Preclinical wound-healing studies with recombinant human basic fibroblast growth factor

Concentration of proinflammatory cytokines in patients with ulcers as a complication of type 2 diabetes mellitus

INTRODUCTION

Difficult healing of chronic wounds is a serious problem for modern medicine. It leads to ulceration, especially in conditions such as diabetic foot syndrome or chronic venous insufficiency. This may be a result of chemical, physical, thermal or biological factors, among others. Analysis of mediators and molecular factors released by the abovementioned structure helps to better understand the mechanism of healing of chronic wounds and the formation of ulcers.

AIM

To assess excretion of selected cytokines in patients with ulcerations as a complication of diabetes mellitus type 2.

MATERIAL AND METHODS

Seventeen patients aged 68-87 took part in the assessment of wound healing in patients with ulceration in the course of diabetes mellitus type 2. The control group consisted of 21 healthy patients aged 32-62. In the blood serum bFGF, TNF-α, IL-4, TGF-β1, TGF-β2 and TGF-β3 were determined.

RESULTS

A significant difference was found in bFGF, IL-4, TGF-β1, TGF-β2, and TGF-β3 levels. Concentration of bFGF was 12% lower in patients with ulcers than in the non-ulcerated control group (p = 0.013). IL-4 concentration was 46% lower in patients with ulcers than in the non-ulcerated control group (p = 0.002). TGF-β1, TGF-β2 and TGF-β3 concentrations were also lower in the group of patients with ulcers compared to those in the non-ulcerated control group.

CONCLUSIONS

Reduced concentrations of selected cytokines and growth factors may indicate abnormal activity of the cells that secrete them and affect the healing process of chronic wounds, hindering and delaying the healing process.

Regeneration of injured skin and peripheral nerves requires control of wound contraction, not scar formation

We review the mounting evidence that regeneration is induced in wounds in skin and peripheral nerves by a simple modification of the wound healing process. Here, the process of induced regeneration is compared to the other two well-known processes by which wounds close, i.e., contraction and scar formation. Direct evidence supports the hypothesis that the mechanical force of contraction (planar in skin wounds, circumferential in nerve wounds) is the driver guiding the orientation of assemblies of myofibroblasts (MFB) and collagen fibers during scar formation in untreated wounds. We conclude that scar formation depends critically on wound contraction and is, therefore, a healing process secondary to contraction. Wound contraction and regeneration did not coincide during healing in a number of experimental models of spontaneous (untreated) regeneration described in the literature. Furthermore, in other studies in which an efficient contraction-blocker, a collagen scaffold named dermis regeneration template (DRT), and variants of it, were grafted on skin wounds or peripheral nerve wounds, regeneration was systematically observed in the absence of contraction. We conclude that contraction and regeneration are mutually antagonistic processes. A dramatic change in the phenotype of MFB was observed when the contraction-blocking scaffold DRT was used to treat wounds in skin and peripheral nerves. The phenotype change was directly observed as drastic reduction in MFB density, dispersion of MFB assemblies and loss of alignment of the long MFB axes. These observations were explained by the evidence of a surface-biological interaction of MFB with the scaffold, specifically involving binding of MFB integrins α1 β1 and α2 β1 to ligands GFOGER and GLOGER naturally present on the surface of the collagen scaffold. In summary, we show that regeneration of wounded skin and peripheral nerves in the adult mammal can be induced simply by appropriate control of wound contraction, rather than of scar formation.

Syndesome Therapeutics for Enhancing Diabetic Wound Healing

Chronic wounds represent a major healthcare and economic problem worldwide. Advanced wound dressings that incorporate bioactive compounds have great potential for improving outcomes in patients with chronic wounds but significant challenges in designing treatments that are effective in long-standing, nonhealing wounds. Here, an optimized wound healing gel was developed that delivers syndecan-4 proteoliposomes ("syndesomes") with fibroblast growth factor-2 (FGF-2) to enhance diabetic wound healing. In vitro studies demonstrate that syndesomes markedly increase migration of keratinocytes and fibroblasts isolated from both nondiabetic and diabetic donors. In addition, syndesome treatment leads to increased endocytic processing of FGF-2 that includes enhanced recycling of FGF-2 to the cell surface after uptake. The optimized syndesome formulation was incorporated into an alginate wound dressing and tested in a splinted wound model in diabetic, ob/ob mice. It was found that wounds treated with syndesomes and FGF-2 have markedly enhanced wound closure in comparison to wounds treated with only FGF-2. Moreover, syndesomes have an immunomodulatory effect on wound macrophages, leading to a shift toward the M2 macrophage phenotype and alterations in the wound cytokine profile. Together, these studies show that delivery of exogenous syndecan-4 is an effective method for enhancing wound healing in the long-term diabetic diseased state.

