Platelet-derived growth factor (BB homodimer), transforming growth factor-beta 1, and basic fibroblast growth factor in dermal wound healing. Neovessel and matrix formation and cessation of repair.

Recombinant platelet-derived growth factor (BB homodimer, rPDGF-BB), transforming growth factor beta 1 (rTGF-beta 1), and basic fibroblast growth factor (rbFGF) can accelerate healing of soft tissues. However, little information is available characterizing the components of wound matrix induced by these growth factors and the molecular mechanisms underlying accelerated repair and wound maturation. In this study, the composition, quantity, and rate of extracellular matrix deposition within growth factor-treated lapine ear excisional wounds were analyzed at different stages of healing using specific histochemical and immunohistochemical stains, coupled with image analysis techniques. Single application of optimal concentrations of each growth factor accelerated normal healing by 30% (P less than 0.0003); rPDGF-BB markedly augmented early glycosaminoglycan (GAG) and fibronectin deposition, but induced significantly greater levels of collagen later in the repair process, compared with untreated wounds rTGF-beta 1 treatment led to rapidly enhanced collagen synthesis and maturation, without increased GAG deposition. In contrast, rbFGF treatment induced a predominantly angiogenic response in wounds, with a marked increase in endothelia and neovessels (P less than 0.0001), and increased wound collagenolytic activity (P less than 0.03). rbFGF-treated wounds did not evolve into collagen-containing scars and continued to accumulate only provisional matrix well past wound closure. These results provide new evidence that growth factors influence wound repair via different mechanisms: 1) rPDGF-BB accelerates deposition of provisional wound matrix; 2) rTGF-beta 1 accelerates deposition and maturation of collagen; and 3) rbFGF induces a profound monocellular angiogenic response which may lead to a marked delay in wound maturation, and the possible loss of the normal signal(s) required to stop repair. These results suggest that specific growth factors may selectively regulate components of the repair response by differing mechanisms, offering the potential for targeted therapeutic intervention.     

Tissue repair processes in healing chronic pressure ulcers treated with recombinant platelet-derived growth factor BB.

Cellular and molecular mechanisms responsible for the observed vulnerary effects of recombinant human platelet-derived growth factor BB (rP-DGF-BB) in man have not been elucidated. In a double-blinded trial, patients having chronic pressure ulcers were treated topically with either rPDGF-BB or placebo for 28 days. To explore how rPDGF-BB may induce chronic wounds to heal, biopsies were taken from the ulcers of a cohort of 20 patients from the trial and evaluated in a blinded fashion by light microscopy for 1), fibroblast content, 2) neovessel formation, and 3), collagen deposition. Electron microscopy also was used to assess fibroblast activation and collagen deposition. Before initiation of therapy most wounds had few fibroblasts and most of those present were not activated. When mean scores for the total active treatment phase (days 8, 15, and 29) for rPDGF-BB-treated ulcers were compared with the scores for placebo-treated ulcers, fibroblast content was significantly higher for the rPDGF-BB-treated ulcers (P = 0.03, Kruskal-Wallis test). More significant differences in fibroblast and neovessel content were observed when six nonhealing wounds were eliminated from the analysis (three placebo, three treatment). Thus, in all healing wounds, rPDGF-BB therapy significantly increased fibroblast (P = 0.0007) and neovessel (P = 0.02) content. These results were correlated with increased collagen fibrillogenesis by fibroblasts from healing rPDGF-BB-treated wounds, as assessed by intracellular procollagen type I immunostaining, and by electron microscopy, and were concordant with clinical measurements (eg, area of ulcer opening and ulcer volume) which showed greater healing in rPDGF-BB-treated wounds. These results suggest induction of fibroblast proliferation and differentiation is one mechanism by which rPDGF-BB can accelerate wound healing and that rPDGF-BB can augment healing responses within a majority of, but not all, nonhealing chronic pressure ulcers in man.     

