Keratinocyte Growth Factor Secretion Research Articles

ISX-9 Promotes KGF Secretion From MSCs to Alleviate ALI Through NGFR-ERK-TAU-β-Catenin Signaling Axis.

Mesenchymal stem cells (MSCs) have been widely studied to alleviate acute lung injury (ALI) due to their paracrine function. However, the microenvironment of inflammatory outbreaks significantly restricted the factors secreted from MSCs like keratinocyte growth factor (KGF). KGF is a growth factor with tissue-repaired ability. Is there a better therapeutic prospect for MSCs in combination with compounds that promote their paracrine function? Through compound screening, we screened out isoxazole-9 (ISX-9) to promote MSCs derived KGF secretion and investigated the underlying mechanisms of action. Compounds that promote KGF secretion were screened by a dual-luciferase reporter gene assay. The TMT isotope labeling quantitative technique was used to detect the differential proteins upon ISX-9 administrated to MSCs. The expressions of NGFR, ERK, TAU, and β-catenin were detected by Western blot. In the ALI model, we measured the inflammatory changes by HE staining, SOD content detection, RT-qPCR, immunofluorescence, etc. The influence of ISX-9 on the residence time of MSCs transplantation was explored by optical in vivo imaging. We found out that ISX-9 can promote the expression of KGF in MSCs. ISX-9 acted on the membrane receptor protein NGFR, upregulated phosphorylation of downstream signaling proteins ERK and TAU, downregulated phosphorylation of β-catenin, and accelerated β-catenin into the nucleus to further increase the expression of KGF. In the ALI model, combined ISX-9 with MSCs treatments upgraded the expression of KGF in the lung, and enhanced the effect of MSCs in reducing inflammation and repairing lung damage compared with MSCs alone. ISX-9 facilitated the secretion of KGF from MSCs both in vivo and in vitro. The combination of ISX-9 with MSCs enhanced the paracrine function and anti-inflammatory effect of MSCs compared with MSCs applied alone in ALI. ISX-9 played a contributive role in the transplantation of MSCs for the treatment of ALI.

Coculture with bone marrow‑derived mesenchymal stem cells attenuates inflammation and apoptosis in lipopolysaccharide‑stimulated alveolar epithelial cells via enhanced secretion of keratinocyte growth factor and angiopoietin‑1 modulating the Toll‑like receptor‑4 signal pathway.

Acute lung injury (ALI) is a common, costly and potentially lethal disease with characteristics of alveolar‑capillary membrane disruption, pulmonary edema and impaired gas exchange due to increased apoptosis and pulmonary inflammation. There is no effective and specific therapy for ALI; however, mesenchymal stem cells (MSCs) have been demonstrated to be a potential option. Lipopolysaccharide (LPS) is a highly proinflammatory molecule that is used to mimic an invivo inflammatory and damaged state invitro. The present study investigated the effect of bone marrow‑derived MSCs on an LPS‑induced alveolar epithelial cell (A549cell line) injury and its underlying mechanisms by a Transwell system. It was identified that a high LPS concentration caused a decrease in cell viability, increases in apoptosis, inflammatory cytokine release and NF‑κB activity, disruption of the caspase‑3/Bcl‑2 ratio, upregulation of Toll‑like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88) and toll‑interleukin‑1 receptor domain‑containing adaptor inducing interferon (TRIF) expression, and facilitation of TLR4/MyD88 and TLR4/TRIF complex formation in A549 cells. Coculture with MSCs attenuated all of these activities induced by LPS in A549 cells. In addition, an increased level of keratinocyte growth factor (KGF) and angiopoietin‑1 (ANGPT1) secretion from MSCs was observed under inflammatory stimulation. KGF and/or ANGPT1 neutralizing antibodies diminished the beneficial effect of MSC conditioned medium. These data suggest that MSCs alleviate inflammatory damage and cellular apoptosis induced by LPS in A549 cells by modulating TLR4 signals. These changes may be partly associated with an increased secretion of KGF and ANGPT1 from MSCs under inflammatory conditions. These data provide the basis for development of MSC‑based therapies for ALI.

Therapeutic Effects of Human Mesenchymal Stem Cell-derived Microvesicles in Severe Pneumonia in Mice.

