LL-37, a natural antimicrobial peptide, was tested on human dental pulp stem cells in the lab. At 5‑10 µg/mL it didn’t kill the cells, actually helped them survive a bit more, and at the higher dose pushed them toward becoming tooth‑building cells by raising a protein called DSPP.

This study evaluated the biocompatibility of 5 and 10 μg/mL LL-37 in vitro and its effect on the differentiation of human dental pulp stem cells (DPSCs) into odontoblast-like cells. Cell viability, genotoxicity, nitric oxide production, cell cycle, dentine sialophosphoprotein (DSPP) production, and DSPP gene expression. Concentrations of 5 and 10 μg/mL of LL-37 were not cytotoxic and generally increased cell viability, especially on the third day (P < .05). The tested concentrations did not induce genotoxicity (P < .05). LL-37 did not significantly alter nitrite production at either concentration. Cell cycle analysis revealed that 10 μg/mL of LL-37 arrested cells in G0/G1 (P < .05). The control group exhibited higher numbers of cells in other phases of the cell cycle (P < .05). The expression of the DSPP protein and gene was also higher in the 10 μg/mL of LL-37 group (P < .05). These results demonstrated that LL-37 was biocompatible at these concentrations and increased the number of viable cells, especially during the initial period. The 10 μg/mL concentration arrested the cell cycle and increased expression of the DSPP protein and gene, which indicates that this peptide contributes to odontoblastic differentiation.