JDR JDR Most Read Articles
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Smith, P.C.
Right arrow Articles by Martínez, J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Smith, P.C.
Right arrow Articles by Martínez, J.
J Dent Res 85(2):150-155, 2006
© 2006 International and American Associations for Dental Research

RESEARCH REPORT
Biological

Differential uPA Expression by TGF-ß1 in Gingival Fibroblasts

P.C. Smith1,*, and J. Martínez2

1 Faculty of Odontology and
2 Laboratory of Cell Biology, Institute of Nutrition and Food Technology (INTA), University of Chile, Olivos 943, Casilla 1903, Santiago, Chile

* corresponding author, patricio.smith{at}gmail.com


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS & METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Transforming Growth Factor-ß1 (TGF-ß1) plays a key role in connective tissue remodeling and inflammation. Under pathological conditions, like periodontal disease, fibroblasts may display an altered response to this growth factor. To investigate this question, we have studied whether TGF-ß1 may differentially regulate the expression of urokinase at the protein level in primary cultures of fibroblasts derived from healthy gingiva, granulation tissue from gingival wounds, and chronic periodontal disease. We observed that TGF-ß1 may repress urokinase expression in healthy gingival fibroblasts and promote its production in granulation-tissue fibroblasts. A significant correlation was found between expression of the myofibroblast marker {alpha}-smooth-muscle actin and stimulation of urokinase production by TGF-ß1. Immunostaining of gingival wounds showed that myofibroblasts were involved in urokinase production. TGF-ß1-stimulated urokinase expression was blocked after inhibition of the c-jun-NH2 terminal kinase signaling pathway. We propose that stimulation of urokinase production by TGF-ß1 is involved in the responses of activated fibroblasts to tissue injury.

KEY WORDS: gingival • myofibroblast • fibroblast • TGF-ß1 • urokinase


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS & METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Fibroblasts play a central role in the remodeling of extracellular matrix (ECM) (Bartold et al., 2000). During chronic inflammation and wound healing, gingival fibroblasts become "activated" and acquire several properties giving rise to a heterogeneous cell population known as granulation-tissue fibroblasts (Häkkinen and Larjava, 1992). Granulation-tissue fibroblasts are characterized by the expression of {alpha}-smooth-muscle actin ({alpha}-SMA) and differ from normal fibroblasts in proliferation rate, morphology, response to cytokines, and synthesis of ECM proteins (Desmoulière et al., 2003).

The urokinase-type plasminogen activator (uPA) is a serine-protease highly expressed in inflamed and normally healing gingival tissues (Kinnby et al., 1999; Xiao et al., 2001). uPA converts plasminogen into plasmin, another serine-protease that degrades fibrin and activates matrix metalloproteinases (Andreasen et al., 1997). Transforming Growth Factor ß1 (TGF-ß1) plays a prominent role in gingival wound-healing and inflammation (Steinsvoll et al., 1999; Kuru et al., 2004). Interestingly, many of the cell responses to this growth factor are modulated by the stage of differentiation of the cell (Akhurst and Derynck, 2001). In the case of human gingival granulation-tissue fibroblasts, TGF-ß1 stimulates the over-expression of proteoglycans (Häkkinen et al., 1996). Although regulation of uPA production is a critical step in inflammation and wound-healing, the molecular clues controlling this event are poorly understood. In the present study, we investigated whether TGF-ß1 may regulate uPA production at the protein level in gingival fibroblasts derived from distinct physiological conditions.


   MATERIALS & METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Cell Cultures
Human gingival fibroblast primary cultures were established by the explant method (Häkkinen and Larjava, 1992). Cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM) (Gibco, Carlsbad, CA, USA) containing 10% fetal bovine serum (FBS) (Gibco) supplemented with antibiotics. Cells were used between the fourth and tenth passages.

Gingival Tissue Samples and Patient Selection
All gingival samples were obtained, with informed consent, from 33 patients attending a dental practice in Santiago, Chile. The protocol was approved by the Ethical Committee of the Faculty of Medicine of the University of Chile. No relevant medical or drug histories were cited.

