Efficacy of growth factors in the accelerated closure of interstices in explanted meshed human skin grafts

Adipokine concentrations in lipoaspirates may have a role in wound healing

OBJECTIVES

In addition to its use as a volume filler, fat grafting may have a potential role in wound healing based on the concentration of growth factors in the lipoaspirate. In this study, we compare the quantitative and qualitative concentration of the various growth factors and adipokines using the Shippert or the Coleman techniques to prepare the lipoaspirate.

METHODS

We measured leptin, adiponectin and the growth factors, i.e., acidic fibroblast growth factor (aFGF), basic FGF (bFGF), keratinocyte growth factor (KGF), bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF) by ELISA in solid and liquid fractions obtained with both techniques in human fat obtained with Coleman technique and Shippert technique.

RESULTS

All of these peptides, except BMP-2, were detected in relevant quantities in the solid fraction. The Coleman but not the Shippert technique resulted in statistically higher adiponectin concentrations in the solid tissue fraction. The other four growth factors occurred in significantly higher concentrations in the solid fractions compared to the liquid fractions, independent of the processing technique.

CONCLUSION

In summary, we demonstrated that KGF, aFGF, bFGF and VEGF, as well as leptin and adiponectin, are contained in fat suspensions obtained by liposuction and in the supernatant. Only the concentration of adiponectin was in the range reported to contribute to wound healing.

Re-epithelialization of adult skin wounds: Cellular mechanisms and therapeutic strategies

Cutaneous wound healing in adult mammals is a complex multi-step process involving overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodelling. Re-epithelialization describes the resurfacing of a wound with new epithelium. The cellular and molecular processes involved in the initiation, maintenance, and completion of epithelialization are essential for successful wound closure. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here, we focus on cellular mechanisms underlying keratinocyte migration and proliferation during epidermal closure. Inability to re-epithelialize is a clear indicator of chronic non-healing wounds, which fail to proceed through the normal phases of wound healing in an orderly and timely manner. This review summarizes the current knowledge regarding the management and treatment of acute and chronic wounds, with a focus on re-epithelialization, offering some insights into novel future therapies.

Use of Growth Factors and Other Cytokines for Treatment of Injuries During a Radiation Public Health Emergency

Due to the threat of a radiological or nuclear incident that could impact citizens, the U.S. Department of Health and Human Services tasked the National Institute of Allergy and Infectious Diseases (NIAID) with identifying and funding early- to mid-stage medical countermeasure (MCM) development to treat radiation-induced injuries. Given that the body's natural response to radiation exposure includes production of growth factors and cytokines, and that the only drugs approved by the U.S. Food and Drug Administration to treat acute radiation syndrome are growth factors targeting either the granulocyte (Neupogen^® or Neulasta^®) or granulocyte and macrophage (Leukine^®) hematopoietic cell lineages, there is interest in understanding the role that these factors play in responding to and/or ameliorating radiation damage. Furthermore, in an environment where resources are scarce, such as what might be expected during a radiation public health emergency, availability of growth factor or other treatments may be limited. For these reasons, the NIAID partnered with the Radiation Injury Treatment Network (RITN), whose membership includes medical centers with expertise in the management of bone marrow failure, to explore the use of growth factors and other cytokines as MCMs to mitigate/treat radiation injuries. A workshop was convened that included government, industry and academic subject matter experts, with presentations covering the anticipated concept of operations during a mass casualty incident including triage and treatment, growth factors under development for a radiation indication, and how the practice of medicine can inform other potential approaches, as well as considerations for administration of these products to diverse civilian populations. This report reviews the information presented, and provides an overview of the discussions from a guided breakout session.

