Aqueous extracts of propolis modulate ECM remodeling and calcium levels during pre-osteoblast differentiation

Osteoporosis and other bone-loss-related disorders remain major health concerns, underscoring the demand for innovative regenerative therapies. Propolis, a natural resinous substance rich in bioactive compounds such as caffeic acid phenethyl ester (CAPE), has emerged as a promising candidate for modulating bone regeneration. However, the cellular and molecular mechanisms underlying its effects on osteoblast function are not fully elucidated. In this study, we evaluated the impact of an aqueous extract of propolis on pre-osteoblast adhesion, proliferation, differentiation, extracellular matrix (ECM) remodeling, and inflammation. Our results showed that while propolis treatment did not alter cell adhesion or cytoskeletal organization, it significantly enhanced cell proliferation through the upregulation of CDK2 expression and phosphorylation, suggesting stimulation of G1/S cell cycle progression. Differentiation analyses demonstrated increased expression of osteogenic markers, including BMP7, Runx2, and Osterix, as well as modulation of the RankL/OPG axis. Despite limited mineralization, we observed enhanced collagen deposition and upregulation of ECM-related proteins, such as bone sialoprotein (BSP), alongside increased MMP9 activity, indicating active ECM remodeling. Moreover, propolis induced an anti-inflammatory cytokine profile, characterized by elevated IL-10 and reduced levels of pro-inflammatory cytokines IL-6, IL-18, and TNF-α. Altogether, our findings suggest that aqueous propolis extract promotes an osteogenic phenotype by modulating cell cycle progression, enhancing osteoblastic differentiation, remodeling the ECM, and reducing inflammation. These results support the potential use of propolis as a natural therapeutic agent in bone tissue engineering and regenerative medicine.