Bone marrow ECM-based vascular niche modeling for the evaluation of HSC/leukemic cell interaction with niche cells

Bone marrow vascular niche regulates both hematopoiesis and hematopoietic disorders, including acute and chronic leukemia. However, it is still not fully understood at the structural and functional levels owing to its inaccessibility in situ. Here, a biomimetic bovine decellularized bone marrow extracellular matrix (dbECM) mixed hydrogel was developed. Proteomics validation confirmed its retention of bone marrow-specific ECM components. The mechanical properties and microstructure of the mixed hydrogel provided a biomimetic platform that integrates biochemical and physical cues for niche functional studies. Vascular networks with multilayered murine C166 endothelial cells (ECs) and mesenchymal stromal cells (MSCs: C3H10T1/2 cells or primary murine bone marrow-derived MSCs) were successfully formed in the mixed hydrogel scaffold. This murine vascular niche model can be utilized to unravel the dynamic events of Lin^-c-Kit⁺ hematopoietic cells /leukemic cell interaction with niche components. MSCs mainly contributed to hematopoietic stem cell preservation, whereas the ECM served as permissive scaffolding but did not directly instruct stemness maintenance. The dynamic disruption of leukemic cells to the vascular integrity was recapitulated in this vascular niche model. Even though leukemic cells adhere to both ECs and MSCs, their adhesion to MSCs was the main niche factor maintaining leukemic stem cells and leading to chemoresistance in the bone marrow. Collectively, this bioengineered short-term static niche delineates the specific roles of dbECM as a structural foundation, ECs as spatial organizers, and MSCs as functional regulators, advancing our understanding of niche-directed physiology and pathology and accelerating the development of microenvironment-targeted therapies.