Surface biology of collagen scaffold explains blocking of wound contraction and regeneration of skin and peripheral nerves

We review the details of preparation and of the recently elucidated mechanism of biological (regenerative) activity of a collagen scaffold (dermis regeneration template, DRT) that has induced regeneration of skin and peripheral nerves (PN) in a variety of animal models and in the clinic. DRT is a 3D protein network with optimized pore size in the range 20-125 µm, degradation half-life 14 ± 7 d and ligand densities that exceed 200 µM α1β1 or α2β1 ligands. The pore has been optimized to allow migration of contractile cells (myofibroblasts, MFB) into the scaffold and to provide sufficient specific surface for cell-scaffold interaction; the degradation half-life provides the required time window for satisfactory binding interaction of MFB with the scaffold surface; and the ligand density supplies the appropriate ligands for specific binding of MFB on the scaffold surface. A dramatic change in MFB phenotype takes place following MFB-scaffold binding which has been shown to result in blocking of wound contraction. In both skin wounds and PN wounds the evidence has shown clearly that contraction blocking by DRT is followed by induction of regeneration of nearly perfect organs. The biologically active structure of DRT is required for contraction blocking; well-matched collagen scaffold controls of DRT, with structures that varied from that of DRT, have failed to induce regeneration. Careful processing of collagen scaffolds is required for adequate biological activity of the scaffold surface. The newly understood mechanism provides a relatively complete paradigm of regenerative medicine that can be used to prepare scaffolds that may induce regeneration of other organs in future studies.

Impact of basic fibroblast growth factor on healing of tympanic membrane perforations due to direct penetrating trauma: a prospective non-blinded/controlled study

OBJECTIVE

To investigate the effect of direct application of basic fibroblast growth factor (bFGF) on healing of tympanic membrane perforations due to direct traumatic penetration through the external auditory canal.

DESIGN

A prospective non-blinded controlled study.

SETTING

University-affiliated teaching hospital.

PARTICIPANTS

In total, 104 patients with small [<25%] penetrating perforations were recruited. They were alternatively allocated to two groups: Control (spontaneous healing, n = 51) and FGF treatment (direct application of bFGF drops in the clinic and repeated daily by the patient, n = 53).

OUTCOMES

Perforation closure rate and time and hearing gain were recorded and compared between the two groups. Information on earache, dizziness and facial paralysis was also collected.

RESULTS

In total, 93 (89%) patients were finally analysed. The closure rate at 3 m of the perforations in the control spontaneous healing and bFGF treatment groups were 77% and 100%, respectively; the difference was statistically significant (P = 0.01). The average closure time was 43.1 ± 2.5 days (range, 17-57 days) for control patients, which was significantly longer (P < 0.01) than that for the bFGF-treated patients (12.6 ± 1.2 days; range, 3-21 days). The mean hearing improvement at 3 m was not significantly different between the FGF treatment and control groups (1.7 ± 2.4 dB vs 11.5 ± 1.9 dB, P > 0.05). No significant difference was observed in earache, dizziness and facial paralysis between two groups.

CONCLUSIONS

Direct application of bFGF may offer an effective topical management of penetrating traumatic tympanic membrane perforations, particularly for small-sized perforations.

Healing large traumatic eardrum perforations in humans using fibroblast growth factor applied directly or via gelfoam

OBJECTIVE

The goal of this study was to evaluate the effects of conservative treatment and fibroblast growth factor (FGF) applied directly or via Gelfoam on the healing of large traumatic tympanic membrane perforations (TMPs) in humans.

STUDY DESIGN

Prospective, randomized, controlled trial.

METHODS

A randomized prospective analysis was performed between February 2009 and January 2011 for the treatment of traumatic TMPs in humans that affected greater than 50% of the TM. The closure rate, closure time, hearing gain, and rate of otorrhea were compared among the direct application of FGF, FGF via Gelfoam, and conservative treatment.

RESULTS

A total of 94 patients were analyzed. The closure rates of large perforations in the direct FGF application, FGF via Gelfoam, and observation groups were 100%, 97%, and 55%, respectively. FGF-treated groups had significantly improved closure rates compared with the observation group (p < 0.05). However, the closure rate did not differ significantly between patients who received FGF only and those who received FGF via Gelfoam (p > 0.05). FGF-treated groups showed shorter mean closure times compared with the observation group (p < 0.05). However, the closure time did not differ significantly between FGF-treated groups (p > 0.05).All perforations were closed within 2 weeks, regardless of the presence of curled edges in the FGF-treated groups.

Effects of the basic fibroblast growth factor and its anti-factor in the healing and collagen maturation of infected skin wound

