Platelet association with gingival tissue inflammation

The expression levels of chemotaxis-related molecules CXC chemokine receptor 1, interleukin-8, and pro-platelet basic protein in gingival tissues

Background/purpose

Excessive host immune response is thought to be an important cause of periodontal tissue damage during periodontitis. The potent chemotaxis produced by locally released chemokines is the key signal to trigger this response. Here, we aimed to investigate the expression of CXC chemokine receptor 1 (CXCR1), and chemokines interleukin-8 (IL-8) and pro-platelet basic protein (PPBP) in human inflammatory gingival tissues compared with healthy tissues.

Materials and methods

A total of 54 human gingival tissues, 27 healthy and 27 inflammatory samples, were collected. Fifteen specimens of each group were employed for quantitative reverse transcription polymerase chain reaction to determine the mRNA levels of CXCR1, IL-8, and PPBP. Six samples of each group were used for Western blotting to investigate the protein expression of CXCR1 and for enzyme-linked immunosorbent assay to evaluate the protein levels of IL-8 and PPBP, respectively.

Results

The mRNA levels of chemokine receptor CXCR1, chemokine IL-8, and PPBP in inflammatory gingival tissues were significantly higher than those in healthy controls (P < 0.05). The protein levels of CXCR1, IL-8, and PPBP in inflammatory gingival tissues were also significantly higher than those in healthy gingival tissues (P < 0.05).

Conclusion

When compared to healthy gingival tissues, the expression of CXCR1, IL-8, and PPBP in inflammatory gingival tissues is higher.

Platelets increase while serum reduces the differentiation and activity of osteoclasts in vitro

Platelets modulate formation of osteoclasts and osteoblasts, but research with different preparations of platelets remains inconclusive. Here, we assessed whether serum components modulate the effect of platelet preparations. In murine bone marrow cultures, osteoclastogenesis was investigated in the presence of platelet-released supernatant (PRS), serum containing PRS (SC-PRS), and serum. Osteoclastogenesis was quantified by the numbers of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells, TRAP activity and resorption assays. Also human osteoclastogenesis assays were performed. Viability and proliferation were tested by MTT and (3) [H]thymidine incorporation assays, respectively. Osteoblastogenesis was assessed by histochemical staining for alkaline phosphatase-of murine bone marrow cultures and human MG63 cells. We found PRS to increase the number of TRAP(+) multinucleated cells in the early phase and TRAP activity in the later phase of osteoclastogenesis. SC-PRS and serum decreased the number and activity of TRAP(+) multinucleated cells. Both serum containing preparations reduced viability and proliferation of hematopoietic progenitors. PRS decreased the numbers of alkaline phosphatase-positive colonies while SC-PRS and serum increased osteoblastmarkers in MG63. Proliferation of MG63 was stimulated by all preparations. These results show that activated platelets support osteoclastogenesis, while platelet preparations that contain serum components decrease osteoclastogenesis and increase osteoblastogenesis in vitro, suggesting that serum components modulate the effects of platelets on osteoclastogenesis and osteoblastogenesis.

Cell biology of osteoimmunology

Osteoimmunology is defined as the research area focusing on the crosstalk between the immune system and the muskoskeletal system. After nearly a decade of research, we are now beginning to understand the basic principles of this crosstalk. It seems that almost all immune cells are capable of communicating with osteoblasts, osteoclasts, and their respective progenitors - and vice versa. Diseases that fall into the category of osteoimmunology including osteoporosis, rheumatoid arthritis, and periodontal disease are of particular significance considering their implications in quality of life, their increased incidence in the population, and socioeconomic issues. To better understand the underlying pathogenesis, the main pathways of the crosstalk between the immune system and the muskoskeletal system need to be uncovered. Our current understanding has already provided the scientific basis for the development of targeted therapies. However, the challenge of future studies is to further decipher this crosstalk at cellular and molecular levels.

Short-term induction of thrombocytopenia delays periodontal healing in rats with periodontal disease: participation of endostatin and vascular endothelial growth factor

BACKGROUND AND OBJECTIVE

Platelets contain factors, including VEGF and endostatin, that can modulate the healing process. We evaluated the effects of severe thrombocytopenia on periodontal healing in rats and determined the contribution of VEGF and endostatin to the healing process.

MATERIAL AND METHODS

Rats were distributed into three test groups and two control groups. Cotton ligatures were placed at the gingival margin level of the lower first molar in the test groups. Sham-operated rats and rats in one of the periodontitis groups were killed 15 days later. Rats in the remaining two periodontitis groups had the ligatures removed in order to study the spontaneous recovery from the periodontal disease 15 days later, and these rats were treated with rabbit antiplatelet serum, in order to induce thrombocytopenia, or normal rabbit serum. An additional group without ligatures received antiplatet serum in the same period.

