Searching for the right timing of surgical delay: angiogenesis, vascular endothelial growth factor and perfusion changes in a skin-flap model

Enhancing Skin Flap Survival with Preoperative Carbon Dioxide Fractional Laser Treatment: A Novel Approach in Reconstructive Surgery

BACKGROUND

Skin flap necrosis remains a significant challenge in reconstructive surgery, predominantly due to insufficient blood supply. Traditional methods like the surgical delay procedure, while effective, are invasive and associated with considerable patient discomfort and health care costs. This study explores the efficacy of Carbon Dioxide Fractional Laser (CDFL) treatment as a novel, less invasive alternative to enhance skin flap survival.

METHODS

Twenty-nine adult male Sprague-Dawley rats were divided into 2 groups: a CDFL treatment group (n=14) and a control group (n=15). The CDFL group received laser pretreatment 1 week before flap surgery, whereas the control group underwent flap surgery without pretreatment. Flap survival was assessed 7 days postsurgery using indocyanine green fluorescence angiography. In addition, histological analysis was conducted to evaluate tissue integrity, capillary density, and VEGF expression.

RESULTS

The CDFL-treated flaps showed significantly increased survival areas compared with controls (P<0.01). Histological evaluation revealed enhanced capillary dilation and increased VEGF expression in the CDFL group (P<0.05). Although capillary density was higher in the CDFL group, it did not reach statistical significance (P=0.052).

CONCLUSION

CDFL pretreatment significantly improves skin flap survival in rats, suggesting potential as a minimally invasive alternative to traditional surgical delay techniques. This approach could offer substantial benefits in reconstructive surgery, reducing patient morbidity and associated costs. Further studies are warranted to confirm these findings in clinical settings.

Extrinsic Vascular Pathway Preservation Improves Survival in a Rat Three-Territory Flap Model Based on the Deep Circumflex Iliac Artery

BACKGROUND

Extended flaps are commonly applied for large defects. However, a postoperative flap necrosis incidence of 11% to 44% remains a major complication. Previous clinical studies have shown that maintaining the extrinsic vascular pathway (EVP) can increase the survival area of extended flaps. The authors hypothesized that preserving the EVP would improve flap survival by reducing blood resistance within the vascular territory.

METHODS

Twenty-four adult male Sprague-Dawley rats were used. Tissue samples were obtained from eight untreated rats as a baseline control. Three-territory flaps were elevated in the remaining 16 rats. The EVP was preserved or ligated. Flap perfusion was assessed immediately using indocyanine green angiography. Rats were euthanized on day 7. The flap survival area was measured using Adobe Photoshop. Hematoxylin and eosin staining, CD31 immunostaining, and Western blot analysis of vascular endothelial growth factor protein expression were used to quantitatively assess vasodilation and angiogenesis in choke zones.

RESULTS

Indocyanine green angiography revealed that blood could flow through the preserved EVP and perfuse the third vascular territory of the flap. EVP preservation significantly increased flap survival area (86.3%, 19.3% difference; P < 0.001), promoted vasodilation (5.0/choke zone, 3.0/choke zone difference; P = 0.013) and angiogenesis (29.3/mm 2 , 14.3/mm 2 difference; P = 0.002), and increased vascular endothelial growth factor expression (0.6, 0.2 difference; P = 0.067) in the second choke zone.

CONCLUSIONS

EVP preservation improves flap survival in this rat three-territory flap model. Further investigation in large-animal models is required for clinical translation.

CLINICAL RELEVANCE STATEMENT

Although further validation in large animal models and prospective clinical trials are necessary to verify the efficacy of the authors' hypothesis, their findings suggest that the EVP preservation procedure could provide an alternative for surgeons to create an extended flap in defect reconstruction.

