Basic fibroblast growth factor accelerates wound healing in chronically ischaemic tissue

The bFGF Can Improve Angiogenesis in Oral Mucosa and Accelerate Wound Healing

Background

The role of the basic fibroblast growth factor (bFGF) has well known in the angiogenesis and ulcer healing. In this study, we aimed to evaluate the effects of bFGF on tissue repair in a rat oral mucosal wound.

Methods

Musosal wound induced on the lip mucosa of rats and bFGF was injected along the edge of the mucosal defect immediately after surgery. The tissues were collected on days 3, 7 and 14 after the wound induction. The micro vessel density (MVD) and CD34 expression were done by histochemical studies.

Results

The bFGF significantly accelerated granulation tissue formation and MVD was increased three days after ulcer induction but decreased 14 days after surgery. The MVD was significantly higher in the bFGF-treated group. The wound area was decreased in all groups time-dependently and a statistically significant difference (p value?) was observed between the bFGF-treated group and untreated group. The wound area was smaller in the bFGF-treated group compared to the untreated group.

Conclusions

Our data demonstrated that bFGF can accelerated and facilitated wound healing.

Modelling optimal delivery of bFGF to chronic wounds using ODEs

In this paper, we present an ordinary differential equation model depicting the interactions of basic fibroblast growth factor (bFGF) and its binding agents in a chronic wound. The delivery of bFGF was treated as a control variable and is coupled to an objective functional. By optimising the objective functional with respect to the control, predictions for optimal delivery rates of bFGF are proposed. The optimal control is then validated by comparing the cost of the objective functional for the optimal delivery rate and several alternative delivery rates. This paper addresses two objectives of effective drug delivery to chronic wounds. The first is to provide insight for the priority of delivering bFGF: to minimise the quantity of bFGF, or to optimise the distribution of bound bFGF. For effective concentrations of bound bFGF, the optimisation of bound bFGF must be prioritised over the minimisation of bFGF delivered. The second objective is to comment on the effect of the proteolytic environment within the wound, with the concentration of bound bFGF starting to decrease late in the treatment period for highly proteolytic environments. This will lead to long term complications with wound closure after the treatment has been completed. Also, it was found that for highly proteolytic environments, the cost of delivering bFGF increased. The need for optimal drug delivery is made apparent by the burden of chronic wounds on the medical industry across the developed world.

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.

Fibronectin matrix mimetics promote full-thickness wound repair in diabetic mice

During tissue repair, fibronectin is converted from a soluble, inactive form into biologically active extracellular matrix (ECM) fibrils through a cell-dependent process. ECM fibronectin promotes numerous cell processes that are critical to tissue repair and regulates the assembly of other proteins into the matrix. Nonhealing wounds show reduced levels of ECM fibronectin. To functionally mimic ECM fibronectin, a series of fibronectin matrix mimetics was developed by directly coupling the matricryptic, heparin-binding fragment of the first type III repeat of fibronectin (FNIII1H) to various sequences from the integrin-binding domain (FNIII8-10). The recombinant proteins were produced as glutathione-S-transferase (GST)-tagged fusion proteins for ease of production and purification. Full-thickness, excisional wounds were produced in genetically diabetic mice, and fibronectin matrix mimetics were applied directly to the wounds. A significant enhancement of wound closure was observed by day 9 in response to GST/III1H,8-10 versus GST-treated controls (73.9%±4.1% vs. 58.1%±4.7% closure, respectively). Two weeks after injury, fibronectin matrix mimetic-treated wounds had developed a multi-layered epithelium that completely covered the wound space. Furthermore, significant increases in granulation tissue thickness were observed in response to treatment with GST/III1H,8-10 (4.05±0.93-fold), GST/III1H,8,10 (2.91±0.49-fold), or GST/III1H,8(RGD) (3.55±0.59-fold) compared with GST controls, and was accompanied by dense collagen deposition, the presence of myofibroblasts, and functional vasculature. Thus, the recombinant fibronectin matrix analogs normalized the impairment in repair observed in this chronic wound model and may provide a new approach to accelerate the healing of diabetic wounds.

