Biomechanical properties of thin skin flap after basic fibroblast growth factor (bFGF) administration

The Effect of Growth Factors on Vaginal Wound Healing: A Systematic Review and Meta-analysis

Surgical outcomes of pelvic organ prolapse (POP) surgery are poor, resulting in a 20% recurrence risk. Following the hypothesis that impaired wound healing is the main determinant of recurrent POP, growth factors have the potential to promote wound healing and may improve surgical outcomes. In this study, we systematically reviewed the effect of growth factors on vaginal wound healing in both in vitro and animal studies. For each independent comparison, the standardized mean difference and 95% CI were calculated using the Hedges' g correction. Of the 3858 retrieved studies, seven studies were included, of which six were included in meta-analysis (three in vitro studies and four in vivo studies). In vitro, basic fibroblast growth factor (bFGF) promotes proliferation, differentiation, and collagen types I and III production. Epidermal growth factor stimulates proliferation and connective tissue growth factor promotes Tenascin-C expression. These effects, however, are less pronounced in vivo; only bFGF slightly promotes collagen production. The review shows that growth factors, particularly bFGF, are able to promote vaginal wound healing in vitro. The uncertain in vivo findings suggest that preclinical models should be improved. The ultimate goal is to develop effective growth factor-supplemented therapies that improve surgical outcomes for POP.

Photocrosslinked gelatin hydrogel improves wound healing and skin flap survival by the sustained release of basic fibroblast growth factor

Biomaterials traditionally used for wound healing can act as a temporary barrier to halt bleeding, prevent infection, and enhance regeneration. Hydrogels are among the best candidates for wound healing owing to their moisture retention and drug-releasing properties. Photo-polymerization using visible light irradiation is a promising method for hydrogel preparation since it can easily control spatiotemporal reaction kinetics and rapidly induce a single-step reaction under mild conditions. In this study, photocrosslinked gelatin hydrogels were imparted with properties namely fast wound adherence, strong wet tissue surface adhesion, greater biocompatibility, long-term bFGF release, and importantly, ease of use through the modification and combination of natural bio-macromolecules. The production of a gelatin hydrogel made of natural gelatin (which is superior to chemically modified gelatin), crosslinked by visible light, which is more desirable than UV light irradiation, will enable its prolonged application to uneven wound surfaces. This is due to its flexible shape, along with the administration of cell growth factors, such as bFGF, for tissue regeneration. Further, the sustained release of bFGF enhances wound healing and skin flap survival. The photocrosslinking gelatin hydrogel designed in this study is a potential candidate to enhance wound healing and better skin flap survival.

Use of ovine acellular peritoneal matrix combined with honey and ovine fetal skin extract in the healing of full-thickness infected burn wounds in a rat model

Treatment of infected burn wounds remains a challenge in burn units. Silver-sulfadiazine (SSD) is the most commonly used topical antimicrobial agent in managing these wounds. We aimed to accelerate the healing of burn wounds by combined application of ovine acellular peritoneal matrix (OAPM), honey (H), and ovine fetal skin extract (OFSE). Sixty-four standardized burn wounds were created on the dorsum of 16 rats and were subsequently inoculated with Staphyloccocus aureus and Pseudomonas aeruginosa. After 48 hr, the wounds were surgically debrided and received either physiologic saline (control group) or SSD, OAPM+SSD, OAPM+H+SSD, and OAPM+H+OFSE+SSD. The healing wounds were evaluated for size, bacterial counts, histopathology, and biomechanical properties on days 3, 7, 14, 21, and 28 after surgery. All treatments had effectively reduced the level of S. aureus and P. aeruginosa on wounds compared to the control group by day 3 and 7. The wounds treated with combined application of OAPM+H+OFSE+SSD demonstrated considerable inflammation reduction, fibroplasia, complete re-epithelialization, and wound contraction together with significantly lesser scar tissue formation. Treatment with OAPM+H+OFSE+SSD showed superior biomechanical properties of the healing wounds. The findings suggested that the synergistic effect of dressing the wounds with OAPM, H, and OFSE was a very effective approach in accelerating the healing process of the experimentally induced infected full-thickness burn wounds in rats.

