Expression of receptors for basic fibroblast growth factor on human periodontal ligament cells

Impact of FGF1 on human periodontal ligament fibroblast growth, osteogenic differentiation and inflammatory reaction in vitro

PURPOSE

To investigate in vitro the impact of fibroblast growth factor 1 (FGF1) in comparison to ascorbic acid (AscA) on human periodontal ligament fibroblast (HPdLF) growth, their osteogenic differentiation, and modulation of their inflammatory reaction to mechanical stress.

METHODS

The influence of different concentrations of FGF1 (12.5-200 ng/mL) on growth and proliferation of HPdLF cells was analyzed over 20 days by counting cell numbers and the percentage of Ki67-positive cells. Quantitative expression analysis of genes encoding the osteogenic markers alkaline phosphatase (ALPL), Runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), and osteopontin (OSP), as well as the fibroblast markers vimentin (VIM) and fibroblast-specific protein 1 (FSP1), was performed after 2 and 20 days of cultivation. Metabolic activity was determined by MTT assay. For comparison with AscA, 50 ng/mL FGF1 was used for stimulation for 2 and 20 days. Cell number, percentage of Ki67-positive cells, and expression of osteoblast- and fibroblast-specific genes were examined. Alkaline phosphatase activity was visualized by NBT/BCIP and calcium deposits were stained with alizarin red. Cytokine (IL‑6, IL‑8, COX2/PGE2) expression and secretion were analyzed by qPCR and ELISA in 6 h mechanically compressed HPdLF cultured for 2 days with FGF1 or ascorbic acid.

RESULTS

Higher concentrations of FGF1 promoted cell proliferation upon short-term stimulation, whereas prolonged treatment induced the expression of osteogenic markers even with low concentrations. AscA promotes cell growth more markedly than FGF1 in short-term cultures, whereas FGF1 induced osteogenic cell fate more strongly in long-term culture. Both factors induced an increased inflammatory response of HPdLF to mechanical compression.

CONCLUSION

Our data suggest that FGF1 promotes an osteogenic phenotype of HPdLF and limits inflammatory response to mechanical forces compared to AscA.

Construction of a human monoclonal antibody against bFGF for suppression of NSCLC

Compelling evidence implicates that overexpression of basic fibroblast growth factor (bFGF) and fibroblast growth factor receptor 1 (FGFR1) in non-small cell lung cancer (NSCLC) drives tumor progression, can serve as prognostic biomarkers or therapeutic targets for NSCLC patients. But at present, we still lack of effective drugs for bFGF. The preparation of monoclonal antibodies against bFGF or to understand its mechanism of action is urgently need. Previously, we used hybridoma technology to produce a murine anti-bFGF monoclonal antibody (E12). However, E12 carries risks of heterogeneity and immunogenicity. In the present work, we produced three humanized variants (H1L1, H2L2 and H3L3) based on E12 by substituting residues in or near the complementarity-determining region (CDR). In addition, we thoroughly explored VH/VL domain combinations to simulate full-length IgG1 antibodies using computational protein design. H3L3 was selected for further study, as it demonstrated the best humanization and strongest affinity for bFGF. Specially, humanization of H3L3's light chain and heavy chain were 100% and 98.89%, respectively. The FGF2 neutralizing effect of H3L3 were confirmed by ELISA. We also found that H3L3 can effectively suppress the growth and angiogenesis of cancer through reduce the phosphorylation of AKT and MAPK. Moreover, H3L3 dramatically reduced tumor size and micro-vessel density in nude mice. Altogether, our study demonstrates that H3L3 exerts anti-tumor effects by impeding NSCLC development.