A RHAMM mimetic peptide blocks hyaluronan signaling and reduces inflammation and fibrogenesis in excisional skin wounds

Hyaluronan is activated by fragmentation and controls inflammation and fibroplasia during wound repair and diseases (eg, cancer). Hyaluronan-binding peptides were identified that modify fibrogenesis during skin wound repair. Peptides were selected from 7- to 15mer phage display libraries by panning with hyaluronan-Sepharose beads and assayed for their ability to block fibroblast migration in response to hyaluronan oligosaccharides (10 kDa). A 15mer peptide (P15-1), with homology to receptor for hyaluronan mediated motility (RHAMM) hyaluronan binding sequences, was the most effective inhibitor. P15-1 bound to 10-kDa hyaluronan with an affinity of K(d) = 10(-7) and appeared to specifically mimic RHAMM since it significantly reduced binding of hyaluronan oligosaccharides to recombinant RHAMM but not to recombinant CD44 or TLR2,4, and altered wound repair in wild-type but not RHAMM(-/-) mice. One topical application of P15-1 to full-thickness excisional rat wounds significantly reduced wound macrophage number, fibroblast number, and blood vessel density compared to scrambled, negative control peptides. Wound collagen 1, transforming growth factor β-1, and α-smooth muscle actin were reduced, whereas tenascin C was increased, suggesting that P15-1 promoted a form of scarless healing. Signaling/microarray analyses showed that P15-1 blocks RHAMM-regulated focal adhesion kinase pathways in fibroblasts. These results identify a new class of reagents that attenuate proinflammatory, fibrotic repair by blocking hyaluronan oligosaccharide signaling.

Surgical implantation of a bioengineered internal anal sphincter

PURPOSE

Fecal incontinence is a common disorder that can have devastating social and psychologic consequences. However, there are no long-term ideal solutions for such patients. Although loss of continence is multifactorial, the integrity of the internal anal sphincter (IAS) has particular significance. We previously described the development of 3-dimensional bioengineered constructs using isolated smooth muscle tissue from donor C57BL/6 IAS. We hypothesized that the bioengineered ring constructs would retain cellular viability and promote neovascularization upon implantation into a recipient mouse.

METHODS

Internal anal sphincter ring constructs were surgically implanted into the subcutaneous tissue of syngeneic C57BL/6 mice and treated with either fibroblastic growth factor 2 (0.26 microg daily) or saline controls using a microosmotic pump. Internal anal sphincter constructs were harvested after 25 days (range, 23-26 days) and assessed morphologically and for tissue viability.

RESULT

Gross morphology showed that there was no rejection. Rings showed muscle attachment to the back of the mouse with no sign of inflammation. Fibroblastic growth factor 2 infusion resulted in a significantly improved histologic score and muscle viability compared with the control group.

CONCLUSIONS

Three-dimensional bioengineered IAS rings can be successfully implanted into the subcutaneous tissue of recipient mice. The addition of fibroblastic growth factor 2 led to improved muscle viability, vascularity, and survival. This approach may become a feasible option for patients with fecal incontinence.

Tgf-beta antisense therapy increases angiogenic potential in human keratinocytes in vitro

BACKGROUND

Transforming growth factor-beta (TGF-beta) has been identified as an important component of wound healing. Recent developments in molecular therapy offer exciting prospects for the modulation of wound healing, specifically those targeting TGF-beta. The purpose of this study was to analyze the effect of TGF-beta targeting on the expression of angiogenic vascular endothelial growth factor (VEGF), a key regulator of angiogenesis, and in vitro angiogenic activity.

METHODS

Expression of angiogenic VEGF in tissue samples from chronic dermal wounds was investigated by immunohistochemistry. The effect of TGF-beta targeting using antisense oligonucleotides on the expression of VEGF was analyzed by ELISA and RT-PCR in cultured human keratinocytes. Human endothelial cells (EC) were grown in conditioned medium produced from the treated keratinocytes. EC migration was measured using a modified Boyden chamber, EC tube formation was analyzed under the light microscope.

RESULTS

Immunohistochemical investigation demonstrated a decreased expression of VEGF protein in tissue samples from chronic dermal wounds compared to normal human skin. Antisense TGF-beta oligonucleotide treatment upregulated VEGF secretion in vitro. Addition of conditioned medium from TGF-beta antisense-treated keratinocytes resulted in an increase of endothelial cell migration and tube formation.

CONCLUSIONS

Our results demonstrate that TGF-beta antisense oligonucleotide technology may be a potential therapeutic option for stimulation of angiogenesis in chronic wounds.

Effect of Polyvinylpyrrolidone-Iodine Liposomal Hydrogel on Wound Microcirculation in SKH1-hr Hairless Mice

AIM

Polyvinylpyrrolidone-iodine liposomal hydrogel (PVP-ILH) is a hydrogel formulation based on polyvinylpyrrolidone-iodine (PVP-I) and liposomes. The beneficial effects of PVP-ILH on wound healing have been previously shown. The aim of this study was to investigate the effects of topically applied PVP-ILH on wound microcirculation.

