Orientador: Célia Regina Nogueira / Resumo: O tecido ósseo é extremamente complexo e regulado por fatores sistêmicos e locais, apresentando considerável atividade metabólica que envolve a remoção do osso mineralizado pelos osteoclastos, seguida pela formação da matriz óssea pelos osteoblastos. A associação de triiodotironina (T3) e estrógeno (E2) pode levar a uma resposta complexa à atividade do tecido ósseo sendo que o T3 possui efeito tanto sobre a reabsorção como na formação óssea e o E2, em baixo nível, pode levar a osteoporose e no estado normal garante a supressão de citocinas, a partir do sistema RANKL, OPG e c-Fos, que participam ativamente no remodelamento ósseo. Dessa forma, muitos estudos têm sido realizados com o objetivo de verificar a ação hormonal sobre o metabolismo ósseo. Entre essas pesquisas, têm sido isoladas células-tronco mesenquimais (CTMs) a partir do tecido adiposo humano e diferenciadas em osteoblastos. Baseado nisso, o objetivo do nosso trabalho foi avaliar o efeito do T3 e E2 nas concentrações infrafisiológica (T3I/ 10-10M e E2I/ 10-9M); fisiológicas (T3F/10-9M e E2F/10-8M) e suprafisiológicas (T3S/10-8M) separadamente e em diferentes associações de T3I (T3I+E2I e T3I+E2F); T3F (T3F+E2I e T3F+E2F) e T3S (T3S+E2I e T3S + E2F) e diferentes associações de E2I (E2I+T3I e E2I+T3F e E2I+T3S); E2F (E2F+T3I e E2F+T3F e E2F+T3S) sobre a expressão gênica e proteica de RANKL, OPG e c-FOS. Quando associados, a maioria desses hormônios aumentou os níveis gênicos da célula estudada. Em c... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Bone tissue is extremely complex and is regulated by systemic and local factors, presenting a considerable metabolic activity involving the removal of mineralized bone by osteoclasts in balance with the formation of bone matrix by osteoblasts. The association of triiodothyronine (T3) and estrogen (E2) may lead the activity of bone tissue to complex responses, due to T3 effects on both bone formation and reabsorption, and E2 being able to lead to osteoporosis when at low levels, or, at normal levels, maintain the suppression of the cytokines RANKL, OPG, and c-FOS, which take part actively on bone remodeling. To date, many studies have been done to verify hormone actions on bone metabolism. Among them, mesenchymal stem cells (MSC) have been isolated from human adipose tissue and differentiated into osteoblasts. The aim of our study was to evaluate the effect of both T3 and E2 on RANKL, OPG, and c-FOS gene and protein expression, at infra- (T3I, 10-10M; E2I, 10-9M), physiological (T3F, 10-9M; E2F, 10-8M) supra- (T3S, 10-8M) and doses. Cells were treated with hormones separately or in all possible combinations of T3 and E2 doses. The majority of associated treatments increased gene expression levels of all genes. We can state that the doses included in this study, of both hormones, efficiently increase the expression of the analyzed genes, especially when associated. / Doutor

Periprosthetic osteolysis remains the leading complication of total hip arthroplasty. It often results in aseptic loosening of the implant with a requirement for a revision surgery. Wear-generated particular debris is the main cause of initiating this destructive process. The most important cellular target for wear debris is a macrophage, which responds to particle challenge by activatig proinflamatory signals, which contribute to increased bone resorption. The activation of the RANKL/RANK/OPG system is considered to be a likely cause of periprosthetic osteolysis leading to implant failure. The aim of this study was to examine the possible correlation between the clinical extent of osteolysis, the number of wear particles and the expression of the osteoclastic mediator RANKL in the tissues around aseptically loosened cemented and non-cemened total hip replacements. Periprosthetic tissues were harvested from 59 patients undergoing revision hip replacement for aseptic loosening. We had observed RANKL-positive cells in 23 of our 59 patients, their presence was noted predominantly in tissues with a loosened cemented endoprosthesis. We have shown that RANKL is present only in the tissues with a large amount of wear debris and predominantly in the cases involving lacunar type of osteolysis. Key words:...

