Fibroblast heterogeneity in the periodontium and other tissues

Effects of compressive force on the differentiation of pluripotent mesenchymal cells

The purpose of this study was to determine the effect of mechanical stress on the differentiation of the pluripotent mesenchymal cell line C2C12. C2C12 cells were cultured continuously under compressive force (0.25-2.0 g/cm(2)). After mechanical stress loading, the levels of expression of mRNAs and proteins for phenotype-specific markers of osteoblasts (Runx2, Msx2, Dlx5, Osterix, AJ18), chondroblasts (Sox5, Sox9), myoblasts (MyoD), and adipocytes (PPAR gamma) were measured by real-time polymerase chain reaction analysis and Western blot analysis, respectively. The expression of activated p38 mitogen-activated protein kinase (p38 MAPK) was measured by Western blotting and/or ELISA. Loading 0.5 g/cm(2) of compressive force significantly increased the expression levels of Runx2, Msx2, Dlx5, Osterix, Sox5, and Sox9. In contrast, the expression levels of AJ18, MyoD, and PPAR gamma were decreased by exposure to 0.5 g/cm(2) of compressive force. Loading 0.5 g/cm(2) of compressive force also induced the phosphorylation of p38 MAPK. SB203580, which is a specific inhibitor of p38 MAPK, inhibited the compressive force-induced phosphorylation of p38 MAPK and partially blocked compressive force-induced Runx2 mRNA expression. These results demonstrate that compressive force stimulation directs the differentiation pathway of C2C12 cells into the osteoblast and chondroblast lineage via activated phosphorylation of p38 MAPK.

Distinctive molecular composition of human gingival interdental papilla

BACKGROUND

Gingiva is composed of attached and marginal (free) gingiva and interdental papilla. Increasing esthetic demands in dentistry have created a need to restore all parts of the gingiva. However, the interdental papilla has limited regeneration potential compared to other parts of the gingiva. It also is more susceptible to gingival overgrowth, suggesting that it has distinct cellular and molecular properties from other parts of the gingiva. Very little is known about the possible differences in the molecular composition of different parts of the gingiva.

METHODS

We compared the expression of a set of key molecules in interdental papilla and marginal gingiva from seven healthy subjects by immunohistochemical staining.

RESULTS

In the interdental papilla, immunoreactivity for integrin alphavbeta6 and cytokeratin 19 in the oral epithelium was significantly higher than in marginal gingiva. Expression of type I procollagen, extra domain A (EDA) and extra domain B (EDB) fibronectin isoforms, tenascin-C, transforming growth factor-beta (TGF-beta), connective tissue growth factor (CTGF), and the signaling molecule son-of-sevenless (SOS)-1 also were increased in the interdental papilla. The expression of small leucine-rich proteoglycans decorin, biglycan, fibromodulin, and lumican in the interdental papilla was partially different from the marginal gingiva.

CONCLUSIONS

Molecular composition of the interdental papilla is distinct from marginal gingiva. Increased expression of molecules normally induced in wound healing (alphavbeta6 integrin, fibronectin-EDB and -EDA, tenascin-C, type I procollagen, TGF-beta, CTGF, and SOS-1) suggests that the cells in the interdental papilla are in an activated state and/or inherently display a specific phenotype resembling wound healing.

Enhanced synthesis of proinflammatory cytokines by vulvar vestibular fibroblasts: implications for vulvar vestibulitis

OBJECTIVE

The objective of the study was to determine whether vestibular fibroblasts from vulvar vestibulitis (VVS) patients produce higher proinflammatory cytokine levels when provoked with Candida albicans (yeast) and alpha-melanocyte-stimulating hormone (alpha-MSH) in vitro.

STUDY DESIGN

Twenty anatomically defined fibroblast strains from patients and age-matched controls were stimulated with 5 regimens: no stimulus, alpha-MSH, heat-killed yeast, alpha-MSH plus yeast, and interleukin (IL)-1beta. Supernatant products included the following: granulocyte macrophage colony-stimulating factor, interferon-gamma, IL-10, IL-12, IL-1beta, IL-2, IL-4, IL-6, IL-8, and tumor necrosis factor-alpha were assayed.

RESULTS

Coincubation with alpha-MSH plus yeast significantly increased IL-6 (3-fold) and IL-8 (greater than 40-fold) production in patients and controls. Vestibular fibroblast exceeded external vulvar fibroblast production of IL-1beta, IL-6, and IL-8 following yeast alone and alpha-MSH plus yeast stimuli in patients and controls. Substratified by anatomic origin, vestibular fibroblasts from VVS patients produced the highest relative levels of IL-1beta, IL-6, and IL-8 at baseline and following the yeast-alone regimen.

CONCLUSION

Localized pain of VVS may results from regionally elevated cytokines produced by vulvar vestibule-specific fibroblasts.

Differential chemokine response of fibroblast subtypes to complement C1q

BACKGROUND AND OBJECTIVE

The pathogenesis of periodontitis includes an inappropriate activation of the classical complement cascade (C') with accumulation of inflammatory C' products in fluids and tissues. Our hypothesis is that in vivo the C' product, C1q, may act as a regulatory component of the innate immune response of distinct matrix fibroblasts to the inflammatory environment. This study analyzed the C1q induction of pro-inflammatory cytokine secretion in fibroblast subtypes derived from distinct periodontal tissues, and identified a mechanism of the cell response.

MATERIAL AND METHODS

Primary human gingival fibroblast, periodontal ligament fibroblast, and granulation tissue fibroblast cultures were treated for 24 h with C1q. Protein arrays assessed the secretory profile of constitutive and C1q-inducible pro-inflammatory cytokines, and enzyme-linked immunosorbent assays were used to quantify the kinetics of each inducible cytokine.

RESULTS

Granulation tissue fibroblast cultures were unresponsive to C1q challenge. In contrast, periodontal ligament fibroblasts responded with a release of monocyte chemoattractant protein (MCP)-1, interleukin-6, interleukin-8, and macrophage inflammatory protein (MIP)-1beta higher than the basal level by 8.2-, 7.0-, 3.8-, and 7.2-fold, respectively. Human gingival fibroblast cultures increased secretion of these chemokines by 5.2-, 4.5-, 3.0-, and 9.8-fold, respectively. Inhibitor studies revealed that C1q-inducible release of chemokines by the human gingival fibroblast and periodontal ligament cultures was contingent upon p38 mitogen-activated protein kinase activity.

CONCLUSION

The ability of C1q to stimulate secretion of pro-inflammatory chemokines depends upon which specific fibroblast subtype is involved. Targeting C1q-activated intracellular signaling pathways may be an effective means to inhibit the production of chemokines that promote inflammatory cell infiltration into gingival and periodontal ligament tissues.

Thy-1 expression by cardiac fibroblasts: lack of association with myofibroblast contractile markers

The objective of this study was to investigate the presence of Thy-1 in the myocardium and on cardiac fibroblasts and to determine whether or not cardiac fibroblasts form a heterogeneous population in term of Thy-1 expression. Thy-1 expression was examined by immunohistology of ventricular sections from normal and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Thy-1 immunostaining was detected in connective tissue on alpha8 integrin-positive and discoidin domain receptor 2 (DDR2)-positive fibroblasts. Enhanced Thy-1 staining was observed in the hearts of DOCA-salt rats particularly in areas of interstitial fibrosis. Cardiac mRNA analysis confirmed the increased Thy-1 expression. On cultured cardiac fibroblasts, flow cytofluorometry showed that cells, from primary culture to passage 4, were double positive for Thy-1 and for both alpha8 integrin and DDR2. Analysis of isolated lipid rafts by detergent-free sucrose gradient indicated that Thy-1 protein was probably located in these structures, but it may be located on a membrane microdomain slightly different from those of caveolin-1, as revealed by immunocytochemistry. Differentiation of fibroblasts into myofibroblasts being a characteristic of cardiac fibrosis and scarring, cardiac fibroblasts were stimulated in the presence of transforming growth factor-beta (TGF-beta) or connective tissue growth factor. While the expression of smooth muscle alpha-actin and alpha8 integrin doubled, Thy-1 level, measured by Western blotting and flow cytofluorometry, was not influenced by TGF-beta. These results demonstrate that cardiac fibroblasts express Thy-1 and form a homogeneous population. Thy-1 expression also appears to be independent of fibroblast differentiation. The dichotomy between the increased Tthy-1 expression in the fibrotic area and the lack of association with fibroblast differentiation suggests that Thy-1 may represent a marker of fibroblast proliferation in the myocardium.

