Differential expression of the keratinocyte growth factor (KGF) and KGF receptor genes in human vascular smooth muscle cells and arteries

Primer on fibroblast growth factor 7 (FGF 7)

Fibroblast growth factor 7 (FGF7), also known as keratinocyte growth factor (KGF), is an important member of the FGF family that is mainly expressed by cells of mesenchymal origin while affecting specifically epithelial cells. Thus, FGF7 is widely expressed in diverse tissues, especially in urinary system, gastrointestinal tract (GI-tract), respiratory system, skin, and reproductive system. By interacting specifically with FGFR2-IIIb, FGF7 activates several downstream signal pathways, including Ras, PI3K-Akt, and PLCs. Previous studies of FGF7 mutants also have implicated its roles in various biological processes including development of essential organs and tissue homeostasis in adults. Moreover, more publications have reported that FGF7 and/or FGF7/FGFR2-IIIb-associated signaling pathway are involved in the progression of various heritable or acquired human diseases: heritable conditions like autosomal dominant polycystic kidney disease (ADPKD) and non-syndromic cleft lip and palate (NS CLP), where it promotes cyst formation and affects craniofacial development, respectively; acquired non-malignant diseases such as chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), mucositis, osteoarticular disorders, and metabolic diseases, where it influences inflammation, repair, and metabolic control; and tumorigenesis and malignant diseases, including benign prostatic hyperplasia (BPH), prostate cancer, gastric cancer, and ovarian cancer, where it enhances cell proliferation, invasion, and chemotherapy resistance. Targeting FGF7 pathways holds therapeutic potential for managing these conditions, underscoring the need for further research to explore its clinical applications. Having more insights into the function and underlying molecular mechanisms of FGF7 is warranted to facilitate the development of effective treatments in the future. Here, we discuss FGF7 genomic structure, signal pathway, expression pattern during embryonic development and in adult organs and mutants along with phenotypes, as well as associated diseases.

Nanomaterials for Angiogenesis in Skin Tissue Engineering

Damage to skin tissue, which causes the disorder of the patient's body homeostasis, threatens the patient's life and increases the personal and social treatment burden. Angiogenesis, a key step in the wound healing process, provides sufficient oxygen and nutrients to the wound area. However, traditional clinical interventions are not enough to stabilize the formation of the vascular system to support wound healing. Due to the unique properties and multiple functions of nanomaterials, it has made a major breakthrough in the application of medicine. Nanomaterials provide a more effective treatment to hasten the angiogenesis and wound healing, by stimulating fundamental factors in the vascular regeneration phase. In the present review article, the basic stages and molecular mechanisms of angiogenesis are analyzed, and the types, applications, and prospects of nanomaterials used in angiogenesis are detailed. Impact statement Wound healing (especially chronic wounds) is currently a clinically important issue. The long-term nonhealing of chronic wounds often plagues patients, medical systems, and causes huge losses to the social economy. There is currently no effective method of treating chronic wounds in the clinic. Angiogenesis is an important step in wound healing. Nanomaterials had properties that are not found in conventional materials, and they have been extensively studied in angiogenesis. This review article provides readers with the molecular mechanisms of angiogenesis and the types and applications of angiogenic nanomaterials, hoping to bring inspiration to overcome chronic wounds.

Therapeutic potential of growth factors in pulmonary emphysematous condition

Pulmonary emphysema is a major manifestation of chronic obstructive pulmonary disease (COPD), which is characterized by progressive destruction of alveolar parenchyma with persistent inflammation of the small airways. Such destruction in the distal respiratory tract is irreversible and irreparable. All-trans-retinoic acid was suggested as a novel therapy for regeneration of lost alveoli in emphysema. However, profound discrepancies were evident between studies. At present, no effective therapeutic options are available that allow for the regeneration of lost alveoli in emphysematous human lungs. Recently, some reports on rodent's models have suggested the beneficial effects of various growth factors toward alveolar maintenance and repair processes.

Self-assembling elastin-like peptides growth factor chimeric nanoparticles for the treatment of chronic wounds

Chronic wounds are associated with poor epidermal and dermal remodeling. Previous work has shown the efficacy of keratinocyte growth factor (KGF) in reepithelialization and elastin in dermal wound healing. Here we demonstrate the fabrication of a fusion protein comprising of elastin-like peptides and KGF. This fusion protein retains the performance characteristics of KGF and elastin as evidenced by its enhancement of keratinocyte and fibroblast proliferation. It also preserved the characteristic elastin-like peptides inverse phase transitioning allowing the recombinant protein to be expressed in bacterial hosts (such as Escherichia coli) and purified rapidly and easily using inverse temperature cycling. The fusion protein self-assembled into nanoparticles at physiological temperatures. When applied to full thickness, wounds in Lepr(db) diabetic mice these particles enhanced reepithelialization and granulation, by 2- and 3-fold respectively, when compared to the controls. The data strongly suggests that these self-assembled nanoparticles may be beneficial in the treatment of chronic wounds resulting from diabetes or other underlying circulatory conditions.

