Basic fibroblast growth factor stimulation of epidermal wound healing in pigs

The pig as a model system for investigating the recruitment and contribution of myofibroblasts in skin healing

In the skin-healing field, porcine models are regarded as a useful analogue for human skin due to their numerous anatomical and physiological similarities. Despite the widespread use of porcine models in skin healing studies, the initial origin, recruitment and transition of fibroblasts to matrix-secreting contractile myofibroblasts are not well defined for this model. In this review, we discuss the merit of the pig as an animal for studying myofibroblast origin, as well as the challenges associated with assessing their contributions to skin healing. Although a variety of wound types (incisional, partial thickness, full thickness, burns) have been investigated in pigs in attempts to mimic diverse injuries in humans, direct comparison of human healing profiles with regards to myofibroblasts shows evident differences. Following injury in porcine models, which often employ juvenile animals, myofibroblasts are described in the developing granulation tissue at 4 days, peaking at Days 7-14, and persisting at 60 days post-wounding, although variations are evident depending on the specific pig breed. In human wounds, the presence of myofibroblasts is variable and does not correlate with the age of the wound or clinical contraction. Our comparison of porcine myofibroblast-mediated healing processes with those in humans suggests that further validation of the pig model is essential. Moreover, we identify several limitations evident in experimental design that need to be better controlled, and standardisation of methodologies would be beneficial for the comparison and interpretation of results. In particular, we discuss anatomical location of the wounds, their size and depth, as well as the healing microenvironment (wet vs. moist vs. dry) in pigs and how this could influence myofibroblast recruitment. In summary, although a widespread model used in the skin healing field, further research is required to validate pigs as a useful analogue for human healing with regards to myofibroblasts.

Fibroblast growth factor-impregnated collagen-gelatin sponge improves keratinocyte sheet survival

Commercially available cultured epithelial keratinocyte sheets (KSs) have played an essential role in wound healing over the last four decades. Despite the initial uptake by the dermal elements, the survival rate of KS on the dermis-like tissue generated by conventional artificial dermis (AD) is low, making this method unsuitable for standard treatments. Therefore, an innovative AD such as collagen/gelatin sponge (CGS) that maintains the release of human recombinant basic fibroblast growth factor (bFGF) may promote wound healing. In this study, we examined whether combination therapy with KSs and CGS with bFGF (bFGF-CGS) could enhance KS survival by heterologous grafting by transplantation of human-derived KSs in an athymic nude rat wound model of staged skin reconstruction. The CGSs were implanted into skin defect wounds on athymic nude rats, which were then divided into two experimental groups: the bFGF group (CGSs containing bFGF, n = 8) and control group (CGSs with saline, n = 8). Two weeks after implantation, human epithelial cell-derived KSs were grafted onto the dermis-like tissue, followed by assessment of the survival and morphology at one week later using digital imaging, histology (hematoxylin and eosin and Masson's trichrome staining), immunohistology (von Willebrand factor), immunohistochemistry (cytokeratin 1-5-6, Ki-67), and immunofluorescence (collagen IV, pan-cytokeratins) analyses. The bFGF group showed a significantly higher KS survival area (86 ± 58 vs. 32 ± 22 mm2; p < 0.05) and increased epidermal thickness (158 ± 66 vs. 86 ± 40 µm; p < 0.05) compared with the control group, along with higher dermis-like tissue regeneration, neovascularization, epidermal maturation, and basement membrane development. These results indicate that the survival rate of KSs in the dermis-like tissue formed by bFGF-CGS was significantly increased. Therefore, combination treatment of bFGF-CGS and KSs shows potential for full-thickness skin defect reconstruction in clinical situations.

Fibroblast growth factor 2 accelerates the epithelial-mesenchymal transition in keratinocytes during wound healing process

In the wound healing process, the morphology of keratinocytes at the wound edge temporarily changes to a spindle morphology, which is thought to occur due to an epithelial–mesenchymal transition (EMT). Fibroblast growth factor (FGF) 2, also called basic FGF, has the potential to accelerate wound closure by activating vascular endothelial cells and fibroblasts. We examined the effects of FGF2 on keratinocyte morphology and EMT in wounded skin. Histological examination of murine wounds treated with FGF2 revealed that wound edge keratinocytes formed thickened and multilayered epithelia. In addition, we detected wound edge keratinocytes migrating individually toward the wound center. These migrating keratinocytes exhibited not only spindle morphology but also down-regulated E-cadherin and up-regulated vimentin expression, which is characteristic of EMT. In FGF2-treated wounds, a PCR array revealed the upregulation of genes related to EMT, including transforming growth factor (TGF) signaling. Further, FGF2-treated wound edge keratinocytes expressed EMT-associated transcription factors, including Snai2, and showed translocation of β-catenin from the cell membrane to the cytoplasm/nucleus. However, in vitro examination of keratinocytes revealed that FGF2 alone did not activate EMT in keratinocytes, but that FGF2 might promote EMT in combination with TGFβ1. These findings suggest that FGF2 treatment of wounds could promote keratinocyte EMT, accelerating wound closure.