Surgical delay increases the survival of expanded random-pattern flap in pediatric patients

Despite the aid of tissue expansion, the ideal design of random pattern flap is not always available in patients with extensive skin lesions. We investigated the effectiveness of surgical delay on expanded flaps in pediatric patients. Retrospective cohort study was performed on patients who underwent tissue expansion surgery for extensive skin lesions at Seoul National University Children's Hospital. The surgical delay technique was employed for patients with unfavorable flap conditions related to location or transposition angles. The dimensions of skin lesions and flaps were measured based on medical photographs. Fifty patients underwent a total of 66 tissue expansion procedures (49 conventional procedures among 41 patients, 17 surgical delay procedures among 15 patients) from January 2016 to September 2019. Although flaps in the surgical delay group were more narrow-based (p < 0.001), the partial flap loss rate and excised area-to-inflation amount ratio was comparable between the two groups (p = 0.093 and p = 0.194, respectively). Viable flaps, excluding postoperative necrosis, in the surgical delay group were significantly more narrow-based in terms of the length-to-base width ratio and the area-to-base width ratio compared to conventional group (p < 0.01, p < 0.01). Surgical delay can result in outcomes comparable to well-designed random flaps, even in disadvantageous conditions. Patients with large skin lesions but limited areas for expansion may benefit from surgical delay.

Dermal Nipple-Areola Complex Perfusion through Circumareolar Scars: A Delay Model in Two-Stage Nipple-Sparing Mastectomy

BACKGROUND

Nipple-sparing mastectomy (NSM) has evolved as a standard surgical option. The NSM complication rate remains high in large breasts. To reduce the risk of necrosis, several authors have proposed delayed procedures to enhance blood supply to the nipple-areola complex (NAC). The purpose of this study in a porcine model was to show adequate redirection of NAC perfusion by neoangiogenesis through circumareolar scars.

METHODS

Delayed two-staged NSM was simulated in 52 nipples (six pigs) with a 60-day interval. The nipples underwent a full-thickness, circumareolar incision onto the muscular fascia, with preservation of underlying glandular perforators. After 60 days, NSM was performed through a radial incision. A silicone sheet was introduced in the mastectomy plane to prevent NAC revascularization by wound bed imbibition. Digital color imaging was used to assess necrosis. Near-infrared fluorescence with indocyanine green was used to assess perfusion patterns and perfusion in real time.

RESULTS

No NAC necrosis was seen after 60 days' delay in any nipples. In all nipples, indocyanine green angiography showed complete alteration of the NAC vascular perfusion pattern from subjacent gland to a capillary fill following devascularization, exhibiting a predominant arteriolar capillary blush without distinct larger vessels.

CONCLUSIONS

NAC delay reverses glandular perfusion to adequate dermal neovascularization. Neovascularization through full-thickness scars provides sufficient dermal perfusion after 60 days' delay. Identical staged delay in humans may be a surgically safe NSM option and could broaden therapeutic NSM indications in difficult breasts. Large clinical trials are necessary to provide identical results in human breasts.

CLINICAL RELEVANCE STATEMENT

NAC delay reverses glandular perfusion to adequate dermal neovascularization. Neovascularization through full-thickness scars provides sufficient dermal perfusion after 60 days of delay. Identical staged delay in humans may be a surgically safe NSM option.

Effectiveness of Different Surgical Flap Delay Methods and Their Systemic Toxicities

OBJECTIVE

The surgical flap delaying has been shown to be effective in preventing partial flap loss or in preparing larger flaps. However, there is no gold standard flap delay method in the literature. In this study, the authors aimed to compare 3 types of surgical delay methods to determine which model would increase more flap survival. The authors also investigated the effect of delay methods on circulating mononuclear leukocytes as a parameter of DNA damage.

METHODS

Twenty-four Sprague-Dawley male rats were divided into 4 groups. All subjects had a 10 × 3 cm modified McFarlane flap. Surface area measurements, biopsies, and blood samples were taken on the day of sacrification; 7th day for the control group and 14th day for delay groups.

RESULTS

Between incisional surgery delay groups, a significant difference was found in necrosis and apoptosis in the bipedicled group, and only necrosis in the tripedicled group compared to the control. In terms of DNA damage, it was found higher in all experimental groups than in the control group.

CONCLUSIONS

Both incisional surgical delay procedures' results were meaningfully effective when only incisions were made without the elevation of flaps. In conclusion, bipedicled incisional surgical delay seems to be the most effective method in McFarlane experimental flap model whereas two-staged surgeries may increase the risk of systemic toxicity.