Advancements in Regenerative Strategies Through the Continuum of Burn Care

Burns are caused by several mechanisms including flame, scald, chemical, electrical, and ionizing and non-ionizing radiation. Approximately half a million burn cases are registered annually, of which 40 thousand patients are hospitalized and receive definitive treatment. Burn care is very resource intensive as the treatment regimens and length of hospitalization are substantial. Burn wounds are classified based on depth as superficial (first degree), partial-thickness (second degree), or full-thickness (third degree), which determines the treatment necessary for successful healing. The goal of burn wound care is to fully restore the barrier function of the tissue as quickly as possible while minimizing infection, scarring, and contracture. The aim of this review is to highlight how tissue engineering and regenerative medicine strategies are being used to address the unique challenges of burn wound healing and define the current gaps in care for both partial- and full-thickness burn injuries. This review will present the current standard of care (SOC) and provide information on various treatment options that have been tested pre-clinically or are currently in clinical trials. Due to the complexity of burn wound healing compared to other skin injuries, burn specific treatment regimens must be developed. Recently, tissue engineering and regenerative medicine strategies have been developed to improve skin regeneration that can restore normal skin physiology and limit adverse outcomes, such as infection, delayed re-epithelialization, and scarring. Our emphasis will be centered on how current clinical and pre-clinical research of pharmacological agents, biomaterials, and cellular-based therapies can be applied throughout the continuum of burn care by targeting the stages of wound healing: hemostasis, inflammation, cell proliferation, and matrix remodeling.

α11 integrin stimulates myofibroblast differentiation in diabetic cardiomyopathy

AIMS

Diabetic cardiomyopathy is characterized by the production of a disorganized fibrotic matrix in the absence of coronary atherosclerosis and hypertension. We examined whether adhesion of cardiac fibroblasts to glycated collagens mediates the differentiation of pro-fibrotic myofibroblasts, which may contribute to cardiac fibrosis.

METHODS AND RESULTS

By microarray, we found that methylglyoxal-treated collagen selectively enhanced α11 integrin expression in human cardiac fibroblasts, while levels of other collagen-binding integrins (α1, α2, and α10) were unchanged. Similar increases in α11 integrin mRNA and protein expression were observed in cardiac fibroblasts from streptozotocin (STZ)-treated Sprague-Dawley rats. In human cardiac fibroblasts plated on methyglyoxal-treated collagen and in cardiac fibroblasts from diabetic rats, transforming growth factor (TGF)-β2 but not TGF-β1 or TGF-β3 was increased compared with controls. Knock-down of α11 integrin and TGF-β receptors with small-interfering RNA blocked the increased expression of TGF-β2, α-smooth muscle actin (α-SMA), and α11 integrin that were induced in cells plated on methylglyoxal-treated collagen. Further, inhibition of Smad3 signalling blocked methylglyoxal-collagen up-regulation of α11 integrin and α-SMA expression. Rats with STZ-induced diabetes exhibited increased phosphorylation of Smad3 in cardiac tissues compared with control rats.

CONCLUSION

Interactions between α11 integrins and the Smad-dependent TGF-β2 signalling may contribute to the formation of pro-fibrotic myofibroblasts and the development of a fibrotic interstitium in diabetic cardiomyopathy.

Sugar-coating wound repair: a review of FGF-10 and dermatan sulfate in wound healing and their potential application in burn wounds

Thousands of patients suffer from burn injuries each year, yet few therapies have been developed to accelerate the wound healing process. Most fibroblast growth factors (FGFs) have been extensively evaluated but only a few have been found to participate in the wound healing process. In particular, FGF-10 is robustly increased in the wound microenvironment after injury and has demonstrated some ability to promote wound healing in vitro and in vivo. Glycosaminoglycans are linear carbohydrates that participate in wound repair by influencing cytokine/growth factor localization and interaction with cognate receptors. Dermatan sulfate (DS) is the most abundant glycosaminoglycan in human wound fluid and has been postulated to be directly involved in the healing process. Recently, the combination of FGF-10 and DS demonstrated the potential to accelerate wound healing via increased keratinocyte proliferation and migration. Based on these preliminary studies, DS may serve as a cofactor for FGF-10, and together they are likely to expedite the healing process by stimulating keratinocyte activity. As a specific subtype of wounds, the overall healing process of burn injuries does not significantly differ from other types of wounds, where optimal repair results in matrix regeneration and complete reepithelialization. At present, standard burn treatment primarily involves topical application of antimicrobial agents, while no routine therapies target acceleration of reepithelialization, the key to wound closure. Thus, this novel therapeutic combination could be used in conjunction with some of the current therapies, but it would have the unique ability to initiate wound healing by stimulating keratinocyte epithelialization.

A phage-targeting strategy for the design of spatiotemporal drug delivery from grafted matrices

Background

The natural response to injury is dynamic and normally consists of complex temporal and spatial cellular changes in gene expression, which, when acting in synchrony, result in patent tissue repair and, in some instances, regeneration. However, current therapeutic regiments are static and most rely on matrices, gels and engineered skin tissue. Accordingly, there is a need to design next-generation grafting materials to enable biotherapeutic spatiotemporal targeting from clinically approved matrices. To this end, rather then focus on developing completely new grafting materials, we investigated whether phage display could be deployed onto clinically approved synthetic grafts to identify peptide motifs capable of linking pharmaceutical drugs with differential affinities and eventually, control drug delivery from matrices over both space and time.