Muscarinic cholinoceptor activation modulates DNA synthesis and CD40 expression in fibroblast cells

1 The aim of the present work was to examine the role of muscarinic acetylcholine receptors (mAChR) on DNA synthesis and CD40 expression in human fibroblast cells. Neonatal human skin fibroblast cultures were stimulated with carbachol in presence or absence of specific antagonists and the following parameters were measured: identification of mAChR subtypes, DNA synthesis, inositol phosphates (InsP) production and CD40 expression. 2 Human fibroblasts express mAChR with Kd 0.47 +/- 0.11 nm and Bmax 236 +/- 22 fmol mg protein(-1). Carbachol stimulates DNA synthesis, InsP and the expression of CD40. All these effects were inhibited by atropine, mustard hydrochloride (4-DAMP) and pirenzepine but not by AF-DX 116 and tropicamide, indicating that M3 and M1 mAChR are implicated in carbachol action. The relative Ki of the antagonists obtained by competition binding assay was in parallel to the relative potency for blocking both carbachol-stimulated InsP accumulation and DNA synthesis. 3 The intracellular pathway leading to carbachol-induced biological effects involved phospholipase C and calcium/calmodulin, as U-73122 and trifluoroperazine blocked carbachol effects, respectively. Calphostin C, a protein kinase C inhibitor, had no effect, indicating that this enzyme does not participate in the system. 4 These results may contribute to a better understanding of the modulatory role of the parasympathetic muscarinic system on normal human fibroblast function.

Effects of an enamel matrix derivative on human osteoblasts and PDL cells grown in organoid cultures

OBJECTIVE

The objective of this study was to investigate cellular effects of enamel matrix derivative (EMD) in human derived, primary osteoblasts and periodontal ligament (PDL) cells grown in organoid cultures.

STUDY DESIGN

Cell replication was assessed by BrdU-incorporation. [(3)H]-proline incorporation was measured to determine the synthesis of proline-containing proteins, such as collagen. In addition, calcium accumulation and alkaline-phosphatase-activity were quantified. Electron microscopy for morphological analysis was performed.

RESULTS

Our results showed that EMD enhances BrdU-incorporation in PDL cells and osteoblasts. Also, in osteoblast organoid cultures [3H]-proline incorporation was 3-fold increased (P < .01). Extensive matrix deposition was noted in osteoblast cultures by electron microscopy. In osteoblasts, high levels of calcium accumulation and alkaline-phosphatase-activity were found. However, EMD did not promote mineralization.

CONCLUSION

Our results indicate that under organoid culture conditions EMD is able to promote the synthesis of proline-containing proteins such as collagen but not matrix mineralization of primary human osteoblastic cells.

Tissue-Specific Function of Lymph Node Fibroblastic Reticulum Cells

OBJECTIVE

We present the first characterization of the cytokine expression pattern of lymph node fibroblastic reticulum cells (FRC), which are the stromal cells responsible for maintaining the highly structured nodal reticular fiber framework.

METHODS

Microarray expression profiles of cultured nodal FRC and dermal fibroblasts (DF) were compared as well as their response to TNF, IL-4, IL-6 and IL-13, cytokines responsible for intranodal stromal activation.

RESULTS

Hierarchical clustering of FRC and DF short-term culture samples revealed genes that were differentially expressed in FRC and DF. Identified differently regulated genes were confirmed by RNase protection analysis, PCR or immunohistochemistry. At earlier culture time points, FRC showed higher levels of several chemokines, including CCL2/MCP-1, and cytokines, e.g. IL-6, whereas several genes related to the production of extracellular matrix and angiogenesis were preferentially expressed in early DF cultures. By 60 days in culture, FRC and DF showed similar expression patterns consistent with homogenization of specialized stromal subsets. FRC and DF showed nearly identical transcriptional responses to exogenous TNF stimulation.

CONCLUSIONS

Cultured FRC showed an overall transcriptional profile similar to cultured DF, including parallel responsiveness to TNF, but with differences in the expression of chemotactic chemokines, which reflect their biological roles.

Heterogeneous presence of myofibroblasts in hereditary gingival fibromatosis

BACKGROUND/AIM

Hereditary gingival fibromatosis (HGF) fibroblasts are characterized by an increased production of collagen and transforming growth factor-beta1 (TGF-beta1), resulting in a fibrotic enlargement of the gingiva of affected patients. A common feature of interstitial fibrosis is the occurrence of myofibroblasts, which are regarded as the predominant cells in matrix synthesis. The goal of this article is to describe the presence of myofibroblasts in HGF in order to elucidate the mechanisms underlying HGF gingival overgrowth.

MATERIALS AND METHODS

Fibroblast cell lines and gingival samples from patients of two distinct families affected by HGF and from normal gingiva (NG) were included in this study. To characterize the presence of myofibroblasts, the expression of specific myofibroblast marker smooth muscle isoform of alpha-actin (alpha-SMA) was examined by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, immunofluorescence, and flow cytometric analysis. Immunohistochemistry against the alpha-SMA antigen was performed in the gingival tissue samples.

RESULTS

Our results demonstrated a significant increase in the expression of the myofibroblast marker alpha-SMA in cells from one HGF family (designed as HGF Family 2), which are also characterized by an elevated expression of type I collagen, TGF-beta1 and connective tissue growth factor (CTGF). Additionally, alpha-SMA-positive cells were broadly detected in the gingival tissue samples from HGF Family 2 patients. In contrast, alpha-SMA expression by HGF Family 1 cells was quite similar to NG cells and no myofibroblasts were detected immunohistochemically, despite the higher levels of TGF-beta1 and type I collagen in HGF Family 1 fibroblasts than in NG cells. The expression of CTGF, which has been considered a key molecule to promote the transdifferentiation of myofibroblasts via TGF-beta1 activation, by HGF Family 1 cultures was significantly lower compared with HGF Family 2 and similar to NG control cells.

CONCLUSIONS

Our results suggest that the presence of myofibroblasts in HGF could be dependent on CTFG expression levels, and different biological mechanisms may account for the gingival overgrowth observed in HGF patients. This could be an underlying reason for the high variable clinical expressivity of disease.

Proteomic analysis of protein components in periodontal ligament fibroblasts

BACKGROUND

Characterization of periodontal ligament (PDL) fibroblast proteome is an important tool for understanding PDL physiology and regulation and for identifying disease-related protein markers. PDL fibroblast protein expression has been studied using immunological methods, although limited to previously identified proteins for which specific antibodies are available.

METHODS

We applied proteomic analysis coupled with mass spectrometry and database knowledge to human PDL fibroblasts.

RESULTS

We detected 900 spots and identified 117 protein spots originating in 74 different genes. In addition to scaffold cytoskeletal proteins, e.g., actin, tubulin, and vimentin, we identified proteins implicated with cellular motility and membrane trafficking, chaparonine, stress and folding proteins, metabolic enzymes, proteins associated with detoxification and membrane activity, biodegradative metabolism, translation and transduction, extracellular proteins, and cell cycle regulation proteins.

CONCLUSIONS

Most of these identified proteins are closely related to the extensive PDL fibroblasts' functions and homeostasis. Our PDL fibroblast proteome map can serve as a reference map for future clinical studies as well as basic research.

Lipopolysaccharide-binding protein down-regulates the expression of interleukin-6 by human gingival fibroblast

BACKGROUND

Lipopolysaccharide-binding protein (LBP) participates in the interaction of lipopolysacchaide (LPS) with CD14 to modulate the expression of cytokines. Human gingival fibroblast may actively participate in LPS-induced immuno-inflammatory responses through CD14, toll-like receptor (TLR) superfamily, MD-2 and related adaptive proteins, leading to the expression of cytokines.

OBJECTIVES

The present in vitro study aimed to investigate the possible effect of LBP and E. coli LPS interaction on the expression of cellular LPS receptors and IL-6 by human gingival fibroblast.

METHODS

The mRNA expression of CD14, LBP, TLR-2, TLR-4, MD-2 and IL-6 in human gingival fibroblast explants was detected by reverse transcriptionpolymerase chain reaction (RT-PCR) in the presence or absence of E. coli LPS and recombinant human LBP (rhLBP), while IL-6 peptides were analyzed by ELISA and immunohistochemistry, respectively.

RESULTS

Human gingival fibroblast could constitutively express CD14, MD-2 and IL-6 mRNAs, but not TLR-2, TLR-4 and LBP mRNAs. E. coli LPS induced the messages expression of MD-2, TLR-2 and -4. The expression of both IL-6 message and peptide was up-regulated by E. coli LPS in a dose dependent manner. Whereas rhLBP could significantly down-regulate the expression of both mRNAs and peptides of CD14 and IL-6 but not MD-2 signals in the presence or absence of E. coli LPS. The up-regulated expression of TLR-2 and -4 by E. coli LPS no longer existed in the presence of rhLBP.

