Comparison of the osteoinductive potential of preconditioned dental pulp stem cell secretome versus their exosomes

This study aimed to compare the effects of osteogenically preconditioned dental pulp stem cells (DPSCs) secretome versus their exosomes on proliferation, migration, osteogenic differentiation, and mineralization of bone marrow stem cells (BMSCs). BMSCs and DPSCs were isolated and characterized. DPSCs were osteogenically preconditioned for 10 days before isolation of their derivatives. The study involved four groups: negative control (BMSCs in complete media), positive control (BMSCs in complete media with osteogenic supplement), secretome group (BMSCs co-cultured with DPSCs-secretome), and exosome group (BMSCs co-cultured with DPSCs-exosomes). BMSCs' viability through MTT assay and cell migration were evaluated. Mineralization was assessed through Alizarin red S and Von Kossa staining. RT-qPCR was performed for osteogenic gene expression, followed by statistical analysis. The exosome group showed the highest cell proliferation on day 5, but it did not reach statistical significance. Cell migration assay showed more rapid wound closure in the control group. However, after 24 h, the secretome group outperformed the exosome group, while the opposite results were observed after 48 h. The exosome group revealed the highest mineralization and osteogenic marker expressions, followed by the secretome, and finally the control groups, with significant differences between groups. Therefore, osteogenic preconditioning can be considered as an efficient tool for enhancing the osteoinductive influence of DPSCs-derivatives, promoting osteoblastic differentiation and mineralization, and under the tested conditions, exosomes demonstrated greater osteoinductive activity compared to secretome. However, osteogenically committed cells seem to lose their paracrine influence on cell viability and migration.