Effect of PRF, PPP, and DMEM media on mineralization behavior of periodontal progenitor populations. (a), (c), (e), and (g) are alkaline phosphatase staining assays and (b), (d), (f), and (h) are alizarin red S mineralization assays. In (a)–(f), alkaline phosphatase ((a), (c), and (e)) or alizarin red ((b), (d), and (f)) staining in periodontal progenitor cells cultured for 7, 14, and 21 days were compared. Different coculture conditions (PRF, PPP, OM, and DMEM) are distinguished by different bar patterns which are identified in the bar legend above (b). The three periodontal progenitor populations compared in this study, dental follicle (DF), periodontal ligament (PDL), and alveolar bone (AB) are labeled on the x-axis of the graphs in (a)–(f). (g) and (h) illustrate the differences in mineralization behavior between alveolar bone progenitors cocultured with PRF, OM, PPP, and DMEM for 14 days; (g) is a photograph of the alkaline phosphate-stained 6-well plate and (h) is a photograph of the alizarin red-stained 6-well plate. Level of significance was calculated in comparison to the DMEM-treated cells within each group. *P < 0.05, **P < 0.01, and ***P < 0.001.