Effect of surgical denervation on the viability of inferior epigastric neurovenous flaps in the rat

The purpose of this study was to examine how the inferior epigastric neurovenous flap in the rat reacts to surgical denervation. The survival of a denervated flap was compared with that of an innervated flap. A 2 x 2-cm flap was raised in 30 female Wistar rats assigned randomly to six groups of 10 rats each: group 1, innervated neurovenous flap; group 2, denervated neurovenous flap, acute model; group 3, denervated neurovenous flap, chronic model; group 4, innervated inferior epigastric island flap; group 5, denervated inferior epigastric island flap, acute model; and group 6, control, composite graft. Acute denervation produced a significant decrease in the survival of the inferior epigastric neurovenous flap (p < 0.05). The surviving area of the innervated flaps decreased from 94+/-14% (mean +/- standard deviation) to 16+/-34% by acute denervation. Chronic denervation was effective in decreasing flap necrosis in these flaps (survival, 99+/-5%). There were no differences between the average viable area of the standard inferior epigastric flap in the denervated and innervated groups.     

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.     

Protective effects of monoclonal antibody to intercellular adhesion molecule-1 in venous ischemia-reperfusion injury: experimental study in rats

Flaps with venous occlusion have a decreased survival rate compared with arterial occlusion. It seems that several factors are involved in the etiology of total venous occlusion, including free radicals, edema, thrombosis, and reperfusion injury. In the present study, the authors evaluated the blockage of polymorphonuclear leukocyte endothelial adhesion by using a monoclonal antibody to the intercellular adhesion molecule 1 (ICAM-1) ligand to prevent venous ischemia-reperfusion injury in rat epigastric island flaps. A skin flap (3 x 4 cm) supplied by the superficial epigastric artery and vein was harvested unilaterally in 40 male Wistar rats. Total venous occlusion of the skin flap was achieved. Arterial inflow was left intact. Rats were randomly divided into four groups (n = 10). In Group 1; rats were intravenously pretreated with 0.5 ml of 0.9 percent normal saline 15 min before applying a venous clamp, and the flaps were subjected to 6 hr of venous ischemia. In Group 2; rats were intravenously pretreated with 0.05 mg of monoclonal antibody to the intercellular adhesion molecule 1 (0.20 mg/kg) in 0.5 ml of 0.9 percent normal saline 15 min before applying the venous clamp, and the flaps were subjected to venous ischemia as in Group 1. In Group 3; rats were pretreated as in Group 1, and the flaps were subjected to 8 hr of venous ischemia. In Group 4; rats were pretreated as in Group 2, and the flaps were subjected to 8 hr of venous ischemia. The flaps were assessed histologically and by measuring viable and non-viable areas on postoperative day 7. Flap measurements revealed that blocking the action of ICAM-1 IN VIVO by administering monoclonal antibody significantly attenuated ischemic injury after 6 or 8 hr of venous occlusion.     

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.     

Effect of celecoxib on fasciocutaneous flap survival and revascularization

OBJECTIVES: To study the effect of celecoxib (Celebrex; Pfizer, Cambridge, Mass) on (1) primary ischemic time and (2) revascularization of fasciocutaneous free flaps in a rat model. METHODS: In the ischemia study, 50 male Sprague-Dawley rats were divided into 2 groups of 25 rats each, a control group and a celecoxib group. Five rats in each treatment group were exposed to ischemic times of 4, 6, 8, 10, and 12 hours. Survival of the flap was assessed 7 days after reversal of the ischemia. Probit curves and the critical ischemic time were calculated. In the revascularization study, 30 male Sprague-Dawley rats were divided into 2 groups of 15 rats each. One group was fed celecoxib, while the other was fed a normal diet. All rats had a 3 x 6-cm fasciocutaneous flap based on the inferior epigastric artery elevated and exposed to 2 hours of primary ischemia. The flap was then sutured back into the wound bed. Each of these groups was then divided into 3 groups of 5 rats whose pedicles were divided on postoperative day 5, 6, or 7. Percentage survival of the flap was measured 7 days later. In both parts of the study, the experimental group was fed celecoxib, 1500 ppm, throughout the interoperative period. In each animal, a 3 x 6-cm ventral fasciocutaneous groin flap based on the left superficial epigastric artery was elevated. RESULTS: In the ischemia study, respective flap survival rates from the control and celecoxib groups at the various ischemic times were as follows: 4 hours, 100% and 100%; 6 hours, 80% and 100%; 8 hours, 80% and 80%; 10 hours, 60% and 60%; and 12 hours, 20% and 10%. The median lethal ischemic times were 9.7 and 9.6 hours, respectively. There was no statistical difference in flap survival between the celecoxib and control groups. In the revascularization study, ligation of the flap pedicle on day 5, 6, or 7 did not result in any difference in the percentage of flap survival among the 3 groups. CONCLUSION: Celecoxib appears to have no deleterious effect on free tissue transfer survival or healing, as evidenced by revascularization in a fasciocutaneous free flap model.     