CONCLUSIONS

This study suggests that LBP may down-regulate the expression of IL-6 by human gingival fibroblast. Further studies are warranted to clarify the molecular mechanisms of LBP in regulation of cytokine expression by host cells and to elaborate the relevant clinical implications.

Expression of CD13/aminopeptidase N on human gingival fibroblasts and up-regulation upon stimulation with interleukin-4 and interleukin-13

BACKGROUND AND OBJECTIVES

Aminopeptidase N (APN)/CD13 is a multifunctional ectoenzyme that is involved in anti-inflammatory reactions, control of immune reactions and differentiation of many cellular systems. Here, we hypothesized that CD13/APN would be expressed on human gingival fibroblasts (hGF) and would contribute to the regulation of immune responses in periodontal tissue.

METHODS AND RESULTS

CD13/APN was expressed on hGF at the mRNA and protein levels as determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and flow cytometry, respectively. Enzymatic activities accompanying the expression were assessed by colorimetrical analysis using the synthetic substrate Leu-p-nitroanilide. We examined the possible regulation of CD13/APN expression on hGF in response to T cell-derived cytokines. T helper (Th) 2 cell type cytokines such as interleukin-4 and interleukin-13, but not interleukin-2 or interleukin-15, preferentially increased the expression of proteins as well as the enzymatic activities of CD13/APN in a dose-dependent manner. Receptors for these cytokines, the interleukin-4 receptor alpha chain, interleukin-13 receptor alpha1 chain, and interleukin-2R common gamma chain, were expressed on hGF assessed by RT-PCR or flow cytometry. hGF exhibited inhibitory effects for formyl-methionyl-leucyl-phenylalanine (FMLP)-induced polymorphonuclear leukocyte-activation that was evaluated by Mac-1 expression, and this inhibitory effect was partially recovered by pre-treatment with the APN-specific inhibitor bestatin.

CONCLUSIONS

These findings suggested that CD13/APN expressed by hGF could contribute to the anti-inflammatory response in periodontal tissue, and may be involved in disease processes mediated by Th2 cells.

Site-matched papillary and reticular human dermal fibroblasts differ in their release of specific growth factors/cytokines and in their interaction with keratinocytes

The interfollicular dermis of adult human skin is partitioned into histologically and physiologically distinct papillary and reticular zones. Each of these zones contains a unique population of fibroblasts that differ in respect to their proliferation kinetics, rates at which they contract type I collagen gels, and in their relative production of decorin and versican. Here, site-matched papillary and reticular dermal fibroblasts couples were compared to determine whether each population interacted with keratinocytes in an equivalent or different manner. Papillary and reticular fibroblasts grown in monolayer culture differed significantly from each other in their release of keratinocyte growth factor (KGF) and granulocyte-macrophage colony stimulating factor (GM-CSF) into culture medium. Some matched fibroblast couples also differed in their constitutive release of interleukin-6 (IL-6). Papillary fibroblasts produced a higher ratio of GM-CSF to KGF than did corresponding reticular fibroblasts. Interactions between site-matched papillary and reticular couples were also assayed in a three-dimensional culture system where fibroblasts and keratinocytes were randomly mixed, incorporated into type I collagen gels, and allowed to sort. Keratinocytes formed distinctive cellular masses in which the keratinocytes were organized such that the exterior most layer of cells exhibited characteristics of basal keratinocytes and the interior most cells exhibited characteristics of terminally differentiated keratinocytes. In the presence of papillary dermal fibroblasts, keratinocyte masses were highly symmetrical and cells expressed all levels of differentiation markers. In contrast, keratinocyte masses that formed in the presence of reticular fibroblasts tended to have irregular shapes, and terminal differentiation was suppressed. Furthermore, basement membrane formation was retarded in the presence of reticular cells. These studies indicate that site-matched papillary and reticular dermal fibroblasts qualitatively differ in their support of epidermal cells, with papillary cells interacting more effectively than corresponding reticular cells.

Effect of cyclosporin A on human gingival fibroblast collagen turnover in relation to the development of gingival overgrowth: an in vitro study

In a significant number of cases (25-81%) immunosuppressant treatment with cyclosporin A (CsA) is associated with gingival overgrowth, seriously interfering with the functions of mastication and speech. In CsA-induced gingival enlargement, quantitative modifications of the extracellular matrix components occur, and collagen (COL) metabolism and matrix metalloproteinases (MMPs) have been suggested as being the main targets. Since the mechanisms at the basis of CsA-induced gingival overgrowth are not yet completely understood, our aim was to analyze the effect of CsA on COL turnover in cultured human gingival fibroblasts. Cultured human gingival fibroblasts from four healthy volunteers were incubated with CsA (800 ng/ml) or with its vehicle (VH) for variable intervals of time (24, 48, 72 h). Fibroblast morphology was studied by light and electron microscope. Collagen type I (COL-I), MMP-1, MMP-2, TIMP-1 and TGF-beta1 mRNA were determined by RT-PCR; COL-I and MMP-1 by dot blot, and MMP-2 by zymography. Our results evidenced an up-regulation of COL-I and TGF-beta1 gene expression 72 h after CsA treatment. MMP-1, MMP-2 and TIMP-1 mRNA levels are affected but not significantly. Protein analysis revealed COL-I increase at all the considered times and, 72 h after CsA treatment, reduced collagenolytic levels. Our data suggest that COL accumulation during CsA-induced gingival overgrowth may be mainly sustained by an altered COL-I degradation due to decreased MMP-1 activity. However, interindividual differences of collagenase levels after CsA treatment suggest that a genetic predisposition to develop gingival overgrowth may be relevant.

Dermal fibroblasts from different layers of human skin are heterogeneous in expression of collagenase and types I and III procollagen mRNA

Patients with diabetic neuropathy have reduced numbers of cutaneous nerves, which may contribute to an increased incidence of nonhealing wounds. Nerve growth factor (NGF) has been reported to augment wound closure. We hypothesized that topical 2.5S NGF, a biologically active subunit of the NGF polymer, would accelerate wound repair, augment nerve regeneration, and increase inflammation in excisional wounds in diabetic mice. A full-thickness 6-mm punch biopsy wound was created on the dorsum of C57BL/6J-m+ Leprdb mice (db/db) and heterozygous (db/-) littermates and treated daily with normal saline or 2.5S NGF (1 microg/day or 10 microg/day) on post-injury days 0-6. Time to closure, wound epithelialization, and degree of inflammation were compared using a Student's t-test. Color subtractive-computer-assisted image analysis was used to quantify immunolocalized nerves in wounds. Non-overlapping (20x) digital images of the wound were analyzed for nerve profile counts, area density (number of protein gene product 9.5 positive profiles per unit dermal area) and area fraction (protein gene product 9.5 positive area per unit dermal area). Healing times in db/db mice decreased from 30 days in normal saline-treated mice to 26 days in mice treated with 1 microg/day NGF (p<0.05) and 24 days in mice treated with 10 microg/day NGF (p<0.02). A similar trend in db/- mice was not significant. NGF treatment augmented epithelialization in the db/db mice (p<0.05). Histological evaluation of inflammation in healed wounds showed no statistical difference between treatment groups. Total nerve number, area density, and area fraction were increased in NGF-treated wounds at 14, 21, and 35 days (p<0.05). The 2.5 NGF subunit may improve wound closure kinetics by promoting epithelialization and nerve regeneration. Further studies to determine the role of nerves in wound repair are warranted.

Cyclosporin A induces proliferation in human gingival fibroblasts via induction of transforming growth factor-beta1

BACKGROUND

Cyclosporin A (CsA) is a widely used immunosuppressant that causes significant side effects including gingival overgrowth. The pathogenesis of this condition is not fully understood; however, recent studies show that CsA regulates the transcription of several cytokines including transforming growth factor-beta 1 (TGF-beta1). In this study, we evaluated the effects of CsA and TGF-beta1 on human normal gingival (NG) fibroblast proliferation, and explored a possible autocrine stimulation of TGF-beta1 as a cellular regulator of proliferation induced by CsA in NG fibroblasts.

METHODS

NG fibroblast cell lines were incubated with increasing concentrations of CsA or TGF-beta1 and the proliferation index determined by automatic cell counting, BrdU incorporation, PCNA expression, and mitotic potential. To determine the effect of TGF-beta1 on the proliferation rate of NG fibroblasts under CsA treatment, NG fibroblast cultures were simultaneously treated with CsA and antisense oligonucleotides against the translation-start site of the TGF-beta1 mRNA.

