Approved Abstracts

Methylmercury exposure during pregnancy and lactation elicits physicochemical, ultrastructural and morphological impairments on the alveolar bone of offspring rats



Author(s): Chemelo VS; Nascimento PC; Bittencourt LO; Albuquerque ARL; Paz SPA; Angélica RS; Collares FM; Prado AF; Crespo-López ME; Lima RR;
Presenter: Leonardo Oliveira Bittencourt

Methylmercury (MeHg) is the most toxic form of mercury and considered a potential environmental pollutant. Several populations live in endemic regions of MeHg exposure and subjected to the toxicant for long periods. The MeHg toxic effects are mainly associated with neurological system impairments, including when organisms are exposed during the neurodevelopment period. However, evidences regarding the effects of MeHg on bone structures are scarce, and when it comes to alveolar bone and intrauterine and/or lactation period, they are inexistent. The alveolar bone is an important structure for stomatognathic system, responsible for teeth support and reabsorption of occlusal forces in oral cavity. Thus, considering the fundamental importance of alveolar bone for oral health, this study aimed to investigate the effects of MeHg exposure during pregnancy and lactation on the offspring rats’ alveolar bone, in order to characterize possible damages at physicochemical level, ultrastructural and morphological organization of the alveolar bone. For this, female rats were exposed during pregnancy and lactation to a dose of 40 μg/kg/day, equivalent to human consumption in riverside communities. The experimental protocol was carried out in two groups: the rats were directly exposed though cookies (containing or not MeHg) during the ± 21 days of pregnancy and the period of 21 days of lactation. Then, the mandibles of the offspring were collected and the alveolar bone analyzed through Fourier Transform Infrared Spectroscopy (FTIR-ATR) to evaluate the physicochemical composition; through Scanning Electron Microscopy (SEM) for ultrastructural evaluation; through histological analyses by Hematoxylin and Eosin and PicroSirius Red staining methods to evaluate osteocytes density and collagen fibers, respectively. Trabeculae and bone volume by x-ray microtomography analysis was also performed. The data were analyzed by Student’s t-test, adopting p<0.05. The unprecedented results showed that the exposure to MeHg during lactation and pregnancy showed changes in the mineral component of the alveolar bone. Moreover, in the morphological analyses, it was observed differences in alveolar bone integrity associated with a reduced osteocyte density and decrease on bone collagen fibers content. Furthermore, the exposure to MeHg showed reduced trabecular thickness and bone volume and an increase of trabecular spaces, resulting in an increase in exposed root area and a decrease dimensional in bone height. In this way, the results pointed for the first time that the alveolar bone structure is susceptible to MeHg toxic effects, when organisms are exposed during intrauterine and lactation periods. These physicochemical and morphological findings suggest impairments on stomatognathic system homeostasis, and in a translational perspective, the assessment of changes in the mineral content, morphology and structure of alveolar bone can help us to understand possible abnormalities induced by toxic metals, as well as highlight the need for care for structures other than those already seen as targets for damage triggered by environmental exposure to MeHg, especially regarding the children oral health. This study was financed in part by the Programa Nacional de Cooperação Acadêmica na Amazônia – PROCAD/Amazônia from the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - This research was also supported by Pró-Reitoria de Pesquisa da UFPA (PROPESP, UFPA, Brazil) and Brazilian National Council for Scientific and Technological Development (CNPq).

Keywords: Mercury; Alveolar bone; Morphology

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