Effects of microneedle length and duration of preconditioning on random pattern skin flaps in rats

To date, the surgical delay of skin flaps is the most common and reliable method that increases skin flap survival. In this study, we aimed to increase skin flap viability using preconditioning by microneedling. Seventy-two Sprague Dawley rats were randomly divided into control, surgical flap delay (SFD), and four microneedling groups (7 or 14 days of preconditioning with 0.5 mm or 1 mm needles). Modified McFarlane flaps were raised on the back of rats. In Group I, a caudal pedicled skin flap was raised and the flap survival rate was assessed on postoperative day 14. In the SFD group, a bipedicled flap was created and after 14 days of surgical delay, all skin flaps were raised. In the microneedling groups, 0.5 mm or 1 mm needles were used for 7 or 14 days. The flap survival rates of all microneedling and SFD groups were significantly higher than the control group. The plasma levels of vascular endothelial growth factor (VEGF) did not significantly differ between groups, but the VEGF level of skin samples in the SFD group was higher than the control group. The vessel counts of all microneedling and SFD groups were statistically higher than the control group in all skin samples taken before raising the flaps, but skin samples taken 14 days after raising the skin flap did not show any difference between groups. We showed that preconditioning by microneedling can be used to improve the viability of critical ischemic skin flaps at a level similar to surgical delay.

Surgical delay of anterior chest wall prior to open coronary arterial bypass grafting surgery may decrease postoperative sternal complications

Open coronary arterial bypass grafting (CABG) procedures are inherently risky in regards to the healing capacity of the subsequent sternal wound. Patients often have underlying risk factors for poor healing and the procedure itself often reduces vascularity to the anterior chest with internal mammary artery (IMA) dissection. Currently unrelated is the surgical delay procedure. It is a well-established technique for augmenting vascularity and ultimatelytissue survival. It involves partial disruption of the blood supply to a flap for a period of time prior to fully elevating the flap (usually between 3 and 21 days). Recently, endoscopic robotic IMA dissection has become possible as a part of totally endoscopic CABGs for left-sided vessel disease. We are proposing a new technique, using surgical delay for patients who require open sternotomies for CABGS to reduce the rate of postoperative sternal wound complications. To delay the CABG, the majority of a robotic internal IMA dissectionwould be performed prior to an open CABG via a midline sternotomy. We hypothesize that this may decrease sternal wound complication rates. Potential pitfalls include consequences of disrupting the normal anatomic location of the IMAs and causing inflammation before the open CABG. Animal models will be the next step, as they will evaluate the feasibility of the delay as well as help to determine the optimal timing for the procedure.

Effect of Endogenous Vascular Endothelial Growth Factor on Flap Surgical Delay in a Rat Flap Model

BACKGROUND

Experimental evidence suggests that endogenous vascular endothelial growth factor (VEGF) may play a major role in the surgical delay phenomenon. The purpose of this study was to investigate the effect of endogenous VEGF on flap surgical delay.

METHODS

A total of 82 adult male Sprague-Dawley rats with an average weight of 330 g were used for these experiments. These experiments were then conducted in two parts. In part 1, 32 rats were used to assess the effectiveness of VEGF inhibitor through Western blot assay and enzyme-linked immunosorbent assay. In part 2, 50 rats were used to investigate the effect of VEGF on flap surgical delay by means of arteriography, histologic analysis, and flap viability.

RESULTS

The VEGF protein inhibition ratio reached the maximum (approximately 91.6 percent) in 5 to 7 days. The number of transverse arteries and the number of vessels greater than 0.1 mm in diameter on the 3-day delay duration and the 6-day delay duration were significantly greater than those of the normal group. The number of transverse arteries and the number of vessels greater than 0.1 mm in diameter on the 6-day inhibition duration were not significantly changed compared with the normal group. Microvascular density on the 6-day delay duration obviously increased, whereas the 6-day inhibition duration was not significantly changed in comparison to the normal group.

CONCLUSION

Endogenous VEGF is an initiating factor of the surgical delay effect by controlling choke vessel dilation and neovascularization within the choke zones.

Comparison of subdermal and perforator delay techniques on a rat flap model

Background

In this study, we investigated the subdermal and perforator delay phenomena as a method to improve flap survival.