RESULTS

Treatment of NG fibroblasts with CsA or TGF-beta1 significantly stimulated the cell proliferation in a dose-dependent manner. Furthermore, neutralization of TGF-beta1 production in CsA-treated NG fibroblasts inhibited CsA's effect on NG fibroblast proliferation, demonstrating an autocrine stimulatory effect of TGF-beta1 in CsA-treated NG fibroblast proliferation.

CONCLUSION

The results presented here suggest that CsA stimulatory induction of NG fibroblast proliferation is mediated via TGF-beta1 in an autocrine fashion.

Secreted Frizzled-related Protein 1 (SFRP1) Protects Fibroblasts from Ceramide-induced Apoptosis

Secreted frizzled-related proteins (SFRPs) are soluble proteins that have highly restricted tissue distribution. Although not fully understood, a role of SFRP1 in the regulation of apoptosis has been suggested. Our previous study disclosed a much greater level of SFRP1 expression in periodontal ligament fibroblasts (PDLFs), which have been suggested to maintain a reduced level of apoptosis compared with gingival fibroblasts. We have tested the role of SFRP1 in the regulation of fibroblast apoptosis both in vitro and in vivo. Our data showed that SFRP1 was significantly up-regulated in cultured human PDLFs during ceramide-induced apoptosis. In vivo study demonstrated an increased SFRP1 expression in mice periodontal ligament during force-induced apoptosis. While inhibition of endogenous SFRP1 increased the percentage of cell death in cultured human PDLFs, exogenous SFRP1 substantially reduced apoptosis in cultured human gingival fibroblasts, which do not maintain a high level of endogenous SFRP1 expression. The effect of SFRP1 on apoptosis was linked to the regulation of several apoptosis-related genes, including p53, caspase-3, caspase-9, and BCL-2-interacting killer (BIK). Furthermore our results indicated that the addition of exogenous SFRP1 could reduce the level of apoptosis in dermal fibroblasts in vivo, and this effect was also linked to the regulation of similar apoptosis-related genes as observed in in vitro studies. Collectively our results suggest that the constitutive up-regulation of SFRP1 could be an adaptive cell survival mechanism inherent to functionally specialized fibroblasts, and the addition of SFRP1 may contribute to the inhibition of apoptosis in fibroblast-related cells.

Porphyromonas gingivalis lipopolysaccharide signaling in gingival fibroblasts-CD14 and Toll-like receptors

Periodontal disease is the major cause of adult tooth loss and is commonly characterized by a chronic inflammation caused by infection of oral bacteria. Porphyromonas gingivalis (P. gingivalis) is one of the suspected periodontopathic bacteria and is frequently isolated from the periodontal pockets of patients with chronic periodontal disease. The lipopolysaccharide (LPS) of P. gingivalis is a key factor in the development of periodontitis. Gingival fibroblasts, which are the major constituents of gingival connective tissue, may directly interact with bacteria and bacterial products, including LPS, in periodontitis lesions. It is suggested that gingival fibroblasts play an important role in the host responses to LPS in periodontal disease. P. gingivalis LPS enhances the production of inflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor alpha (TNF-alpha) in gingival fibroblasts. However, the receptor that binds with P. gingivalis LPS on gingival fibroblasts remained unknown for many years. Recently, it was demonstrated that P. gingivalis LPS binds to gingival fibroblasts. It was also found that gingival fibroblasts express CD14, Toll-like receptor 4 (TLR4), and myeloid differentiation primary response gene 88 (MyD88). P. gingivalis LPS treatment of gingival fibroblasts activates several intracellular proteins, including protein tyrosine kinases, and up-regulates the expression of monocyte chemoattractant protein-1 (MCP-1), extracellular signal-regulated kinase 1 (ERK1), and signal-regulated kinase 2 (ERK2), IL-1 receptor-associated kinase (IRAK), nuclear factor-kappaB (NF-kappaB), and activating protein-1 (AP-1). These results suggest that the binding of P. gingivalis LPS to CD14 and TLR4 on gingival fibroblasts activates various second-messenger systems. In this article, we review recent findings on the signaling pathways induced by the binding of P. gingivalis LPS to CD14 and Toll-like receptors (TLRs) in gingival fibroblasts.

Regulatory mechanisms of periodontal regeneration

The periodontal ligament, located between the cementum and the alveolar bone, has a width ranging from 0.15 to 0.38 mm. Regeneration and homeostasis of the periodontal ligament are highly significant functions in relation to periodontal therapy, tooth transplantation or replantation, and orthodontic tooth movement. The purpose of this review is to discuss the regulatory mechanisms of regenerative and homeostatic functions in the periodontal ligament based on currently published studies and also on our own experimental data. We consider the capability of the ligament tissue to promote or to suppress calcification in connection with bone and cementum formation and the maintenance of the periodontal ligament space. Also discussed are the involvement of the periodontal ligament tissue in the regenerative ability, cell proliferation, growth and differentiation factors, extracellular matrix proteins, homeostatic phenomena, function of Malassez epithelial rests, tooth movement, or occlusal loading. Regulatory mechanisms for regeneration and homeostasis of the periodontal ligament are hypothetically proposed.

Effect of transforming growth factor-beta1, interleukin-6, and interferon-gamma on the expression of type I collagen, heat shock protein 47, matrix metalloproteinase (MMP)-1 and MMP-2 by fibroblasts from normal gingiva and hereditary gingival fibromatosis

BACKGROUND

Increased collagen and extracellular matrix deposition within the gingiva is the main characteristic feature of hereditary gingival fibromatosis (HGF). To date, it is not well established if these events are a consequence of alterations in the collagen and other extracellular matrix molecules synthesis or disturbances in the homeostatic equilibrium between synthesis and degradation of extracellular matrix molecules. Cytokines are important regulators of expression of the profibrogenic genes, including type I collagen and its molecular chaperone heat shock protein (Hsp)47 and proteolytic enzymes degrading extracellular matrix such as matrix metalloproteinases-1 and -2 (MMP-1 and MMP-2).

METHODS

In this study, we analyzed the expression and production of type I collagen, Hsp47, MMP-1, and MMP-2 in normal gingiva (NG) and HGF fibroblasts, and investigated the effects of transforming growth factor-beta1 (TGF-beta1), interleukin-6 (IL-6) and interferon-gamma (IFN-gamma) on the expression of these genes by NG and HGF fibroblasts.

RESULTS

Our results obtained from semi-quantitative reverse transcription-polymerase chain reactions (RT-PCR), Western blots, enzyme-linked immunosorbent assays (ELISA), and enzymographies clearly demonstrated that the expression and production of type I collagen and Hsp47 were significantly higher in fibroblasts from HGF than from NG, whereas MMP-1 and MMP-2 expression and production were lower in fibroblasts from HGF patients. Addition of TGF-beta1 and IL-6, which are produced in greater amounts by HGF fibroblasts, promoted an increase in type I collagen and Hsp47 and a decrease in MMP-1 and MMP-2 expression. IFN-gamma reduced both type I collagen and Hsp47 expression, whereas it had a slight effect on the expression of MMP-1 and MMP-2.

CONCLUSION

These patterns of expression and production suggest that enhanced TGF-beta1 and IL-6 production simultaneously increase the synthesis and reduce the proteolytic activities of fibroblasts from patients with HGF, which may favor the accumulation of extracellular matrix observed in patients with this condition.

Oral fibroblasts produce more HGF and KGF than skin fibroblasts in response to co-culture with keratinocytes

The production of hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) in subepithelial fibroblasts from buccal mucosa, periodontal ligament, and skin was determined after co-culture with keratinocytes. The purpose was to detect differences between the fibroblast subpopulations that could explain regional variation in epithelial growth and wound healing. Normal human fibroblasts were cultured on polystyrene or maintained in collagen matrix and stimulated with keratinocytes cultured on membranes. The amount of HGF and KGF protein in the culture medium was determined every 24 h for 5 days by ELISA. When cultured on polystyrene, the constitutive level of KGF and HGF in periodontal fibroblasts was higher than the level in buccal and skin fibroblasts. In the presence of keratinocytes, all three types of fibroblasts in general increased their HGF and KGF production 2-3 times. When cells were maintained in collagen, the level of HGF and KGF was decreased mainly in skin cultures. However, in oral fibroblasts, induction after stimulation was at a similar level in collagen compared to on polystyrene. Skin fibroblasts maintained in collagen produced almost no HGF whether with or without stimulation. The results demonstrate that the secretion of KGF and HGF in both unstimulated fibroblasts and in fibroblasts co-cultured with keratinocytes is dependent on the type of fibroblasts. In general, the periodontal fibroblasts had the highest level of cytokine production. This high level of growth factor production may influence the proliferation and the migration of junctional epithelium and thereby influence the development of periodontal disease.