Placenta growth factor in diabetic wound healing: altered expression and therapeutic potential

Reduced microcirculation and diminished expression of growth factors contribute to wound healing impairment in diabetes. Placenta growth factor (PlGF), an angiogenic mediator promoting pathophysiological neovascularization, is expressed during cutaneous wound healing and improves wound closure by enhancing angiogenesis. By using streptozotocin-induced diabetic mice, we here demonstrate that PlGF induction is strongly reduced in diabetic wounds. Diabetic transgenic mice overexpressing PlGF in the skin displayed accelerated wound closure compared with diabetic wild-type littermates. Moreover, diabetic wound treatment with an adenovirus vector expressing the human PlGF gene (AdCMV.PlGF) significantly accelerated the healing process compared with wounds treated with a control vector. The analysis of treated wounds showed that PlGF gene transfer improved granulation tissue formation, maturation, and vascularization, as well as monocytes/macrophages local recruitment. Platelet-derived growth factor, fibroblast growth factor-2, and vascular endothelial growth factor mRNA levels were increased in AdCMV.PlGF-treated wounds, possibly enhancing PlGF-mediated effects. Finally, PlGF treatment stimulated cultured dermal fibroblast migration, pointing to a direct role of PlGF in accelerating granulation tissue maturation. In conclusion, our data indicate that reduced PlGF expression contributes to impaired wound healing in diabetes and that PlGF gene transfer to diabetic wounds exerts therapeutic activity by promoting different aspects of the repair process.     

Recombinant Hepatocyte Growth Factor Accelerates Cutaneous Wound Healing in a Diabetic Mouse Model

We examined effects of recombinant hepatocyte growth factor (HGF) on cutaneous wound healing, using a full-thickness cutaneous excision model in diabetic mice. Topical administration of HGF, as well as basic fibroblast growth factor (bFGF), promoted the rate of wound closure and re-epithelialization. Both HGF and bFGF enhanced expansion of the granulation tissue and stimulated neovascularization on day 7 postwounding, wherein the increase in microvessel density in HGF-treated wounds was higher than that in bFGF-treated wounds. Matrix metalloproteinases (MMP-2 and MMP-9) activities involved in cell migration, angiogenesis, and extracellular matrix (ECM) remodeling, were enhanced by HGF-treatment on day 7. On day 28 postwounding (later stages of wound healing), granulation tissue in bFGF-treated wounds remained to a greater extent than that seen in saline- and HGF-treated wounds. Likewise, bFGF- but not HGF-treatment stimulated DNA synthesis of fibroblasts in granulation tissue, suggesting that HGF stimulates wound healing with lesser degree of susceptibility to cutaneous scarring. We propose that supplement of HGF may be a potential therapeutic approach for treatment of cutaneous ulcer.     

Recombinant hepatocyte growth factor accelerates cutaneous wound healing in a diabetic mouse model

We examined effects of recombinant hepatocyte growth factor (HGF) on cutaneous wound healing, using a full-thickness cutaneous excision model in diabetic mice. Topical administration of HGF, as well as basic fibroblast growth factor (bFGF), promoted the rate of wound closure and re-epithelialization. Both HGF and bFGF enhanced expansion of the granulation tissue and stimulated neovascularization on day 7 postwounding, wherein the increase in microvessel density in HGF-treated wounds was higher than that in bFGF-treated wounds. Matrix metalloproteinases (MMP-2 and MMP-9) activities involved in cell migration, angiogenesis, and extracellular matrix (ECM) remodeling, were enhanced by HGF-treatment on day 7. On day 28 postwounding (later stages of wound healing), granulation tissue in bFGF-treated wounds remained to a greater extent than that seen in saline- and HGF-treated wounds. Likewise, bFGF- but not HGF-treatment stimulated DNA synthesis of fibroblasts in granulation tissue, suggesting that HGF stimulates wound healing with lesser degree of susceptibility to cutaneous scarring. We propose that supplement of HGF may be a potential therapeutic approach for treatment of cutaneous ulcer.     

深Ⅱ度烫伤创面早期应用重组人表皮生长因子后表皮生长因子受体的表达

背景：有研究表明重组人表皮生长因子能促进烧伤创面愈合,内源性表皮生长因子通过与表皮生长因子受体结合发挥生物学效应。 目的：观察局部应用重组人表皮生长因子对大鼠烫伤创面表皮生长因子受体的影响,分析其促进创面愈合的可能机制。 方法：制备Wistar大鼠背部深Ⅱ度烫伤模型,分为2组,对照组于创面喷洒生理盐水,实验组喷洒重组人表皮生长因子。烫伤后0,1,3,5,7,10,14,21 d取创面组织,采用Western blot检测表皮生长因子受体蛋白表达,并测定两组大鼠创面愈合率。 结果与结论：烫伤后7-21 d 实验组创面愈合率高于对照组(P < 0.05)。两组表皮生长因子受体蛋白表达在1 d明显降低(P < 0.05),随后又升高,7 d达峰值且对照组比实验组高(P < 0.05);峰值过后,对照组逐渐下降,21 d接近烫伤前水平,实验组迅速下降,14 d达谷值,随后上升,21 d接近烫伤前水平,两组差异有显著性意义(P < 0.05)。说明早期局部应用重组人表皮生长因子可影响表皮生长因子受体的表达规律,并显著促进大鼠深Ⅱ度烫伤创面愈合。     