PLAP-1/Asporin Positively Regulates FGF-2 Activity

PLAP-1 is an extracellular matrix protein that is predominantly expressed in the periodontal ligament within periodontal tissue. It was previously revealed that PLAP-1 negatively regulates bone morphogenetic protein 2 and transforming growth factor β activity through direct interactions. However, the interaction between PLAP-1 and other growth factors has not been defined. Here, we revealed that PLAP-1 positively regulates the activity of fibroblast growth factor 2 (FGF-2), a critical growth factor in tissue homeostasis and repair. In this study, we isolated mouse embryonic fibroblasts (MEFs) from Plap-1(-/-) mice generated in our laboratory. Interestingly, Plap-1(-/-) MEFs exhibited enhanced responses to bone morphogenetic protein 2 but defective responses to FGF-2, and Plap-1 transfection into Plap-1(-/-) MEFs rescued these defective responses. In addition, binding assays revealed that PLAP-1 promotes FGF-2-FGF receptor 1 (FGFR1) complex formation by direct binding to FGF-2. Immunocytochemistry analyses revealed colocalization of PLAP-1 and FGF-2 in wild-type MEFs and reduced colocalization of FGF-2 and FGFR1 in Plap-1(-/-) MEFs compared with wild-type MEFs. Taken together, PLAP-1 positively regulates FGF-2 activity through a direct interaction. Extracellular matrix-growth factor interactions have considerable effects; thus, this approach may be useful in several regenerative medicine applications.

The multifaceted role of the vasculature in endochondral fracture repair

Fracture healing is critically dependent upon an adequate vascular supply. The normal rate for fracture delayed or non-union is estimated to be between 10 and 15%, and annual fracture numbers are approximately 15 million cases per year. However, when there is decreased vascular perfusion to the fracture, incidence of impaired healing rises dramatically to 46%. Reduction in the blood supply to the fracture can be the result of traumatic injuries that physically disrupt the vasculature and damage supportive soft tissue, the result of anatomical location (i.e., distal tibia), or attributed to physiological conditions such as age, diabetes, or smoking. The role of the vasculature during repair is multifaceted and changes during the course of healing. In this article, we review recent insights into the role of the vasculature during fracture repair. Taken together these data highlight the need for an updated model for endochondral repair to facilitate improved therapeutic approaches to promote bone healing.

Periodontal fibroblasts modulate proliferation and osteogenic differentiation of embryonic stem cells through production of fibroblast growth factors

BACKGROUND

Periodontal ligament fibroblasts (PLFs) maintain homeostasis of periodontal ligaments by producing paracrine factors that affect various functions of stem-like cells. It is hypothesized that PLFs induce proliferation and differentiation of stem cells more effectively than gingival fibroblasts (GFs) and skin fibroblasts (SFs).

METHODS

PLFs and GFs were isolated from extracted teeth and cultured in the presence and absence of osteogenesis-inducing factors. Mouse embryonic stem (mES) cells and SFs were purchased commercially. mES cells were incubated with culture supernatants of these fibroblasts or cocultured directly with the cells. Proliferation and mineralization in mES cells were determined at various times of incubation. Immunostaining and polymerase chain reaction were performed. The activity of mitogen-activated protein kinase and alkaline phosphatase (ALP) was also measured.

RESULTS

In cocultures, PLFs stimulated proliferation of mES cells more effectively than GFs or SFs. Similarly, the addition of culture supernatant of PLFs induced the most prominent proliferation of mES cells, and this was significantly inhibited by treatment with antibody against fibroblast growth factor (FGF)4 or the c-Jun N-terminal kinase inhibitor SP600125 (anthra[1,9-cd]pyrazol-6(2H)-one). Supplementation with culture supernatant from the fibroblasts induced osteogenic differentiation of mES cells in the order PLFs > GFs > SFs. These activities of PLFs were related to their potential to produce osteogenic markers, such as ALP and runt-related transcription factor-2 (Runx2), and to secrete FGF7. Pretreatment of mES cells with the extracellular signal-regulated kinase inhibitor PD98059 [2-(2-amino-3-methyoxyphenyl)-4H-1-benzopyran-4-one] or SP600125 clearly attenuated mineralization induced by culture supernatant of PLF with attendant decreases in mRNA levels of Runx2, bone sialoprotein, osteocalcin, and osteopontin.