Granulation-tissue fibroblasts from periodontal disease (GT-PD) were obtained from marginal gingiva from patients affected by moderate to advanced periodontal disease during the extraction of hopeless teeth (n = 14) (nine women, five men; mean age, 40 ± 8 yrs). Sites selected for biopsy showed 4 mm or more of probing depth, 3 mm or more of attachment loss, and bleeding upon probing. These cells were compared with gingival fibroblasts from healthy marginal gingiva (HMG) obtained during crown-lengthening surgery (n = 6) (three women, three men; mean age, 34 ± 13 yrs). Sites selected for biopsy demonstrated a probing depth of 3 mm or less, absence of attachment loss, and no bleeding upon probing. Granulation-tissue fibroblasts from wounds (GT-W) were obtained from wounds created in the attached gingiva of human volunteers as described previously (n = 4) (three men, one woman; mean age, 33 ± 5 yrs) (Larjava et al., 1993). After 10 days of healing, granulation tissue was harvested and processed for cell culture. GT-W fibroblasts were compared with fibroblasts derived from healthy attached gingiva (HAG) obtained during the extraction of asymptomatic retained teeth (n = 9) (seven women, two men; mean age, 27 ± 12 yrs).

Detection of uPA and Plasminogen Activator Inhibitor (PAI-1)
Conditioned media (CM) derived from cell cultures stimulated with TGF-ß1 (US Biological, Swampscott, MA, USA) or Epidermal Growth Factor (EGF) (Calbiochem, La Jolla, CA, USA) was processed for uPA and PAI-1 detection through Western blot analysis as previously described (Smith et al., 2004).

Signal Transduction Studies
Mitogen-activated protein kinase (MAPK) activation was assessed through Western blot analysis with antibodies against p-JNK (Upstate Biotechnology, Lake Placid, NY, USA) or JNK2 (Santa Cruz, CA, USA) as previously described (Smith et al., 2004). Inhibition of MAPK pathways was assessed with the following reagents: SP600125 (Biomol, Plymouth, PA, USA), PD98059 and SB203580 (Calbiochem).

Casein Zymography and Radial Diffusion Assays
uPA-secreted activity and radial diffusion assay of cell cultures were determined as previously described (Santibáñez et al., 1995). Quantification of caseinolytic bands was performed by densitometric analysis. Variations in uPA activity after TGF-ß1 or EGF treatment were calculated after normalization against the non-stimulated uPA activity.

Immunofluorescence of Cultured Cells
Cells were processed for immunofluorescence as described previously (Smith et al., 2004) with antibodies against {alpha}-SMA (Sigma, St. Louis, MO, USA), vimentin (Sigma), and human cytokeratin (Dako, Carpinteria, CA, USA). Actin fibers were stained with Alexa Fluor-Phalloidin (Molecular Probes, Eugene, OR, USA). We quantified {alpha}-SMA-expressing cells by scoring {alpha}-SMA-positive/-negative cells within a total of 200 cells for each individual sample under study. For this purpose, we considered {alpha}-SMA cells as positive when immunostaining was clearly detected in association with the actin cytoskeleton.

Immunohistochemistry
Urokinase and {alpha}-SMA immunohistochemistry was performed on formalinfixed, paraffin-embedded gingival tissue biopsies by the peroxidase-antiperoxidase technique (Dako), with diaminobenzidine as chromogenic substrate. Mouse monoclonal antibodies against human uPA (American Diagnostica, Stamford, CT, USA) and {alpha}-SMA (Sigma) were used. Harris hematoxylin was used as counter-stain. We performed negative controls by replacing primary antibodies with non-immune serum. As positive controls, uPA and {alpha}-SMA expression were detected in migrating epithelial cells from gingival wounds and in blood vessels, respectively (data not shown).

Statistical Analysis
Differences in the expression of {alpha}-SMA and TGF-ß1-stimulated uPA production were evaluated by the Student’s t test. The relationship between TGF-ß1-stimulated uPA activity and {alpha}-SMA expression was analyzed by Pearson correlation. Significance was determined by Bonferroni corrections.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Characterization of Gingival Fibroblasts
Actin stress fibers were detected in both healthy and granulation-tissue fibroblasts (Fig. 1AGo). Granulation-tissue cells displayed a more extended cytoplasm when compared with healthy fibroblasts. {alpha}-SMA expression was low in HMG and HAG cultures, while it was more frequently detected in granulation-tissue cultures. Noteworthy, GT-W fibroblasts were frequently positive for this marker. The mesenchymal origin of the cells was confirmed after staining for vimentin. Quantification of myofibroblasts in each culture showed that {alpha}-SMA expression was significantly higher in GT-W fibroblasts as compared with HAG fibroblasts (p < 0.05) (Fig. 1BGo). A slightly higher, but non-significantly different, expression level of {alpha}-SMA was detected in GT-PD fibroblasts as compared with HMG fibroblasts.