Periprosthetic osteolysis remains the leading complication of total hip arthroplasty. It often results in aseptic loosening of the implant with a requirement for a revision surgery. Wear-generated particular debris is the main cause of initiating this destructive process. The most important cellular target for wear debris is a macrophage, which responds to particle challenge by activatig proinflamatory signals, which contribute to increased bone resorption. The activation of the RANKL/RANK/OPG system is considered to be a likely cause of periprosthetic osteolysis leading to implant failure. The aim of this study was to examine the possible correlation between the clinical extent of osteolysis, the number of wear particles and the expression of the osteoclastic mediator RANKL in the tissues around aseptically loosened cemented and non-cemened total hip replacements. Periprosthetic tissues were harvested from 59 patients undergoing revision hip replacement for aseptic loosening. We had observed RANKL-positive cells in 23 of our 59 patients, their presence was noted predominantly in tissues with a loosened cemented endoprosthesis. We have shown that RANKL is present only in the tissues with a large amount of wear debris and predominantly in the cases involving lacunar type of osteolysis. Key words:...

Astronauts are at risk of losing 1.0% to 1.5% of their bone mass for every month they spend in space despite their adherence to diets and exercise regimens designed to protect their musculoskeletal systems. This loss is the result of microgravity-related impairment of osteocyte and osteoblast function and the consequent upregulation of osteoclast-mediated bone resorption. This review describes the ontogeny of osteoclast hematopoietic stem cells and the contributions macrophage colony stimulating factor, receptor activator of the nuclear factor-kappa B ligand, and the calcineurin pathways make in osteoclast differentiation and provides details of bone formation, the osteoclast cytoskeleton, the immune regulation of osteoclasts, and osteoclast mechanotransduction on Earth, in space, and under conditions of simulated microgravity. The article discusses the need to better understand how osteoclasts are able to function in zero gravity and reviews current and prospective therapies that may be used to treat osteoclast-mediated bone disease.

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<p>Giant cell tumour of bone (GCT) is an aggressive primary bone tumour with an unclear etiology that presents with significant local osteolysis due in part to the accumulation of multinucleated osteoclast-like giant cells. However, it is the neoplastic spindle-like stromal cells within GCT that largely direct the pathogenesis of the tumour. I hypothesize that parathyroid hormone-related protein (PTHrP) is a key mediator within GCT that promotes the characteristic osteolytic phenotype by stimulating both bone resorption and giant cell formation. The work presented in this thesis collectively demonstrates that the stromal cells express PTHrP and its receptor, the parathyroid hormone type 1 receptor (PTH1R), and that PTHrP acts in an autocrine/paracrine manner within the tumour to stimulate expression of factors that promote bone resorption. Data are presented that demonstrate that PTHrP stimulates stromal cell expression of the receptor activator of nuclear factor-κB ligand (RANKL), a known essential regulator of osteoclastogenesis, which results in increased formation of multinucleated cells from murine monocytes. Moreover, the GCT stromal cells express matrix metalloproteinase (MMP)-1 and MMP-13. These results suggest that the stromal cells may participate directly in bone resorption through the degradation of type I collagen, the promotion of osteoclast activity, or through a combination of these elements. PTHrP also regulates the expression of MMP-13 by the stromal cells. Experiments with CD40 ligand show that local factors present within the tumour can influence PTHrP expression by the stromal cells and potentiate its catabolic effects by stimulation of RANKL and MMP-13 expression. Together, this thesis presents evidence that suggests PTHrP is an important factor in the pathophysiology of GCT by its actions on promoting catabolism within the tumour. The role of PTHrP in normal physiology and the mechanisms of action presented here suggest that research into the effects of PTHrP within GCT may provide invaluable information that enhances our understanding of the biology of this particularly aggressive bone tumour.</p> / Doctor of Philosophy (PhD)