CONCLUSION

PLFs regulate the proliferation and osteogenic differentiation of mES cells more strongly than GFs and SFs via the secretion of FGF through a mechanism that involves mitogen-activated protein kinase-mediated signaling.

Fibroblast growth factor-7 facilitates osteogenic differentiation of embryonic stem cells through the activation of ERK/Runx2 signaling

Fibroblast growth factor-7 (FGF7) is known to regulate proliferation and differentiation of cells; however, little information is available on how FGF7 affects the differentiation of embryonic stem cells (ESCs). We examined the effects of FGF7 on proliferation and osteogenic differentiation of mouse ESCs. Exogenous FGF7 addition did not change the proliferation rate of mouse ESCs. In contrast, the addition of FGF7 facilitated the dexamethasone, ascorbic acid, and β-glycerophosphate (DAG)-induced increases in bone-like nodule formation and calcium accumulation. FGF7 also augmented mRNA expression of runt-related transcription factor-2 (Runx2), osterix, bone sialoprotein (BSP), and osteocalcin (OC) in the presence of DAG. FGF7-mediated increases in the mineralization and bone-specific gene expression were almost completely attenuated by pretreating with anti-FGF7 antibody. FGF7 treatment accelerated the DAG-induced activation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) in the cells. A pharmacological inhibitor specific to ERK, but not to JNK or p38 kinase, dramatically suppressed FGF7-mediated mineralization and accumulation of collagen and OC in the presence of DAG. This suppression was accompanied by the reduction in Runx2, osterix, BSP, and OC mRNA levels, which were increased by FGF7 in the presence of DAG. Collectively, our results suggest that FGF7 stimulates osteogenic differentiation, but not proliferation, in ESCs, by activating ERK/Runx2 signaling.

Regulation of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases by basic fibroblast growth factor and dexamethasone in periodontal ligament cells

BACKGROUND AND OBJECTIVES

In this study, we investigated the effect of basic fibroblast growth factor (bFGF) and dexamethasone (Dex) on mRNA expressions of collagen (COL) type I, III and X, matrix metalloproteinases (MMP)-1, -2, -3 and -9 and tissue inhibitors of metalloproteinases (TIMP)-1 and -2, and also on mineralization and morphology of periodontal ligament (PDL) cells.

MATERIAL AND METHODS

Periodontal ligament cells were obtained from premolar teeth extracted for orthodontic reasons. Periodontal ligament cells were cultured with Dulbecco's modified Eagle's medium containing: (1) 5% fetal bovine serum (FBS); (2) 5% FBS + ascorbic acid (AA, 50 microg/mL); (3) 5% FBS + Dex (10(-7) m) + AA; (4) 5% FBS + bFGF (10 ng/mL) + AA; or (5) 5% FBS + Dex (10(-7) m) + bFGF + AA. Cells within each group were evaluated for gene expression profile using semi-quantitative reverse transcriptase-polymerase chain reaction for COL I, III and X, MMP-1, -2, -3 and -9 and TIMP-1 and -2 on days 14 and 21 and for biomineralization by von Kossa stain in vitro on day 21. Images of PDL cells were examined using a phase contrast microscope.

RESULTS

Basic fibroblast growth factor stimulated MMP-1, MMP-3 and MMP-9 mRNA expressions and inhibited TIMP-2 mRNA expression. Treatment of cells with Dex + bFGF led to downregulation of MMP-1, MMP-3 and MMP-9 transcripts. Whilst AA alone and Dex alone induced biomineralization of PDL cells, bFGF blocked the mineralization activity of the cells. In the Dex + bFGF group, more mineral nodules were noted when compared to AA alone and Dex alone groups.

CONCLUSION

The addition of Dex to culture reversed bFGF-mediated inhibition of mineralization. Use of combined bFGF and Dex to regulate PDL cell function may be a good therapeutic option to obtain periodontal regeneration.

