The expression of plasminogen activator system in a rat model of periodontal wound healing

Differential uPA Expression by TGF-β1 in Gingival Fibroblasts

Transforming Growth Factor-β1 (TGF-β1) plays a key role in connective tissue remodeling and inflammation. Under pathological conditions, like periodontal disease, fibroblasts may display an altered response to this growth factor. To investigate this question, we have studied whether TGF-β1 may differentially regulate the expression of urokinase at the protein level in primary cultures of fibroblasts derived from healthy gingiva, granulation tissue from gingival wounds, and chronic periodontal disease. We observed that TGF-β1 may repress urokinase expression in healthy gingival fibroblasts and promote its production in granulation-tissue fibroblasts. A significant correlation was found between expression of the myofibroblast marker α-smooth-muscle actin and stimulation of urokinase production by TGF-β1. Immunostaining of gingival wounds showed that myofibroblasts were involved in urokinase production. TGF-β1-stimulated urokinase expression was blocked after inhibition of the c-jun-NH2 terminal kinase signaling pathway. We propose that stimulation of urokinase production by TGF-β1 is involved in the responses of activated fibroblasts to tissue injury.

Establishment of Epithelial Attachment on Titanium Surface Coated with Platelet Activating Peptide

The aim of this study was to produce epithelial attachment on a typical implant abutment surface of smooth titanium. A challenging complication that hinders the success of dental implants is peri-implantitis. A common cause of peri-implantitis may results from the lack of epithelial sealing at the peri-implant collar. Histologically, epithelial sealing is recognized as the attachment of the basement membrane (BM). BM-attachment is promoted by activated platelet aggregates at surgical wound sites. On the other hand, platelets did not aggregate on smooth titanium, the surface typical of the implant abutment. We then hypothesized that epithelial BM-attachment was produced when titanium surface was modified to allow platelet aggregation. Titanium surfaces were coated with a protease activated receptor 4-activating peptide (PAR4-AP). PAR4-AP coating yielded rapid aggregation of platelets on the titanium surface. Platelet aggregates released robust amount of epithelial chemoattractants (IGF-I, TGF-β) and growth factors (EGF, VEGF) on the titanium surface. Human gingival epithelial cells, when they were co-cultured on the platelet aggregates, successfully attached to the PAR4-AP coated titanium surface with spread laminin5 positive BM and consecutive staining of the epithelial tight junction component ZO1, indicating the formation of complete epithelial sheet. These in-vitro results indicate the establishment of epithelial BM-attachment to the titanium surface.

Relevance of the plasminogen system in physiology, pathology, and regeneration of oral tissues - From the perspective of dental specialties

Plasmin is a proteolytic enzyme that is crucial in fibrinolysis. In oral tissues, the plasminogen system plays an essential role in physiological and pathological processes, which in addition to fibrinolysis include degradation of extracellular matrix, inflammation, immune response, angiogenesis, tissue remodeling, cell migration, and wound healing. Oral tissues reveal a change in the plasminogen system during pathological processes such as periodontitis, peri-implantitis, or pulpitis, as well as in response to mechanical load. The plasminogen system is also a key element in tissue regeneration. The number of studies investigating the plasminogen system in dentistry have grown continuously in recent years, highlighting its increasing relevance in dental medicine. In this review, we present the diverse functions of the plasminogen system in physiology and its importance for dental specialists in pathology and regeneration. We thus provide an overview of the current knowledge on the role of the plasminogen system in the different fields of dentistry, including endodontics, orthodontics, periodontics, and oral surgery.

Formation of blood clot on biomaterial implants influences bone healing

The first step in bone healing is forming a blood clot at injured bones. During bone implantation, biomaterials unavoidably come into direct contact with blood, leading to a blood clot formation on its surface prior to bone regeneration. Despite both situations being similar in forming a blood clot at the defect site, most research in bone tissue engineering virtually ignores the important role of a blood clot in supporting healing. Dental implantology has long demonstrated that the fibrin structure and cellular content of a peri-implant clot can greatly affect osteoconduction and de novo bone formation on implant surfaces. This article reviews the formation of a blood clot during bone healing in relation to the use of platelet-rich plasma (PRP) gels. It is implicated that PRP gels are dramatically altered from a normal clot in healing, resulting in conflicting effect on bone regeneration. These results indicate that the effect of clots on bone regeneration depends on how the clots are formed. Factors that influence blood clot structure and properties in relation to bone healing are also highlighted. Such knowledge is essential for developing strategies to optimally control blood clot formation, which ultimately alter the healing microenvironment of bone. Of particular interest are modification of surface chemistry of biomaterials, which displays functional groups at varied composition for the purpose of tailoring blood coagulation activation, resultant clot fibrin architecture, rigidity, susceptibility to lysis, and growth factor release. This opens new scope of in situ blood clot modification as a promising approach in accelerating and controlling bone regeneration.

