Bone morphogenetic protein 2-enhanced osteogenic differentiation of stem cell spheres by regulation of Runx2 expression

Bone morphogenetic protein 2 (BMP-2) is a growth factor that is used to induce osteogenic differentiation in stem cells. The present study assessed the effects of BMP-2 on stem cell spheroid morphology, viability and osteogenic differentiation. Stem cell spheres were constructed and treated with BMP-2 at predetermined concentrations (0-100 ng/ml) using concave microwells. Cell viability was qualitatively and quantitatively analyzed via microscopy and a water-soluble tetrazolium salt assay kit, respectively. Alkaline phosphatase activity was assessed and an anthraquinone dye for calcium deposit evaluation was performed to determine osteogenic differentiation. The expressions of (runt-related transcription factor 2) and collagen 1 were also determined via quantitative PCR. Spherical shapes were formed using concave microwells on day 1, which were maintained up to day 21. On day 1, the relative cell viability of 0, 10 and 100 ng/ml BMP-2 treated cells was 100.0±1.9, 97.3±4.4 and 101.3±2.6%, respectively. Significantly higher values for alkaline phosphatase activity were determined in the 100 ng/ml treated group when compared with the control group. Additionally, Runx2 mRNA levels were significantly higher in the 100 ng/ml BMP-2 group compared with the control group, as determined via quantitative PCR. The results of the present study indicated that BMP-2 enhanced the differentiation of stem cell spheres, which was demonstrated by increased alkaline phosphatase activity and Runx2 expression.