Mesenchymal stem cells enhance wound healing through differentiation and angiogenesis

Although chronic wounds are common, treatment for these disabling conditions remains limited and largely ineffective. In this study, we examined the benefit of bone marrow-derived mesenchymal stem cells (BM-MSCs) in wound healing. Using an excisional wound splinting model, we showed that injection around the wound and application to the wound bed of green fluorescence protein (GFP)(+) allogeneic BM-MSCs significantly enhanced wound healing in normal and diabetic mice compared with that of allogeneic neonatal dermal fibroblasts or vehicle control medium. Fluorescence-activated cell sorting analysis of cells derived from the wound for GFP-expressing BM-MSCs indicated engraftments of 27% at 7 days, 7.6% at 14 days, and 2.5% at 28 days of total BM-MSCs administered. BM-MSC-treated wounds exhibited significantly accelerated wound closure, with increased re-epithelialization, cellularity, and angiogenesis. Notably, BM-MSCs, but not CD34(+) bone marrow cells in the wound, expressed the keratinocyte-specific protein keratin and formed glandular structures, suggesting a direct contribution of BM-MSCs to cutaneous regeneration. Moreover, BM-MSC-conditioned medium promoted endothelial cell tube formation. Real-time polymerase chain reaction and Western blot analysis revealed high levels of vascular endothelial growth factor and angiopoietin-1 in BM-MSCs and significantly greater amounts of the proteins in BM-MSC-treated wounds. Thus, our data suggest that BM-MSCs promote wound healing through differentiation and release of proangiogenic factors. Disclosure of potential conflicts of interest is found at the end of this article.     

A new mouse model for wound healing in hemophilia A

Purpose: To establish a new mouse model for wound healing studies on hemophilia A. Methods: Total 54 male mice with different genotypes including wild-type nude mice, heterozygous mice (FVIII^-/-/Nu) and FVIII deficient mice (FVIII^-/-) were generated and verified by PCR. Mice were subjected to wound healing research by making a 5 mm-thickness wound on mice skin and applying recombinant human epidermal growth factor (EGF, 10 μg/g) ointment, FVIII ointment (30 IU) or the ointment base to heal the wounds. Furthermore, keratinocytes were isolated from these newborn mice and subjected to migration assay by stimulation of EGF (ng/ml), insulin (10 μM) or vehicle. Results: A new hemophilic mouse model (FVIII^-/-/Nu) was constructed successfully after genotyping verified by PCR. Compared to FVIII^-/- mice, FVIII^-/-/Nu and Nu mice showed greater degree of wound contraction and loss of the crust. Topical treatment with EGF exhibited faster wound healing than FVIII and ointment base. Insulin treatment showed more increased migration distance than treated with EGF or vehicle. FVIII^-/-/Nu mice showed greater migration than FVIII^-/- and Nu mice. Conclusions: A new mouse model (FVIII^-/-/Nu) for wound healing in hemophilia A was constructed, and topical treatment of insulin may be a better therapy than EGF for healing wounds in hemophilia A.     

Accelerated healing of ulcer wounds in the rabbit ear by recombinant human transforming growth factor-beta 1

A dermal ulcer wound-healing model was established in rabbit ear to examine the effects of recombinant human transforming growth factor-beta 1 (rhTGF-beta 1) in wound healing. Histomorphometric examination of the wounds indicate a biphasic healing response 7 days after a single application of rhTGF-beta 1 at the time of wounding. Statistically significant healing occurred at 5-100 ng but not at higher doses of 500 or 1000 ng rhTGF-beta 1/wound. Enhanced collagen synthesis as determined by [3H]proline incorporation occurred at 15 and 25 ng and was significantly depressed at 500 ng rhTGF-beta 1/wound. Multiple doses of 100 ng rhTGF-beta 1 applied to the wound at the time of wounding and for 3 days after wounding provided results comparable to the single application of growth factor. Delaying treatment 24 hr after wounding did not enhance wound healing compared with vehicle. Our findings suggest that rhTGF-beta 1 can be a valuable growth factor to improve the healing of ulcer wounds.     

