Influence of skeletal site of origin and donor age on osteoblastic cell growth and differentiation

Bone loss with aging may be due, at least in part, to inadequate bone forma tion. Moreover, the process of bone aging is known to follow a different pa ttern throughout the skeleton. In this study, we examined the cell prolifer ation rate (area under the cell growth curve, AUG) and the secretion of C-t erminal type I procollagen (PICP), alkaline phosphatase (ALP), and osteocal cin (OC) in primary cultures of osteoblastic cells from human trabecular bo ne. Osteoblastic cells were obtained for 168 donors (100 women and 68 men). Ninety-eight bone samples were obtained from subjects undergoing knee arth roplastia, 52 aged 50-70 years (64 +/- 5) and 46 over age 70 (73 +/- 2). An other 70 bone samples were obtained from subjects undergoing hip arthroplas tia; 51 were 50-70 years old (64 +/- 4) and 19 were over 70 (75 +/- 5). Ost eoblastic cells from the older donors had a lower proliferation rate and OC secretion than those from younger subjects. However, ALP secretion was hig her in the former subjects, whereas PICP secretion was unchanged. Osteoblas tic cells from hip had a lower proliferation rate than those from knee. PIC P secretion was also lower and ALP secretion was higher in the former cells . In age-matched cell cultures, osteoblastic cells from the knee had higher proliferation rate and PICP secretion than osteoblastic cells from the hip . However, ALP secretion was lower in knee osteoblastic cells than those fr om hip only in the younger group. With aging, ALP secretion was found to in crease in knee osteoblactic cells, whereas OC secretion decreased in osteob lastic cell cultures from the hip. Our findings suggest that bone loss with aging may be accounted for, at least in part, by a decreased osteoblastic cell proliferation and an increased osteoblastic maturation. In addition, o ur data indicate that these changes with aging do not occur similarly at di fferent skeletal sites.