Effect of alendronate on bone-specific alkaline phosphatase on periodontal bone loss in rats.

OBJECTIVE: The study aims to evaluate the effect of alendronate (ALD) on bone-specific alkaline phosphatase (BALP) serum levels on periodontal bone loss in Wistar rats. DESIGN: Periodontitis was induced by ligature around the upper second molar in 36 male Wistar rats (± 200 g). Groups of six animals received 0.9% saline (SAL) or ALD (0.01; 0.05; 0.25 mgkg(-1), s.c.), over 11 days; then they were sacrificed and their maxillae were removed to be defleshed and stained for macroscopic or histopathological analysis. Blood samples were collected for BALP, transaminases and total alkaline phosphatase (TALP) serum dosage, and haematologic study. Rats were weighed daily. RESULTS: Periodontitis induction caused reduction of BALP, intense alveolar bone loss (ABL), cementum and periodontal ligament destructions and intense leucocyte infiltration seen microscopically. Systemically, periodontitis induced leucocytosis, weight loss and TALP reduction. ALD (0.25 mgkg(-1)) prevented BALP reduction (19.17 ± 1.36 Ul(-1)) when compared to SAL (13.6 ± 1.5), as well as prevented ABL, by 57.2%, when compared to SAL (4.80+0.18 mm(2)), which was corroborated by histological findings (ALD 0.25 mgkg(-1)=1.5 (1-2) and SAL=3 (2-3)) (p<0.05). ALD did not alter transaminases but reduced TALP levels (p<0.05). ALD 0.25 mgkg(-1) reduced 6th-h neutrophilia (2.50 ± 0.22cell × 10(3)mm(-3)) and 7th- (12.29 ± 0.66) and 11th-day lymphomonocytosis (15.74 ± 0.52) when compared to SAL (5.20 ± 0.28; 18.24 ± 1.05; and 23.21 ± 1.48, respectively). ALD did not alter the weight loss. CONCLUSION: ALD prevented BALP reduction and ABL and reduced inflammatory infiltrate, without causing systemic alterations.

Overexpression of matrix metalloproteinase (MMP)-1 and -9 in central giant cell lesions of the jaws: implications for clinical behavior.

OBJECTIVE: The aim of this study was to investigate the relationship between the immunohistochemical expression of MMP-1 and MMP-9 with the clinical behavior of central giant cell lesions (CGCLs) of the jaws. STUDY DESIGN: Paraffin-embedded tissue from 30 aggressive and 12 nonaggressive CGCLs was assessed for the expression of MMP-1 and MMP-9 using immunohistochemistry. RESULTS: Although cellular immunolocalization patterns of MMP-1 and MMP-9 were similar, mean values of expression estimation/SID scores of each protease were significantly higher in aggressive CGCLs in comparison with nonaggressive lesions. Moreover, linear regression analysis showed that there was a reasonably good correlation not only between the expression estimation but also among SID scores of the 2 proteolytic enzymes. CONCLUSION: The findings of this study suggest a role for MMP-1 and MMP-9 in the resorptive activity of different cellular groups in CGCLs and indicate that differences in immunoreactivity of these 2 proteolytic enzymes may underlie the distinct clinical behavior.

MAP kinase phosphatase-1 protects against inflammatory bone loss.

The mitogen-activated protein (MAP) kinase phosphatase (MKP) family plays an important function in regulating the pro-inflammatory cytokines by deactivating MAP kinases. MKP-1 is essential for the dephosphorylation of p38 MAP kinase that regulates expression of IL-6, TNF-alpha, and IL-1 beta. We hypothesized that MKP-1 regulates inflammatory bone loss in experimental periodontitis. Wild-type and Mkp-1(-/-) mice received A. actinomycetemcomitans LPS injection in the palatal region or PBS control 3 times/wk for 30 days. Mice were killed, and maxillae were assessed by microcomputed tomography, histological analysis, and TRAP staining for measurement of bone loss, extent of inflammation, and degree of osteoclastogenesis. Results indicated that, in LPS-injected Mkp-1(-/-) mice, significantly greater bone loss occurred with more inflammatory infiltrate and a significant increase in osteoclastogenesis compared with Mkp-1(-/-) control sites or either wild-type group. Analysis of these data indicates that MKP-1 plays a key role in the regulation of inflammatory bone loss.

Vascular endothelial growth factor and e-nitric oxide synthase-mediated regenerative response occurring upon autologous and heterologous bone grafts.