Microvesicles (MVs) are anuclear fragments of cells released from the endosomal compartment or shed from surface membranes. We and other investigators demonstrated that MVs released by mesenchymal stem cells (MSCs) were as effective as the cells themselves in inflammatory injuries, such as after endotoxin-induced acute lung injury. However, the therapeutic effects of MVs in an infectious model of acute lung injury remain unknown. We investigated the effects of human MSC MVs on lung inflammation, protein permeability, bacterial clearance, and survival after severe bacterial pneumonia. We tested the effects of MVs derived from human MSCs on Escherichia coli pneumonia in mice. We also studied the interactions between MVs and human monocytes and human alveolar epithelial type 2 cells. Administration of MVs derived from human MSCs improved survival in part through keratinocyte growth factor secretion and decreased the influx of inflammatory cells, cytokines, protein, and bacteria in mice injured with bacterial pneumonia. In primary cultures of human monocytes or alveolar type 2 cells, the uptake of MVs was mediated by CD44 receptors, which were essential for the therapeutic effects. MVs enhanced monocyte phagocytosis of bacteria while decreasing inflammatory cytokine secretion and increased intracellular ATP levels in injured alveolar epithelial type 2 cells. Prestimulation of MSCs with a toll-like receptor 3 agonist further enhanced the therapeutic effects of the released MVs. MVs derived from human MSCs were as effective as the parent stem cells in severe bacterial pneumonia.

KGFR as a possible therapeutic target in middle ear cholesteatoma

Conclusion: We demonstrated that repression of keratinocyte growth factor (KGF) receptor (KGFR) could be a potentially useful strategy in the conservative treatment of middle ear cholesteatoma. Objectives: Recently, the use of a selective inhibitor of the KGFR, SU5402, in an in vitro experiment resulted in the inhibition of the differentiation and proliferation of epithelial cells through KGF secretion by fibroblasts isolated from the cholesteatoma. In this study, we investigated the effects of the KGFR inhibitor during middle ear cholesteatoma formation in vivo. Methods: Based on the role of KGF in the development of cholesteatoma, Flag-hKGF cDNA driven by CMV14 promoter was transfected through electroporation into the external auditory canal of rats five times on every fourth day. Ears transfected with empty vector were used as controls. KGFR selective inhibitor (SU5402) or MEK inhibitor (PD0325901) was administered in the right ear of five rats after vector transfection. In the control, 2% DMSO in PBS was administered in the other ears after vector transfection. Results: The use of a selective KGFR inhibitor, SU5402, completely prevented middle ear cholesteatoma formation in the rats.

KGF, FGFb, VEGF, HGF and TGFβ1 secretion of human keratocytes following photodynamic inactivation (PDI) in vitro

With increasing resistance of microorganisms to antibiotics, photodynamic inactivation (PDI) may be a potential treatment alternative for infectious keratitis. Growth factors have the function to regulate proliferation, apoptosis and motility of the cells, and thereby affect wound healing. The purpose of this study was to evaluate the possible impact of PDI on the secretion of keratinocyte growth factor (KGF), fibroblast growth factor beta (FGFb), vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF) and transforming growth factor β1 (TGFβ1) of human keratocytes, in vitro. Primary human keratocytes were isolated by digestion in collagenase A (1.0 mg/ml) from human corneal buttons, and cultured in DMEM/Ham's F12 medium supplemented with 10% FCS. Keratocyte cell cultures underwent illumination using red (670 nm) light for 13 min following exposure to 100 nM concentration of the photosensitizer chlorin e6 (Ce6) in culture medium. Five hours and 24 hours after PDI, secretion of KGF, FGFb, VEGF, HGF and TGFβ1 was measured by enzyme-linked immunoabsorbent assay (ELISA). Compared to untreated controls, FGFb secretion of keratocytes increased (p < 0.0001) and HGF expression decreased (p < 0.01) significantly 5 hours after PDI, whereas KGF, VEGF, and TGFβ1 secretion remained unchanged. Twenty-four hours following PDI, KGF secretion decreased (p < 0.0001) significantly, while FGFb, HGF, VEGF and TGFβ1 concentrations did not differ markedly from untreated controls. Photodynamic inactivation triggers FGFb and inhibits HGF secretion of keratocytes transiently (5 hours) and inhibits KGF secretion 24 hours following treatment. In the short term, PDI does not have an impact on VEGF and TGFβ1 secretion of keratocytes, in vitro.