Injuries of the hands and wrist are prevalent in many occupations requiring repetitive tasks and may be further aggravated by advancing age; these injuries are termed work related musculoskeletal disorders (WMSDs). Prior studies using an innovative operant rat model of reaching and grasping as a model of WMSDs demonstrated exposure dependent changes in forelimb bones of young adult rats performing repetitive tasks ≤ 3 months. No one has yet to examine if aging enhances forelimb bone degradative changes occurring with WMSDs, or if forelimb bones adapt or degrade further in response to moderate versus high demand repetitive tasks performed for prolonged time periods (up to 24 months). Bone remodeling is a normal biological process that allows bones to adjust to strains. Unfortunately, both aging and inflammation can deregulate the balance between bone resorption and formation. Aging mammals display increased baseline inflammatory-cytokine levels, both systemically and at the tissue level. Several inflammatory cytokines have been shown to stimulate osteoclastogenesis leading to bone resorption and reduced bone formation. We have reported increased production of inflammatory cytokines in serum and musculotendinous tissues of aged animals performing a repetitive reaching and grasping tasks for up to 12 weeks, warranting further examination of whether aged rats performing these tasks have increased bone resorptive changes, compared to young adult rats. We hypothesized that aging would enhance bone degradative changes in our model as a consequence of increased bone inflammatory responses to a moderate demand repetitive task. Therefore, our first aim was to examine forearm grip strength, trabecular and cortical bone quality, and inflammatory cytokine levels in radii of mature (14-18 mo of age) and young adult (2.5-6.5 mo of age) female Sprague Dawley rats after performance of a high repetition low force (HRLF) task for 12 weeks, compared to each other and age-matched controls. We found that mature rats performing a moderate demand repetitive task for 12 weeks had decreased bone formation and quality, particularly cortical bone quality, compared to young adult rats performing the same task, with increased inflammatory and decreased anti-inflammatory responses, and perhaps lower grip strength, as likely contributors. An adaptive bone response was observed in young adult animals performing a moderate level task of high repetition low force for 12 weeks. In contrast, a previous study showed bone degradative changes in young adult rats performing a high demand task of high repetition high force task for 12 weeks. Osteocytes are the mechanosensing cells of bones, and disruption or changes to their environment can lead to apoptosis or molecular changes. In models of forced bone loading to bone fatigue, osteocyte apoptosis increases sclerostin levels and osteoclast recruitment. Increased sclerostin also leads to increased RANKL production. In contrast, low level loading for a short period reduces sclerostin levels and encourages bone formation. We hypothesized that long-term muscle loading at high repetition low force loads would induce further bone adaptation, but that long-term high repetition high force muscle loading would result in detrimental bone loss, as well as alterations in these two bone remodeling proteins, RANKL and sclerostin. Therefore, our second aim was to determine if prolonged performance of a moderate demand upper extremity reaching and grasping task by young adult rats would continue to enhance forelimb bone formation and quality. We hypothesized that continued performance of a high repetition low force (HRLF) task for 24 weeks would lead to increased bone formation. We also hypothesized that RANKL and sclerostin, two proteins that have not been investigated in our rat model of WMSDs, would be reduced in rats performing a HRLF task for 24 weeks, as the bones reach adaptation. We found that 24 week HRLF rats showed several indices of bone formation and adaptation to the task; as well as reduced sclerostin immunoexpression, compared to controls, a reduction that likely contributed to the enhanced bone formation. To expand on this investigation, in our third aim, we investigated the impact of performance of a high repetition high force (HRHF) task for 18 weeks on young adult rat forelimb bones, and on sclerostin and RANKL levels. We observed detrimental trabecular bone remodeling in the radius, including decreased trabeculae bone volume, number and