MATERIALS AND METHODS

Experiments were performed on wounds in male SKH1-hr hairless mice (n = 48). Mice were randomized into five treatment groups: mice treated with polyacrylic acid (PAA) and PAA 1:10 as well as PVP-ILH and PVP-ILH 1:10. Mice treated with sodium chloride served as control. Immediately as well as 3, 7, and 14 days after wounding, intravital fluorescent microscopy (IFM) was performed to determine wound surface area and standard microcirculatory parameters.

RESULTS

Topically administered PVP-ILH reduced wound size significantly faster compared to controls. Standard microcirculatory parameters, e.g. functional capillary density (FCD) and plasma leakage, showed no differences. FCD increases in all groups after wound creation. Using PVP-ILH, a trend towards higher FCD was observed.

CONCLUSION

The wound model in hairless mice in combination with IFM is suitable to qualitatively assess wound microcirculation over a period of 2 weeks even after topical application of pigmented ointments. PVP-ILH showed a positive effect on dermal wound healing and wound microcirculation.

Emerging new drugs for wound repair

Every year, millions of people experience burns, suffer from nonhealing wounds, or have acute wounds that become complicated by infection, dehiscence or problematic scarring. Effective wound treatment requires carefully considered interventions often requiring multiple clinic or hospital visits. The resulting costs of wound care are staggering, and more efficacious and cost-effective therapies are needed to decrease this burden. Unfortunately, the expenses and difficulties encountered in performing clinical trials have led to a relatively slow growth of new treatment options for the wound management. Research efforts attempting to examine wound pathophysiology have been hampered by the lack of an adequate chronic wound healing model, and the complexity of the wound healing cascade has limited attempts at pharmacological modification. As such, currently available wound healing therapies are only partially effective. Therefore, many new therapies are emerging that target various aspects of wound repair and the promise of new therapeutic interventions is on the immediate horizon.

Platelet gel for healing cutaneous chronic wounds

Wound healing is a specific host immune response for restoration of tissue integrity. Experimental studies demonstrated an alteration of growth factors activity due to their reduced synthesis, increased degradation and inactivation. In wound healing platelets play an essential role since they are rich of alpha-granules growth factors (platelet derived growth factor--PDGF; transforming growth factor-beta--TGF-beta; vascular endothelial growth factor--VEGF). Topical use of platelet gel (PG), hemocomponent obtained from mix of activated platelets and cryoprecipitate, gives the exogenous and in situ adding of growth factors (GF). The hemocomponents are of autologous or homologous origin. We performed a technique based on: multicomponent apheretic procedure to obtain plasma rich platelet and cryoprecipitate; manual processing in an open system, in sterile environment, for gel activation. Every step of the gel synthesis was checked by a quality control programme. The therapeutic protocol consists of the once-weekly application of PG. Progressive reduction of the wound size, granulation tissue forming, wound bed detersion, regression and absence of infective processes were considered for evaluating clinical response to hemotherapy. 24 patients were enrolled. They had single or multiple cutaneous ulcers with different ethiopathogenesis. Only 3 patients could perform autologous withdrawal; in the others homologous hemocomponent were used, always considering suitability and traceability criteria for transfusional use of blood. Complete response was observed in 9 patients, 2 were subjected to cutaneous graft, 4 stopped treatment, 9 had partial response and are still receiving the treatment. In each case granulation tissue forming increased following to the first PG applications, while complete re-epithelization was obtained later. Pain was reduced in every treated patient. Topical haemotherapy with PG may be considered as an adjuvant treatment of a multidisciplinary process, useful to enhance therapy of cutaneous ulcers.

Cytokines and wound healing: the role of cytokine and anticytokine therapy in the repair response

Wound healing is an integrated and complex process involving a large number of regulatory molecules, including proinflammatory cytokines and growth factors, and an orchestrated tissue response. Dysregulation in cytokine or growth factor expression dramatically alters the normal wound healing process, and blocking the inappropriate production of specific proinflammatory cytokines or supplementing the milieu with increased quantities of growth factors has demonstrated the central role played by these mediators. Both protein-based and DNA-based (gene transfer) therapies are currently under clinical development as tools to improve the healing process. Although there has been some success with these approaches in both experimental models and in patients, only through a better understanding of the complexity and diversity of the wound healing process, as well as an improved comprehension of the time-dependent and concentration-dependent responses to individual proinflammatory cytokines or growth factors, will further development in the therapeutic treatment of healing wounds be attained.

