Comparative Analysis of Amelogenin-Derived Peptides LRAP and SP on Osteogenic Differentiation of Human Dental Pulp and Bone Marrow-Derived Stem Cells

Background/Objectives: This study aimed to compare the biological effects of two amelogenin-derived peptides—the leucine-rich amelogenin peptide (LRAP) and a synthetic peptide (SP)—on human dental pulp stem cells (hDPSCs) and human bone marrow–derived mesenchymal stem cells (hBMSCs). The investigation focused on cell viability, osteogenic differentiation, mineralization, gene expression, and β-catenin expression. Methods: hDPSCs and hBMSCs were cultured in osteogenic medium and treated with LRAP and SP at 1, 5, 10, 50, and 100 ng/mL. Cytotoxicity was assessed by MTT assay, while osteogenic differentiation was evaluated by alkaline phosphatase (ALP) activity and Alizarin Red S staining. Gene expression of RUNX2, COL1A1, OCN, MEPE, and DMP1 was quantified by qPCR. β-catenin localization was analyzed by immunofluorescence. Statistical analysis was performed using one-way ANOVA with Tukey’s post hoc test (p < 0.05). Results: Both peptides exhibited good biocompatibility with hBMSCs, while high concentrations (≥50 ng/mL) reduced hDPSC viability. In both cell types, LRAP and SP increased ALP activity and mineral deposition in a concentration-dependent manner, with the greatest effects at 10 ng/mL. LRAP significantly upregulated osteogenic (RUNX2, COL1A1, OCN) and odontogenic (MEPE, DMP1) gene expression in hDPSCs. Immunofluorescence revealed nuclear β-catenin translocation in hDPSCs and membrane-associated accumulation in hBMSCs, indicating activation of canonical and non-canonical pathways, respectively. Conclusions: LRAP and SP promote osteogenic differentiation through distinct cell-type-specific signaling mechanisms, highlighting their potential as biomimetic agents for mineralized tissue regeneration.