PURPOSE: The infection is one of the main factors that affect the physiological evolution of the surgical wounds. The aim of this work is to evaluate the effects of fibroblast growth factor (FGFâ) and anti-FGFâ in the healing, synthesis and maturation of collagen when topically used on infected skin wounds of rats. METHODS: An experimental study was perfomed in 60 male Wistar rats. All animals were divided in two groups (A and B). Each group was divided in three subgroups A1, B1; A2, B2 and A3, B3. After anesthesia with pentobarbital, two open squared wounds (1cm²), 4cm distant to each other, were done in the dorsal skin of all the rats. In group A (n=30) the wounds were contaminated with multibacterial standard solution, and in group B(n=30) the wounds were maintained sterile. These wounds were named F1 (for inflammation analysis) and F2 (for collagen study). The open wounds of A1 and B1 rats were topically treated with saline solution, A2 and B2 were treated with FGFâ and subgroups A3 and B3 were treated with FGFâ and anti-FGFâ. The rats were observed until complete epitelization of F2 wounds for determination of healing time and the expression of types I and III collagen, using Picro Sirius Red staining. Inflammatory reaction in F1 wounds was studied using hematoxilineosin staining. The three variable was measured by the Image Pro-Plus Média Cybernetics software. The statistical analysis was performed by ANOVA and Tukey test, considering p<0.05 as significant. RESULTS: It was observed that infection retarded significantly (p<0.05) the time of wound scarring and the topical application of FCFb reverted the inhibition of healing caused by bacteria. The inflammatory reaction was greater in the subgroup B2 than in B1 and A3, and the difference was significant (p<0.05). It was observed greater expression of type I collagen in all the subgroups treated with FCFb, when compared with the untreated subgroups. Type III collagen was significantly decreased in wounds of B3 rats, comparing to the other subgroups. CONCLUSIONS: The FCFb accelerated the healing of open infected wounds and contributed with maturation of collagen, enhancing the type I collagen density. The anti-FCFb antibody was able to attenuate the production of both type I and III collagen.

The generation of germline transgenic silkworms for the production of biologically active recombinant fusion proteins of fibroin and human basic fibroblast growth factor

We generated germline transgenic silkworms bearing a fibroin light chain (FL) promoter-driven FL gene whose 3'-end was flanked with human basic fibroblast growth factor (bFGF) gene, FL/bFGF gene. The cocoons from transgenic worms were trypsinized to remove sericin layers, and treated with solution containing CaCl(2), ethanol, and water at a molar ratio of 1:2:8 (CaCl(2)/ethanol/water) to solubilize fibroin layers. Western blot analysis showed that the recombinant protein, r(FL/bFGF), was solubilized with CaCl(2)/ethanol/water, but not with trypsin, indicating that r(FL/bFGF) was in fibroin layers. Thus, it was concluded that the worms spun cocoons whose fibroin layers were composed of the inherent gene-derived natural fibroin (nF) and r(FL/bFGF). The mixture of nF and r(FL/bFGF) was dubbed r(FL/bFGF)nF. The solubilized r(FL/bFGF)nF was refolded using the glutathione redox system. Human umbilical vein endothelial cells (HUVECs) grew in the refolded r(FL/bFGF)nF-containing culture media, showing that bFGF in r(FL/bFGF) was biologically active. r(FL/bFGF)nF immobilized on a culture dish also supported the growth of HUVECs in bFGF-free media, suggesting the usefulness of r(FL/bFGF)nF as a new biomaterial for tissue engineering. The currently developed transgenic silkworms will be suitable for mass production of fibroins bearing a variety of biological activities.

The effects of basic fibroblast growth factor on postoperative mastoid cavity problems

OBJECTIVES

To present the effects of basic fibroblast growth factor on intractable cavity problems and discuss the mechanisms of its effects.

METHODS

We treated three ears with postoperative open cavities. All three cases had suffered from chronic discharge of the ear for 7, 10, and 30 years, respectively; 100 microg/ml of trafermin (genetic recombination) solution, as basic fibroblast growth factor, was dropped into the open cavity once daily. If bacterial and/or fungal infection was observed, antibiotics and/or antifungal agents were administered locally twice daily.

RESULTS

The cavities epithelialized and were cured within 2 months using this treatment.

CONCLUSION

Our results suggest that basic fibroblast growth factor stimulates the proliferation and differentiation of keratinocytes, fibroblasts, and endothelial cells, leading to accelerated wound healing. The basic fibroblast growth factor agent appears to be highly effective in treating intractable cavity problems.

The fibroblast-populated collagen matrix as a model of wound healing: a review of the evidence

The fibroblast-populated collagen matrix (FPCM) has been utilized as an in vitro model of wound healing for more than 2 decades. It offers a reasonable approximation of the healing wound during the phases of established granulation tissue and early scar. The gross and microscopic morphology of the FPCM and the healing wound are similar at analogous phases. The processes of proliferation, survival/apoptosis, protein synthesis, and contraction act in similar directions in these two models, and the response to exogenous agents also is consistent between them. If its limitations are respected, then the FPCM can be used as a model of the healing wound.

Progranulin is a mediator of the wound response

Annually, 1.25 million individuals suffer burns in the United States and 6.5 million experience chronic skin ulcers, often from diabetes, pressure or venous stasis. Growth factors are essential mediators of wound repair, but their success as therapeutics in wound treatment has, so far, been limited. Therefore, there is a need to identify new wound-response regulatory factors, but few have appeared in recent years. Progranulin (also called granulin or epithelin precursor, acrogranin or PC-derived growth factor) is a growth factor involved in tumorigenesis and development. Peptides derived from progranulin have been isolated from inflammatory cells, which led to suggestions that progranulin gene products are involved in the wound response, but this remains undemonstrated. We report that in murine transcutaneous puncture wounds, progranulin mRNA is expressed in the inflammatory infiltrate and is highly induced in dermal fibroblasts and endothelia following injury. When applied to a cutaneous wound, progranulin increased the accumulation of neutrophils, macrophages, blood vessels and fibroblasts in the wound. It acts directly on isolated dermal fibroblasts and endothelial cells to promote division, migration and the formation of capillary-like tubule structures. Progranulin is, therefore, a probable wound-related growth factor.

