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.