Therapeutic Effects of Human Mesenchymal Stem Cells in Ex Vivo Human Lungs Injured with Live Bacteria

Mesenchymal stem cells secrete paracrine factors that can regulate lung permeability and decrease inflammation, making it a potentially attractive therapy for acute lung injury. However, concerns exist whether mesenchymal stem cells' immunomodulatory properties may have detrimental effects if targeted toward infectious causes of lung injury. Therefore, we tested the effect of mesenchymal stem cells on lung fluid balance, acute inflammation, and bacterial clearance. We developed an Escherichia coli pneumonia model in our ex vivo perfused human lung to test the therapeutic effects of mesenchymal stem cells on bacterial-induced acute lung injury. Clinical-grade human mesenchymal stem cells restored alveolar fluid clearance to a normal level, decreased inflammation, and were associated with increased bacterial killing and reduced bacteremia, in part through increased alveolar macrophage phagocytosis and secretion of antimicrobial factors. Keratinocyte growth factor, a soluble factor secreted by mesenchymal stem cells, duplicated most of the antimicrobial effects. In subsequent in vitro studies, we discovered that human monocytes expressed the keratinocyte growth factor receptor, and that keratinocyte growth factor decreased apoptosis of human monocytes through AKT phosphorylation, an effect that increased bacterial clearance. Inhibition of keratinocyte growth factor by a neutralizing antibody reduced the antimicrobial effects of mesenchymal stem cells in the ex vivo perfused human lung and monocytes grown in vitro injured with E. coli bacteria. In E. coli-injured human lungs, mesenchymal stem cells restored alveolar fluid clearance, reduced inflammation, and exerted antimicrobial activity, in part through keratinocyte growth factor secretion.

Effect of nifedipine on the expression of keratinocyte growth factor and its receptor in cocultured/monocultured fibroblasts and keratinocytes

Keratinocyte growth factor (KGF) and its receptor (KGFR) are involved in hyperplastic diseases. This study explored the effect of intercellular communication on KGF and KGFR in cocultured/monocultured gingival fibroblasts and keratinocytes following treatment with nifedipine. Human gingival fibroblasts and keratinocytes were monocultured and cocultured, respectively. MTT was used to investigate the effects of nifedipine on the proliferation of gingival fibroblasts and keratinocytes. Monoculture and coculture systems were treated with different concentrations (0, 0.2 or 20μg/mL) of nifedipine, and the expression of KGF and KGFR mRNAs was examined by RT-PCR, whilst the secretion of KGF and the expression of KGFR on the membrane were analyzed using ELISA and flow cytometry, respectively. Nifedipine (0, 0.2 and 20μg/mL) had no influence on cell proliferation within 3d. KGF and KGFR mRNAs were up-regulated, but only in the cocultures. In coculture, the secretion of KGF was significantly increased by nifedipine, while it was only significantly up-regulated by 20μg/mL of nifedipine in monoculture. Moreover, the level of KGFR protein in the membrane was significantly increased by 20μg/mL of nifedipine in monocultures, while it was significantly down-regulated by 20μg/mL of nifedipine in cocultures. The expression of KGF and KGFR are influenced by the interplay of gingival keratinocytes and fibroblasts. Epithelial keratinocytes and mesenchymal fibroblasts may interplay to dynamically regulate gene expression, which may have an effect on the gingival condition following treatment with nifedipine.

Organic components from scallop shell increase expression of keratinocyte growth factor in human skin fibroblast

We observed previously that scallop shells contain organic components that have various useful applications for skin. The organic components from scallop shell (scallop shell extract) enhance the turnover rate of the rat skin epidermal layer and increase the rate of recovery of UVB-induced injury to rat dorsal skin. We investigated the effect of scallop shell extract on the expression of keratinocyte growth factor (KGF) from human skin fibroblasts because it has been reported that KGF promotes wound healing and reduces the generation of UVB-induced free radicals in skin. Scallop shell extract increased the mRNA expression level of KGF in skin fibroblasts and the secretion of KGF from the fibroblasts at the protein level. These results suggest that the scallop shell extract may promote recovery from UVB-induced injury in skin through an increase in the secretion of KGF from the fibroblast cell.

