Division of Histology, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Tobetsu-cho, Ishikari-gun, Hokkaido, Japan.
Division of Anatomy, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Tobetsu-cho, Ishikari-gun, Hokkaido, Japan.
Anat Rec (Hoboken). 2022 May;305(5):1112-1118. doi: 10.1002/ar.24693. Epub 2021 Jun 12.
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.
编码由 B 细胞特异性莫洛尼鼠白血病病毒整合位点 1，Bmi1 是多梳蛋白组的一部分，位于干细胞和未分化细胞中。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知之甚少。在这项研究中，我们旨在观察 Bmi1 在大鼠骨骼发育和骨折愈合过程中的软骨内骨化过程中的分布。在胚胎第 14 天（E）和第 16 天的软骨原基中心周围的细胞中，检测到 Bmi1 的免疫反应性。随后，在软骨原基周围形成了钙化的骨基质，表达 runt 相关转录因子 2（Runx2）和骨形成蛋白（Osx）的成骨细胞显示出 Bmi1 的免疫阳性。在骨骨折后 4 天，骨折周围的结缔组织含有 Bmi1 阳性细胞。在骨折后 42 天，新骨表面的成骨细胞显示 Bmi1、Runx2 和 Osx 的阳性反应，但成骨细胞中的 Bmi1 免疫反应性低于 Runx2 和 Osx 免疫反应性。总之，Bmi1 定位于成骨细胞系细胞的早期分化阶段，可能调节它们在软骨内骨化过程中的分化。
