Type I collagen‐induced osteoblastic differentiation of bone‐marrow cells mediated by collagen‐α2β1 integrin interaction

Bone marrow cells are multipotent cells. When bone marrow cells were cultured with type I collagen matrix gels, they showed high alkaline phosphatase activity, collagen synthesis, and formed mineralized tissues. Furthermore, cells expressed osteocalcin and bone sialoprotein genes, which are osteoblast-specific genes. These findings indicate that type I collagen matrix gels induce osteoblastic differentiation of bone marrow cells. Type I collagen interacts with the α 2 β 1 integrin receptor on the cell membrane and mediates extracellular signals into cells. DGEA peptide is a cell-binding domain of type I collagen molecule. When collagen–integrin interaction was interrupted by the addition of Asp-Gly-Glu-Ala (DGEA) peptide to the culture, the expression of osteoblastic phenotypes of bone marrow cells was inhibited. Furthermore, anti-α 2 integrin antibody, which interacts with α subunit of integrin and blocks the binding of integrin with collagen, suppressed the expression of osteoblastic phenotypes. These findings imply that collagen-α 2 β 1 integrin interaction is an important signal for the osteoblastic differentiation of bone marrow cells. J. Cell. Physiol. 184:207–213, 2000. © 2000 Wiley-Liss, Inc.