The Japanese Experience with Basic Fibroblast Growth Factor in Cutaneous Wound Management and Scar Prevention: A Systematic Review of Clinical and Biological Aspects

INTRODUCTION

Basic fibroblast growth factor (bFGF) plays several key roles in wound healing. Over the last 2 decades, clinical and basic research on bFGF has been actively conducted in Japan with reports on its potent efficacy in accelerating the healing of chronic ulcers and burn wounds by stimulating key cellular players in the skin. However, its efficacy remains unrecognized internationally. Thus, this study reviews current knowledge about the therapeutic value of bFGF in wound management and scar prevention accumulated in Japan over the last 2 decades.

METHODS

We review the Japanese literature that demonstrates the anti-scarring effects of bFGF and exhaustively assess how these effects are exerted. Using the search terms "bFGF OR growth factors AND wound healing in Japan" and "bFGF AND scar prevention in Japan," we conducted a search of the PubMed database for publications on the role of bFGF in wound and scar management in Japan. All eligible papers published between 1988 and December 2019 were retrieved and reviewed.

RESULTS

Our search yielded 208 articles; 82 were related to the application of bFGF for dermal wound healing in Japan. Of these, 27 fulfilled all inclusion criteria; 11 were laboratory studies, 7 were case reports, 4 were clinical studies, and 5 were randomized controlled trials.

CONCLUSION

Further research, with recognition of the therapeutic value of bFGF in wound and scar management and its clinical applications, is needed to provide additional clinical advantages while improving wound healing and reducing the risk of post-surgical scar formation.

Medium conditioned by human mesenchymal stromal cells reverses low serum and hypoxia-induced inhibition of wound closure

Chronic wounds, such as pressure ulcers, are a common complication of impaired peripheral circulation, such as in advanced diabetes. Factors secreted by mesenchymal stromal cells (MSCs) have been shown to enhance wound healing in vitro and in vivo. However, there is little understanding of the impact of the chronic wound environment, namely the limited supply of nutrients and oxygen, on the ability of wound cells to respond to MSCs. In this study, we first established the effects of hypoxia (1% O2) and low serum (1% serum) concentration on the proliferation and migration of keratinocytes. We found that hypoxia and low serum significantly slowed down these processes. Next, we found that supplementation with human MSC-concentrated conditioned media (hMSC-CM) enhanced both cell migration and proliferation in the presence of hypoxia and low serum. Furthermore, low serum and hypoxia decreased cell spreading and F-actin expression, which was reversed in the presence of hMSC-CM. Several wound healing mediators were identified in hMSC-CM, including IL-5, IL-6, IL-8, IL-9, IP-10, MCP-1, FGF-2, and VEGF. This study suggests that the concentrated secretome of human MSCs can reverse the inhibitory effect of hypoxia and low serum on keratinocyte proliferation and migration. This phenomenon may contribute to the beneficial effects of hMSC-CM on wound healing in vivo.

Physician-initiated first-in-human clinical study using a novel angiogenic peptide, AG30/5C, for patients with severe limb ulcers

AIM

In patients with diabetes or ischemia, angiogenesis and infection control are required for chronic leg ulcers, which substantially impair patients' quality of life. We developed a novel functional peptide, named AG30/5C, with angiogenic and anti-microbial properties. Treatment with AG30/5C significantly accelerated the wound healing of full-thickness defects in mice. To evaluate the safety of AG30/5C in the treatment of leg ulcers, a physician-initiated clinical study was carried out.

METHODS

The first-in-human trial was designed as an open-label treatment with AG30/5C (0.1 mg/mL) given twice per day for 11 days, and with a follow-up period of 17 days. The inclusion criteria for severe skin ulcers were: (i) diabetes or critical limb ischemia; (ii) resistance to standard therapy for 1 month; and (iii) detection of methicillin-resistant Staphylococcus aureus in the skin ulcer.

RESULTS

Four patients were enrolled in this study, and two patients met these criteria. For the evaluation of safety, three adverse effects were reported as possibly related to AG30/5C treatment; however, these adverse effects were not severe and resolved during or after treatment. Thus, there were no safety concerns. In both patients, the size of the ulcer decreased after treatment (44.62% and 10.23% decrease), and further decreased after the follow-up period (73.85% and 10.23% decrease). The former patient was diagnosed as Werner syndrome and the skin ulcer was resistant to standard therapy; however, it was sensitive to AG30/5C treatment.

CONCLUSIONS

Topical treatment with AG30/5C for severe leg ulcers was safe, well tolerated and effective. Geriatr Gerontol Int 2017; 17: 2150-2156.

Physiologically Low Oxygen Enhances Biomolecule Production and Stemness of Mesenchymal Stem Cell Spheroids

Multicellular human mesenchymal stem cell (hMSC) spheroids have been demonstrated to be valuable in a variety of applications, including cartilage regeneration, wound healing, and neoangiogenesis. Physiological relevant low oxygen culture can significantly improve in vitro hMSC expansion by preventing cell differentiation. We hypothesize that hypoxia-cultured hMSC spheroids can better maintain the regenerative properties of hMSCs. In this study, hMSC spheroids were fabricated using hanging drop method and cultured under 2% O2 and 20% O2 for up to 96 h. Spheroid diameter and viability were examined, as well as extracellular matrix (ECM) components and growth factor levels between the two oxygen tensions at different time points. Stemness was measured among the spheroid culture conditions and compared to two-dimensional cell cultures. Spheroid viability and structural integrity were studied using different needle gauges to ensure no damage would occur when implemented in vivo. Spheroid attachment and integration within a tissue substitute were also demonstrated. The results showed that a three-dimensional hMSC spheroid cultured at low oxygen conditions can enhance the production of ECM proteins and growth factors, while maintaining the spheroids' stemness and ability to be injected, attached, and potentially be integrated within a tissue.

