Effects of substrate strain and mechanical damage on osteocyte around implant

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Microdamage is naturally contained in bone and has been considered to trigger bone remodeling. Osteocytes, which exist in bone matrix forming 3-D cell-to-cell network, provide cellular basis to detect local mechanical environment neighboring the microdamage, and should be involved in the initiating mechanism of bone remodeling. This time we demonstrate the role of osteocytes in the initial phase of osteoclastogenesis around implant, osteocyte-like cell line MLO-Y4 cells were three-dimensionally cultured inside col- lagen gel and subjected to cyclic stretching like occlusal force.In vivo study, right maxillary first molars were extirpated from rats and implanted with 3 types of implants (non-load, reasonable-load, over loaded). At 1, 2 and 4 weeks after implantation, rats were sacrificed and undecalcified ground sections were fabricated. We examined microcracks around osteocytes by fluorescent stain and after that, the specimens were stained with the Villanueva Goldner stain and bone volume was calculated. As a results, every specimens showed new bone formation around implants, but these bone qualities were less mineralized bone. So osteocyte could not showed these observation period. In the future, we continue to examine bone remodeling around implant long period of observation.In vitro study, we established a loading apparatus in which osteocyte-like cell line MLO-Y4 cells were three-dimensionally cultured inside collagen gel and subjected to cyclic stretching in near occlusal force. According to the level of RANKL in mechanical group were significantly higher than those in the non-mechanical group. Our data suggested that when MLO-Y4cells are mechanically damaged, the membrane-bound forms of M-CSF and RANKL are released, and could thus act as a “targeting” signal to bone remodeling.