Osteoblast-related gene expression of bone marrow cells during the osteoblastic differentiation induced by type I collagen

Bone marrow contains multipotent cells that differentiate into fibroblasts, adipocytes, and osteoblasts, Recently we found that type I collagen matrix induced the osteoblastic differentiation of bone marrow cells. Three weeks after cells were cultured with type I collagen, they formed mineralized ti ssues. In this study, we investigated the expression of osteoblast-related genes (alkaline phosphatase, osteocalcin, bone sialoprotein, osteopontin, a nd cbfa-1) during the osteoblastic differentiation. The expression of alkal ine phosphatase and osteopontin genes increased time-dependently during the osteoblastic differentiation. Osteocalcin and bone sialoprotein genes were expressed in cells that formed mineralized tissues, and both were expresse d only after cells reached the mineralized tissue-formation stage, On the o ther hand, the cbfa-1 gene was expressed from the early differentiation sta ge, The Asp-Gly-Glu-Ala (DGEA) amino acid domain of type I collagen interac ts with the alpha2 beta1 integrin receptor on the cell membrane and mediate s extracellular signals into cells. When the collagen-integrin interaction was interrupted by the addition of DGEA peptide to the culture, the express ion of osteoblastic phenotypes of bone marrow cells was inhibited. These fi ndings imply that the collagen-alpha2 beta1 integrin interaction is an impo rtant signal for the osteoblastic differentiation of bone marrow cells.