Clinical Impact Upon Wound Healing and Inflammation in Moist, Wet, and Dry Environments

SIGNIFICANCE

Successful treatment of wounds relies on precise control and continuous monitoring of the wound-healing process. Wet or moist treatment of wounds has been shown to promote re-epithelialization and result in reduced scar formation, as compared to treatment in a dry environment.

RECENT ADVANCES

By treating wounds in a controlled wet environment, delivery of antimicrobials, analgesics, other bioactive molecules such as growth factors, as well as cells and micrografts, is allowed. The addition of growth factors or transplantation of cells yields the possibility of creating a regenerative wound microenvironment that favors healing, as opposed to excessive scar formation.

CRITICAL ISSUES

Although several manufacturers have conceived products implementing the concept of moist wound healing, there remains a lack of commercial translation of wet wound-healing principles into clinically available products. This can only be mitigated by further research on the topic.

FUTURE DIRECTIONS

The strong evidence pointing to the favorable healing of wounds in a wet or moist environment compared to dry treatment will extend the clinical indications for this treatment. Further advances are required to elucidate by which means this microenvironment can be optimized to improve the healing outcome.

Current understanding of molecular and cellular mechanisms in fibroplasia and angiogenesis during acute wound healing

Cutaneous wound healing ultimately functions to facilitate barrier restoration following injury-induced loss of skin integrity. It is an evolutionarily conserved, multi-cellular, multi-molecular process involving co-ordinated inter-play between complex signalling networks. Cellular proliferation is recognised as the third stage of this sequence. Within this phase, fibroplasia and angiogenesis are co-dependent processes which must be successfully completed in order to form an evolving extracellular matrix and granulation tissue. The resultant structures guide cellular infiltration, differentiation and secretory profile within the wound environment and consequently have major influence on the success or failure of wound healing. This review integrates in vitro, animal and human in vivo studies, to provide up to date descriptions of molecular and cellular interactions involved in fibroplasia and angiogenesis. Significant molecular networks include adhesion molecules, proteinases, cytokines and chemokines as well as a plethora of growth factors. These signals are produced by, and affect behaviour of, cells including fibroblasts, fibrocytes, keratinocytes, endothelial cells and inflammatory cells resulting in significant cellular phenotypic and functional plasticity, as well as controlling composition and remodelling of structural proteins including collagen and fibronectin. The interdependent relationship between angiogenesis and fibroplasia relies on dynamic reciprocity between cellular components, matrix proteins and bioactive molecules. Unbalanced regulation of any one component can have significant consequences resulting in delayed healing, chronic wounds or abnormal scar formation. Greater understanding of angiogenic and fibroplastic mechanisms underlying chronic wound pathogenesis has identified novel therapeutic targets and enabled development of improved treatment strategies including topical growth factors and skin substitutes.

A dynamic system for delivering controlled bromine and chlorine vapor exposures to weanling swine skin

CONTEXT

Assessing the hazards of accidental exposure to toxic industrial chemical (TIC) vapors and evaluating therapeutic compounds or treatment regimens require the development of appropriate animal models.

OBJECTIVE

The objective of this project was to develop an exposure system for delivering controlled vapor concentrations of TICs to the skin of anesthetized weanling pigs. Injury levels targeted for study were superficial dermal (SD) and deep dermal (DD) skin lesions as defined histopathologically.

MATERIALS AND METHODS

The exposure system was capable of simultaneously delivering chlorine or bromine vapor to four, 3-cm diameter exposure cups placed over skin between the axillary and inguinal areas of the ventral abdomen. Vapor concentrations were generated by mixing saturated bromine or chlorine vapor with either dried dilution air or nitrogen.

RESULTS

Bromine exposure concentrations ranged from 6.5 × 10(-4) to 1.03 g/L, and exposure durations ranged from 1 to 45 min. A 7-min skin exposure to bromine vapors at 0.59 g/L was sufficient to produce SD injuries, while a 17-min exposure produced a DD injury. Chlorine exposure concentrations ranged from 1.0 to 2.9 g/L (saturated vapor concentration) for exposures ranging from 3 to 90 min. Saturated chlorine vapor challenges for up to 30 min did not induce significant dermal injuries, whereas saturated chlorine vapor with wetted material on the skin surface for 30-60 min induced SD injuries. DD chlorine injuries could not be induced with this system.

CONCLUSION

The vapor exposure system described in this study provides a means for safely regulating, quantifying and delivering TIC vapors to the skin of weanling swine as a model to evaluate therapeutic treatments.

