Avaliação do processo de reparo peri-implantar em ratas tratadas com dose oncológica ou dose osteoporótica de zoledronato
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Data
2019-02-20
Autores
Toro, Luan Felipe
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Universidade Estadual Paulista (Unesp)
Resumo
Bisfosfonatos (BPs) são fármacos amplamente empregados no tratamento de condições que desencadeiam osteólise, atuando via inibição do processo de reabsorção óssea. Os BPs de maior potência, como o zoledronato, são utilizados para o controle da progressão de metástase óssea em neoplasias malignas osteotrópicas ou para o tratamento da osteoporose severa. Todavia, um dos seus efeitos adversos é a ocorrência da osteonecrose dos maxilares associada à terapia medicamentosa (ONM-M). Dentre os principais fatores de risco locais para a ONM-M destacam-se as intervenções odontológicas invasivas, como as cirurgias para instalação de implantes dentários osseointegráveis. Apesar do aumento no número de relatos clínicos de ONM-M após a instalação de implantes dentários em pacientes tratados com BPs, poucos são os estudos que visam compreender quais as alterações que desencadeiam esta condição. Diante disso, o objetivo deste estudo foi analisar o processo de reparo peri-implantar na tíbia de ratas tratadas com dose oncológica ou dose osteoporótica de zoledronato e avaliar a existência de correlação entre tal processo e a ocorrência de lesões osteonecróticas. Quarenta ratas (6 meses) foram distribuídas em dois experimentos: Experimento I: receberam injeções intraperitoneais (IP) de 0,45ml de solução de cloreto de sódio (NaCl) 0,9% (grupo VEI-ONC, n=10) ou desta mesma solução acrescida de 100µg/Kg de zoledronato (grupo ZOL-ONC, n=10), a cada 4 dias, durante 8 semanas; Experimento II: receberam injeções IP de 0,45ml de NaCl 0,9% (grupo VEI-OST, n=10) ou desta mesma solução acrescida de 100µg/Kg de zoledronato (grupo ZOL-OST, n=10), a cada 28 dias, durante 24 semanas. Em ambos os experimentos, decorridas 16 semanas do início do protocolo medicamentoso, os animais foram submetidos à instalação de um implante de titânio nas tíbias direita e esquerda. A eutanásia foi efetuada aos 56 dias pós-operatórios. Após a dissecção e realização de um minucioso exame clínico da região peri-implantar, as tíbias esquerdas foram submetidas ao escaneamento microtomográfico para análise da microarquitetura e estruturação do tecido ósseo peri-implantar e, posteriormente, ao processamento histológico por desgaste para análise histométrica do contato osso/implante (COI), um parâmetro para avaliação da osseointegração dos implantes de titânio. As tíbias direitas foram submetidas ao processamento histológico convencional pós-desmineralização, e as secções histológicas foram coradas pela hematoxilina-eosina para análise histopatológica dos tecidos peri-implantares e adjacentes, análise histométrica da porcentagem de tecido ósseo total (PTO-T) e da porcentagem de tecido ósseo não vital (PTO-NV) na região peri-implantar, ou destinadas à reação imunoistoquímica para detecção e quantificação da proteína morfogenética óssea 2/4 (BMP2/4, Bone morphogenetic protein 2/4), do fator de transcrição relacionado à runt 2 (RUNX2, Runt-related transcription factor 2), da osteocalcina (OCN, Osteocalcin), e da fosfatase ácida resistente ao tartarato (TRAP, Tartrate-resistant acid phosphatase). Os dados foram analisados estatisticamente com nível de significância de 5%. ZOL-ONC apresentou maior porcentagem de volume ósseo e menor porosidade total em relação aos grupos VEI-ONC e ZOL-OST, e maior PTO-T em relação ao grupo VEI-ONC. ZOL-ONC e ZOL-OST apresentaram maior PTO-NV e menor número de células RUNX2-positivas e OCN-positivas em relação aos grupos VEI-ONC e VEI-OST, respectivamente, além de extensas áreas de tecido ósseo não vital e focos de inflamação. O COI e o número de células BMP2/4-positivas e TRAP-positivas não diferiram entre os grupos, porém, estas últimas exibiram características de inatividade em ZOL-ONC e ZOL-OST. Deste modo, conclui-se que o tratamento com dose oncológica ou dose osteoporótica de zoledronato não afeta negativamente a osseointegração dos implantes de titânio e a quantidade de tecido ósseo peri-implantar, porém ocasiona o surgimento de áreas de tecido ósseo não vital e focos de inflamação, o que sugere que a instalação de implantes osseointegráveis deva ser vista com grande cautela em tais condições, pois pode constituir-se em um importante fator de risco local para o desencadeamento da ONM-M.
