Age, gender, and percentage of circulating osteoprogenitor (COP) cells: The COP Study

Abstract

Circulating osteoprogenitor (COP) cells are blood-borne cellswhich express a variety of osteoblasticmarkers and are able to formbone nodules in vivo.Whereas a high percentage of COP cells (%COP) is associatedwith vascular calcification, low %COP has been associated with disability and frailty. However, the reference range of %COP in age- and gender-matching populations, and the age-related changes in %COP remain unknown. A cross-sectional studywas undertaken in 144 healthy volunteers inWestern Sydney (20–90 year-old, 10male and 10 female subjects per decade). %COP was quantified by flow cytometry. A high inter-and intra-rater reliability was found. In average, in this healthy population average of %COP was 0.42. There was no significant difference in %COP among the age groups. Similarly, no significant difference was found in %COP with gender, weight, height or BMI. In addition, we identified a normal reference range of %COP of 0.1–3.8%. In conclusion, in addition to the identification of steady levels of COP cells with age, we also identified a normal reference range of %COP, which could be used in future studies looking at musculoskeletal diseases in older populations.