Improvement of Flap Necrosis in a Rat Random Skin Flap Model by In Vivo Electroporation-Mediated HGF Gene Transfer

BACKGROUND

Despite great understanding of underlying mechanisms for flap necrosis and advances in surgical techniques, flap necrosis remains a critical issue. In the present study, the authors investigated the efficacy of electroporation-mediated hepatocyte growth factor (HGF) gene delivery to random dorsal skin flaps (McFarlane) to accelerate wound healing and reduce flap necrosis.

METHODS

Fifteen male Wistar rats (290 to 320 g) were divided randomly into three groups. Group a, the control group (n = 5), underwent surgery and received no gene transfer. Group b received electroporation-mediated HGF gene delivery 24 hours after surgery as a treatment. Group c received electroporation-mediated HGF gene delivery 24 hours before surgery as prophylaxis (n = 5). Planimetry, laser Doppler imaging, and immunohistochemistry were used to assess the efficacy of HGF gene therapy among the groups.

RESULTS

Electroporation-mediated HGF gene delivery significantly decreased flap necrosis percentage compared with the control group in prophylactic and treatment groups (p = 0.0317 and p = 0.0079, respectively) and significantly increased cutaneous perfusion compared with the control group (p = 0.0317 and p = 0.0159, respectively). Moreover, Spearman rank correlation showed a significant negative correlation between flap necrosis percentage and laser index (p = 0.0213 and r = -0.5964, respectively). Furthermore, significantly higher mean CD31 vessel density was detected in treatment and prophylactic groups (p = 0.0079 and p = 0.0159, respectively). In addition, quantitative image analysis revealed significantly higher HGF protein expression in groups b and c (p = 0.0079 and p = 0.0079, respectively).

CONCLUSION

These findings suggested in vivo electroporation-mediated HGF gene delivery enhanced viability and vascularity of the ischemic skin flap.

Aziz SH, Zakaria AD. Effect of Tualang honey on the anastomotic wound healing in large bowel anastomosis in rats-A randomized controlled trial

Background

Honey has long been used for the treatment of number of ailments and diseases including surgical wounds. Current study evaluates the effectiveness of Tualang honey (TH) for large bowel anastomotic healing in Wistar rats.

Methods

Thirty male Wistar rats were given a 3 centimeter infra-umbilical laparotomy wound, in`flicted on their abdomen. The colonic transection was performed at 5 cm distal to caecum, with end to end anastomosis of colon segment. They were divided into two groups. Group I was fed with standard rat chow and water. Meanwhile, Group II apart from standard feed, was also given TH 1.0 g/kg every morning until day seven post operatively. Afterwards, anastomotic bursting pressures were measured and histopathological examination on the anastomosis line was performed with light microscopes. The data from two groups were analyzed by Independent paired t test for continuous variables.

Results

It was found that the tensile strength of colon anastomosis (95 % CI; p = <0.001) and the histopathological study including fibroblast count (p = <0.001) and inflammatory cells (p = 0.002) showed statistically significant difference in the favor of TH-treated group. Meanwhile, neovascularization formation was not statistically significant (p = 0.807); however, the overall count in the TH group was high.

Conclusion

Oral treatment with TH enhances anastomotic wound healing by increasing the number of fibroblasts and by decreasing inflammatory cells leading towards increased wound strength.

