Extracellular matrix-inspired multi-morphology microspheres harness osteogenic-prone stem cells to recruit and reprogram adjacent stem cells for synergistic bone regeneration

Governed by epigenetic regulation, distinct types of adult stem cells exhibit lineage-specific differentiation biases. Osteogenic-prone stem cells might recruit, proliferate, and induce osteogenesis in adjacent osteogenic-weak stem cells, constituting a key mechanism for enhancing endogenous osteogenesis. Biomimetic scaffolds mimicking osteogenic-prone stem cells-favorable extracellular matrix (ECM) could potentiate this intercellular cascade. In this study, according to the gene signatures of osteogenic-prone stem cell subtype, we developed biomimetic mineralized (methacrylated gelatin)-fibrinogen crosslinked hydrogel microspheres (bmGFMs) via microemulsion and photocrosslinking method to support multidirectional cell growth. Fibrinogen was innovatively employed as a biomimetic mineralization template to construct microspherical mineralized compartments while maintaining the accessibility of protein-cell binding sites, thereby creating a hierarchical, osteoinductive ECM microtopography with combined organic-inorganic surface. Physicochemical and mechanical signalings from bmGFMs preferentially attracted osteogenic-prone stem cells for surface colonization and osteogenesis through FAK/PKC/PI3K/Akt signaling pathway. Benefiting from superior interstitial fluid infiltration, paracrine factors (such as SDF-1) secreted by these primed cells further recruited adjacent osteogenic-weak populations, inducing their osteogenic conversion and expanding osteogenic sources. In vivo study showed that bmGFMs guided spatiotemporal bone formation, yielding high-density intramembranous ossification through dual-cell collaborative synergy. These results demonstrate the significance of stem cell-communication-based biomimetic materials for osteogenesis.