Bisphosphonates (BPs) are drugs widely used for the treatment of conditions that cause osteolysis, by inhibition of the bone resorption process. High potency BPs, such as zoledronate, are used to control the progression of bone metastasis in osteotropic malignant neoplasms or for the treatment of severe osteoporosis. However, one of its adverse effects is the occurrence of medication-related osteonecrosis of the jaws (MRONJ). Among the main local risk factors for MRONJ are invasive dental procedures, such as surgeries for installation of osseointegratable dental implants. Despite the increased number of clinical reports of MRONJ after installation of dental implants in patients treated with BPs, there are few studies that aim to understand the changes triggering this condition. So, the objective of this study was to analyze the peri-implant repair process in the tibia of rats treated with oncologic dose or osteoporotic dose of zoledronate and to evaluate the existence of correlation between this process and the occurrence of osteonecrotic lesions. Forty female rats (6 months old) were distributed in two experiments: Experiment I: rats received intraperitoneal (IP) injections of 0.45ml of 0.9% sodium chloride (NaCl) solution (group VEI-ONC, n=10) or this same solution added by 100µg/Kg of zoledronate (group ZOL-ONC, n=10), every 4 days for 8 weeks; Experiment II: rats received IP injections of 0.45ml of 0.9% NaCl solution (group VEI-OST, n=10) or this same solution added by 100µg/Kg of zoledronate (group ZOL-OST, n=10), every 28 days for 24 weeks. In both experiments, 16 weeks after the beginning of drug protocol, all animals were submitted to installation of a titanium implant in both right and left tibiae. Euthanasia was performed at day 56 postoperatively. After dissection and a through clinical examination of the peri-implant area, left tibiae were submitted to microtomographic scanning for analysis of the microarchitecture and structuring of peri-implant bone tissue and, later, to ground-section histological processing for histometric analysis of the bone/implant contact (BIC), a parameter for evaluation of the osseointegration of titanium implants. The right tibiae were submitted to conventional histological processing after demineralization, and the histological sections were stained by hematoxilin-eosin for histopathological analysis of the peri-implant tissues and adjacencies, histometric analysis of the percentage of total bone tissue (PTBT) and the percentage of non-vital bone tissue (PNVBT) in the peri-implant area, or intended for immunohistochemical reaction for detection and quantification of bone morphogenetic protein 2/4 (BMP2/4), runt-related transcription factor 2 (RUNX2), osteocalcin (OCN) and tartrate-resistant acid phosphatase (TRAP). Data were statistically analyzed at significance level of 5%. ZOL-ONC presented higher percentage of bone volume and lower total porosity in relation to groups VEI-ONC and ZOL-OST, and higher PTBT in relation to group VEI-ONC. Groups ZOL-ONC and ZOL-OST presented higher PNVBT and smaller number of RUNX2-positive cells and OCN-positive cells than groups VEI-ONC and VEI-OST, respectively, as well as extensive areas of non-vital bone tissue and foci of inflammation. BIC and the number of BMP2/4-positive cells and TRAP-positive cells did not differ amongst groups, however, these last cells exhibited features of inactivity in ZOL-ONC and ZOL-OST. Thus, it is concluded that the treatment with oncologic dose or osteoporotic dose of zoledronate does not negatively affects osseointegration of titanium implants and the amount of peri-implant bone tissue, but it does cause areas of non-vital bone tissue and inflammation foci, suggesting that installation of osseointegratable implants should be viewed with great caution in such conditions, since it may constitute an important local risk factor for the onset of MRONJ.