Keratinocyte growth factor promotes preadipocyte proliferation via an autocrine mechanism

Keratinocyte growth factor (KGF; also known as FGF-7) is a well-characterized paracrine growth factor for tissue growth and regeneration. However, its role in adipose tissue, which is known to undergo tremendous expansion in obesity, is virtually unknown. Given that we previously identified KGF as one of the up-regulated growth factors in adipose tissue of an early-life programmed rat model of visceral obesity, the present study was undertaken to examine the hypothesis that KGF promotes adipogenesis. Using 3T3-L1 and rat primary preadipocytes as in vitro model systems, we demonstrated that (1) KGF stimulated preadipocyte proliferation in a concentration-dependent manner with a maximal effect at 2.5 ng/ml (approximately 2-fold increase); (2) KGF mRNA was highly expressed in rat adipocytes and preadipocytes as well as 3T3-L1 cells; (3) treatment of preadipocytes with a neutralizing antibody against KGF and siRNA-mediated knockdown of KGF led to a 50% reduction in their proliferative capacity; (4) KGF activated the protein kinase Akt, and the PI3 kinase inhibitor LY294002 blocked KGF stimulation of preadipocyte proliferation; and (5) KGF did not promote differentiation of preadipocytes to mature adipocytes. Together, these results reveal adipocytes and their precursor cells as novel sites of KGF production. Importantly, they also demonstrate that KGF promotes preadipocyte proliferation by an autocrine mechanism that involves activation of the PI3K/Akt signaling pathway. Aberrant KGF expression may have consequences not only for normal adipose tissue growth but also for the pathogenesis of obesity.

FGFR2 abnormalities underlie a spectrum of bone, skin, and cancer pathologies

Fibroblast growth factor receptor (FGFR)2 is regulated on the basis of the balance of FGFs, heparan-sulfate proteoglycans, FGFR2 isoforms, endogenous inhibitors, and microRNAs. FGFR2 signals cross-talk with hedgehog, bone morphogenetic protein, and other regulatory networks. Some cases of congenital skeletal disorders with an FGFR2 mutation show skin phenotypes, including acne, cutis gyrata, and acanthosis nigricans. Gain-of-function mutations or variations of human FGFR2 occur in estrogen receptor-positive breast cancer, diffuse-type gastric cancer, and endometrial uterine cancer. Oral administration of AZD2171 or Ki23057 inhibits in vivo proliferation of cancer cells with aberrant FGFR2 activation in rodent therapeutic models. However, loss-of-function mutations of FGFR2 are reported in human melanoma. Conditional Fgfr2b knockout in the rodent epidermis leads to increased macrophage infiltration to the dermis and adipose tissue, epidermal thickening accompanied by basal-layer dysplasia and parakeratosis, and the promotion of chemically induced squamous-cell carcinoma. Dysregulation of FGFR2 results in a spectrum of bone and skin pathologies and several types of cancer.

KGF-1 for wound healing in animal models

Keratinocyte growth factor-1 (KGF-1) is a member of the fibroblast growth factor (FGF) family FGF7 and is expressed in normal and wounded skin. KGF-1 is massively produced in the early stages of the wound healing process as well as during the later remodeling process (1, 2). We have studied the effects of the electroporation of a KGF-1 plasmid into excisional wounds of different rodent models mimicking diseases known to impair the normal wound healing process. We have used a genetically diabetic mouse model and a septic rat model in our experiments, and we have shown improvement of the healing rate (92% of the wounds are healed at day 12 vs. 40% of the control), the quality of epithelialization (histological score of 3.3 vs. 1.5), and the density of new blood vessels (85% more new blood vessels in the superficial layers than that of the control) (3, 4). Considering these results, we believe we can further explore the treatment modalities for using the electroporation-assisted transfection of DNA plasmid expression vectors of growth factors to enhance cutaneous wound healing.

KGF promotes integrin alpha5 expression through CCAAT/enhancer-binding protein-beta

Keratinocyte growth factor (KGF) and alpha(5)beta(1)-integrin are not expressed in normal skin but they are both highly upregulated in the migrating epidermis during wound healing. Here we report that KGF increased alpha(5) mRNA and protein levels in epidermoid carcinoma cells and stratified bioengineered epidermis. Interestingly, KGF increased integrin alpha(5) in the basal as well as suprabasal cell epidermal layers. Promoter studies indicated that KGF-induced integrin alpha(5) promoter activation was dependent on the C/EBP transcription factor binding site. Accordingly, KGF induced sustained phosphorylation of C/EBP-beta that was dependent on activation of ERK1/2. In addition, a dominant negative form of C/EBP-beta inhibited alpha(5) promoter activity and blocking C/EBP-beta with siRNA diminished integrin alpha(5) expression. Taken together, our data indicate that KGF increased integrin alpha(5) expression by phosphorylating C/EBP-beta. Interestingly, KGF-induced upregulation of integrin alpha(5) was more pronounced in three-dimensional tissue analogues than in conventional two-dimensional culture suggesting that stratified epidermis may be useful in understanding the effects of growth factors in the local tissue microenvironment.