Figure 1
View larger version (56K):
[in this window]
[in a new window]
  		Figure 1. Characterization of healthy and granulation-tissue fibroblasts. (A) At passage 4, human gingival fibroblasts obtained from healthy and granulation-tissue gingiva were stained with Alexa Fluorphalloidin or antibodies recognizing {alpha}-SMA or vimentin. Arrowheads indicate {alpha}-SMA-negative cells. Arrows indicate {alpha}-SMA-positive cells. Bar = 20 µm. (B) The average of {alpha}-SMA expression was obtained after we counted positively stained cells in cell cultures derived from HAG, GT-W, HMG, and GT-PD patients, and analyzed them by Student’s t test.

 
Regulation of uPA Expression by TGF-ß1 in Healthy and Granulation-tissue Fibroblasts
Sub-confluent cultures from healthy and granulation tissues were stimulated with increasing concentrations of TGF-ß1 for 48 hrs. Casein zymography of conditioned medium showed that TGF-ß1 inhibited the secreted uPA activity in healthy gingival fibroblasts (Fig. 2AGo). In contrast, granulation-tissue fibroblasts responded with a dose-dependent increase in secreted uPA activity after TGF-ß1 treatment (Fig. 2AGo). Analysis of the cell-associated uPA activity in cell lysates did not show any significant changes after TGF-ß1 stimulation (data not shown). Interestingly, treatment of cells with a distinct growth factor such as EGF consistently stimulated uPA expression in both healthy and granulation-tissue fibroblasts. Regulation of uPA expression after TGF-ß1 or EGF stimulation was confirmed through Western blotting of the concentrated conditioned medium of healthy and granulation-tissue fibroblasts (Fig. 2BGo). We further evaluated, by means of a radial diffusion assay, the overall proteolytic activity derived from plasminogen activation in the conditioned medium of TGF-ß1-stimulated cells. Surprisingly, TGF-ß1 did not stimulate uPA-derived proteolytic activity in the conditioned medium from granulation-tissue cells (Fig. 2CGo). This result was explained by the observation that TGF-ß1, but not EGF, was able to stimulate the production of the uPA inhibitor PAI-1 in granulation-tissue cells (Fig. 2DGo).


Figure 2
View larger version (33K):
[in this window]
[in a new window]
  		Figure 2. Regulation of uPA production by TGF-ß1 and EGF in healthy and granulation-tissue fibroblasts. (A) Serum-free cultures of gingival fibroblasts from healthy and granulation-tissue (80,000 cells) were stimulated with increasing concentrations of TGF-ß1 or EGF for 48 hrs in DMEM without serum. Conditioned medium, normalized after the quantification of total protein amounts in the cell lysate at the end of the experiment, was analyzed through casein zymography. (B) uPA protein levels were determined through Western blot analysis of the concentrated conditioned medium of 500,000 cells stimulated with 10 ng/mL TGF-ß1 or 10 ng/mL EGF. (C) uPA-derived proteolytic activity was determined in conditioned medium of cells stimulated with 10 ng/mL TGF-ß1 or 10 ng/mL EGF through a radial diffusion assay. (D) PAI-1 production was identified through Western blotting of concentrated conditioned medium of cells stimulated with 10 ng/mL TGF-ß1 or 10 ng/mL EGF. (E) TGF-ß1-stimulated uPA production, determined through casein zymography, in each individual was normalized against non-stimulated uPA production (indicated as 1 in the graph) and compared among the 4 groups under study. Bars indicate averages ± standard deviations. Statistical analysis was performed with Student’s t test (n=33). (F) We performed Pearson correlation analysis, comparing TGF-ß1-stimulated uPA production through casein zymography and {alpha}-SMA expression.

