Aging of human trabecular osteoblasts in culture.

Osteoblasts are the bone forming cells, which synthesize and secrete the components of the bone matrix. An imbalance between the breakdown and the build up of bone and a decline in osteoblast activity is considered to be the basis of age-related changes in bone structure and function, including the origin of osteoporosis. In order to determine whether the osteoblast activity decreases because of a decreased proliferative capacity or some other reason, we have examined several cellular and biochemical characteristics of human trabecular osteoblasts serially passaged in culture. We have studied growth and maximum lifespan in terms of cumulative population doubling level achieved in culture. We have also determined changes in morphology, protein content and the synthesis of proteins, DNA and RNA during aging of osteoblasts. Furthermore, changes in the cytoskeletal components actin and microtubuli have been observed along with a comparison of one dimensional and two dimensional gel electrophoretic protein pattern during aging.