Topical treatment with basic fibroblast growth factor promotes wound healing and barrier recovery induced by skin abrasion

It has been reported that basic fibroblast growth factor (bFGF) promotes the healing of skin ulceration by inducing fibroblast proliferation, yet the role of bFGF on epidermal barrier function, especially from the perspective of scratch-induced skin abrasion, remains unknown. To this end, we initially developed an epidermal abrasion mouse model induced by scratching with a stainless-steel wire brush, and examined the effects of bFGF on the wound healing induced by skin abrasion. This procedure induced a significant elevation of transepidermal water loss (TEWL) in a scratch-count-dependent manner. This elevated TEWL was significantly decreased following topical application of bFGF to the skin. In addition, bFGF increased the expression of Ki67 in keratinocytes following mechanical scratching. These results suggest that bFGF enhances keratinocyte proliferation, which, in turn, repairs the skin barrier disruption and wounds caused by scratching in mice. Consistently, bFGF stimulated proliferation of normal human epidermal keratinocytes (NHEK). Intriguingly, the effect of bFGF and other growth factors on NHEK proliferation was additive. However, high cell density diminished the effect of bFGF on NHEK proliferation. This particular result can be explained by our observation that FGF receptor mRNA expression in NHEK was low under conditions of high cell density. Our findings suggest that bFGF stimulates keratinocyte proliferation, especially in a lower cell density environment, to repair skin wound in accord with skin barrier recovery.

Harnessing growth factors to influence wound healing

Cutaneous wound healing is a dynamic process with the ultimate goal of restoring skin integrity. On injury to the skin, inflammatory cells, endothelial cells, fibroblasts, and keratinocytes undergo changes in gene expression and phenotype, leading to cell proliferation, migration, and differentiation. Cytokines and growth factors play an essential role in initiating and directing the phases of wound healing. These signaling peptides are produced by a variety of cells and lead to a concerted effort to restore the skin barrier function.

Enhanced skin wound healing by a sustained release of growth factors contained in platelet-rich plasma

Platelet-rich plasma (PRP) contains growth factors that promote tissue regeneration. Previously, we showed that heparin-conjugated fibrin (HCF) exerts the sustained release of growth factors with affinity for heparin. Here, we hypothesize that treatment of skin wound with a mixture of PRP and HCF exerts sustained release of several growth factors contained in PRP and promotes skin wound healing. The release of fibroblast growth factor 2, platelet-derived growth factor-BB, and vascular endothelial growth factor contained in PRP from HCF was sustained for a longer period than those from PRP, calcium-activated PRP (C-PRP), or a mixture of fibrin and PRP (F-PRP). Treatment of full-thickness skin wounds in mice with HCF-PRP resulted in much faster wound closure as well as dermal and epidermal regeneration at day 12 compared to treatment with either C-PRP or F-PRP. Enhanced skin regeneration observed in HCF-PRP group may have been at least partially due to enhanced angiogenesis in the wound beds. Therefore, this method could be useful for skin wound treatment.

Epithelial stem cells, wound healing and cancer

It is well established that tissue repair depends on stem cells and that chronic wounds predispose to tumour formation. However, the association between stem cells, wound healing and cancer is poorly understood. Lineage tracing has now shown how stem cells are mobilized to repair skin wounds and how they contribute to skin tumour development. The signalling pathways, including WNT and Hedgehog, that control stem cell behaviour during wound healing are also implicated in tumour formation. Furthermore, tumorigenesis and wound repair both depend on communication between epithelial cells, mesenchymal cells and bone marrow-derived cells. These studies suggest ways to harness stem cells for wound repair while minimizing cancer risk.

Transplantation of adipose stromal cells promotes neovascularization of random skin flaps

The delivery of bone marrow-derived mononulear cells (BM-MNCs) has been proved to be effective at promoting neovascularization of ischemic skin flaps. However, the limited source of BM-MNCs restricts their clinical application. Stromal vascular fraction (SVF) contains a group of heterogeneous cells in the adipose tissue, including adipose tissue-derived stem cells, and it has abundant reserve in human body. In this study, we evaluated the therapeutic potential of SVF to promote neovascularization of random skin flaps. Female Wistar rats were randomly devided into three groups with 8 in each group and received allogeneic SVF, BM-MNCs and phosphate-buffered saline (PBS), respectively, before surgery. Two days after cell administration, a 10 × 3 cm random skin flap was elevated. Flap survival, blood flow perfusion and capillary density were examined 7 days after surgery, and the relevant mechanism was also explored. Results showed that SVF group and BM-MNCs group had higher survival percentage (72.2 ± 2.0% and 76.4 ± 3.1%, respectively) as compared with the control group (56.8 ± 4.6%, P < 0.05). Blood flow perfusion and capillary density of flap tissues in SVF and BM-MNCs groups were both improved. The expression levels of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were increased in flap tissues of SVF and BM-MNCs groups detected by ELISA. These results indicate that SVF could promote vascularization and increase flap survival probably by secreting VEGF and bFGF. The effect of transplantation of SVF on therapeutic angiogenesis of skin flaps is equivalent to that of BM-MNCs.

