The function of KGF in morphogenesis of epithelium and reepithelialization of wounds

Regulation of epidermal homeostasis and repair by phosphoinositide 3-kinase

The epidermis undergoes continuous self-renewal to maintain its protective function. Whereas growth factors are known to modulate overall skin homeostasis, the intracellular signaling pathways, which control the delicate balance between proliferation and differentiation in keratinocytes, are largely unknown. Here we show transient upregulation of the phosphoinositide 3-kinase (PI3K) catalytic subunits p110α and p110β in differentiating keratinocytes in vitro, expression of these subunits in the epidermis of normal and wounded skin, and enhanced Akt phosphorylation in the hyperproliferative wound epidermis. Stimulation of PI3K activity in cultured keratinocytes by stable expression of an inducible, constitutively active PI3K mutant promoted cell proliferation and inhibited terminal differentiation in keratinocyte monocultures and induced the formation of a hyperplastic, disorganized and poorly differentiated epithelium in organotypic skin cultures. Activation of PI3K signaling also caused reorganization of the actin cytoskeleton and induced keratinocyte migration in vitro and in skin organ cultures. The identification of 122 genes, which are differentially expressed after induction of PI3K signaling provides insight into the molecular mechanisms underlying the observed effects of active PI3K on keratinocytes and indicates that hyperproliferation may be achieved at the expense of genome integrity. These results identify PI3K as an important intracellular regulator of epidermal homeostasis and repair.

Mast cells are required for normal healing of skin wounds in mice

Mast cells (MCs) have recently been reported to play a pivotal role in the elicitation of inflammatory reactions that are beneficial to the host, e.g., during innate immune responses to bacteria. To explore whether MCs also contribute to wound repair, we studied experimentally induced skin wounds in MC-deficient Kit(W)/Kit(W-v) mice, normal Kit+/+ mice, and MC-reconstituted Kit(W)/Kit(W-v) mice. Wound closure was significantly impaired in the absence of MCs during the first 6 days of wound healing and histomorphometric analyses of MC degranulation at the wound edges revealed distance-dependent MC activation, i.e., MC degranulation was most prominent directly adjacent to the wound. In addition, Kit(W)/Kit(W-v) mice showed impaired extravasation and recruitment of neutrophils to the wounded areas. Notably, wound closure, extravasation, and neutrophil recruitment were found to be normal in MC-reconstituted Kit(W)/Kit(W-v) mice. Therefore, we examined whether MCs promote wound healing by releasing histamine or TNF-alpha. Interestingly, wound closure was reduced in mice treated with an H1-receptor antagonist but not after treatment with an H2-receptor antagonist or in the absence of TNF-alpha. Taken together, our findings indicate that MC activation and histamine release are required for normal cutaneous wound healing.

Syndecan-4 dependent FGF stimulation of mouse vibrissae growth

The development, maintenance and regeneration of epithelial appendages such as hairs or vibrissae depend on reciprocal interactions between the epidermal and the dermal components of the integument. Growth factors are among a number of signaling molecules that have been identified during these developmental events. Growth factors such as fibroblast growth factors (FGFs) bind cell surface heparan sulfate proteoglycans (HSPGs) on their heparan sulfate side chains and as such these proteoglycans act as co-receptors for FGF receptors (FGFRs) by forming a ternary signaling complex of HSPG, FGFR and FGF. The syndecans make up a family (syndecan-1-4) of transmembrane HSPGs. In the present study we examined the growth response of mouse vibrissae to HSPG-binding growth factors as a function of the presence or absence of syndecan-4 in an organ culture system. Syndecan-4 is expressed on keratinocytes that make up the inner root sheath of the vibrissa. Vibrissae from wild-type mice, but not from syndecan-4 null mice, displayed a statistically significant and dose-dependent growth response to FGF-1, FGF-2 and FGF-7. In contrast, a statistically significant growth response is seen in vibrissae from both wild-type and syndecan-4 null mice when the culture medium is supplemented with either hepatocyte growth factor (HGF) that binds to HSPG, insulin that does not bind to HSPG or 5% fetal bovine serum. The syndecan-4 dependent effect of FGF-1, -2 and -7 on the transcriptional activity of IRS expressed genes and of genes involved in cell proliferation reveals a number of different response patterns. In vivo, the vibrissae of syndecan-4 null mice are shorter and have a smaller diameter than those of wild-type mice and this phenotype may result from a suboptimal response to growth factors. Syndecan-1, which is expressed in the outer root sheath of the vibrissae shaft, does not influence the response of the vibrissae to FGF-1, -2 and -7 and the length and diameter of vibrissae of syndecan-1 null mice do not differ from those of wild-type mice.

FGF-10 and its receptor exhibit bidirectional paracrine targeting to urothelial and smooth muscle cells in the lower urinary tract

Control of the regenerative properties of urothelial tissue would greatly aid the clinician in the management of urinary tract disease and disorders. Fibroblast growth factor 10 (FGF-10) is a mitogen which is particularly promising as a protein therapy for urothelial injury. The spatial synthesis, transport, targeting, and mechanistic pathway of FGF-10 and its receptor were studied in a human urothelial cell culture model and in fixed sections of lower urinary tract tissue. Synthesis of FGF-10 was restricted to mesenchymal fibroblasts, and secreted FGF-10 exhibited paracrine transport to two proximal sites, transitional epithelium and smooth muscle cell bundles, both of which were also the exclusive sites of FGF-10 receptor synthesis. The addition of recombinant FGF-10 to quiescent urothelial cells in vitro was sufficient to stimulate DNA synthesis. This stimulation was through a pathway independent of the epidermal growth factor receptor pathway. Deconvolution, light and transmission electron microscopic studies captured FGF-10 and its receptor in association with the urothelial cell surface, in cytoplasm, and within nuclei, observations that describe the mechanism that transduces the mitogenic signal in these tissues. Localization of the FGF-10 receptor to the superficial urothelial layer is clinically significant because intravesical administration of FGF-10 may provide the clinician a means to control the turnover of transitional epithelium in bladder disorders such as interstitial cystitis.

Novel roles of NM23 proteins in skin homeostasis, repair and disease

Keratinocyte growth factor (KGF) is an important regulator of epidermal homeostasis and repair. Therefore, the identification of KGF target genes in keratinocytes should contribute to our understanding of the molecular mechanisms underlying these processes. In a search for KGF-regulated genes, we identified the gene encoding the nucleoside diphosphate kinase NM23-H1. Apart from a housekeeping function, NM23 proteins are involved in the regulation of many cellular processes as well as in tumor metastasis, but their functions in epidermal homeostasis and repair are largely unknown. Here, we show a high expression of NM23-H1 and NM23-H2 in the KGF-responsive keratinocytes of the hyperproliferative epidermis of mouse skin wounds and of patients suffering from the skin disease psoriasis. To determine if this overexpression is functionally important, we generated HaCaT keratinocyte cell lines overexpressing NM23-H1 and/or -H2. Whereas the enhanced levels of NM23 did not affect cell proliferation in monoculture, NM23-H2 and double transfectants but not NM23-H1 transfectants formed a strongly hyperthickened epithelium in three-dimensional organotypic cultures. The abnormal epithelial morphology resulted from enhanced proliferation, reduced apoptosis and alterations in the differentiation pattern. These findings suggest that epidermal homeostasis depends on a tight regulation of the levels of NM23 isoforms.

