open access

https://doi.org/10.14943/doctoral.k13474

https://hdl.handle.net/2115/77060

podoplanin陽性骨芽細胞および骨細胞における組織化学的検索

英語

CD44

2019-03-25

Hokkaido University

23p

Osteoblastic differentiation into osteocytes is regulated in a temporospatial manner. It is difficult to identify which of osteoblasts are at the verge of differentiating into osteocytes; however, podoplanin reportedly localizes to osteoblasts/osteocytes at the verge of differentiating or right after embedding in the bone matrix. In this study, therefore, we attempted to examine the biological function of podoplanin for osteoblastic differentiation into osteocytes. Podoplanin-reactive osteoblasts show dynamic rearrangement of actin filament distribution and show their assembly along the cell membranes and the basal region of the cytoplasmic processes, whereas osteoblasts with little podoplanin immunoreactivity revealed well-developed stress fibers inside the cells. In the metaphysis (the bone remodeling area), CD44-positive osteoclasts were close to or in contact with podoplanin-reactive osteoblasts showing immunoreactivity of phosphorylated ezrin, an ERM family member associated with actin filament arrangement. Therefore, CD44-positive osteoclasts may participate in the differentiation of podoplanin-positive/phosphorylated ezrin-reactive osteoblasts into osteocytes. Immunoblotting analysis using calvariae from neonatal mice demonstrated increased phosphorylated ezrin when exogenous CD44 was administered. On the endosteal surfaces of cortical bones (a modeling area), bone podoplanin-positive osteoblasts were uniformly localized at certain intervals. Although there was no contact with CD44-positive cells, several osteoblasts showed the immunoreactivities of podoplanin and phosphorylated ezrin. Therefore, unlike femoral trabecules, molecules other than CD44 may transduce the podoplanin/EMR family signaling in preparation for osteocytic differentiation in the cortical bone. Taken together, the interplay between podoplanin and CD44 appears to be, at least in part, associated with ezrin phosphorylation and the subsequent actin rearrangement as well as the facilitation of osteoblastic differentiation into osteocytes in metaphyseal trabecules; however, it does not seem to be associated with the cortical bone.

2019-03-25

甲第13474号

博士(歯学)

(主査) 教授 横山 敦郎, 教授 網塚 憲生, 教授 土門 卓文, 助教 長谷川 智香

歯学研究科(口腔医学専攻)

博士論文

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