A 3D Human Bone and Bone Marrow‐on‐a‐Chip Model for In Vitro Bone Remodeling and Immune Cell Maintenance

We developed a human Bone-on-a-Chip (BOAC) model that integrates autologous primary immune and bone cells on native human bone substrates within a xeno-free, perfused environment. In contrast to existing models, which focus primarily on hematopoietic or stromal compartments, our system recapitulates key aspects of functional bone remodeling and enables the maintenance of mature immune cells (up to 42 days), with preserved functional responsiveness at defined time points during culture. Dynamic flow and sequential cell seeding facilitated osteoclast-mediated resorption, osteoblast-driven matrix formation, and the maintenance of donor-specific immune profiles over extended culture periods. The balance between bone cell activity and immune cell persistence was further optimized by controlled temperature modulation. The BOAC model preserves key features of bone and bone marrow physiology, including extracellular matrix formation, soluble factor signaling, and cellular heterogeneity. The bone scaffold provides a physiologically relevant 3D architecture derived from decellularized human trabecular bone. Single-nucleus RNA sequencing confirmed the presence of major donor-specific immune and bone cell populations. This 3D human in vitro system provides a robust platform for translational research and personalized medicine.