Ação do fator de crescimento de fibroblasto básico na cicatrização da aponeurose abdominal de ratos

OBJETIVO: Trabalho realizado em ratos com o objetivo de estudar o efeito do Fator de Crescimento de Fibroblastos básico (FCFb) na cicatrização da aponeurose abdominal. MÉTODOS: Foram usados 20 ratos Wistar separados aleatoriamente em 2 grupos iguais. Os animais foram anestesiados com pentobarbital sódico na dose de 20 mg/Kg por via intraperitoneal e submetidos a laparotomia mediana de 4 cm, cuja camada aponeurótica foi suturada com mononylon 5-0. No grupo I foi aplicada a dose de 5mg de FCFb sobre a sutura da aponeurose. No grupo II (controle) foi aplicada solução salina 0,9% sobre a linha se sutura. Após observação por 7 dias os animais foram mortos com superdose de anestésico. A camada aponeurótica com 1,5 cm de largura foi submetida a teste de resistência à tensão empregando a Máquina de Ensaios EMIC MF500. Biópsias das zonas de sutura foram processadas e coradas com HE e o tricômico de Masson. Os achados histopatológicos foram quantificados através de sistema digital (Image pro-plus) de captura e processamento de imagens. Os dados obtidos foram analisados pelo teste T com significância 0,05. RESULTADOS: Nos animais do grupo I (experimental) a zona de sutura da camada aponeurótica suportou a carga de 1.103± 103,39gf. A quantificação dos dados histopatológicos desse grupo atingiu a densidade média 226± 29,32. No grupo II (controle) a carga suportada pela zona de sutura foi de 791,1± 92,77 gf. Quando foram comparadas as médias das resistências à tensão dos dois grupos, observou-se uma diferença significante (p<0,01). O exame histopatológico das lâminas desse grupo relevou densidade média 114,1± 17,01, correspondendo a uma diferença significante quando comparadas as médias dos dois grupos (p<0,01). CONCLUSÃO: Os dados permitem concluir que o FCFb contribuiu para aumentar a resistência da aponeurose suturada e para melhorar os parâmetros histopatológicos da cicatrização.

The effects of basic fibroblast growth factor (bFGF) on the breaking strength of acute incisional wounds

Many researchers have reported the effects of cytokines on ulcers, especially on chronic ulcers. However, the long-term influences of cytokines on acute incisional wounds with respect to breaking strength, quality of the scar etc. have not been elucidated completely. In the present study, the breaking strength of scars produced by full thickness incisional wounds of the skin created on backs of rabbits were compared when the wounds were treated by conventional suturing or with basic fibroblast growth factor (bFGF) in addition to suturing. We administered bFGF to full thickness acute incisional wounds of the skin created on backs of rabbits. The breaking strengths of wounds treated by conventional suturing and those treated with bFGF soon after the operation were compared as were the conditions of the scars after long-term follow up of up to 7 weeks. They were also examined histopathologically. Administration of bFGF at the time of wound closure, especially 1.0 microg in amount per cm, increased the breaking strength significantly compared to the control group from 5 weeks after the operation. Moreover, histopathological examination revealed that there was rich vascularization soon after the operation and an arrangement of collagen fibers which lenticulated horizontally from the 5th week and later after the operation in the bFGF treated groups in a dose dependent manner. This study demonstrates that administration of bFGF at the time of wound closure significantly increased the breaking strength compared to the control group from 5 weeks after the operation. And the administration of bFGF also improved the quality of the scar, the condition of the scar by surface condition by inspection as well as the width of scar at histological evaluations. So we think this cytokine may be highly effective clinically. This may be especially true for patients whose wound healing process tends to be delayed such as aged patients or when high breaking strength is recommended even for patients with normal wound healing potential.

Effects of collagen matrix containing transforming growth factor (TGF)-beta(1) on wound contraction

We evaluated the effectiveness of transforming growth factor (TGF)-beta(1) on wound contraction, both alone and in combination with collagen matrix, using an in vivo delayed wound healing type model. To clarify the mechanisms involved in the effectiveness of TGF-beta(1), we also used a fibroblast-populated collagen gel contraction in vitro model. Although we found that TGF-beta(1) significantly accelerated contraction of the fibroblast-populated collagen gel in vitro, we demonstrated that both collagen matrix alone and 1.0 microg of TGF-beta(1) alone significantly inhibited wound contraction in the in vivo model. In addition, the combination of TGF-beta(1) and collagen matrix was much more effective than TGF-beta(1) alone, a finding which was supported by histopathological examination. Wounds treated with collagen matrix containing TGF-beta(1) showed horizontal rearrangement of collagen fibers in the dermal part as well as evidence of active fibroblast proliferation, which was not observed in the scar regions of controls. These results show that the application of TGF-beta(1) treated collagen matrix is effective for preventing contraction producing so called "neodermis" in treating a delayed healing type model and may be highly beneficial for treating chronic wounds.