Keratinocyte growth factor improves repair in the injured tracheal epithelium

Keratinocyte growth factor (KGF) is a critical growth factor in lung development and is a protective agent after lung injury, although the exact mechanisms of this protective effect have not yet been elucidated. Our laboratory has shown that circulating epithelial progenitor cells can traffic to the airway and that they appear to be derived from the bone marrow. On this basis, we hypothesized that KGF and its putative receptor (KGFR) would be important to these cells. We showed that the KGFR, which is found almost exclusively on epithelial cells, was present on cells in the bone marrow and circulation of mice that identified a subpopulation of cytokeratin 5+ circulating epithelial progenitor cells (CEPC). In addition, the KGFR co-localized with a population of cytokeratin 5+ basal cells in the repairing proximal airway. Systemic administration of KGF resulted in a significant increase in mobilization of cytokeratin 5+ CEPC at 6 h after injection. Administration of KGF to mouse recipients of heterotopic syngeneic tracheal transplants resulted in protection and more rapid repair of the tracheal epithelium, with an increase in the number of CEPC in the epithelium of the airway, and this effect was abrogated by blocking CEPC with anti-CXCL12 antibodies. KGF therefore appears to be an important growth factor for local resident progenitor epithelial cell repair and for mobilization and enhanced engraftment of CEPC to the injured proximal airway epithelium.

Liposomal gene transfer of keratinocyte growth factor improves wound healing by altering growth factor and collagen expression

BACKGROUND

Growth factors affect the complex cascade of wound healing; however, interaction between different growth factors during dermal and epidermal regeneration are still not entirely defined. In the present study, we thought to determine the interaction between keratinocyte growth factor (KGF) administered as liposomal cDNA with other dermal and epidermal growth factors and collagen synthesis in an acute wound.

MATERIALS AND METHODS

Rats received an acute wound and were divided into two groups to receive weekly subcutaneous injections of liposomes plus the Lac-Z gene (0.22 microg, vehicle), or liposomes plus the KGF cDNA (2.2 microg) and Lac-Z gene (0.22 microg). Histological and immunohistochemical techniques were used to determine growth factor, collagen expression, and dermal and epidermal structure.

RESULTS

KGF cDNA increased insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein-3 (IGFBP-3), and fibroblast growth factor (FGF), decreased transforming growth factor-beta (TGF-beta), while it had no effect on platelet-derived growth factor (PDGF) levels in the wound. KGF cDNA significantly increased collagen Type IV at both the wound edge as well as the wound bed, while it had no effect on collagen Type I and III. KGF cDNA increased re-epithelialization, improved dermal regeneration, and increased neovascularization.

CONCLUSIONS

Exogenous administered KGF cDNA causes increases in IGF-I, IGF-BP3, FGF, and collagen IV and decreases TGF-beta concentration. KGF gene transfer accelerates wound healing without causing an increase in collagen I or III.

Fibroblast Growth Factor (FGF)-1, FGF2, FGF7 and FGF Receptors are Uniformly Expressed in Trophoblast Giant Cells During Restricted Trophoblast Invasion in Cows

The bovine placenta is characterized by a limited invasion of trophoblast giant cells (TGC). In contrast to mononuclear trophoblast cells (MTC), TGC are non-polarized cells, which migrate and fuse with single uterine epithelial cells throughout gestation. Fibroblast growth factors (FGF) were shown to be associated with the migratory activity of cells, cell differentiation and angiogenesis, and due to its localization in trophoblast cells were proposed as important regulating factors in hemochorial placentae of rodents and humans, and the (syn)epitheliochorial placenta of pig and sheep. Since migrating bovine TGC are of epithelial origin, but exhibit similarities to mesenchymal cells we hypothesize that the restricted trophoblast invasion in cattle is characterized by a specific FGF expression pattern. Therefore, the spatiotemporal expression of specific FGF factor:receptor pairs, either acting on cells of mesenchymal origin or on epithelial cells was examined in bovine placental tissues throughout gestation and prepartum by immunohistochemistry, semiquantitative RT-PCR and in situ hybridization. FGF1 protein was found in trophoblast, caruncular epithelium (CE) and stroma (CS), stroma of chorionic villi (SCV), and in fetal and maternal blood vessels. FGF2 signals dominated in maternal vascular endothelia (VE), immature TGC, and MTC, whereas staining in other cell types was clearly weaker. FGF7 protein was detected in fetal and maternal blood vessel as well as in immature TGC and MTC predominantly at the chorionic plate. FGFR immunoreaction was localized in immature TGC, MTC, and to a clearly lesser extent in CS, CE and fetal and maternal blood vessels. Mature TGC stained negatively for all examined factors and FGFR. The corresponding mRNAs specific for FGF1, -2, -7, total FGFR, and FGFR2 isoforms IIIb and IIIc were colocalized in immature TGC, whereas hybridization was substantially lower in CE and absent in CS, SCV and mature TGC throughout gestation, but switched to CS and VE immediately prepartum. Semiquantitative RT-PCR revealed higher mRNA levels for FGF1, FGFR, and FGFR2IIIc in cotyledons compared to caruncles (p<0.05), whereas it was the opposite with FGF2 (p<0.001). FGF7 and FGFR2IIIb mRNA levels did not differ between caruncles and cotyledons. Significant changes (p<0.05) of mRNA levels related to gestational age were found for FGF1 and FGFR2IIIc, but not for FGF2, -7, total FGFR, and FGFR2IIIb. The specific localization of all examined FGF family members in TGC suggests that TGC, apart from their classical function as producers of hormonal products, play other important roles in the regulation of bovine placentomal growth, differentiation and angiogenesis.