Materials and Methods

In this experimental study, we used 24 rats in three groups. In the control group, the dorsal flaps were elevated and reinserted back to their place. In the experimental groups, we practiced the delay phenomena with two different techniques. In the first experimental group, cranial and lateral side incisions were performed; however, the flaps were not cut-off from the underlying fascia. In the second experimental group, we placed a silicon sheet under the planned flap to cut-off the circulation from the perforator vessels. Four weeks after the delay procedure, the flaps were raised completely and reinserted back to their place.

Results

The average of necrotic area in the control group was 21.9% (±7.70). There was no necrosis in both experimental groups (P < 0.0001). Histological examination revealed that collagen density in both of the experimental groups was increased in comparison to the control group, it has only been found a significant first experimental group (P = 0.0315). We have not found any significant difference in lymphocyte density between the groups. Angiographic imaging has showed an increase in the vascular density in the flaps of the first experimental group.

Conclusion

We believe that both of these delay techniques can be adapted to clinical applications and used safely to increase flap survival.

Visualized identification of the maximal surgical delay effect in a rat flap model

Currently, experimental evidence suggests that the surgical delay can increase flap survival area, but its effect may decrease if the optimal delay period is missed. The aim of this study is to establish a sensitive and objective modality based on the visualized and individualized infrared thermography for identifying the maximal surgical delay effect. A rectangular three-angiosome flap was designed on the unilateral dorsum of the rat. Ninety-six rats were randomly divided into six groups according to the various delay time. Both the relative temperature and the relative temperature ratio were measured by the infrared thermography. Arterial density, number of vessels >0.1 mm in diameter, microvessel density, VEGF concentration, and flap viability were measured. Receiving operating characteristic curve with the highest Youden-Index was used to detect and identify an optimal cutoff point of the relative temperature ratio in the maximal surgical delay effect. The criteria for identifying the flap maximum delay effect based on the infrared thermography included the surface of the postdelayed flaps presented white color (higher temperature) instead of the red and white pattern of the normal skin and the optimal cutoff point of the relative temperature ratio was ≥1.17 with a sensitivity of 84.6% and a specificity of 77.3%. Instead, the sensitivity and specificity of the conventional method based on the delay time were 38.5 and 90.9%, respectively. Infrared thermal imaging can accurately identify the maximum delay effect when combined with the relative temperature ratio.

The Importance of Umbilical Blood Supply and Umbilical Delay in Secondary Abdominoplasty: A Case Report

LEVEL OF EVIDENCE 5

The Delay Phenomenon: Is One Surgical Delay Technique Superior?

Background:

Surgical delay remains a common method for improving flap survival. However, the optimal surgical technique has not been determined. In this article, we compare flap perfusion, viable surface area, and flap contraction of 2 surgical delay techniques.

Methods:

Male Sprague-Dawley rats were divided into 3 groups. In the incisional surgical delay group (n = 9), a 9 × 3 cm dorsal flap was incised on 3 sides without undermining, leaving a cranial pedicle. In the bipedicle surgical delay group (BSD, n = 9), a 9 × 3 cm dorsal flap was incised laterally and undermined, leaving cranial and caudal pedicles. Control group (n = 16) animals did not undergo a delay procedure. Ten days following surgical delay, all flaps for all groups were raised, leaving a cranial pedicle. A silicone sheet separated the flap and the wound bed. On postoperative day (POD) 7, viable surface area was determined clinically. Contraction compared to POD 0 was measured with ImageJ software. Perfusion was measured with Laser Doppler Imaging. The Kruskal-Wallis with Dunn’s multiple comparisons test was performed for group comparisons.

Results:

BSD preserved significantly more viable surface area on POD 7 (13.7 ± 4.5 cm²) than Control (8.7 ± 1.8 cm²; P = 0.01). BSD also showed significantly less contraction (21.0% ± 13.5%) than Control (45.9% ± 19.7%; P = 0.0045). BSD and incisional surgical delay showed significantly increased perfusion compared with Control on POD 0 (P = 0.02 and 0.049, respectively), which persisted on POD 3. This trend resolved by POD 7.

Conclusion:

BSD showed improved early perfusion, increased viable surface area, and reduced contraction compared to control, suggesting that BSD is the superior flap design for preclinical modeling.

