The Effect of Aging on the Differentiation of Rat Osteoblast-like Cells in vitro

The osteogenic capability of cells derived from the bone marrow of young (4 week old) or adult (10 month old) male Wistar rats was investigated in vitro. The proliferation ratio of osteogenic cells from the young and adult animals increased until 9 days of culture, and then rapidly decreased. Alkaline phosphatase (ALP) activity in both types of cells increased in intensity from 5 days and peaked at 11 days, and ALP activity in the young cells was significantly higher than in the adult cells at all time periods. Calcified nodules were first detected after 7 days in both types of cells. The Ca/P ratio of calcified nodules increased until 13 days in both types of cells, and was significantly higher in the young cells than that in the adult cells at all time periods, except at 7 days. Connexin 43-immunoreactive spots were detected at cell-to-cell junctions at early times in the young cells, but in the adult cells, only a few connexin 43 immunoreactive spots were observed at early times, and these gradually increased at later times. These results suggest that cells derived from the bone marrow of young rats differentiate into osteogenic cells and synthesize calcified nodules at earlier time periods in vitro compared with cells derived from adult rats.