Bone regeneration procedures allow oral rehabilitation with dental implants also in edentulous ridges with severe bone atrophy. The integration of grafted materials with the host tissue can initiate regenerative, inflammatory and apoptotic response. Since molecular mechanisms exist at the basis of such response, the aim of this work is to investigate, by immunohistochemical analyses, the expression of proteins involved in the graft integration process, in parallel to clinical and histological modifications, occurring on sites treated with extraoral autologous bone graft deriving from the parietal region of the calvaria (eAB), intraoral autologous bone graft deriving from mandibular ramus (iAB) and heterologous bone graft from swine (hB) in human patients. In our study, the immunohistochemical expression of BSP, VEGF, eNOS in eAB samples was significantly higher (p < 0.05) compared to values recorded in iAB and hB samples. The inflammatory response, investigated by iNOS expression, was found lower in all autologous samples (eAB and iAB) compared to hB, at statistically significant values. Moreover, the expression of the pro-apoptotic molecule, Bax, resulted significantly lower (p < 0.05) in eAB than in iAB and hB samples. These values, together with the low number of apoptotic cells detected in autologous samples, suggest a good regenerative response when extraoral autologous bone graft is used in comparison to the response from the other grafts, and also suggest the use of calvaria graft as a predictable therapeutic procedure for repairing severe bone defects in oral and maxillofacial surgery, not only by clinical and biomechanical criteria, but also from a biomolecular aspect.

Hyper-reactive PMNs in FcgammaRIIa 131 H/H genotype periodontitis patients.

BACKGROUND: Receptors for the Fc part of IgG (FcgammaRIIa) on polymorphonuclear leukocytes (PMN) mediate phagocytosis and cell activation. Previous results show that one of the genetic variants of the FcgammaRIIa, the 131 H/H, is associated with more periodontal breakdown than the R/R. This may be due to hyper-reactivity of the H/H-PMNs upon interaction with bacteria. AIM: To study whether the FcgammaRIIa genotype modifies the PMN reactivity in periodontitis patients. MATERIAL AND METHODS: A cohort of 98 periodontitis patients was genotyped. From these, 10 H/H and 10 R/R consented to participate. PMNs were incubated with immune serum-opsonized Actinobacillus actinomycetemcomitans (A.a.). Phagocytosis, degranulation (CD63 and CD66b expression), respiratory burst and elastase release were assessed. RESULTS: Patients of the H/H genotype showed more bone loss than those with the H/R or R/R genotype (p=0.038). H/H-PMNs phagocytosed more opsonized A.a. than did R/R-PMNs (p=0.019). The H/H-PMNs also expressed more CD63 and CD66b than did the R/R-PMNs (p=0.004 and 0.002, respectively) and released more elastase (p=0.001). CONCLUSIONS: The genotyping results confirm previous reports that more periodontal destruction occurs in the H/H genotype than in the H/R or R/R genotype. The functional studies indicate a hyper-reactivity of the H/H-PMN in response to bacteria, which may be one of several pathways leading to more periodontal breakdown.

Inducible nitric oxide synthase mediates bone development and P. gingivalis-induced alveolar bone loss.

The role of inducible nitric oxide synthase (iNOS) in bone development and bacterially induced periodontal bone loss was examined using mice with targeted mutation of the iNOS gene. Femurs of iNOS KO mice showed 30% and 9% higher bone mineral density compared to wild type (WT) at 4 and 9 weeks of age, respectively. Micro-computed tomography revealed that cortical thickness and cortical bone density is increased in the absence of iNOS, while trabecular bone thickness and bone density remains unchanged. Histochemical analysis using TRAP staining showed that osteoclast numbers are lower by 25% in iNOS KO femurs compared to WT femurs. When bone marrow cells were stimulated with M-CSF and RANKL in vitro, iNOS KO cultures developed 51% fewer TRAP-positive multinuclear cells compared to WT cultures. When similar cultures were grown on dentine discs, resorption pit area was decreased by 54% in iNOS KO cultures. Gene expression studies showed that iNOS expression is induced by M-CSF and RANKL in WT bone marrow cultures, while no iNOS transcript was detected in iNOS KO. No compensatory change was detected in the expression of neuronal or endothelial NOS isoforms. There was no difference in RANK and osteoprotegerin expression between iNOS KO and WT bone marrow cultures after M-CSF and RANKL-treatment, while Traf6 expression was significantly lower in the absence of iNOS. In the alveolar bone of the maxilla, the distance between the cementoenamel junction and the alveolar bone crest was larger in iNOS KO compared to WT mice from 6 to 14 weeks of age, indicating a developmental effect of iNOS in oral tissues. Oral administration of the periodontal pathogen Porphyromonas gingivalis caused alveolar bone loss in the maxilla of WT mice, but failed to do so in iNOS KO mice. Expression of the osteoclast marker cathepsin K was 25% lower in iNOS KO alveolar bone. These data indicate that iNOS promotes bone resorption during bone development as well as after bacterial infection, and that iNOS is an important signal for normal osteoclast differentiation.