Relaxin's involvement in extracellular matrix homeostasis

Burgeoning evidence suggests that the hormone relaxin modulates collagen in the extracellular matrix of diverse tissues. In separate lines of study, we provide further substantiation of this hypothesis. Immunofluorescence was used to probe isolated fibroblasts derived from volar oblique ligament explant culture for vimentin, actin, RXFP1, and estrogen receptor beta. Ligaments were obtained as surgical waste from thumb reconstruction patients. Four specimens have been examined to date. Cells derived from these patients expressed vimentin and actin, consistent with fibroblast morphology. Putative fibroblasts derived from two of three female patients expressed RXFP1 receptors; the solitary male was negative. Given the small sample, however, the data are considered preliminary. Immunohistochemistry was used on frozen sections from 26 skin biopsies obtained from children undergoing genitoplasty. A subset of samples was also probed for transforming growth factor (TGF-beta1) and TGF-beta3. Appropriate controls were used. Finally, a subset of patient blood was assayed for relaxin by using an enzyme-linked immunosorbent assay-based method. The results showed RXFP1 receptor expression in the cells that populate the basement membrane in 96% of patients, regardless of gender. Most tissue expressed TGF-beta. Finally, serology suggested that relaxin was detectable in these children. Our two lines of research provide additional evidence for the diverse tissue tropism of relaxin. In particular, connective tissues as diverse as ligaments and basal lamina keratinocytes express RXFP1. These data lend support to our contention that relaxin affects ligament integrity and wound healing.

Effects of basic fibroblast growth factor on density and morphology of fibroblasts grown on root surfaces with or without conditioning with tetracycline or EDTA

A study was conducted to evaluate in vitro the effect of root surface conditioning with basic fibroblast growth factor (b-FGF) on morphology and proliferation of fibroblasts. Three experimental groups were used: non-treated, and treated with 50 microg or 125 microg b-FGF/ml. The dentin samples in each group were divided into subgroups according to the chemical treatment received before application of b-FGF: none, or conditioned with tetracycline-HCl or EDTA. After contact with b-FGF for 5 min, the samples were incubated for 24 h with 1 ml of culture medium containing 1 x 10(5) cells/ml plus 1 ml of culture medium alone. The samples were then subjected to routine preparation for SEM, and random fields were photographed. Three calibrated and blind examiners performed the assessment of morphology and density according to two index systems. Classification and regression trees indicated that the root surfaces treated with 125 microg b-FGF and previously conditioned with tetracycline-HCl or EDTA presented a morphology more suggestive of cellular adhesion and viability (P = 0.004). The density of fibroblasts on samples previously conditioned with EDTA, regardless of treatment with b-FGF, was significantly higher than in the other groups (P < 0.001). The present findings suggest that topical application of b-FGF has a positive influence on both the density and morphology of fibroblasts.

Opposite effects of bFGF and TGF-β on collagen metabolism by human periodontal ligament fibroblasts

This study evaluated the effects of bFGF and TGF-beta, individually and combined, on cell proliferation and collagen metabolism. Primary human periodontal ligament cells were stimulated with two concentrations (1 and 10 ng/ml) of each growth factor, both individually and combined. Proliferation was determined by a commercial biochemical assay. Real time RT-PCR determined gene expression of MMP-1 and -2, collagen types I and III, TIMP-1, -2 and -3. Autocrine effects on synthesis of bFGF and TGF-beta were evaluated by ELISA. Only TGF-beta, either isolated or associated with bFGF, significantly increased cell proliferation. TGF-beta had anabolic effects, increasing expression of type I and III collagen as well as of TIMPs, whereas bFGF had opposite effects. When bFGF and TGF-beta were associated, the anabolic effects prevailed. Synthesis of TGF-beta was induced only by the association of lower concentrations of the growth factors, whereas there was a dose-dependent production of bFGF. It is concluded that bFGF had a predominantly catabolic effect, and TGF-beta exerted an anabolic effect on hPDL cells.

