Acidic fibroblast growth factor: evaluation of topical formulations in a diabetic mouse wound healing model

Encapsulation of berberine decorated ZnO nano-colloids into injectable hydrogel using for diabetic wound healing

Chronic wound healing in diabetic patients had been considered a major clinical challenge, so there was an urgent need to establish more effective treatment methods. In this study, we prepared berberine-modified ZnO nano-colloids hydrogel (ZnO-Ber/H) and evaluated its wound healing performance in a diabetic rat. The prepared ZnO-Ber/H had excellent moisturizing, anti-inflammatory and anti-oxidative stress abilities. In vitro, ZnO-Ber/H could effectively up-regulate antioxidant stress factors (Nrf2, HO-1, NQO1) by 4.65-fold, 2.49-fold, 2.56-fold, respectively. In vivo experiments have shown that ZnO-Ber/H could effectively improve the wound healing rate (92.9%) after 15 days of treatment. Meanwhile, the ability of anti-oxidative stress had also been verified in vivo. ZnO-Ber/H down-regulated inflammatory factor (TNF-α, IL-1β, and IL-6) by 72.8%, 55% and 71% respectively, up-regulated vascular related factors VEGF and CD31 by 3.9-fold and 3.2-fold by Western blot. At the same time, ZnO-Ber/H could promote the expression of EGFR and FGFR, thereby affecting the generation of new epithelial tissue. Based on extensive characterization and biological evaluation, ZnO-Ber/H was expected to be a potential candidate for promoting diabetic wound healing.

Systematic review and meta-analysis of mouse models of diabetes-associated ulcers

Mouse models are frequently used to study diabetes-associated ulcers, however, whether these models accurately simulate impaired wound healing has not been thoroughly investigated. This systematic review aimed to determine whether wound healing is impaired in mouse models of diabetes and assess the quality of the past research. A systematic literature search was performed of publicly available databases to identify original articles examining wound healing in mouse models of diabetes. A meta-analysis was performed to examine the effect of diabetes on wound healing rate using random effect models. A meta-regression was performed to examine the effect of diabetes duration on wound healing impairment. The quality of the included studies was also assessed using two newly developed tools. 77 studies using eight different models of diabetes within 678 non-diabetic and 720 diabetic mice were included. Meta-analysis showed that wound healing was impaired in all eight models. Meta-regression suggested that longer duration of diabetes prior to wound induction was correlated with greater degree of wound healing impairment. Pairwise comparisons suggested that non-obese diabetic mice exhibited more severe wound healing impairment compared with db/db mice, streptozotocin-induced diabetic mice or high-fat fed mice at an intermediate stage of wound healing (p<0.01). Quality assessment suggested that the prior research frequently lacked incorporation of key clinically relevant characteristics. This systematic review suggested that impaired wound healing can be simulated in many different mouse models of diabetes but these require further refinement to become more clinically relevant.

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.

Insulin Mucoadhesive Liposomal Gel for Wound Healing: a Formulation with Sustained Release and Extended Stability Using Quality by Design Approach

The present study deals with the formulation of topical insulin for wound healing with extended stability and sustained release, by applying quality by design concepts. Insulin has been promoted as a promising therapeutic wound healing agent. Topical formulation of insulin faced major problems, as it cannot be delivered safely to the wound with a controlled rate. Formulation of insulin-loaded vesicles in optimized bio-adhesive hydrogels has been explored to ensure a safe delivery of insulin to wounds in a controlled manner. Quality by design (QbD) was applied to study the effect of several critical process parameters on the critical quality attributes. Ishikawa diagram was used to identify the highest risk factors, which were screened by a fractional factorial design and augmented by Box-Behnken design. The optimized formula was incorporated into a mucoadhesive gel, which was further subjected to stability and clinical studies. An optimized formula was obtained with a particle size of 257.751 nm, zeta potential - 20.548 mv, 87.379% entrapment efficiency, and a release rate of 91.521 μg/cm²/h. The results showed that liposomal insulin remained stable for 6 months in aqueous dispersion state at 4°C. Moreover, the release was sustained up to 24 h. The clinical study showed an improvement in the wound healing rate, 16 times, as the control group, with magnificent reduction in the erythema of the ulcer and no signs of hypoglycemia. Insulin-loaded liposomal chitosan gel showed a promising drug delivery system with high stability and sustained release.

