Synergistic effects of astragalus on 3D-printed calcium silicate/poly-ε-caprolactone scaffolds to regulate inflammation/osteogenesis for bone regeneration

Abstract

Bone defects represent a significant clinical challenge, traditionally addressed primarily through scaffold-based repair strategies. However, recent studies have revealed that relying solely on scaffolds may not fully overcome the bottlenecks in bone defect repair. Mounting evidence suggests that modulating the inflammatory response plays a crucial role in the bone healing process. While moderate inflammation can promote bone tissue regeneration, excessive or prolonged inflammatory responses may impede the repair process. Our previously developed calcium silicate (CS) scaffold, known to stimulate osteoblast proliferation and accelerate bone tissue formation, was enhanced with magnesium–strontium to boost cellular biological activity and foster bone formation and angiogenesis. In this study, the effects of 3D-printed CS scaffolds reinforced with astragalus (Ast) on inflammation regulation and osteogenic gene expression were examined. X-ray diffraction and Fourier transform infrared spectroscopy confirmed that the Ast phase structure and chemical functional groups were added to the materials. The findings revealed that integrating Ast improves scaffold biocompatibility, bioactivity, and bone and vascular tissue formation efficacy, enhances mechanical strength, and decelerates biodegradation. The 5% Ast-containing CS scaffold exhibited superior capabilities in promoting cell proliferation and differentiation, indicative of effective bone regeneration. Moreover, analysis of hMSC-seeded AstCS scaffold supernatants revealed significantly reduced levels of pro-inflammatory cytokines IL-1β and IL-6, coupled with elevated expression of the anti-inflammatory factor IL-1RA. These results suggest that Astragalus incorporation effectively modulates inflammatory signaling in the scaffold microenvironment. Transcriptome RNA sequencing revealed that this scaffold modulated multiple signaling pathways crucial for bone regeneration, such as WNT, AKT, and PI3K, and significantly influenced genes associated with cellular bone regeneration, angiogenesis, and immune responses. These results highlight the potential of combining Ast with CS in 3D-printed scaffolds for bone tissue engineering, offering new strategies for employing natural pharmaceutical ingredients as bioactivity enhancers and providing a substantial foundation for designing future bone regeneration materials with immune-modulating capabilities.