Evaluation of matrix metalloproteinase-1 and tissue inhibitor of metalloproteinase-1 levels in gingival fibroblasts of cyclosporin A-treated patients

BACKGROUND

Cyclosporin A (CsA) is a potent immunosuppressant used to prevent organ transplant rejection and to treat various autoimmune diseases. CsA-induced gingival overgrowth (CsA GO) is the most widely seen side effect of this drug; its pathogenesis is not completely understood. The aim of this study was to identify and compare matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) levels in gingival fibroblast cultures of tissues derived from renal transplant patients receiving CsA and exhibiting gingival overgrowth and from periodontally healthy control subjects.

METHODS

Gingival overgrowth samples were obtained from patients undergoing therapy with CsA, and control tissues were obtained from systemically healthy donors. Gingival fibroblasts were grown using explant cultures. Three different study groups were identified: 1) CsA GO fibroblast culture; 2) CsA-treated healthy gingival fibroblast culture (H+CsA); and 3) healthy gingival fibroblast culture (H). The levels of MMP-1 and TIMP-1 in these groups of gingival fibroblasts were analyzed by enzyme-linked immunoabsorbent assay (ELISA).

RESULTS

The levels of TIMP-1 were significantly lower in CsA GO than H (P < 0.05). There was no statistically significant difference in the levels of MMP-1 between H and CsA GO (P = 0.505). The ratio of MMP-1 to TIMP-1 was significantly higher in CsA GO than H (P < 0.05).

CONCLUSIONS

The results of this study indicate that CsA therapy does not have a significant effect on MMP-1 levels. However, low TIMP-1 levels can be an important factor in the pathogenesis of CsA GO, since the balance between MMP-1 and TIMP-1 levels was changed by CsA.

Cytokine regulation of syndecan-1 and -2 gene expression in human periodontal fibroblasts and osteoblasts

Cell-surface proteoglycans participate in several biological functions including interactions with a variety of growth factors and cytokines. Regulation of syndecan-1 and -2 gene expression was investigated in human periodontal ligament fibroblasts (PDLF), osteoblasts (OB) and gingival fibroblasts (GF), in response to platelet-derived growth factor (PDGF-BB), transforming growth factor (TGF-beta 1), and interleukin (IL-1 beta) by Northern blot analyses. We also compared the effect of PDGF-BB and TGF-beta 1, separately and in combination, in the prolonged presence of IL-1 beta on the expression of both syndecan genes. The results demonstrated that the three cell lines regulated the expression of syndecan-1 and -2 in response to growth factors and cytokines in different manners. These cell lines increased syndecan-1 mRNA levels in response to either PDGF-BB or TGF-beta 1 and decreased levels in response to IL-1 beta. The effect of IL-1 beta on syndecan-1 mRNA synthesis was partially reversed after adding PDGF-BB and TGF-beta 1, separately or in combination, in the presence of IL-1 beta. In contrast, syndecan-2 mRNA level was markedly upregulated in response to either TGF-beta 1 or IL-1 beta in OB when compared with the other two cell lines. However, the stimulatory effect of TGF-beta 1 on syndecan-2 mRNA production in OB was abolished in the prolonged presence of IL-1 beta. These findings lend support to the notion that syndecan-1 and syndecan-2 have distinct functions which correlate with their source and functions within the periodontium.

Effect of cigarette smoking on human PDL fibroblasts attachment to periodontally involved root surfaces in vitro

BACKGROUND/AIM

Cigarette smoking is one of the most significant risk factors in the development and further advancement of inflammatory periodontal disease. However, no study has been performed to investigate the effect of smoking on the attachment of human periodontal ligament fibroblasts to either periodontally diseased or healthy roots. The present study was conducted to evaluate the attachment of fibroblasts derived from healthy human periodontal ligament (PDL) to periodontally diseased root surfaces of smokers.

METHOD

The subjects included 14 smokers and seven nonsmokers with at least a single periodontally involved anterior tooth planned for extraction. In addition, seven impacted third molars, which had been removed from nonsmoking adolescents, were used as a healthy control. The smoking status of each patient was determined by classifying the volunteers into four groups according to their level of cigarette consumption at the initial examination (seven patients each). Nonsmoking subjects who had never smoked cigarettes and had healthy periodontium were called healthy control (G1). In subjects with periodontal diseases, nonsmoking subjects who had never regularly smoked cigarettes (< 2 cigarettes/week) were called positive control (G2), smokers consuming <or=19 cigarettes/day were placed in group G3, and smokers consuming >or=20 cigarettes/day were located in group G4. To exclude the effects of all local irritants except for the adsorbed tobacco products, all teeth were subjected to thorough scaling and root planing 1 week before extraction. After 1 week of meticulous home care and continued smoking experience, teeth were extracted and the periodontally involved test areas were prepared for PDL culturing. PDL cells were cultured on root segments for 24 h. Samples were prepared for SEM viewing, photographing and counting at x750 in a standard area.

RESULTS

The results of this study indicated that smokers' data (G3, G4) revealed a significant reduction of attached PDL cells when compared to that of nonsmokers' healthy and positive controls (G1, G2). No significant difference in the mean number of attached cells was found between data derived from smokers' groups (G3 vs. G4). The attached cells in all groups varied in shape; they were flatter in the control groups, while they were round in smokers' groups, with no dose-dependent effect.

CONCLUSION

The present results suggest that cigarette smoking compromises PDL cell adhesion to root planed surfaces, which might affect periodontal regeneration following therapy.

Differences in motility pattern between human buccal fibroblasts and periodontal and skin fibroblasts

Migration of fibroblasts from surrounding normal tissue into the wound bed is an important requirement for successful wound healing. This study investigated the motility pattern of buccal, periodontal and skin fibroblasts to determine whether differences in the wound healing efficiency at these sites can be explained by differences in the motile behavior of their respective fibroblast populations. The migratory characteristics were studied in a two-dimensional culture system. The migration of single cells was time-lapse video recorded at intervals of 15 min for a period of 6 h using a computer-assisted microscope work-station. For evaluation of cell morphology, cell contours were recognized semiautomatically and used for determination of cell area, cell spreading and number and length of processes. We found that the cellular displacement of the buccal fibroblasts was only approximately 50% of the cellular displacement of periodontal and skin fibroblasts. The decreased cellular displacement of the buccal fibroblasts was found to be due to both lower cellular speed and less persistence in direction. The buccal fibroblasts also displayed smaller areas and longer processes. The differences in cellular morphology and motility pattern amongst the three fibroblast types could not be explained by differences in secretion of extracellular matrix components and are therefore believed to reflect phenotypic differences amongst fibroblast subpopulations.

Effect of avocado and soybean unsaponifiables on gelatinase A (MMP-2), stromelysin 1 (MMP-3), and tissue inhibitors of matrix metalloproteinase (TIMP- 1 and TIMP-2) secretion by human fibroblasts in culture

BACKGROUND

In inflamed periodontal tissues, gingival fibroblasts are able to express matrix metalloproteinases (MMPs) and their natural inhibitors, tissue inhibitors of matrix metalloproteinases (TIMPs). They can also respond to growth factors and cytokines. In this study, the in vitro effects of avocado and soybean unsaponifiable residues (ASU), their fractions (avocado unsaponifiable [ASF] or soy unsaponifiable [SSF]) on MMP-2 and MMP-3, and the activity and secretion of their inhibitors TIMP-1 and TIMP-2 were investigated using cultured human gingival fibroblasts.

METHODS

Gingival fibroblasts were cultured for 72 hours with ASU, ASF, and SSF at concentrations of 0. 1, 0.5, 2.5, 5, and 10 microgram/ml of culture medium, after pretreatment or no pretreatment for 1 hour with interleukin-1beta (IL-1beta). MMP-2 and MMP-3 were detected and quantified in the culture media after zymography and image analysis. TIMP-1, TIMP-2, MMP-2, and MMP-3 were also evidenced by dot blotting and quantified by image analysis.

RESULTS

In the absence of IL-1beta, a slight decrease in the secretion of MMP-2 was observed with lower doses of ASU, ASF, and SSF. The decrease of MMP-3 secretion was clearly marked with all fractions especially at low concentrations (0.1 and 2.5 microgram/ml). A slight decrease in TIMP-2 secretion was seen for low doses of ASU, ASF, and SSF, while a small increase was seen at higher concentrations. Concerning TIMP-1, no significant variation was observed in culture medium for low concentrations, and a decrease was noted for 5 and 10 microgram/ml of ASU, ASF, and SSF. As anticipated, IL-1beta induced a marked release of MMP-2, MMP-3, and TIMP-1, but no variation for TIMP-2 was seen. ASU, ASF, and SSF reversed the IL-1beta effect on gingival fibroblasts for MMP-2 and MMP-3, particularly with doses varying from 0.1 to 2.5 microgram/ml and for TIMP-1, particularly with doses varying from 2.5 to 10 microgram/ml.