Methods

To test this hypothesis, we biopanned combinatorial peptide libraries onto different formulations of a wound-healing matrix (Integra^®) and eluted the bound peptides with 1) high salt, 2) collagen and glycosaminoglycan or 3) low pH. After three to six rounds of biopanning, phage recovery and phage amplification of the bound particles, any phage that had acquired a capacity to bind the matrix was sequenced.

Results

In this first report, we identify distinct classes of matrix-binding peptides which elute differently from the screened matrix and demonstrate that they can be applied in a spatially relevant manner.

Conclusions

We suggest that further applications of these combinatorial techniques to wound-healing matrices may offer a new way to improve the performance of clinically approved matrices so as to introduce temporal and spatial control over drug delivery.

Effect of sustained-release PDGF and TGF-beta on cyclophosphamide-induced impaired wound healing

BACKGROUND

Proper wound healing is pivotal to successful surgical outcomes. Previous studies have shown that growth factors can be used to enhance tissue repair under impaired healing conditions. However, because of limited delivery methods, the growth factors in these studies were delivered either topically or as a single local administration.

METHODS

Sixty Sprague-Dawley rats were divided equally into five groups and served as untreated normal controls or were implanted subcutaneously with a novel sustained-release drug delivery system through a dorsal incisional wound. This system delivered either transforming growth factor (TGF)-beta alone, platelet-derived growth factor (PDGF) alone, or TGF-beta and PDGF in combination, or served as unloaded sham controls. Wound healing was impaired in all treated rats by the administration of cyclophosphamide on days 1, 3, and 5. Wound tensile breaking strength was determined on days 4, 7, and 14.

RESULTS

Sustained release of either TGF-beta or PDGF alone not only failed to improve the healing of cyclophosphamide-induced impaired wound healing but resulted in a paradoxical decrease in wound tensile breaking strength by day 7. However, the combined delivery of both TGF-beta and PDGF improved wound healing and significantly increased wound tensile breaking strength by day 7.

CONCLUSIONS

Sustained-release delivery of TGF-beta and PDGF in combination, but not separately, by a subcutaneously implanted drug delivery system significantly improves cyclophosphamide-induced impaired wound healing in rats.

Down-regulation of transforming growth factor beta-2 expression is associated with the reduction of cyclosporin induced gingival overgrowth in rats treated with roxithromycin: an experimental study

Background

Gingival overgrowth (GO) is a common side effect of the chronic use of cyclosporine (CsA), an immunosuppressant widely used to prevent rejection in transplant patients. Recent studies have reported elevated levels of specific cytokines in gingival overgrowth tissue, particularly TGF-beta, suggesting that this growth factor plays a role in the accumulation of extracellular matrix materials. The effectiveness of azithromycin, a macrolide antibiotic, in the regression of this undesirable side effect has also been demonstrated.

Methods

In this study, we created an experimental model for assessing the therapeutic effect of roxithromycin in GO and the expression of transforming growth factor beta (TGF-beta2) through immunohistochemistry. We used four groups of rats totaling 32 individuals. GO was induced during five weeks and drug treatment was given on the 6th week as follows: group 1 received saline; group 2 received CsA and was treated with saline on the 6th week; group 3 received CsA and, on the 6th week, ampicilin; and group 4 received CsA during 5 weeks and, on the 6th week, was treated with roxithromycin.

Results

The results demonstrated that roxithromycin treatment was effective in reducing cyclosporine-induced GO in rats. Both epithelial and connective tissue showed a decrease in thickness and a significant reduction in TGF-beta2 expression, with a lower number of fibroblasts, reduction in fibrotic areas and decrease in inflammatory infiltrate.

Conclusion

The present data suggest that the down-regulation of TGF-beta2 expression may be an important mechanism of action by which roxithromycin inhibits GO.

Rigorous Vibrio vulnificus soft tissue infection of the lower leg in a renal transplant patient managed by vacuum therapy and autologous growth factors

BACKGROUND

Vibrio vulnificus is a gram-negative marine bacterium that grows well in coastal waters. It is an opportunistic pathogen that can cause serious life-threatening infections in patients with certain health conditions. Vibrio-induced wound infections in immunosuppressed patients are difficult to treat because the healing process may be significantly delayed. Reconstructive surgery may not be successful in early treatment as skin grafts are likely to fail, and there may be increased morbidity of donor sites of grafts or flaps.