A synthetic uric acid analog accelerates cutaneous wound healing in mice

Wound healing is a complex process involving intrinsic dermal and epidermal cells, and infiltrating macrophages and leukocytes. Excessive oxidative stress and associated inflammatory processes can impair wound healing, and antioxidants have been reported to improve wound healing in animal models and human subjects. Uric acid (UA) is an efficient free radical scavenger, but has a very low solubility and poor tissue penetrability. We recently developed novel UA analogs with increased solubility and excellent free radical-scavenging properties and demonstrated their ability to protect neural cells against oxidative damage. Here we show that the uric acid analog (6, 8 dithio-UA, but not equimolar concentrations of UA or 1, 7 dimethyl-UA) modified the behaviors of cultured vascular endothelial cells, keratinocytes and fibroblasts in ways consistent with enhancement of the wound healing functions of all three cell types. We further show that 6, 8 dithio-UA significantly accelerates the wound healing process when applied topically (once daily) to full-thickness wounds in mice. Levels of Cu/Zn superoxide dismutase were increased in wound tissue from mice treated with 6, 8 dithio-UA compared to vehicle-treated mice, suggesting that the UA analog enhances endogenous cellular antioxidant defenses. These results support an adverse role for oxidative stress in wound healing and tissue repair, and provide a rationale for the development of UA analogs in the treatment of wounds and for modulation of angiogenesis in other pathological conditions.

Cellular aspects of wound healing

Wound healing is a dynamic interactive process that involves a sequence of molecular and cellular events. Recent advances in cellular and molecular biology have greatly expanded our understanding of the biological process involved in wound repair and tissue regeneration. From plasma extravasation, with coagulation and platelet aggregation, to reepithelialization and remodeling of injured tissue, the organism acts by trying to restore functionality tissue. Thus, the present study encompasses several cellular aspects involved in the wound healing process, as well as the main drugs used in treating the pathology related to wound healing complications. Economic aspects are also addressed, mainly related to chronic wounds of diabetic feet.

Angiogenesis in cutaneous disease: part I

Angiogenesis is an important process in normal physiology and disease pathogenesis. Angiogenesis is controlled in a healthy body by a system of angiogenic growth factors and angiogenesis inhibitors. When angiogenic growth factors are predominantly expressed, blood vessel growth occurs and disease may result. Successful therapies have been developed that target growth factors, their receptors, or the cascade pathways that are activated by growth factor/receptor interactions. There is good evidence that angiogenesis plays an important role in a wide range of cutaneous maladies, and angiogenesis-targeting therapies are playing an increasing role in the management of dermatologic disease. Cutaneous angiogenesis offers an exciting new arena for targeted dermatologic therapeutics.

LEARNING OBJECTIVES

After completing this learning activity, participants should be able to distinguish angiogenic growth factors and inhibitors, recognize angiogenic mediating agents and compare their mechanisms of action, and apply the use of angiogenic mediating agents in clinical and research situations.

Development of bFGF-chitosan matrices and their interactions with human dermal fibroblast cells

Chitosan (CH) is a naturally derived, biodegradable polymer of glucosamine with a variable frequency of N-acetyl-D-glucosamine units, and has been demonstrated to have numerous pharmacological and wound-healing properties. Biodegradable chitosan films were fabricated using a solvent casting technique and investigated for skin tissue-engineering applications. Basic fibroblast growth factor (bFGF) was incorporated into the CH matrices (1 microg/film) by 3 methods: adsorption, entrapment and covalent binding. Release rates and biological activity of the incorporated bFGF were monitored. Human dermal fibroblasts (HDF cells) were used as an in vitro model for cell response to CH and bFGF-CH films. Cell attachment, growth and acid-soluble collagen quantification were employed as an assessment of cell function. The fibroblasts were found to remain viable on the chitosan films and scaffolds. CH films without bFGF were compatible with HDF cells; however, the fibroblasts did not proliferate. The release profile of adsorbed and bound bFGF from CH films were similar (indicating that binding was not efficient) while entrapped bFGF was not released in the time frame studied. The concentration of bFGF released to the cell culture medium was not high enough to stimulate HDF proliferation. However, cell attachment was significantly increased in chitosan films with bFGF adsorbed onto the surface as compared to control surfaces. HDF cells grown on CH films produced significantly more collagen than those on control surfaces.

The effectiveness of basic fibroblast growth factor in fibrin-based cultured skin substitute in vivo

Cultured skin substitute (CSS), comprised keratinocytes and fibroblasts in a biopolymer matrix, is useful for adjunctive burn therapy. However, the vascularization of CSS is much slower than split-thickness autografts, because it lacks a vascular plexus. This study evaluated the influence of basic fibroblast growth factor (bFGF) on fibrin-based CSS grafting in vivo. Fibrin-based CSS treated with 0, 0.26, 1.3, 6.5, 13, or 130 microg/cm bFGF was transplanted into athymic mice, and macroscopic and histologic examinations of the graft were performed on day 21 posttransplantation. Engrafted CSS of the 0.26 to 6.5 microg/cm bFGF treatment groups were similar to the untreated control. However, the engrafted area was significantly suppressed in the 13 microg/cm bFGF treatment group, and the 130 microg/cm bFGF treatment group was not engrafted. Neovascularization of CSS was significantly increased in the 1.3 microg/cm bFGF treatment group compared with the control (P < .05). The number of human fibroblastic cells in CSS that were positive for vimentin increased significantly in the 0.26 and 1.3 microg/cm bFGF treatment groups (P < .01). CSS treated with 0.26 to 6.5 microg/cm bFGF showed normal epidermis with keratinizing stratified squamous epithelium, whereas the thickness of the epidermis and proliferation of keratinocytes in the basal layer was decreased. These results demonstrated that bFGF treatment (1.3 microg/cm) in fibrin-based CSS may enhance angiogenesis and fibroblast proliferation after transplantation.