Accelerating effects of basic fibroblast growth factor on wound healing of rat palatal mucosa

PURPOSE

In this study, basic fibroblast growth factor (bFGF) was examined for its ability to accelerate tissue repair in a rat oral mucosal wound.

MATERIALS AND METHODS

A 4-mm mucosal defect was surgically made to the depth of the periosteum in a rat palate. bFGF was injected along the edge of the mucosal defect immediately after surgery. A control group received only phosphate-buffered saline vehicle.

RESULTS

bFGF significantly accelerated granular tissue formation and reepithelialization. From the histologic analysis, the bFGF-treated group showed relatively faster collagen maturation. Starting 3 days after surgery, fibroblast growth factor receptor 1 (FGFR1)-positive cells appeared in the granular and spinous cell layers of the reepithelializing mucosa in the bFGF-treated group, whereas almost none was observed in the intact oral mucosa. By day 5, FGFR1-positive cells were seen below the stratum corneum, even in the control group. However, the number and intensity of FGFR1-positive cells in the bFGF-treated group were greater than in the control group. Results of immunostaining against proliferating cell nuclear antigen showed that bFGF stimulated cell proliferation of the basal cell layer in the regenerating epithelium. At a higher dose of bFGF, proliferating cell nuclear antigen-positive cells were also observed in the submucosal connective tissue.

CONCLUSION

By the induction of its ligand protein concomitant with direct effects such as increased granular tissue formation and reepithelialization, a single topical application of bFGF facilitated wound healing in rat oral mucosa. The results of this study support the consideration for bFGF application for patients with impaired healing of oral mucosal injury.

Influence of platelet-derived growth factor on microcirculation during normal and impaired wound healing

The aim of the current study was to evaluate the influence of platelet-derived growth factor (PDGF) on skin microcirculation during normal and impaired wound healing. Secondary healing wounds were created on the ears of hairless mice and treated once with 3 microg of PDGF-BB immediately after wound creation. Intravital fluorescence microscopy was used to quantify reepithelialization, revascularization, vessel diameters, vascular permeability, and leukocyte-endothelium interactions up to 24 days after wound creation. Microvascular perfusion was assessed by laser Doppler flowmetry. Wound healing was studied in normal (n = 15) and ischemic skin tissue (n = 15) as well as in mice (n = 17) rendered hyperglycemic by an intravenous injection of streptozotocin 7 days prior to wound creation. Treatment with PDGF accelerated reepithelialization and reduced the time for complete wound closure in ischemic skin from 14.9 +/- 2.5 (control) to 12.3 +/- 1.8 days (p < 0.03), and in hyperglycemic animals from 15.0 +/- 2.4 (control) to 12.0 +/- 3.0 days (p < 0.04). Revascularization of these wounds was also significantly enhanced after PDFG application. No other parameters were influenced by the treatment. Normal wound healing was not affected. This study confirms the positive influence of PDGF on wound healing under pathophysiological conditions. The effects in this model seem to be primarily due to the mitogenic potency of PDGF on keratinocytes and endothelial cells. A significant effect on leukocyte activation during the inflammatory process was not observed.

Basic fibroblast growth factor and epidermal growth factor reverse impaired ulcer healing of the rabbit oral mucosa

BACKGROUND

The therapies for refractory ulcers on the oral mucosa are symptomatic and very unsatisfactory. We hypothesized that application of growth factors might be able to achieve successful remission of the lesion. We evaluated the effects of systemic administration and topical application of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) on impaired wound healing of ulcers in the rabbit gingiva.

METHODS

Almost uniform round ulcers could be created on the gingiva of the rabbits by chemical injury with acetic acid. When the submandibular glands were removed or i.v. injection of cisplatin (CDDP) and peplomycin sulfate was performed before ulcer formation, healing of the ulcers took longer than in untreated rabbits. To ascertain whether or not human EGF and bFGF affect rabbit cells, we first examined the effects of EGF and bFGF on the proliferation of the cells derived from rabbit gingiva. We then applied EGF or bFGF in these impaired healing models.

RESULTS

EGF and bFGF promoted proliferation of the fibroblasts, and EGF also promoted proliferation of the keratinocytes isolated from gingival tissue of rabbits in vitro. Systemic injections of EGF and bFGF in rabbits, which had their submandibular glands removed, and topical application of bFGF accelerated healing of ulcers created in rabbits injected with CDDP and peplomycin sulfate. The ability of bFGF to promote the healing of ulcers was much greater than that of EGF.

