Early osteocyte response to bone resorption stimuli

ABSTRACT

Over the last decade, increasing attention has been focused on the role of the osteocyte in bone remodeling, in view of its demonstrated ability to respond to mechanical and electric stimuli applied to bone. A previous [quot ]in vivo[quot ] study performed at our laboratory demonstrated that the application of orthodontic forces results in osteocytic lacunae enlargement. To our knowledge there are no data on cell and lacunae response to an inflammatory stimulus in the literature. The aim of this work was to determine whether osteocyte response to an inflammatory stimulus is comparable to that observed under mechanical stress and whether the ensuing cellular changes involve changes in the shape of the osteocyte and/or its lacunae. Three groups of ten male Wistar rats each, 200 to 250 g body weight, were used. Group I served as control. A cotton thread cervical ligature was placed around the first upper molars of animals in Group II, and those in Group III were fitted with an orthodontic appliance designed to exert a force toward palatine. All the animals were killed 24 hours after applying the stimuli. The histomorphometric determinations were measured on the interradicular crest between the two distal roots of the first upper molars. Osteocyte and lacunar volumes were measured and lacunar shape was analyzed. Group II exhibited a dense inflammatory infiltrate and slight resorption of the crest. Group III showed slight resorption of the vestibular wall. The lacunar volume increased in both experimental groups as compared to controls. The cell volume to lacunar volume decreased. These results suggest that osteocytes respond to inflammatory as well as to mechanical stimuli of bone resorption, enlarging lacunae without changes in cell volume.