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

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

Adenosine promotes wound healing and mediates angiogenesis in response to tissue injury via occupancy of A(2A) receptors

Recent evidence indicates that topical application of adenosine A(2A) receptor agonists, unlike growth factors, increases the rate at which wounds close in normal animals and promotes wound healing in diabetic animals as well as growth factors, yet neither the specific adenosine receptor involved nor the mechanism(s) by which adenosine receptor occupancy promotes wound healing have been fully established. To determine which adenosine receptor is involved and whether adenosine receptor-mediated stimulation of angiogenesis plays a role in promotion of wound closure we compared the effect of topical application of the adenosine receptor agonist CGS-21680 (2-p-[2-carboxyethyl]phenethyl-amino-5'-N-ethylcarboxamido-adenosine) on wound closure and angiogenesis in adenosine A(2A) receptor knockout mice and their wild-type littermates. There was no change in the rate of wound closure in the A(2A) receptor knockout mice compared to their wild-type littermates although granulation tissue formation was nonhomogeneous and there seemed to be greater inflammation at the base of the wound. Topical application of CGS-21680 increased the rate of wound closure and increased the number of microvessels in the wounds of wild-type mice but did not affect the rate of wound closure in A(2A) receptor knockout mice. Similarly, in a model of internal trauma and repair (murine air pouch model), endogenously produced adenosine released into areas of internal tissue injury stimulates angiogenesis because there was a marked reduction in blood vessels in the walls of healing air pouches of A(2A) receptor knockout mice compared to their wild-type controls. Inflammatory vascular leakage and leukocyte accumulation in the inflamed air pouch were similarly reduced in the A(2A) receptor knockout mice reflecting the reduced vascularity. Thus, targeting the adenosine A(2A) receptor is a novel approach to promoting wound healing and angiogenesis in normal individuals and those suffering from chronic wounds.     

Nicotine accelerates angiogenesis and wound healing in genetically diabetic mice

Recently, we have discovered an endogenous cholinergic pathway for angiogenesis mediated by endothelial nicotinic acetylcholine receptors (nAChRs). Since angiogenesis plays a major role in wound repair, we hypothesized that activation of nAChRs with nicotine would accelerate wound healing in a murine excisional wound model. In genetically diabetic and control mice full-thickness skin wounds (0.8 cm) were created on the dorsum and topically treated over 7 days with either vehicle (phosphate-buffered saline, PBS) or nicotine (10(-8) mol/L, 10(-9) mol/L; each, n = 5). Wound size was measured over 14 days followed by resection, histological analysis, and quantitation of vascularity. In diabetic animals an agonist (epibatidine, 10(-10) mol/L) or antagonist (hexamethonium, 10(-4) mol/L) of nAChRs as well as the positive control basic fibroblast growth factor (bFGF, 25 microg/kg) were also tested. To further study the role of endothelial nAChRs in angiogenesis, we used an ex vivo vascular explant model. In diabetic mice wound healing was markedly impaired. Nicotine significantly accelerated wound healing as assessed by closure rate and histological score. The effects of nicotine were equal to bFGF and were mimicked by epibatidine and blocked by hexamethonium. Histomorphometry revealed increased neovascularization in animals treated with nicotine. Furthermore, capillary-like sprouting from vascular explants was significantly enhanced by nicotine. In conclusion, agonist-induced stimulation of nAChRs accelerates wound healing in diabetic mice by promoting angiogenesis. We have discovered a cholinergic pathway for angiogenesis that is involved in wound healing, and which is a potential target for therapeutic angiogenesis.     

Fibrin-based scaffold incorporating VEGF- and bFGF-loaded nanoparticles stimulates wound healing in diabetic mice

Diabetic skin ulcers are difficult to heal spontaneously due to the reduced levels and activity of endogenous growth factors. Recombinant human vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) are known to stimulate cell proliferation and accelerate wound healing. Direct delivery of VEGF and bFGF at the wound site in a sustained and controllable way without loss of bioactivity would enhance their biological effects. The aim of this study was to develop a poly(ether)urethane–polydimethylsiloxane/fibrin-based scaffold containing poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with VEGF and bFGF (scaffold/GF-loaded NPs) and to evaluate its wound healing properties in genetically diabetic mice (db/db). The scaffold application on full-thickness dorsal skin wounds significantly accelerated wound closure at day 15 compared to scaffolds without growth factors (control scaffold) or containing unloaded PLGA nanoparticles (scaffold/unloaded NPs). However, the closure rate was similar to that observed in mice treated with scaffolds containing free VEGF and bFGF (scaffold/GFs). Both scaffolds containing growth factors induced complete re-epithelialization, with enhanced granulation tissue formation/maturity and collagen deposition compared to the other groups, as revealed by histological analysis. The ability of the scaffold/GF-loaded NPs to promote wound healing in a diabetic mouse model suggests its potential use as a dressing in patients with diabetic foot ulcers.     