Detecting the developmental toxicity of bFGF in the embryonic stem cell test using differential gene expression of differentiation-related genes

Basic fibroblast growth factor (bFGF) is a mitogenic cytokine that can stimulate mesoderm-and neuroectoderm-originated cell proliferation. This study was performed to investigate the effects of bFGF on cell differentiation and the expression of specific markers at different embryonic developmental stages. We firstly evaluated the embryotoxic potential of bFGF in vitro using a modified EST protocol. Sequentially, we further investigated how bFGF impact the different tissue-special genes and proteins expressions during the differentiation of murine ES cells in vitro and attempt to reveal the effects of bFGF on differentiation processes. This analysis was focused on key tissue- and stage-specific genes involved in ectodermal, mesodermal, and endodermal differentiation, including ectodermal-specific gene Nestin, Oligo2 and Syn, mesodermal-specific gene MHC and MyoD, and endodermal-specific gene GATA6, TTR and ALB, as well as undifferentiated gene Sox-2 and Oct-4. The results demonstrate that bFGF could promote expression of ectodermal-specific genes and protein, but suppress the expressions of endoderm-specific and some mesoderm-specific gene and protein. A conclusion can be drawn that bFGF exhibits weak embryotoxicity and mainly promotes ES cell differentiation towards the ectodermal lineages but suppress differentiation into endoderm lineages. These opposing effects of bFGF on the embryonic development of the three germ layers may be related to its weak embryotoxic potential. More specifically, inhibition of expression of the endodermal-specific markers transthyretin (TTR), and albumin (ALB) by bFGF may be of more value in detecting the embryotoxic potential of bFGF.

Effects of stromal cell derived factor-1 and CXCR4 on the promotion of neovascularization by hyperbaric oxygen treatment in skin flaps

Hyperbaric oxygen (HBO) is known to increase the survival of skin flaps by promoting neovascularization; however, the detailed mechanisms involved are not fully understood. In the present study, we aimed to characterize the effects of HBO treatment on neovascularization and skin flap survival. We also analyzed the mechanisms associated with the expression of angiogenic molecules, such as stromal cell derived factor-1 (SDF‑1) and its specific receptor CXCR4, to assess the effects of SDF-1 and CXCR4 on the promotion of neovascularization by HBO treatment in skin flaps. The epigastric pedicle skin flap model was established in rats that were randomly divided into the following groups: i) sham‑operated (SH group); ii) ischemia followed by reperfusion and analysis on the third and fifth day (IR3d and IR5d groups, respectively) postoperatively; iii) ischemia followed by reperfusion, HBO treatment and analysis on the third and fifth day (HBO3d and HBO5d groups, respectively) postoperatively. In the two HBO groups, animals received 1 h of HBO treatment in a 2.0 ATA chamber with 100% O2 twice per day for 3 days and then daily for 2 consecutive days following surgery. On the postoperative third and fifth day, skin flap survival measurement, histological analysis, immunohistochemical staining and western blotting for SDF‑1 and CXCR4 expression, were performed. Compared with those of the IR groups, skin flap survival, microvessel density (MVD) and expression of SDF‑1 and CXCR4 proteins were significantly increased in the HBO groups. Pearson's correlation analysis demonstrated a positive correlation between MVD and the high expression of SDF‑1 and CXCR4 following HBO treatment. Results of this study suggested that the effects of HBO treatment in promoting neovascularization may be explained by the upregulation of SDF‑1 and CXCR4 expression in the skin flaps of rats.

Biomechanical properties of in vivo human skin from dynamic optical coherence elastography

Dynamic optical coherence elastography is used to determine in vivo skin biomechanical properties based on mechanical surface wave propagation. Quantitative Young's moduli are measured on human skin from different sites, orientations, and frequencies. Skin thicknesses, including measurements from different layers, are also measured simultaneously. Experimental results show significant differences among measurements from different skin sites, between directions parallel and orthogonal to Langer's lines, and under different skin hydration states. Results also suggest surface waves with different driving frequencies represent skin biomechanical properties from different layers in depth. With features such as micrometer-scale resolution, noninvasive imaging, and real-time processing from the optical coherence tomography technology, this optical measurement technique has great potential for measuring skin biomechanical properties in dermatology.