Remodeling of extracellular matrix in gastric ulceration

The quality of ulcer repair remains crucial for the stability of the injured tissue and for preventing recurrence. Therefore, we studied the temporo-spatial expression of the fibrillar and basement membrane collagens (types I, III, and IV), the collagenase MMP-2 as well as its inhibitor TIMP-1 before and after oral administration of basic fibroblast growth factor (b-FGF) over 30 days in acetic acid-induced rat gastric ulcers. The alterations and the exact location of the mRNA transcripts and their precipitated proteins were visualized by means of radioactive in situ hybridization and immunohistochemistry. Our data show that hybridization signals of procollagen I could first be identified 2 hours after ulcer induction. After 12 hours the ulcer was established and the mRNA was enhanced at the ulcer margin. After 24-48 hours the other procollagen transcripts were detected and all were further upregulated over the mesenchymal cells of all gastric layers up to 21 days, then declined at 30 days. In contrast, MMP-2 became prominent after 48 hours and up to 21 days. TIMP-1 was enhanced at 72 hours. After oral administration of b-FGF the transcriptional activity of the procollagens and MMP-2 was not significantly altered, while ulcer diameter was significantly reduced. We conclude that the early onset and long duration of collagens' expression points to their central structural and functional role in gastric ulcer healing. MMP-2 seems to be involved in both active ulceration and ECM remodeling. The timing of TIMP/MMP expression may be critical for proper restoration of gastric wall integrity.

Effects of a collagen matrix containing prostaglandin E(1) on wound contraction

In this study, we evaluated the effectiveness of prostaglandin (PG) E(1) in inhibiting wound contraction, both alone and in combination with collagen matrix, using a in vivo full thickness skin defect model. To clarify the mechanisms involved in this inhibition we also used a fibroblast-populated collagen gel contraction in vitro model. We demonstrated that collagen matrix alone significantly inhibited wound contraction PG E(1) alone did not. Interestingly, their combination was much more effective than either collagen matrix or PG E(1) alone, a finding which was also supported by histopathological examination. Wounds treated with collagen matrix, but not control wounds, showed horizontal rearrangement of collagen fibers in the dermal part as well as evidence of active fibroblast proliferation which was not observed in scar regions surrounded by normal dermis. With the fibroblast-populated collagen gel contraction in vitro model, we found that PG E(1) significantly inhibited contraction at a high dose. It was concluded that collagen matrix combined with PG E(1) is effective for preventing contracture producing so called neodermis than collagen matrix alone, which remains one of the most challenging problems in treating full thickness type wounds.

FGF2-Targeted adenovirus encoding platelet-derived growth factor-B enhances de novo tissue formation

Gene therapy has yet to achieve reproducible clinical efficacy, due to inadequate gene delivery, inadequate gene expression, or dose-limiting toxicity. We have developed a gene therapy technology for tissue repair and regeneration that employs a structural matrix for DNA delivery. The matrix holds the DNA vector at the treatment site and provides a scaffolding for in-growth and accumulation of repair cells and efficient DNA transfection. We now report, for the first time, matrix-mediated delivery of targeted DNA vectors for soft tissue repair. A collagen matrix was used to deliver an adenoviral vector encoding platelet-derived growth factor-B (AdPDGF-B), resulting in efficient transgene expression in vitro and in vivo. Increases in the overall levels of expression and in the relative amounts of secreted PDGF-BB were achieved when AdPDGF-B was conjugated to fibroblast growth factor (FGF2) such that the virus was targeted for cellular uptake via FGF receptors. Matrix-mediated delivery of AdPDGF-B enhanced wound healing responses in vivo, and FGF2 targeting generated effects comparable to nontargeted vectors at significantly lower doses. Therefore, matrix-mediated delivery in combination with FGF2 targeting overcomes some of the safety and efficacy limitations of current gene therapy strategies and is an attractive therapeutic approach for tissue repair and regeneration.

Ischemia increases the angiogenic potency of basic fibroblast growth factor (FGF-2)

The aim of this study was to investigate the angiogenic response to exogenously administered basic fibroblast growth factor (FGF-2) in normal and ischemic skin, using the hairless mouse ear microcirculatory model. The hairless mouse ear is a well-established model for in vivo studies of skin microcirculation. Using this model, angiogenesis- and angiogenesis-associated changes in the microcirculation can be directly and continuously viewed and quantified in a variety of different experimental settings. To create ischemia in the mouse ear, all but one of the three to four feeding vessels nourishing the ear were ligated 3 days prior to a local subdermal injection of FGF-2 (9.3 + 1-0.5 mm/mm2) or saline into the dorsum of the ears. Angiogenesis was quantified by direct observation, at high magnification, of the injection site where increases in total vessel length (TVL) were measured repeatedly over 18 days following injection. We found a significant (P < 0.01) increase in TVL in normal and ischemic ears injected with FGF-2. Saline injection also induced a significant increase in TVL in ischemic ears. However, the angiogenic response to FGF-2 in ischemic ears was significantly stronger than saline alone in ischemic ears or saline or FGF-2 in normal ears. This response could be used clinically to accelerate angiogenesis and thus increase perfusion in ischemic tissue.