Bisphosphonates (BPs) are drugs widely used for the treatment of conditions that cause osteolysis, by inhibition of the bone resorption process. High potency BPs, such as zoledronate, are used to control the progression of bone metastasis in osteotropic malignant neoplasms or for the treatment of severe osteoporosis. However, one of its adverse effects is the occurrence of medication-related osteonecrosis of the jaws (MRONJ). Among the main local risk factors for MRONJ are invasive dental procedures, such as surgeries for installation of osseointegratable dental implants. Despite the increased number of clinical reports of MRONJ after installation of dental implants in patients treated with BPs, there are few studies that aim to understand the changes triggering this condition. So, the objective of this study was to analyze the peri-implant repair process in the tibia of rats treated with oncologic dose or osteoporotic dose of zoledronate and to evaluate the existence of correlation between this process and the occurrence of osteonecrotic lesions. Forty female rats (6 months old) were distributed in two experiments: Experiment I: rats received intraperitoneal (IP) injections of 0.45ml of 0.9% sodium chloride (NaCl) solution (group VEI-ONC, n=10) or this same solution added by 100µg/Kg of zoledronate (group ZOL-ONC, n=10), every 4 days for 8 weeks; Experiment II: rats received IP injections of 0.45ml of 0.9% NaCl solution (group VEI-OST, n=10) or this same solution added by 100µg/Kg of zoledronate (group ZOL-OST, n=10), every 28 days for 24 weeks. In both experiments, 16 weeks after the beginning of drug protocol, all animals were submitted to installation of a titanium implant in both right and left tibiae. Euthanasia was performed at day 56 postoperatively. After dissection and a through clinical examination of the peri-implant area, left tibiae were submitted to microtomographic scanning for analysis of the microarchitecture and structuring of peri-implant bone tissue and, later, to ground-section histological processing for histometric analysis of the bone/implant contact (BIC), a parameter for evaluation of the osseointegration of titanium implants. The right tibiae were submitted to conventional histological processing after demineralization, and the histological sections were stained by hematoxilin-eosin for histopathological analysis of the peri-implant tissues and adjacencies, histometric analysis of the percentage of total bone tissue (PTBT) and the percentage of non-vital bone tissue (PNVBT) in the peri-implant area, or intended for immunohistochemical reaction for detection and quantification of bone morphogenetic protein 2/4 (BMP2/4), runt-related transcription factor 2 (RUNX2), osteocalcin (OCN) and tartrate-resistant acid phosphatase (TRAP). Data were statistically analyzed at significance level of 5%. ZOL-ONC presented higher percentage of bone volume and lower total porosity in relation to groups VEI-ONC and ZOL-OST, and higher PTBT in relation to group VEI-ONC. Groups ZOL-ONC and ZOL-OST presented higher PNVBT and smaller number of RUNX2-positive cells and OCN-positive cells than groups VEI-ONC and VEI-OST, respectively, as well as extensive areas of non-vital bone tissue and foci of inflammation. BIC and the number of BMP2/4-positive cells and TRAP-positive cells did not differ amongst groups, however, these last cells exhibited features of inactivity in ZOL-ONC and ZOL-OST. Thus, it is concluded that the treatment with oncologic dose or osteoporotic dose of zoledronate does not negatively affects osseointegration of titanium implants and the amount of peri-implant bone tissue, but it does cause areas of non-vital bone tissue and inflammation foci, suggesting that installation of osseointegratable implants should be viewed with great caution in such conditions, since it may constitute an important local risk factor for the onset of MRONJ.
Descrição
Palavras-chave
Difosfonatos, Implantes dentários, Osseointegração, Osteonecrose, Dental implants, Diphosphonates, Osseointegration, Osteonecrosis