Accelerated wound closure of pressure ulcers in aged mice by chitosan scaffolds with and without bFGF

Pressure ulcers are a significant healthcare concern, especially for elderly populations. Our work served to ameliorate the chronicity of these ulcers by addressing ischemia-reperfusion injury mediated by neutrophils and the concomitant loss of vasculature in these wounds. To this end, chitosan scaffolds loaded with basic fibroblast growth factor (bFGF) contained in gelatin microparticles were developed and tested for clinical relevance in an aged mouse model. Pressure ulcers were induced in aged mice, and efficacy of treatment was assessed. On days 3 and 7, both chitosan and chitosan-bFGF scaffolds significantly accelerated wound closure compared to gauze control. By day 10, all wounds achieved similar closure. Delivery and angiogenic function of bFGF was verified through ELISA and histology. Elevated neutrophil levels were observed in chitosan and chitosan-bFGF groups. Since neutrophil elastase contributes to the proteolytic environments of pressure ulcers, the effect of chitosan on elastase was assessed. In vitro, chitosan inhibited elastase activity. In vivo, elastase protein levels in wounds were reduced with chitosan-bFGF scaffolds by day 10. These results suggest that chitosan is an effective material for growth factor delivery and can help to heal chronic ulcers. Collectively, our data show that chitosan-bFGF scaffolds are effective in accelerating wound closure of pressure ulcers in aged animals.

Exposure to gamma rays induces early alterations in skin in rodents: Mechanical, biochemical and structural responses

In this study, the effect of gamma rays has been investigated on the normal rat skin using biomechanical, biochemical and histological techniques. Seventeen male Wistar albino rats were divided into two groups (control (n=7) and irradiated (n=10)). The irradiated group was treated with a (60)Co gamma source at a dose of 10Gy at room temperature. Skin biomechanics were measured with tensile test using biomaterial testing machine and maximum load, stiffness, energy absorption capacity, ultimate stress, ultimate strain and elastic modulus were calculated. In the irradiated group, energy, strain and toughness were significantly lower than in the control group (p<0.05). However, strength, displacement, stiffness, stress and elastic modulus were similar to that of the control group (p>0.05). Catalase (CAT) activities and the levels of malondialdehyde (MDA) in the skin of rats were measured using the biochemical methods. MDA levels significantly increased whereas CAT activities decreased in the irradiated group as compared with the control group (p<0.05). Diameters of collagen fibers were measured by transmission electron microscopy. There was no significant difference (p>0.05) between control and irradiated groups for collagen fiber diameter. Thickness of epidermis was significantly lower than the control group. There were no changes in the epidermis between the irradiated group and the control group ultrastructurally. The results of this study show that the gamma irradiation has a significant effect on normal healthy skin.

Wound dressings containing bFGF-impregnated microspheres

The primary objective was to synthesize a novel wound dressing containing basic fibroblast growth factor (bFGF)-loaded microspheres for promoting healing and tissue regeneration. Gelatin sponge was chosen as the underlying layer and elastomeric polyurethane membranes were used as the external layer. To achieve prolonged release, bFGF addition was loaded in microspheres. The microspheres were characterized for particle size, in vitro protein release and bioactivity. The bilayer dressings were tested in in vivo experiments on full-thickness skin defects created on pigs. Average size of the microspheres was 14.36 +/- 3.56 microm and the network sponges were characterized with an average pore size of 80-160 microm. Both the in vitro release efficiency and the protein bioactivity revealed that bFGF was released in a controlled manner and it was biologically active as assessed by its ability to induce the proliferation of fibroblasts. It was observed that sustained release of bFGF provided a higher degree of reduction in the wound areas. Histological investigations showed that the dressings were biocompatible and did not cause any mononuclear cell infiltration or foreign body reaction. The structure of the newly formed dermis was almost the same as that of the normal skin. The application of these novel bilayer wound dressings provided an optimum healing milieu for the proliferating cells and regenerating tissues in pig's skin defect models.