Fine-Sampled Photographic Quantitation of Dermal Wound Healing Senescence in Aged BALB/cByJ Mice and Therapeutic Intervention with Fibroblast Growth Factor-1

Objective: To determine quantitative parameters of dermal wound healing senescence in aged BALB/cByJ mice (an important animal model of aging) and to evaluate the potential for therapeutic intervention by fibroblast growth factor-1 (FGF-1). Approach: Utilize a novel noninvasive fine-sampled photographic methodology to quantify wound healing parameters for healing phases from wounding through to wound closure. Results: Parameters associated with key healing phases were quantified and compared between nonaged and aged cohorts of both genders. The results identify a sexual dimorphism in dermal wound healing, with nonaged females exhibiting a greater overall healing efficiency than males. This enhanced healing in females, however, senesces with age such that healing parameters for aged males and females are statistically indistinguishable. Topical application of FGF-1 was identified as an effective therapeutic intervention to treat dermal healing senescence in aged females. Innovation: The FGF intervention is being analyzed using a new recently published model. This approach significantly increases the amount of preclinical animal data obtainable in wound healing studies, minimizes cohort number compared with (lethal) histological studies, and permits a direct statistical comparison between different healing studies. Conclusion: Quantitative parameters of dermal wound healing, obtained from noninvasive fine-sampled photographic data, identify topical FGF-1 as an effective therapeutic to treat the senescence of dermal healing present in aged female BALB/cByJ mice.

Accelerated healing in NONcNZO10/LtJ type 2 diabetic mice by FGF-1

The development of novel therapies to treat chronic diabetic ulcers depends upon appropriate animal models for early stage investigation. The NONcNZO10/LtJ mouse is a new polygenic strain developed to more realistically model human metabolic syndrome and obesity-induced type 2 diabetes; however, detailed wound healing properties have not been reported. Herein, we describe a quantitative wound healing study in the NONcNZO10/LtJ mouse using a splinted excisional wound. The rate of wound healing is compared to various controls, and is also quantified in response to topical administration of normal and mutant fibroblast growth factor-1 (FGF-1). Quantitation of reepithelialization shows that the diabetic condition in the NONcNZO10/LtJ mouse is concomitant with a decreased rate of dermal healing. Furthermore, topical administration of a FGF-1/heparin formulation effectively accelerates reepithelialization. A similar acceleration can also be achieved by a stabilized mutant form of FGF-1 formulated in the absence of heparin. Such accelerated rates of healing are not associated with any abnormal histology in the healed wounds. The results identify the NONcNZO10/LtJ mouse as a useful model of impaired wound healing in type 2 diabetes, and further, identify engineered forms of FGF-1 as a potential “second-generation” therapeutic to promote diabetic dermal wound healing.

Fibroblast growth factors, old kids on the new block

The fibroblast growth factors (FGFs) are a family of cell intrinsic regulatory peptides that control a broad spectrum of cellular activities. The family includes canonic FGFs that elicit their activities by activating the FGF receptor (FGFR) tyrosine kinase and non-canonic members that elicit their activities intracellularly and via FGFR-independent mechanisms. The FGF signaling axis is highly complex due to the existence of multiple isoforms of both ligands and receptors, as well as cofactors that include the chemically heterogeneous heparan sulfate (HS) cofactors, and in the case of endocrine FGFs, the Klotho coreceptors. Resident FGF signaling controls embryonic development, maintains tissue homeostasis, promotes wound healing and tissue regeneration, and regulates functions of multiple organs. However, ectopic or aberrant FGF signaling is a culprit for various diseases, including congenital birth defects, metabolic disorder, and cancer. The molecular mechanisms by which the specificity of FGF signaling is achieved remain incompletely understood. Since its application as a druggable target has been gradually recognized by pharmaceutical companies and translational researchers, understanding the determinants of FGF signaling specificity has become even more important in order to get into the position to selectively suppress a particular pathway without affecting others to minimize side effects.

TAT-Mediated Acidic Fibroblast Growth Factor Delivery to the Dermis Improves Wound Healing of Deep Skin Tissue in Rat

BACKGROUND

The definition of deep tissue injury was derived from multiple clinical cases as "A purple or maroon localized area of discolored intact skin or blood-filled blister due to damage of underlying soft tissue from pressure and/or shear". Acidic fibroblast growth factor (aFGF) significantly improves wound healing under diabetic conditions. However, to date, the therapeutic application of aFGF has been limited, due to its low delivery efficiency and short half-life.

METHODOLOGY/PRINCIPAL FINDINGS

Using an animal model of magnet-induced pressure ulcers, transactivator of transcription protein (TAT)-aFGF was evaluated for transdermal delivery and wound healing. Immunohistochemistry and Western blotting were also performed to determine the expression of transforming growth factor (TGF)-β1, α-smooth muscle actin (α-SMA), CD68, proliferating cell nuclear antigen (PCNA) and TGF-β-receptor II (TGF- βRII) in cultured human dermal fibroblasts. We found that that mice treated with TAT-aFGF had higher accumulation of aFGF in both dermis and subcutaneous tissues compared with mice treated with aFGF alone. In the remodeling phase, TAT-aFGF treatment decreased the expression of α-SMA to normal levels, thereby facilitating normal wound healing processes and abrogating hypertrophic scarring. In human dermal fibroblasts, TAT-aFGF reversed the suppressive effect of TNF-α on α-SMA expression and restored TGF-βRII and TGF-β1 expression.