Perforator flaps in hand reconstruction: the effect of blood vessel twisting

BACKGROUND AND AIMS

Perforator flaps increasingly find acceptance and use in hand reconstructive surgery. A propeller flap is an island flap that moves from one orientation to another by rotating around its vascular pedicle. It is now possible to design propeller flaps based on a single perforator, so-called "perforator-based propeller flaps," but they are more prone to vascular impairment when twisted more than 90°.

METHODS

We present a prospective study conducted in the Plastic and Reconstructive Surgery Department of the Rehabilitation Hospital over 17 months. All perforator-based propeller flaps that were used for hand reconstruction were analyzed. The parameters studied included the size and location of the defect, the size and shape of the flap, the perforator (length and location) that was used, the degree of twisting of the perforator, the degree of perforator dissection, the management of the donor site, and flap survival area.

RESULTS

In this study we investigated the circulatory impairment induced by twisting of the pedicle on a true perforator flap. All flaps survived completely with the exception of partial skin necrosis in few cases. Some of these cases required debridement and skin grafting.

CONCLUSIONS

Perforator-based propeller flaps provide a reliable option for covering small- to medium-size hand complex tissue defects. They have the advantages of using similar tissues in reconstruction, not damaging another area, they do not require main vessels sacrifice, and the donor site can be generally directly closed.

AdVEGF-All6A+ Preconditioning of Murine Ischemic Skin Flaps Is Comparable to Surgical Delay

Background:

Surgical flap delay is commonly used in preconditioning reconstructive flaps to prevent necrosis. However, staged procedures are not ideal. Pharmacologic up-regulation of angiogenic and arteriogenic factors before flap elevation poses a nonsurgical approach to improve flap survival.

Methods:

Male Sprague Dawley rats were divided into control (n = 16), surgical delay (Delay), AdNull, AdEgr-1, and AdVEGF (n ≥ 9/group) groups. Delay rats had a 9 cm × 3 cm cranial based pedicle skin flap incised 10 days prior to elevation. Adenoviral groups received 28 intradermal injections (10⁹ pu/animal total) throughout the distal two thirds of the flap 1 week prior to elevation. At postoperative day (POD) 0 flaps were elevated and silicone sheeting was placed between flap and wound bed. Perfusion analysis in arbitrary perfusion units of the ischemic middle third of the flap using laser Doppler imaging was conducted preoperatively and on POD 0, 3, and 7. Clinical and histopathologic assessments of the skin flaps were performed on POD 7.

Results:

AdVEGF (50.8 ± 10.9 APU) and AdEgr-1 (39.3 ± 10.6 APU) perfusion levels were significantly higher than controls (16.5 ± 4.2 APU) on POD 7. Delay models were equivalent to controls (25.9 ± 6.8 APU). AdVEGF and Delay animals showed significantly more viable surface area on POD 7 (14.4 ± 1.3 cm², P < 0.01 and 12.4 ± 1.2 cm², P < 0.05, respectively) compared with Controls (8.7 ± 0.7 cm²).

Conclusions:

AdVEGF preconditioning resulted in flap survival comparable to surgical delay. Adenoviral preconditioning maintained perfusion levels postoperatively while surgical delay did not.

Delayed platysma myocutaneous turnover flap for repair of pharyngocutaneous fistula

INTRODUCTION

Pharyngocutaneous fistula (PCF) is a common and serious complication after total laryngectomy. Numerous surgical and non-surgical treatment approaches have been described. Here we describe a platysma myocutaneous turnover flap for repair of PCF.

MATERIALS AND METHODS

Platysma myocutaneous turnover flap is described and two patients are used as examples.

RESULTS

Repair was initially successful in both patients; however, one patient had recurrence of fistula after her cancer recurred at the stoma.

DISCUSSION

Numerous surgical techniques have been described for repair of PCF. Here a turnover flap was used, a technique not previously described for this problem. The delay technique enhances the viability of the flap thought to be through numerous mechanisms.

CONCLUSION

The platysma myocutaneous turnover flap is useful for closure of pharyngocutaneous fistula when non-operative measures have failed.