The plasminogen activation system in periodontal tissue (Review)

The plasminogen activation system (PAS) plays an essential role in tissue proteolysis in physiological and pathological processes. Periodontitis is a chronic infection associated with increased proteolysis driven by plasminogen activation. In this comprehensive review, we summarise the effects of PAS in wound healing, tissue remodelling, inflammation, bacterial infection, and in the initiation and progression of periodontal disease. Specifically, we discuss the role of plasminogen activators (PAs), including urokinase PA (uPA), tissue-type PA (tPA), PA inhibitor type 1 (PAI-1) and 2 (PAI-2) and activated plasminogen in periodontal tissue, where their concentrations can reach much higher values than those found in other parts of the body. We also discuss whether PA deficiencies can have effects on periodontal tissue. We conclude that in periodontal disease, PAS is unbalanced and equalizing its function can improve the clinical periodontal tissue condition.

Prospective potency of TGF-β1 on maintenance and regeneration of periodontal tissue

Periodontal ligament (PDL) tissue, central in the periodontium, plays crucial roles in sustaining tooth in the bone socket. Irreparable damages of this tissue provoke tooth loss, causing a decreased quality of life. The question arises as to how PDL tissue is maintained or how the lost PDL tissue can be regenerated. Stem cells included in PDL tissue (PDLSCs) are widely accepted to have the potential to maintain or regenerate the periodontium, but PDLSCs are very few in number. In recent studies, undifferentiated clonal human PDL cell lines were developed to elucidate the applicable potentials of PDLSCs for the periodontal regenerative medicine based on cell-based tissue engineering. In addition, it has been suggested that transforming growth factor-beta 1 is an eligible factor for the maintenance and regeneration of PDL tissue.

Effects of platelet-derived growth factor isoforms on plasminogen activation by periodontal ligament and gingival fibroblasts

BACKGROUND AND OBJECTIVE

Platelet-derived growth factor isoforms and components of the plasminogen activator system are expressed at higher levels during periodontal regeneration. Recombinant platelet-derived growth factor-BB is approved for the treatment of periodontal defects. In the present study we investigated the effect of platelet-derived growth factor isoforms on the plasminogen activator system in periodontal fibroblasts.

MATERIAL AND METHODS

Human periodontal ligament fibroblasts and gingival fibroblasts were exposed to platelet-derived growth factor isoforms. Changes in urokinase-type plasminogen activator, tissue-type plasminogen activator, plasminogen activator inhibitor-1 and plasminogen activator inhibitor-2 transcript levels by platelet-derived growth factor-BB were monitored with a quantitative reverse transcription-polymerase chain reaction. Urokinase-type plasminogen activator and plasminogen activator inhibitor-1 protein levels were assessed by immunoassays. The effects of platelet-derived growth factor-BB on mitogen-activated protein kinase and phosphoinositol-3 kinase/Akt signaling were investigated by western blot and inhibitor studies. Casein zymography and kinetic assays revealed the size and activity, respectively, of the plasminogen activators.

RESULTS

We found that incubation of periodontal ligament fibroblasts and gingival fibroblasts with platelet-derived growth factor-BB resulted in enhanced levels of urokinase-type plasminogen activator and plasminogen activator inhibitor-1 transcripts, but not of tissue-type plasminogen activator and plasminogen activator inhibitor-2. Platelet-derived growth factor-BB also increased urokinase-type plasminogen activator and plasminogen activator inhibitor-1 release into the culture medium. Phosphorylation of extracellular signal-regulated kinase, p38, c-Jun N-terminal kinase and Akt was observed in fibroblasts of both origin. Inhibition of phosphoinositol-3 kinase signaling abrogated the platelet-derived growth factor-BB effect on plasminogen activator inhibitor-1 production. Casein zymography revealed enzymatic activity of the urokinase-type plasminogen activator in cell-conditioned media and lysates of periodontal ligament fibroblasts and gingival fibroblasts. Exposure of gingival fibroblasts, but not of periodontal ligament fibroblasts, to platelet-derived growth factor isoforms moderately increased total plasminogen activation in the medium.