CONCLUSIONS/SIGNIFICANCE

Our results demonstrate that TAT-aFGF has a favorable therapeutic effect on the healing of subcutaneous deep tissue injury.

The prevention of diabetic cardiomyopathy by non-mitogenic acidic fibroblast growth factor is probably mediated by the suppression of oxidative stress and damage

BACKGROUND

Emerging evidence showed the beneficial effect of acidic fibroblast growth factor (aFGF) on heart diseases. The present study investigated whether non-mitogenic aFGF (nm-aFGF) can prevent diabetic cardiomyopathy and the underlying mechanisms, if any.

METHODOLOGY/PRINCIPAL FINDINGS

Type 1 diabetes was induced in mice by multiple intraperitoneal injections of low-dose streptozotocin. Hyperglycemic and age-matched control mice were treated with or without nm-aFGF at 10 µg/kg daily for 1 and 6 months. Blood pressure and cardiac function were assessed. Cardiac H9c2 cell, human microvascular endothelial cells, and rat cardiomyocytes were exposed to high glucose (25 mM) for mimicking an in vitro diabetic condition for mechanistic studies. Oxidative stress, DNA damage, cardiac hypertrophy and fibrosis were assessed by real-time qPCR, immunofluorescent staining, Western blotting, and pathological examination. Nm-aFGF significantly prevented diabetes-induced hypertension and cardiac dysfunction at 6 months. Mechanistic studies demonstrated that nm-aFGF showed the similar preventive effect as the native aFGF on high glucose-induced oxidative stress (increase generation of reactive oxygen species) and damage (cellular DNA oxidation), cell hypertrophy, and fibrotic response (increased mRNA expression of fibronectin) in three kinds of cells. These in vitro findings were recaptured by examining the heart of the diabetic mice with and without nm-aFGF.

CONCLUSIONS

These results suggest that nm-aFGF can prevent diabetic cardiomyopathy, probably through attenuation of cardiac oxidative stress, hypertrophy, and fibrosis.

Pharmacokinetic properties of 2nd-generation fibroblast growth factor-1 mutants for therapeutic application

Fibroblast growth factor-1 (FGF-1) is an angiogenic factor with therapeutic potential for the treatment of ischemic disease. FGF-1 has low intrinsic thermostability and is characteristically formulated with heparin as a stabilizing agent. Heparin, however, adds a number of undesirable properties that negatively impact safety and cost. Mutations that increase the thermostability of FGF-1 may obviate the need for heparin in formulation and may prove to be useful “2nd-generation” forms for therapeutic use. We report a pharmacokinetic (PK) study in rabbits of human FGF-1 in the presence and absence of heparin, as well as three mutant forms having differential effects upon thermostability, buried reactive thiols, and heparin affinity. The results support the hypothesis that heparan sulfate proteoglycan (HSPG) in the vasculature of liver, kidney and spleen serves as the principle peripheral compartment in the distribution kinetics. The addition of heparin to FGF-1 is shown to increase endocrine-like properties of distribution. Mutant forms of FGF-1 that enhance thermostability or eliminate buried reactive thiols demonstrate a shorter distribution half-life, a longer elimination half-life, and a longer mean residence time (MRT) in comparison to wild-type FGF-1. The results show how such mutations can produce useful 2nd-generation forms with tailored PK profiles for specific therapeutic application.

Royal jelly enhances migration of human dermal fibroblasts and alters the levels of cholesterol and sphinganine in an in vitro wound healing model

Oral administration of royal jelly (RJ) promotes wound healing in diabetic mice. Concerns have arisen regarding the efficacy of RJ on the wound healing process of normal skin cells. In this study, a wound was created by scratching normal human dermal fibroblasts, one of the major cells involved in the wound healing process. The area was promptly treated with RJ at varying concentrations of 0.1, 1.0, or 5 mg/ml for up to 48 hrs and migration was analyzed by evaluating closure of the wound margins. Furthermore, altered levels of lipids, which were recently reported to participate in the wound healing process, were analyzed by HPTLC and HPLC. Migration of fibroblasts peaked at 24 hrs after wounding. RJ treatment significantly accelerated the migration of fibroblasts in a dose-dependent manner at 8 hrs. Although RJ also accelerated the migration of fibroblasts at both 20 hrs and 24 hrs after wounding, the efficacy was less potent than at 8 hrs. Among various lipid classes within fibroblasts, the level of cholesterol was significantly decreased at 8 hrs following administration of both 0.1 ug/ml and 5 mg/ml RJ. Despite a dose-dependent increase in sphinganines, the levels of sphingosines, ceramides, and glucosylceramides were not altered with any concentration of RJ. We demonstrated that RJ enhances the migration of fibroblasts and alters the levels of various lipids involved in the wound healing process.

