Bone-derived bioactive substrates promote axonal sprouting but elicit astrocyte reactivity: Implications for CNS-repair scaffold design

Mineralized bone is increasingly considered as a functional substrate for regenerative applications, yet its impact on neuron–glia remodeling remains insufficiently defined. We cultured ex vivo injured rat hippocampal tissue on glass coverslips either uncoated or coated with micron-scale mouse skull bone particles and quantified neurite architecture and astrocyte morphology. Bone-particle substrates supported robust adhesion and selectively modulated process development. Axons on bone displayed a 2.8-fold increase in varicosity-like expansion size and 2.2-fold higher neurofilament-M expression relative to glass, indicating potentiated axonal sprouting. In contrast, dendrites exhibited 20% shorter mean length and 73% lower branching. Astrocytes on bone showed 21% shorter processes with 34% fewer processes per cell; total cell area and GFAP levels were unchanged. However, astrocytes displayed increased circularity, decreased roundness, and elevated solidity—morphologies consistent with a reactive, potentially chronic, state. Together, these data identify mineralized bone as a bioactive osseous substrate that enhances axonogenesis while biasing astrocytes toward reactivity. This divergence suggests design trade-offs for osseous or mineral-hybrid scaffolds aimed at central nervous system repair. Our findings provide quantitative guidance for engineering bone-derived or mineral-composite scaffolds that differentially control neuronal and glial outcomes in neural repair strategies.