Expression of MT1-MMP during deciduous tooth resorption in odontoclasts.

Membrane type 1-matrix metalloproteinase (MT1-MMP) is a membrane-bound matrix metalloproteinase capable of mediating pericellular proteolysis of extracellular matrix components. In osteoclasts, the localization of MT1-MMP has been reported at the tips of specialized membrane protrusions (podosomes and lamellipodia) so that osteoclasts might use MT1-MMP to perform focal proteolysis and move through the extracellular matrix to the bone surface. The objectives of this study were to investigate an association of MT1-MMP in physiological root resorption of the deciduous tooth by reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blot analysis, and to identify MT1-MMP-producing cell during deciduous tooth resorption by in situ hybridization and immunohistochemistry. RT-PCR and Northern blot analysis revealed the exclusively high expression of MT1-MMP mRNA in bovine root-resorbing tissue, which lies between the root of the deciduous tooth and its permanent successor. Expression of MT1-MMP mRNA was seen in odontoclasts aligning in the surface layer of the root-resorbing tissue at sites of root resorption. Furthermore, immmunohistochemistry also confirmed the localization of MT1-MMP protein to the odontoclasts. The present identification of MT1-MMP in odontoclasts during deciduous tooth resorption might be relevant to the migration activity that these cells have to gain access to the root surface.

[Expression of cathepsin K and IL-6 mRNA in root-resorbing tissue during tooth movement in rats].

OBJECTIVE: To investigate the expression and the localization of Cathepsin K and IL-6 mRNA in root-resorbing tissue and to elucidate the molecular changes and mechanism of root resorption induced by tooth movement. METHODS: Rats were subject to experimental tooth movement to induce root resorption. In situ hybridization was performed to identify the cells in root-resorbing tissue that produced Cathepsin K or IL-6 the difference of CK mRNA or IL-6 mRNA expression between root resorption group and control group was calculated by t-test. RESULTS: Cathepsin K mRNA was highly and selectively expressed in multinuclear odontoclast and IL-6 mRNA expressed in fibroblast, osteoblast, osteocyte and cementoblast. The expression of Cathepsin K mRNA and IL-6 mRNA in root-resorbing tissue increased evidently compared with the normal periodontium. CONCLUSIONS: Odontoclast in the root-resorbing tissue expresses Cathepsin K mRNA that participates in proteolysis during root resorption. IL-6 plays a very important role in the root resorption as a multifunctional cytokine.

Localization of cathepsin K in bovine odontoclasts during deciduous tooth resorption.

Cathepsin K is a cysteine proteinase, which is abundantly and selectively expressed in osteoclasts. It is believed to play an important role in the proteolysis of bone resorption by osteoclasts. The objectives of this study were to investigate the association of cathepsin K in the physiological root resorption of deciduous teeth and to identify the cathepsin K-producing cells in deciduous root resorption. RT-PCR and Northern blot analysis of the total RNAs extracted from bovine active and resting root-resorbing tissues, which lie between the root of deciduous tooth and its permanent successor, were performed. The active root-resorbing tissue, which has a high population of odontoclasts on its surface that is attached to resorbing root surface, showed an extremely high expression of cathepsin K in comparison with the resting root-resorbing tissue. By in situ hybridization, cathepsin K mRNA was highly and selectively expressed in multinucleated odontoclasts that aligned along the surface of the tissue and apposed to the resorbing root surface of the deciduous tooth. Western blot analysis of the active root-resorbing tissue was used to characterize the anti-cathepsin K antibody. A band of 27 kDa, corresponding with the predicted size for mature cathepsin K, was demonstrated. Immunohistochemistry confirmed the specific localization of cathepsin K protein to the odontoclasts. These results demonstrate that odontoclasts in the deciduous root resorption express cathepsin K mRNA and protein that may participate in the proteolysis of root resorption of the deciduous tooth.

An alternative hypothesis from veterinary science for the pathogenesis of noncarious cervical lesions.

An alternative hypothesis to abrasion and erosion for the pathogenesis of noncarious cervical lesions was put forward in 1984; the so-called occlusal theory suggested that tensile stresses from occlusal overload could be involved in the pathogenesis of noncarious cervical lesions and that bending stresses applied to teeth could cause disruption of the surface enamel, resulting in increased susceptibility to dissolution and abrasion at the affected sites and in the development of wedge-shaped lesions. This theory has gained increased acceptance in recent years, although absolute scientific evidence has been scant. These lesions also occur in animals, in particular, the domestic cat, in which they are called feline odontoclastic resorptive lesions. A variety of theories about pathogenesis of these lesions have been put forward, but there is some evidence that occlusal overload may be a contributory factor in the development of an inflammatory response in the periodontal membrane and the presence of enzymes associated with resorption in the gingival crevice. Further investigation may help define a common etiology between the pathogenesis of feline odontoclastic resorptive lesions and noncarious cervical lesions.

