Characterisation of the human hematopoietic stem cell niche in bone marrow during steady state and acute myeloid leukaemia (AML)

• Applicant: Susann Rahmig, Ph.D.
• Subject Area: Hematology, Oncology
• Term: from 2021 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495195939

Throughout life the cells in our blood are replenished by so-called hematopoietic stem cells (HSCs) in the bone marrow, that can differentiate into white and red blood cells, as well as platelets via several progenitor stages. A deregulation of this differentiation process can lead to a lack of certain blood cells or to malignant diseases like leukaemia. Maintenance and differentiation of HSCs are regulated by different intrinsic and extrinsic factors. The extrinsic signals are provided by a microenvironment of cellular and molecular factors in the bone marrow, termed the ‘stem cell niche’. However, which factors of the stem cell niche regulate blood formation in what way is only insufficiently studied and especially for the human system there is very limited data available. Therefore, the aim of this research project is to characterize the human hematopoietic stem cell niche in healthy donors and leukaemia patients. The host laboratory has an extensive tissue biobank comprising thousands of bone marrow samples from leukaemia patients and a couple hundred bone marrow aspirates and trephines from healthy donors who underwent hip replacement surgery. Using samples from healthy individuals, non-hematopoietic bone marrow cells will be assessed for their cellular heterogeneity and gene expression by single cell RNA sequencing (scRNA-seq) (objective 1). From this analysis we also hope to identify cell type-specific markers which can be used to discriminate the different niche cell populations by antibodies. By using a combination of these newly identified and already known markers we will perform spatial characterization of the stem cell niche in bone marrow trephines from healthy donors by means of imaging mass cytometry (objective 2). We also want to perform scRNA-seq of non-hematopoietic bone marrow cells from leukaemia patients and compare this data to that from the healthy samples, to recognize alterations in gene expression and cellular composition occurring during the emergence of leukaemia (objective 4). Finally, we want to establish an in vivo model of the human bone marrow niche by adapting the ‘ossicle’ model, which uses the capability of human mesenchymal stem cells to form bone organoids with a bone marrow cavity after subcutaneous transplantation into mice (objective 3). By adding human endothelial cells, employing new mouse strains and using new carrier materials, we want to improve the ossicle model to resemble the human stem cell niche as close as possible. We then want to study the interactions healthy and leukemic bone marrow cells with components of the ossicles and again identify differences between healthy and leukemic niches (objective 4). The overall goal of the project is to identify potential targets within the stem cell niche that could be exploited for therapeutic application.

• DFG Programme: WBP Fellowship
• International Connection: United Kingdom
• Host: Professor Paresh Vyas, Ph.D.