Id proteins: novel targets of activin action, which regulate epidermal homeostasis

Activin is a member of the transforming growth factor beta (TGF-beta) family, which plays a crucial role in skin morphogenesis and wound healing. To gain insight into the underlying mechanisms of action, we searched for activin-regulated genes in cultured keratinocytes. One of the identified target genes encodes Id1, a negative regulator of helix-loop-helix transcription factors. We show that Id1, Id2, and Id3 are strongly downregulated by activin in keratinocytes in vitro and in vivo. To determine the role of Id1 in keratinocyte biology, we generated stable HaCaT keratinocyte cell lines overexpressing this protein. Our results revealed that enhanced levels of Id1 do not affect proliferation of keratinocytes in monoculture under exponential culture conditions or in response to activin or TGF-beta1. However, in three-dimensional organotypic cultures, Id1-overexpressing HaCaT cells formed a hyperthickened and disorganized epithelium that was characterized by enhanced keratinocyte proliferation, abnormal differentiation, and an increased rate of apoptosis. These results identify an important function of Id1 in the regulation of epidermal homeostasis.

FGF10 is required for cell proliferation and gland formation in the stomach epithelium of the chicken embryo

The development of digestive organs in vertebrates involves active epithelial-mesenchymal interactions. In the chicken proventriculus (glandular stomach), the morphogenesis and cytodifferentiation of the epithelium are controlled by the inductive signaling factors that are secreted from the underlying mesenchyme. Previous studies have shown that Fgf10 is expressed in the developing chicken proventricular mesenchyme, whereas its receptors are present in the epithelium. In our present study, we show that FGF10 is an early mesenchymal signal that is critically associated with the developmental processes in the proventricular epithelium. Furthermore, virus-mediated Fgf10 overexpression in ovo results in a hypermorphic epithelial structure and an increase in epithelial cell number. In contrast, the overexpression of a secreted FGFR2b (sFGFR2b), an FGF10 antagonist, blocks cell proliferation and gland formation in the proventricular epithelium in ovo. This downregulation of proliferative activity was subsequently found to retard gland formation and also to delay differentiation of the epithelium. These results demonstrate that FGF10 signaling, mediated by FGFR1b and/or FGFR2b, is required for proliferation and gland formation in the epithelium in the developing chick embryo.

Nrf transcription factors in keratinocytes are essential for skin tumor prevention but not for wound healing

The Nrf2 transcription factor is a key player in the cellular stress response through its regulation of cytoprotective genes. In this study we determined the role of Nrf2-mediated gene expression in keratinocytes for skin development, wound repair, and skin carcinogenesis. To overcome compensation by the related Nrf1 and Nrf3 proteins, we expressed a dominant-negative Nrf2 mutant (dnNrf2) in the epidermis of transgenic mice. The functionality of the transgene product was verified in vivo using mice doubly transgenic for dnNrf2 and an Nrf2-responsive reporter gene. Surprisingly, no abnormalities of the epidermis were observed in dnNrf2-transgenic mice, and even full-thickness skin wounds healed normally. However, the onset, incidence, and multiplicity of chemically induced skin papillomas were strikingly enhanced, whereas the progression to squamous cell carcinomas was unaltered. We provide evidence that the enhanced tumorigenesis results from reduced basal expression of cytoprotective Nrf target genes, leading to accumulation of oxidative damage and reduced carcinogen detoxification. Our results reveal a crucial role of Nrf-mediated gene expression in keratinocytes in the prevention of skin tumors and suggest that activation of Nrf2 in keratinocytes is a promising strategy to prevent carcinogenesis of this highly exposed organ.

Endostatin influences endothelial morphology via the activated ERK1/2-kinase endothelial morphology and signal transduction

Endostatin, the proteolytic fragment of collagen XVIII, is known to be a potent inhibitor of angiogenesis. However, to date, only limited knowledge exists with regard to the effects of endostatin on vessel morphology and the underlying signaling pathway. The aim of the present work was therefore to determine the impact of endostatin and its collagen XV analogue restin on vessel development during wound healing and embryonic angio- and vasculogenesis. Time lapse experiments and electron microscopy demonstrate similar morphological changes evoked by endostatin and the ERK1/2-kinase inhibitor PD98059. Furthermore, we show that ERK1/2 phosphorylation, a crucial signaling event in vascular morphogenesis, is regulated by endostatin via the protein phosphatase 2A PP2A. These findings provide new insight into a key signaling pathway of vascular remodeling evoked by a matrix-derived factor.

Phenotypic differences between oral and skin fibroblasts in wound contraction and growth factor expression

Wounds of the oral mucosa heal in an accelerated fashion with reduced scarring compared with cutaneous wounds. The differences in healing outcome between oral mucosa and skin could be because of phenotypic differences between the respective fibroblast populations. This study compared paired mucosal and dermal fibroblasts in terms of collagen gel contraction, alpha-smooth muscle actin expression (alpha-SMA), and production of the epithelial growth factors: keratinocyte growth factor (KGF) and hepatocyte growth factor/scatter factor (HGF). The effects of transforming growth factor -beta1 and -beta3 on each parameter were also determined. Gel contraction in floating collagen lattices was determined over a 7-day period. alpha-SMA expression by fibroblasts was determined by Western blotting. KGF and HGF expression were determined by an enzyme-linked immunosorbent assay. Oral fibroblasts induced accelerated collagen gel contraction, yet surprisingly expressed lower levels of alpha-SMA. Oral cells also produced significantly greater levels of both KGF and HGF than their dermal counterparts. Transforming growth factor-beta1 and -beta3, over the concentration range of 0.1-10 ng/mL, had similar effects on cell function, stimulating both gel contraction and alpha-SMA production, but inhibiting KGF and HGF production by both cell types. These data indicate phenotypic differences between oral and dermal fibroblasts that may well contribute to the differences in healing outcome between these two tissues.

Peptide-matrix-mediated gene transfer of an oxygen-insensitive hypoxia-inducible factor-1alpha variant for local induction of angiogenesis

Hypoxia-inducible factor (HIF) constitutes a target in therapeutic angiogenesis. HIF-1alpha functions as a sensor of hypoxia and induces expression of vascular endothelial growth factor (VEGF), which then induces angiogenesis. To explore the potential of HIF-1alpha gene therapy in stimulating wound healing, we delivered a gene encoding a stabilized form of HIF-1alpha, lacking the oxygen-sensitive degradation domain, namely HIF-1alpha deltaODD, by using a previously characterized peptide-based gene delivery vector in fibrin as a surgical matrix. The peptide vector consisted of multiple domains: (i) A cysteine-flanked lysine hexamer provided DNA interactions that were stable extracellularly but destabilized intracellularly after reduction of the formed disulfide bonds. This DNA-binding domain was fused to either (ii) a fibrin-binding peptide for entrapment within the matrix or (iii) a nuclear localization sequence for efficient nuclear targeting. The HIF-1alpha deltaODD gene was expressed and translocated to the nucleus under normoxic conditions, leading to up-regulation of vascular endothelial growth factor (VEGF)-A165 mRNA and protein levels in vitro. When the peptide-DNA nanoparticles entrapped in fibrin matrices were applied to full-thickness dermal wounds in the mouse (10 microg per wound in 30 microl of fibrin), angiogenesis was increased comparably strongly to that induced by VEGF-A165 protein (1.25 microg per wound in 30 microl of fibrin). However, the maturity of the vessels induced by HIF-1alpha deltaODD was significantly higher than that induced by VEGF-A165 protein, as shown by stabilization of the neovessels with smooth muscle. Nonviral, local administration of this potent angiogenesis-inducing gene by using this peptide vector represents a powerful approach in tissue engineering and therapeutic angiogenesis.