OBJECTIVE

Herein a case of septicemia and wound necrosis owing to V. vulnificus wound infection in a renal transplant patient is reported.

METHOD

To conservatively yet adequately débride the wound bed, stimulate angiogenesis, and accelerate granulation, vacuum-assisted closure was employed. Granulation was further enhanced by autologous platelet concentrate spray, which has also been reported to increase the epithelialization rate.

RESULT

Complete epithelialization of the wound was achieved 4 weeks after completion of treatment.

CONCLUSION

Noninvasive advanced modalities may be employed to successfully treat infectious soft tissue deficits in immunocompromised patients.

Construction and characterization of a high activity mutant of human keratinocyte growth factor-2

Keratinocyte growth factor-2 (KGF-2) plays an important role in vertebrate limb development, lung branching morphogenesis, regeneration and reconstruction of the epidermis. Previous studies have used the wild type factor. Here, we have constructed a double-site mutant of human KGF-2, named STEA. STEA possesses higher receptor binding affinity and promotes better proliferation activity on rat tracheal epithelium (RTE) cells than recombinant human KGF-2. These results suggest that the simultaneous mutation of Ser115 to Thr and Glu117 to Ala improves the biological activity of KGF-2.

Large-scale production of biologically active human keratinocyte growth factor-2

A rapid and efficient expression and purification system has been developed for large-scale production of biologically active recombinant human keratinocyte growth factor-2 (rhKGF-2). The gene encoding human KGF-2 was cloned into the expression vector pET3c and transformed into Escherichia coli BL21(DE3)/pLys S. Under optimal conditions in a 30-l fermentor, the average bacterial yield and the average expression level of rhKGF-2 of three batches were up to 732 g and 32%, respectively. The recombinant protein was purified by cation exchange and heparin-affinity chromatography. One hundred and sixty five milligrams of pure rhKGF-2 was achieved per liter culture. A preliminary biochemical characterization of purified rhKGF-2 was performed by Western blotting and mitogenic activity analysis, and the results demonstrated that purified rhKGF-2 could react with anti-human KGF-2 antibody and stimulate the proliferation of HaCat cells.

Expression, purification, and characterization of recombinant human keratinocyte growth factor-2 in Pichia pastoris

Keratinocyte growth factor-2 (KGF-2) is a member of the fibroblast growth factor family. The full-length human KGF-2 coding sequence, gained by synthesizing, was cloned into the pPICZalphaA vector in frame with the yeast alpha-factor secretion signal under the transcriptional control of the AOX promoter and integrated into Pichia pastoris strain GS115. In shake-flask culture induced with methanol, the rhKGF-2 content was about 17.5% of the total secreted proteins. Under the optimal conditions, stable production of rhKGF-2 around 1.0g/l was achieved. The recombinant protein was purified by heparin affinity chromatography. A preliminary biochemical characterization of purified rhKGF-2 was performed both by Western blot analysis and biological activity analysis, and the result demonstrated that the recombinant KGF-2 was expressed successfully.

Fibroblasts from chronic wounds show altered TGF-beta-signaling and decreased TGF-beta Type II receptor expression

Chronic wounds are characterized by failure to heal in a defined time frame. However, the pathogenic steps leading from the etiological factors to failure to heal are unknown. Recently, increasing evidence suggests that resident cells in chronic wounds display a number of critical abnormalities, including senescence and unresponsiveness to the stimulatory action of transforming growth factor-beta1 (TGF-beta1). In this study, we have determined some of the mechanisms that might be responsible for unresponsiveness to TGF-beta1. Using Northern analysis and affinity labeling, we show that venous ulcer fibroblasts have decreased TGF-beta Type II receptor expression. This finding is not the result of genetic mutation, as shown by experiments with Type II receptor satellite instability. Decreased Type II receptor expression was accompanied by failure of ulcer fibroblasts to phosphorylate Smad 2, Smad 3, and p42/44 mitogen activating protein kinase (MAPK), and was associated with a slower proliferative rate in response to TGF-beta1. We conclude that venous ulcer fibroblasts show decreased Type II receptor expression and display abnormalities in the downstream signaling pathway involving MAPK and the early Smad pathway. These findings suggest ways to address and treat the abnormal cellular phenotype of cells in chronic wounds.