Characteristics of rhVEGF release from topical hydrogel formulations

PURPOSE

To study recombinant human vascular endothelial growth factor (rhVEGF), the release characteristics from topical gel formulations, and its interaction with the gelling agents.

METHODS

The release kinetics were followed by quantifying rhVEGF that diffused into the receptor chamber of Franz cells. Analytical ultracentrifuge (AUC) was used to characterize the sedimentation velocity of rhVEGF experienced in the gel. The interactions were characterized by isothermal calorimetry (ITC), and rhVEGF conformation was assessed by circular dichroism (CD).

RESULTS

The fraction of protein released was linear with the square root of time. The release rate constants did not show significant change within a wide range of bulk viscosities created by different concentrations of hydroxypropyl methylcellulose (HPMC) or MC gels. Sedimentation velocity determined by AUC generated comparable sedimentation coefficients of protein in these gels. AUC and ITC revealed no significant interaction between rhVEGF and HPMC and some change on secondary structure of the protein by Far UV CD, which was not the case with carboxymethyl cellulose (CMC).

CONCLUSIONS

Microviscosity, not bulk viscosity, was the key factor for the release of rhVEGF from cellulosic gels such as HPMC. Interaction between rhVEGF and CMC resulted in slower, and reduced amount of, release from the gel.

Accelerated wound healing through the incorporation of basic fibroblast growth factor-impregnated gelatin microspheres into artificial dermis using a pressure-induced decubitus ulcer model in genetically diabetic mice

The objective of this study was to evaluate the effect of incorporating basic fibroblast growth factor (bFGF)-impregnated gelatin microspheres into an artificial dermis on impaired wound healing using a pressure-induced decubitus ulcer model in genetically diabetic mice. Daily 10 h prolonged pressure at 500 g/cm2 was loaded for 2 consecutive days over the femoral trochanter tertius of mice to produce ischemic necrosis. Five days after completion of the pressure load, the necrotic tissues were resected. Then, an artificial dermis incorporating bFGF-impregnated gelatin microspheres or bFGF in solution was implanted into the wound (n = 5). Mice were sacrificed at 5, 7, and 10 days after implantation, and a full-thickness biopsy was taken and stained with hematoxylin and eosin for histological analysis. All experimental animals were infected because diabetic mice have little tolerance for infection. Seven days after implantation, the incorporation of bFGF into the artificial dermis reduced infection and accelerated fibroblast proliferation and capillary formation. However, the accelerated effects were more significant with the incorporation of bFGF-impregnated gelatin microspheres than with free bFGF. We conclude that the incorporation of bFGF-impregnated gelatin microspheres into an artificial dermis induced tissue regeneration in an artificial dermis in an impaired wound healing model.

Adeno-associated viral vector-mediated human vascular endothelial growth factor gene transfer stimulates angiogenesis and wound healing in the genetically diabetic mouse

AIMS/HYPOTHESIS

We studied the gene therapy efficacy of diabetes-associated wound healing disorder with an adeno-associated virus (AAV) vector expressing the 165-amino acid isoform of human vascular endothelial growth factor-A (VEGF-A) by using an incisional skin-wound model produced on the back of female diabetic C57BL/KsJ db+/db+ mice and their normal littermates ( db+/+m).

METHODS

Animals were randomized to receive intradermally into the wound edges either rAAV-LacZ (a control gene), or rAAV-VEGF165. Animals were killed on different days (7 and 14 days after skin injury) and wounded skin tissues were used for gene marker studies, histological evaluation and immunohistochemistry, and wound breaking strength analysis. Furthermore we studied the VEGF mature protein in the wounds.

RESULTS

We found that AAV vectors are highly efficient for gene transfer to the mouse skin, displaying an exquisite tropism for the panniculus carnosus by using the beta-galactosidase activity assay. We confirmed the increased expression of the angiogenic factor at day 7 by measuring the wound content of the mature protein. Delivery of VEGF165 to incisional skin wounds of diabetic mice resulted in a remarkable induction of new vessel formation with consequent improvement in the wound healing process. The rAAV-VEGF165 gene improved wound healing in diabetic mice through the stimulation of angiogenesis, reepithelization, synthesis and maturation of extracellular matrix. Moreover the recombinant AAV encoding the human VEGF165 increased the breaking strength of the wound and enhanced the wound content of VEGF.

