A parallelized, perfused 3D triculture model of leukemia for in vitro drug testing of chemotherapeutics

Leukemia patients undergo chemotherapy to combat the leukemic cells (LCs) in the bone marrow. During therapy not only the LCs, but also the blood-producing hematopoietic stem and progenitor cells (HSPCs) may be destroyed. Chemotherapeutics targeting only the LCs are urgently needed to overcome this problem and minimize life-threatening side-effects. Predictive in vitro drug testing systems allowing simultaneous comparison of various experimental settings would enhance the efficiency of drug development. Here, we present a three-dimensional (3D) human leukemic bone marrow model perfused using a magnetic, parallelized culture system to ensure media exchange. Chemotherapeutic treatment of the acute myeloid leukemia cell line KG-1a in 3D magnetic hydrogels seeded with mesenchymal stem/stromal cells (MSCs) revealed a greater resistance of KG-1a compared to 2D culture. In 3D tricultures with HSPCs, MSCs and KG-1a, imitating leukemic bone marrow, HSPC proliferation decreased while KG-1a cells remained unaffected post treatment. Non-invasive metabolic profiling enabled continuous monitoring of the system. Our results highlight the importance of using biomimetic 3D platforms with proper media exchange and co-cultures for creating in vivo-like conditions to enable in vitro drug testing. This system is a step towards drug testing in biomimetic, parallelized in vitro approaches, facilitating the discovery of new anti-leukemic drugs

Rebuilding the hematopoietic stem cell niche: Recent developments and future prospects

Hematopoietic stem cells (HSCs) have proven their clinical relevance in stem cell transplantation to cure patients with hematological disorders. Key to their regenerative potential is their natural microenvironment – their niche – in the bone marrow (BM). Developments in the field of biomaterials enable the recreation of such environments with increasing preciseness in the laboratory. Such artificial niches help to gain a fundamental understanding of the biophysical and biochemical processes underlying the interaction of HSCs with the materials in their environment and the disturbance of this interplay during diseases affecting the BM. Artificial niches also have the potential to multiply HSCs in vitro, to enable the targeted differentiation of HSCs into mature blood cells or to serve as drug-testing platforms. In this review, we will introduce the importance of artificial niches followed by the biology and biophysics of the natural archetype. We will outline how 2D biomaterials can be used to dissect the complexity of the natural niche into individual parameters for fundamental research and how 3D systems evolved from them. We will present commonly used biomaterials for HSC research and their applications. Finally, we will highlight two areas in the field of HSC research, which just started to unlock the possibilities provided by novel biomaterials, in vitro blood production and studying the pathophysiology of the niche in vitro. With these contents, the review aims to give a broad overview of the different biomaterials applied for HSC research and to discuss their potentials, challenges and future directions in the field. Statement of significance Hematopoietic stem cells (HSCs) are multipotent cells responsible for maintaining the turnover of all blood cells. They are routinely applied to treat patients with hematological diseases. This high clinical relevance explains the necessity of multiplication or differentiation of HSCs in the laboratory, which is hampered by the missing natural microenvironment – the so called niche. Biomaterials offer the possibility to mimic the niche and thus overcome this hurdle. The review introduces the HSC niche in the bone marrow and discusses the utility of biomaterials in creating artificial niches. It outlines how 2D systems evolved into sophisticated 3D platforms, which opened the gateway to applications such as, expansion of clinically relevant HSCs, in vitro blood production, studying niche pathologies and drug testing