Neurovenous superficial inferior epigastric flaps in rats

BACKGROUND: We performed an experimental study on 46 male rats to evaluate the vitality of superficial inferior epigastric neurovenous flaps performed following different procedures. METHODS: Rats were divided into 5 groups: A (n=6), B (n=10), C (n=10), D (n=10) and E (n=10). On each rat a hemi-abdominal flap based on the superficial inferior epigastric pedicle was raised. In group A the flap was sutured into its original position, isolating it from underlying tissues by a latex glove patch. In group B an arteriectomy of the superficial inferior epigastric artery was performed. In group C the superficial inferior epigastric artery was sectioned at its origin, without dissecting it out of the pedicle. In group D and E the same procedures performed respectively in group B and C were followed, but the epigastric pedicles were immediately explanted for optic microscope observation. Flap vitality in groups A, B and C was checked after 7 days. RESULTS: Flaps in group A appeared completely vital: the glove did not interfere with flap survival. All flaps in group B looked necrotic. In group C, 9 flaps survived completely and 1 flap underwent complete necrosis. Pedicle specimens of the viable flaps (group C) were explanted for observation under the optic microscope. Each specimen from groups C, D, E revealed a rich vascular plexus in the connective tissue around the pedicle. Seven days after surgery, neo-microangiogenesis was evident. CONCLUSIONS: The results witness the importance of perivenous and perineural arterioles for neurovenous flaps survival, also considering the adaptive increase in capillary development in the days following surgery.     

Sulfatide and monoclonal antibodies prevent reperfusion injury in skin flaps

Sulfatide binds to P- and L-selectin, which play important roles in the initiation of neutrophil-endothelial interactions. Sulfatide protects skin flaps from ischemia-reperfusion injury. The purpose of this study was to evaluate the augmented protection when anti-rat ICAM-1 and anti-rat LFA-1 antibodies are combined with sulfatide in the ischemia-reperfusion model of rat skin flaps. Sulfatide was administered intravenously just before elevation of the right abdominal epigastric flap, and monoclonal antibodies were injected 30 min before clamp release. The femoral artery and vein were clamped above and below the epigastric vessels for 11 h and then the clamp was released. The administration of both sulfatide and monoclonal antibodies significantly increased the flap surviving area (6.58 +/- 0.61 cm(2) versus the group with monoclonal antibodies alone, 4.43 +/- 0.32 cm(2), P = 0.01). In the untreated rats the area was 1.86 +/- 0.36 cm(2). Histological examination 24 h after reperfusion in the group treated with sulfatide and monoclonal antibodies showed only slight leukocyte invasion into the flap, and myeloperoxidase activity 24 h after reperfusion was significantly reduced. This study indicates that both sulfatide and monoclonal antibodies protect rat skin flaps from ischemia-reperfusion injury.     

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.     