Sequential cytokine therapy for pressure ulcers: clinical and mechanistic response

OBJECTIVE

To compare the healing response of sequential topically applied cytokines to that of each cytokine alone and to a placebo in pressure ulcers, and to evaluate the molecular and cellular responses.

SUMMARY BACKGROUND DATA

Because of a deficiency of cytokine growth factors in chronic wounds and the reversal of impaired healing in animal models, pressure ulcer trials have been performed with several exogenously applied growth factors. Because single-factor therapy has not been uniformly successful, combination or sequential cytokine therapy has been proposed. Laboratory data have suggested that sequential treatment with granulocyte-macrophage/colony-stimulating factor (GM-CSF)/basic fibroblast growth factor (bFGF) might augment the previously reported effect of bFGF alone.

METHODS

A masked, randomized pressure ulcer trial was performed comparing sequential GM-CSF/bFGF therapy with that of each cytokine alone and with placebo during a 35-day period. The primary measure was wound volume decrease over time. Cytokine wound levels and mRNA levels were serially determined. Fibroblast-populated collagen lattices (FPCLs) were constructed from serial fibroblast biopsies. Cellular ultrastructure was evaluated by electron microscopy. Changes in ease of surgical closure and its relative cost were determined.

RESULTS

Ulcers treated with cytokines had greater closure than those in placebo-treated patients. Patients treated with bFGF alone did the best, followed by the GM-CSF/bFGF group. Patients treated with GM-CSF or bFGF had higher levels of their respective cytokine after treatment. Patients with the greatest amount of healing showed higher levels of platelet-derived growth factor (PDGF) on day 10 and transforming growth factor beta (TGFbeta1) on day 36. Message for the bFGF gene was upregulated after treatment with exogenous bFGF, suggesting autoinduction of the cytokine. FPCLs did not mimic the wound responses. Ultrastructure of wound biopsies showed response to bFGF. Treatment with any of the cytokines improved the wound by allowing easier wound closure. This was most marked for the bFGF-alone treatment, with a cost savings of $9,000 to $9,200.

CONCLUSIONS

Treatment with bFGF resulted in significantly greater healing than the other treatments in this trial. The clinical response appeared to be related to upregulation of the bFGF message and to increased levels of PDGF-AB, bFGF, and TGFbeta1 in the wounds and changes in ultrastructure. The resultant improvements could be correlated with cost savings.

Effects of a collagen matrix containing basic fibroblast growth factor on wound contraction

We evaluated the effectiveness of basic fibroblast growth factor (bFGF) in inhibiting wound contraction, both alone and in combination with collagen matrix, using a simulated in vivo delayed healing type model. We also studied the mechanisms involved in this inhibition in in vitro experiments using fibroblast populated collagen gels. As a result, we were able to demonstrate that both collagen matrix and bFGF significantly inhibited wound contraction; especially, bFGF acted in a dose-dependent fashion. Interestingly, their combination was much more effective than either collagen matrix or bFGF alone, a finding that was supported by the histopathological data. Wounds treated with collagen matrix, but not control wounds, showed horizontal rearrangement of collagen fibers in dermis as well as evidence of fibroblast proliferation, which was not observed in scar regions surrounded by normal dermis. Using fibroblast-populated collagen gel contraction as an in vitro model, we found that bFGF significantly inhibited contraction. Taking all these results together, it was concluded that collagen matrix is useful not only as a carrier of cytokines such as bFGF, but also for the quick closure of chronic wounds, thereby preventing contracture, which remains one of the most challenging problems in treating this type of wound. Application of bFGF-treated collagen matrix to chronic wounds such as decubitus, and diabetic and leg ulcers may prove to be highly beneficial in clinical practice.

In vitro effects of epidermal growth factor or insulin-like growth factor on tenoblast migration on absorbable suture material

OBJECTIVE

To determine the effects of epidermal growth factor (EGF) or insulin-like growth factor (IGF) on tenoblast migration on absorbable suture material using an in vitro model.

STUDY DESIGN

An in vitro evaluation of tenoblast migration.

ANIMAL OR SAMPLE POPULATION

Segments of the long digital flexor tendon were obtained from Cobb chickens (9-11 weeks old) immediately after the birds were euthanatized.

METHODS

Tissue culture explants of tendons containing absorbable suture material were treated with either EGF or IGF. Tenoblast migration was assessed daily using an inverted microscope equipped with bright field and phase optics. Tenoblast migration was assessed according to the following criteria: time of first cell appearance, percent of explant interfaces producing cells, migration distance, and terminal migration index at 120 and 168 hours.

RESULTS

EGF had a stimulatory effect on tenoblast migration for cells originating from the endotenon interfaces. No significant effect was noted on migration distance for cells originating from epitenon interfaces. A stimulatory effect on the percentage of interfaces producing cells and a significant decrease in time of first cell appearance were also observed after EGF treatment. IGF-stimulated cell migration distance for epitenon interfaces but this stimulatory effect did not occur at a higher concentration. IGF was inhibitory to percent of epitenon and endotenon interfaces producing cells but decreased time of first cell appearance at low concentration.