 
After examining several cultures from healthy and granulation tissues, we observed that GT-W (n = 4) and GT-PD (n = 14) fibroblasts responded with a significant increase in uPA production, as compared with their respective controls (p < 0.05) (Fig. 2EGo). All of the cultures derived from HAG and HMG showed an inhibition or a non-responsive behavior after TGF-ß1 stimulation (n = 15). Although cells derived from both GT-W and GT-PD cultures responded to TGF-ß1 with an increase in uPA production, a higher response was observed in wound-derived cells. We performed a correlation analysis comparing TGF-ß1-stimulated uPA production and {alpha}-SMA expression in all cell cultures, regardless of their clinical origin. Pearson correlation analysis showed a measurable relationship between {alpha}-SMA expression and TGF-ß1-stimulated uPA production (r = 0.562; p < 0.01; n = 33) (Fig. 2FGo).

Signaling Pathways Involved in uPA Production
In healthy gingival fibroblasts, TGF-ß1 inhibited uPA production, and the MAPK inhibitors tested did not modify this response (Fig. 3AGo). In granulation-tissue fibroblasts, the JNK inhibitor SP600125 completely abrogated the stimulus of TGF-ß1 on uPA production, while blockade of the ERK (PD98059) and p38 (SB203580) pathways did not interfere in this response. These results were replicated in 3 independent experiments with different cell cultures. Inhibition of uPA production by SP600125 displayed dose-dependent behavior (Fig. 3BGo). In addition, we observed that JNK was activated by TGF-ß1 in granulation-tissue fibroblasts (Fig. 3CGo).


Figure 3
View larger version (28K):
[in this window]
[in a new window]
  		Figure 3. Signal transduction pathways involved in TGF-ß1-stimulated uPA production. (A) Healthy and granulation-tissue gingival fibroblasts (80,000 cells) were cultured in the presence of specific MAPK inhibitors: 40 µM PD98059, 10 µM SB203580, or 10 µM SP600125 in serum-free DMEM. After 15 min, cell cultures were treated with 10 ng/mL TGF-ß1 for 48 hrs. Secreted uPA activity was evaluated by casein zymography. (B) Dose-response analysis of the effects of the JNK inhibitor SP600125 on TGF-ß1-stimulated uPA production determined through casein zymography in 3 independent experiments. (C) Gingival granulation-tissue fibroblasts (300,000 cells) were incubated with TGF-ß1 (10 ng/mL) in DMEM without serum for different periods of time, as indicated. The level of activated JNK (pJNK) was determined by Western blotting with specific antibodies.

 
Expression of Urokinase in Gingival Wounds
Urokinase and {alpha}-SMA expression was assessed, through immunohistochemistry, in 3 normally healing gingival wounds. Expression of {alpha}-SMA was prominent in granulation-tissue fibroblasts (Figs. 4A, 4CGo). uPA expression was observed in keratinocytes, endothelial cells, and fibroblasts (Fig. 4BGo). After staining serial sections, we observed a spatial correlation between the distribution of {alpha}-SMA-positive fibroblasts and the expression of uPA in similar cell types (Figs. 4C, 4DGo). In healthy gingival tissues, {alpha}-SMA expression was occasionally detected in blood vessels and fibroblasts, while uPA expression was observed at low levels in endothelial cells or fibroblasts (Figs. 4E, 4FGo). Negative controls did not show any specific immunoreactivity (not shown).


Figure 4
View larger version (95K):
[in this window]
[in a new window]
  		Figure 4. Immunolocalization of {alpha}-SMA expression and uPA production in sections of gingival wounds and healthy gingiva. (A,C,E) {alpha}-SMA expression. (B,D,F) uPA production. (A–D) Acute gingival wounds. (E,F) Healthy gingiva. GT = granulation tissue. HT = healthy tissue. BV = blood vessel. (G) Negative control section. Arrows indicate {alpha}-SMA staining; arrowheads indicate uPA staining. Bar = 50 µm.

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
Regulation of uPA production is a critical event that may affect the evolution of cancer, wound healing, and inflammation (Carmeliet et al., 1994; Harbeck et al., 2004). TGF-ß1 stimulates uPA production during epithelial-mesenchymal transformation (Santibáñez et al., 2000). However, in mesenchymal cells, contradictory studies have reported that TGF-ß1 may have a stimulatory, inhibitory, or null effect on uPA production in fibroblasts derived from lung, synovium, breast, or skin (Laiho et al., 1986a,b; Hamilton et al., 1991; Sieuwerts et al., 1999). In the present study, we observed that healthy gingival fibroblasts either responded to TGF-ß1 with an inhibition of uPA production or, eventually, did not respond. In granulation-tissue fibroblasts, TGF-ß1 stimulated uPA and PAI-1 production, adding a crucial element to the cellular proteolytic balance. In spite of the fact that the radial diffusion assay showed that TGF-ß1 seems to be unable to stimulate plasminogen activation due to PAI-1 synthesis, we cannot rule out that temporal or spatial variations in the synthesis or distribution of uPA and PAI-1 by TGF-ß1-stimulated cells might result in plasminogen processing in vivo.