thickness, increased trabecular separation and anisotropy, and a transition to rod-shaped trabeculae in 18-week HRHF task animals, compared to food restricted control rats. In the 18-week HRHF rats, osteoclast numbers increased and osteoblast numbers decreased, concomitant with increased osteocyte apoptosis and empty lacunae, compared to control rats. Also, mRNA and protein levels of RANKL increased and sclerostin decreased in the 18-week HRHF rats, compared to to control rats. Thus, prolonged performance of a high demand task of high repetition high force induced detrimental trabecular bone changes. The increased RANKL likely contributed to these changes, and although sclerostin level decreased, a change that should contribute to enhanced osteoblast activity, bone formation was not rescued. In conclusion, prolonged performance of a HRLF task by young adult rats leads to reduced sclerostin levels and increased bone formation and bone quality. Aged rats performing the same HRLF task showed increased bone degradative changes that might increase fracture risk. In contrast, prolonged performance of a HRHF task by young adult rats leads to increased bone resorption and degradation, changes associated with RANKL expression. Sclerostin levels were reduced by the HRHF task, but failed to rescue bone formation. / Cell Biology

O conhecimento dos eventos biológicos que ocorrem no periápice dos dentes com necrose pulpar se torna importante para compreender o desenvolvimento das lesões periapicais. Muitas são as moléculas e mediadores que participam na instalação da lesão periapical, a partir da infecção bacteriana que ocorre no interior dos canais radiculares. Assim, o objetivo do presente trabalho foi avaliar moléculas do sistema imune inato, da osteoclastogênese e metaloproteinases em lesões periapicais (LP) induzidas experimentalmente em camundongos knockout e wild type. Para esse objetivo, o presente estudo foi dividido em dois trabalhos distintos. O primeiro teve como objetivo avaliar a expressão de metaloproteinase 2 (MMP2) e metaloproteinase 9 (MMP9) durante a progressão da LP em camundongos knockout para TLR2 (TLR2 KO) e MyD88 (MyD88 KO), em comparação com camundongos wild type (WT). O segundo estudo avaliou a correlação da expressão gênica e imunomarcação de RANK, RANKL, OPG, TLR2 e MyD88 durante a progressão da LP em camundongos WT. No primeiro estudo lesões periapicais foram induzidas em molares inferiores de 54 camundongos TLR2 KO, MyD88 KO e WT (n=18/grupo). Após 7, 21 e 42 dias, os animais foram eutanaziados e as mandíbulas foram dissecadas e submetidas a processamento histotécnico. Os cortes histológicos foram submetidos a imunohistoquímica e posteriormente foi avaliada presença ou ausência de MMP2 e MMP9 nos diferentes grupos. No segundo estudo, 35 camundongos WT foram utilizados. As lesões periapicais foram induzidas nos primeiros molares inferiores de ambos os lados. Após 0 (G0), 7 (G7), 21 (G21) e 42 (G42) dias, os animais foram anestesiados e eutanasiados para que as mandíbulas fossem dissecadas e divididas ao meio.O lado direito das mandíbulas foi para o processamento histotécnico, para posterior marcação de RANK, RANKL, OPG, TLR2 e MyD88, por meio da imuno-histoquímica do lado esquerdo da mandíbula foi utilizado para a extração de RNA, para a determinação da expressão gênica de RANK (Tnfrsf11a), RANKL (Tnfrsf11), OPG (Tnfrsf11b), TLR2 (Tlr2) e MyD88 (Myd88) utilizando quantificação em Tempo Real da Reação da Polimerase em Cadeia (qRT-PCR). Para ambos os estudos, testes paramétricos e não paramétricos foram realizados com nível de significância de 5%. Foi possível observar, no primeiro estudo, que nos períodos iniciais da progressão da lesão periapical, houve um aumento na imunomarcação de MMP9 nos camundongos TLR2 KO e MyD88 KO, quando comparados aos WT, diferente da MMP2 que não se observou nenhum aumento na imunomarcação. No entanto, aos 42 dias observou-se uma redução da imunomarcação de MMP2 e um aumento da MMP9 nos camundongos TLR2 KO. Adicionalmente, no segundo estudo, foi possível observar um aumento da imunomarcação para RANK, RANKL, OPG, TLR2 e MyD88 durante a progressão da lesão periapical (p<0,05). O aumento da expressão de Tnfrsf11 foi diferente entre os grupos G0 e G42, e G21 e G42 (p=0,006). No entanto, a expressão de Tnfrsf11b foi diferente entre os grupos G0 e G7, G7, G21 e G42, sendo possível observar uma diminuição dessa expressão ao longo do tempo (p<0,001). Tlr2 foi mais expresso entre os grupos G0 e G42 (p=0,03). E a expressão da molécula Myd88 foi estatisticamente