Postischemic flap washout with hydroxyethyl starch (HAES) and its beneficial effect on the no-reflow phenomenon in rat skin island flaps

This study investigated the possible effect of hydroxyethyl starch (HAES) as a postischemic perfusion washout on survival of skin flaps. Forty-eight, male, Sprague-Dawley rats were used in this experiment. A 4×6 cm unilateral island skin flap based on the superficial inferior epigastric artery and vein was raised. The femoral neurovascular bundle supplying the flap pedicle was also dissected free. The flaps were divided into four groups, each consisting of 12 rats. Group 1 (Nonishemic control); Group 2 (Control) – no perfusion washout; Group 3 (Saline) – postischemic washout with normal saline solution; Group 4 (HAES) – postischemic washout with hydroxyethyl starch 10% (HAES) solution. The flaps were subjected to 11 hours of warm ischemia. Thirty minutes prior to the completion of the ischemic period, the flaps were perfused with normal saline solution in group 3 and with HAES in group 4. The percentage of flap survival was assessed on postoperative day 7. Statistical analysis was performed using the Student’s t-test. Flap survival rates for Group 4 (HAES) were significantly greater than Group 2 (Control nonperfusion washout) and Group 3 (saline solution) (p<0.001). This is the first study to investigate the effect of HAES on skin flap survival based on the results, HAES solution may be useful in clinical practice. Received: 6 August 1997 / Accepted: 11 December 1997     

The effect of hyperbaric oxygen on reperfusion of ischemic axial skin flaps: a laser Doppler analysis.

This study evaluates the microvascular reperfusion of ischemic skin flaps with and without acute hyperbaric oxygen (HBO) treatment. Thirty-two axial pattern epigastric skin flaps (3 x 6 cm) in male Wistar rats were subjected to 8 hours of global ischemia by pedicle clamp occlusion. The rats were divided into the following control and two experimental groups: Control (n = 12) with ischemia, no HBO; Group 1 (n = 11) with HBO treatment (three 1.75-hour dives, 2.5 absolute atm, 100% O2) during ischemia; and Group 2 (n = 9) with HBO treatment (two 1.75-hour dives) immediately after ischemia. Laser Doppler flows were recorded in two distal standardized flap locations at 0.5, 2, 4, and 18 hours after reperfusion in control rats and Group 1 rats and at 18 hours only in Group 2 rats, using a Med-Pacific 6000 laser Doppler unit. Mean distal flap laser Doppler flows (mV) were Control: 0.5 hours = 23.2 +/- 11.9, 2 hours = 52.8 +/- 27.3, 4 hours = 53.6 +/- 32.1, 18 hours = 40.2 +/- 36.2; Group 1: 0.5 hours = 71.8 +/- 30.9 (p less than 0.05 vs. control), 2 hours = 74.3 +/- 27.3, 4 hours = 67.4 +/- 20.6, 18 hours = 79.1 +/- 40.3 (p less than 0.05 vs. control); and Group 2: 18 hours = 90.3 +/- 47.9 (p less than 0.05 vs. control). It is concluded that acute HBO treatment of ischemic rat skin flaps improves distal microvascular perfusion as measured by laser Doppler flowmetry. This effect is observed for HBO treatment given either during or immediately after prolonged global ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of twisting on perforator flap viability: an experimental study in rats

Perforator flaps increasingly find acceptance and use in the field of reconstructive surgery due to their decreased donor-site morbidity and increased like-tissue coverage. Nevertheless, they are more prone to vascular compromise, especially when the meticulous technique they require is not employed. Pedicle twisting is a condition occasionally encountered in flap procedures, sometimes inadvertently, sometimes inevitably. In this study, circulatory comprise induced by twisting of the pedicle on a true perforator flap in a rat model is investigated.Thirty-eight Wistar-Albino rats were randomized into 4 groups, and cranial epigastric artery true perforator flaps were elevated on a single perforator. The flaps were returned as they were in the control group (n = 9), and with 90 degrees , 180 degrees , and 270 degrees of torsion in groups 2 (n = 9), 3 (n = 10), and 4 (n = 10), respectively. The flaps were evaluated by their flap survival area, weight, and histopathological appearance by the end of the first week.The mean flap survival ratios for groups 1, 2, 3, and 4 were 97.78 +/- 4.41%, 72.22 +/- 44.10%, 73.50 +/- 30.46%, and 30 +/- 30.18% (mean +/- SD), respectively. The degree of degenerative changes in group 4 was found to be statistically significant (P < 0.016).Our histopathological examinations indicate that vascular compromise was moderate in group 3 and severe in group 4. Our findings suggest that under normal conditions, the pedicle of a true perforator flap must not be twisted more than 180 degrees .     

