BONE-RELATED MATRIX PROTEINS EXPRESSION IN-VITRO AND IN-VIVO BY MARROW STROMAL CELL-LINE

MBA-1, a bone marrow stroma-derived cell line, was transplanted in an ectopic site and formed endochondral bone. The ossicle developed throu gh stages of cell proliferation, differentiated into a zone of hypertr ophy and formed a chondroid-like area which further developed to prima ry mineralized bone. We explored the expression of various matrix prot eins by MBA-1 cells in vitro and in the ossicle formed in vivo. MBA-I cells constitutively expressed mRNAs encoding for collagen I, non-coll agenous proteins and alkaline phosphatase. RNA extracted from the ossi cle formed by these cells was expressed in a different pattern. The in vivo maturation of MBA-I cells was accompanied by low expression of m RNA for procollagen alpha(2)(I) and a marked increase in osteonectin a nd osteopontin mRNA levels. Thus, the ability to follow expression of these genes through bone formation in vivo has been demonstrated.