(433j) Developing a Functional and Analytical in Vitro Bone Marrow Analogue

Trabecular bone is a vital tissue that supports mechanical structure, mineral homeostasis, and blood formation, yet detailed understanding of these processes remains limited due to the anatomical inaccessibility of the inner bone cavity. In vitro bone marrow models hold great promise for advancing our understanding of bone marrow biology in both health and disease. A key challenge is the functional coexistence of rigid, mineralized bone and soft, vascularized marrow. We propose that continuous bone remodeling is a critical process that integrates these two distinct tissue microenvironments.

As bone and marrow represent fundamentally different tissue microenvironments, we developed a modular platform that integrates bone- and marrow-mimicking biomaterials to construct a functional and analytically tractable in vitro bone marrow model. For the bone compartment, we engineered demineralized bone paper by sectioning decellularized bovine cortical bone into thin (~20 µm) sheets. This osteoid-inspired biomaterial preserves the hierarchical alignment of collagen fibers and biochemical features of mature lamellar bone, providing a biologically relevant scaffold that supports osteoblast activity and osteoclast-mediated resorption—both essential to bone remodeling. To recreate the marrow microenvironment, we employed inverted colloidal crystal hydrogel scaffolds with fully interconnected, size-controlled spherical pores (300–500 µm), mimicking the architecture of bone marrow sinusoids. When seeded with human bone marrow stromal cells, these scaffolds support the co-culture of hematopoietic cells and recapitulate key aspects of stromal–hematopoietic interactions within a tunable and physiologically relevant 3D matrix.

By integrating these distinct 3D bone and marrow components, we have established a composite in vitro bone marrow analogue that captures tissue-level complexity and supports dynamic crosstalk. This platform enables spatiotemporal control of cellular organization, signaling gradients, and matrix remodeling, making it a powerful tool for mechanistic studies and high-content functional assays. Ultimately, this engineered bone marrow model is expected to advance both basic and translational research, with applications in drug testing, disease modeling, and regenerative medicine.