Delay by Staged Elevation of Flaps and Importance of Inclusion of the Perforator Artery

"Surgical delay" is aimed at increasing blood flow to adjacent angiosomes by opening choke vessels, to obtain larger and more reliable flaps. We hypothesized that staged elevation (delay) from distal to proximal, in addition to preservation perforator artery near the base will improve survival. Thirty-two Sprague-Dawley rats were divided into 4 groups and 3x8cm caudal McFarlane flaps were elevated. In "delay" groups the 3 × 4 cm distal part was elevated and sutured back, with complete elevation (3 × 8 cm) after 4 days. The deep circumflex iliac artery (DCIA) at the base was either preserved or transected. The groups were: group A (Delay/DCIA preserved), group B (Delay/DCIA transected), group C (No Delay/DCIA preserved), group D (No Delay/DCIA transected). The percentage of surviving flap area was measured after 7 days with digital planimetrics. Statistics were done with ANOVA and unpaired T-test. The survivals were: 98.44 ± 3.13 %(group A), 69.33 ± 5.51 %(group B), 76.50 ± 8.91 %(group C) and 52.89 ± 3.15 %(group D). Delay lead to a greater degree of survival whether the arteries were preserved (p = 0.002) or transected (p = 0.01). In groups where the DCIA was preserved, the delay lead to a greater area of survival (p = 0.002). Inclusion of arteries lead to a greater degree of survival whether delay was performed (p = 0.003) or not (p = 0.005). Necropsy showed that the DCIAs were dilated bilaterally when preserved with vascular arcades reaching all viable areas. When the DCIA was transected, the gluteal perforators were dilated bilaterally with the vascular arcades reaching all viable areas. Staged elevation is an effective method of delay in both random and rando-axial flaps. When this is combined with preserving the perforator artery, survival rates are further enhanced.

Complications of the angularis oris axial pattern buccal flap for reconstruction of palatine defects in two dogs

CASE REPORT

Complications associated with surgical reconstruction of hard palate defects with a buccal mucosal flap based on the angularis oris artery and vein in two dogs are described. Distal flap necrosis occurred in both cases, but the flaps were successfully salvaged by division of the original flap pedicle and rotation of the flap material into the remaining defect. Postoperative dysphagia was observed in both dogs until flap revision. Salvage of the intact distal portion of the flap following division of the direct artery and vein 14 days postoperatively is discussed.

CONCLUSION

The angularis oris axial pattern buccal flap is an option for reconstruction of large defects of the hard palate. Survival of the flap can be improved by removal of teeth likely to cause occlusal trauma to the flap's pedicle. In the event of distal flap necrosis, the repair may be salvaged by rotation of the remaining flap into the defect, following establishment of vascular supply from adjacent tissue.

The use of a dermal substitute for simultaneous flap delay and donor site coverage in two cases

OBJECTIVE

Lower extremity traumatic wounds can be difficult to treat owing to limb ischaemia and large zones of injury. Often, muscle or fasciocutaneous flaps are used in the presence of severe open orthopaedic injuries with soft tissue defects. Sometimes local flaps may be the preferred or only option, but may not tolerate being rotated or advanced owing to resulting flap ischaemia. One well-studied technique that can increase the survival of various flaps involves the delay phenomenon.

METHOD

In these case reports, Integra Dermal Regeneration template was used to simultaneously create delayed flaps and to cover the wound and flap donor site so that the donor site could be skin grafted at the time of flap inset.

RESULTS

These cases demonstrate that use of Integra can enhance the delay phenomenon while simultaneously providing coverage of soft tissue defects in preparation for ultimately insetting delayed flaps and better covering donor areas.

CONCLUSION

This technique may be applicable to many different flaps in many different anatomic locations and should be considered an option when reconstructing complicated wounds.

DECLARATION OF INTEREST

none.

