ESTROGEN DEPLETION INCREASES OSTEOCYTE CANALICULAR DIAMETER INCORTICAL AND CANCELLOUS BONE OF THE RAT PROXIMAL TIBIA

摘要

Estrogen depletion has been shown to cause bone loss in the proximal metaphysis of the rat tibia [1,2]. A decrease in bone volume fraction is frequently reported, yet there is little analysis in the literature related to changes in microporosities during osteoporosis. Our recent work quantifying microporosity changes due to estrogen depletion has shown an increase in the lacunar-canalicular porosity surrounding osteocytes in the proximal metaphysis of the rat tibia [3].Osteocytic osteolysis, the process by which osteocytes may modify their immediate environment through microresorption [4], could explain the increase in lacunar-canalicular porosity in the metaphysis of ovariectomized animals. Resorption of the lacunar and canalicular surfaces surrounding osteocytes would result in a broadening of the interstitial fluid spaces, and the larger pores would allow a larger volume of fluid to move during cyclic loading, enhancing molecular transport through the lacunar-canalicular network [5]. On the other hand, an increase in the canalicular size might disrupt tethers believed to attach osteocytes to the canalicular wall, potentially reducing the mechanosensitivity of the osteocytes [6,7].