Effect of Mitomycin C on IL-1R Expression, IL-1–Related Hepatocyte Growth Factor Secretion and Corneal Epithelial Cell Migration

To investigate how mitomycin C (MMC) modulates hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) secretions in human corneal fibroblasts and regulates human corneal epithelial (HCE) cell migration. Primary human corneal fibroblasts were treated with MMC (0.05, 0.1, or 0.2 mg/mL for 5 minutes) and were cultivated with or without interleukin (IL)-1beta. Transcript and secretion of HGF and KGF were determined by quantitative real-time RT-PCR and Western blot analysis, respectively. The effect of MMC-treated fibroblasts on HCE cell migration was evaluated using a transwell migration assay. The influence of MMC on HGF expression/secretion and HCE cell migration was further confirmed by RNA interference. The number of IL-1 receptors (IL-1R) on the fibroblast surface was analyzed by flow cytometry. MMC alone did not affect endogenous HGF expression, whereas IL-1beta alone significantly upregulated HGF transcripts and secretion. By modifying IL-1R numbers, MMC further upregulated IL-1beta-related HGF expression at a concentration of 0.05 mg/mL but to a lesser extent at 0.1 and 0.2 mg/mL. KGF transcripts and intracellular expression were suppressed by MMC dose dependently in the presence or absence of IL-1beta, whereas KGF secretion was not affected. Conditioned medium from MMC-treated fibroblasts exerted a similar concentration-dependent effect on HCE cell migration, enhancing migration most significantly at 0.05 mg/mL MMC in the presence of IL-1beta. The MMC dose-dependent modulation of HCE cell migration was abolished in HGF-silenced fibroblasts. MMC differentially modulated IL-1R expression at various concentrations and regulated HGF and KGF differently. MMC alone did not alter HGF expression. In the presence of IL-1beta, MMC-treated corneal fibroblasts modified HCE cell migration through IL-1beta-induced HGF secretion.

Allogeneic human mesenchymal stem cells for treatment of E. coli endotoxin-induced acute lung injury in the ex vivo perfused human lung

Recent studies have suggested that bone marrow-derived multipotent mesenchymal stem cells (MSCs) may have therapeutic applications in multiple clinical disorders including myocardial infarction, diabetes, sepsis, and hepatic and acute renal failure. Here, we tested the therapeutic capacity of human MSCs to restore alveolar epithelial fluid transport and lung fluid balance from acute lung injury (ALI) in an ex vivo perfused human lung preparation injured by E. coli endotoxin. Intra-bronchial instillation of endotoxin into the distal airspaces resulted in pulmonary edema with the loss of alveolar epithelial fluid transport measured as alveolar fluid clearance. Treatment with allogeneic human MSCs or its conditioned medium given 1 h following endotoxin-induced lung injury reduced extravascular lung water, improved lung endothelial barrier permeability and restored alveolar fluid clearance. Using siRNA knockdown of potential paracrine soluble factors, secretion of keratinocyte growth factor was essential for the beneficial effect of MSCs on alveolar epithelial fluid transport, in part by restoring amiloride-dependent sodium transport. In summary, treatment with allogeneic human MSCs or the conditioned medium restores normal fluid balance in an ex vivo perfused human lung injured by E. coli endotoxin.

Allogeneic human mesenchymal stem cells for treatment of E. Coli endotoxin‐induced acute lung injury in an ex vivo perfused human lung

Recent studies have indicated that bone marrow derived mesenchymal stem cells (MSC) may have therapeutic applications in multiple clinical disorders. Currently, little is known regarding the effect of MSC in experimental models of acute lung injury (ALI) and pulmonary edema. We recently reported that intrapulmonary (via the trachea) treatment with MSC 4 h after endotoxin delivery to the lung improved survival and reduced the extent of pulmonary edema formation in endotoxin‐induced ALI in mice (J Immunol 2007). Here, we tested the therapeutic potential of human MSC to resolve pulmonary edema from ALI in an ex vivo perfused human lung preparation injured by E. Coli endotoxin. Intra‐bronchial instillation of endotoxin resulted in the loss of alveolar epithelial fluid transport measured as alveolar fluid clearance (AFC). Instillation of allogeneic human MSC or its conditioned medium given 1 h following endotoxin‐induced lung injury completely restored AFC. Using siRNA knockdown of potential paracrine soluble factors, we found that the secretion of keratinocyte growth factor (KGF) was essential for the restorative effect of MSC. In summary, the therapeutic effect of allogeneic human MSC on the resolution of endotoxin‐induced pulmonary edema in an ex vivo perfused human lung was mediated by the secretion of KGF. FAER &amp; NHLBI HL093026, HL51854 and HL51856.