Effect of chitosan film containing basic fibroblast growth factor on wound healing in genetically diabetic mice

Basic fibroblast growth factor (bFGF) has been shown to stimulate wound healing. However, consistent delivery of bFGF has been problematic. We studied the stability of bFGF incorporated into a chitosan film as a delivery vehicle for providing sustained release of bFGF. The therapeutic effect of this system on wound healing in genetically diabetic mice was determined as a model for treating clinically impaired wound healing. A chitosan film was prepared by freeze-drying hydroxypropylchitosan (a water-soluble derivative of chitosan) acetate buffer solution. Growth factor was incorporated into films before drying by mixing bFGF solution with the hydroxypropylchitosan solution. bFGF activity remained stable for 21 days at 5 degrees C, and 86.2% of activity remained with storage at 25 degrees C. Full-thickness wounds were created on the backs of diabetic mice, and chitosan film or bFGF-chitosan film was applied to the wound. The wound was smaller in after 5 days in both groups, but the wound was smaller on day 20 only in the bFGF-chitosan group. Proliferation of fibroblasts and an increase in the number of capillaries were observed in both groups, but granulation tissue was more abundant in the bFGF-chitosan group. These results suggest that chitosan itself facilitates wound repair and that bFGF incorporated into chitosan film is a stabile delivery vehicle for accelerating wound healing.     

Growth factors in porcine full and partial thickness burn repair. Differing targets and effects of keratinocyte growth factor, platelet-derived growth factor-BB, epidermal growth factor, and neu differentiation factor.

The topical application of recombinant growth factors such as epidermal growth factor, platelet-derived growth factor-BB homodimer (rPDGF-BB), keratinocyte growth factor (rKGF), and neu differentiation factor has resulted in significant acceleration of healing in several animal models of wound repair. In this study, we established highly reproducible and quantifiable full and deep partial thickness porcine burn models in which burns were escharectomized 4 or 5 days postburn and covered with an occlusive dressing to replicate the standard treatment in human burn patients. We then applied these growth factors to assess their efficacy on several parameters of wound repair: extracellular matrix and granulation tissue production, percent reepithelialization, and new epithelial area. In full thickness burns, only rPDGF-BB and the combination of rPDGF-BB and rKGF induced significant changes in burn repair. rPDGF-BB induced marked extracellular matrix and granulation tissue production (P = 0.013) such that the burn defect was filled within several days of escharectomy, but had no effect on new epithelial area or reepithelialization. The combination of rPDGF-BB and rKGF in full thickness burns resulted in a highly significant increase in extracellular matrix and granulation tissue area (P = 0.0009) and a significant increase in new epithelial area (P = 0.007), but had no effect on reepithelialization. In deep partial thickness burns, rKGF induced the most consistent changes. Daily application of rKGF induced a highly significant increase in new epithelial area (P < 0.0001) but induced only a modest increase in reepithelialization (83.7% rKGF-treated versus 70.2% control; P = 0.016) 12 days postburn. rKGF also doubled the number of fully reepithelialized burns (P = 0.02) at 13 days postburn, at least partially because of marked stimulation of both epidermal and follicular proliferation as assessed by proliferating cell nuclear antigen expression. In situ hybridization for KGFR in porcine burns revealed strong expression of KGFR on hair follicles and basal epidermis, confirming direct rKGF action on follicular as well as epidermal keratinocytes. Although the epithelial proliferation induced by rKGF resulted in marked neoepidermal psoriasiform hyperplasia with exaggerated rete ridges and neoepidermal and follicular maturation as assessed by expression of cytokeratin 10, a marker of keratinocyte terminal differentiation was not delayed and appeared to be accelerated in some rKGF-treated burns. Recombinant epidermal growth factor induced a trend toward increased new epithelial area in deep partial thickness burns, but had no effect on reepithelialization. The recombinant neu differentiation factor-alpha 2 isoform had no significant biological effects in either full or deep partial thickness burns.(ABSTRACT TRUNCATED AT 250 WORDS)     

