Matrix mineralization controls gene expression in osteoblasts

Osteoblasts are adherent cells. Under physiological conditions they attach to mineralized and non-mineralized osseous surfaces. However, how exactly osteoblasts respond to these different osseous surfaces is largely unknown. Our hypothesis was that the state of matrix mineralization provides a functional signal to osteoblasts. To assess the osteoblast response to mineralized compared to demineralized osseous surfaces, we assessed the transcriptom. Porcine tibia was cut into 16 slices with 600 µm thickness each. 8 slices were demineralized with 0,5 M EDTA over 16 hrs, while the other 8 slices were left in their native condition. All slices were sterilized over 16 hrs, using 2% PAA (peracedic acid, Bioxal SA, Chalon-sur-Saône, France). MG-63 cells were seeded onto the osseous surfaces (200,000/cm²), followed by incubation of the samples for 72 hrs (37 °C, 5% CO2). After incubation, the adhesive cells were mechanically removed using a cell scraper. For each surface (mineralized or demineralized), the 8 samples were randomly pooled in pairs, resulting in an n=4 per surface group. RNA was extracted in Trizol.