PhD Fellowship: “Engineering the embryonic haematopoietic stem cell (HSC) niche in vitro”

Background. Bone marrow HSCs are broadly used for clinical transplantations, but the need for donors outstrips supply. Pluripotent human ES/iPS cells could be a great alternative source of HSCs to meet demands. During embryo development, HSCs emerge in the dorsal aorta within the aorta-honad-mesonephros (AGM) region through the process called endothelial-to-haematopoietic transition (EHT). However, molecular mechanisms underlying EHT are poorly understood. Although the cultured mouse AGM region can recapitulate HSC development, multiple attempts to derive HSCs from ES/iPS cells without genetic manipulations fail.

Hypothesis and goals. During embryogenesis, organs and tissues show a great degree of self-organisation. It is becoming increasingly evident that tissue patterning and cell specification can be guided by geometric physical constraints of the substrate. Spatial dorso-ventral polarisation of secreted molecules in the AGM region also play a role in HSC development. We propose that a combination of geometrical constraints and spatially polarised signalling will enable functional AGM organoids to be generated in vitro. The main goal of the project is to generate an efficient in vitro platform for investigating effects of spatial constraints and molecular polarisation on reconstruction of the human AGM region.

Approaches and methodology. The student will generate a dual fluorescent reporter human ES cells using CrispR/CAS9 system to facilitate efficient screening for conditions supporting AGM organoid formation and EHT. Highly controlled geometrically constrained supports for cultured cells and polarised signalling will be established using the cutting-edge micropatterning machine (Primo, Alveole). Cell specification and formation of AGM organoids will be explored using fluorescent microscopy, flow cytometry and gene expression analysis with support of bioinformatics. Blood cells generated in the system will be tested functionally by transplantation into immunocompromised NSG mice.

Impact. Pluripotent hES/iPS cells hold great hope for regenerative medicine. These are potentially a valuable source of HSCs that could overcome the shortage of donors and enhance safety of transplantations. However, to date HSC derivation from cultured hES cells remains a challenge. This project has a strong translational aspect and can open up opportunities to develop new protocols for directed differentiation of bona fide HSCs for clinical applications.

Environment. You will be working in a highly collaborative environment of Medvinsky’s lab. We were the first who discovered the central role of AGM region in HSC development and demonstrated that the AGM region can autonomously generate HSCs in culture. We have a strong record studying both the mouse and human AGM region at cellular and molecular levels, including spatial transcriptomics analyses. This project will be conducted in collaboration with Dr. Guillaume Blin, Quantitative Biology of Pattern Formation group.

Informal enquiries: a.medvinsky@ed.ac.uk