significante entre os grupos G0 e G7, G21 e G42 (p=0,01). A razão Tnfrsf11/Tnfrsf11b aumentou durante a progressão da lesão periapical (p=0,002). Também foi possível observar uma correlação moderada entre Myd88 e Rankl (r=0,42; p=0,03) e entre Myd88 e Tlr2 (r=0,48; p<0,0001). Após as metodologias empregadas e os dados analisados, concluímos que a produção de MMP2 e MMP9 foi modulada por TLR2 e Myd88 durante a progressão da lesão periapical. Alem disso, podemos sugerir que existe uma correlação positiva entre o sistema RANK/RANKL/OPG e as proteínas do sistema imune inato, TLR2 e MyD88, durante a perda óssea decorrente da infecção bacteriana dos canais radiculares e posterior progressão da lesão periapical. / Knowledge of the biological events occurring inteeth apex with pulp necrosis becomes important to understand the development of periapical lesions. There are manymolecules and mediators that participate in the installation of the periapical lesion, from the bacterial infection that occurs inside the root canals. Thus, the aim of the present study was to evaluate molecules of the innate immune system, osteoclastogenesis and metalloproteinases in experimentally apical periodontitis (AP) induced in knockout and wild type mice. For this purpose, the present study was divided into two distinct studies. The first one aimed to evaluate the expression of metalloproteinases 2 (MMP2) and metalloproteinases 9 (MMP9) during the progression of AP in TLR2 knockout mice (TLR2 KO) and MyD88 knockout mice (MyD88 KO), compared to wild type mice (WT). The second study evaluated the correlation of gene expression and immunostaining of RANK, RANKL, OPG, TLR2 and MyD88 during LP progression in WT mice. In the first study AP were induced in lower molars of 54 TLR2 KO, MyD88 KO and WT mice (n = 18 / group). After 7, 21 and 42 days, the animals were euthanized and the jaws were dissected and submitted to histotechnical processing. The histological sections were submitted to immunohistochemistry and subsequently the presence or absence of MMP2 and MMP9 in the different groups was evaluated. In the second study, 35 WT mice were used. Periapical lesions were induced in the lower first molars on both sides. After 0 (G0) to 7 (G7), 21 (G21) and 42 (G42) days, the animals were anesthetized and euthanized so that the jaws were dissected and divided in half. The right side of the jaws was for the histotechnic processing, for subsequent imunostaining of RANK, RANKL, OPG, TLR2 and MyD88, through immunohistochemistry and the left side of the jaws was used for the extraction of RNA, for the determination of expression of RANK (Tnfrsf11a), RANKL (Tnfrsf11), OPG (Tnfrsf11b), TLR2 (Tlr2) and MyD88 (Myd88) using Quantification Real Time of Polymerase Chain Reaction (qRT-PCR). For both studies, parametric and non-parametric tests were performed with significance level of 5%. It was possible to observe in the first study that in the initial periods of AP progression there was an increase in MMP9 immunostaining in TLR2 KO and MyD88 KO mice when compared to WT, different from MMP2 that no increase in immunostaining was observed. However, at 42 days there was a reduction in MMP2 immunostaining and an increase of MMP9 in TLR2 KO mice was observed. Additionally, in the second study, it was possible to observe an increase in the immunostaining for RANK, RANKL, OPG, TLR2 and MyD88 during periapical lesion progression (p <0.05). The increase in Tnfrsf11 expression was different between groups G0 and G42, and G21 and G42 (p = 0.006). However, the expression of Tnfrsf11b was different between the G0 and G7, G7, G21 and G42 groups, and a decrease in expression over time (p <0.001) was observed. Tlr2 was more expressed between the G0 and G42 groups (p = 0.03). And the expression of the Myd88 molecule was statistically significant between the G0 and G7, G21 and G42 groups (p = 0.01). The Tnfrsf11 / Tnfrsf11b ratio increased during the AP progression (p = 0.002). It was also possible to observe a moderate correlation between Myd88 and Rankl (r = 0.42, p = 0.03) and between Myd88 and Tlr2 (r = 0.48, p <0.0001). After the methodologies used and the data analyzed, we conclude that the production of MMP2 and MMP9 was modulated by TLR2 and Myd88 during the AP progression. In addition, we can suggest that there is a positive correlation between the RANK / RANKL / OPG system and the proteins of the innate immune system, TLR2 and MyD88, during bone loss due to bacterial infection of the root canals and subsequent progression of the apical periodontitis.

