Osteogenesis in an in vitro coculture of human periodontal ligament fibroblasts and human microvascular endothelial cells

Background: Periodontal bone healing is a complex process involving many cells and processes that must function flawlessly for proper healing to occur. The exact progenitor cells that contribute to this process are not fully characterized. Periodontal fibroblasts and pericytes were postulated to be potential osteoprogenitor cells. This study describes a viable coculture model for the in vitro study of osteogenesis. Methods: Human microvascular endothelial cells (HMVEC) and human periodontal ligament (HPDL) fibroblasts were cocultured in a layered model and monitored for the development of runt-related transcription factor 2 (runx2) and desmin expression by real-time polymerase chain reaction. Conditions shown to be osteogenic (bone morphogenetic protein [BMP]-2 and enamel matrix derivative [EMD]) were compared to a control coculture that was unstimulated. Results: The HMVEC migrated into a layer of collagen containing only HPDL cells as monitored by fluorescent labeling. runx2 and desmin expressions were increased in stimulated cocultures in week 2 compared to controls. At week 3, the unstimulated control cocultures developed the expression of runx2 and desmin, and the cocultures that were stimulated with EMD and BMP-2 achieved significantly higher levels of these factors than any of the other conditions. Conclusions: Signs of osteogenesis werepresent inthecocultures in unstimulated and stimulated conditions. However, in the stimulated condition, osteogenicmarkerswere increased at earlier time points.As such, thismodelmay provide a goodmethod for the study of specific cellular processes thatmaylead to osteogenesis and eventually for understanding the regeneration of periodontal bone in vivo. J Periodontol 2010;81:139-149.