CONCLUSION/INTERPRETATION

Our study suggests that VEGF gene transfer might represent a new approach to treat wound healing disorders associated with diabetes.

The role of oxidised regenerated cellulose/collagen in wound repair: effects in vitro on fibroblast biology and in vivo in a model of compromised healing

Irrespective of underlying chronic wound pathology, delayed wound healing is normally characterised by impaired new tissue formation at the site of injury. It is thought that this impairment reflects both a reduced capacity to synthesize new tissue and the antagonistic activities of high levels of proteinases within the chronic wound environment. Historically, wound dressings have largely been passive devices that offer the wound interim barrier function and establish a moist healing environment. A new generation of devices, designed to interact with the wound and promote new tissue formation, is currently being developed and tested. This study considers one such device, oxidised regenerated cellulose (ORC) /collagen, in terms of its ability to promote fibroblast migration and proliferation in vitro and to accelerate wound repair in the diabetic mouse, a model of delayed wound healing. ORC/collagen was found to promote both human dermal fibroblasts proliferation and cell migration. In vivo studies considered the closure and histological characteristics of diabetic wounds treated with ORC/collagen compared to those of wounds given standard treatment on both diabetic and non-diabetic mice. ORC/collagen was found to significantly accelerate diabetic wound closure and result in a measurable improvement in the histological appearance of wound tissues. As the diabetic mouse is a recognised model of impaired healing, which may share some characteristics of human chronic wounds, the results of this in vivo study, taken together with those relating the positive effects of ORC/collagen in vitro, may predict the beneficial use of this device in the clinical setting.

Success and limitations of a naked plasmid transfection protocol for keratinocyte growth factor-1 to enhance cutaneous wound healing

Our group and others have previously reported enhancement of cutaneous wound healing following the transfection of tissue with plasmid vectors expressing the DNA for growth factors. In these experiments, growth factor treated animals were usually compared to animals treated with control plasmid vector. To achieve consistent transfection, high DNA plasmid load and repeated penetrations of the wound by needle or gene gun were required. In the current experiments, we assessed the effect of the plasmid load and repeated tissue penetrations on wound healing of excisional wounds in diabetic C57 mice. Animals received 5 mm excisional wounds, and were assigned to the following groups, no treatment, phosphate buffered saline solution injections, and plasmid vector injection with and without the keratinocyte growth factor-1 gene. Intradermal injections of 100 microg plasmid were given adjacent to the wounds at days 1-5, 7 and 11. At day 9, wound closure was more advanced in keratinocyte growth factor-1 treated animals compared to those treated with control plasmid. But a detrimental effect of the DNA plasmid injection was evident from a comparison of the DNA control group versus the non-injected group. Therefore, the challenge for developing an effective system for the enhancement of wound healing lies in improving transfection efficiency.

Raxofelast, a hydrophilic vitamin E-like antioxidant, stimulates wound healing in genetically diabetic mice

BACKGROUND

Impaired wound healing is a well-documented phenomenon in experimental and clinical diabetes. Emerging evidence favors the involvement of free radicals in the pathogenesis of diabetes-related healing deficit. This study assessed the effect of systemic administration of raxofelast, a protective membrane antioxidant agent, on wound healing by using healing-impaired (db/db) mice.

METHODS

The wound healing effect of raxofelast was investigated by using an incisional skin-wound model produced on the back of female diabetic C57BL/KsJ db+/db+ mice and their healthy littermates (db+/+m). Animals were then randomized to the following treatment: raxofelast (15 mg/kg/d intraperitoneally) or its vehicle (dimethyl sulfoxide/sodium chloride 0.9%, 1:1, vol/vol). The animals were killed on different days, and the wounded skin tissues were used for histologic evaluation and for analysis of malondialdehyde (MDA) level and myeloperoxidase (MPO) activity, wound breaking strength, and collagen content.

RESULTS

Diabetic mice showed delayed wound healing together with low collagen content, breaking strength, and increased MDA levels and MPO activity when compared with their healthy littermates. The administration of raxofelast did not modify the process of wound repair in healthy (db/+) mice, but significantly improved impaired wound healing in diabetic mice through the stimulation of angiogenesis, reepithelialization, synthesis, and maturation of extracellular matrix. Furthermore, raxofelast treatment significantly reduced MDA levels, MPO activity, and increased the breaking strength and collagen content of the wound.

CONCLUSIONS

The current study provides evidence that raxofelast restores wound healing to nearly normal levels in experimental diabetes-impaired wounds and suggests that an increased lipid peroxidation in diabetic mice may have a role in determining a defect of wound repair.