O diabete melito é uma doença metabólica com alta prevalência na população e quando no estado descompensado pode causar diversas complicações metabólicas e clínicas, entre elas a osteoporose. Entretanto, ainda não foram completamente esclarecidos os mecanismos pelos quais o diabete diminui a densidade mineral óssea e aumenta o risco a fraturas. Recentemente foram descritos alguns genes que estão envolvidos no turnover ósseo: OPG, RANK e RANKL. Além disso, o uso de hipoglicemiantes orais como as tiazolidinedionas (TZD), pode influenciar negativamente o metabolismo ósseo. Com a finalidade de identificar marcadores sensíveis de alteração do metabolismo ósseo foram investigadas as relações entre a expressão dos genes OPG, RANK e RANKL em células do sangue periférico e a resposta a TZDs em pacientes com DM2. Foram selecionados 52 indivíduos (36 diabéticos e 16 normoglicêmicos), no Instituto Dante Pazzanese de Cardiologia. Os indivíduos diabéticos foram tratados com pioglitazona (15, 30 e 45 mg/ dia/ via oral) por 16 semanas. Foram colhidas amostras de sangue, antes e após o tratamento para determinação de exames laboratoriais e extração de RNA total. A expressão de mRNA dos genes OPG, RANK e RANKL foi quantificada e avaliada por RT-PCR em tempo real, empregando-se o GAPD como controle endógeno. Observou-se que nos pacientes DM2 após o tratamento com pioglitazona, houve diminuição da glicemia de jejum, glicemia pós-prandial, insulina, Hb1Ac, índices HOMA-IR e HOMA-&#946; e aumento nas concentrações séricas de HDL, demonstrando a eficácia do tratamento. Ao comparar a expressão dos genes entre o grupo DM2 (sem tratamento) e o grupo normoglicêmico (NG), foi evidenciado um aumento da expressão de OPG no grupo NG em relação ao grupo DM2, e ao analisar a expressão entre as mulheres, constatou-se aumento da expressão de RANK no grupo DM2 em relação ao grupo NG. Além disso, ao correlacionar a expressão dos genes com as dosagens dos parâmetros bioquímicos, constatou-se que o aumento da expressão de RANK e RANKL está relacionado com o aumento das concentrações de cálcio ionizado e diminuição da expressão de OPG. Esses dados sugerem que a atividade osteoclástica está aumentada nos pacientes DM2 e com o tratamento o quadro osteoporótico pode ser agravado. / The diabetes mellitus is a metabolic disease with high prevalence in the population and can cause various metabolic and clinic complications, including osteoporosis, when it is decompensated. However, the mechanisms by which diabetes decreases bone mineral density and increases the risk of fractures are not completely clarified. Recently some genes which are involved in bone turnover were described: OPG, RANK and RANKL. Moreover, the treatment using oral hypoglycemic drugs such as thiazolidinediones (TZD), may negatively affect the bone metabolism. In order to identify sensitive markers related to the bone metabolism, were investigated the relationship between the expression of genes OPG, RANK and RANKL in peripheral blood leukocytes and the response to TZDs treatment in patients with DM2. Fifty-two individuals were selected (36 diabetics and 16 normoglycemics) at Dante Pazzanese Institute of Cardiology. Diabetic patients were treated with pioglitazone (15, 30 and 45 mg I day I oral) during 16 weeks. Blood samples were collected for biochemical analyses and total RNA extraction, before and after treatment. Gene expression of the genes OPG, RANK and RANKL in peripheral blood mononuclear cells was evaluated by Real Time PCR, using the GAPD housekeeping gene as the endogenous reference. In DM2 patients after treatment with pioglitazone there was reduction in their fasting glycemia, postprandial glycemia, insulin, Hb1Ac, HOMA-IR and HOMA-&#946; indices, and their serum concentrations of HDL increased, which demonstrates the effectiveness of the treatment. The bone profile markers have not altered after treatment, suggesting an anabolic action of the insulin in bone metabolism of these patients. Normoglycemics (NG) group gene expression, when compared with DM2 group (with no treatment), had increased OPG expression. Besides, RANK expression in group DM2 was higher than NG group when it was analyzed among women. Furthermore, having correlated the expression of the genes with the biochemical parameters data, the increase on RANK and RANKL gene expression is related to increased concentrations of ionized calcium and to decreased expression of OPG gene. These results are suggestive that osteoclastic activity is higher in DM2 patients, the treatment can exacerbate osteoporosis severity and the bone markers does not have enough sensibility to differentiate changes in individuals with type 2 diabetes mellitus.

