SMOC1-induced osteoblast differentiation involves enhanced proliferation of human bone marrow mesenchymal stem cells

SPARC related modular calcium binding 1 (SMOC1) has been implicated in the regulation of the osteoblast differentiation of human bone marrow mesenchymal stem cells (BMSCs); however, it is not clear how it regulates this process. In this study, we analyzed molecular networks during the SMOC1-induced osteoblast differentiation of BMSCs. SMOC1 overexpression induced the deposition of minerals and the expression of osteoblast marker genes. During osteoblast differentiation induced by SMOC1 overexpression, gene profiling was performed using an Affymetrix GeneChip. The expression of 191 genes was increased by SMOC1 overexpression, and these genes were classified into 17 groups based on gene ontology: developmental process (23%), cellular component organization (23%), cell death (10.5%), cell cycle (9.9%), cell adhesion (7.9%), and cytoskeleton organization (5.2%). Protein interaction analysis also showed the strong interaction of proteins involved in development, cell death, and cell cycle. Consistently, proliferation of BMSCs overexpressing SMOC1 was significantly increased compared to BMSCs expressing the control vector. These results suggest that SMOC1 induces the osteoblast differentiation of BMSCs by inducing the expression of an array of genes involved in cell growth and development.