Cell cycle inhibitors p21 and p16 are required for the regulation of Schwann cell proliferation

Regulated cell proliferation is a crucial prerequisite for Schwann cells to achieve myelination in development and regeneration. In the present study, we have investigated the function of the cell cycle inhibitors p21 and p16 as potential regulators of Schwann cell proliferation, using p21- or p16-deficient mice. We report that both inhibitors are required for proper withdrawal of Schwann cells from the cell cycle during development and following injury. Postnatal Schwann cells express p21 exclusively in the cytoplasm, first detectable at postnatal day 7. This cytoplasmic p21 expression is necessary for proper Schwann cell proliferation control in the late development of peripheral nerves. After axonal damage, p21 is found in Schwann cell nuclei during the initiation of the proliferation period. This stage is critically regulated by p21, since loss of p21 leads to a strong increase in Schwann cell proliferation. Unexpectedly, p21 levels are upregulated in this phase suggesting that the role of p21 may be more complex than purely inhibitory for the Schwann cell cycle. However, inhibition of Schwann cell proliferation is the overriding crucial function of p21 and p16 in peripheral nerves as revealed by the consequences of loss-of-function in development and after injury. Different mechanisms appear to underlie the inhibitory function, depending on whether p21 is cytoplasmic or nuclear.

Expression of keratinocyte growth factor and its receptor in adaptive changes of ileorectal pouch mucosa

OBJECTIVE

Total proctocolectomy with formation of an ileo-anal pouch is a well-established surgical procedure for patients with ulcerative colitis (UC) or familiar adenomatous polyposis (FAP). The pouch mucosa undergoes adaptive changes, with inflammation of the ileal reservoir being the most common complication. The aetiology is unknown. The keratinocyte growth factor (KGF) has not only been shown to promote intestinal wound healing and re-epithelialization but also to have some immunomodulatory properties. This study was designed to investigate a putative involvement of KGF in observed histomorphological changes in the pouch mucosa.

MATERIALS AND METHODS

Multiple biopsies were obtained from age-matched and sex-matched patients. Biopsies were stained with H&E and scored for inflammation and morphological changes. mRNA expression levels of KGF and KGF-receptor (KGFR) were determined using competitive RT-PCR, protein expression and phosphorylation was analyzed by Western blotting. KGF and KGFR were localized in tissue samples by immunohistochemistry.

RESULTS

Expression of KGF and KGFR was significantly increased in inflamed and adapting mucosa. Patterns of expression did not significantly differ in pouch mucosa from UC or FAP patients. Protein expression correlated with the mRNA results and KGFR was shown to be activated in adapting pouch mucosa. KGF was detected on subepithelial cells, mainly on fibroblasts, whereas expression of KGFR was restricted to epithelial cells.

CONCLUSION

Expression of KGF and KGFR is significantly increased in the pouch mucosa, suggesting an involvement of this growth factor in tissue repair and adaptive changes. Topical application of KGF might alleviate the inflammatory and promote the adaptive process in the ileo-anal pouch mucosa.

The fibroblast growth factor binding protein is a novel interaction partner of FGF-7, FGF-10 and FGF-22 and regulates FGF activity: implications for epithelial repair

The fibroblast growth factor-binding protein (FGF-BP) binds and activates FGF-1 and FGF-2, thereby contributing to tumor angiogenesis. In this study, we identified novel binding partners of FGF-BP, and we provide evidence for a role of this protein in epithelial repair processes. We show that expression of FGF-BP increases after injury to murine and human skin, in particular in keratinocytes. This upregulation is most likely achieved by major keratinocyte mitogens present at the wound site. Most importantly, we demonstrate that FGF-BP interacts with FGF-7, FGF-10, and with the recently identified FGF-22, and enhances the activity of low concentrations of ligand. Due to the important functions of FGF-7 and FGF-10 for repair of injured epithelia, our findings suggest that upregulation of FGF-BP expression after injury stimulates FGF activity at the wound site, thus enhancing the process of epithelial repair.

Allogeneic versus xenogeneic immune reaction to bioengineered skin grafts

There are conflicting reports on the survival and immune reaction to allografts and xenografts of cultured skin substitutes (CSS). In this study, we investigated the allogeneic and xenogeneic responses to CSS of human keratinocytes and genetically engineered CSS expressing keratinocyte growth factor (KGF) that forms a hyperproliferative epidermis. CSS (control and KGF modified) and neonatal human foreskins were evaluated by immunohistochemistry for the expression of MHC class I and II. To study allograft rejection, grafts were transplanted to human peripheral blood mononuclear cell (huPBMC)-reconstituted SCID mice. To study xenograft rejection, grafts were transplanted to immunocompetent mice. Graft survival and immune reaction were assessed visually and microscopically. After transplantation, control CSS formed a normal differentiated epidermis, whereas KGF CSS formed a hyperproliferative epidermis. Control and KGF CSS expressed class I similar to neonatal foreskin, but did not express class II. In the allograft model, rejection of neonatal foreskins was between 5 and 9 days. In contrast, neither control nor KGF CSS was rejected by huPBMC-SCID mice. Histology showed dense mononuclear cell infiltration in human foreskins, with few, if any, mononuclear cells in control or KGF CSS. In contrast to the allogeneic reaction, CSS (control and KGF) were rejected in the xenograft model, but rejection was delayed (9-21 days) compared with neonatal skin (5-8 days). Humanized SCID mice rejected allografts of human neonatal foreskins, but did not reject control CSS or KGF CSS, even though the KGF CSS formed a hyperproliferative epidermis. Rejection of control and KGF CSS by immunocompetent mice in a xenograft model was comparable and their survival was significantly prolonged compared with neonatal skin. These results demonstrate that control CSS and hyperproliferative KGF CSS are less immunogenic than normal human skin and that sustained hyperproliferation of the epidermis does not accelerate rejection.

Reduction of radiochemotherapy-induced early oral mucositis by recombinant human keratinocyte growth factor (palifermin): Experimental studies in mice

PURPOSE

To study the effect of recombinant human keratinocyte growth factor (rHuKGF or palifermin) on oral mucositis induced by radiochemotherapy in a mouse model.

METHODS AND MATERIALS

Cis-diamminedichloroplatinum (cisplatin) and/or 5-fluorouracil were given before single dose irradiation, combined with palifermin before or after the treatment, or both. Daily fractionated irradiation for 2 weeks was followed by graded test doses. With additional chemotherapy in Week 1, palifermin was given before radiotherapy and at the end of the first week, or additionally at the end of Week 2. Radiochemotherapy in Week 2 was combined with palifermin at the end of Weeks 1 and 2, Weeks 1, 2, and 3, or additionally before radiotherapy. Ulceration of mouse tongue mucosa was analyzed as the endpoint.

RESULTS

The dose associated with ulcer induction in 50% of the mice (ED(50)) for single-dose irradiation was 11.5 +/- 0.7 Gy. Palifermin increased the ED(50) to about 19 Gy in all protocols tested. Similar values were observed when chemotherapy was added before irradiation. With fractionated irradiation, palifermin increased the ED(50) for test irradiation from 5.7 +/- 1.5 Gy to 12-15 Gy, depending on the administration protocol. With chemotherapy in Week 1, two palifermin injections had no significant effect, but a third injection increased the ED(50) to 13 Gy. With chemotherapy in Week 2, all palifermin protocols resulted in ED(50) values of 13-14 Gy.

CONCLUSION

A marked increase in oral mucosal radiation tolerance by palifermin was found, which was preserved in combinations with chemotherapy using cisplatin and/or 5-fluorouracil.

Gammadelta T cell-induced hyaluronan production by epithelial cells regulates inflammation

Nonhealing wounds are a major complication of diseases such as diabetes and rheumatoid arthritis. For efficient tissue repair, inflammatory cells must infiltrate into the damaged tissue to orchestrate wound closure. Hyaluronan is involved in the inflammation associated with wound repair and binds the surface of leukocytes infiltrating damaged sites. Skin gammadelta T cells play specialized roles in keratinocyte proliferation during wound repair. Here, we show that gammadelta T cells are required for hyaluronan deposition in the extracellular matrix (ECM) and subsequent macrophage infiltration into wound sites. We describe a novel mechanism of control in which gammadelta T cell-derived keratinocyte growth factors induce epithelial cell production of hyaluronan. In turn, hyaluronan recruits macrophages to the site of damage. These results demonstrate a novel function for skin gammadelta T cells in inflammation and provide a new perspective on T cell regulation of ECM molecules.