Delayed reepithelialization and basement membrane regeneration after wounding in mice lacking CXCR3

Wound healing is a complex, orchestrated series of biological events that is controlled by extracellular components that communicate between cell types to re-establish lost tissue. We have found that signaling by ELR-negative CXC chemokines through their common CXCR3 receptor is critical for dermal maturation during the resolving phase. In addition there needs to be complete maturation of the epidermis and regeneration of a delineating basement membrane for proper functioning. The role of this ligand-receptor system appears confounding as one ligand, CXCL4/(PF4), is present during the initial dissolution and two others, CXCL10/(IP-10) and CXCL11/(IP-9/I-TAC), are expressed by keratinocytes in the later regenerative and resolving phases during which the basement membrane is re-established. We examined CXCR3 signaling role in healing using a mouse lacking this receptor, as all three ligands act solely via the common receptor. Reepithelialization was delayed in CXCR3-deficient mice in both full and partial-thickness excisional wounds. Even at 90 days postwounding, the epidermis of these mice appeared less mature with lower levels of E-cadherin and cytokeratin 18. The underlying basement membrane, a product of both dermal fibroblasts and epidermal keratinocytes, was not fully established with persistent diffuse expression of the matrix components laminin 5, collagen IV, and collagen VII throughout the wound bed. These results suggest that CXCR3 and its ligands play an important role in the re-establishment of the basement membrane and epidermis. These studies further establish the emerging signaling network that involves the CXCR3 chemokine receptor and its ligands as a key regulator of wound repair.

Effects of human midkine on spontaneous resorption of herniated intervertebral discs

This study was performed in 36 rabbits to investigate the role of midkine (MK) in the resorption of herniated intervertebral discs. The L(1-2) disc was excised and immersed in one of three kinds of solution for two hours before relocation into the L4 epidural space. In the MK-treated group, the weight of relocated intervertebral discs decreased more over time than in the control group. Newly formed vessels and inflammatory cells were more frequently observed in the MK-treated group than in the control group two weeks after surgery. The degradation of matrix was more significant in the MK-treated group than in the control group four weeks after surgery. Larger areas were replaced by fibrous tissues in the MK-treated group eight weeks after surgery. Thus, MK can accelerate the resorption of the intervertebral disc relocation to the epidural space. Epidural injection of MK may contribute to the therapy of lumber disc herniation.

Transcriptional responses associated with sulfur mustard and thermal burns in porcine skin

In military and civilian environments, serious cutaneous damage can result from thermal burns or exposure to the blistering agent sulfur mustard [bis (2-chloroethyl) sulfide; HD]. Similar therapies have historically been used to treat cutaneous thermal and HD injuries; however, the underlying molecular mechanisms of tissue damage and wound healing may differ between the types of burns. Using microarray analysis, this study assessed the transcriptional responses to cutaneous HD and thermal injury at 48 hours post-exposure to identify molecular networks and genes associated with each type of skin injury. Ventral abdominal sites on each of 4 weanling swine were exposed to 400 mul of undiluted HD or a heated brass rod (70 degrees C) for 8 minutes and 45-60 seconds, respectively. At 48 hours post-exposure, total RNA was isolated from excised skin samples and hybridized to Affymetrix GeneChip Porcine Genome Arrays (containing 20,201 genes). Both HD and thermal exposure promoted significant transcriptional changes where 290 and 267 transcripts were increased and 197 and 707 transcripts were decreased with HD and thermal exposure, respectively. HD- and thermal-injured skin expressed 149 increased and 148 decreased common transcripts. Comparison of the 10 most significantly changed biological functions for HD and thermal exposures identified 7 overlapping functional groups. Canonical pathways analysis revealed 15 separate signaling pathways containing transcripts associated with both HD and thermal exposure. Within these pathways, 5 transcripts (CXCR4, FGFR2, HMOX1, IL1R1, and TLR4) were identified as known targets for existing phase II/III clinical trial or Food and Drug Administration (FDA)-approved drugs. This study is the first to directly assess transcriptional changes in porcine skin subjected to HD or thermal injury over the same time period.

Effect of zwitterionic polymers on wound healing

The effect of a thin film of a zwitterionic random copolymer composed of carboxybetaine [1-carboxy-N,N-dimethyl-N-(2'-methacryloyloxyethyl)methanaminium inner salt] (CMB) and n-butyl methacrylate (BMA), poly(CMB-r-BMA) (CMB, 30 mol%), on the healing of a full-thickness excisional and incisional wound in hairless rats was examined. The poly(CMB-r-BMA) film significantly enhanced wound closure and complete healing of a full-thickness excisional wound compared with the effect of the poly(n-butyl methacrylate) (PBMA) and the poly(ethylene terephthalate) (PET) films. However, the poly(CMB-r-BMA) film did not enhance healing of a full-thickness incisional wound in hairless rats. The amount of proteins adsorbed and that of neutrophiles adhered onto the poly(CMB-r-BMA) film were significantly smaller than those onto the PBMA and PET films. The results suggested that various cells and growth factors in the wound exudate are utilized effectively by covering an excisional wound with the poly(CMB-r-BMA) film, resulting in acceleration of healing. In addition, the poly(CMB-r-BMA) film significantly enhanced healing of a full-thickness excisional wound in hairless rats compared with the effect of Tegaderm as wound dressings. The poly(CMB-r-BMA) film has potential as a new wound dressing.