Fibrin-embedded administration of VEGF plasmid enhances skin flap survival

The aim of the present study was to experimentally evaluate whether topical fibrin-mediated administration of a vascular endothelial growth factor (VEGF)-A plasmid to the wound bed can protect skin flaps from necrosis. A plasmid expression vector containing the VEGF-A cDNA was constructed. The plasmid was then administered to the wound bed of rat abdominal skin flaps in a fibrin sealant. The percentage of viable, ischemic and necrotic tissue was assessed postoperatively as a baseline and after 3 and 7 days using digital surface area morphometry. Laser Doppler imaging of the flaps and VEGF-A Western blot analysis of flap tissue were performed to assess angiogenesis and VEGF-A tissue levels. Flaps treated with VEGF plasmids in the presence of uptake enhancing Lipofectamine transfection reagent increased flap survival 7 days postoperatively significantly associated with markedly elevated tissue perfusion and enhanced tissue VEGF-A protein expression. Our results indicate that topical fibrin-mediated administration of a VEGF-A plasmid may serve as an alternative to previous strategies in treating ischemic skin flaps. The suggested therapeutic approach is easily applicable and inexpensive in preparation. Thus, this protocol may also enhance wound healing in posttrauma skin lacerations or in skin grafts.

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

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

Effect of dermal thickness, tissue composition, and body site on skin biomechanical properties

BACKGROUND/PURPOSE

Quantitative measurement of skin biomechanical properties has been used effectively in the investigation of physiological changes in tissue structure and function and to determine treatment efficacy. As the methods are applied to new questions, tissue characteristics that may influence the resultant biomechanical properties are important considerations in the research design. For certain applications, variables such as dermal thickness and subdermal tissue composition, as well as age and/or solar exposure, may influence the skin biomechanics.

METHODS

We determined the influence of dermal thickness, tissue composition, and age on the skin biomechanical properties at the shoulder, thigh, and calf among 30 healthy females. We compared two devices, the Biomechanical Tissue Characterization System and the Cutometer SEM 575 Skin Elasticity Meter , to determine the effect of tissue sampling size. Dermal thickness was measured with 20 MHz ultrasound (Dermascan C) and tissue composition was inferred from anthropomorphic data.

RESULTS

Skin thickness was significantly correlated with stiffness, energy absorption, and U(r)/U(f) for the shoulder. Body mass index (BMI) was significantly correlated with stiffness (negative correlation), energy absorption (positive), and skin thickness (negative) for the shoulder. Significant differences across body sites were observed. The calf was significantly different from the thigh and shoulders for all parameters (P<0.05, one-way anova). The calf had significantly lower laxity, laxity%, elastic deformation, energy absorption, elasticity, elasticity %, U(r), U(f), and U(r)/U(f) and significantly higher stiffness compared with the thighs and shoulders. sites. The thigh and shoulder sites were significantly different for all parameters except U(r)/U(f), elasticity %, laxity%, and stiffness. The dominant and non-dominant sides were significantly different. The dominant side (right for 90% of the subjects) had increased stiffness and decreased energy absorption (tissue softness, compliance) compared with the left side. A significant (P< or =0.02) negative relationship with age was seen for all biomechanical measures except stiffness at the shoulder. For the thigh and calf sites, significant negative correlations with age were found for elasticity %, U(r), and U(r)/U(f). Age and skin thickness were not correlated in this population. Skin thickness and age influenced the energy absorption at the shoulder site. The biological elasticity at the calf site could be predicted by age and BMI. The biological activity at the thigh site could be predicted by skin thickness and BMI.

CONCLUSIONS

Significant regional variations in biomechanical properties and dominant side effects were observed. The biomechanical properties were significantly influenced by age. Certain properties varied with dermal thickness and tissue composition. The parameters were well correlated between the two instruments. The Cutometer, with its smaller aperture, was found to be more sensitive to age relationships.

