemic necrosis of epigastric skin flaps in a rat model1, 2

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.