CONCLUSION

These findings suggest that periodontal ligament fibroblasts attempt to maintain an equilibrium of the plasminogen activator system in the presence of platelet-derived growth factor isoforms.

Plasminogen activation by fibroblasts from periodontal ligament and gingiva is not directly affected by chemokines in vitro

OBJECTIVE

Chronic inflammation in periodontal disease is associated with increased plasminogen activation and elevated levels of chemokines. It is unknown whether chemokines can regulate the activation of plasminogen via modulation of plasminogen activators (PA) and the corresponding plasminogen activator inhibitors (PAI) in periodontal tissue.

DESIGN

To establish a link between chemokines and activation of plasminogen, human periodontal ligament fibroblasts (PDL) and gingival fibroblasts (GF) were incubated with IL-8, monocyte chemoattractant protein-1, macrophage inflammatory protein-1alpha, and platelet factor-4, either alone or in the presence of the inflammatory mediators TGF-beta and IL-1. The potential of the cell lysates to activate plasminogen was based on kinetic studies with the substrate casein. Casein zymography was performed to determine the molecular sizes of the PA. Total PAI-1 in the cell-conditioned medium was quantified by immunoassay.

RESULTS

We report that the chemokines did not affect activation of plasminogen by PDL and GF. Even in the presence of TGF-beta which suppressed, and IL-1 which stimulated plasminogen activation, the chemokines had no direct effect. Inhibition of PA and plasmin, but not of matrix metalloproteinases and cysteine proteinases prevented caseinolysis. The plasminogen activation capacity of the cell lysates was represented by a single band with features of uPA. The immunoassay showed that the release of PAI-1 in PDL and GF remained unaffected by the chemokines, also when stimulated with TGF-beta.

CONCLUSIONS

These results suggest that plasminogen activation by PDL and GF is not directly affected by the chemokines even in the presence of the inflammatory mediators TGF-beta and IL-1.

Gene expression profiling of cells involved in periodontal regeneration

Understanding the molecular mechanisms involved in periodontal regeneration is important for the development of more predictable clinical techniques. This study aimed to identify these mechanisms by comparing the gene expression profiles of cells derived from regenerating defects with patient-matched periodontal ligament cells. Gene profiling was carried out via Affymetrix U133A arrays containing probes for 22,000 genes. Robust differences in gene expression were obtained by identifying genes that consistently changed by a minimum of 2-fold. Analysis of molecular function as designated by gene ontology (GO) identified differentially regulated mechanisms including protein metabolism, tyrosine kinase activity, and skeletal development. The differentially expressed genes could be broadly divided into the categories of protein biosynthesis and turnover, structural constituents of the cytoskeleton and extracellular matrix, and signal transduction. The differential expression of 4 genes (EGR-1, elastin, osteoprotegerin, and IGFBP3) was confirmed via real-time polymerase chain reaction (PCR). Further, the expression of another 2 differentially expressed transcripts, decorin and biglycan, was immunohistochemically confirmed in a periodontal wound healing model and the protein expression was consistent with the pattern of gene expression. This study gives insight into the molecular processes involved in periodontal regeneration and identifies cell markers that are characteristic of regenerating periodontal tissues.

Associations between peri-implant crevicular fluid volume, concentrations of crevicular inflammatory mediators, and composite IL-1A ?889 and IL-1B +3954 genotype: A cross-sectional study on implant recall patients with and without clinical signs of peri-implantitis

OBJECTIVES

To assess possible relationships between peri-implant crevicular fluid (PICF) volumes, biochemical markers of the peri-implant immune response, and periodontitis-associated genotype.

MATERIAL AND METHODS

PICF samples from 29 implant maintenance patients, 24 wearing overdentures, five having single crowns and bridgework (11 patients with peri-implantitis and 18 individuals with healthy peri-implant conditions), were analyzed for per site and per crevicular-fluid-volume concentrations of interleukin-1beta, plasminogen activator inhibitor type 2, and prostaglandin E2 by ELISA. Associations between the three substance concentrations and to crevicular fluid flow rate were analyzed by linear regression analysis. The possible differentiating influence of the composite interleukin-1A and -1B genotype on the patients' peri-implant health and biochemical inflammatory status was checked formally with t-test statistics and the Wilcoxon' test. One implant per patient was chosen for analysis.