CONCLUSIONS

These findings suggest a potential role for avocado and soy unsaponifiable extracts to prevent the deleterious effects of IL-1beta that occur during periodontal diseases.

Transforming growth factor-beta1 autocrine stimulation regulates fibroblast proliferation in hereditary gingival fibromatosis

BACKGROUND

Hereditary gingival fibromatosis (HGF) is a rare oral disease characterized by a slow and progressive enlargement of both the maxilla and mandible gingiva. Increased proliferation, elevated synthesis of extracellular matrix, particularly collagen, and reduced levels of matrix metalloproteinases seem to contribute to the pathogenesis of gingival overgrowth in HGF patients. Transforming growth factor-beta1 (TGF-beta1) is an important cytokine thought to play a major role in fibrotic disorders such as HGF due to its ability to stimulate the synthesis and reduce the degradation of extracellular matrix. In HGF fibroblasts, TGF-beta1 autocrine stimulation reduces expression and production of matrix metalloproteinases. However, the role of TGF-beta1 in fibroblast growth modulation has not been established in this disease.

METHODS

The aim of this study was to confirm the increased proliferation rate of HGF fibroblast cell lines and to explore a possible autocrine role of TGF-beta1 as a cell growth stimulator by blocking production of this endogenous cytokine using 2 well-established systems: antisense oligonucleotides and neutralizing antibodies.

RESULTS

Four different cellular proliferation assays, bromodeoxyuridine labeling, argyrophilic nucleolar organizing region staining, proliferating cell nuclear antigen, and mitotic indexes, confirmed that fibroblasts from HGF proliferate significantly faster than those from normal gingiva. Antisense oligonucleotides reduced TGF-beta1 production as demonstrated by capture enzyme-linked immunosorbent assay, whereas TGF-beta1 expression levels were not significantly modified. Blocking TGF-beta1 synthesis with oligonucleotides or its activity with specific antibodies resulted in a decreased magnitude of HGF fibroblast proliferation.

CONCLUSION

These results are consistent with the existence of an autocrine role of TGF-beta1 as a stimulator of HGF fibroblast proliferation.

Heterogeneous expression of Toll-like receptor 4 and downregulation of Toll-like receptor 4 expression on human gingival fibroblasts by Porphyromonas gingivalis lipopolysaccharide

Porphyromonas gingivalis (P. gingivalis) is implicated in the initiation and progression of periodontitis. Human gingival fibroblasts (HGFs) are the major constituent of gingival connective tissue. P. gingivalis or its components such as lipopolysaccharide (LPS) upregulate the production of various inflammatory cytokines including interleukin (IL)-1 and IL-6 in HGFs. Recently, we demonstrated that the binding of P. gingivalis LPS to Toll-like receptor 4 (TLR4) on HGFs activates various second messenger systems (Biochem. Biophys. Res. Commun. 273, 1161-1167, 2000). In the present study, we examined the level of TLR4 expression on HGFs by flow cytometric analysis (FACS), and studied the levels of IL-1 and IL-6 in the culture medium upon LPS stimulation of HGFs by enzyme-linked immunosorbent assay (ELISA). Upon stimulation by P. gingivalis LPS for 24 h, HGFs that expressed a high level of TLR4 secreted significantly higher levels of IL-1 and IL-6 than HGFs that expressed a low level of TLR4. On the other hand, after stimulation with P. gingivalis LPS for 24 h, the level of TLR4 on the surface of HGFs decreased. These results suggest that the level of TLR4 expression on HGFs reflects the extent of inflammation in the gingival tissue, and that P. gingivalis LPS downregulates TLR4 expression on HGFs. These findings may be used to control inflammatory and immune responses in periodontal disease.

The putative collagen binding peptide hastens periodontal ligament cell attachment to bone replacement graft materials

BACKGROUND

Bone replacement graft (BRG) materials are often used to treat periodontal defects, to promote cellular invasion, and to encourage bone regrowth. Periodontal ligament fibroblasts (PDLF) incorporate these materials and form the basis of the renewed connection between the existing and newly formed alveolar bone and the tooth surface. A peptide (P-15) that mimics the putative cell-binding domain of collagen has been reported to promote dermal fibroblast attachment and proliferation.

METHODS

PDLF were quantitatively examined for their ability to adhere to a variety of BRG materials fluorometrically. In addition, scanning electron microscopy was used to examine the changes in morphology exhibited by these cells as they attached and spread on several BRG materials. Finally, BRG materials containing the P-15 peptide were quantitatively examined for their ability to promote PDLF attachment and proliferation.

RESULTS

Freeze-dried allograft bone supports greater PDLF attachment than does several xenograft and alloplastic anorganic bone replacement materials. An anorganic BRG material containing the P-15 peptide promoted more rapid cell attachment and spreading than a similar anorganic BRG material lacking this peptide. Finally, none of the BRG materials examined promoted PDLF proliferation.

CONCLUSIONS

Our data indicate that the addition of the P-15 peptide increases the rapidity of PDLF attachment to xenogeneic bone replacement materials. This increase in the rate of attachment may have clinical significance in the context of the dynamic regulation of cell attachment during periodontal regeneration. However, this peptide does not promote an increase in stable cell attachment or proliferation in vitro.

Delayed wound healing in aged rats is associated with increased collagen gel remodeling and contraction by skin fibroblasts, not with differences in apoptotic or myofibroblast cell populations

Aging has been anecdotally reported to result in prolonged wound healing. Measurement of punch biopsy wound closure in young (4 month old) and old (36 month old) rats indicated there was a significant delay in wound closure by old rats during the early phase of repair, after which closure rates were equivalent. The delay in granulation tissue accumulation in older animals could involve premature programmed cell death (apoptosis); however, apoptotic fibroblasts in sponge granulation tissue and tissue culture were less abundant in samples from old rats relative to young rats. Myofibroblasts express alpha-smooth muscle actin, and they are believed to be important in wound contraction. There were no significant differences in overall abundance or distribution of alpha-smooth muscle actin containing myofibroblasts in granulation tissue and in cultured granulation tissue fibroblasts regardless of the age of the donor rat. The spatial distribution of myofibroblasts and apoptotic cells was distinct. Fibroblasts from granulation tissue and skin explants were placed in a collagen gel contraction assay prior to the 5th passage to determine their in vitro contractility. While granulation tissue fibroblasts from young and old rats showed similar collagen gel contractility, skin fibroblasts from old rats displayed greater collagen gel contractile behavior than young skin fibroblasts. Greater gel contractility of fibroblasts from old rats appeared to result, in large part, from the ability of those cells to cause generalized gel degradation. Gelatin zymography indicated a greater abundance of matrix metalloproteinase-2 in supernatants from gels containing skin fibroblasts from old rats. Taken together, these results suggest that the age-associated healing delay in the rat may not be related to the appearance or abundance of distinct myofibroblast or apoptotic cell populations. Proteolysis may have a significant role in delayed wound healing in aged animals.

Isolation and characterization of cultured human periodental ligament fibroblast-specific cDNAs

The molecular mechanisms that control the function of periodontal ligament (PDL) fibroblasts remain unclear. We speculated that the character of differentiating PDL fibroblasts is defined by the altered expansion of specific genes not found in neighboring gingival fibroblasts in the periodontium. To expand this set, subtractive hybridization was applied between cultured human PDL and gingival fibroblasts to identify genes differentially expressed in PDL. Consequently five candidate clones, PDLs (periodontal ligament specific) 5, -17, -22, -25, and -31 were identified and characterized by homology search, Northern analysis, and in situ hybridization. Although the mRNAs of these clones were expressed by bone marrow cells and rarely by gingival fibroblasts, the highest expression was detected in the PDL cells, which were uniformly distributed throughout the whole PDL. Amongst the five candidate clones, we focused on PDLs17, because it is a hypothetical protein whose biological function has not been reported yet in the database. Polyclonal antiserum raised against PDLs17 peptide was made, and stained the PDL fibroblasts, osteoblast-like cells and stromal cells in the bone marrow, but not gingival fibroblasts. The results suggest that clones, PDLs5, -17, -22, -25, and -31 may be used as PDL fibroblast-specific markers, and that PDLs17 could act as an important factor in the differentiation process of PDL fibroblasts.

