Elucidating the functions of cardiac-residing hematopoietic stem and progenitor cells during development and injury

• Applicant: Felix Gunawan, Ph.D.
• Subject Area: Developmental Biology ; Cell Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565645410

Hematopoietic stem and progenitor cells (HSPCs) give rise to all blood cells throughout life and exhibit high diversity in their fate lineages and functional characteristics. No reliable methods are currently available to grow HSPCs in vitro, a key objective in therapies for blood disorders. Thus, in vivo studies addressing where HSPCs originate and reside in at later stages are critical to identifying the molecular players and defining the microenvironmental conditions that promote HSPC development, functions, and fate heterogeneity. Using zebrafish as a model compatible with imaging of HSPCs in vivo, our recent work showed that the heart endothelial cells, or endocardial cells, give rise to and retain a subpopulation of HSPCs. This HSPC subpopulation is maintained in the high-pressure cardiac environment and exposed to blood flow, which differ from the conditions other HSPC populations experience in niches protected from flow. We hypothesize that the endocardial-residing HSPCs facing high mechanical forces acquire specialized functions and fates and can function as quick responders that can differentiate into blood cells, such as immune cells and platelets, particularly under stress. To address this hypothesis, we have established new zebrafish models for cardiovascular injury using laser ablation and vascular bacterial infection. Both stress models induce rapid recruitment of cells positive for HSPC markers, allowing further studies we proposed to determine where the cells are derived from and what their function is. Our proposed work will identify the functions and molecular profiles of the endocardial-derived HSPCs during development and disease. First, we will perform transcriptomic profiling of HSPCs in the endocardium, in other hematopoietic niches that are protected from flow, as well as from the endocardium with reduced blood flow, and identify differently regulated genes between the two populations. We will initially focus on mechanoresponsive genes that might be highly transcribed in endocardial HSPCs and assess the differentiation states and function of endocardial-residing HSPCs in which these genes are knocked out. Second, we will trace the fates of HSPCs that arrive/are derived from the endocardium at different developmental stages (embryonic to adult) and determine their contribution to different hematopoietic lineages. Finally, using photoconversion-based lineage tracing in the injury and infection models we established, we will assess the recruitment of HSPCs from the endocardium to sites of vascular injury and infection. Using cell-specific ablation of endocardial HSPCs, we will test the effects of the manipulations on normal cardiovascular development, as well as on the reactions to vascular injury and infection. Together, our work will provide important insight into the mechanisms by which HSPC fate, function and behaviours are regulated by biomechanical forces in different hematopoietic niches.

• DFG Programme: Research Grants