uPA is secreted as an inactive molecule and is converted to an active form that generates plasminogen activation. Plasmin is the main factor involved in uPA activation, thus leading to a reciprocal pro-enzyme activation phenomenon (Behrendt, 2004). From our data, we can suggest that EGF, which generates strong plasminogen activation in both cell types, may stimulate uPA synthesis and activation. It remains to be determined whether TGF-ß1 is able to induce uPA activation in gingival fibroblasts.

Plasminogen activation may also be achieved by tissue plasminogen activator (tPA) (Irigoyen et al., 1999). Although previous studies have demonstrated that gingival fibroblasts may express tPA, our casein-zymography assays were not able to detect a 64-kDa band corresponding to this molecular species.

Besides its role as a protease, uPA may also stimulate proliferation of fibroblasts and chemotaxis of neutrophils, macrophages, and fibroblasts (Anichini et al., 1994; Resnati et al., 1996). Therefore, TGF-ß1-stimulated uPA production by granulation-tissue fibroblasts might promote the recruitment of different cells to the site of tissue injury.

Resident tissue fibroblasts may become activated after tissue injury, and acquisition of this phenotype may further modulate the responses of these cells to growth factors (Desmoulière et al., 2003). In this context, gingival granulation-tissue fibroblasts may develop an altered expression of several proteoglycans and collagens after TGF-ß1 stimulation (Häkkinen et al., 1996). Our results, showing that granulation-tissue fibroblasts up-regulate uPA expression after TGF-ß1 treatment, are in accordance with the proposed distinct cell behavior among fibroblasts derived from different physiological conditions.

Gingival myofibroblasts play a significant role in the remodeling of the ECM (Arora and McCulloch, 1994). We observed that expression of the myofibroblast marker {alpha}-SMA varied greatly in the cell cultures under study, with lower levels in resting healthy tissues, intermediate levels in GT-PD, and higher levels in GT-W fibroblasts. Although both wound- and periodontitis-derived cells responded to TGF-ß1 with an increase in uPA production, a more expressive response was observed in wound-derived cells that displayed the higher levels of {alpha}-SMA. These findings suggest that chronic periodontal lesions represent a mixture of cell phenotypes in which myofibroblast differentiation is not totally accomplished.

Urokinase expression is tightly regulated at the transcriptional level, and several MAPK pathways have been involved in uPA expression (Miralles et al., 1998; Parra et al., 2000; Santibáñez et al., 2000). Fibroblasts deficient in MEKK1, an upstream stimulator of ERK and JNK, are unable to up-regulate uPA expression after stimulation with growth factors (Witowsky et al., 2003). We have recently reported that, in healthy gingival fibroblasts, EGF-stimulated uPA expression depends on the combined activity of ERK and JNK pathways (Smith et al., 2004). Here, we observed that, in granulation-tissue cells, TGF-ß1-stimulated uPA expression was abolished after inhibition of the JNK pathway, suggesting that this route may be involved in the expression of uPA.

Immunostaining of normally healing gingival wounds showed that gingival granulation-tissue fibroblasts were involved in uPA expression. These results reinforce in vitro results showing that, in cell cultures enriched in myofibroblasts, TGF-ß1 stimulated uPA expression. Granulation-tissue fibroblasts have been identified as a prominent source of uPA during wound healing (Schäfer et al., 1994). Interestingly, in response to cancer invasion, peritumoral stromal cells develop a tissular reaction known as ’cancer desmoplasia’, and these cells are also involved in uPA production (Nielsen et al., 1996).

Periodontal disease is characterized by alternating periods of tissue degradation and fibrosis. During wound healing, tissue remodeling allows for the replacement of the injured tissue. In both processes, it has been hypothesized that myofibroblasts play an active role. In the present study, we were able to determine that granulation-tissue fibroblasts respond to TGF-ß1 by increasing uPA production, a process which is possibly regulated by the JNK signaling pathway. We propose that these events are involved in the responses of activated gingival fibroblasts to tissue injury.


