Multipotent hematopoietic stem and progenitor cells (HSPC) reside in specialized stem cell niches within the bone marrow, that provide a suitable microenvironment for lifelong maintenance of the stem cells. Meaningful in vitro models recapitulating the in vivo stem cell niche biology can be employed for both basic research as well as for applied sciences and represent a powerful tool to reduce animal tests in preclinical studies. Recently we published the generation of an in vitro bone marrow niche model, capable of long-term cultivation of HSC based on an organ-on-a-chip platform. This study provides a detailed analysis of the 3D culture system including matrix environment analysis by SEM, transcriptome analysis and system intrinsic differentiation induction. Furthermore, the bone marrow on a chip model can serve to multiply and harvest HSPC, since repeated cell removal not compromised the functionality of the culture system. The prolongation of the culture time to 8 weeks demonstrate the capacity to apply the model in repeated drug testing experiments. The quality of the presented system is emphasized by the differentiation capacity of long-term cultivated HSPC in vitro and in vivo. Transplanted human HSPC migrated actively into the bone marrow of irradiated mice and contributed to the long-term reconstitution of the hematopoietic system after four and eight weeks of in vitro cultivation. The introduced system offers a multitude of possible applications to address a broad spectrum of questions regarding HSPC, the corresponding bone marrow niche biology, and pathological aberrations.

Bone marrow-on-a-chip: Emulating the human bone marrow