Different Methylation Patterns of RUNX2, OSX, DLX5 and BSP in Osteoblastic Differentiation of Mesenchymal Stem Cells

Runt-related transcription factor 2 (RUNX2) and osterix (OSX) as two specific osteoblast transcription factors and distal-less homeobox 5 (DLX5) as a non-specific one are of paramount importance in regulating osteoblast related genes including osteocalcin, bone sialoprotein (BSP), osteopontin and collagen type Iα1. The present study sets out to investigate whether epigenetic regulation of these genes is important in osteoblastic differentiation of mesenchymal stem cells (MSCs).

In this experimental study, MSCs were differentiated to osteoblasts under the influence of the osteogenic differentiation medium. DNA and RNA were extracted at days 0, 7, 14 and 21 from MSCs differentiating to osteoblasts. Promoter regions of RUNX2, OSX, DLX5 and BSP were analyzed by methylation-specific PCR (MSP). Gene expression was analyzed during osteoblastic differentiation by quantitative real-time polymerase chain reaction (PCR).

MSP analysis revealed that promoter methylation status did not change in RUNX2, DLX5 and BSP during MSC osteoblastic differentiation. In contrast, OSX promoter showed a dynamic change in methylation pattern. Moreover, RUNX2, OSX, DLX5 and BSP promoter regions showed three different methylation patterns during MSC differentiation. Gene expression analyses confirmed these results.

The results show that in differentiation of MSCs to osteoblasts, epigenetic regulation of OSX may play a leading role.