Abstract
We previously reported that spheroids containing three-dimensional proliferative cells may be useful for periodontal tissue regeneration. The aim of this study was to observe the changes of human alveolar bone periosteal cells (HABPCs) in spheroids using ultrastructural and immunohistochemical techniques. HABPCs were suspended at a cell density of 1.8 X 104 cells/cm2 in a 100-mm culture dish. After 10 daysʼ culture, the cells formed spheroids, which were digested by 0.25% trypsin, and centrifuged at 300 g for 3 min. Furthermore, the spheroids were matured for 1, 3, 7 and 14 days by immersion in a 24-well culture dish. The spheroids were examined at 1 day after formation by transmission electron microscopy, which revealed that the HABPCs were scattered in the whole spheroid. Specimens of spheroids were divided into three zones by the cell localization, namely, surface, middle and central zones, at 3 days. The number of cells in the central zone was decreased on day 7.In the middle zone on day 14 cells were found at a low density, with numerous collagen fibers observed in the wide intercellular spaces. When the spheroids were cultured for a prolonged period , the collagen synthesis started in the central zone of the spheroids, and gradually moved to the surface zone of the spheroids. An increase in the number of dense granules in the cells was observed. Furthermore, a similar degree of increase of both Osteopontin (OP)- and Osteocalcin (OC)- immunoreactive cells was noted. The results suggested that the cells in the spheroids had the potential for differentiation direction in the spheroids from central to surface zone. And the possibility of bone regeneration following transplantation of HABPC spheroids based on their ability to express OP and OC in alveolar bone. Nihon Shishubyo Gakkai Kaishi(J Jpn Soc Periodontol)54(2):155-166,2012.
