One of the most noteworthy characteristics of mesenchymal stem cells (MSCs) is their ability to differentiate into osteoblasts in vitro and in vivo. In vitro, this is easily achieved by culturing in the appropriate induction medium. It is because of the reliability and ease of this process that osteogenic differentiation has become a popular assay for the demonstration of MSC plasticity. Although the conditions required for inducing osteogenic differentiation by MSCs typically do not vary particularly between investigators, many methods are employed to measure the extent of differentiation. These methods include, but are not limited to, reverse transcriptase PCR (RT-PCR) for detection of osteogenic transcripts, enzyme linked immunosorbent assay (ELISA) for secreted protein markers, colorimetric assays for osteogenic enzymes, and direct staining of matrix components. This chapter reviews the protocols most commonly utilized for the evaluation of osteogenic differentiation for cultured MSCs.
