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Imprint
Combination of a microphysiologic system and a scaffold-free 3D organoid as a developmental model for ossification
Project
Project code: BfR-ZEBET-08-1322-706
Contract period: 01.07.2017
- 31.12.2019
Purpose of research: Experimental development
Conventional two-dimensional (2D) cell culture is of limited value when complex interactions between various cell types, tissues and organs of higher organisms need to be imitated. Tissue-specific parameters such as the oxygen partial pressure, the composition of the extracellular matrix but also specific mechanical forces are difficult to model in a monolayer. In consequence, the translation of findings from conventional 2D-culture methods towards more complex organisms is often hampered. This poses a problem, especially in regenerative medicine and toxicology; hence a large number of animal experiments are still performed. Yet, due to ethical issues but also the limited comparability between the physiology of laboratory species and humans, concerns rise whether animal models are relevant for translational research. In order to circumvent the difficulties appointed above, advanced technologies such as ‘organ-on-a-chip’ systems can be employed. These are microfluidic systems that enable the reconstitution of physiological parameters of certain tissues and allow a co-cultivation of different cell types in two- or three dimensions (3D). In addition to Liver-, Lung- and Kidney-on-a-chip models, numerous other organ-chips have been already published. However, there is no physiological relevant ‘Bone-on-a-chip’ model that takes all key parameters such as hypoxia, mechanical load, the cellular composition and environment that influence bone function into account. In addition to its motility-related functions in the musculoskeletal system, bone hosts the hematopoietic stem cell (HSC) - niche. The HSC niche is of utmost importance in the formation of the blood and immune system. By means of conventional cell culture, the HSC phenotype, including stem cell-typical properties, can be maintained only to a limited extent. Neither the complex interactions with mesenchymal stromal cells (MSCs) or vasculature-forming cells, nor the different oxygen gradients can be modeled as under in vivo conditions. Furthermore, the bone of an organism is characterized by a constant resorption and regeneration of tissue, a process known as bone remodeling. Here, bone forming osteoblasts (OBs) and bone-resorbing osteoclasts (OCs) interact as a consequence of stimulation by external signals such as mechanical stress. The proposed project is focused on the development of a micro-physiological ‘Bone-on-a-chip’ system. In order to simulate physiological parameters and the cellular composition of bone, the model system combines a microfluidic platform and a tissue analogue – an organoid. The tissue analogue is planned to be generated scaffold-free from primary cells (MSCs, OBs and HSCs) isolated from bone marrow and bone. The primary material is provided through a cooperation with the DRK clinics Westend. Since these are samples from different patients, a high variability between the individual donors can be assumed. In order to keep this variability as low as possible, all donated cell samples have to be characterized in advance for phenotypes such as metabolic activity and proliferation rate. Both MSCs and OBs are examined for their differentiation potential towards the osteogenic, adipogenic, and chondrogenic lineage. Subsequently, tissue analogues are generated only from cells of donors that exhibit similar properties. After successful generation of an organoid from OBs and their adaptation to the microphysiological system, a co-culture system that combines OBs and MSC will be established. In order to simulate bone remodeling, bone-resorbing OCs are needed in the course of the project. OCs might either autonomously differentiate from macrophages and thus the hematopoietic lineage, i.e. the HSCs added to the organoid, or are subsequently added in form of a commercially available cell line to the organoid. Similar to MSCs, HSCs will also be isolated from bone marrow fluid. In order to be able to reproduce the bone as precisely as possible, vascularization of the tissue analog is finally necessary to ensure optimised supply of oxygen and nutrients throughout the organoid. After a successful establishment of all parameters, the ‘Bone-on-a-chip’ is meant to be used as a developmental model for human ossification that can be utilized for both basic science and toxicological studies (i.e. teratogenicity of chemicals and/or drugs).
Section overview
Subjects
- Animal health
- Biotechnology
Framework programme
Funding programme
Excutive institution
BfR - Centre for Documentation and Evaluation of Alternatives to Animal Experiments (BfR - ZEBET)