   ACKNOWLEDGMENTS
 
This work received financial support from the Departamento de Investigación y Desarrollo, Universidad de Chile, grant number 02/10-2 (to JM), FONDECYT, grant number (1040734) (to JM), and from Colgate Palmolive Chile S.A. We thank Prof. Julieta González and Prof. Cecilia Allende (ICBM, Faculty of Medicine, University of Chile), Prof. Alejandro Oyarzún (Faculty of Odontology, University of Chile), and Dr. Juan F. Santibáñez (INTA, University of Chile) for helping us with immunohistochemistry, microphotography, and cell culture assays, respectively. We also acknowledge Dr. Marco Méndez (INTA, University of Chile), who performed the statistical analysis, and Dr. Mariana Cifuentes (INTA, University of Chile), for critical reading of this manuscript.

Received March 4, 2005; Last revision August 29, 2005; Accepted September 15, 2005


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Akhurst RJ, Derynck R (2001). TGF-beta signaling in cancer—a double-edged sword. Trends Cell Biol 11:S44–S51.[ISI][Medline]

Andreasen PA, Kjøller L, Christensen L, Duffy MJ (1997). The urokinase-type plasminogen activator system in cancer metastasis: a review. Int J Cancer 72:1–22.[ISI][Medline]

Anichini E, Fibbi G, Pucci M, Caldini R, Chevanne M, Del Rosso M (1994). Production of second messengers following chemotactic and mitogenic urokinase-receptor interaction in human fibroblasts and mouse fibroblasts transfected with human urokinase receptor. Exp Cell Res 213:438–448.[ISI][Medline]

Arora PD, McCulloch CA (1994). Dependence of collagen remodelling on alpha-smooth muscle actin expression by fibroblasts. J Cell Physiol 159:161–175.[ISI][Medline]

Bartold PM, Walsh LJ, Narayanan AS (2000). Molecular and cell biology of the gingiva. Periodontol 2000 24:28–55.

Behrendt N (2004). The urokinase receptor (uPAR) and uPAR-associated protein (uPARAP/Endo180): membrane proteins engaged in matrix turnover during tissue remodeling. Biol Chem 385:103–136.[ISI][Medline]

Carmeliet P, Schoonjans L, Kieckens L, Ream B, Degen J, Bronson R, et al. (1994). Physiological consequences of loss of plasminogen activator gene function in mice. Nature 368:419–424.[Medline]

Desmoulière A, Darby IA, Gabbiani G (2003). Normal and pathologic soft tissue remodeling: role of the myofibroblast, with special emphasis on liver and kidney fibrosis. Lab Invest 83:1689–1707.[ISI][Medline]

Häkkinen L, Larjava H (1992). Characterization of fibroblast clones from periodontal granulation tissue in vitro. J Dent Res 71:1901–1907.[Abstract/Free Full Text]

Häkkinen L, Westermarck J, Kähäri V-M, Larjava H (1996). Human granulation-tissue fibroblasts show enhanced proteoglycan gene expression and altered response to TGF-ß1. J Dent Res 75:1767–1778.[Abstract/Free Full Text]

Hamilton JA, Piccoli DS, Leizer T, Butler DM, Croatto M, Royston AK (1991). Transforming growth factor beta stimulates urokinase-type plasminogen activator and DNA synthesis, but not prostaglandin E2 production, in human synovial fibroblasts. Proc Natl Acad Sci USA 88:7180–7184.[Abstract/Free Full Text]

Harbeck N, Kates RE, Gauger K, Willems A, Kiechle M, Magdolen V, et al. (2004). Urokinase-type plasminogen activator (uPA) and its inhibitor PAI-I: novel tumor-derived factors with a high prognostic and predictive impact in breast cancer. Thromb Haemost 91:450–456.[ISI][Medline]

Irigoyen JP, Muñoz-Canoves P, Montero L, Koziczak M, Nagamine Y (1999). The plasminogen activator system: biology and regulation. Cell Mol Life Sci 56:104–132.[ISI][Medline]

Kinnby B, Lindberg P, Lecander I, Matsson L (1999). Localization of plasminogen activators and plasminogen-activator inhibitors in human gingival tissues demonstrated by immunohistochemistry and in situ hybridization. Arch Oral Biol 44:1027–1034.[ISI][Medline]

