Navegando por Palavras-chave "ESTROGENIOS"

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    Expressão de receptor de estrógeno beta e apoptose
    (Universidade Federal de São Paulo (UNIFESP), 2009-01-28) Crusoé-Souza, Mady [UNIFESP]; Cerri, Paulo Sergio [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Introduction: Combined and coordinated action among osteoblasts, osteocytes and osteoclasts is responsable for bone tissue homeostasis. Local and systemic factors regulate bone formation and resorption processes, controlling proliferation, differentiation, activity and survival of bone cells. Estrogen is widely used to inhibit bone resorption in menopausal women. This hormone acts on osteoblasts and mesenchymaI cells, controlling the production of growing factors and cytokines which are important for the osteoclasts formation, activity and survival. The presence of estrogen receptors in bone cells has been demonstrated; nevertheless, the expression of these receptors is variable according to the bone histophysiology and type. Purpose: The aim of this study was to investigate which alveolar bone cells express estrogen receptors beta in estradiol-treated and untreated rats. Considering that estrogen induces apoptosis in osteoclasts, a quantitative analysis of osteoclasts and a possible relationship between apoptosis and estrogen receptor beta expression in these cells were also carried out. Material and Methods: Ten, 22-dayold female rats were divided into two groups: estrogen group (EG) and sham control group (SG). EG animals received injections of 0.125mg/100g body weight estradiol hexahydrobenzoate daily, for 14 days. SG animals received injections of corn oil, used as the dilution vehicle of estrogen. Twenty four hours after the last injection, fragments of the maxilla containing alveolar bone surrounding the upper molars were removed and immersed in formaldehyde. After decalcification, the fragments were dehydrated and embedded in paraffin. Some sections were stained with hematoxylin and eosin. For quantitative analysis of the number of osteoclasts, alveolar bone sections were submitted to the TRAP (tartrate-resistant acid phosphatase), used as osteoclast marker. The number of TRAP-positive osteoclasts/mm of bone surface was carried out, and the statistical analysis was performed using the Mann-Whitney test (p ≤ 0.05). Sections were submitted to immunohistochemistry reaction for estrogen receptor beta (ERβ); for detection of apoptosis, the TUNEL (Terminal deoxynucleotidyl transferase-mediated dUTP Nick-End Labeling) method was used. Sections were also submitted to the double labeling: immunohistochemistry reaction for ERβ followed by the TUNEL method. Some fragments of alveolar bone were removed, immersed in fixative solution and processed for transmission electron microscopy. Results: The number of TRAP-positive osteoclasts/mm of alveolar bone surface was significantly reduced in the EG in comparison to SG. Immunoreaction for ERβ was observed in the cytoplasm and nuclei of osteoblasts, osteocytes and osteoclasts in the sham and estrogen groups. In EG, the double labeling revealed TUNEL-positive nuclei in the osteoclasts immuno-positive for ERβ. The ultrastructural results showed shrunken osteoclasts exhibiting nuclei with conspicuous masses of condensed peripheral chromatin and citoplasmatic blebs, indicating apoptosis. Conclusions: Estrogen seems to have an important role in the bone homeostasis via estrogen receptors beta. The presence of ERβ-positive osteoclasts, exhibiting TUNEL-positive nuclei, in the EG, indicates that estrogen acts directly on osteoclasts and may induce apoptosis. These results reinforce the idea that estrogen induces osteoclasts apoptosis and may be responsible, at least in part, for the reduction in the alveolar bone resorption in estrogen-treated rats.