A Multi-Niche Microvascularized Human Bone-Marrow-on-a-Chip

Abstract

21The human bone marrow (hBM) is a complex organ critical for hematopoietic and immune 22 homeostasis, and where many cancers metastasize. Yet, understanding the fundamental biology of 23 the hBM in health and diseases remain difficult due to complexity of studying or manipulating the 24 BM in humans. Accurate in vitro models of the hBM microenvironment are critical to further our 25 understanding of the BM niche and advancing new clinical interventions. Although, in vitro 26 culture models that recapitulate some key components of the BM niche have been reported, there 27 are no examples of a fully human, in vitro, organoid platform that incorporates the various niches 28 of the hBM -specifically the endosteal, central marrow, and perivascular niches -thus limiting 29 their physiological relevance. Here we report an hBM-on-a-chip that incorporates these three 30 niches in a single micro-physiological device. Osteogenic differentiation of hMSCs produced 31 robust mineralization on the PDMS surface ("bone layer") and subsequent seeding of endothelial 32 cells and hMSCs in a hydrogel network ("central marrow") created an interconnected vascular 33 network ("perivascular niche") on top. We show that this multi-niche hBM accurately mimics the 34 ECM composition, allows hematopoietic progenitor cell proliferation and migration, and is 35 affected by radiation. A key finding is that the endosteal niche significantly contributes to hBM 36 physiology. Taken together, this multi-niche micro-physiological system opens up new 37 opportunities in hBM research and therapeutics development, and can be used to better understand 38 hBM physiology, normal and impaired hematopoiesis, and hBM pathologies, including cancer 39 metastasis, multiple myelomas, and BM failures. 40 41 42Hematopoietic stem cells (HSCs) reside and self-renew in the bone marrow (BM) throughout 43 adulthood, where multipotency is maintained and hematopoietic progenitor cells (HPCs) 44 differentiate to maintain hematopoietic homeostasis (1). The microenvironment that maintains 45 HSC potency and regulates differentiation of HPCs, i.e. the HSC niche, is characterized by BM 46 stromal cells, extracellular matrix (ECM), and biochemical and physical signals (2-4). The HSC 47 niche can be disrupted, naturally with age, with radiation or chemotherapies, or by primary and 48 metastatic malignancies in the BM, and also through the mobilization of HSCs for apheresis. 49Novel, human, and potentially patient specific, models of this microenvironment are critical to 50 advancing our understanding of the BM niche, develop new BM directed therapeutics, and 51 evaluate the effects and predict the success (or failure) of clinical interventions (5). 52Our understanding of the location and composition of the BM microenvironment has been 53 changing over the last two decades. Early research had indicated that HSCs resided in a hypoxic, 54 endosteal niche, where potency was maintained (6, 7). However, recent findings have shown that 55 multi-potent HSCs are perivascular and ex...

Microfluidics and organ-on-a-chip technologies: A systematic review of the methods used to mimic bone marrow

“…Here, two relevant papers shall be mentioned that are still under the peer review process and were not formally included in this revision. Nelson et al developed a device where co-culture is done with main cells that compose the three niches: osteoblasts (specific endosteal cell), endothelial cells (specific perivascular cell), mesenchymal cells, and hematopoietic cells (niches cells) [ 127 ]. The culture was implemented in a hydrogel matrix based on collagen types I and IV, fibronectin, and lamina, all components existing in the BM microenvironment [ 8 ].…”

Hematopoietic progenitors polarize in contact with bone marrow stromal cells by engaging CXCR4 receptors

“…The model was inspired by the pioneering work of Noo-Li Jeon, who described the set-up for the micro-channel geometry and the culture conditions necessary for inducing endothelial cells self-organization into hollow and perfusable 3D networks (Kim et al, 2013). Side channels included osteoblasts in 3D matrices made of collagen and fibrin to model a minimal version of the endosteal niche (Nelson et al, 2019). Maskless photo-lithography was used to test several chip prototypes and optimize channel design, which included the presence of pillars preventing the collapse of the 3D matrix in response to high contractile forces produced by osteoblasts (see Methods and Supplementary Figure S1).…”

Bioengineering the Bone Marrow Vascular Niche

“…Resuming all these parameters have permitted the reproducible production of a perfusable vascular network in a microfluidic chip. Ever since, these chips have been reproduced in various ways and designed according to the needs ( Jeon et al, 2014 ; Wang et al, 2015 ; Chen et al, 2017 ; Oh et al, 2017 ; Phan et al, 2017 ; Palikuqi et al, 2020 ), and have been used for BM engineering ( Bersini et al, 2014 ; Jeon et al, 2015 ; Jusoh et al, 2015 ; Nelson et al, 2019 ; Bessy et al, 2020 ; Chou et al, 2020 ; Ma et al, 2020 ).…”

“…Recent advances in the field have led to the fabrication of complex compartmented chips based on the same principle, achieving the aim to mimic physiological conditions. First, Nelson added a layer of osteoblast to the EC and MSC network, thus generating a new compartment, mimicking a marrow-bone interaction ( Nelson et al, 2019 ). Once again, the overall change of organization of the vascular network, when formed in presence of different supporting cell types, was reported, with notably a vessel thinning to a capillary like structures when in presence of osteoblasts.…”