CONCLUSION

Basic FGF may be effective for refractory oral mucosal lesions.

The effect of vascular endothelial growth factor on the healing of ischaemic skin wounds

The effect of exogenous vascular endothelium growth factor (VEGF) on wound healing in an ischaemic skin flap model was evaluated in this study. Seventy-two Sprague-Dawley rats were used. Normal incisional wound and H-shaped double flaps were used as the wound models. The study was divided into two parts. In Part I, VEGF protein levels were determined from the incisional and H-shaped ischaemic wounds at 12 and 24 h, postoperatively. In Part II, tensile strength and immunohistochemical stains were examined to determine the level of microvessel density (MVD) at 1 and 2 weeks, postoperatively in simple incisional wounds, ischaemic wounds, and ischaemic wounds following 1 ml (1 microg/ml) exogenous VEGF injections into the subcutaneous tissue. The results showed a significantly higher level of VEGF protein in the ischaemic wounds than the incisional wounds. Tensile strength was statistically higher in the incisional wound group and in the ischaemic flap wounds with VEGF treatment compared to the ischaemic flaps with no treatment at 1 week, postoperatively (p>0.05). MVD data indicated that ischaemic wound repair with VEGF treatment had significantly higher MVD than the normal incisional wounds and ischaemic wounds without treatment. We conclude that exogenous application of VEGF can increase early angiogenesis and tensile strength in the ischaemic wound.

An extract of the root of Lithospermun erythrorhison accelerates wound healing in diabetic mice

Many people suffer from intractable bedsores, which sometimes develop because of chronic metabolic failure in patients. An extract of the root of Lithospermun erythrorhison (SK) has been reported to have an effect on wound healing. However, the effects of SK have not been studied in chronic wounds, such as bedsores. The healing-impaired diabetic (db/db) mouse is a good model for the investigation of clinical healing therapies. Therefore, we examined whether SK accelerates wound healing in db/db mice. Full-thickness round wounds of 6-mm diameter were created on the backs of mice. After applying SK, we covered the wound with a film dressing to keep it moist. At three weeks, wound closure was complete in SK-treated mice but not in controls. Capillary vessel number and collagen synthesis increased early in wound healing in SK-treated wounds. At this time, vascular endothelial growth factor (VEGF)-positive neutrophils had infiltrated the wound and the appearance of apoptotic fibroblasts and endothelial cells in the granulation tissue was more advanced than in the controls. Where the wound was covered with epithelium, there tended to be less infiltration of VEGF-positive cells and apoptotic cells. These results suggest that the inflammatory phase was shortened, and the proliferative and maturation phases were advanced by SK. It is known that SK also has antibacterial activity. Therefore, we conclude that SK is useful for wound healing in db/db mice, and could potentially help patients with intractable bedsores.

Growth factors in the treatment of diabetic foot ulcers

BACKGROUND

Chronic foot ulceration is a major source of morbidity in diabetic patients. Despite traditional comprehensive wound management, including vascular reconstruction, there remains a cohort of patients with non-responding wounds, often resulting in amputation. These wounds may benefit from molecular manipulation of growth factors to enhance the microcirculation.

METHODS

A review of the current literature was performed using Pubmed, with secondary references obtained from key articles.

RESULTS AND CONCLUSION

There has been a generally disappointing clinical outcome from growth factor trials, although topical platelet-derived growth factor has shown significant benefit and should be considered in non-healing, well perfused ulcers after failure of conventional wound care. The modulatory role of the extracellular matrix in the cellular response to growth factors and data from regenerative-type fetal wound healing are further areas of interest. The chemical induction of microvessel formation may become a future therapeutic option.

Orthogonal polarization spectral imaging versus intravital fluorescent microscopy for microvascular studies in wounds

The aim of this study was to validate orthogonal polarization spectral (OPS) imaging against intravital fluorescence microscopy (IFM) for microvascular measurements in normal skin and during wound healing. Experiments were performed on the ears of hairless mice (N = 8). The diameter of arterioles and venules, red blood cell velocity in venules, and the functional capillary density were assessed under normal conditions using OPS imaging and IFM. After creation of a circular wound, these observations were repeated at the identical microvascular regions on days 4, 7, 10, and 15. Images were videotaped, and CapImage was used for off-line computer-assisted analysis. Using OPS imaging, the microcirculation of wounded skin in hairless mice could be observed successfully. The regression analyses against standard IFM revealed a significant (p < 0.001) correlation for measurements of all microcirculatory parameters investigated (venular diameter: r(2) = 0.98, N = 345; red blood cell velocity: r(2) = 0.51, N = 326; functional capillary density: r(2) = 0.44, N = 156). However, for diameter as well as for functional capillary density measurements, OPS imaging yielded lower absolute values compared with IFM. The authors were able to validate OPS imaging against IFM for the measurement of microvascular parameters in an animal model of skin wound healing. Such a device should now help to study the role of microcirculation in physiology and pathophysiology during wound healing in patients. First clinical investigations are promising.