Kuru L, Griffiths GS, Petrie A, Olsen I (2004). Changes in transforming growth factor-beta1 in gingival crevicular fluid following periodontal surgery. J Clin Periodontol 31:527–533.[ISI][Medline]

Laiho M, Saksela O, Keski-Oja J (1986a). Transforming growth factor beta alters plasminogen activator activity in human skin fibroblasts. Exp Cell Res 164:399–407.[ISI][Medline]

Laiho M, Saksela O, Andreasen PA, Keski-Oja J (1986b). Enhanced production and extracellular deposition of the endothelial-type plasminogen activator inhibitor in cultured human lung fibroblasts by transforming growth factor-beta. J Cell Biol 103:2403–2410.[Abstract/Free Full Text]

Larjava H, Salo T, Haapasalmi K, Kramer RH, Heino J (1993). Expression of integrins and basement membrane components by wound keratinocytes. J Clin Invest 92:1425–1435.[ISI][Medline]

Miralles F, Parra M, Caelles C, Nagamine Y, Felez J, Muñoz-Canoves P (1998). UV irradiation induces the murine urokinase-type plasminogen activator gene via the c-Jun N-terminal kinase signaling pathway: requirement of an AP1 enhancer element. Mol Cell Biol 18:4537–4547.[Abstract/Free Full Text]

Nielsen BS, Sehested M, Timshel S, Pyke C, Danø K (1996). Messenger RNA for urokinase plasminogen activator is expressed in myofibroblasts adjacent to cancer cells in human breast cancer. Lab Invest 74:168–177.[ISI]

Parra M, Lluis F, Miralles F, Caelles C, Muñoz-Cánoves P (2000). The cJun N-terminal kinase (JNK) signaling pathway mediates induction of urokinase-type plasminogen activator (uPA) by the alkylating agent MNNG. Blood 96:1415–1424.[Abstract/Free Full Text]

Resnati M, Guttinger M, Valmonica S, Sidenius N, Blasi F, Fazioli F (1996). Proteolytic cleavage of the urokinase receptor substitutes for the agonist-induced chemotactic effect. EMBO J 15:1572–1582.[ISI][Medline]

Santibáñez JF, Maccioni RB, Martínez J (1995). The secretion of urokinase-like plasminogen activator is inhibited by microtubule-interacting drugs. Cell Biochem Funct 13:217–225.[ISI][Medline]

Santibáñez JF, Iglesias M, Frontelo P, Martínez J, Quintanilla M (2000). Involvement of the Ras/MAPK signaling pathway in the modulation of urokinase production and cellular invasiveness by transforming growth factor-beta(1) in transformed keratinocytes. Biochem Biophys Res Commun 273:521–527.[ISI][Medline]

Schäfer BM, Maier K, Eickhoff U, Todd RF, Kramer MD (1994). Plasminogen activation in healing human wounds. Am J Pathol 144:1269–1280.[Abstract]

Sieuwerts AM, Klijn JG, Henzen-Logmans SC, Foekens JA (1999). Cytokine-regulated urokinase-type-plasminogen-activator (uPA) production by human breast fibroblasts in vitro. Breast Cancer Res Treat 55:9–20.[ISI][Medline]

Smith PC, Santibáñez JF, Morales JP, Martinez J (2004). Epidermal growth factor stimulates urokinase-type plasminogen activator expression in human gingival fibroblasts. Possible modulation by genistein and curcumin. J Periodontal Res 39:380–387.[ISI][Medline]

Steinsvoll SH, Alstensen TS, Schenck K (1999). Extensive expression of TGF-beta1 in chronically-inflamed periodontal tissue. J Clin Periodontol 26:366–373.[ISI][Medline]

Witowsky J, Abell A, Johnson NL, Johnson GL, Cuevas BD (2003). MEKK1 is required for inducible urokinase-type plasminogen activator expression. J Biol Chem 278:5941–5946.[Abstract/Free Full Text]

Xiao Y, Li H, Bunn C, Bartold PM (2001). The expression of plasminogen activator system in a rat model of periodontal wound healing. J Periodontol 72:849–857.[ISI][Medline]





This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Smith, P.C.
Right arrow Articles by Martínez, J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Smith, P.C.
Right arrow Articles by Martínez, J.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
IADR Journals Advances in Dental Research ®
Journal of Dental Research ® Critical Reviews (1990-2004)