title: Ultrastructural observation on cells meeting the histological criteria for preosteoblasts--a study in the mouse tibial metaphysis.
abstract: Preosteoblasts are currently defined as the precursors of mature osteoblasts. These cells are morphologically diverse and may represent a continuum during osteoblast differentiation. We have attempted to categorize the different preosteoblastic phenotypes in vivo by examining bone cells expressing the runt-related transcription factor 2, alkaline phosphatase and BrdU incorporation - histological traits of a preosteoblast - under transmission electron microscopy (TEM). TEM observations demonstrated, at least, in part two preosteoblastic subtypes: (i) a cell rich in cisterns of rough endoplasmic reticulum (rER) with vesicles and vacuoles and (ii) a subtype featuring extended cytoplasmic processes that connect with distant cells, with a small amount of scattered cisterns of rER and with many vesicles and vacuoles. ER-rich cells, whose cellular machinery is similar to that of an osteoblast, were often seen adjacent to mature osteoblasts, and therefore, may be ready for terminal differentiation. In contrast, ER-poor and vesicle-rich cells extended their cytoplasmic processes to mature osteoblasts and, frequently, to bone-resorbing osteoclasts. The abundant vesicles and vacuoles identified in this cell type indicate that this cell is involved in vesicular transport rather than matrix synthesis activity. In summary, our study verified the morphological diversity and the ultrastructural properties of osteoblastic cells in vivo.
authors.affiliation: Niigata University School of Dentistry, Niigata, Japan.
authors.forename: Kaya
authors.initials: K
authors.lastname: Narimatsu
authors.forename: Minqi
authors.initials: M
authors.lastname: Li
authors.forename: Paulo Henrique Luiz
authors.initials: PH
authors.lastname: de Freitas
authors.forename: Sara
authors.initials: S
authors.lastname: Sultana
authors.forename: Sobhan
authors.initials: S
authors.lastname: Ubaidus
authors.forename: Taku
authors.initials: T
authors.lastname: Kojima
authors.forename: Liu
authors.initials: L
authors.lastname: Zhucheng
authors.forename: Guo
authors.initials: G
authors.lastname: Ying
authors.forename: Reiko
authors.initials: R
authors.lastname: Suzuki
authors.forename: Tsuneyuki
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Kimimitsu
authors.initials: K
authors.lastname: Oda
authors.forename: Norio
authors.initials: N
authors.lastname: Amizuka
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D002454:Cell Differentiation; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D046529:Microscopy, Electron, Transmission; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure*; D010012:Osteogenesis; D010641:Phenotype; D013977:Tibia / Q000166:cytology* / Q000254:growth & development
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; C493716:Runx2 protein, mouse; D000469:Alkaline Phosphatase; D001973:Bromodeoxyuridine