Role of keratinocyte growth factor in the pathogenesis of autosomal dominant polycystic kidney disease

BACKGROUND

Previous studies have shown that the expression and distribution of keratinocyte growth factor (KGF), also known as FGF-7 (fibroblast growth factor-7) or HBGF-7 (heparin-binding growth factor-7), may be implicated in kidney cyst formation and expansion. However, there are no data on KGF expression in human autosomal dominant polycystic kidney disease (ADPKD) tissue, and it is unknown whether it affects ADPKD cyst-lining epithelial cell epithelial cell proliferation.

METHODS

The expression and distribution of KGF and KGF receptor (KGFR) mRNA in ADPKD cystic and normal kidney tissues were examined using quantitative real-time polymerase chain reaction (PCR) and in situ hybridization. KGF and KGFR protein expression in the above tissues was analysed by immunohistochemistry and western blot. The effect of KGF on cyst-lining epithelial cell proliferation was assessed by MTT assay, and its effect on the cyst-lining epithelial cell cycle was analysed by flow cytometry. The effect of KGF on cyclin D1 and P21(wafl) gene expression in cyst-lining epithelial cells was also determined.

RESULTS

KGF and KGFR mRNA expression in ADPKD cysts was higher than in normal kidney tissues. KGF and KGFR protein expression was also higher in ADPKD cysts and was localized to cyst-lining epithelial cells, tubular and interstitial cells. In vitro experiments revealed that KGF promoted cyst-lining epithelial cell proliferation, and decreased the ratio of G0/G1 phase but increased that of S phase. In response to KGF, the expression of the cyclin D1 gene in cyst-lining epithelial cells increased markedly while P21(wafl) expression decreased.

CONCLUSIONS

KGF and KGFR expression was upregulated in ADPKD kidney tissues. KGF stimulated the proliferation of cyst-lining epithelial cell in vitro by regulating the expression of cyclin D1 and P21(wafl) genes. KGF may play a role in pathogenesis of ADPKD.

Regulation of endometrial fibroblast growth factor 7 (FGF-7) and its receptor FGFR2IIIb in gilts after sex steroid replacements, and during the estrous cycle and early gestation

The aim of this study was to characterize the effect of ovarian steroids and early gestation on the expression of fibroblast growth factor 7 (FGF-7) and its receptor (FGFR2IIIb) in the porcine endometrium. In Experiment 1, gilts were ovariectomized (OVX) on day 10 of the estrous cycle and treated thereafter with vehicle (VEH), progesterone (P4), estradiol benzoate (EB), or P4+EB. Days 12 and 20 cyclic gilts (C12 and C20) were used to determine the influence of physiologically low and high plasma estradiol and progesterone concentrations on their expression. In Experiment 2, the expression of FGF-7 and FGFR2IIIB was characterized on days 1 (G 1) and 12 (G 12) of gestation. FGF-7 and FGFR2IIIb mRNA were quantified by quantitative real-time RT-PCR, and localization of FGF-7 protein in steroid-treated and early pregnant gilts was performed by immunohistochemistry. VEH-gilts expressed both FGF-7 and FGFR2IIIB mRNA. We found a significant effect of EB, but no effects of P4 or P4+EB on the mRNA expression of FGF-7. FGFR2IIIb mRNA significantly decreased after the EB and combined P4+EB treatments, compared to P4 only substituted animals. Day 12 cyclic gilts showed significantly higher FGF-7 and FGFR2IIIb mRNA expression compared with day 20 gilts. Between day 1 and 12 of gestation, FGF-7 mRNA expression differed highly while FGFR2IIIb transcripts only varied significantly. FGF-7 protein was localized in endometrial epithelia, vascular smooth muscle, and the endothelium of different types of blood vessels. Staining was weak in VEH and P4 treated gilts, whereas it was prominent following EB and P4+EB. FGF-7 antibody strongly stained the luminal epithelium on day 12 of gestation. In summary, FGF-7 and FGFR2IIIb mRNA expression is regulated differently by exogenous ovarian steroids, assuming progesterone in connection with a specific amount of 17beta-estradiol, whereas the receptor seems to be inhibited by estradiol. Both transcripts coordinately increased during the progesterone dominated phase on day 12 both in cyclic and early pregnant gilts. We conclude that estradiol and progesterone are involved in the regulation of this ligand-receptor system, which might have an important role in preparing endometrial tissue for implantation in gilts.