Immunohistochemical analysis of keratinocyte growth factor and fibroblast growth factor 10 expression in psoriasis

The pathogenic mechanism underlying the hyperproliferation of keratinocytes in psoriasis is still not completely clarified. The production of cytokines released by activated T lymphocytes infiltrating the upper dermis probably has a crucial role. Even dermal fibroblasts can participate in the process through the secretion of growth factors, and some studies have reported an increased expression of the insulin-like growth factor 1. Few studies, however, have focused on the possible involvement of the keratinocyte growth factor (KGF/FGF-7) and the fibroblast growth factor 10 (FGF-10/KGF-2), which are secreted by fibroblasts and stimulate keratinocyte proliferation acting through a receptor specifically expressed by epithelial cells. The aim of this study was to investigate the expression of KGF and FGF-10 on the skin of patients with psoriasis by immunohistochemical analysis and to evaluate the correlation with the lymphocyte infiltrate and the epidermal proliferation. Immunostaining for KGF and FGF-10 showed that both the growth factors are upregulated in the upper dermis of psoriatic skin, and that the expression is correlated with the presence of T-cell infiltrate and with keratinocyte proliferation. Our data suggest that in psoriatic lesions activated lymphocytes can stimulate fibroblasts to produce KGF and FGF-10, which in turn contribute to sustain the hyperproliferative status of the keratinocytes.

Comprehensive analysis of FGF and FGFR expression in skin: FGF18 is highly expressed in hair follicles and capable of inducing anagen from telogen stage hair follicles

We quantified the mRNA expression of all 22 fibroblast growth factor family members (FGF) and their four receptors (FGFR) in adult mouse full-thickness skin at various stages of the hair growth cycle. We found that in addition to mRNA encoding FGF previously identified in skin (FGF1, 2, 5, 7, 10, 13, and 22), FGF18 mRNA was also strongly expressed. Expression of these FGF varied throughout hair growth cycle: mRNA expression of FGF18 and 13 peaked at telogen; FGF7 and 10 at anagen V; and FGF5 and 22 at anagen VI. In situ hybridization revealed that FGF18 mRNA is mainly expressed in the anagen inner root sheath and telogen bulge of hair follicles. In culture, FGF18 stimulated DNA synthesis in human dermal fibroblasts, dermal papilla cells, epidermal keratinocytes and vascular endothelial cells. When FGF18 was administered subcutaneously to mice in a uniform telogen state, anagen hair growth was observed. Our findings suggest that FGF18 is important for the regulation of hair growth and the maintenance of skin in adult mice.

FGF signals specifically regulate the structure of hair shaft medulla via IGF-binding protein 5

Reciprocal interactions between the dermal papilla and the hair matrix control proliferation and differentiation in the mature hair follicle. Analysis of expression suggests an important role for FGF7 and FGF10, as well as their cognate receptor FGFR2-IIIb, in these processes. Transgenic mice that express a soluble dominant-negative version of this receptor in differentiating hair keratinocytes were generated to interfere with endogenous FGF signalling. Transgenic mice develop abnormally thin but otherwise normal hairs, characterised by single columns of medulla cells in all hair types. All structural defects and the accompanying changes of global gene expression patterns are restricted to the hair medulla. Forced transgenic expression of IGF-binding protein 5, whose expression level is elevated upon suppression of FGFR2-IIIb-mediated signalling largely phenocopies the defect of dnFgfr2-IIIb-expressing hairs. Thus, the results identify Igfbp5-mediated FGFR2-IIIb signals as a key regulator of the genetic program that controls the structure of the hair shaft medulla.

Epidermal stem cells: the cradle of epidermal determination, differentiation and wound healing

The field of epidermal stem cells has dramatically advanced in the last decade, leading to a better understanding of the molecular factors, signalling pathways and cellular events that identify and characterize stem cells, thus revealing their immense potential for therapeutic use. Furthermore, multipotent epidermal stem cells present the major advantage of easy accessibility with the discovery of their specific location within the bulge of the hair follicle. This review focuses on the most recent findings on epidermal stem cells, and their potential role in initial epidermal commitment, differentiation and wound healing processes in the skin.

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.

Interaction of exogenous liposomal insulin-like growth factor-I cDNA gene transfer with growth factors on collagen expression in acute wounds

Growth factors have been shown to modulate the complex cascade of wound healing, however, interaction between different growth factors during dermal and epidermal regeneration is still not entirely defined. We have recently shown that exogenous liposomal gene transfer of cDNA results in physiologic expression and response in an acute wound. In the present study we determined the interaction between insulin-like growth factor-I (IGF-I), a mesenchymal growth factor, administered as liposomal cDNA, with other dermal and epidermal growth factors on collagen synthesis in an acute wound. Sprague-Dawley rats were given a scald burn to inflict an acute wound and divided into two groups to receive weekly subcutaneous injections of liposomes plus a beta-galactosidase containing plasmid (Lac Z [0.2 microg, vehicle]), or liposomes plus the IGF-I cDNA containing plasmid (2.2 microg) and Lac Z (0.2 microg). Immunological assays, histological and immunohistochemical techniques were used to determine growth factor concentration and different types of collagen (I, III, and IV) after IGF-I cDNA gene transfer. IGF-I cDNA transfer accelerated reepithelization and was associated with increased levels of IGF-I, fibroblast growth factor, keratinocyte growth factor, vascular endothelial cell growth factor, and platelet-derived growth factor protein expression. IGF-I cDNA had no effect on transforming growth factor-beta. IGF-I cDNA significantly increased type IV collagen while it had no effect on types I and III collagen. Exogenously administered IGF-I cDNA increased protein concentrations of keratinocyte growth factor, fibroblast growth factor, platelet-derived growth factor, and type IV collagen. We conclude that liposomal IGF-I gene transfer can accelerate wound healing without causing an increase in types I and III collagen expression.

ADAMTS1 proteinase is up-regulated in wounded skin and regulates migration of fibroblasts and endothelial cells

The metalloproteinase ADAMTS1 (a disintegrin and metalloproteinase with thrombospondin motifs) is induced under inflammatory conditions, and it is also a potent inhibitor of angiogenesis. Due to these properties, we speculated about the role of ADAMTS1 in cutaneous wound repair. Here we have shown up-regulation of ADAMTS1 expression in wounds of normal and particularly of healing-impaired genetically diabetic mice. Immunofluorescence staining identified macrophages as the source of ADAMTS1 in early wounds, whereas keratinocytes and fibroblasts produce this protein at later stages of wound healing. The distribution of ADAMTS1 in the normal and wounded epidermis, its regulation in cultured keratinocytes, as well as the skin phenotype of ADAMTS1 knock-out mice suggests a role of this metalloproteinase in keratinocyte differentiation. Furthermore, we provide evidence for a novel dual function of ADAMTS1 in fibroblast migration; although low concentrations of this protein stimulate fibroblast migration via its proteolytic activity, high concentrations inhibit this process because of binding to fibroblast growth factor-2 and subsequent inhibition of its promotogenic activity. Similar effects were also observed with endothelial cells. Taken together, our results suggest a role of ADAMTS1 in keratinocyte differentiation and migration of fibroblasts and endothelial cells in healing skin wounds.

The novel cytokine p43 stimulates dermal fibroblast proliferation and wound repair

The multifunctional cytokine p43 acts on endothelial and immune cells to control angiogenesis and inflammation. In this report, we describe an additional activity of p43 that specifically promotes fibroblast proliferation and wound repair. In skin wound regions from mice, tumor necrosis factor-alpha induced p43 expression and secretion from macrophages recruited to the site. p43 also promoted fibroblast proliferation through its 146-amino acid N-terminal domain as revealed by deletion mapping. This p43-induced fibroblast proliferation was mediated by extracellular signal-regulated kinase (Erk). Depletion of endogenous p43 in mice by gene disruption retarded wound repair, whereas exogenous supplementation of recombinant human p43 to the wound area stimulated dermal fibroblast proliferation, collagen production, and wound closure. Thus, we have identified a novel p43 activity involving the stimulation of fibroblast proliferation, which could be applied therapeutically to aid wound repair.