Accelerated Healing of Ulcer Wounds in the Rabbit Ear by Recombinant Human Transforming Growth Factor-β1

Abstract

A dermal ulcer wound-healing model was established in rabbit ear to examine the effects of recombinant human transforming growth factor-β1 (rhTGF-β 1) in wound healing. Histo-morphometric examination of the wounds indicate a biphasic healing response 7 days after a single application of rhTGF-β l at the time of wounding. Statistically significant healing occurred at 5-100 ng but not at higher doses of 500 or 1000 ng rhTGF-β l/wound. Enhanced collagen synthesis as determined by [³H] proline incorporation occurred at 15 and 25 ng and was significantly depressed at 500 ng rhTGF-β1wound. Multiple doses of 100 ng rhTGF-/3l applied to the wound at the time of wounding and for 3 days after wounding provided results comparable to the single application of growth factor. Delaying treatment 24 hr after wounding did not enhance wound healing compared with vehicle. Our findings suggest that rhTGF-β l can be a valuable growth factor to improve the healing of ulcer wounds.     

Platelet-derived growth factor-beta receptor activation is essential for fibroblast and pericyte recruitment during cutaneous wound healing

Connective tissue remodeling provides mammals with a rapid mechanism to repair wounds after injury. Inappropriate activation of this reparative process leads to scarring and fibrosis. Here, we studied the effects of platelet-derived growth factor receptor-beta blockade in vivo using the platelet-derived growth factor receptor (PDGFR)-beta inhibitor imatinib mesylate on tissue repair. After 7 days, healing of wounds was delayed with significantly reduced wound closure and concomitant reduction in myofibroblast frequency, expression of fibronectin ED-A, and collagen type I. Using a collagen type I transgenic reporter mouse, we showed that inhibiting PDGFR-beta activation restricted the distribution of collagen-synthesizing cells to wound margins and dramatically reduced cell proliferation in vivo. By 14 days, treated wounds were fully closed. Blocking PDGFR-beta signaling did not prevent the differentiation of myofibroblasts in vitro but potently inhibited fibroblast proliferation and migration. In addition, PDGFR-beta inhibition in vivo was accompanied by abnormal microvascular morphogenesis reminiscent of that observed in PDGFR-beta-/- mice with significantly reduced immunostaining of the pericyte marker NG2. Imatinib treatment also inhibited pericyte proliferation and migration in vitro. This study highlights the significance of PDGFR-beta signaling for the recruitment, proliferation, and functional activities of fibro-blasts and pericytes during the early phases of wound healing.     

Fibrosin: a novel lymphokine in wound healing.

Several growth factors are actively synthesized during wound repair and function to stimulate different cell types involved in the process of healing. Fibrosin is a novel fibrogenic lymphokine that stimulates several biological activities that relate to in vivo scarring. To investigate the role of fibrosin, we used "punch biopsy" and linear wounding procedures in a murine model of wound healing. Histological examination showed that recombinant fibrosin stimulated epithelialization of wounds and accelerated healing of both punch biopsy and linear wounds. Fibrosin enhanced healing of linear wounds by reducing the time for healing by approximately 30-40%. From our data we estimated the healing time of control wounds to be 22-24 days; wounds treated with fibrosin appeared to heal in 14-16 days. Our observations suggest that fibrosin enhances wound healing and may be involved in accelerating epithelialization, collagen matrix formation, and also remodeling of the extracellular matrix in vivo. Thus fibrosin may function during different phases of wound healing and act as a potent inducer of scar formation and wound healing. This finding may have direct clinical applications.     

Effects of granulocyte-macrophage colony-stimulating factor on wound contraction

The effect of topical recombinant murine and human GM-CSF, 1 or 10 µg/cm² for one to ten days, on the contraction and healing of acute and chronic granulating wounds infected withEscherichia coli was studied in Sprague-Dawley rats. Bacterial contamination of wounds produced significant inhibition of wound contraction. Application of GM-CSF at either dose level to infected wounds markedly increased the rate of wound closure compared to the rate in infected untreated controls. Ten days treatment was found to be more effective than a single application. An advanced stage of wound healing was observed at ten days in the GM-CSF-treated rats compared with controls. Bacterial counts decreased in the GM-CSF-treated wounds which may suggest bactericidal activity. Topical treatment with GM-CSF was shown to effectively inhibit the retardation of wound closure produced by bacterial contamination and may therefore be useful in the management of patients with infected wounds.