Number of osteoprogenitor cells in human bone marrow markedly decreases after skeletal maturation |
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Authors: | Saburo Nishida Naoto Endo Hiroshi Yamagiwa Tatsuhiko Tanizawa Hideaki E Takahashi |
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Institution: | (1) Department of Orthopaedic Surgery, Niigata University School of Medicine, 1 Asahimachi-dori, Niigata 951-8510, Japan, JP |
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Abstract: | Pluripotent mesenchymal stem cells in bone marrow differentiate to osteoblast progenitor cells. When the bone marrow cells
are cultured in vitro, they form colony-forming units-fibroblastic (CFU-Fs) with exhibiting osteoblastic features such as
expression of alkaline phosphatase (ALP) and formation of calcified nodules ex vivo. This article describes the effect of
growth, maturation, and aging of the skeleton on human CFU-Fs harvested from human iliac bone marrow. Human bone marrow cells
were harvested from the ilia of 49 women, and were cultured ex vivo for examination. The 49 subjects ranged in age from 4
to 88 years and were without metabolic bone disease. These aspirated bone marrow cells from human ilium exhibited osteoblastic
phenotype such as alkaline phosphatase (ALP) activity, expression of osteocalcin (OSC) and parathyroid hormone-receptor (PTH-R)
mRNA, and the formation of calcified nodules in vitro. The number of ALP-positive CFU-Fs and the ALP activity were quantified.
The highest levels of ALP-positive CFU-Fs were observed in the young group, particularly in those under 10 years of age. The
levels of ALP-positive CFU-Fs declined sharply after 10 years of age; those above 20 years of age exhibited a lower number
of ALP-positive CFU-Fs, with a gradual decline with increasing age. These results indicate that change in the number of ALP-positive
CFU-Fs may be associated with skeletal growth and maturation. The results also show that osteoblastic features such as ALP
activity and capability of formation of calcification nodules were maintained even in the older subjects. These findings suggest
that decreased activity of bone formation in the aged subjects could be, in part, caused by the decreased number of osteoprogenitor
cells differentiating into osteoblasts because the number of ALP-positive CFU-Fs was one of the indices exhibiting bone-forming
activity in the human marrow stromal cells.
Received: July 24, 1998 / Accepted: Dec. 28, 1998 |
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Keywords: | : osteoprogenitor cells colony-forming units-fibroblastic (CFU-F) bone marrow skeletal maturation |
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