Tyrosine kinases in disease: overview of kinase inhibitors as therapeutic agents and current drugs in clinical trials

Tyrosine kinases, first described as oncogenes, have been shown to play a role in normal cellular processes. Aberrations in tyrosine kinase activity lead to disease states. For fifteen years it has been postulated that the inhibition of tyrosine kinases may have therapeutic utility and the design and testing of inhibitors have been major focuses of research and development in both academic institutions and pharmaceutical companies. While early research focused on developing chemical entities that mimic phosphotyrosine, later research has focused on developing competitive adenosine triphosphate (ATP) inhibitors with various levels of selectivity on kinase targets. This review focuses on a discussion of tyrosine kinases thought to be important in disease, including platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), vascular endothelial cell growth factor (VEGF), epidermal growth factor (EGF) receptors, HER-2 and Src. In addition, the classes of inhibitors designed to affect these targets and that have overcome research and development challenges and entered clinical trials are discussed. These include isoxazole, quinazoline, substituted pyrimidines and indolinone compounds, all of which are in clinical trials or near clinical development by SUGEN, Zeneca, Novartis, Pfizer and Parke-Davis. A summary of the chemistry and activity of these agents is provided.

Fibroblast growth factor signaling in tumorigenesis

Fibroblast growth factors and their signaling receptors have been associated with multiple biological activities, including proliferation, differentiation and motility. Consequently, they have evoked interest as candidate oncogenes with the potential to initiate and/or promote tumorigenesis. This has resulted in a large literature describing the presence of these growth factors and their receptors in cancer cell lines and primary tumors of diverse origin. However, it is only recently that compelling evidence has emerged to implicate the fibroblast growth factors (Fgfs) and their receptors in the genesis of human cancers. Here, we outline the model systems that demonstrate the potential oncogenic nature of Fgf signaling and summarise recent evidence that implicates aberrant Fgf signaling as important in the natural history of some common human cancers.

Expression of different p63 variants in healing skin wounds suggests a role of p63 in reepithelialization and muscle repair

Healing of skin wounds in mammals involves partial reconstruction of the dermis and coverage of the injured site by keratinocytes. The latter process is achieved by extensive migration and hyperproliferation of keratinocytes at the wound rim. Because the p53 protein family member p63 is expressed in human hyperproliferative epidermis, this study determined whether enhanced keratinocyte proliferation correlates with the expression of p63. Therefore, we investigated the temporal and spatial distribution of four major variants of the p63 transcription factor-TAp63alpha, TAp63gamma, DeltaNp63alpha and DeltaNp63gamma-during normal skin wound healing in mice. Transcripts encoding amino-terminally truncated DeltaNp63 variants were found at high levels in basal and suprabasal keratinocytes of the hyperproliferative wound epithelium. Interestingly, TAp63 variants, which include the conserved transactivation domain TA at their amino-terminus, were also expressed in wound keratinocytes as well as at the edge of the injured subcutaneous muscle panniculus carnosus. These findings suggest splice-variant specific functions of p63 in reepithelialization and muscle repair.

The water-soluble extract of Illicium anisatum stimulates mouse vibrissae follicles in organ culture

It is well known that reduced blood flow in the scalp is a cause of alopecia. We have shown previously that the extract of Illicium anisatum increases subcutaneous blood flow in mice. In the present study, we used an organ culture system to examine whether this extract promoted hair follicle elongation. B6C3HF1 mouse vibrissae follicles were cultured in serum-free medium for 7 days at 31 degrees C. Follicles treated with water-soluble (WS) extracts of the leaves, fruits and roots of Illicium anisatum or shikimic acid grew significantly longer than controls. In contrast, ethyl acetate-soluble (AS) extracts and n-hexane-soluble (HS) extracts of the leaves, fruits and roots of the plant inhibited hair follicles and shaft growth. Fractionation of the WS fruit extract showed that the number 1 and number 2 fractions possessed hair follicle elongation activity. GC/MS analysis revealed that the number 1 fraction contained shikimic acid, and that the number 2 fraction was a mixture of many components including glycosides and polysaccharides. Reverse transcription-polymerase chain reaction analysis demonstrated that shikimic acid also induced mRNA expression of insulin-like growth factor-1, keratinocyte growth factor, and vascular endothelial growth factor in the hair follicles. These results suggest that the WS extract of Illicium anisatum promotes hair growth and may be a useful additive in hair growth products.

FGF-7 expression enhances the performance of bioengineered skin

To improve the performance of bioengineered skin, we used a recombinant retrovirus encoding FGF-7 to modify diploid human keratinocytes genetically. Control or FGF-7-expressing keratinocytes were seeded onto acellular human dermis to form bioengineered skin. Gene-modified skin secreted significant levels of FGF-7 and formed a thicker and hyperproliferative epidermis with about four times the number of cells per square centimeter. Secretion of an endogenous trophic factor, VEGF, was increased approximately 5-fold. Migration of FGF-7-expressing keratinocytes was stimulated as was the self-healing of bioengineered skin expressing FGF-7. When tested in a bacterial infection model, the antimicrobial properties of FGF-7-expressing skin were increased >500-fold against both gram-negative and gram-positive bacteria. After transplantation to full-thickness wounds on athymic mice, skin expressing FGF-7 was revascularized more rapidly. These results demonstrate that genetic modification can be used to enhance performance and that expression of FGF-7 augments several properties important to the wound-healing properties of bioengineered skin.

MRP8 and MRP14 control microtubule reorganization during transendothelial migration of phagocytes

MRP14 (S100A9) is the major calcium-binding protein of neutrophils and monocytes. Targeted gene disruption reveals an essential role of this S100 protein for transendothelial migration of phagocytes. The underlying molecular mechanism comprises major alterations of cytoskeletal metabolism. MRP14, in complex with its binding partner MRP8 (S100A8), promotes polymerization of microtubules. MRP14 is specifically phosphorylated by p38 mitogen-activated protein kinase (MAPK). This phosphorylation inhibits MRP8/MRP14-induced tubulin polymerization. Phosphorylation of MRP14 is antagonistically regulated by binding of MRP8 and calcium. The biologic relevance of these findings is confirmed by the fact that MAPK p38 fails to stimulate migration of MRP14-/- granulocytes in vitro and MRP14-/- mice show a diminished recruitment of granulocytes into the granulation tissue during wound healing in vivo. MRP14-/- granulocytes contain significantly less polymerized tubulin, which subsequently results in minor activation of Rac1 and Cdc42 after stimulation of p38 MAPK. Thus, the complex of MRP8/MRP14 is the first characterized molecular target integrating MAPK- and calcium-dependent signals during migration of phagocytes.

Dendritic epidermal T cells regulate skin homeostasis through local production of insulin-like growth factor 1

A fine balance between rates of proliferation and apoptosis in the skin provides a defensive barrier and a mechanism for tissue repair after damage. Vgamma3(+) dendritic epidermal T cells (DETCs) are primary modulators of skin immune responses. Here we show that DETCs both produce and respond to insulin-like growth factor 1 (IGF-1) after T cell receptor stimulation. Mice deficient in DETCs had a notable increase in epidermal apoptosis that was abrogated by the addition of DETCs or IGF-1. Furthermore, DETC-deficient mice had reduced IGF-1 receptor activation at wound sites. These findings indicate critical functions for DETC-mediated IGF-1 production in regulating skin homeostasis and repair.

