Overexpression of interleukin-4 using adeno-associated virus is a potential strategy to enhance bone regeneration

This study aimed to investigate the bone regeneration potential of IL-4 gene delivery via adeno-associated virus (AAV) vectors, with a particular focus on modulating macrophage polarization and promoting osteogenic differentiation. Four different AAV serotypes (AAV1, AAV2, AAV5, and AAV6) encoding the IL-4 gene were evaluated in rat and human gingival fibroblasts and dental pulp stem cells (DPSCs). AAV2 exhibited the highest transduction efficiency and IL-4 expression in all tested cell types. IL-4 transduced DPSCs demonstrated enhanced osteogenic differentiation, as evidenced by the upregulation of osteogenic markers, increased alkaline phosphatase activity, and elevated calcium deposition. IL-4 transduction activated the extracellular signal-regulated kinase signaling pathway, contributing to osteogenesis. To assess the therapeutic efficacy of AAV2-IL-4 in vivo, a lipopolysaccharide-induced calvarial osteolysis model was established in C57BL/6 mice. AAV2-IL-4 administration significantly reduced bone resorption, as confirmed by micro-CT and histological analysis. Moreover, IL-4 gene delivery promoted M2 macrophage polarization. These findings highlight AAV2-IL-4 as a promising gene therapy strategy for bone regeneration, effectively integrating immunomodulation and osteogenesis to counteract inflammation-driven bone loss.