Adipose-derived stem cells and keratinocytes in a chronic wound cell culture model: the role of hydroxyectoine

Chronic wounds represent a major socio-economic problem in developed countries today. Wound healing is a complex biological process. It requires a well-orchestrated interaction of mediators, resident cells and infiltrating cells. In this context, mesenchymal stem cells and keratinocytes play a crucial role in tissue regeneration. In chronic wounds these processes are disturbed and cell viability is reduced. Hydroxyectoine (HyEc) is a membrane protecting osmolyte with protein and macromolecule stabilising properties. Adipose-derived stem cells (ASC) and keratinocytes were cultured with chronic wound fluid (CWF) and treated with HyEc. Proliferation was investigated using MTT test and migration was examined with transwell-migration assay and scratch assay. Gene expression changes of basic fibroblast growth factor (b-FGF), vascular endothelial growth factor (VEGF), matrix metalloproteinases-2 (MMP-2) and MMP-9 were analysed by quantitative real-time polymerase chain reaction (qRT-PCR). CWF significantly inhibited proliferation and migration of keratinocytes. Addition of HyEc did not affect these results. Proliferation capacity of ASC was not influenced by CWF whereas migration was significantly enhanced. HyEc significantly reduced ASC migration. Expression of b-FGF, VEGF, MMP-2 and MMP-9 in ASC, and b-FGF, VEGF and MMP-9 in keratinocytes was strongly induced by chronic wound fluid. HyEc enhanced CWF induced gene expression of VEGF in ASC and MMP-9 in keratinocytes. CWF negatively impaired keratinocyte function, which was not influenced by HyEc. ASC migration was stimulated by CWF, whereas HyEc significantly inhibited migration of ASC. CWF induced gene expression of VEGF in ASC and MMP-9 in keratinocytes was enhanced by HyEc, which might partly be explained by an RNA stabilising effect of HyEc.

Acute and chronic wound fluids influence keratinocyte function differently

Wound healing requires a proper functioning of keratinocytes that migrate, proliferate and lead to a competent wound closure. Impaired wound healing might be due to a disturbed keratinocyte function caused by the wound environment. Basically, chronic wound fluid (CWF) differs from acute wound fluid (AWF). The aim of this study was to analyse the effects of AWF and CWF on keratinocyte function. We therefore investigated keratinocyte migration and proliferation under the influence of AWF and CWF using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] test and scratch assay. We further measured the gene expression by qRT-PCR regarding growth factors and matrixmetalloproteinases (MMPs) involved in regeneration processes. AWF had a positive impact on keratinocyte proliferation over time, whereas CWF had an anti-proliferative effect. Keratinocyte migration was significantly impaired by CWF in contrast to an undisturbed wound closure under the influence of AWF. MMP-9 expression was strongly upregulated by CWF compared with AWF. Keratinocyte function was significantly impaired by CWF. An excessive induction of MMP-9 by CWF might lead to a permanent degradation of extracellular matrix and thereby prevent wounds from healing.

Acute and chronic wound fluids inversely influence adipose-derived stem cell function: molecular insights into impaired wound healing

Wound healing is a complex biological process that requires a well-orchestrated interaction of mediators as well as resident and infiltrating cells. In this context, mesenchymal stem cells play a crucial role as they are attracted to the wound site and influence tissue regeneration by various mechanisms. In chronic wounds, these processes are disturbed. In a comparative approach, adipose-derived stem cells (ASC) were treated with acute and chronic wound fluids (AWF and CWF, respectively). Proliferation and migration were investigated using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test and transwell migration assay. Gene expression changes were analysed using quantitative real time-polymerase chain reaction. AWF had a significantly stronger chemotactic impact on ASC than CWF (77·5% versus 59·8% migrated cells). While proliferation was stimulated by AWF up to 136·3%, CWF had a negative effect on proliferation over time (80·3%). Expression of b-FGF, vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 was strongly induced by CWF compared with a mild induction by AWF. These results give an insight into impaired ASC function in chronic wounds. The detected effect of CWF on proliferation and migration of ASC might be one reason for an insufficient healing process in chronic wounds.

A review of indocyanine green fluorescent imaging in surgery

The purpose of this paper is to give an overview of the recent surgical intraoperational applications of indocyanine green fluorescence imaging methods, the basics of the technology, and instrumentation used. Well over 200 papers describing this technique in clinical setting are reviewed. In addition to the surgical applications, other recent medical applications of ICG are briefly examined.

