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 through stages of cell proliferation, differentiated into a zone of hypertrophy and formed a chondroid-like area which further developed to primary mineralized bone. We explored the expression of various matrix proteins by MBA-1 cells in vitro and in the ossicle formed in vivo. MBA-I cells constitutively expressed mRNAs encoding for collagen I, non-collagenous proteins and alkaline phosphatase. RNA extracted from the ossicle formed by these cells was expressed in a different pattern. The in vivo maturation of MBA-I cells was accompanied by low expression of mRNA for procollagen alpha(2)(I) and a marked increase in osteonectin and osteopontin mRNA levels. Thus, the ability to follow expression of these genes through bone formation in vivo has been demonstrated.