Role of growth factors on periodontal repair

Regeneration of periodontal structures lost during periodontal diseases constitutes a complex biological process regulated among others by interactions between cells and growth factors. Growth factors are biologically active polypeptides affecting the proliferation, chemotaxis and differentiation of cells from epithelium, bone and connective tissue. They express their action by binding to specific cell-surface receptors present on various target cells including osteoblasts, cementoblasts and periodontal ligament fibroblasts. The observation that growth factors participate in all cell functions led to exogenous application during periodontal tissue repair aiming to their use as an alternative therapeutic approach to periodontal therapy. Cell types and cultures conditions, dose, carrier materials, application requirements are of critical importance in the outcome of periodontal repair. The purpose of this article is to review the literature with respect to the biological actions of PDGF, TGF, FGF, IGF and EGF on periodontal cells and tissues, which are involved in periodontal regeneration.

Time- and dose-dependent mitogenic effect of basic fibroblast growth factor combined with different bone graft materials: an in vitro study

OBJECTIVES

In periodontal regeneration, the growth factor concentrations and the delivery system used are of great importance. In an attempt to assess the mitogenic effect of basic fibroblast growth factor (bFGF) on periodontal ligament (PDL) cells combined with different bone replacement materials, two allografts of cortical (DFDBA) and cancellous (DFBA) bone and an anorganic bovine material with a synthetic peptide (ABM P-15) were used. The purpose of this study was to evaluate the in vitro mitogenic effect of different doses of bFGF alone or in combination with DFDBA, DFBA and ABM P-15 on human PDL cells in a time-dependent mode.

MATERIAL AND METHODS

PDL cell cultures were derived from the mid-root of four maxillary premolars. Cells were grown and reached confluence. On day 2 of quiescence, new medium was added along with (1) 1, 5, 10 and 25 ng/ml of bFGF alone, (2) 10 mg of DFDBA, DFBA and ABM P-15 alone and (3) their combination. The mitogenic effect was determined at 24 and 48 h of culture by using a hemocytometer chamber. The cells were counted under a phase contrast microscope.

RESULTS

The results revealed that bFGF at the highest concentrations and after 48 h exerted a significant mitogenic effect on PDL cells, and also DFDBA and DFBA supported cell proliferation. Furthermore, DFDBA and DFBA enriched with bFGF had a significant mitogenic effect after 48 h of culture. ABM P-15 with 10 and 25 ng/ml of bFGF up-regulated PDL cell proliferation after 48 h of incubation.

CONCLUSIONS

The findings of this study demonstrate the beneficial role of bFGF combined with DFDBA and DFBA as carriers in periodontal repair.

Dexamethasone and basic-fibroblast growth factor regulate markers of mineralization in cementoblasts in vitro

BACKGROUND

The aim of this study was to determine the effects of basic-fibroblast growth factor (b-FGF) and/or dexamethasone (Dex) on cementoblasts in vitro.

METHODS

Murine cementoblasts were treated as follows: 1) 5% FBS (fetal bovine serum) + ascorbic acid (AA, 50 microg/ml, control); 2) 5% FBS + Dex (10(7)M) + AA; 3) 5% FBS + b-FGF (50 ng/ml)+AA; or 4) 5% FBS + Dex (10(7) M) + b-FGF (50 ng/ml)+AA and then evaluated by Northern analysis for changes in specific genes and by von Kossa stain for changes in mineral nodule formation.