Activities of the matrix metalloproteinase stromelysin-2 (MMP-10) in matrix degradation and keratinocyte organization in wounded skin

The matrix metalloproteinase stromelysin-2 is expressed in keratinocytes of the epithelial tongue of skin wounds, suggesting a role in keratinocyte migration. Here, we show that stromelysin-2 enhances migration of cultured keratinocytes. To gain insight into the in vivo activities of stromelysin-2 in epithelial repair, we generated transgenic mice expressing a constitutively active stromelysin-2 mutant in keratinocytes. These animals had no alterations in skin architecture, and the healing rate of skin wounds was normal. Histologically, however, we found abnormalities in the organization of the wound epithelium. Keratinocytes at the migrating epidermal tip were scattered in most sections of mice with high expression level, and there was a reduced deposition of new matrix. In particular, the staining pattern of laminin-5 at the wound site was altered. This may be due to proteolytic processing of laminin-5 by stromelysin-2, because degradation of laminin-5 by this enzyme was observed in vitro. The inappropriate matrix contact of keratinocytes was accompanied by aberrant localization of beta1-integrins and phosphorylated focal adhesion kinase, as well as by increased apoptosis of wound keratinocytes. These results suggest that a tightly regulated expression level of stromelysin-2 is required for limited matrix degradation at the wound site, thereby controlling keratinocyte migration.

Keratinocyte growth factor/fibroblast growth factor 7, a homeostatic factor with therapeutic potential for epithelial protection and repair

Keratinocyte growth factor (KGF) is a paracrine-acting, epithelial mitogen produced by cells of mesenchymal origin. It is a member of the fibroblast growth factor (FGF) family, and acts exclusively through a subset of FGF receptor isoforms (FGFR2b) expressed predominantly by epithelial cells. The upregulation of KGF after epithelial injury suggested it had an important role in tissue repair. This hypothesis was reinforced by evidence that intestinal damage was worse and healing impaired in KGF null mice. Preclinical data from several animal models demonstrated that recombinant human KGF could enhance the regenerative capacity of epithelial tissues and protect them from a variety of toxic exposures. These beneficial effects are attributed to multiple mechanisms that collectively act to strengthen the integrity of the epithelial barrier, and include the stimulation of cell proliferation, migration, differentiation, survival, DNA repair, and induction of enzymes involved in the detoxification of reactive oxygen species. KGF is currently being evaluated in clinical trials to test its ability to ameliorate severe oral mucositis (OM) that results from cancer chemoradiotherapy. In a phase 3 trial involving patients who were treated with myeloablative chemoradiotherapy before autologous peripheral blood progenitor cell transplantation for hematologic malignancies, KGF significantly reduced both the incidence and duration of severe OM. Similar investigations are underway in patients being treated for solid tumors. On the basis of its success in ameliorating chemoradiotherapy-induced OM in humans and tissue damage in a variety of animal models, additional clinical applications of KGF are worthy of investigation.

Activated hepatic stellate cells express keratinocyte growth factor in chronic liver disease

Keratinocyte growth factor (KGF), a member of the fibroblast growth factor (FGF) family, is a specific mitogen for different types of epithelial cells and a potent survival factor for these cells under stress conditions. KGF expression increases strongly after injury to various tissues, including the skin and the intestine, and signaling via the KGF receptor was shown to be crucial for repair of skin wounds and for liver regeneration. Here we demonstrate an increased expression of KGF in chronic liver disease associated with fibrosis. The extent of KGF overexpression correlated strongly with the stage of fibrosis. As the cellular source of KGF we identified activated hepatic stellate cells (HSCs)/myofibroblasts. In contrast to the ligand, the KGF receptor, FGFR2-IIIb, was exclusively expressed by hepatocytes, but not by activated HSCs or other parenchymal or nonparenchymal liver cells. Based on the known effects of KGF on hepatocytes in vitro, our findings suggest that HSC/myofibroblast-derived KGF may enhance liver regeneration and/or hepatocyte survival in patients with chronic liver disease.

Fibroblast growth factors in epithelial repair and cytoprotection

Growth factors are polypeptides that stimulate the division of certain cell types at low concentrations. Fibroblast growth factor (FGF) 7 (FGF-7) and its homologue FGF-10 act specifically on various types of epithelial cells including keratinocytes of the skin, intestinal epithelial cells and hepatocytes. In addition, FGF-7 and FGF-10 have been shown to be more than growth factors: they can protect epithelial cells from damaging effects induced, for example, by radiation and oxidative stress. Therefore, they are currently in clinical trials for the treatment of oral mucositis, a severe side-effect of cancer therapy characterized by painful inflammation and ulceration of the oral epithelium. To gain insight into the mechanisms of FGF-7/FGF-10 action in epithelial cells, we searched for genes that are regulated by these growth factors. Indeed, we identified genes that help us to explain the mechanisms that underlie the effects of FGF-7. Most interestingly, several genes were identified that are likely to mediate the cytoprotective effect of FGF-7 for epithelial cells in vitro and possibly also in injured and diseased tissues in vivo.

Parallels between tissue repair and embryo morphogenesis

Wound healing involves a coordinated series of tissue movements that bears a striking resemblance to various embryonic morphogenetic episodes. There are several ways in which repair recapitulates morphogenesis. We describe how almost identical cytoskeletal machinery is used to repair an embryonic epithelial wound as is involved during the morphogenetic episodes of dorsal closure in Drosophila and eyelid fusion in the mouse foetus. For both naturally occurring and wound-activated tissue movements, JNK signalling appears to be crucial, as does the tight regulation of associated cell divisions and adhesions. In the embryo, both morphogenesis and repair are achieved with a perfect end result, whereas repair of adult tissues leads to scarring. We discuss whether this may be due to the adult inflammatory response, which is absent in the embryo.

Cellular and genetic analysis of wound healing in Drosophila larvae

To establish a genetic system to study postembryonic wound healing, we characterized epidermal wound healing in Drosophila larvae. Following puncture wounding, larvae begin to bleed but within an hour a plug forms in the wound gap. Over the next couple of hours the outer part of the plug melanizes to form a scab, and epidermal cells surrounding the plug orient toward it and then fuse to form a syncytium. Subsequently, more-peripheral cells orient toward and fuse with the central syncytium. During this time, the Jun N-terminal kinase (JNK) pathway is activated in a gradient emanating out from the wound, and the epidermal cells spread along or through the wound plug to reestablish a continuous epithelium and its basal lamina and apical cuticle lining. Inactivation of the JNK pathway inhibits epidermal spreading and reepithelialization but does not affect scab formation or other wound healing responses. Conversely, mutations that block scab formation, and a scabless wounding procedure, provide evidence that the scab stabilizes the wound site but is not required to initiate other wound responses. However, in the absence of a scab, the JNK pathway is hyperinduced, reepithelialization initiates but is not always completed, and a chronic wound ensues. The results demonstrate that the cellular responses of wound healing are under separate genetic control, and that the responses are coordinated by multiple signals emanating from the wound site, including a negative feedback signal between scab formation and the JNK pathway. Cell biological and molecular parallels to vertebrate wound healing lead us to speculate that wound healing is an ancient response that has diversified during evolution.

