Abstract
Marrow stroma cells (MSC) play a major role in osteogenesis. The potential of the MSC to differentiate to boneโforming cells relies upon molecular regulation. This study analyzed MBAโ15 cells for the expression of genes and proteins that are key regulators of osteoblast differentiation. These cells express Cbfa1 and cโfos transcription factors (TF) of osteoprogenitor proliferating cells. RTโPCR and immunohistochemistry were used to demonstrate the message and protein expression of extracellular matrix proteins that are a prerequisite for matrix formation and mineralization, including alkaline phosphatase (ALP), osteocalcin, osteopontin, biglycan, and bone sialoprotein (BSP). The activity of ALP was correlated at various cell densities with coโexpression of osteocalcin or osteopontin. Adhering cells must attach to the appropriate matrix to enable survival and differentiation. Using attachment assays, we demonstrated that MBAโ15 cells adhered to collagenous matrix and the effect on survival measured by changes in intracellular calcium (Ca) levels. The cells' adhesion to matrix is mediated via cell surface molecules. We quantified the expression of cells surface molecules that are important players in mediating cellโmatrix interaction. Flow cytometry analysis (FACS) was used to determine the expression of CDโ31 (36%), and lower levels were identified for CDโ62E and CD11b. In summary, the present study demonstrates the expression of molecular markers that are distinctive for the osteoblastic phenotype in MBAโ15 marrow stroma cells and have crucial role in cellโmatrix interaction, in establishing the cellular osteogenic phenotype and their survival. ยฉ 2005 WileyโLiss, Inc.