The bone remodeling process called osteoblasts has an important role in bone formation working together with
osteoclasts of which the cells are responsible for bone resorption. In addition, these bone turnover markers are used to
follow-up the conditions of bone remodeling in the patients. Recently, osteoblastic lineage cells have been found that they exist
in the human peripheral blood. However, there has been no report about the amount of circulating osteoblastic lineage cells
that have the relationship with the samples of bone turnover markers showing the bone remodeling condition. In the present
study, circulating osteoblasts were quantified in 43 subjects aged between 25-90 years. They were classified by age into 3
groups: A) lower than 60 years old (n = 9), B) from 60 to 79 years old (n = 22) and C) equal and over 80 years old (n = 12).
All were studied by the flow cytometry method using an antibody to osteocalcin and bone turnover markers β-CrossLab
(βCTx), PINP and NMID. These markers including parathyroid hormone were analyzed. The result showed the best positive
correlation between the percentage of circulating osteoblasts and bone turnover markers of the equal and over 80-year-old
group. While another result exhibited the negative correlation of circulating osteocalcin positive cells with the bone turnover
markers in the group of lower than 60 years old. As circulating osteoblasts had the correlation with bone turnover markers
in the group aged > 80 years old, this could be used as the markers to follow up the bone turnover situation of the patients in
this age group. However, this is a pilot study. Further analysis of more amounts of subjects should be done for a better result.

Keywords: Circulating-osteoblast, Circulating-osteocalcin-positive cell, Bone remodeling, Bone marker, bCTx, Flow cytometry
analysis