Comparação microscópica e proliferativa de fibroblastos gengivais de pacientes com gengiva normal e com fibromatose gengival hereditária

Fibromatose gengival hereditária (FGH) é uma condição bucal rara clinicamente manifestada por um aumento gengival generalizado e fibrótico, podendo apresentar-se de forma isolada ou associada a outras alterações, como parte de síndromes. Os mecanismos biológicos envolvidos na FGH são desconhecidos, e os resultados de estudos de cultura celulares são controversos. Para elucidar as características fenotípicas dos fibroblastos de FGH, nós isolamos quatro linhagens celulares de fibroblastos de FGH de indivíduos de uma mesma família e comparamos as características morfológicas e proliferativas com fibroblastos provenientes de pacientes com gengiva clinicamente normal (GN). Fibroblastos de GN e FGH em condições de subconfluência celular apresentaram típicas características morfológicas, como formato fusiforme, núcleo central e longos prolongamentos citoplasmáticos, mas em condições de saturação da densidade celular, os fibroblastos de FGH apresentaram dimensões menores que as células controle. A relação núcleo/citoplasma foi sempre menor para todas as linhagens celulares de fibroblastos de FGH, sugerindo que a redução celular, é proveniente de uma redução ou compactação citoplasmática e não nuclear. A capacidade proliferativa de fibroblastos de FGH foi maior que a de fibroblastos de GN. Estes resultados sugerem que diferenças morfológicas e proliferativas dos fibroblastos de FGH podem estar associadas aos eventos biológicos envolvidos na etiopatogenia do aumento gengival observado em pacientes com FGH.

Enamel matrix-derived protein stimulates attachment of periodontal ligament fibroblasts and enhances alkaline phosphatase activity and transforming growth factor beta1 release of periodontal ligament and gingival fibroblasts

BACKGROUND

Although it is claimed that enamel matrix-derived proteins (EMP) can be used to promote new attachment formation around periodontally involved teeth, the underlying biological mechanism is not understood. It was the aim of the present study to investigate the effects of EMP on the behavior of human periodontal ligament (HPLF) and gingival fibroblasts (HGF) in vitro, with special focus on their attachment properties, the expression of alkaline phosphatase (ALP) activity, the release of transforming growth factor (TGF)beta1, and their proliferative rate.

METHODS

Fibroblast populations were obtained from 10 individuals with a healthy periodontium and cultured in chemically defined medium on culture plates coated with EMP, purified collagen type I, or their respective vehicles. Experiments were performed in the absence of serum for periods up to 48 hours.

RESULTS

It was shown that HGF barely attached and spread on EMP-coated substrata, whereas HPLF attached and spread within 24 hours. However, when cultured on purified collagen type I, both cell types showed rapid attachment and spreading. Furthermore, the expression of ALP activity was significantly enhanced under the influence of EMP, especially in HPLF. HPLF and HGF both released significantly higher levels of TGFbeta1 in the presence of EMP. EMP did not influence 3H-thymidine incorporation by HPLF and HGF.

CONCLUSIONS

Our results indicate that HPLF and HGF respond differently to EMP. A more rapid attachment of HPLF to this substratum might contribute, during the initial stages of periodontal healing, to selective outgrowth and colonization of exposed root surfaces in vivo.

Retroviral transduction of human periodontal cells with a temperature-sensitive SV40 large T antigen

The periodontal ligament (PDL) is considered to contain subpopulations of cells responsible for the development, repair and regeneration of the periodontium. Cell cultures have been used as model systems in order to understand the complex cellular and biochemical events underlying these processes. In order to obtain long-term cultures of these cells that can be cloned and characterized, primary cultures of PDL and gingival cells were infected with an amphotropic retroviral construct encoding a temperature-sensitive SV40 large T antigen (tsT). After selection for drug resistance, the cells expressed the T antigen and proliferated at 34 degrees C for more than 40 passages. However, when the T antigen was inactivated by incubation at 39 degrees C, the cultures became growth-arrested and the granularity of the cells increased, possibly as a result of differentiation. Reverse transcribed-polymerase chain reaction and flow cytometry showed that the tsT-transduced cells expressed a number of soft and hard connective-tissue antigens, including osteocalcin, osteonectin, osteopontin, collagen type I and alkaline phosphatase. Moreover, incubation of the transduced PDL cells at 39 degrees C was found to upregulate the expression of osteocalcin, osteopontin and collagen type I, but downregulate osteonectin. At this temperature, the presence of the dexamethasone downregulated type I collagen, while vitamin D3 had no effect on the expression of any of the antigens examined. Under all culture conditions, antigen expression was far higher in the transduced PDL cells than the gingival cells. The findings thus show that growth of the tsT-transduced PDL and gingival cells is temperature-dependent and that the presence of the T antigen increases their lifespan but does not ablate the expression of certain of their characteristic phenotypic and functional features.

IL-10 inhibits Porphyromonas gingivalis LPS-stimulated human gingival fibroblasts production of IL-6

Lipopolysaccharides (LPS) of Porphyromonas gingivalis have been implicated in the initiation and development of periodontal diseases. In a previous study, we investigated the signal transduction pathway of P. gingivalis and demonstrated that LPS stimulates the production of interleukin (IL)-6 in human gingival fibroblasts (HGFs), which in turn activates osteoclasts in vitro. The cytokine, IL-10, was initially described as cytokine synthesis inhibitory factor. In this study, we examined that effect of IL-10 on P. gingivalis LPS-induced human gingival fibroblast production of IL-6. LPS-induced IL-6 production was inhibited by IL-10 in a dose-dependent manner. Flow cytometric analysis showed that HGFs bind to fluorescein-isothiocyanate (FITC) labeled IL-10. Western blotting analysis demonstrated the expression of IL-10 receptor on the cell surface of these cells. Engagement of LPS initiated the protein tyrosine phosphorylation of several intracellular proteins including extracellular signal-regulated kinase 2 (ERK2), and these events were suppressed by IL-10. These results suggest that IL-10 inhibits the inflammatory response via the IL-10 receptor in P. gingivalis LPS-initiated periodontal diseases.

Nodular fasciitis and solitary fibrous tumor of the oral region: tumors of fibroblast heterogeneity

OBJECTIVE

Fibroblastic proliferations of the oral cavity are extremely varied, yet they share certain features-spindle cell morphology, collagen synthesis, and fasciculation. Nodular fasciitis is a cellular fibroblastic lesion, uncommonly located in the oral submucosa, that shows smooth muscle actin (SMA) immunoreactivity. Solitary fibrous tumor expresses a CD34 fibroblast phenotype. The aim of this study is to report instances of nodular fasciitis and solitary fibrous tumor in the orofacial region and investigate immunohistochemical markers to compare and contrast fibroblastic phenotypic heterogeneity in these tumors.

STUDY DESIGN

Seven benign cellular fibrogenic tumors initially diagnosed as nodular fasciitis over a 10-year period were examined. Immunohistochemical markers, including S-100 protein, SMA, CD68, CD34, and vimentin, were used to further characterize these lesions.

RESULTS

All tumors occurred in adults, and the buccal mucosa was found to be the favored site. The spindle cells in these tumors showed phenotypic heterogeneity both within and between tumors. All were vimentin-reactive and harbored small populations of CD68-positive macrophage/dendrocytes. Five tumors were SMA-positive and CD34-negative; the tumor in one case was SMA-negative and CD34-positive, and that in another was SMA-positive and CD34-positive.

CONCLUSION

Although rare, nodular fasciitis and solitary fibrous tumor arise in oral submucosa, usually in the cheek. The histopathologic features and immunomarkers indicative of myofibroblastic differentiation are seen in nodular fasciitis, whereas solitary fibrous tumor is CD34-positive; however, one instance was found to be positive for both markers. All of these cases harbored subpopulations of CD68-positive cells. Immunomarkers are a valuable adjunct in differentiating nodular fasciitis from solitary fibrous tumor, yet some tumors may harbor heterogeneous fibroblast phenotypes.

Analysis of NO synthase expression in neuronal, astroglial and fibroblast-like derivatives differentiating from PCC7-Mz1 embryonic carcinoma cells

We studied the expression of the NO synthase isoforms in an in vitro model of neural development using RT-PCR, Western blot and immunohistochemistry. Murine PCC7-Mz1 cells (Jostock et al., Eur. J. Cell Biol. 76, 63-76, 1998) differentiate in the presence of all-trans retinoic acid and dibutyryl cAMP along the neural pathway into neuron-like, fibroblast-like and astroglia-like cells. Undifferentiated cells showed immunofluorescent staining for neuronal-type NOS I and endothelial-type NOS III. This expression pattern was retained in those cells differentiating into neurofilament- and tau protein-positive neuronal cells. Thymocyte alloantigen (Thy1.2/CD 90.2)-positive fibroblasts, appearing around day 3, and glial fibrillary acidic protein (GFAP)-positive astroglial cells, appearing after day 6 of differentiation, stained negative for any NOS isoform. Starting at day 6 of differentiation, expression of inducible-type NOS II could be stimulated with cytokines in a subset of cells, which may represent activated astrocytes. NOS II was always undetectable in non-induced cultures. These data indicate that the ability of stem cells to express NOS I and NOS III is only retained when the cells differentiate along the neuronal lineage, while a small subpopulation of cells acquires the ability to express NOS II in response to cytokines.

