Critical Reviews in Oral Biology & Medicine, Vol 3, 269-305, Copyright © 1992 by International & American Associations for Dental Research
Concepts of osteoblast growth and differentiation: basis for modulation of bone cell development and tissue formation
J. B. Lian and G. S. Stein
Department of Cell Biology, University of Massachusetts Medical Center, Worcester 01655.
The combined application of molecular, biochemical, histochemical, and
ultrastructural approaches has defined a temporal sequence of gene
expression associated with development of the bone cell phenotype in
primary osteoblast cultures. The peak levels of expressed genes reflect a
developmental sequence of bone cell differentiation characterized by three
principal periods: proliferation, extracellular matrix maturation and
mineralization, and two restriction points to which the cells can progress
but cannot pass without further signals. The regulation of cell growth and
bone-specific gene expression has been examined during this developmental
sequence and is discussed within the context of several unique concepts.
These are (1) that oncogene expression in proliferating osteoblasts
contributes to the suppression of genes expressed postproliferatively, (2)
that hormone modulation of a gene is dependent upon the maturational state
of the osteoblast, and (3) that chromatin structure and the presence of
nucleosomes contribute to three-dimensional organization of gene promoters
that support synergistic and/or antagonistic activities of physiologic
mediators of bone cell growth and differentiation.