Inhibition of lipid peroxidation restores impaired vascular endothelial growth factor expression and stimulates wound healing and angiogenesis in the genetically diabetic mouse

Impaired wound healing is a well-documented phenomenon in experimental and clinical diabetes. Experimental evidence suggests that a defect in vascular endothelial growth factor (VEGF) regulation might be associated with wound-healing disorders. We studied the involvement of lipid peroxidation in the pathogenesis of altered VEGF expression in diabetes-related healing deficit by using an incisional skin-wound model produced on the back of female diabetic C57BL/KsJ db+/ db+ mice and their normal (db+/+m) littermates. Animals were then randomized to the following treatment: raxofelast (15 mg.kg(-1).day(-1) i.p.), an inhibitor of lipid peroxidation, or its vehicle (DMSO/NaCl 0.9%, 1:1 vol: vol). The animals were killed on different days (3, 6, and 12 days after skin injury), and the wounded skin tissues were used for histological evaluation, for analysis of conjugated dienes (CDs), as an index of lipid peroxidation and wound breaking strength. Furthermore, we studied the time course of VEGF mRNA expression throughout the skin-repair process (3, 6, and 12 days after skin injury), by means of reverse transcriptase-polymerase chain reaction, as well as the mature protein in the wounds. Diabetic mice showed impaired wound healing with delayed angiogenesis, low breaking strength, and increased wound CD content when compared with their normal littermates. In healthy control mice, a strong induction of VEGF mRNA was found between day 3 and day 6 after injury, while no significant VEGF mRNA expression was observed at day 12 after injury. In contrast, VEGF mRNA levels, after an initial increase (day 3), were significantly lower in diabetic mice than in normal littermates, and light induction of VEGF mRNA expression was also present at day 12 after injury. Similarly, the wound content of the angiogenic factor was markedly changed in diabetic mice. Administration of raxofelast did not modify the process of wound repair in normal mice, but significantly improved the impaired wound healing in diabetic mice through the stimulation of angiogenesis, re-epithelization, and synthesis and maturation of extracellular matrix. Moreover, raxofelast treatment significantly reduced wound CD levels and increased the breaking strength of the wound. Lastly, the inhibition of lipid peroxidation restored the defect in VEGF expression during the process of skin repair in diabetic mice and normalized the VEGF wound content. The current study provides evidence that lipid peroxidation inhibition restores wound healing to nearly normal levels in experimental diabetes-impaired wounds and normalizes the defect in VEGF regulation associated with diabetes-induced skin-repair disorders.

Defining a model to predict the distribution of topically applied growth factors and other solutes in excisional full-thickness wounds

Controversy over the efficacy of many topical wound treatments, particularly growth factors, is common, with many clinical practitioners still confused as to the real value of these agents. A serious lack of knowledge appears to exist concerning the diffusion and distribution of topically applied solutes in wounds. Without this basic understanding there seems little chance of accurately predicting the therapeutic window of drugs targeted at cellular activities, such as division and chemotaxis, and processes, such as collagen lattice deposition and contraction, occurring below the surface of the granulating layer. This study was designed to determine the absorption and distribution of a number of radiolabeled solutes (water, sodium chloride, lidocaine) and growth factors (basic fibroblast growth factor, epidermal growth factor) applied topically to full-thickness excisional wounds in rats during the early (2 d), mid (7 d), and late (12 d) stages of repair. Results showed that water and sodium penetrated deepest into wound sites and that changes in water distribution and retention in the wound paralleled the healing process. Multiple stepwise regression showed that molecular weight and tissue depth, but not day of healing, were significant factors in predicting the concentration of each solute in wound and underlying tissue sites. This finding was consistent with a tissue diffusion model developed in this study. Basic fibroblast growth factor and epidermal growth factor only penetrated slightly into the upper granulating layers of the wound site, and calculation of therapeutic doses, based on the percentage of applied solute reaching the deeper granulating layers, is presented.

The development of site-specific drug-delivery systems for protein and peptide biopharmaceuticals

The desire to deliver protein and peptide biopharmaceuticals conveniently and effectively has led to intense investigation of site-specific drug-delivery systems. Despite challenges, progress towards the convenient noninvasive delivery of proteins and peptides has been achieved through specific routes of administration. In addition, the delivery of proteins and peptides to specific sites of action has been utilized to lower the total delivered dose, to gain access to specific organs or body compartments and to concentrate a therapeutic dose at a specific site of pharmacological action.