Liposomal gene transfer of multiple genes is more effective than gene transfer of a single gene

Liposomal gene transfer is an effective therapeutic approach for the treatment of several pathophysiologic states. The purpose of the present study was to define whether gene transfer of multiple genes is a feasible approach and whether this approach would be more effective than the single transfer of cDNA. Rats were inflicted an acute wound and divided into four groups to receive weekly subcutaneous injections of liposomes plus the Lac-Z gene (0.22 microg, vehicle), or liposomes plus the insulin like-growth factor-I (IGF-I)cDNA (2.2 microg) and Lac Z gene (0.22 microg), or liposomes plus the keratinocyte growth factor (KGF) cDNA (2.2 microg) and Lac Z gene (0.22 microg), or liposomes plus the IGF-I/KGF cDNA (2.2 microg) and Lac Z gene (0.22 microg). Planimetry, immunological assays, histological and immunohistochemical techniques were used to determine molecular mechanisms after gene transfer, protein expression, dermal and epidermal regeneration. IGF-I/KGF cDNA transfer increased IGF-I and KGF protein concentration and caused concomitant cellular responses, for example,by increasing IGFBP-3, P<0.05. IGF-I/KGF cDNA gene transfer improved epidermal regeneration by exhibiting the most rapid area and linear wound re-epithelization by almost 250% compared to control and each growth factor given individually, P<0.001, which was probably due to promitogenic and antiapoptotic effects on basal keratinocytes when compared to controls, P<0.001. Dermal regeneration was improved in IGF-I/KGF cDNA-treated animals by an increased collagen deposition and morphology when compared with vehicle, IGF-I and KGF, P<0.001. IGF-I/KGF cDNA increased VEGF concentrations and thus neovascularization when compared with vehicle, IGF-I and KGF, P<0.001. In the present study, we showed that exogenous gene transfer of multiple cDNA sequences have an additive effect on intracellular and biological responses when compared to the same gene administered as a single cDNA sequence. Our findings demonstrate that gene therapy with multiple genes is feasible, and that the gene transfer of multiple genes can enhance and accelerate physiologic and biological effects.

Myofibroblast differentiation is induced in keratinocyte-fibroblast co-cultures and is antagonistically regulated by endogenous transforming growth factor-beta and interleukin-1

In wound healing epidermal-dermal interactions are known to regulate keratinocyte proliferation and differentiation. To find out how fibroblasts respond to epithelial stimuli, we characterized fibroblasts in monolayer co-culture with keratinocytes. On co-culture numerous extracellular matrix- and smooth muscle cell-associated gene transcripts were up-regulated in fibroblasts, suggesting a differentiation into myofibroblasts. Increased alpha-smooth muscle actin (alpha-SMA) protein expression in co-cultured fibroblasts started at approximately day 4, was serum-independent, but required endogenous transforming growth factor (TGF)-beta. In co-cultures, TGF-beta neutralizing monoclonal antibody strongly reduced alpha-SMA induction. Endogenous TGF-beta production and activation were increased at 24 and 48 hours, requiring, like alpha-SMA induction, close keratinocyte-fibroblast proximity. As myofibroblast differentiation only started after 4 days, we analyzed the presence of endogenous inhibitors at early time points. Blocking keratinocyte-derived interleukin (IL)-1 using IL-1 receptor antagonist, alpha-SMA expression in co-cultures was potentiated. Conversely, adding exogenous IL-1alpha completely suppressed endogenous alpha-SMA induction. In co-cultured fibroblasts strong nuclear factor-kappaB binding activity was observed from 2 hours, decreasing at 2 and 4 days, suggesting an early, IL-1-mediated inhibition of TGF-beta signaling in co-cultured fibroblasts. This biphasic differentiation event is regulated by the balance of endogenous TGF-beta and IL-1 activity and is reminiscent of myofibroblast differentiation at early and later stages of wound healing.

Inhibition by the soluble syndecan-1 ectodomains delays wound repair in mice overexpressing syndecan-1

Wound repair is a tightly regulated process stimulated by proteases, growth factors, and chemokines, which are modulated by heparan sulfate. To characterize further the role of the heparan sulfate proteoglycan syndecan-1 in wound repair, we generated mice overexpressing syndecan-1 (Snd/Snd) and studied dermal wound repair. Wound closure, reepithelialization, granulation tissue formation, and remodeling were delayed in Snd/Snd mice. Soluble syndecan-1 was increased, and shedding was prolonged in wounds from Snd/Snd mice. Excess syndecan-1 increased the elastolytic activity of wound fluids. Additionally, cells in the granulation tissue and keratinocytes at wound edges showed markedly reduced proliferation rates in Snd/Snd mice. Skin grafting experiments between Snd/Snd and control mice indicated that the slower growth rate was mainly due to a soluble factor in the Snd/Snd mouse skin. Syndecan-1 immunodepletion and further degradation experiments identified syndecan-1 ectodomain as a dominant negative inhibitor of cell proliferation. These studies indicate that shed syndecan-1 ectodomain may enhance proteolytic activity and inhibit cell proliferation during wound repair.

Bulge- and basal layer-specific expression of fibroblast growth factor-13 (FHF-2) in mouse skin

A variety of polypeptide growth factors are involved in the dynamic maintenance of the skin and hair. Here, we demonstrate the presence of high levels of fibroblast growth factor (FGF)-13 in the bulge region of hair follicles. Using real-time PCR, we found that expression of FGF-13 mRNA is comparable to, or higher than, that of other FGF known to regulate hair growth and wound healing. To gain additional insight into the function of FGF-13, we evaluated its distribution using in situ hybridization and immunohistochemical staining. Unlike other FGF, the distribution of FGF-13 mRNA and protein in adult mice was mainly restricted to cells in the bulge region of hair follicles, although lower levels were detected with less frequency in keratinocytes in the basal layer of the epidermis. FGF-13 protein was detectable in the bulge region throughout the hair growth cycle, but its distribution was especially wide during telogen and early anagen. During hair follicle morphogenesis in newborn mice, FGF-13 protein was first detected in the bulge region and basal layer keratinocytes 3 d after birth. These findings suggest that FGF-13 may play a role in regulating the function of cells in the bulge region and basal layer of the epidermis.

Down-regulation of connective tissue growth factor and type I collagen mRNA expression by connective tissue growth factor antisense oligonucleotide during experimental liver fibrosis

Transforming growth factor (TGF)-beta 1 is a major mediator of liver fibrosis. Connective tissue growth factor (CTGF) mediates TGF-beta 1 pro-fibrogenic effects in vitro, but its in vivo role is unknown. Both TGF-beta 1 and CTGF are overexpressed in hepatic stellate cells during liver fibrosis. We have used antisense oligonucleotides to examine the role of CTGF in carbon tetrachloride-induced liver fibrosis in mice. Mice received carbon tetrachloride together with CTGF or TGF-beta 1 antisense oligonucleotides for 2 weeks (preventive model), or carbon tetrachloride for 2 weeks followed by carbon tetrachloride and oligonucleotides for 2 more weeks (curative model). In both models, CTGF and TGF-beta 1 oligonucleotides decreased by more than 50 percent the mRNA expression of their targets. Type I collagen mRNA was also decreased by about 40 percent in the preventive experiment. Tissue inhibitor of matrix metalloproteinase-1 mRNA expression and fibrotic deposition evaluated by Sirius red staining were not modified in any group. In summary, our results suggest that hepatic stellate cells can be targeted in vivo with oligonucleotides, and that reducing CTGF levels can lead to a decrease in fibrogenesis as shown by the reduction in type I collagen expression. The lack of effect on fibrosis may be due to the persistence of high tissue inhibitor of matrix metalloproteinase-1 expression.

Liposome-mediated transfer of vascular endothelial growth factor cDNA augments survival of random-pattern skin flaps in the rat

Tissue engineering is an application for gene therapy that is in its infancy. We show that simple liposomal-mediated gene transfer could result in a potentially useful biological effect in the field of wound healing. cDNA encoding the 165 amino acid form of vascular endothelial growth factor complexed to commercially available liposomes was injected into rat skin 1 week before raising a random pattern 3 x 10 cm flap. The flap survival was enhanced by 14 percent, and was accomplished without accessing the arterial inflow of the territory. These results were statistically significant (p<0.002) and reproducible. No adverse effects were seen. Histological analysis of the angiogenesis localized much of the new vessel formation to the area around the hair follicles. Polymerase chain reaction amplification of extracted flap tissue confirmed the presence of the transgene.

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.