Calcitonin gene-related peptide delays the no-reflow phenomenon in the rat island flap

Calcitonin gene-related peptide (CGRP) is a bioactive neuropeptide with potent vasodilatory properties. The effect of CGRP on the no-reflow phenomenon was studied in rats. Island flaps based on the epigastric vessels were exposed to 11 hours of warm ischemia. CGRP was given as single doses before, before and after, or after the ischemic insults. Pre-ischemic treatment with CGRP increased flap survival at concentrations ranging from 10(-9) mol/L to 10(-7) mol/L. The survival rate of saline and untreated control flaps was 18.4%, calculated on the basis of tissue survival areas. The optimum survival rate after preischemic CGRP treatment was 60.3%, and after both preischemic and postischemic CGRP treatment, 66.3% (p less than 0.005 as compared with controls). Given as a single dose after the ischemic period, CGRP increased flap survival to 45.5% at 10(-7) mol/L (p less than 0.05), but no effect was found at lower concentrations. Apart from free radical scavengers, CGRP is the only agent known to delay the no-reflow phenomenon after a single postischemic dose.     

Delay in neurovenous flaps: experimental and clinical experience

The objective of this study was to examine the effects of the standard surgical delay in the flaps based on the cutaneous branches of the vascular axis around a superficial sensory nerve. The delay procedure was experimentally tested in rats and subsequently used in patients.In the experimental study, the survival of a delayed inferior epigastric neurovenous flap was compared with that of a nondelayed inferior epigastric neurovenous flap. One type of clinically applicable delay pattern (standard bipedicled technique) was employed. A 3 x 3 cm flap was raised in 20 female Wistar rats assigned randomly to 2 groups. Each group consisted of 20 flaps. The standard bipedicled delay pattern increased the percentage survival of the delayed inferior epigastric neurovenous flap. The survival percentage of the delayed flaps was 59.8 +/- 185.0 (P < 0.5). The histologic findings of the skin revealed that our delay procedure enhanced the perfusion of the flap by dilating the arterial network.Stimulated by our experimental findings, we used the island bipedicled surgical flap delay or combined strategic-standard delay in the distally pedicled sural flap successfully on 9 cases.     

A novel model for supermicrosurgery training: the superficial inferior epigastric artery flap in rats

The purpose of this study was to determine the usefulness of a new flap model, the superficial inferior epigastric artery (SIEA) flap for supermicrosurgical training. Experimental groups were randomly divided into three groups of 10 rats each. In each group SIEA flaps were elevated and then returned to their original locations with or without vascular anastomosis of the superficial inferior epigastric vessels. Group 1: free SIEA flap, group 2: free SIEA flap with 1 hour ischemia time, group 3: free SIEA flap with 4 hours ischemia time, group 4: SIEA flap without vascular anastomosis. The viability rate was 80% with group 1, 50% with group 2, and 40% with group 3. All nonvascularized flaps (group 4) underwent complete necrosis. These findings suggest that preservation of blood flow in a flap has a beneficial effect on the prevention of microthrombosis in the subcutaneous capillary network of the skin and increases the flap survival rate. The SIEA flap with preserved circulation is an ideal model for developing supermicrosurgical skills.     