RESULTS

After ligature removal, rats treated with normal rabbit serum showed reduced myeloperoxidase activity, decreased alveolar bone loss and increased numbers of blood vessels. Thrombocytopenia caused a delay in alveolar bone regeneration, a decrease in the number of vessels and a modest decrease in myeloperoxidase activity. In the rats with periodontitis, serum endostatin concentrations were slightly decreased and serum VEGF remained unchanged compared with sham-operated animals. After ligature removal, a significant VEGF increase and endostatin decrease were observed in the rats treated with normal rabbit serum. Thrombocytopenia led to a dramatic fall in both VEGF and endostatin concentrations.

CONCLUSION

Thrombocytopenia leads to a delay of periodontal healing in the situation of experimental periodontitis, which might be mediated in part by a decrease in the serum concentration of VEGF and endostatin derived from the platelets. However, other factors derived from the platelets may also have contributed to a delay of periodontal healing in the rats with thrombocytopenia.

Activated platelets retain their potential to induce osteoclast-like cell formation in murine bone marrow cultures

Supernatants immediately obtained after platelet activation can induce osteoclast-like cell formation in murine bone marrow cultures. Here we report that activated platelets retain their potential to induce osteoclast-like cell formation over a 3-day period with repeated washing, when co-cultured with murine bone marrow cells. Supernatants obtained from washed platelets 3 days following their activation with thrombin, caused the differentiation of haematopoietic progenitors into osteoclast-like cells. The platelet-derived soluble factor(s) responsible for the induction of osteoclastogenesis can be retained in an ultrafilter with a nominal molecular weight limit of 10 kDa, and loose their activity when incubated at 99 degrees C. Indomethacin, which inhibits cyclooxygenase activity, and osteoprotegerin, a decoy receptor for receptor activator of nuclear factor-kappaB ligand (RANKL), suppressed the formation of osteoclast-like cells in this model. The in vitro findings presented here suggest that activated platelets can induce osteoclast-like cell formation via a prostaglandin and RANKL-dependent mechanism over a time period corresponding to the existence of a blood clot.

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.

Levels of TGFbeta1 in gingival crevicular fluid during a 21-day experimental model of gingivitis

OBJECTIVE

TGFbeta1 is a multifunctional growth factor with both pro- and anti-inflammatory properties. This study aimed to determine levels of TGFbeta1 in gingival crevicular fluid (GCF), serum and plasma in the early stages of gingival inflammation.

DESIGN

A 21-day experimental model of gingivitis employing a split mouth design with a soft vinyl splint used to cover test teeth during brushing.

SUBJECTS

Ten healthy volunteers (mean age 21 years; five males and five females).

METHODS

GCF and blood (with and without EDTA) was collected on days 0, 7, 14 and 21. GCF volumes were measured on a precalibrated Periotron 8000TM. Clinical indices of gingival inflammation and plaque levels were obtained after GCF sampling. Normal brushing resumed after GCF collection on day 21 and final samples were collected on day 35. TGFbeta1 and alkaline phosphatase (ALP) levels were determined using enhanced chemiluminescent methods.

RESULTS

Clinical indices and GCF volumes increased at test sites during the 21-day test period. Concentrations of TGFbeta1 and ALP in GCF (test and control), serum and plasma did not change throughout the study (P > 0.3). However, total amounts of TGFbeta1 (pg sample-1) and ALP (mu IU sample-1) in GCF increased at test sites and were significantly higher than baseline values at days 7, 14 and 21 (P < 0.04). Control sites showed no variation in TGFbeta1 or ALP levels throughout the study period (P > 0.35). All parameters at test sites returned to control levels at day 35 (P > 0.3).

CONCLUSION

The data indicate that GCF TGFbeta1 levels increase early in plaque-induced inflammation. Whether the biological consequence of this site-specific increase is pro- or anti-inflammatory in nature remains to be elucidated.

Unprovoked periodontal hemorrhage, life-threatening anemia and idiopathic thrombocytopenia purpura: an unusual case report

Spontaneous gingival bleeding can occasionally be the only sign of systemic bleeding problems. The diagnosis and management of such conditions may challenge the skills of both the hematologist and the oral physician. We present this patient because of several confusing phenomena that were encountered: unprovoked periodontal hemorrhage, which endangered the life of an otherwise asymptomatic young adult male; (especially unusual was a platelet count above 150,000 cells per microliter of blood), and presentation of idiopathic thrombocytopenia purpura through spontaneous periodontal hemorrhage alone. This case history also highlights the fact that medical intervention to correct the underlying aberration of hemostasis is necessary for local dental measures to successfully stop bleeding. In contrast with the definition of thrombocytopenia, the "within normal" count of platelets should not exclude the possibility of idiopathic thrombocytopenia purpura; a fact that, if ignored, can make the diagnosis and management of bleeding troublesome.