Reabsorçäo dentária fisiológica: estudo dos mecanismos (Apoptose) e das moléculas desencadeadoras (Bmp-4 e Gelatinase B) em dentes decíduos de gatos / Physiologic tooth resorption: mechanism study (apoptosis) and of molecules (Bmp 4 and Gelatinase B) in cats' deciduous teeth

A reabsorçäo dentária fisiológica ou rizólise em dentes decíduos, representa um fenômeno natural e programado pelo organismo, seguido pela substituiçäo da dentiçäo temporária pela permanente. Para estudar os mecanismos e mediadores bioquímicos envolvidos na induçäo da reabsorçäo fisiológica foram utilizados caninos e incisivos decíduos de gatos, em diferentes estádios de rizólise. Os animais utilizados tinham aproximadamente dois meses de vida pós-natal. O caráter programado da reabsorçäo dentária fisiológica motivou o estudo da participaçäo da apoptose neste processo. A apoptose foi evidenciada pela técnica TUNEL modificada nos cementoblastos, fibroblastos do tecido pulpar, do ligamento periodontal e nos restos epiteliais de Malassez dos dentes decíduos. A partir desta marcaçäo buscou-se identificar os prováveis mediadores bioquímicos indutores da apoptose nestas células, utilizando-se da hibridizaçäo in situ com radiosótopos. Uma das proteínas envolvidas na induçäo da apoptose em eventos fisiológicos, a proteína morfogenética óssea 4 (BMP-4), foi detectada nos cementoblastos e células do ligamento periodontal do dente decíduo. Topograficamente observou-se uma similaridade entre a expressäo de Bmp-4 e a técnica TUNEL modificada em cortes idênticos. Uma intensa marcaçäo de Bmp-4 foi também observada nos ameloblastos do dente permanente. Para a análise da participaçäo dos clastos na rizólise, foi avaliada via hibridizaçäo in situ, a expressäo de gelatinase B, uma metaproteinase da matriz extracelular sintetizada por estas células...

Dental pulp mucopolysaccharidase: identification and role in tooth resorption.

The presence of mucopolysaccharidase activity within the pulps of resorbing deciduous teeth was investigated using histochemical techniques. The loss of toluidine blue metachromasia within glycosaminoglycan film subtrates indicated the presence of enzyme activity. This was related to physiologic resorption.

Mucopolysaccharidase activity in traumatized human deciduous teeth undergoing accelerated resorption: isolation and characterization.

Mucopolysaccharidase activity was observed in traumatized human decidous teeth. Histochemical analysis of the periodontal ligaments from these teeth revealed a loss of film substrate metachromasia during incubation, indicating enzyme activity. Routine histology of these ligaments showed the presence of an inflammatory infiltrate throughout this tissue. Biochemical analysis of the ligaments revealed a 10-fold increase of enzyme activity when incubation time was increased from 1 to 8 h. When compared to the enzyme activity measured during physiologic resorption, activity was increased. This suggests that the presence of an inflammatory infiltrate not observed in the tissues undergoing physiologic resorption may be responsible for the rapid resorption seen in traumatized deciduous teeth.

Identification and localization of a mucopolysaccharidase in human deciduous teeth.

The presence of a mucopolysaccharidase in resorbing deciduous teeth was investigated using histochemical techniques. The loss of toluidine blue metachromasia within glycosaminoglycan film substrates indicated the presence of enzyme activity, and was related to physiologic resorption. Such activity was localized to the periodontal ligament of these teeth.

Enzyme histochemical characteristics of human and kitten odontoclasts and kitten osteoclasts: a comparative study using whole cells.

Methods for the histochemical demonstration of enzymes in whole cell preparations of odontoclasts and osteoclasts are described. Enzyme histochemical characteristics of human and kitten odontoclasts from resorbing primary teeth and of osteoclasts from kitten femur metaphyses were determined and compared. The enzyme profiles, times for the appearance of detectable reaction product, intensity of the reactions and localization of the reaction products were similar in all three types of giant cell. These findings suggest that odontoclasts have enzyme properties and metabolic functions similar to those of osteoclasts. Species differences appear to be minor, although the NADP-dependent enzymes are less active in human than in kitten odontoclasts. Both odontoclasts and osteoclasts are rich in enzymes concerned with energy production and possess considerable activity of enzymes usually associated with catabolic functions. Metabolic pathways are well developed in respect of the utilization of succinic, malic, glutamic, lactic and isocitric acids, beta-hydroxybutyric acid and glucose-6-phosphate, and they also possess phosphatases, non-specific esterases and leucine naphthylamidase. The distribution of enzyme reaction products for the individual enzymes demonstrated is consistent with the presence in these cells of large numbers of mitochondria and lysosome-like organelles. Considerable phosphatase activity is demonstrable in both odontoclasts and osteoclasts at both neutral and acid pH.