Effects of Octacalcium Phosphate on the Development of Bone Marrow Derived Stromal Cells: Comparison of Osteogenic Medium/OCP Induced Osteocalcin Expression
According to the gene repertoire, distinct morphology and the organisation of extracellular matrix, osteoblast development was identified as a series of stages, proliferation, differentiation, matrix deposition, matrix maturation and mineralization. Each of these stages required tightly regulated and functionally coupled expression of genes related to the transcription factors and bone matrix. In this paper, we identify the effects of OCP to the differentiation of osteoblasts from the point of view of differentiation sequence development. Osteogenic medium (Ost MEM) mainly regulated the osteocalcin (OC) mRNA expression in the first week of culture. As culture continued to 24 days, OCP crystal assemblies became the main regulator. This shift in the role that OCP and Ost MEM played in regulation may reflect different biological functions of OC in Ost MEM induced regulation and OCP crystals induced regulation. The up-regulated OC mRNA expression by OCP crystal assemblies may function as a signal to coordinate the activities of osteoblasts and osteoclasts instead of inducing mineralisation at the end of the differentiation sequence of osteoblasts. By comparing the modified expression pattern observed on the OCP crystal particles with the patterns of differentiation sequences, it was found that BMSCs colonising OCP crystal assemblies from day 7 to day 24 matched the process of differentiation in the early stages of matrix deposition. The gene expressions of BMSC cultured in the osteogenic medium (positive control) corresponded with the process from matrix deposition to mineralisation. Hence, the differentiation process of BMSCs on OCP crystal assemblies was different from that found on the positive control. BMSCs could differentiate to osteoblasts that would function as a regulator for osteoclast activities.
Guy Daculsi and Pierre Layrolle
Y. Liu et al., "Effects of Octacalcium Phosphate on the Development of Bone Marrow Derived Stromal Cells: Comparison of Osteogenic Medium/OCP Induced Osteocalcin Expression", Key Engineering Materials, Vols. 361-363, pp. 1009-1012, 2008