RESULTS

Mitotic activity: b-FGF stimulated DNA synthesis significantly versus negative control. Gene expression: osteocalcin (OCN): Dex or b-FGF or the combination resulted in a decrease in expression versus control. Bone sialoprotein (BSP): Dex increased expression of BSP mRNA levels, b-FGF decreased transcript for BSP at 6 and 24 hours. Long-term (8 days) Dex, b-FGF, or Dex plus b-FGF caused a decrease in BSP expression versus control; osteopontin (OPN): both Dex and b-FGF increased transcripts for OPN seen by 6 hours, with a greater increase noted with b-FGF versus Dex. No apparent additive effect of Dex with b-FGF was noted; matrix gamma-carboxyglutamic acid protein (MGP): b-FGF induced transcripts for MGP and addition of Dex increased this effect, while Dex alone had no effect on expression. Biomineralization: Dex increased cementoblast- mediated biomineralization, while b-FGF blocked this activity, and addition of Dex to b-FGF did not alter FGF associated inhibition.

CONCLUSION

Dex and FGF alone and in combination alter cementoblast behavior, but additional studies are required to determine whether these factors have beneficial effects at the clinical level.

Dentin matrix proteins and soluble factors: intrinsic regulatory signals for healing and resorption of dental and periodontal tissues?

Dentin contains numerous polypeptides and signaling molecules sequestered in a mineralized matrix. The exposure and release of these molecules occur as a consequence of injury to the pulp and periodontal ligament, which may result from luxation, orthodontic movement or infections of tooth and periodontal structures. When released at these sites, dentin constituents have the potential to act on different surrounding cells, including periodontal cells, osteoblasts, osteoclasts and inflammatory cells, and to affect the course of dental disease. Experimental studies have highlighted the interactions between dentin and cells from tooth and periodontal tissues and reveal dentin to be a cell adhesive, signaling and migratory stimulus for various mesenchymal and inflammatory cells. These results support the hypothesis that dentin molecules might function as regulatory signals for the healing and resorption of dental and periodontal tissues. Data from recent and classical investigations are summarized, many open questions are discussed, and current hypotheses concerning the mechanisms of tooth resorption and periodontal healing are outlined. Many questions regarding the importance of dentin as a source of multifunctional molecules remain unanswered and provide important directions for future studies.

Novel isolation of alkaline phosphatase-positive subpopulation from periodontal ligament fibroblasts

BACKGROUND

Periodontal ligament fibroblasts (PDLFs) are the cells essential for periodontal regeneration. PDLFs comprise a heterogeneous cell population and consist of several cell subsets that differ in their function. It is known that PDLFs produce osteoblast-related extracellular matrix proteins and show higher alkaline phosphatase (ALP) activity compared with gingival fibroblasts (GFs), implying that PDLFs have osteogenic characterisitics. The aim of the present study was to isolate the osteogenic population of PDLFs according to their expression of ALP.

METHODS

PDLFs and gingival fibroblasts were separated into two populations, ALP-positive and ALP-negative, with an immunomagnetic method using a monoclonal antibody against human bone type ALP and magnetic beads conjugated with a secondary antibody. Expression of basic fibroblast growth factor (bFGF) receptor and transforming growth factor (TGF)-beta receptor was investigated in these two populations. Osteoblast-related molecules, osteocalcin, and bone sialoprotein; ALP activity; and effect of bFGF on proliferation were also compared.

RESULTS

Effective separation was confirmed in both PDLFs and GFs by flow cytometry. The expression of FGF receptor (FGFR) and TGF-beta receptor was significantly higher in ALP-positive PDLFs than in ALP-negative PDLFs. ALP-positive PDLFs also expressed higher mRNA levels of osteocalcin and bone sialoprotein compared with ALP-negative PDLFs. The mitogenic effect of bFGF on ALP-positive PDLFs was greater than that of ALP-negative PDLFs.

CONCLUSIONS

These results indicate that osteoblastic and/or cementoblastic PDLF subsets could be isolated from the PDLF populations using an immunomagnetic method. Magnetic isolation of PDLFs may be a useful tool to obtain the cells which will potentially induce mineralization on the root surface.

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.