Basic fibroblast growth factor treatment for various types of recalcitrant skin ulcers: reports of nine cases

The treatment of chronic intractable ulcers constitutes crucial topics in dermatological practice. We describe here nine cases of different types of therapy-resistant ulcers that were successfully treated with the employment of spraying with basic fibroblast growth factor once daily. When it was initiated, we could easily find in all the cases that the healing process of the ulcers was greatly accelerated by this therapy with the resultant achievement of complete epithelialization in a relatively short time. This therapeutic modality is useful not only for chronic ulcers but also for acute extensive ulcers.

Stromal progenitor cell therapy corrects the wound-healing defect in the ischemic rabbit ear model of chronic wound repair

Chronic wounds create a formidable clinical problem resulting in considerable morbidity and healthcare expenditure. The etiology for wound healing impairment appears to be multifactorial; however, ischemia is a common factor in most types of chronic wounds. Ideal therapy for such wounds would be to correct deficiencies in growth factors and matrix components and provide cellular precursors required for timely wound closure. We hypothesized that stromal progenitor cell (SPC) therapy could correct the ischemic wound-healing defect through both direct and indirect mechanisms. To test this hypothesis, we used the ischemic rabbit ear model of chronic wound healing. We found that treatment of the wounds with SPCs was able to reverse the ischemic wound-healing impairment, with improved granulation tissue formation and reepithelialization compared with vehicle or bone marrow mononuclear cell controls. In vitro, SPCs were found to produce factors involved in angiogenesis and reepithelialization, and extracellular matrix components, providing evidence for both direct and indirect mechanisms for the observed correction of the healing impairment in these wounds. Treatment of ischemic wounds with SPCs can dramatically improve wound healing and provides a rationale for further studies focused on SPCs as a potential cellular therapy in impaired wound healing.

Release of basic fibroblast growth factor from a crosslinked glycosaminoglycan hydrogel promotes wound healing

We describe synthetic extracellular matrix (sECM) hydrogel films composed of co-crosslinked thiolated derivatives of chondroitin 6-sulfate (CS) and heparin (HP) for controlled-release delivery of basic fibroblast growth factor (bFGF) to full-thickness wounds in genetically diabetic (db/db) mice. In this model for chronic wound repair, full-thickness wounds were treated with CS, CS-bFGF, or CS-HP-bFGF films. At 2 and 4 weeks postinjury, wound closure and formation of the new epidermis and dermis were determined. Both CS and CS-HP hydrogel films accelerated wound repair, even without bFGF. Addition of bFGF to CS films showed partial dose-dependent acceleration of wound repair. Importantly, addition of bFGF to co-crosslinked CS-HP sECM films showed a dramatic bFGF dose-dependent acceleration of wound healing, as well as improved dermis formation and vascularization. Compared with 27% wound closure in 2 weeks in the controls, 89% wound closure was observed for mice treated with the CS-HP-bFGF films. The synthetic CS-HP sECM films mimic the chemistry and biology of heparan sulfate proteoglycans, and may have clinical potential for topical delivery of growth factors to patients with compromised wound healing.

Platelet-Rich and Platelet-Poor Plasma

Hemostasis is important for any surgical procedure. One method uses autologous platelet-rich and/or platelet-poor plasma sprayed on the wound site. Although effective, there are little quantitative data available to fully document the extent to which these autologous products function as hemostats. Also, limitations in current animal models make quantitative study of topical hemostats difficult. A porcine partial-thickness skin wound model was developed to compare the hemostatic ability of these treatments with untreated control wounds. Rectangular partial-thickness dermal wounds were created in the back of a pig, which was then sprayed with activated platelet-rich plasma, activated platelet-poor plasma, or left untreated. Bleeding was quantified by two methods: 1) gravimetric measurement of exudate transfer to a sponge over a 15-minute interval, and 2) iron assay of the exudate over this same interval. Values for treated wounds were normalized to those of control wounds to minimize interanimal variability. Both gravimetric and iron assay measurements demonstrated that platelet-rich plasma was effective within 5 minutes after application with normalized bleeding values of approximately 35% and 20%, respectively, of the untreated controls. Corresponding values for platelet-poor plasma were approximately 90% and 65%, respectively, with differences only significant for the iron assay method measured on 10- and 15-minute wound exudate. Although both platelet-rich and platelet-poor plasma demonstrated hemostatic potential, the effect was more robust with the former. Iron assay was a more accurate method of measuring bleeding than gravimetric analysis.

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.

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.

