Conditioned media from differentiating craniofacial bone marrow stromal cells influence mineralization and proliferation in periodontal ligament stem cells.

Previous reports have mainly focused on the behavioral responses of human periodontal ligament stem cells (hPDLSCs) in interaction with tibia bone marrow stromal cells (BMSCs). However, there is little study on the biologic features of hPDLSCs under the induction of maxilla BMSCs (M-BMSCs) at different phases of osteogenic differentiation. We hypothesized that M-BMSCs undergoing osteogenic differentiation acted on the proliferation, differentiation, and bone-forming capacity of hPDLSCs. In this paper, primary hPDLSCs and human M-BMSCs (hM-BMSCs) were expanded in vitro. After screening of surface markers for characterization, hPDLSCs were cocultured with different phases of differentiating hM-BMSCs. Cell proliferation and alkaline phosphatase activity were examined, and mineralization-associated markers such as osteocalcin and runt-related transcription factor 2 of hPDLSCs in coculture with uninduced/osteoinduced hM-BMSCs were evaluated. hPDLSCs in hM-BMSCs-conditioned medium (hM-BMSCs-CM) group showed a reduction in proliferation compared with untreated hPDLSCs, while osteoinduced hM-BMSCs for 10 day-conditioned medium (hM-BMSCs-CM-10ds) and osteoinduced hM-BMSCs for 15 day-conditioned medium (hM-BMSCs-CM-15ds) enhance the proliferation of hPDLSCs. hM-BMSCs of separate differentiation stages temporarily inhibited osteogenesis of hPDLSCs in the early days. Upon extending time periods, uninduced/osteoinduced hM-BMSCs markedly enhanced osteogenesis of hPDLSCs to different degrees. The transplantation results showed hM-BMSCs-CM-15ds treatment promoted tissue regeneration to generate cementum/periodontal ligament-like structure characterized by hard-tissue formation. This research supported the notion that hM-BMSCs triggered osteogenesis of hPDLSCs suggesting important implications for periodontal engineering.