Localization of Bmi1 in osteoblast-lineage cells during endochondral ossification
Localization of Bmi1 in osteoblast-lineage cells during endochondral ossification
复制标题
软骨内骨化过程中 Bmi1 在成骨细胞谱系细胞中的定位
作者：
Takebe H;Irie K;Hosoya A
Bmi1由B细胞特异性Moloney鼠白血病病毒整合位点1编码，是定位于干细胞和未分化细胞的多梳状蛋白质组的一部分。它调节各种分化基因的表达。然而，Bmi1对骨骼发育的调控机制仍然知之甚少。在本研究中，我们旨在观察Bmi1在大鼠骨发育和骨折愈合的软骨内成骨过程中的分布。Bmi1在胚胎第14天的间充质细胞聚集区和胚胎16d的软骨原基中心周围的细胞中检测到Bmi1的免疫反应。随后，在软骨原基周围形成钙化的骨基质，表达Runt相关转录因子2(Runx2)和Osterix(OSX)的成骨细胞表达Bmi1。骨折后4 ，骨折周围结缔组织内可见Bmi1阳性细胞。在骨折后42 天，新生骨表面的成骨细胞呈Bmi1、Runx2和Osx阳性反应，但Bmi1免疫反应弱于Runx2和Osx。综上所述，Bmi1基因定位于成骨细胞系细胞的早期分化阶段，并可能在软骨内成骨过程中调节其分化。
Encoded by B cell–specific moloney murine leukemia virus integration site 1, Bmi1 is part of the polycomb group of proteins localized in stem and undifferentiated cells. It regulates the expression of various differentiation genes. However, the regulatory mechanism of skeletal development by Bmi1 remains poorly understood. In this study, we aimed to observe Bmi1 distribution during endochondral ossification processes in rat bone development and fracture healing. Immunoreactivity of Bmi1 was detected in the mesenchymal cell aggregation area at embryonic day (E) 14 and in cells around the center of cartilage primordium at E 16. Subsequently, the calcified bone matrix was formed around the cartilage primordium, and osteoblasts expressing Runt‐related transcription factor 2 (Runx2) and Osterix (Osx) showed immunopositivity for Bmi1. At 4 days after bone fracture, the connective tissue around the fractured bone contained Bmi1‐positive cells. At 42 days after fracture, osteoblasts along the surface of the new bone revealed Bmi1‐, Runx2‐ and Osx‐positive reactions, but the Bmi1 immunoreactivity in osteocytes was less than the Runx2 and Osx immunoreactivities. In conclusion, Bmi1 is localized in the osteoblast‐lineage cells in their early differentiation stages, and it might regulate their differentiation during endochondral ossification.