Cytokine manipulation of the wound

Most individuals expect that healing is an inevitable outcome; wound healing is taken for granted. Although wound healing is perceived as inevitable, it can be fraught with problems and altered at many points. In the past, optimization of wound healing focused on minimizing contamination, accurate tissue approximation, and providing protection. With the advent of recombinant technology, optimization can now include manipulation of the molecular and cellular wound environment. Although the exact manipulative scheme has not yet evolved, it is clear from the multiple attempts reported in this article that understanding and progress is being made.

The rate of re-epithelialization across meshed skin grafts is increased with exposure to silver

The objective in this study was to determine whether exposure to pure silver increases the rate of re-epithelialization across a partial thickness wound. A meshed skin graft, placed on an excised burn wound was used as a healing model.

METHODS

The rate of meshed skin graft epithelial closure on an exposed burn using a moist healing environment was shown. A moistened silver delivery system (Acticoat) was compared with a standard xeroform and eight ply gauze dressing continually moistened with a 0.01% neomycin and polymyxin solution (NP). Twenty burn patients with deep burns of over 15% of TBS were excised and grafted with 2:1 meshed grafts. One graft area was treated with the antibiotic solution and another with the silver delivery. The meshed graft was performed within 3 days of injury.

RESULTS

No infections were noted and quantitative swab cultures gave less than 10(2) bacteria in all cases at wound closure. At day 7, re-epithelialization was complete with silver and 55% closed with NP solution. Wound closure was complete in the NP solution group at day 10. Silver increased re-epithelialization rate by over 40%, a significant increase. Graft take was over 95% in both groups.

CONCLUSION

Silver released in a moist wound surface environment significantly increases the rate of re-epithelialization compared to a standard antibiotic solution.

Skin resurfacing for the burned patient

It has been estimated that 2 million people per year have burns requiring medical attention in the United States. The available and expert clinicians in dedicated burn centers around the country have cared successfully for these patients and given them a second chance at a functional life. It still behooves current-day plastic surgeons to be knowledgeable and adept in their care, not only because they may be called upon at times to manage some of the smaller acute burns, but also because many of the general principles of burn reconstruction and wound management are relevant to other areas of general plastic surgery. Acute burns should be dealt with like any other major trauma with the ABCs of aggressive resuscitation and airway management. Like any other wound, debridement and nutrition are important (i.e., early escharectomy of the burn wound and enteral nutrition during the hypermetabolic state). Early coverage of the open wound is essential to limit bacterial colonization and prevent infection and to reduce fluid and electrolyte and heat loss. If autografts are not available immediately, temporary coverage with one of the above-mentioned barrier materials should be used. Still, autografts, when available, should be the burn surgeon's first choice. Donor sites may be reharvested to provide more autograft than was anticipated with large-percentage TBSA burns. Physicians should keep in mind the advantages (and disadvantages) of using the scalp and back. As far as research and technological advances in the area of plastic surgery, burn surgery may be the most progressive, with the evolution of biologic tissue-engineered skin substitutes and the research of growth factors in healing. Further improvements in tissue engineering and technology should result in even more effective skin substitutes and hence better functional and aesthetic outcomes with economic efficiency in large burns.

Simultaneous delivery of an active protein and neutralizing antibody: creation of separated regions of biological activity

Spatial control over the biological activity of nerve growth factor (NGF) via a novel type of controlled-release device was demonstrated in an in vitro system. Two-layer polymer matrices that simultaneously released NGF and a neutralizing antibody (anti-NGF) from opposite faces were placed in PC12 cell-populated collagen gels. Biological activity in the gels was assessed over the course of 10 days by direct observation of the cells, which extend neuronal processes in the presence of NGF in a dose-dependent manner. The concentrations of both proteins in the gels were determined by ELISA as a function of distance from the polymer matrices at various time points. A boundary in biological activity was established within a few days of the initiation of the cultures; this boundary persisted and became more pronounced throughout the duration of the experiment. ELISA analysis revealed regions of high concentration of both NGF and anti-NGF on their respective sides of the polymer matrix early in the experiment. The theoretical amount of active NGF in the gel sections was calculated on the basis of these ELISA results; the concentration of active NGF in the region adjacent to the polymer correlated with the observed degree of biological response. These experiments suggest that spatial control over the biological activity of a potent agent can be obtained by an appropriately designed controlled-release device.