O conhecimento dos eventos biológicos que ocorrem no periápice dos dentes com necrose pulpar se torna importante para compreender o desenvolvimento das lesões periapicais. Muitas são as moléculas e mediadores que participam na instalação da lesão periapical, a partir da infecção bacteriana que ocorre no interior dos canais radiculares. Assim, o objetivo do presente trabalho foi avaliar moléculas do sistema imune inato, da osteoclastogênese e metaloproteinases em lesões periapicais (LP) induzidas experimentalmente em camundongos knockout e wild type. Para esse objetivo, o presente estudo foi dividido em dois trabalhos distintos. O primeiro teve como objetivo avaliar a expressão de metaloproteinase 2 (MMP2) e metaloproteinase 9 (MMP9) durante a progressão da LP em camundongos knockout para TLR2 (TLR2 KO) e MyD88 (MyD88 KO), em comparação com camundongos wild type (WT). O segundo estudo avaliou a correlação da expressão gênica e imunomarcação de RANK, RANKL, OPG, TLR2 e MyD88 durante a progressão da LP em camundongos WT. No primeiro estudo lesões periapicais foram induzidas em molares inferiores de 54 camundongos TLR2 KO, MyD88 KO e WT (n=18/grupo). Após 7, 21 e 42 dias, os animais foram eutanaziados e as mandíbulas foram dissecadas e submetidas a processamento histotécnico. Os cortes histológicos foram submetidos a imunohistoquímica e posteriormente foi avaliada presença ou ausência de MMP2 e MMP9 nos diferentes grupos. No segundo estudo, 35 camundongos WT foram utilizados. As lesões periapicais foram induzidas nos primeiros molares inferiores de ambos os lados. Após 0 (G0), 7 (G7), 21 (G21) e 42 (G42) dias, os animais foram anestesiados e eutanasiados para que as mandíbulas fossem dissecadas e divididas ao meio.O lado direito das mandíbulas foi para o processamento histotécnico, para posterior marcação de RANK, RANKL, OPG, TLR2 e MyD88, por meio da imuno-histoquímica do lado esquerdo da mandíbula foi utilizado para a extração de RNA, para a determinação da expressão gênica de RANK (Tnfrsf11a), RANKL (Tnfrsf11), OPG (Tnfrsf11b), TLR2 (Tlr2) e MyD88 (Myd88) utilizando quantificação em Tempo Real da Reação da Polimerase em Cadeia (qRT-PCR). Para ambos os estudos, testes paramétricos e não paramétricos foram realizados com nível de significância de 5%. Foi possível observar, no primeiro estudo, que nos períodos iniciais da progressão da lesão periapical, houve um aumento na imunomarcação de MMP9 nos camundongos TLR2 KO e MyD88 KO, quando comparados aos WT, diferente da MMP2 que não se observou nenhum aumento na imunomarcação. No entanto, aos 42 dias observou-se uma redução da imunomarcação de MMP2 e um aumento da MMP9 nos camundongos TLR2 KO. Adicionalmente, no segundo estudo, foi possível observar um aumento da imunomarcação para RANK, RANKL, OPG, TLR2 e MyD88 durante a progressão da lesão periapical (p<0,05). O aumento da expressão de Tnfrsf11 foi diferente entre os grupos G0 e G42, e G21 e G42 (p=0,006). No entanto, a expressão de Tnfrsf11b foi diferente entre os grupos G0 e G7, G7, G21 e G42, sendo possível observar uma diminuição dessa expressão ao longo do tempo (p<0,001). Tlr2 foi mais expresso entre os grupos G0 e G42 (p=0,03). E a expressão da molécula Myd88 foi estatisticamente significante entre os grupos G0 e G7, G21 e G42 (p=0,01). A razão Tnfrsf11/Tnfrsf11b aumentou durante a progressão da lesão periapical (p=0,002). Também foi possível observar uma correlação moderada entre Myd88 e Rankl (r=0,42; p=0,03) e entre Myd88 e Tlr2 (r=0,48; p<0,0001). Após as metodologias empregadas e os dados analisados, concluímos que a produção de MMP2 e MMP9 foi modulada por TLR2 e Myd88 durante a progressão da lesão periapical. Alem disso, podemos sugerir que existe uma correlação positiva entre o sistema RANK/RANKL/OPG e as proteínas do sistema imune inato, TLR2 e MyD88, durante a perda óssea decorrente da infecção bacteriana dos canais radiculares