Synthesis and assessment of a novel peptide conjugate to deliver phenytoin for wound repair

Crude preparations containing phenytoin, a medication used clinically as an anti-convulsant for epilepsy, have been shown to accelerate wound healing in both animals and humans. We hypothesized that a phenytoin-octa( l -arginine) conjugate, lysed in wound exudate would release phenytoin to produce improved healing while the arginine moiety would form nitric oxide inducing angiogenesis and cell proliferation. In addition, the expected increase in solubility of this new chemical entity would facilitate formulation and increase phenytoin availability at the receptor targets. Following synthesis of the conjugate molecule, its effect on Keratinocyte Growth Factor secretion by cultured human gingival fibroblasts was examined. Gel preparations containing phenytoin and the phenytoin-octa( l -arginine) conjugate were then applied to a diabetic wound model and wound healing parameters were measured. Results indicate that this novel compound demonstrates equivalent efficacy to phenytoin alone at a considerably lower phenytoin dose. The improved wound repair apparent here as well as the increased solubility give the phenytoin-octa( l -arginine) conjugate an advantage over previously examined phenytoin preparations.

Selective cyclooxygenase‐2 inhibitor downregulates the paracrine epithelial–mesenchymal interactions of growth in scirrhous gastric carcinoma

The importance of cancer-mesenchymal interactions in the aggressive behavior of scirrhous gastric cancer is supported by experimental and clinical evidences. We have previously reported that gastric fibroblasts secretion of keratinocyte growth factor (KGF) underline the remarkable proliferation of scirrhous gastric cancer cells. Cyclooxygenase-2 (COX-2) is not only expressed in cancer cells, but also in interstitial fibroblasts in gastric carcinoma. To clarify the mechanisms responsible for the antiproliferation effect of COX-2 inhibitors, effect of COX-2 inhibitor on the paracrine epithelial-mesenchymal interactions of growth was examined. Scirrhous gastric cancer cell line, OCUM-2M, gastric fibroblasts, NF-21, and COX-2 inhibitor, JTE-522, were used. Growth-interaction was examined by calculating the number of cancer cells or by measuring [(3)H] thymidine incorporation of cancer cells. Effect of JTE-522 on KGF expression from NF-21 cells and OCUM-2M cells was analyzed by ELISA and RT-PCR. The conditioned medium from gastric fibroblasts significantly stimulated the growth of scirrhous gastric cancer cells. JTE-522 at the concentrations of 10(-5) and 10(-6) M significantly decreased the growth-stimulating activity of gastric fibroblasts. JTE-522 reduced the expression of KGF mRNA and the production of KGF from gastric fibroblasts. Oral administration of JTE-522 significantly decreased the size of xenografted tumor coinoculated with OCUM-2M cells and NF-21 cells in nude mice. JTE-522 decreased COX-2 expression and Ki67 labeling index within the coinoculated tumor. These findings suggested that a selective COX-2 inhibitor, JTE-522, downregulates KGF production from gastric fibroblasts, resulting in the inhibition of paracrine epithelial-mesenchymal interactions of proliferation between scirrhous gastric cancer cells and gastric fibroblasts.