Growth factors and flap survival

Growth factors are members of a large functional group of polypeptide regulatory molecules that influence the biological activities of responsive cells. In the last decade, the use of a variety of growth factors as therapeutic agents to improve wound healing and the viability of ischemic skin flaps has aroused considerable interest. Here, we review the literature concerning the regulation of growth factors in a flap, the role of angiogenesis in flap survival, the effect of growth factors on the metabolism of a flap, and angiogenesis in flap prefabrication and maturation. The potential application of growth factors in gene therapies is also reviewed.

Gene therapy in flap survival

Growth factors are members of a large functional group of polypeptide regulatory molecules that exert a powerful influence on all phases of wound healing and repair through interactions with specific cell surface receptors. The use of growth factors to improve wound healing and the viability of ischemic skin flaps has been well-documented throughout the last decade. In this article, we review the literature concerning the use gene therapy in flap survival, including the various methods employed to transplant plasmids or viruses capable of coding and producing growth factors in ischemic tissue.

Efeitos do fator de crescimento de fibroblasto básico (FCFbeta) na cicatrização de anastomoses do esôfago

OBJETIVO: Os fatores de crescimento são substâncias moduladoras do processo de cicatrização. O fator de crescimento de fibroblastos básico (FCFbeta) liberado pelas plaquetas, macrófagos e pelos próprios fibroblastos, estimulam a proliferação celular, a produção de colágeno e de outros elementos da matriz celular, favorecendo o processo da cicatrização, mesmo em situações adversas, como diabetes e uso de corticosteróides. O presente estudo objetivou determinar a influência do FCFbeta no processo de cicatrização de anastomoses esofageanas em modelo de experimentação animal, avaliando-se a resistência à pressão, formação de tecido de granulação e deposição de colágeno. MÉTODO: Foram estudados dois grupos A e B, ambos com 10 ratos de linhagem Wistar, separados de forma aleatória, todos submetidos à secção e anastomose do esôfago por via abdominal. Nos animais do grupo A, foi feita aplicação tópica na linha de sutura de 10ng de FCFbeta. No grupo B (controle) foi aplicado igual volume de solução salina. Os animais foram sacrificados no 7º dia, o esôfago ressecado para teste de resistência da anastomose, estudo qualitativo do aporte de células inflamatórias, da angiogênese e quantificação do colágeno na zona da anastomose, através de sistema digital. RESULTADO: A densidade média dos parâmetros histológicos do grupo A foi 9095,51±1284,5, maior que no grupo B, que teve densidade 7162,4±1273,19 (p=0,013). A resistência da anastomose do grupo A teve a média 210±18,88 mmHg, significativamente maior que no grupo B, que atingiu o valor 157±29,55 mmHg (p=0,0024). CONCLUSÃO: Este estudo concluiu que o FCFbeta atuou melhorando a cicatrização e aumentando significativamente a resistência de anastomoses do esôfago realizadas em ratos.

Evaluation of the mechanism of vascular endothelial growth factor improvement of ischemic flap survival in rats

This study evaluated the effects of exogenous vascular endothelial growth factor (VEGF) on the regulation of cytokines in a rat dorsal ischemic skin flap model. Exogenous VEGF (1 microg/ml) was injected subdermally into the flaps of 12 rats before the flaps were sutured back in place. Another 12 rats with flaps received saline injections, as a control group. Biopsy specimens were obtained from the flaps treated with VEGF or saline solution, at positions 2.5, 5.5, and 8.5 cm from the distal edge of the flaps, at 12 hours (n = 6 for each group) and 24 hours (n = 6 for each group) after suturing of the flaps. Expression of cytokine, growth factor, and inducible nitric oxide synthase was measured. The results demonstrated that expression of tumor necrosis factor-alpha and nitric oxide synthase in the distal part of the VEGF-treated flaps was significantly decreased, compared with the control values, at 12 and 24 hours postoperatively. It was concluded that administration of exogenous VEGF could protect flaps from ischemia-reperfusion injury through the regulation of proinflammatory cytokines and the inhibition of cytotoxic nitric oxide production.