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.

Keratinocyte growth factor-1 expression in healthy and diseased human periodontal tissues

OBJECTIVES

Keratinocyte growth factor-1 (KGF-1) is up-regulated in chronic inflammation and specifically stimulates epithelial cell proliferation by signaling through the epithelial-specific keratinocyte growth factor receptor (KGFR). We examined KGF-1 and KGFR protein and gene expression in healthy and diseased periodontal tissues.

METHODS

Tissues were collected from patients with periodontal health or disease, immediately frozen and stained for KGF-1 and KGFR protein expression. Laser capture microdissection of epithelial and connective tissue cells with reverse transcription-polymerase chain reaction (RT-PCR) examined KGF-1 and KGFR gene expression profiles and enzymatic digestion with heparitinase, chondroitinase ABC or pre-treatment with suramin examined epithelial surface molecule interactions with KGF-1.

RESULTS

In tissues collected from healthy patients, KGF-1 protein localized to areas of junctional and basal oral epithelial cells and was significantly increased in periodontal pocket epithelium (p<0.01) and in the oral epithelium (p<0.05) of disease-associated tissues. KGFR localized to the junctional and the parabasal cells of oral epithelium, with the relative staining intensity being increased in disease-associated pocket epithelium (p<0.05). Laser capture microdissection with RT-PCR confirmed KGF-1 and KGFR were specifically expressed by connective tissue and epithelium, respectively. KGF-1 localization to epithelial cells was largely eliminated by suramin pre-treatment, indicating interaction with the KGFR.

CONCLUSIONS

KGF-1 and KGFR proteins are expressed in healthy periodontal tissues but significantly increased in diseased periodontal tissues. We hypothesize up-regulation of KGF-1 and KGFR protein associated with disease regulates epithelial cell behavior associated with onset and progression of periodontal pocket formation.

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.

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.

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.

Expression of keratinocyte growth factor receptor (KGFR/FGFR2 IIIb) in vascular smooth muscle cells

Keratinocyte growth factor receptor (KGFR), also known as fibroblast growth factor receptor (FGFR)2 IIIb, is located in many types of epithelial cells and is activated by four known ligands (FGF-1, FGF-3, FGF-7 (also known as KGF) and FGF-10) that are predominantly synthesized by mesenchymal cells. In the early stage of atherosclerosis, vascular smooth muscle cells (VSMC) transform from a contractile to a synthetic phenotype, proliferate and migrate into the intima. Previously, FGF-7 mRNA expression was reported in VSMC, but KGFR mRNA was not detected. In the present study, we attempted to determine whether KGFR is localized in VSMC cultured from rat aorta and VSMC in human normal and atherosclerotic coronary arteries. Expression of KGFR mRNA and its protein was detected in cultured rat VSMC by reverse transcription-polymerase chain reaction and western blot analysis, respectively. Immunohistochemically, KGFR was localized in the VSMC of the outer layer of the media in normal human coronary arteries. Furthermore, it was localized in the VSMC of the media and thickened intima of atherosclerotic arteries. Recombinant FGF-7 and/or FGF-10 proteins stimulated the growth of cultured rat VSMC. These findings indicate that KGFR localized in VSMC may contribute to the proliferation of VSMC in normal and atherosclerotic arteries.

Keratinocyte growth factor promotes cell motility during alveolar epithelial repair in vitro

Epithelia play a key role as protective barriers, and mechanisms of repair are crucial for restoring epithelial barrier integrity, especially in the lung. Cell spreading and migration are the first steps of reepithelialization. Keratinocyte growth factor (KGF) plays a key role in lung epithelial repair and protects against various injuries. We hypothesized that KGF may protect the lung not only by inducing proliferation but also by promoting epithelial repair via enhanced epithelial cell migration. In an in vitro wound-healing model, we found that KGF enhanced wound closure by 33%. KGF acted primarily by inducing lamellipodia emission (73.2 +/- 3.9% of KGF-treated cells had lamellipodia vs 61.3 +/- 3.4% of control cells) and increasing their relative surface area (59 +/- 2.7% with KGF vs 48 +/- 2.0% in controls). KGF reduced cytoskeleton stiffness as measured by magnetic twisting cytometry and increased cell motility (5.8 +/- 0.42 microm/h with KGF vs 3.7 +/- 0.41 microm/h in controls). KGF-increased cell motility was associated with increased fibronectin deposition during wound closure and with fibronectin reorganization into fibrils at the rear of the cells. Taken together, our findings strongly suggest that KGF may promote epithelial repair through several mechanisms involved in cell migration.