Keratinocyte Growth Factor Expression by Fibroblasts in Pulmonary Fibrosis

Keratinocyte growth factor (KGF) is secreted by fibroblasts and protects from pulmonary fibrosis in animal models. Interleukin (IL)-1beta is the most potent inducer of KGF in fibroblasts, acting through the c-Jun pathway. We evaluated in vitro KGF production by human lung fibroblasts from patients with idiopathic pulmonary fibrosis (IPF, n = 10) and from control subjects (n = 7) at baseline and after IL-1beta stimulation. Basal KGF secretion by IPF fibroblasts was similar to controls. In fibroblasts from control subjects, IL-1beta increased c-Jun expression, c-Jun activation, and KGF secretion. SP600125, a specific c-Jun N-terminal kinase (JNK) inhibitor, inhibited the effect of IL-1beta. By contrast, in IPF fibroblasts, IL-1beta did not increase c-Jun expression and c-Jun activation, and weakly increased KGF secretion, whereas SP600125 had no effect. IL-1beta similarly increased JunB expression in fibroblasts from patients with IPF and control subjects. Total JNK content was not different in either unstimulated or IL-1beta-stimulated IPF and control fibroblasts. IL-1beta increased phosphorylated JNK in control and IPF fibroblasts, but this increase was weaker and heterogeneous in IPF. Altogether, our results demonstrate a dysregulation of KGF secretion by IPF fibroblasts. The weak response to IL-1beta is associated with a defect of c-Jun expression and activation and a defect of JNK activation.

Defect of hepatocyte growth factor production by fibroblasts in human pulmonary emphysema

Pulmonary emphysema results from an excessive degradation of lung parenchyma associated with a failure of alveolar repair. Secretion by pulmonary fibroblasts of hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) is crucial to an effective epithelial repair after lung injury. We hypothesized that abnormal HGF or KGF secretion by pulmonary fibroblasts could play a role in the development of emphysema. We measured in vitro production of HGF and KGF by human fibroblasts cultured from emphysematous and normal lung samples. HGF and KGF production was quantified at basal state and after stimulation. Intracellular content of HGF was lower in emphysema (1.52 pg/mug, range of 0.15-7.40 pg/mug) than in control fibroblasts (14.16 pg/mug, range of 2.50-47.62 pg/mug; P = 0.047). HGF production by emphysema fibroblasts (19.3 pg/mug protein, range of 10.4-39.2 pg/mug) was lower than that of controls at baseline (57.5 pg/mug, range of 20.4-116 pg/mug; P = 0.019) and after stimulation with interleukin-1beta or prostaglandin E(2). Neither retinoic acids (all-trans and 9-cis) nor N-acetylcysteine could reverse this abnormality. KGF production by emphysema fibroblasts (5.3 pg/mug, range of 2.2-9.3 pg/mug) was similar to that of controls at baseline (2.6 pg/mug, range of 1-6.1 pg/mug; P = 0.14) but could not be stimulated with interleukin-1beta. A decreased secretion of HGF by pulmonary fibroblasts could contribute to the insufficient alveolar repair in pulmonary emphysema.

Secretion of keratinocyte growth factor by cultured human endometrial stromal cells is induced through a cyclic adenosine monophosphate-dependent pathway

Objective: To evaluate the effects of known modulators of endometrial function on the production of keratinocyte growth factor by endometrial stromal cells. Design: The effects of dibutyryl-cyclic adenosine monophosphate (db-cAMP), 12- O-tetradecanoylphorbol 13-acetate (TPA), ethinyl estradiol-17α (EE), and medroxyprogesterone acetate (MPA) on the secretion of keratinocyte growth factor by endometrial stromal cells were investigated. Setting: Research laboratory at a university medical school. Patient(s): Eleven endometrial specimens in the late proliferative phase. Intervention(s): Endometrial stromal cells were incubated for 24 hours with db-cAMP, TPA, EE, or MPA. Main Outcome Measure(s): The concentration of keratinocyte growth factor in the culture media was measured using an ELISA. Result(s): Small amounts of keratinocyte growth factor were detected in the culture media of unstimulated endometrial stromal cells. The production of keratinocyte growth factor by endometrial stromal cells was stimulated with db-cAMP in a dose-dependent manner. The stimulatory effect of db-cAMP was inhibited by Rp-adenosine 3′,5′-cyclic monophosphothioate. None of TPA, EE, nor MPA affected the keratinocyte growth factor production by these cells. Conclusion(s): These results suggest that a cAMP-dependent pathway may play an important role in the regulation of keratinocyte growth factor production by endometrial stromal cells. Keratinocyte growth factor secreted by endometrial stromal cells may be involved in the regeneration of the endometrium during the normal menstrual cycle and early pregnancy.