e posterior progressão da lesão periapical. / Knowledge of the biological events occurring inteeth apex with pulp necrosis becomes important to understand the development of periapical lesions. There are manymolecules and mediators that participate in the installation of the periapical lesion, from the bacterial infection that occurs inside the root canals. Thus, the aim of the present study was to evaluate molecules of the innate immune system, osteoclastogenesis and metalloproteinases in experimentally apical periodontitis (AP) induced in knockout and wild type mice. For this purpose, the present study was divided into two distinct studies. The first one aimed to evaluate the expression of metalloproteinases 2 (MMP2) and metalloproteinases 9 (MMP9) during the progression of AP in TLR2 knockout mice (TLR2 KO) and MyD88 knockout mice (MyD88 KO), compared to wild type mice (WT). The second study evaluated the correlation of gene expression and immunostaining of RANK, RANKL, OPG, TLR2 and MyD88 during LP progression in WT mice. In the first study AP were induced in lower molars of 54 TLR2 KO, MyD88 KO and WT mice (n = 18 / group). After 7, 21 and 42 days, the animals were euthanized and the jaws were dissected and submitted to histotechnical processing. The histological sections were submitted to immunohistochemistry and subsequently the presence or absence of MMP2 and MMP9 in the different groups was evaluated. In the second study, 35 WT mice were used. Periapical lesions were induced in the lower first molars on both sides. After 0 (G0) to 7 (G7), 21 (G21) and 42 (G42) days, the animals were anesthetized and euthanized so that the jaws were dissected and divided in half. The right side of the jaws was for the histotechnic processing, for subsequent imunostaining of RANK, RANKL, OPG, TLR2 and MyD88, through immunohistochemistry and the left side of the jaws was used for the extraction of RNA, for the determination of expression of RANK (Tnfrsf11a), RANKL (Tnfrsf11), OPG (Tnfrsf11b), TLR2 (Tlr2) and MyD88 (Myd88) using Quantification Real Time of Polymerase Chain Reaction (qRT-PCR). For both studies, parametric and non-parametric tests were performed with significance level of 5%. It was possible to observe in the first study that in the initial periods of AP progression there was an increase in MMP9 immunostaining in TLR2 KO and MyD88 KO mice when compared to WT, different from MMP2 that no increase in immunostaining was observed. However, at 42 days there was a reduction in MMP2 immunostaining and an increase of MMP9 in TLR2 KO mice was observed. Additionally, in the second study, it was possible to observe an increase in the immunostaining for RANK, RANKL, OPG, TLR2 and MyD88 during periapical lesion progression (p <0.05). The increase in Tnfrsf11 expression was different between groups G0 and G42, and G21 and G42 (p = 0.006). However, the expression of Tnfrsf11b was different between the G0 and G7, G7, G21 and G42 groups, and a decrease in expression over time (p <0.001) was observed. Tlr2 was more expressed between the G0 and G42 groups (p = 0.03). And the expression of the Myd88 molecule was statistically significant between the G0 and G7, G21 and G42 groups (p = 0.01). The Tnfrsf11 / Tnfrsf11b ratio increased during the AP progression (p = 0.002). It was also possible to observe a moderate correlation between Myd88 and Rankl (r = 0.42, p = 0.03) and between Myd88 and Tlr2 (r = 0.48, p <0.0001). After the methodologies used and the data analyzed, we conclude that the production of MMP2 and MMP9 was modulated by TLR2 and Myd88 during the AP progression. In addition, we can suggest that there is a positive correlation between the RANK / RANKL / OPG system and the proteins of the innate immune system, TLR2 and MyD88, during bone loss due to bacterial infection of the root canals and subsequent progression of the apical periodontitis.