Cytokines, growth factors, and plastic surgery

Numerous inflammatory cytokines and growth factors have been identified and are known to be essential for normal wound healing and host defense, and many have been implicated in disease states treated by plastic surgeons. Cytokines and growth factors are members of a large functional group of polypeptide regulatory molecules secreted by different cell lines. These peptides exert their influence through autocrine and paracrine fashions within sites of injury and repair. Although cytokines and growth factors are crucial in initiating, sustaining, and regulating the postinjury response, these same molecules have been implicated in impaired wound healing, abnormal scarring, and chronic cutaneous diseases. Therapeutic manipulation of inflammatory mediators in normal and impaired wounds has been performed, with mixed clinical results, but evolving strategies such as gene therapy, as well as further characterization of the cellular-mechanism cytokines and growth-factor triggers, will further add to our therapeutic options. This article discusses the current understanding of important cytokines and growth factors involved in the normal injury response and then addresses pathological states associated with an inappropriate expression of these mediators. Finally, a summary of various cytokine and growth factor-directed strategies being used in impaired wound healing states is presented.

Traumatic arteriogenic erectile dysfunction: a rat model

We developed a rat model of traumatic arteriogenic erectile dysfunction (ED) for the study of vasculogenic ED. Bilateral ligation of the internal iliac artery was performed on 30 three-month old male Sprague-Dawley rats as an experimental group. The control group consisted of 12 rats which underwent dissection of the internal iliac artery without ligation. Before their euthanization at 3 days, 7 days, and 1 month (10 rats in the experimental group and four rats in the control group at each time point), erectile function was assessed by electrostimulation of the cavernous nerves. Penile tissues were collected for nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase staining, trichrome staining, electron microscopy and RT-PCR for transforming growth factor beta (TGF-beta1), insulin like growth factor-I (IGF-I) and fibroblast growth factors (FGF) mRNA expression. Electrostimulation of the cavernous nerves revealed a highly significant declining of the intracavernous pressure after 3 and 7 days. No significant recovery of erectile function was noted at 1 month. Histology showed degeneration of the dorsal nerve fibers in all experimental rats. There was little decrease in the bulk of intracavernous smooth muscle in the experimental rats euthanazed 7 and 30 days. NADPH diaphorase staining revealed a significant decrease in nitric oxide synthase (NOS) containing nerve fibers in the dorsal and intracavernosal nerves in all rats in the experimental group. Electron microscopy showed a variety of changes such as collapse of sinusoids, increased cell debris, fibroblast and myofibroblast loss, intracellular deposition of fat and collagen and fatty degeneration. RT-PCR revealed up-regulation of TGF-beta1 after 3 days but not after 7 days or 1 month. There is no significant difference in IGF-I or FGF expression between the experimental and control group. Bilateral ligation of internal iliac arteries produces a reliable animal model for traumatic arteriogenic ED. Further studies are needed to investigate the molecular mechanism of ED in this model.

A review of therapeutic angiogenesis and consideration of its potential applications to plastic and reconstructive surgery

The use of exogenous agents to stimulate the growth of new blood vessels into ischaemic tissue is a potentially revolutionary therapy in a wide variety of clinical specialties. Therapeutic angiogenesis research has been mostly confined to ischaemia of the heart and the lower limb. There has been relatively little research into the potential applications of the technique to plastic, reconstructive and burns surgery. In this paper, relevant published work is reviewed and potential applications of therapeutic angiogenesis to our specialty are considered.