Up-Regulation of Keratinocyte Growth Factor and Receptor: A Possible Mechanism of Action of Phenytoin in Wound Healing

A number of studies suggest that keratinocyte growth factor (KGF) plays a major part in reepithelialisation after injury, via binding to the specific KGF receptor (KGFR). Several pharmacological agents, including the anti-epileptic drug phenytoin (PHT), have been widely used clinically to promote wound healing. Although the mechanism of action of PHT in this process is still not well understood, it is possible that the activity of PHT in wound healing is mediated via KGF and the KGFR. In the present study, using the enzyme-linked immunosorbant assay and flow cytometry we have shown that PHT increases KGF secretion and KGFR expression by more than 150% in gingival fibroblasts and epithelial cells, respectively. Moreover, semi-quantitative reverse transcriptase-polymerase chain reaction analysis showed that PHT also markedly increased both KGF and KGFR gene transcription by these cells. Our findings thus suggest that the wound healing activity of PHT in vivo may be mediated, at least partly, via KGF and its receptor.

KERATINOCYTE GROWTH FACTOR IS UPREGULATED BY THE HYPERPLASIA-INDUCING DRUG NIFEDIPINE

Keratinocyte growth factor (KGF) is the seventh member of the fibroblast growth factor (FGF) family. It is produced by mesenchymal cells and its activity is specific for epithelial cells, controlling epithelial homeostasis and wound repair in a paracrine manner. Although KGF has been implicated in a number of hyperplastic pathologies, it has not previously been investigated in gingival hyperplasia (GH), an adverse side-effect of three pharmacologically different types of drugs, including the anti-hypertensive drug nifedipine (NIF). The mechanism by which NIF causes GH is not yet known, but we have recently shown that KGF mRNA transcripts are elevated in drug-induced GH in vivo (manuscript submitted). It is therefore possible that the action of NIF is mediated via KGF and, in the present study, using the enzyme-linked immunosorbent assay (ELISA) and the semi-quantitative reverse transcribed-polymerase chain reaction (RT-PCR), we found that NIF upregulates KGF secretion and gene transcription by gingival fibroblasts in vitro. Our results thus suggest that KGF may have an important role in the molecular pathology of GH in vivo.

Parathyroid hormone-related protein is a positive regulator of keratinocyte growth factor expression by normal dermal fibroblasts

Parathyroid hormone-related protein (PTHrP), an important factor in the pathogenesis of humoral hypercalcemia of malignancy, is produced by many normal tissues, including the skin, where it regulates keratinocyte growth and differentiation and dermal fibroblast function. Keratinocyte growth factor (KGF), a member of the fibroblast growth factor (FGF) family, is a secretory product of stromal cells and functions as a mediator of epithelial cell growth and differentiation. Phenotypes of the skin in several transgenic mouse models, in which the KGF and PTHrP genes have been overexpressed or disrupted, suggest that these two factors interact in vivo to regulate homeostasis of the skin. In this study, we investigated the effects of KGF on PTHrP secretion and expression by normal human foreskin keratinocytes (NHFK) and the effects of PTHrP on KGF secretion and expression by normal human dermal fibroblasts (NHDF) in vitro. N-terminal PTHrP(1-36) increased KGF secretion, protein expression and mRNA expression by NHDF in a dose-dependent manner, however, KGF did not regulate PTHrP expression and secretion by NHFK. By flow cytometry, PTHrP also increased the percentage of NHDF producing KGF. Our results indicate that PTHrP produced by keratinocytes is a potential paracrine regulator of KGF expression by dermal fibroblasts in vivo. This paracrine regulation may explain, in part, the epidermal atrophy seen in the PTHrP null mice and epidermal hyperplasia seen in transgenic mice overexpressing PTHrP in their basal keratinocytes. Our results also suggest that PTHrP is an important mediator for the healing of skin wounds and growth of neoplasms of squamous origin.

Growth factors as mediators of androgen action during male urogenital development

Studies on the developing prostate and seminal vesicle suggests that androgens act via mesenchymal androgen receptors to elicit synthesis and secretion of keratinocyte growth factor and probably other paracrine factors that regulate epithelial growth and morphogenesis. Clearly, the overall regulation of prostatic epithelial growth and ductal branching morphogenesis is complex and multifactorial, involving the interaction of both positive and negative regulators, extracellular matrix, cell surface receptors for growth factors, and vascularization. Future progress in our understanding of normal and abnormal prostatic growth will certainly be dependent upon the utilization of appropriate, biologically relevant models to examine the respective roles of these complex developmental process.