Effect of acute ischemic preconditioning on blood-flow response in the epigastric pedicled rat flap

Research in the field of microvascular surgery has shown that ischemic preconditioning (repeated brief episodes of feeding artery occlusions followed by reperfusion) improves flap survival. The authors used a custom-designed clamping method and laser Doppler flowmetry to investigate changes in blood flow (BF) responses, either with acute ischemic preconditioning or without it. The animal model used was the partially elevated epigastric flap of adult Sprague-Dawley rats. In the preconditioned group (n=12), the flaps underwent preconditioning with three cycles of 10-min of feeding artery clamping, followed by 10 min of reperfusion, for a total preconditioning period of 1 hr. In the control group (n=12), the flaps were perfused without clamping for 1 hr. All the flaps underwent occlusion of the feeding artery for 15, 30, 60, 120 and 180 sec to observe the changes in the BF responses, 60 min and 150 min after flap elevation. To compare the responses between preconditoned and control groups the BF responses were analyzed during the overshoot period (i.e., BF being above the baseline after different feeding artery occlusion periods). Statistical analysis of the responses showed that the magnitude of increase in BF after clamp release (p<0.001), the duration of overshoot (p=0.014), and the amplitude of overshoot after clamp release (p=0.002) were statistically significantly greater in the preconditioned group than in the control group. The results suggest that vessels and their responses to change in perfusion pressure are involved in the multifactorial process of the ischemia-protective effect caused by acute ischemic preconditioning. As far as is known, this is the first report showing changes in flap vascular responses after acute ischemic preconditioning.     

Effect of the delay phenomenon on survival of rat island skin flaps with total venous occlusion

Necrosis is an inevitable result in flaps with total venous occlusion even if arterial flow is sufficient. The purpose of this study was to investigate the effect of surgical delay on rat island skin flaps with total venous occlusion, using 20 Swiss albino rats. Two epigastric island flaps were elevated in each rat. Flaps of experimental and control groups were elevated in the same animal. In the experimental group (n=20), flap boundaries were incised down to the fascia and the incisions were sutured as a delay procedure at the first stage. After 7 days, the 3 x 6-cm epigastric island flap was elevated, the inferior epigastric vein was ligated, and was cut under X60 magnification. Then, all flaps were sutured back to their original beds. In the control group (n=20), the same surgical procedure as in the experimental group was repeated without a delay procedure. Viability was assessed at postoperative days 1, 3, and 7. At the end of day 7, all flaps in the control group were totally necrosed; however flaps in the experimental group survived partially. The surviving area ranged between 24 and 74 percent (mean: 60 +/- 15 percent). The differences between the two groups were found to be statistically significant, using Student's t-test ( p<0.005). Surgical delay could not completely save a flap with totally interrupted venous return. Nevertheless, a 60 +/- 15 percent portion of these flaps could survive with the help of a simple delay procedure.     

Effect of warm ischemia on neovascularization of island flaps.

Poor neovascularization in free-flap transfers is considered to be a consequence of insufficient hypoxic stimulus in a transferred flap with good axial-pattern circulation and a short warm ischemia time. The purpose of the study was to investigate the effect of warm ischemia time on neovascularization of axial-pattern flaps. Oblique adipomusculocutaneous groin island flaps based on the superficial epigastric vessels were raised on the right side of 21 Wistar rats, evaluated in three groups. In Group 1 (n=7), flaps were resutured without creating ischemia; in Groups 2 (n=7) and 3 (n=7), flaps were resutured after 90-min and 180-min warm ischemic periods, respectively. At 5 days postoperatively, an intravenous fluorescein test was performed following pedicle ligation, and survival was assessed by planimetric technique 7 days after pedicle ligation. Histopathologic scoring was performed according to capillary formation, inflammation, and necrosis. The intravenous fluorescein test revealed significantly higher uptake in the group with the longest ischemic period, while the mean surviving area was greater in the groups with ischemic insult, comparing to the non-ischemic group. Similarly, histopathologic scoring showed significantly higher values in the ischemic groups. The authors demonstrated that neovascularization was enhanced after 90- and 180-min warm ischemia times. The authors concluded that short ischemia time in free flaps may be an attributable factor in late flap failures, due to pedicle obstruction.     