Regulation of thymic epithelium by keratinocyte growth factor

Here we demonstrate that keratinocyte growth factor (KGF) and FGFR2IIIb signaling can affect development and function of thymic epithelium (TE) and that alphabeta-lineage thymocytes contribute to intrathymic levels of KGF. Thymocyte expression of KGF is developmentally regulated, being undetectable in CD3-4-8- thymocytes and expressed at highest levels by mature CD4 or CD8 thymocytes. Exposure of thymocyte-depleted fetal thymic lobes to KGF resulted in reduced thymic epithelial expression of class II major histocompatibility complex (MHC), invariant chain (Ii), and cathepsin L (CatL) molecules involved in thymocyte-positive selection and also stimulated expression of the cytokines interleukin 6 (IL-6) and thymic stromal-derived lymphopoietin (TSLP), while having little effect on IL-7 or stem cell factor expression. Within intact fetal thymic organ culture (FTOC), exogenous KGF impairs the generation of CD4 thymocytes. Two lines of evidence point to responsiveness of the medullary TE compartment to KGF and FGFR2IIIb signaling. First, the medullary compartment is expanded in intact FTOC exposed to KGF in vitro. Second, in the RAG-deficient thymus, where the thymocytes do not express detectable levels of KGF message, the hypoplastic medullary TE compartment can be expanded by administration of recombinant KGF in vivo. This expansion is accompanied by restoration of the normal profile of medullary TE-associated chemokine expression in the RAG2(-/-) thymus. Collectively, these findings point to a role for KGF and FGFR signaling in the development and function of thymic epithelium.

Non-viral liposomal keratinocyte growth factor (KGF) cDNA gene transfer improves dermal and epidermal regeneration through stimulation of epithelial and mesenchymal factors

Keratinocyte growth factor (KGF) stimulates epithelial cell differentiation and proliferation, which are of major importance for wound healing. Local protein administration, however, has been shown to be ineffective due to enzymes and proteases in the wound fluid. We hypothesized that delivering KGF as a non-viral liposomal cDNA gene complex is a new approach that would effectively enhance dermal and epidermal regeneration. Twenty-two rats were given an acute wound and divided into two groups to receive weekly subcutaneous injections of liposomes plus the LacZ gene (0.2 microg, vehicle), or liposomes plus the KGF cDNA (2.2 microg) and LacZ cDNA (0.2 microg). Transfection was confirmed by histochemical assays for beta-galactosidase. Planimetry, histological and immunohistochemical techniques were used to determine protein expression, dermal and epidermal regeneration. Transfection and subsequent KGF expression was found in diving cells in the granulation tissue. Epidermal regeneration was improved by 170% in rats receiving the KGF cDNA constructs by exhibiting the most rapid area and linear wound re-epithelialization, P < 0.0001. KGF improved epidermal cell net balance by increasing skin cell proliferation and decreasing skin cell apoptosis, P < 0.0001. Dermal regeneration was further improved in KGF cDNA treated animals by an increased collagen deposition and morphology, P < 0.0001. KGF cDNA increased neo-vascularization and concomitant VEGF concentrations when compared with vehicle, P < 0.01. KGF cDNA did not only stimulate epithelial cells, but also mesenchymal cells through increases in IGF-I concentration, P < 0.005. Liposomes containing the KGF cDNA gene constructs were effective in improving epidermal and dermal regeneration. KGF gene transfer to acute wounds may represent a new therapeutic strategy to enhance wound healing.

Esophageal ulceration activates keratinocyte growth factor and its receptor in rats: implications for ulcer healing

BACKGROUND & AIMS

Cellular and molecular mechanisms of esophageal ulcer healing remain unexplored. We studied the sequential cellular events and the expression of keratinocyte growth factor (KGF) and its receptor (KGF-R) during the healing of experimental esophageal ulcers.

METHODS

Esophageal ulcers were produced in rats by local application of acetic acid. Studies included (1) ulcer size, (2) quantitative histology, and (3) KGF and KGF-R messenger RNA and protein expression by reverse-transcription polymerase chain reaction, Western blotting, and immunostaining. In separate groups, ulcer size and esophageal epithelial proliferation were evaluated after a single injection of recombinant human KGF (1 mg/kg) around the ulcer.

RESULTS

Ulcers were fully developed 3 days after induction, and 58% of ulcers were re-epithelialized by 9 days. At 3 days, in esophageal tissue bordering the ulcers, KGF messenger RNA and protein were increased by 191% and 151%, respectively, and KGF-R messenger RNA and protein were increased by 357% and 237%, respectively. KGF was expressed in stromal cells, whereas KGF-R was expressed in epithelial cells. At 6 days, epithelial proliferation at the ulcer margin was increased by 216%, and treatment with KGF further enhanced cell proliferation and accelerated ulcer healing.

CONCLUSIONS

KGF is a likely mediator of esophageal epithelial proliferation and ulcer healing.