RESULTS

In patients with healthy peri-implant conditions, genotype-positive individuals showed elevated crevicular fluid flow rates and at the same time reduced mediator concentrations. In patients with an implant affected from peri-implantitis, no statistically significant influence of the periodontitis-associated genotype around the fixture can be stated. There was no statistical difference between per site and per crevicular-fluid-volume concentration analyses. All three mediator concentrations were positively related to each other, while there was a strong negative correlation between crevicular fluid volume and plasminogen activator inhibitor 2 or prostaglandin E2.

CONCLUSIONS

The Interleukin-1 polymorphism investigated exerted only little influence on the peri-implant crevicular immune response, and this influence appeared to be of limited impact in sites with established peri-implantitis lesions.

Plasminogen activators and inhibitor type-1 in alveolar osteitis

Alveolar osteitis (AO) is characterized by excess fibrinolysis, leading to early dissociation of the clot that normally follows tooth extraction. Nonetheless, scarce information is available on the fibrinolytic system in AO. In this study, we report on the differential composition of postextraction wound healing tissue and of peri-alveolar gingival epithelium from normal healing and AO patients in terms of plasminogen activators, plasminogen activator inhibitor-type 1, and urokinase-type plasminogen activator receptor. Plasminogen activators were studied by overlay zymography, western blotting, and enzyme-linked immunosorbent assay (ELISA). Plasminogen activator inhibitor-type 1 and urokinase receptor were measured by ELISA. In AO, the fibrinolytic activity of wound healing tissue was accounted for by an increase ( approximately 85%) of urokinase-type plasminogen activator, whereas tissue-type plasminogen activator was unchanged. Plasminogen activator inhibitor-type 1 showed a 6.7-fold increase in AO. These results point to key roles of urokinase in AO hyper-fibrinolysis and of plasminogen activator inhibitor type-1 in slowing down the healing response. Peri-alveolar gingival epithelium in AO showed an overall decrease of all the components of the fibrinolytic system, including the urokinase receptor, which indicates a decrease of the migration properties of epithelial cells.

Effects of Antiadhesion preparation on free fibrinogen and fibrin degrading products in abdominal exudates of rabbits postoperatively

AIM: To observe effects of ACOL on fibrinogen (FIB), fibrin degrading products (FDP) and changes of FIB and FDP concentration in rabbits with intro-abdominal exudates during 7 d after major abdominal surgery.

METHODS: Sixty New Zealand rabbits were randomly divided into 4 groups: ACOL group, the control group, DCT group and the normal group. After being modeled, except the normal group, the other 3 groups were treated with different ways for a week; the intro-abdominal exudates of rabbits in the 4 groups were drawn for FIB and FDP measurement once daily during 7 d after major abdominal surgery.

RESULTS: FIB and FDP in the intro-abdominal exudates altered in a regular way and ACOL could change the concentration of FIB and FDP in the intra-abdominal exudates after major abdominal surgery.

CONCLUSION: ACOL can prevent intestinal adhesion by reducing the concentration of FIB and raising that of FDP in the intro-abdominal exudates after major abdominal surgery.

Heterogeneity of gene expression in human atheroma unmasked using cDNA representational difference analysis

The rupture of an atherosclerotic plaque can have profound consequences, such as myocardial or cerebrovascular infarction. The complex interactions of vascular smooth muscle cells (VSMCs) with inflammatory and immune cells are thought to contribute to both plaque genesis and stability. Key to our understanding of these processes is the identification of genes expressed in human atheromatous lesions. We have employed cDNA representational difference analysis (RDA) to investigate the differences in gene expression between normal and atherosclerotic human vessels. Thirty-one cDNA clones representing sequences expressed in atheroma were isolated, many of which encoded components of inflammatory and immune pathways. The reciprocal experiment, to identify genes expressed in the healthy vasculature, identified two genes associated with the contractile functions of VSMCs. Semiquantitative RT-PCR analysis of expression of these genes in forty samples, derived from healthy and atheromatous vessels, demonstrated marked heterogeneity of gene expression between lesions, although several of the genes were preferentially expressed in atherosclerotic lesions. In situ hybridization identified subsets of macrophages at sites of neovascularization within the lesion and intimal VSMCs as expressing the disease-associated genes. In conclusion, cDNA RDA is a useful, fast, and efficient technique for studying differential gene expression particularly when clinical material is limiting.