Fabrication of chondroitin sulfate-chitosan composite artificial extracellular matrix for stabilization of fibroblast growth factor

The development of a novel, three-dimensional, macroporous artificial extracellular matrix (AECM) based on chondroitin sulfate (ChS)-chitosan (Chito) combination is reported. The composite AECM composed of ChS-Chito conjugated network was prepared by a homogenizing interpolyelectrolyte complex/covalent conjugation technique through co-crosslinked with N,N-(3-dimethylaminopropyl)-N'-ethyl carbodiimide (EDC) and N-hydroxysuccinimide (NHS). In contrast to EDC/NHS, two different reagents, calcium ion and glutaraldehyde, were used to react with ChS or Chito for the preparation of ChS-Chito composites containing crosslinked ChS or Chito network in the matrix. The stability and in vitro enzymatic degradability of the glutaraldehyde-, EDC/NHS-, and Ca2+ -crosslinked ChS-Chito composite AECMs were all investigated in this study. The results showed that crosslinking improved the stability of prepared ChS-Chito AECMs in physiological buffer solution (PBS) and provided superior protective effect against the enzymatic hydrolysis of ChS, compared with their non-crosslinked counterpart. Because ChS was a heparin-like glycosaminoglycan (GAG), the ChS-Chito composite AECMs appeared to promote binding efficiency for basic fibroblast growth factor (bFGF). The bFGF releasing from the ChS-Chito composite AECMs retained its biological activity as examined by the in vitro proliferation of human fibroblast, depending on the crosslinking mode for the preparation of these composite AECMs. Histological assay showed that the EDC/NHS-crosslinked ChS-Chito composite AECM, after incorporated with bFGF, was biodegradable and could result in a significantly enhanced vascularization effect and tissue penetration. These results suggest that the ChS-Chito composite AECMs fabricated in this study may be a promising approach for tissue-engineering application.

A basic fibroblast growth factor improved the quality of skin grafting in burn patients

To avoid hypertrophic scars in burn wounds, the simultaneous application of basic fibroblast growth factor (bFGF) with regular surgical debridement and skin grafting was investigated for skin hardness by clinical examination and instrumental measurement. As little is known about the role of bFGF in wounds, burn wound scars were tested for hardness. Burn scars in various anatomical locations at least 1 year after final wound healing clinically demonstrated a significantly lower hard score in bFGF-treated wounds than in non-bFGF wounds (0.95+/-0.51 versus 2.3+/-0.66, respectively, p<0.01). In addition, a durometer, which is widely used in industry to measure materials similar to skin, such as rubber and thread-balls, demonstrated a significantly lower reading in bFGF-treated wounds than in non-bFGF wounds (7.9+/-3.64 versus 15.5+/-4.39, bFGF versus non-bFGF, respectively, p<0.01). The results demonstrated that burn wounds treated with clinically approved bFGF might contribute to a better cutaneous wound quality, at least in terms of hardness.

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.

Wound-healing studies in transgenic and knockout mice

Injury to the skin initiates a cascade of events including inflammation, new tissue formation, and tissue remodeling, that finally lead to at least partial reconstruction of the original tissue. Historically, animal models of repair have taught us much about how this repair process is orchestrated and, over recent years, the use of genetically modified mice has helped define the roles of many key molecules. Aside from conventional knockout technology, many ingenious approaches have been adopted, allowing researchers to circumvent such problems as embryonic lethality, or to affect gene function in a tissue- or temporal-specific manner. Together, these studies provide us with a growing source of information describing, to date, the in vivo function of nearly 100 proteins in the context of wound repair. This article focuses on the studies in which genetically modified mouse models have helped elucidate the roles that many soluble mediators play during wound repair, encompassing the fibroblast growth factor (FGF) and transforming growth factor-beta (TGF-beta) families and also data on cytokines and chemokines. Finally, we include a table summarizing all of the currently published data in this rapidly growing field. For a regularly updated web archive of studies, we have constructed a Compendium of Published Wound Healing Studies on Genetically Modified Mice which is avaialble at http://icbxs.ethz.ch/members/grose/woundtransgenic/home.html.

Gene therapy in the treatment of lower extremity wounds

This article presents a brief overview of the etiology of chronic wounds of the lower extremities and their current medical and surgical treatment. Gene therapy as a potential tool for treating therapeutically challenging wounds is described in terms of the vectors employed in gene transfer, as well as the strategies used to promote wound healing. Results from animal model studies, as well as clinical trials, are presented.

Development of alginate wound dressings linked with hybrid peptides derived from laminin and elastin

We designed hybrid peptides, SIRVXVXPG (X: A or G), from a laminin-derived peptide, SIKVAV, and an elastin-derived peptide, VGVAPG, and tried to develop new alginate dressings linked covalently with the hybrid peptides. First, we examined the effectiveness of the hybrid peptides for cell attachment and proliferation using normal human dermal fibroblasts (NHDF) in vitro. The hybrid peptides promoted attachment of NHDF, whereas neither Ac-KSIKVAV nor Ac-KVGVAPG promoted attachment. Although all the peptides we examined promoted the proliferation of NHDF to some extent, the hybrid peptide-coated plates showed strong NHDF proliferative activity, compared with the other peptide. Next, we created alginate dressings linked with some of these peptides and examined their effectiveness in wound healing using a rabbit ear skin defect model in vivo. Nine days after operation, ears with the alginate dressings linked with the hybrid peptides showed significantly greater epithelialization and a larger volume of regenerated tissue compared to those treated with SIVAV-linked, VGVAPG-linked and unlinked alginate dressings. These new alginate dressings linked with the hybrid peptides could be promising dressings especially for wounds with impaired healing.