CONCLUSIONS

Using an in vitro model, EGF had a stimulatory effect on tenoblast migration. IGF was stimulatory at low concentration levels but inhibitory at a higher concentration. Increased migration distance was observed for endotenon interfaces after EGF treatment and for epitenon interfaces after IGF treatment.

CLINICAL RELEVANCE

EGF or IGF might enhance tendon repair if they could be delivered to the repair site. Incorporation of EGF or IGF into suture material would allow slow release and prolonged exposure of migrating tenoblasts to growth factors.

The future of recombinant growth factors in wound healing

For more than a decade, clinical trials have been conducted of the application of topical exogenous recombinant growth factors in attempts to accelerate the healing of chronic wounds. Although the results of some of these trials have been encouraging, overall the results have been somewhat discouraging. Much of the difficulty lies in the paucity of carefully controlled clinical trials of wound healing. Since wound healing is a complex process that can be influenced, both positively and negatively, by many factors, designing these trials has proved difficult. To date, only a single recombinant growth factor-recombinant human platelet-derived growth factor-BB (rhPDGF-BB)- has been approved by the US Food and Drug Administration; and that only for use in diabetic foot ulcers. It is unlikely, however, that a single growth factor will be able to resolve all issues of repair or strengthen all vulnerabilities of chronic wounds. Our expectation, therefore, is that growth factors, cytokines, and other biologic agents will be used more specifically in the future, for example, by targeting growth factor therapy at those specific components or processes that a given wound uses to heal.

Apoptosis in the chick wing bud and the permanence of FGF-2 rescue

Two regions of programmed cell death that occur in the mesoderm of developing chick wing buds were studied in vitro. The opaque patch (OP) and posterior necrotic zone (PNZ) were examined for the presence of internucleosomal DNA degradation and for rescue by protein synthesis inhibition, two defining characteristics of apoptosis. Agarose gel electrophoresis showed that DNA from OP and PNZ tissue was cleaved into nucleosome size pieces and this cleavage was prevented by inhibition of protein synthesis with cycloheximide. Both regions showed rescue with cycloheximide as determined by the chromium release assay and examination of electron micrographs. Also, the permanence of basic fibroblast growth factor (EGF-2) rescue in the OP and NPZ was examined using the chromium release assay. While rescue in the OP was found to be permanent, rescue in the PNZ only delayed death while FGF-2 was present in the culture medium. This research shows that death in the OP and PNZ exhibits internucleosomal DNA fragmentation and is prevented by inhibition of protein synthesis with cycloheximide, biochemically characterizing this death as apoptosis. It also suggests that in vitro FGF-2 rescue is permanent in the OP but is merely a delay of cell death in the PNZ.

Effects of basic fibroblast growth factor on in vivo cerebral tumorigenesis in rats

OBJECTIVE

In vitro evidence suggests that basic fibroblast growth factor (bFGF) promotes tumor cell proliferation and angiogenesis. In this study, we evaluated the early and delayed effects of recombinant human bFGF on the early and late phases of in vivo, in situ tumorigenesis in rats.

METHODS

Brain tumors were induced by transplacentally exposing fetal rats to N-nitrosoethylurea on Day 17 of pregnancy. On postnatal (PN) Day 60 or 90, N-nitrosoethylurea-exposed rats underwent stereotactic intraventricular implantation of Gelfoam saturated with bFGF (60 micrograms) or vehicle; the rats were killed 4 days (early group) or 30 days (delayed group) later. The early and delayed effects of bFGF on the early phase of tumorigenesis (PN Day 60) were evaluated in 14 and 10 rats, respectively; early and delayed effects on the late phase of tumorigenesis (PN Day 90) were evaluated in 12 rats each.

RESULTS

Histological examination 30 days after implantation showed a significantly higher tumor rate in rats that had been treated with bFGF on PN Day 90, compared with vehicle-treated control rats (P < 0.05); furthermore, in the bFGF-treated animals there was significantly greater intratumoral and periventricular glial fibrillary acidic protein expression, as determined immunohistochemically. Increased vascularity in the tumor ipsilateral to the implant was found in 2 of 14 rats that had been treated with bFGF on PN Day 60.

CONCLUSION

These findings support in vitro evidence that bFGF and its receptor complex are implicated in the genesis and progression of N-nitrosoethylurea-induced brain tumors in this animal model.

Basic fibroblast growth factor mediates angiogenic activity in early surgical wounds

BACKGROUND

Wound angiogenesis is believed to be initiated by the early rapid release of performed growth factors such as basic fibroblast growth factor (bFGF). However, neither the angiogenic environment of early surgical wounds nor the potential contribution of bFGF to early surgical wound angiogenesis has been investigated.

METHODS

We collected surgical drain fluid (SDF) from closed suction drains 6 hours to 6 days after operation. SDF was tested for endothelial cell (EC) proliferative and chemotactic activity and for the capacity to stimulate angiogenesis in vivo in the rat corneal assay. bFGF levels of SDF were determined with enzyme-linked immunosorbent assay. Neutralizing antibody to bFGF was used to determine the contribution of bFGF to SDF activity.