Therapeutic success and efficacy of nonviral liposomal cDNA gene transfer to the skin in vivo is dose dependent

It is well documented that responses to growth factor treatment typically display bell-shaped dose responses that can significantly affect efficacy. Here we tested the hypothesis that nonviral liposomal gene delivery also displays this characteristic. We chose two different growth factors, keratinocyte growth factor (KGF) and insulin-like growth factor-I (IGF-I) CMV-driven transfecting constructs at three different concentrations and assessed efficacy on several physiological parameters that are descriptive of wound healing progress in a burn-wound healing model. Rats were given a 60% TBSA scald burn and randomly divided into one of seven groups to receive weekly subcutaneous injections of liposomes containing the cDNA for KGF (0.2 microg, 2.2 microg, or 22.2 microg), or liposomes containing the cDNA for IGF-I (0.2 microg, 2.2 microg, or 22.2 microg) at various concentrations, but constant liposome:DNA ratios and a LacZ gene (0.2 microg) CMV-driven construct for beta-galactosidase as vehicle and marker gene. Transfection was confirmed by histology for beta-galactosidase. Physiological efficacy was evaluated by measuring the wound healing parameters that define dermal and epidermal regeneration. Transfection products were found in the cytoplasm of rapidly dividing cells of the granulation tissue. Different doses of the nonviral cDNA gene transfer coding for KGF or IGF-I resulted in different outcomes for dermal and epidermal regeneration. There was a dose-dependent response to both growth factor gene transfers that was not dissimilar from that typically displayed by treatment with growth factor proteins. Both concentrations below and above the optimal concentration of DNA:liposomal preparations did not yield the results observed at the optimal concentration.

Keratinocyte growth factor attenuates hydrostatic pulmonary edema in an isolated, perfused rat lung model

Hydrostatic pulmonary edema is a common complication of congestive heart failure, resulting in substantial morbidity and mortality. Keratinocyte growth factor (KGF) is a mitogen for type II alveolar epithelial and microvascular cells. We utilized the isolated perfused rat lung model to produce hydrostatic pulmonary edema by varying the left atrial and pulmonary capillary pressure. Pretreatment with KGF attenuated hydrostatic edema formation. This was demonstrated by lower wet-to-dry lung weight ratios, histological evidence of less alveolar edema formation, and reduced alveolar accumulation of intravascularly administered FITC-labeled large-molecular-weight dextran in rats pretreated with KGF. Thus KGF attenuates injury in this ex vivo model of hydrostatic pulmonary edema via mechanisms that prevent increases in alveolar-capillary permeability.

Keratinocyte growth factor facilitates alloengraftment and ameliorates graft-versus-host disease in mice by a mechanism independent of repair of conditioning-induced tissue injury

We have previously shown that pretreatment of mice with keratinocyte growth factor (KGF), an epithelial tissue repair factor, can ameliorate graft-versus-host disease (GVHD) after intensive chemoradiotherapeutic conditioning and allogeneic bone marrow transplantation (BMT). To determine whether this effect was dependent on a KGF-mediated mechanism affecting repair of conditioning-induced epithelial cell injury, we studied GVHD in the absence of conditioning using BALB/c severe combined immune-deficient (SCID) recipients given C57BL/6 T cells. KGF (5 mg/kg per day, subcutaneously) given either before or after T-cell transfer enhanced body weights and extended survival. KGF-treated recipients had elevated serum levels of the Th2 cytokine interleukin 13 (IL-13) on day 6 after T-cell transfer concomitant with reduced levels of the inflammatory cytokines tumor necrosis factor-α (TNF-α) and interferon gamma (IFN-γ). A 3-day KGF pretreatment also depressed the secondary in vitro mixed lymphocyte response (MLR) of C57BL/6 splenocytes taken 7 days after in vivo alloimmunization with irradiated BALB/c spleen cells. To determine whether KGF would inhibit host-antidonor–mediated BM rejection, pan-T-cell–depleted BALB/c BM cells were infused into sublethally irradiated C57BL/6 mice and administered KGF either before or before and after BMT. Surprisingly, all KGF schedules tested actually resulted in enhanced alloengraftment. The presence of KGF receptor on donor antihost alloreactive T cells could not be detected by binding studies with radiolabeled KGF, reverse transcriptase–polymerase chain reaction, and Western blotting. Therefore, the mechanism of action of KGF on inhibiting T-cell–mediated immune effects may not be due to a direct effect of KGF on T cells. These studies demonstrate that KGF, by mechanisms independent of repair of conditioning-induced injury, has great potential as an anti-GVHD therapeutic agent with the added benefit of inhibiting the rejection of pan-T-cell–depleted donor BM allografts.

