Tensile mechanical strain up-regulates Runx2 and osteogenic factor expression in human periosteal cells: Implications for distraction osteogenesis

Purpose: Distraction osteogenesis is now accepted as a standard treatment in oral and maxillofacial reconstructive surgery. In the process of bone regeneration with the application of strain, the periosteum might be very involved in osteogenesis. This study examined the effect of mechanical strain on periosteal cells and the implications for distraction osteogenesis. Materials and Methods: Periosteal cells were obtained from mandibular periosteum that was excised while extracting impacted wisdom teeth. Mechanical strain was applied using a specially designed apparatus with flexible silicon bottom chambers. The levels of mRNA of the osteoblast differentiation factor Runx2 (Cbfa1/AML3/PebαA) and osteogenic factors were analyzed at different times using the reverse transcription-polymerase chain reaction method to evaluate the effect of the strain. Results: The periosteal cells expressed the osteogenic phenotype. The strain had a shaping effect on the cells. The application of tensile strain strongly activated the expression of osteogenic and angiogenic growth factors, and up-regulated the expression of Runx2, an osteoblast-specific transcription factor. Conclusion: Tensile strain may initiate the differentiation of periosteal cells into osteogenic cells, inducing the expression of Runx2 in the process of bone regeneration. Therefore, the periosteum is profoundly involved in bone formation and regeneration, especially in distraction osteogenesis.