Adenoviral-mediated gene transfer in wound healing

The application of gene transfer strategies to wound healing is not an obvious use of this technology until one considers the important role of cytokines and growth factors in the normal wound healing response. Several gene transfer strategies have been proposed, from in vitro retroviral-mediated gene transfer with autologous transplantation, to in vivo plasmid based gene transfer as retroviral gene transfer. The limitations of these approaches have been efficiency of gene transfer, transgene expression and biologic response. Adenoviral-mediated gene transfer in wound healing is a relatively new application of this vector. The advantage of the adenovirus as a gene transfer vector lies in its ability to transduce nondividing cells of all types at very high efficiency without integration into the host cell's genome. The disadvantage of adenovirus as a vector is the relatively short duration of transgene expression and the inflammatory response it elicits. In the setting of wound healing brief duration of high levels of transgene may be all that is necessary to favorably influence wound healing. Secondly, as wound healing is fundamentally an inflammatory response, the inflammation elicited by the adenovirus may not be detrimental as long as the transgene is a growth factor with significant vulnerary effects such as platelet-derived growth factor-B. This review summarizes the current state of adenoviral-mediated gene transfer in experimental models of impaired wound healing which have laid the groundwork for proposed phase I clinical trials of adenoviral-mediated gene transfer of platelet-derived growth factor-B in chronic venous leg ulcers and chronic nonhealing diabetic foot ulcers. Adenoviral-mediated gene transfer is a useful tool in the study of the role of specific cytokines and growth factors in normal and impaired wound healing. Adenoviral-mediated gene transfer may hold significant promise for clinical application as a means of efficient growth factor delivery in correcting impaired wound healing.

Vascular and epidermal effects of fibroblast growth factor on irradiated and nonirradiated skin flaps

Head and neck cancer surgeons are often faced with the challenge of managing previously irradiated soft tissue that has poor vascularity and slower epithelialization. This study investigates the effect of supplemental basic fibroblast growth factor (bFGF) on flap vascularity, tissue oxygenation, and epidermal regeneration in nonirradiated (n = 40) and irradiated porcine skin flaps (n = 40). Supplemental bFGF increased vascularity in nonirradiated flaps by 80% (p = .005), with a trend to a higher tissue oxygen level by day 14. The irradiated bFGF-treated flaps did not show increased vascularity or higher tissue oxygen levels 2 weeks after surgery. However, in both irradiated and nonirradiated groups, epidermal regeneration increased by greater than 70% with supplemental bFGF (p < .002). The results of this study suggest that supplemental bFGF can increase tissue vascularity in nonirradiated tissues and epidermal regeneration in both nonirradiated and irradiated conditions.

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.

Mitogenic whey extract stimulates wound repair activity in vitro and promotes healing of rat incisional wounds

The ability of single growth factors to promote healing of normal and compromised wounds has been well described, but wound healing is a process requiring the coordinated action of multiple growth factors. Only the synergistic effect on wound healing of combinations containing at most two individual growth factors has been reported. We sought to assess the ability of a novel milk-derived growth factor-enriched preparation ¿mitogenic bovine whey extract (MBWE), which contains six known growth factors, to promote repair processes in organotypic in vitro models and incisional wounds in vivo. MBWE stimulated the contraction of fibroblast-populated collagen lattices in a dose-dependent fashion and promoted the closure of excisional wounds in embryonic day 17 fetal rat skin. Application of MBWE increased incisional wound strength in normal animals on days 3, 5, 7, and 10 and reversed the decrease in wound strength observed following steroid treatment. Wound histology showed increased fibroblast numbers in wounds from normal and steroid-compromised animals. These data suggest the mixture of factors present in bovine milk exerts a direct action on the cells of cutaneous wound repair to enhance both normal and compromised healing.

A new murine model for mammalian wound repair and regeneration

Regeneration is generally considered to be a phenomenon restricted to amphibians in which amputated limbs reform and regrow. We have recently noted a strain of mouse, the MRL, which displays a remarkable capacity for cartilagenous wound closure and provides an example of a phenomenon previously considered to be a form of regeneration. Specifically, through-and-through ear punches rapidly attain full closure with normal tissue architecture reminiscent of regeneration seen in amphibians as opposed to scarring, as usually seen in mammals. Histologically, we have demonstrated normal cell growth and microanatomy, including angiogenesis and chondrogenesis, as opposed to control C57BL/6 mice which have ear holes that contract minimally but do not close. Finally, this phenomenon is a genetically definable quantitative trait.

The effect of recombinant basic fibroblast growth factor (bFGF) in fibrin adhesive vehicle on the healing of ischaemic and normal incisional skin wounds

Normal and ischaemic incisional wounds in rats were treated with recombinant human basic fibroblast growth factor (rbFGF) in fibrin adhesive vehicle. After 10 days of healing the maximum load*S and stress*S (S denotes correction for shrinkage) of ischaemic wounds were increased by 45% and 39%, respectively, after treatment with 20 micrograms rbFGF and by 67% and 56% after treatment with 60 micrograms rbFGF. After 20 days only 20 micrograms rbFGF had any effect and increased maximum load*S by 31% and energy at maximum (load*S, stress*S) by 40%-48%. In normal wounds 0.6-20 micrograms and 60 micrograms rbFGF decreased the strength parameters by 19%-34% and 49%-52%, respectively, after 10 days. After 20 days there was no negative influence but 60 micrograms rbFGF increased the biomechanical properties by 15%-24%. Treatment with the fibrin adhesive vehicle alone decreased the biomechanical properties of ischaemic wounds after 20 days, and of normal wounds after both 10 and 20 days. In conclusion, rbFGF can improve the healing of ischaemic wounds and may be used in the treatment of ischaemic wounds in patients, but it can have negative effects on normal wound healing.

