Chemoattractive potential of stem cells from apical papilla in peripheral blood monocytes: an in vitro study

Chemokine (CC-motif) ligand 2 (CCL2) is the primary chemokine involved in monocyte migration from peripheral blood to tissues. These cells, in turn, will differentiate into macrophages and osteoclasts. Given that apical papilla stem cells (SCAP) are an important source of CCL2, this study aimed to investigate whether SCAP culture supernatant can recruit monocytes in vitro via CCL2. SCAP-conditioned medium (CM-SCAP) was obtained through primary culture after confirming the osteo/odontogenic differentiation potential of these cells. The supernatant was analyzed for CCL2 using an immunoenzymatic assay. Monocytes were isolated from human peripheral blood and positively selected using magnetic beads. CD 14+ cells were seeded into 5-μm pore transwell inserts placed in wells containing CM-SCAP. After 24 hours, the insert was removed, and the migrated cells were quantified using the Alamar Blue viability assay. Recombinant human CCL2 was used as a positive control, while the proliferation medium only was used as the negative control. CM-SCAP in the presence of a CCL2 neutralizer antibody was also tested. Statistical analysis was performed to assess group differences, considering data normality and a 5% significance level (p < 0.05). SCAP produced CCL2 in vitro, and none of the CM-SCAP dilutions affected monocyte viability. Wells containing CM-SCAP displayed a significant increase in cell migration compared to the control. This finding was abrogated by the CCL2 neutralizing antibody. Therefore, SCAP supernatant can induce monocyte migration in vitro through a CCL2-dependent mechanism.