Effects of basic fibroblast growth factor on human gingival epithelial cells

BACKGROUND

Our previous reports found that basic fibroblast growth factor (FGF-2; bFGF) influences the proliferation and extracellular matrix production of periodontal ligament (PDL) cells. In this study, we examined FGF-2 expression in gingival epithelium and the effect of FGF-2 on proliferative responses by gingival epithelial (GE) cells.

METHODS

Human GE cells were isolated from healthy gingival epithelium, and the mRNA expression of FGF-2 and FGF receptors (FGFRs) was examined by reverse transcription-polymerase chain reaction (RT-PCR). The distribution of FGF-2 in gingival tissues was detected by immunohistological analysis using the monoclonal antibody for human recombinant FGF-2, which was newly established and designated as BF-2. Further, the proliferative responses of GE cells to FGF-2 were investigated by measuring [3H]-thymidine uptake.

RESULTS

RT-PCR revealed that GE cells express FGFR-1, FGFR-2, FGFR-3, and FGFR-4 mRNA; however, not that of FGF-2. Employing immunohistochemical staining with BF-2, FGF-2 was observed localized in the intercellular spaces of gingival epithelium, though not in the cytoplasm of epithelial cells. Interestingly, staining by BF-2 in the intercellular spaces was diminished after treatment of the tissue sections with heparitinase. Further, an in vitro analysis revealed that FGF-2 enhanced the proliferative responses of human GE cells. However, costimulation with fetal calf serum inhibited the FGF-2-induced proliferation of GE cells, whereas the same costimulation synergistically enhanced FGF-2-induced PDL cell proliferation.

CONCLUSIONS

FGF-2 is anchored in the intercellular spaces of gingival epithelium via heparansulfate and may regulate the growth and cytodifferentiation of GE cells via cell-type specific receptors.

Expression of growth-factor receptors in normal and regenerating human periodontal cells

Growth factors are biologically active mediators that bind to specific receptors on target cells and regulate genes involved in cell growth, wound healing and regeneration. The expression of these receptors is thus of fundamental importance for the response of the cells to the factors. The aim here was to examine, using immunohistochemistry and flow cytometry, the expression of growth factor receptors in normal gingiva, periodontal ligament and in cells derived from these tissues, and also in regenerated tissues following guided tissue regeneration (GTR). By immunocytochemistry platelet-derived growth factor receptor-alpha (PDGF-Ralpha) was not detected in any of the tissues, whereas the PDGF-Rbeta and transforming growth factor-beta receptor types I and II (TGF-beta RI, RII) appeared to be upregulated in regenerated tissues compared with gingival and periodontal ligament tissues. Epidermal growth factor receptor (EGF-R) was also notably elevated in the regenerated tissue and was strongly expressed in the gingival epithelium but not in the periodontal ligament. Neither were fibroblast growth factor receptor-I (FGF-RI) or insulin-like growth factor receptor (IGF-R) detected in the periodontal ligament, nor in the gingiva, but they sometimes stained weakly in the regenerated tissues. Flow cytometry (FCM) showed that all the cells derived from the normal gingiva and the periodontal ligament expressed the PDGF-Rbeta, whereas the TGF-beta RI and RII, FGF-RI and IGF-R were detected in only a proportion of the total cells. In contrast, none of the cells expressed the PDGF-Ralpha or the EGF-R. These observations show that the growth factor receptors are differentially expressed by the periodontal tissues and cells and suggest that the corresponding factors may also be differentially involved in periodontal wound healing and regeneration.

Cytokines and the role they play in the healing of ligaments and tendons

Cytokines are small proteins with the properties of locally acting hormones. They are essential for the healing of connective tissues following injury. Various cytokines are expressed endogenously during the healing responses of those ligaments and tendons which possess them, and there is evidence that the exogenous application of certain cytokines promotes healing. Because healing is a multistep process, several different cytokines may need to be applied at different times to achieve a satisfactory response. Sustained, localised delivery of the appropriate cytokines presents a technical challenge to their clinical use in the repair of ligaments and tendons. Slow release devices and gene transfer are being evaluated as strategies for obviating this limitation.