Optimal timing of extracorporeal shock wave treatment to protect ischemic tissue

Enhancement of flap survival through extracorporeal shock wave treatment (ESWT) is a promising new technique; however, no attempt has been made to define the optimal time point and frequency of ESWT to optimize treatment with ESWT for ischemic indications. Twenty-eight male Wistar rats were randomized into 4 groups and an oversized, random-pattern flap was raised and reattached in place in each animal. ESWT was applied 7 days before (group E7) or immediately after the surgical intervention (group E0). The third group was treated with ESWT 7 days before and additionally immediately after the operation (group E7/0). The fourth group served as a control group and did not receive any ESWT (group C). Seven days after flap harvest the results of flap survival, perfusion, microvessel density, and vascular endothelial growth factor concentrations were assessed. Flap survival was significantly increased in all ESWT groups as compared with the control group. The groups (E7 and E0) that received ESWT pre- or postoperatively showed a significant increase in flap perfusion and microvessel density. Combined pre- and postoperative ESWT application (group E0/E7) did not demonstrate a cumulative effect in any evaluation. In this study, we were be able to prove the effectiveness of ESWT in the protection of ischemic tissue flaps. This study suggests that single postoperative application is the most efficacious protocol for clinical applications of ESWT in the treatment of ischemic tissue.

Priming with a combination of proangiogenic growth factors improves wound healing in normoglycemic mice

Growth factors and/or angiogenic factors are supposed to improve wound healing. The aim of our study was to evaluate the effects of subcutaneous pretreatment with combinatory proangiogenic factors on wound closure, mechanical properties, vessel density and morphology. Twenty-eight Balb/c mice were divided equally into two groups. A mixture of VEGF (35.0 µg), bFGF (2.5 µg) and PDGF (3.5 µg) was administered subcutaneously 3, 5 and 7 days to 14 mice before full thickness skin punch biopsy wounding, whereas 14 control animals received three injections of 0.2 ml saline solution. Wound sizes were assessed daily and the repaired tissues were harvested 7 days after complete wound closure. Complete closure (≥ 95% healing of initial wound area) was reached in all proangiogenic pretreated animals on day 10, whereas controls needed 13 days for complete closure. Tensile strengths were nearly twofold higher compared to the controls (p ≤ 0.01). The punch biopsy material revealed 4.2-fold higher vessel densities in the proangiogenic pretreated group. On day 17, the vessel densities in the proangiogenic pretreated wounds were also 3.2-fold higher compared to the untreated controls. No significant differences were seen in the collagen ratio. Pretreatment with proangiogenic factors revealed several significant effects on wound healing: faster time to closure, a higher vessel density and a better functional outcome. These results suggest a beneficial effect of pretreatment with combinatory growth factors in mouse skin wounds without impaired wound healing. This might be exploited in further investigations in diabetic healing as a therapeutic approach for elective surgery.

Non-viral VEGF(165) gene therapy--magnetofection of acoustically active magnetic lipospheres ('magnetobubbles') increases tissue survival in an oversized skin flap model

Adenoviral transduction of the VEGF gene in an oversized skin flap increases flap survival and perfusion. In this study, we investigated the potential of magnetofection of magnetic lipospheres containing VEGF₁₆₅-cDNA on survival and perfusion of ischemic skin flaps and evaluated the method with respect to the significance of applied magnetic field and ultrasound. We prepared perfluoropropane-filled magnetic lipospheres (‘magnetobubbles’) from Tween60-coated magnetic nanoparticles, Metafectene, soybean-oil and cDNA and studied the effect in an oversized random-pattern-flap model in the rats (n= 46). VEGF-cDNA-magnetobubbles were administered under a magnetic field with simultaneously applied ultrasound, under magnetic field alone and with applied ultrasound alone. Therapy was conducted 7 days pre-operative. Flap survival and necrosis were measured 7 days post-operatively. Flap perfusion, VEGF-protein concentration in target and surrounding tissue, formation and appearance of new vessels were analysed additionally. Magnetofection with VEGF-cDNA-magnetobubbles presented an increased flap survival of 50% and increased flap perfusion (P < 0.05). Without ultrasound and without magnetic field, the effect is weakened. VEGF concentration in target tissue was elevated (P < 0.05), while underlying muscle was not affected. Our results demonstrate the successful VEGF gene therapy by means of magnetobubble magnetofection. Here, the method of magnetofection of magnetic lipospheres is equally efficient as adenoviral transduction, but has a presumable superior safety profile.