The proteoglycans of human cementum: immunohistochemical localization in healthy, periodontally involved and ageing teeth

Cementum is believed to play a regulatory role in periodontal regeneration through a variety of macromolecules present in its extracellular matrix (ECM), among which are the proteoglycans (PG). The PG of human cementum have not been fully characterized. This study has used a standard indirect immunoperoxidase technique to investigate the presence and distribution of PG species within the ECM of human cementum. Freshly extracted human permanent teeth were separated into 8 age groups; each group was subdivided to include healthy and periodontally involved teeth, which were then fixed, demineralized and wax-embedded. Sections were incubated with polyclonal antibodies recognizing protein core epitopes in the large chondroitin sulphate PG versican and the small interstitial PG decorin, biglycan, fibromodulin and lumican. Immunoreactivity to versican, decorin, biglycan and lumican was evident at the borders and lumina of a proportion of lacunae and canaliculi surrounding cementocytes in cellular cementum, as well as on inserted periodontal ligament (PDL) fibres. Biglycan was also present along incremental lines in cellular cementum, whereas staining for fibromodulin was negative. In acellular cementum, no immunoreactivity was evident with any of the antibodies used except on inserted PDL fibres. These results indicate that versican, decorin, biglycan and lumican are components of the ECM of cellular, but not of acellular cementum. Neither age nor periodontal diseases appear to qualitatively influence the PG population of cementum. The distribution of PG epitopes around a proportion of cementocytes suggests the existence of different cementocyte subpopulations, or a differential response of these cells to yet undefined stimuli.

Possible role of monkey gingival fibroblasts in external basement membrane maintenance

Morphological and immunocytochemical investigations were made of the interface between the junctional epithelium and connective tissue in gingiva from young monkeys (Macaca fuscata). Some fibroblasts with conspicuous cytoplasmic organelles, including the elements of rough endoplasmic reticulum, the Golgi apparatus, and mitochondria, were found close to the external basement membrane in the connective tissue underlying the junctional epithelium. Occasionally, cytoplasmic cell processes either made contact with the lamina densa of the basement membrane or came into direct contact with the plasma membrane of the basal layer of junctional epithelium cells. Fragments of a structure like that of the basement membrane were observed between the process and the basal cells. Fibroblasts could be seen very close to the disrupted portion created by the passage of leukocytes migrating into the junctional epithelium through the external basement membrane. Immunoperoxidase methods demonstrated a positive reaction product for laminin on the external basement membrane. This product was observed in the rough endoplasmic reticulum of junctional epithelium cells and of gingival connective tissue fibroblasts located close to the junctional epithelium basement membrane. The cytoplasm of fibroblasts distant from the epithelium, however, demonstrated no immunoreactivity. These results suggest that, in cooperation with epithelial cells, some fibroblasts located near the junctional epithelium can produce such basement membrane components as laminin and that these components may serve to stabilize and/or restore previously assembled basement membrane.

Involvement of CD14 on human gingival fibroblasts in Porphyromonas gingivalis lipopolysaccharide-mediated interleukin-6 secretion

The lipopolysaccharides (LPS) of Porphyromonas gingivalis are implicated in the initiation and development of periodontal diseases. However, the mechanisms underlying P. gingivalis LPS-mediated periodontal destruction are still unknown. Here, it was found that P. gingivalis LPS activates human gingival fibroblasts (HGF) to release interleukin 6 (IL-6) via CD14. Flow-cytometric analysis showed that HGFs bind to fluorescein-isothiocyanate (FITC)-labelled LPS, and express CD14 on their surfaces. The binding of FITC LPS was competitively suppressed by unlabelled synthetic lipid A as well as by LPS. LPS-induced IL-6 production was inhibited by anti-CD14 monoclonal antibody in a dose-dependent manner. The binding of FITC LPS to HGF was abrogated by anti-CD14 monoclonal antibody. Engagement of LPS initiated the protein tyrosine phosphorylation of several intracellular proteins including extracellular signal-regulated kinase (ERK) 1 and 2, and these events were suppressed by the anti-CD14 monoclonal. These results suggest that CD14 is a cell surface binding site for LPS and is involved in the LPS-mediated activation of HGF.

Heterogeneous expression and release of CD14 by human gingival fibroblasts: characterization and CD14-mediated interleukin-8 secretion in response to lipopolysaccharide

To identify the role in periodontal inflammatory diseases of human gingival fibroblasts (HGF), the major constituents of gingival tissue, the expression of CD14, a possible lipopolysaccharide (LPS) receptor, and the release of soluble CD14 (sCD14) by HGF were examined. Among the HGF samples from the nine donors tested, more than 50% of the HGF from five donors expressed CD14 but less than 20% of HGF from the other four donors did so, as determined by flow cytometric analysis. The CD14 expression on the cell surface was correlated with the expression of CD14 mRNA. The HGF and skin and lung fibroblasts tested expressed no CD18, which indicates that fibroblasts do not possess other LPS receptors, such as CD11b/CD18 and CD11c/CD18. The CD14 expression by the HGF was decreased after subculturing and was highest at the confluent stage of culture. The treatment of high-CD14-expressing (CD14(high)) HGF with phosphatidylinositol-phospholipase C reduced CD14 expression; this result and the increase in a 55-kDa CD14 indicate that the membrane CD14 (mCD14) on the HGF may be a 55-kDa glycosylphosphatidylinositol-anchored protein. CD14(high) HGF spontaneously released 48- and 57-kDa sCD14. The total release of sCD14 by the HGF was augmented by gamma interferon and Escherichia coli LPS in accordance with the increased expression of mCD14. The CD14(high) HGF secreted interleukin-8 in response to LPS, and the secretion was completely inhibited by anti-CD14 antibody. These results suggest that (i) HGF consist of populations that are heterogeneous on the basis of different levels of expression of CD14 and (ii) CD14(high) HGF secrete inflammatory cytokines in response to LPS via CD14.

The scarring processes in mucosal tissues after immune injury

OBJECTIVES

An important feature of the healing processes is scar formation which may be necessary for organism survival. If it proceeds to the pathological state, it may impair normal function. The purpose of this review is to focus on some of the factors that may influence this process after immune injury, comparing it in the skin and mucosa.

METHODS

A detailed literature search of peer-reviewed journals was conducted. Studies reported in all languages considered relevant and important were used, including humans, animals, and tissue culture.

RESULTS

Analysis of the data indicate that the scarring process is mainly dependent on (1) the type of the lesion, (2) the cause and duration of injury, and (3) the tissue involved and its microenvironment. Equally important is the large spectrum and heterogenicity in the biological activity of fibroblasts and their role in scar formation.

CONCLUSIONS

The process of scar formation is complex and multistep process and is affected and influenced by local and systemic factors. Although it appears irreversible, there are pharmacological agents available, and under investigation, that may minimize its detrimental effects.

Keratinocyte growth factor mRNA expression in periodontal ligament fibroblasts

Keratinocyte growth factor (KGF) is a fibroblast growth factor which mediates epithelial growth and differentiation. KGF is expressed in subepithelial fibroblasts, but generally not in fibroblasts of deep connective tissue, such as fascia and ligaments. Here we demonstrate that KGF mRNA is expressed in periodontal ligament fibroblasts, and that the expression is increased upon serum stimulation. Fibroblasts from human periodontal ligament, from buccal mucosa, from gingiva, and from skin were established from explants. Alkaline phosphatase activity was used as an indicator of the periodontal nature of fibroblasts. Cells were first cultured in DMEM with 0.5% fetal calf serum (FCS) and then incubated for 8 h, and 72 h in fresh DMEM with 10% FCS. Total RNA was isolated and used for Northern blotting with a P32-labeled KGF cDNA probe. Total RNA from cultured keratinocytes was used as negative controls. KGF mRNA was found in all cultured fibroblasts. Upon addition of 10% FCS to the cell cultures, an increase in KGF mRNA levels was noticed especially after 72 h. Furthermore, RT-PCR analysis of material scraped from the tooth root surface indicated the presence of KGF mRNA even in noncultured periodontal ligament cells.