RESULTS

The EC proliferative activity of SDF was maximal on postoperative day 0 (POD 0, 390% that of normal serum) and then fell by 41% on POD 1 and to near serum levels thereafter. SDF from PODs 0 and 1 also showed marked EC chemotactic activity and stimulated rapid formation of new vessels without signs of inflammation when implanted into rat corneas. The temporal appearance of bFGF in these exudates showed a pattern similar to EC proliferative activity, peaking on POD at 854 pg/ml and decreasing 80% by POD 2. Neutralizing antibody to bFGF decreased he proliferative activity of SDF from PODs 0 and 1 to near serum levels and substantially decreased the chemotactic and the in vivo neovascular response to SDFs.

CONCLUSIONS

Surgical wounds are characterized by a rapid and early angiogenic environment that is mediated in part by bFGF, suggesting that tissue or platelet stores of bFGF may initiate wound repair.

Basic fibroblast growth factor for stimulation of bone formation in osteoinductive or conductive implants

Basic Fibroblast Growth Factor (bFGF) is one of the endogenous factors found in bone matrix. bFGF is a mitogen for many cell types, including osteoblasts and chondrocytes. It can stimulate angiogenesis and osteoblast gene expression. The purpose of this study was to investigate whether exogenous bFGF can stimulate the formation of bone in bone grafts and in a bone graft substitute. In a model using demineralized bone matrix implants for bone induction, a dose of 15 ng bFGF per implant increased the number of chondrocytes and the amount of bone, whereas 1900 ng greatly inhibited cartilage and bone formation. These results are consistent with previous studies with this model, showing that a lower dose of bFGF increased bone calcium content and a higher dose reduced it. Thus, exogenous bFGF can stimulate proliferation during early phases of bone induction. A new device, the bone conduction chamber, was developed for the application of bFGF to bone conductive materials. This model made it possible to demonstrate a difference between the conductive properties of bone grafts and porous hydroxyapatite. bFGF increased bone ingrowth into bone graft inside the chamber and showed a biphasic dose-response curve, so that 8-200 ng per implant (0.4-10 ng/mm3) increased bone ingrowth, but higher or lower doses had no effect. The same doses had the same effects in porous hydroxyapatite. In both bone grafts and porous hydroxyapatite, the highest dose still caused an increase in ingrowth of fibrous tissue. The effect on bone ingrowth was first detected after 6 weeks, regardless if administration of bFGF started at implantation or 2 weeks later, using an implanted minipump. Hyaluronate gel was effective as a slow-release carrier for bFGF. In conclusion, bFGF stimulates bone formation in bone implants, depending on dose and method for administration.

The use of basic fibroblast growth factor (bFGF) for enhancement of bone ingrowth into pyrolized bovine bone

This pilot study aimed to investigate whether in vivo cultivation of bone in porous scaffolds can be enhanced by the use of growth factors. Four adult Göttingen minipigs received subperiosteal implantation of a block of pyrolized bovine bone on either side of the mandible. The blocks were covered with polylactic membrane. On one side, the implants were loaded with 240 micrograms of lyophilized basic fibroblast growth factor (bFGF). After 5 months, bone ingrowth was found throughout the whole block into the peripheral pore layers regardless of whether or not the scaffolds had been loaded with bFGF. Fluorescence labels likewise showed no significant differences in bone formation.

Direct visualization and measurements of wound neovascularization: application in microsurgery research

Neovascularization or angiogenesis is an essential yet poorly understood component of the healing process. In wound healing research, there is a lack of models enabling quantitative and continuous measurements of wound neovascularization. The hairless mouse ear wound model permits quantitative measurements of wound epithelialization and neovascularization continuously throughout the healing process. On the ears of male homozygous (hr/hr) hairless mice, standardized circular full thickness dermal wounds are produced; then, using vital microscopy, these two processes are directly viewed and measured at day 0 and every third day thereafter until these are complete. This model system and its application to clinically relevant situations are reviewed.

The safety and effect of topically applied recombinant basic fibroblast growth factor on the healing of chronic pressure sores

The first randomized, blinded, placebo-controlled human trials of recombinant basic fibroblast growth factor (bFGF) for pressure sore treatment were performed. Three different concentrations of bFGF in five dosing schedules were tested for safety using hematology, serum chemistries, urinalysis, absorption, antibody formation, and signs of toxicity. Efficacy was evaluated by wound volumes, histology, and photography. No toxicity, significant serum absorption, or antibody formation occurred. In six of eight subgroups, there was a trend toward efficacy with bFGF treatment. When all subgroups were combined, comparison of the slopes of the regression curves of volume decrease over initial pressure sore volume demonstrated a greater healing effect for the bFGF-treated patients (p < 0.05). Histologically, bFGF-treated wound sections demonstrated increased fibroblasts and capillaries. More patients treated with bFGF achieved > 70% wound closure (p < 0.05). Blinded observers were able to distinguish differences in visual wound improvement between bFGF and placebo groups. These data suggest that bFGF may be effective in the treatment of chronic wounds.