Stimulation of angiogenesis by FGF-1 delivered through a modified fibrin scaffold

A few studies have indicated that repeated dosing of acidic fibroblast growth factor (FGF-1) is essential to be effective in modulating the wound-healing response. However, little investigation has been done to determine the effective dosing regimen of FGF-1 or the appropriate carrier vehicle for this growth factor. The main objective of this study was to determine the effective angiogenic stimulatatory dose of FGF-1 delivered through a modified fibrin matrix, using a rabbit ear ulcer model. Specifically, the aim was to test the effects of FGF-1 on the angiogenic, fibroblastic, and epithelial responses in a wound model. Five 6-mm diameter ulcers to the depth of bare cartilage were created on each rabbit ear. Four different combinations (0.8, 8, 80, and 800 micrograms/ml) of the growth factor were examined across two periods of study. Pooled modified fibrin was used to deliver the growth factor. Histomorphometrical quantification was conducted after routine histological processing of the ulcers sites. Data analysis indicated a strong correlation between concentration and the histomorphometric response. In general, the growth factor treatments affected the healing response and exhibited a dose-dependent behavior. The addition of FGF-1 led to an increase in the angiogenic and fibroblastic responses, as well as an increase in the epithelialization rate. The preferred dose of 8 micrograms initiated a high epithelialization rate, fibroblastic, and angiogenic responses, and was the lowest dose required to initiate these responses.

The effect of acidic fibroblast growth factor and live yeast cell derivative on tympanic membrane regeneration in a rat model

The current treatment of choice for chronic tympanic membrane perforations is surgery. Recent studies using various polypeptide growth factors to accelerate closure of tympanic membrane perforations in model systems have produced mixed results. This study evaluates the effect of acidic fibroblast growth factor (AFGF) and live yeast cell derivative (LYCD) on the rate of healing of acute tympanic membrane perforations in a rat model. Thirty-seven rats had both ears separately randomized in a blinded fashion to receive AFGF in one of three concentrations, LYCD, or a control solution. The rats initially underwent subtotal removal of the tympanic membranes bilaterally. Solutions were applied to the randomized ears daily for 3 days, starting at the time of the surgical perforation. The ears were photographed every 3 to 8 days for 35 days. The photographs were digitally scanned and a computer analysis was used to calculate the percentage of residual perforation. No significant difference in the rate of healing was observed for ears treated with AFGF or LYCD versus the controls. Given the potential advantages of medical treatment of tympanic membrane perforations and the established efficacy of growth factors in other model systems, however, further research is warranted.

In vivo evaluation for rhGM-CSF wound-healing efficacy in topical vehicles

The wound-healing efficacy of recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF) was studied in a mouse model. Full-thickness wounds were treated with liquid crystalline, emulsion, and niosome vehicles alone and with rhGM-CSF. The control group was non-medicated. Observation of the vehicle groups with and without the rhGM-CSF displayed better healing profiles than the control group. The vehicles were also evaluated among themselves and it was noted that emulsion base and niosome base groups gave significantly better healing profiles and histological results than the liquid crystalline base group. Among the rhGM-CSF containing groups, emulsion formulation displayed a stronger wound-healing effectiveness compared to the other formulations. In vitro release characteristics of the recombinant protein from the three vehicle formulations were demonstrated with diffusion cells. Histological and immunohistochemical evaluation was performed on biopsies taken on the last day of the experiment.

Transfection with aFGF cDNA improves wound healing

Somatic gene therapy is a potentially useful strategy for the delivery of growth factors or cytokines to enhance wound healing. Experimental excisional and incisional wounds in impaired-healing diabetic mice (db/db) were treated with aFGF and with a plasmid coding for aFGF. A eukaryotic expression plasmid composed of the Hst signal peptide sequence in-frame with the human aFGF sequence was used. Transfection of tissues was accomplished either by direct plasmid uptake or by uptake facilitated with cationic liposomes. The results show that the closure of excisional wounds was significantly accelerated (p < 0.05) by topical application of human recombinant aFGF or by transfection with the aFGF plasmid but not by vehicle or control plasmid not containing the aFGF sequence. In incisional wounds, aFGF or transfection with the plasmid significantly increased the wound-breaking strength compared to their corresponding controls (p < 0.05). Quantitative histology of the plasmid-treated incisional wound sections revealed improved wound quality. The transcription of mRNA from human aFGF cDNA in the incisional wound tissue extracts was confirmed by RT-PCR, and the expressed aFGF was detected by immune dot blot and immunohistochemistry assays. The transfection was a transient process with a peak at 9 d in db/+ (littermates of the diabetic mice) incisional wounds, at 36 d in db/db incisional wounds, and at 27 d in db/db excisional wounds. Cells transfected with human aFGF occupied up to 6.4% of the transectional area in the wound sites. Thus, aFGF gene delivery resulted in both gene expression and a functional improvement in healing.