Exogenous liposomal IGF-I cDNA gene transfer leads to endogenous cellular and physiological responses in an acute wound

The purpose of the present study was to examine whether exogenous liposomal cDNA gene transfer is recognized by the cell and causes endogenous cellular and physiological responses. When administered as a protein, IGF-I is known to cause adverse side effects due to lack of cellular responses. Therefore, we used IGF-I cDNA as a vector to study cellular and physiological effects after liposomal administration to wounded skin. Sprague-Dawley rats were given a scald burn to inflict an acute wound and were divided into two groups to receive weekly subcutaneous injections of liposomes plus the Lac-Z gene (0.2 μg vehicle) or liposomes plus the IGF-I cDNA (2.2 μg) and Lac Z gene (0.22 μg). Transfection was confirmed by histochemical assays for β-galactosidase. Planimetry, immunological assays, and histological and immunohistochemical techniques were used to determine molecular mechanisms after gene transfer, protein expression, and dermal and epidermal regeneration. IGF-I cDNA transfer increased IGF-I protein expression and caused concomitant cellular responses by increasing IGF binding protein (IGFBP)-3 and decreasing IGFBP-1. IGF-I cDNA gene transfer increased keratinocyte growth factor expression and exerted promitogenic antiapoptotic effects on basal keratinocytes, thus improving epidermal regeneration. IGF-I cDNA improved dermal regeneration by an increased collagen deposition and morphology. IGF-I cDNA increased VEGF concentrations and thus neovascularization. Exogenous-administered IGF-I cDNA is recognized by the cell and leads to similar intracellular responses as the endogenous gene. Liposomal IGF-I gene transfer further leads to improved dermal and epidermal regeneration by interacting with other growth factors.

Blocking of FGFR signaling inhibits breast cancer cell proliferation through downregulation of D-type cyclins

Overexpression of fibroblast growth factor receptor (FGFR) tyrosine kinases has been found in many human breast cancers and has been associated with poor patient prognosis. In order to understand the mechanism by which FGFR mediates breast cancer cell proliferation, we used a low molecular weight compound, PD173074, that selectively inhibits FGFR tyrosine kinase activity and autophosphorylation. This potential anticancer agent caused a G1 growth arrest of MDA-MB-415, MDA-MB-453 and SUM 52 breast cancer cells. Our analyses revealed that FGFR signaling links to the cell cycle machinery via D-type cyclins. PD173074-mediated inhibition of FGFR activity caused downregulation of cyclin D1 and cyclin D2 expression, inhibition of cyclin D/cdk4 activity and, as a consequence, reduction of pRB phosphorylation. Retroviral-mediated ectopic expression of cyclin D1 prevented pRB hypophosphorylation and the cell cycle G1 block in PD173074-treated cells, suggesting a central role for D cyclins in proliferation of FGFR-driven breast cancer cells. The repression of FGFR activity caused downregulation of MAPK in MDA-MB-415 and MDA-MB-453 cells. In SUM 52 cells, both MAPK and PI3K signaling pathways were suppressed. In conclusion, results shown here describe a mechanism by which FGFR promotes proliferation of breast cancer cells.

Ribosomal S6 kinase as a mediator of keratinocyte growth factor-induced activation of Akt in epithelial cells

The keratinocyte growth factor receptor (KGFR) is a member of the fibroblast growth factor receptor (FGFR) superfamily. The proximal signaling molecules of FGFRs are much less characterized compared with other growth factor receptors. Using the yeast two-hybrid assay, we have identified ribosomal S6 kinase (RSK) to be a protein that associates with the cytoplasmic domain of the KGFR. The RSK family of kinases controls multiple cellular processes, and our studies for the first time show association between the KGFR and RSK. Using a lung-specific inducible transgenic system we have recently demonstrated protective effects of KGF on the lung epithelium and have demonstrated KGF-induced activation of the prosurvival Akt pathway both in vivo and in vitro. Here we show that a kinase inactive RSK mutant blocks KGF-induced Akt activation and KGF-mediated inhibition of caspase 3 activation in epithelial cells subjected to oxidative stress. It was recently shown that RSK2 recruits PDK1, the kinase responsible for both Akt and RSK activation. When viewed collectively, it appears that the association between the KGFR and RSK plays an important role in KGF-induced Akt activation and consequently in the protective effects of KGF on epithelial cells.

Comprehensive evaluation of ureteral healing after electrosurgical endopyelotomy in a porcine model: original report and review of the literature

PURPOSE

Endopyelotomy (EP) has yet to equal the success achieved with open dismembered pyeloplasty. To understand better the ureteral response to EP we performed a timed histopathological evaluation of the porcine ureter after Acucise (Applied Medical, Rancho Santa Margarita, California) EP.

MATERIALS AND METHODS

In 28 domestic pigs bilateral Acucise EPs were performed and bilateral 7Fr stents were placed. The kidneys, ureters and bladder were harvested after EP at 0, 1, 2, 3, 6, 12 and 18 hours, 1, 3 and 5 days, and 1, 2, 4 and 8 weeks. The stents were removed after 4 weeks. The healing area of the ureter was sectioned. Half was fixed in formalin 10%, stained and evaluated by light microscopy. The other half was frozen and reverse transcriptase-polymerase chain reaction was performed to measure steady state levels of epidermal growth factor, transforming growth factor (TGF)-alpha, TGF-beta 1, TGF-beta 2, TGF-beta 3, keratinocyte growth factor, vascular endothelial growth factor, insulin-like growth factor, platelet derived growth factor, collagen type 1, integrin and fibronectin transcript expression. Immunohistochemistry for actin, desmin and myosin expression was completed. The same studies were applied to the mid portion of the unoperated ureter.

RESULTS

Initial sealing of the ureterotomy defect was by blood clot and periureteral fat. Complete healing of the mucosa was observed at 2 weeks in animals without an associated urinoma. However, in no case did the muscle layer bridge the whole circumference of the ureter despite followup out to 8 weeks. In the operated ureter elevated expression of keratinocyte growth factor, vascular endothelial growth factor, TGF-alpha, TGF-beta 1, TGF-beta 3 and integrin was detected 2 hours after the operation and sustained for 7 to 14 days after the procedure. Immunohistochemistry revealed that most presumed myocytes seen in the defect were actually myofibroblasts. Persistent urinoma formation beyond the first few days appeared to slow the healing process.

CONCLUSIONS

Urothelium regenerated rapidly over an iatrogenic ureteral defect despite the absence of a lamina propria. Muscle cell coverage failed to occur completely at 8 weeks. In the initial 8 weeks of the healing process myofibroblasts appear to be prevalent. A persistent urinoma negatively impacts the healing process.

A crucial role for Fgfr2-IIIb signalling in epidermal development and hair follicle patterning

To understand the role Fgf signalling in skin and hair follicle development, we analysed the phenotype of mice deficient for Fgfr2-IIIb and its main ligand Fgf10. These studies showed that the severe epidermal hypoplasia found in mice null for Fgfr2-IIIb is caused by a lack of the basal cell proliferation that normally results in a stratified epidermis. Although at term the epidermis of Fgfr2-IIIb null mice is only two to three cells thick, it expresses the classical markers of epidermal differentiation and establishes a functional barrier. Mice deficient for Fgf10 display a similar but less severe epidermal hypoplasia. By contrast, Fgfr2-IIIb-/-, but not Fgf10-/-, mice produced significantly fewer hair follicles, and their follicles were developmentally retarded. Following transplantation onto nude mice, grafts of Fgfr2-IIIb-/- skin showed impaired hair formation, with a decrease in hair density and the production of abnormal pelage hairs. Expression of Lef1, Shh and Bmp4 in the developing hair follicles of Fgfr2-IIIb-/- mice was similar to wild type. These results suggest that Fgf signalling positively regulates the number of keratinocytes needed to form a normal stratified epidermis and to initiate hair placode formation. In addition, Fgf signals are required for the growth and patterning of pelage hairs.