Osteogenic differentiation of mouse embryonic stem cells: differential gene expression analysis by cDNA microarray and purification of osteoblasts by cadherin-11 magnetically activated cell sorting.

We have previously shown osteogenic differentiation of mouse embryonic stem (ES) cells and temporal enrichment with osteoblastic cells, by stimulation with serum-containing culture medium supplemented with beta-glycerophosphate, ascorbate, and dexamethasone. In our present study we have used similar culture conditions to further investigate osteogenic differentiation of mouse ES cells. Using reverse transcription-polymerase chain reaction (RT-PCR) we demonstrated the expression of genes associated with osteoblast differentiation including the bone matrix protein osteocalcin and the transcription factor Cbfa-1/runx2. Furthermore, results of cDNA microarray analysis, and subsequent RT-PCR analysis of differentiating ES cells after exposure to osteogenic stimuli, revealed a combination of upregulation of genes involved in osteoblast differentiation including osteopontin, HSP-47, and IGF-II coupled with downregulation of genes involved in differentiation of other phenotypes such as the neuroectoderm factor Stra-13. Finally, we have applied magnetically activated cell-sorting methods to ES cell cultures treated with osteogenic stimuli and, using an antibody to cadherin-11, have purified a subpopulation of cells with osteoblastic characteristics.