Ultrastructural observation on cells meeting the histological criteria for preosteoblasts--a study in the mouse tibial metaphysis.
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.
Narimatsu
Kaya
K
Niigata University School of Dentistry, Niigata, Japan.
Li
Minqi
M
de Freitas
Paulo Henrique Luiz
PH
Sultana
Sara
S
Ubaidus
Sobhan
S
Kojima
Taku
T
Zhucheng
Liu
L
Ying
Guo
G
Suzuki
Reiko
R
Yamamoto
Tsuneyuki
T
Oda
Kimimitsu
K
Amizuka
Norio
N
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
D050659:Core Binding Factor Alpha 1 Subunit; C493716:Runx2 protein, mouse; D000469:Alkaline Phosphatase; D001973:Bromodeoxyuridine