Protein expression of fibroblast growth factor receptor-1 in keratinocytes during wound healing in rat skin

Fibroblast growth factors have been shown to play important roles in wound healing. To define their sites of action, we examined the expression of fibroblast growth factor receptor-1 (FGFR-1) during burn wound healing in rat skin by immunohistochemistry and western blot analysis. In cryostat sections of intact skin, little or no staining was observed. After a burn, however, staining for FGFR-1 was found in newly forming epidermis. The suprabasal layer of such epidermis, composed mostly of regenerating keratinocytes, was stained intensely, whereas keratinocytes in newly forming hair follicles were devoid of staining. Staining gradually decreased week by week after wound closure and was hardly visible 10 weeks after the burn, when the thickness of the epidermis had returned to the normal level. Staining was also found in small blood vessels and capillaries of granulation tissues of the dermis. Western blot analysis using the same antiserum was performed in the newly forming epidermis 10 d after the burn. A single band was detected with an apparent molecular weight of 120 kDa, corresponding to the short membrane-bound form of rat FGFR-1. Our study indicates that FGFR-1 is expressed during wound healing, mainly in regenerating epidermis and to some extent in blood vessels of the dermis. Fibroblast growth factors may affect the proliferation and differentiation of epidermal keratinocytes as well as angiogenesis in the dermis via the FGFR-1 expressed during wound healing.

Growth factors in surgery

Surgical reconstruction of functional and aesthetic defects is often compromised by donor-tissue limitations and wound-healing constraints--problems that can potentially be overcome by peptide growth factor therapy. The effectiveness of growth factor therapy in animal models and in limited human clinical trials has been realized. Epidermal growth factor (EGF), fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), platelet-derived wound-healing formula (PDWHF), transforming growth factor (TGF), the bone morphogenetic proteins (BMPs), and general considerations of growth factor therapy are reviewed.

A freeze-injured skin graft model for the quantitative study of basic fibroblast growth factor and other promoters of angiogenesis in wound healing

A new in vivo model has been developed for the quantitative study of promoters and potential promoters of angiogenesis. Full thickness rat skin autografts received a reproducible and uniform freeze injury, before being applied to full thickness wounds, in order to delay revascularisation. Blood flow in the grafts was measured during the healing period using noninvasive (laser Doppler flowmetry) and invasive (133Xe clearance) techniques. The increase in blood flow over a period of 10-14 days was taken as an index of angiogenesis. These measurements were corroborated by histological assessment of the graft vasculature, using a laminin stain to highlight vascular basement membrane. Freeze injury delayed but did not ultimately prevent full graft revascularisation (p < 0.01 for laser Doppler flowmetry and 133Xe clearance). Application of the angiogenic agent basic fibroblast growth factor (bFGF), in slow release pellet form, stimulated angiogenesis in cryoinjured grafts in a dose-related fashion. Doses of 500 and 5000 ng bFGF produced significant stimulation (500 ng bFGF, p < 0.001, and 5000 ng bFGF, p < 0.01, for both laser Doppler flowmetry and 133Xe clearance; increased vessel profile counts, p < 0.05, at each time point tested for both doses) while 50 ng bFGF had no significant effect. By contrast, 500 ng bFGF had no measurable effect on uninjured grafts. In addition, bFGF-stimulated angiogenesis in cryoinjured grafts was antagonised by a neutralising antibody to bFGF, demonstrating the specificity of action of bFGF in this model.

Fibroblast growth factors: activities and significance of non-neurotrophin neurotrophic growth factors

Although first characterized by virtue of their ability to stimulate endothelial cell proliferation in vitro and angiogenesis in vivo, the fibroblast growth factors are now also well recognized for their neurotrophic activities. Understanding the physiological significance of these multifunctional, virtually ubiquitous and pluripotential molecules, however, remains enigmatic. Recent advances describing their molecular, biochemical and biological characteristics has led to a better understanding of their role in the central nervous system.