Mesenchymal stem cells transduced by stromal cell-derived factor-1α augment ischemic free flaps' survival

Mesenchymal stem cells (MSCs) have the potential for differentiating into vascular endothelial cells. Stromal cell-derived factor-1α (SDF-1α) plays an important role in neovascularization of ischemic flaps. The authors evaluated the feasibility of applying MSCs transduced by SDF-1α gene to the treatment of early and partial ischemic free flaps survival. MSCs were isolated from Lewis rats and cultured in vitro. Recombinant adenovirus encoding SDF-1α gene (Ad-SDF-1α) was transduced into the MSCs. Lewis rats that underwent epigastric free flaps based on medial and lateral branches of superficial inferior epigastric vessels and femoral vessels were equally randomized into 4 groups, and injected with Ad-SDF-1α-transduced MSCs, MSCs, Ad-SDF-1α, and normal saline, respectively. Gene transduction, flaps survival, neovascularization, and expression level of SDF-1a protein were detected. The results showed that Ad-SDF-1α-transduced MSCs expressed higher SDF-1α both in vitro and in vivo, yielded more survival area, and resulted in higher neovascularization than any other groups. Interestingly, the necrotic sites of all free flaps were in the proximal end rather than in the distal end. In conclusion, Ad-SDF-1α-transduced MSCs can increase neovascularization of early and partial ischemic free flaps and augment the surviving areas.     

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

The effect of vascular endothelial growth factor (VEGF) on skin flap survival and its ability to induce a pharmacological delay by promoting angiogenesis in a flap was studied in a rat transverse rectus abdominis musculocutaneous flap, using a 3 x 8-cm skin paddle with the inferior epigastric vessels as its main vascular supply. Forty-three Sprague-Dawley rats were divided into four groups. In group 1, VEGF was injected into the femoral vein after the flap was elevated. In group 2, VEGF was injected intra-arterially into the flap through the superior epigastric artery after the flap was elevated. In group 3, VEGF was injected into the subcutaneous fascial layer in the area where the flap would be dissected, and the flap was then raised 7 days after injection. In group 4, the flap was dissected and replaced, using saline injection as the control. On postoperative day 5, the survival area of each skin paddle was measured and the flap was harvested for histological analysis. The results showed that the mean survival area +/- standard deviation for the skin paddle was 6.82 +/- 4.89 cm2 (28.4 +/- 20.4% of the whole skin paddle) in the control group, and 4.2 +/- 3.0 cm2 (17.5 +/- 12.5%) and 6.02 +/- 5.97 cm2 (25.1 +/- 24.9%) in the groups with VEGF systemic and intra-arterial administration respectively. The skin survival area in the group with preoperative subcutaneous administration of VEGF was 17.85 +/- 2.88 cm2 (74.4 +/- 12%), which was significantly higher than the other three groups (p < 0.01). Histological semiquantitative analysis showed increased neovascularization in the flap treated with VEGF preoperatively. The data demonstrate that preoperative treatment with VEGF can induce angiogenesis and enhance skin paddle survival in a musculocutaneous flap.     

Obesity alters rat abdominal flap survival

Obesity presents a risk factor for flap-related complications in autologous tissue breast reconstruction. In this study, an animal model was developed to examine this phenomenon. Abdominal flaps based on a superficial inferior epigastric pedicle were elevated in an experimental group of obese Zucker (fa/fa) rats (n = 8; mean weight, 413 g) and in their lean littermates (n = 9; mean weight, 276 g). Flap tissue was harvested from a subset of both groups for baseline characterization, including histology, and assays for ATP and oxidative phosphorylation uncoupler, UCP-2. Flaps were then evaluated for survival by planimetry at 4 and 7 days postprocedure. Flap survival 7 days postoperatively was reduced in obese (42.0% +/- 8.6%) versus lean (70.3% +/- 6.7%) rats (P < 0.05). At baseline, flap tissue of obese animals had decreased ATP content relative to lean counterparts (0.12 +/- 0.12 nM/microg vs 0.36 +/- 0.23 nM/microg protein, P < 0.05), whereas UCP2 mRNA was higher in obese flap tissue versus lean. Reduced viability of obese flaps may be attributable to decreased baseline energy stores due to oxidative phosphorylation uncoupling by UCP-2. This study is the first to introduce a promising animal model for examining the effect of obesity on increased flap-related complications in breast reconstruction using autologous tissue.