Three dimensional de novo micro bone marrow and its versatile application in drug screening and regenerative medicine

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 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.

The extracellular matrix of hematopoietic stem cell niches

•

Comprehensive overview of different classes of ECM molecules in the HSC niche.

•

Overview of current knowledge on role of biophysics of the HSC niche.

•

Description of approaches to create artificial stem cell niches for several application.

•

Importance of considering ECM in drug development and testing.

Hematopoietic stem cells (HSCs) are the life-long source of all types of blood cells. Their function is controlled by their direct microenvironment, the HSC niche in the bone marrow. Although the importance of the extracellular matrix (ECM) in the niche by orchestrating niche architecture and cellular function is widely acknowledged, it is still underexplored. In this review, we provide a comprehensive overview of the ECM in HSC niches. For this purpose, we first briefly outline HSC niche biology and then review the role of the different classes of ECM molecules in the niche one by one and how they are perceived by cells. Matrix remodeling and the emerging importance of biophysics in HSC niche function are discussed. Finally, the application of the current knowledge of ECM in the niche in form of artificial HSC niches for HSC expansion or targeted differentiation as well as drug testing is reviewed.

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

Bone marrow (BM) is an organ responsible for crucial processes in living organs, e. g., hematopoiesis. In recent years, Organ-on-a-Chip (OoC) devices have been used to satisfy the need for in vitro systems that better mimic the phenomena occurring in the BM microenvironment. Given the growing interest in these systems and the diversity of developed devices, an integrative systematic literature review is required. We have performed this review, following the PRISMA method aiming to identify the main characteristics and assess the effectiveness of the devices that were developed to represent the BM. A search was performed in the Scopus, PubMed, Web of Science and Science Direct databases using the keywords (("bone marrow" OR "hematopoietic stem cells" OR "haematopoietic stem cells") AND ("organ in a" OR "lab on a chip" OR "microfluidic" OR "microfluidic*" OR ("bioreactor" AND "microfluidic*"))). Original research articles published between 2009 and 2020 were included in the review, giving a total of 21 papers. The analysis of these papers showed that their main purpose was to study BM cells biology, mimic BM niches, model pathological BM, and run drug assays. Regarding the fabrication protocols, we have observed that polydimethylsiloxane (PDMS) material and soft lithography method were the most commonly used. To reproduce the microenvironment of BM, most devices used the type I collagen and alginate. Peristaltic and syringe pumps were mostly used for device perfusion. Regarding the advantages compared to conventional methods, there were identified three groups of OoC devices: perfused 3D BM; co-cultured 3D BM; and perfused co-cultured 3D BM. Cellular behavior and mimicking their processes and responses were the mostly commonly studied parameters. The results have demonstrated the effectiveness of OoC devices for research purposes compared to conventional cell cultures. Furthermore, the devices have a wide range of applicability and the potential to be explored.

In Situ Articular Cartilage Regeneration through Endogenous Reparative Cell Homing Using a Functional Bone Marrow-Specific Scaffolding System

In situ tissue regeneration by homing endogenous reparative cells to the injury site has been extensively researched as a promising alternative strategy to facilitate tissue repair. In this study, a promising scaffolding system DCM-RAD/SKP, which integrated a decellularized cartilage matrix (DCM)-derived scaffold with a functionalized self-assembly Ac-(RADA)₄-CONH₂/Ac-(RADA)₄GGSKPPGTSS-CONH₂ (RAD/SKP) peptide nanofiber hydrogel, was designed for repairing rabbit osteochondral defect. In vitro experiments showed that rabbit bone marrow stem cells migrated into and have higher affinity toward the functional scaffolding system DCM-RAD/SKP than the control scaffolds. One week after in vivo implantation, the functional scaffolding system DCM-RAD/SKP facilitated the recruitment of endogenous mesenchymal stem cells within the defect site. Moreover, gene expression analysis indicated that the DCM-RAD/SKP promoted chondrogenesis of the recruited cells. In vivo results showed that the DCM-RAD/SKP achieved superior hyaline-like cartilage repair and successful subchondral bone reconstruction. By contrast, the control groups mostly led to fibrous tissue repair. These findings indicate that the DCM-RAD/SKP can recruit endogenous stem cells into the site of cartilage injury and promote differentiation of the infiltrating cells into the chondrogenic lineage, holding great potential as a one-step surgery strategy for cartilage repair.