Keratinocyte growth factor facilitates alloengraftment and ameliorates graft-versus-host disease in mice by a mechanism independent of repair of conditioning-induced tissue injury

We have previously shown that pretreatment of mice with keratinocyte growth factor (KGF), an epithelial tissue repair factor, can ameliorate graft-versus-host disease (GVHD) after intensive chemoradiotherapeutic conditioning and allogeneic bone marrow transplantation (BMT). To determine whether this effect was dependent on a KGF-mediated mechanism affecting repair of conditioning-induced epithelial cell injury, we studied GVHD in the absence of conditioning using BALB/c severe combined immune-deficient (SCID) recipients given C57BL/6 T cells. KGF (5 mg/kg per day, subcutaneously) given either before or after T-cell transfer enhanced body weights and extended survival. KGF-treated recipients had elevated serum levels of the Th2 cytokine interleukin 13 (IL-13) on day 6 after T-cell transfer concomitant with reduced levels of the inflammatory cytokines tumor necrosis factor-α (TNF-α) and interferon gamma (IFN-γ). A 3-day KGF pretreatment also depressed the secondary in vitro mixed lymphocyte response (MLR) of C57BL/6 splenocytes taken 7 days after in vivo alloimmunization with irradiated BALB/c spleen cells. To determine whether KGF would inhibit host-antidonor–mediated BM rejection, pan-T-cell–depleted BALB/c BM cells were infused into sublethally irradiated C57BL/6 mice and administered KGF either before or before and after BMT. Surprisingly, all KGF schedules tested actually resulted in enhanced alloengraftment. The presence of KGF receptor on donor antihost alloreactive T cells could not be detected by binding studies with radiolabeled KGF, reverse transcriptase–polymerase chain reaction, and Western blotting. Therefore, the mechanism of action of KGF on inhibiting T-cell–mediated immune effects may not be due to a direct effect of KGF on T cells. These studies demonstrate that KGF, by mechanisms independent of repair of conditioning-induced injury, has great potential as an anti-GVHD therapeutic agent with the added benefit of inhibiting the rejection of pan-T-cell–depleted donor BM allografts.

Keratinocyte growth factor induces angiogenesis and protects endothelial barrier function

Keratinocyte growth factor (KGF), also called fibroblast growth factor-7, is widely known as a paracrine growth and differentiation factor that is produced by mesenchymal cells and has been thought to act specifically on epithelial cells. Here it is shown to affect a new cell type, the microvascular endothelial cell. At subnanomolar concentrations KGF induced in vivo neovascularization in the rat cornea. In vitro it was not effective against endothelial cells cultured from large vessels, but did act directly on those cultured from small vessels, inducing chemotaxis with an ED50 of 0.02-0.05 ng/ml, stimulating proliferation and activating mitogen activated protein kinase (MAPK). KGF also helped to maintain the barrier function of monolayers of capillary but not aortic endothelial cells, protecting against hydrogen peroxide and vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) induced increases in permeability with an ED50 of 0.2-0.5 ng/ml. These newfound abilities of KGF to induce angiogenesis and to stabilize endothelial barriers suggest that it functions in microvascular tissue as it does in epithelial tissues to protect them against mild insults and to speed their repair after major damage.

Genomic structure, mapping, activity and expression of fibroblast growth factor 17

Fibroblast growth factors are essential molecules for development. Here we characterize Fgfl7, a new member of the fibroblast growth factor (FGF) family. The Fgfl7 gene maps to mouse chromosome 14 and is highly conserved between mouse and human (93% identity). It exhibits 60% amino acid identity with Fgf8 and 50% identity with Fgf8. Both Fgf8 and Fgf17 have a similar structure and a similar pattern of alternative splicing in the 5' coding region. When expressed in 3T3 fibroblasts, mouse FGF17 is transforming, indicating that it can activate the 'c' splice form of either FGF receptor (FGFR) one or two. During midgestation embryogenesis, in situ hybridization analysis localized Fgf17 expression to specific sites in the midline structures of the forebrain, the midbrain-hindbrain junction, the developing skeleton and in developing arteries. Comparison to Fgf8 revealed a striking similarity in expression patterns, especially in the central nervous system (CNS), suggesting that both genes may be important for CNS development, although Fgf17 is expressed somewhat later than Fgf8. In the developing skeleton, both genes are expressed in costal cartilage while Fgf8 is preferentially expressed in long bones. In the developing great vessels Fgfl7 is preferentially expressed, suggesting that it may have a more prominent role in vascular growth.

Keratinocyte growth factor: a unique player in epithelial repair processes

Keratinocyte growth factor (KGF) is a member of the rapidly growing fibroblast growth factor (FGF) family of mitogens. Whereas most FGFs influence proliferation and/or differentiation of various cell types, KGF seems to act specifically on epithelial cells. It has been demonstrated that KGF stimulates proliferation and migration of these cells, but it also affects differentiation processes. Finally, recent studies have demonstrated a protective function of this growth factor in vitro and in vivo. Due to these properties, KGF could play an important role in repair processes. Indeed a series of studies have provided insight into the expression and function of KGF in inflammation and repair of various tissues and organs, and a therapeutic potential of this growth factor has been demonstrated.