Effect of topical application of a stable prostacyclin analogue, SM-10902 on wound healing in diabetic mice

The mechanism of wound healing induced by topical application of an ointment containing a new stable prostacyclin analogue, SM-10902 ((+)-methyl[2-[(2R,3aS,4R,5R, 6aS)-octahydro-5-hydroxy-4-[(E)-(3S,5S)-3-hydroxy-5-methyl-1- nonenyl]-2-pentalenyl] ethoxy] acetate), was investigated in the full-thickness wounds of genetically diabetic mice (db/db mice). The db/db mice treated with SM-10902 ointment (1, 10 and 100 micrograms/g) showed greater decrease in wound lesion area not covered with epidermis and fewer complete healing days than those treated with ointment base, and the effects of this prostacyclin analogue were greater than those of lysozyme chloride ointment (50 mg/g, Reflap ointment). SM-10902 ointment increased skin blood flow in the central site of the wound with development of wound healing. Histological evaluation of wounds revealed that SM-10902 ointment increased the capillary number during the early stage of the wound-healing process. These results suggest that SM-10902 ointment promotes wound healing through the stimulation of angiogenesis and the improvement of blood flow in neovascularization of repairing wound and may be useful in the treatment of skin ulcers caused by peripheral circulatory insufficiency.

Vascular effects of sustained-release fibroblast growth factors

Since the half-life of most angiogenic growth factors is several hours or less, sustained-release delivery would be optimal for their future clinical use. Two fibroblast growth factors, basic fibroblast growth factor (bFGF) and endothelial cell growth factor (ECGF), were delivered in two sustained-released modalities (poloxamer 407 and a gelatin sponge [Gelfoam]) to attempt to increase soft tissue vascularity. In vitro bioactivity of ECGF-poloxamer formulations was also tested on endothelial cell cultures. Among vascular-compromised skin flaps in rabbits, ECGF-poloxamer (N = 26), bFGF-poloxamer (N = 5), ECGF-poloxamer (N = 9, irradiated), and bFGF-Gelfoam flaps (N = 22) did not demonstrate significant differences in viability and vascularity compared to controls (p > .05). Irradiation had a detrimental effect on both flap vascularity and viability (p = .02). Future efforts for sustained delivery of angiogenic proteins are critical in order to make them clinically useful in wound healing.

Acidic fibroblast growth factor accelerates dermal wound healing in diabetic mice

Acidic fibroblast growth factor (aFGF) is a potent mitogenic and chemotactic agent for vascular endothelial cells, dermal fibroblasts, and epidermal keratinocytes, the principal cellular constituents of skin. To explore its potential to heal chronic dermal wounds, we applied pure recombinant human aFGF topically to full-thickness excisional injuries in healing-impaired genetically diabetic mice. Transformation of the nonlinear percent initial wound areas as a function of time to linear rates of tissue ingrowth from the original wound edges showed that aFGF increased wound closure in a dose-dependent manner. Optimal 3-micrograms/cm2 doses of aFGF nearly tripled the linear rate of healing. The median time to complete closure decreased from 46 d in vehicle-treated wounds to only 16 d in those treated with aFGF. Histomorphometric analyses established that aFGF increased granulation tissue formation and reepithelialization throughout healing. Vehicle- and aFGF-treated wounds appeared to be histologically equivalent by the time of closure. Therefore, aFGF has potential therapeutic applications for promoting healing of dermal ulcers, especially in healing-impaired individuals.

Formulation design of acidic fibroblast growth factor

The design of an aqueous formulation for acidic fibroblast growth factor (aFGF) requires an understanding of the type of compounds that can either directly or indirectly stabilize the protein. To this end, spectrophotometric turbidity measurements were initially employed to screen the ability of polyanionic ligands, less specific compounds, and variations in solution conditions (temperature and pH) to stabilize aFGF against heat-induced aggregation. It was found that in addition to the well-known protection of aFGF by heparin, a surprisingly wide variety of polyanions (including small sulfated and phosphorylated compounds) also stabilizes aFGF. These polyanionic ligands are capable of raising the temperature at which the protein unfolds by 15-30 degrees C. Many commonly used excipients were also observed to stabilize aFGF in both the presence and the absence of heparin. High concentrations of some of these less specific agents are also able to increase the temperature of aFGF thermal unfolding by as much as 6-12 degrees C as shown by circular dichroism and differential scanning calorimetry. Other compounds were found which protect the chemically labile cysteine residues of aFGF from oxidation. Aqueous formulations of aFGF were thus designed to contain both a polyanionic ligand that enhances structural integrity by binding to the protein and chelating agents (e.g., EDTA) to prevent metal ion-catalyzed oxidation of cysteine residues. While room-temperature storage (30 degrees C) leads to rapid inactivation of aFGF in physiological buffer alone, several of these aFGF formulations are stable in vitro for at least 3 months at 30 degrees C. Three aFGF topical formulations were examined in an impaired diabetic mouse model and were found to be equally capable of accelerating wound healing.