Zebrafish as a Model System for the Interrogation of Hematopoietic Stem Cell Engraftment

Abstract

Hematopoietic stem cell (HSC) transplant is a treatment used to infuse healthy blood stem cells to patients that suffer from a range of blood disorders, such as leukemia. Although transplantations are successful nearly 85% of the time, the associated morbidity and mortality rates are still too high. To improve HSC transplantation outcomes, it is crucial to better understand all facets of HSC engraftment, which includes the seeding, expansion, and differentiation of donor HSC into the recipient. Zebrafish is an ideal animal model to study engraftment due to their small size, high fecundity, and malleable genetics. We have established a novel transplantation model using the zebrafish runx1 W84X bloodless mutant strain. These animals lack endogenous HSC and thus possess empty HSC niche available for donor cell engraftment without the need for pre‐conditioning regimens. Transplantation of donor marrow cells that ubiquitously express green fluorescent protein (ubi:GFP) into runx1 W84X homozygous mutants at two days‐post fertilization (dpf) results in robust GFP+ donor cell engraftment that sustains the blood system of the mutants into adulthood. Sham‐injected and un‐injected embryos served as negative controls. Using this model, we will image transplanted embryos daily to visualize all stages of engraftment. From 4–7 dpf, we observed seeding of GFP+ cells into all hematopoietic tissues including the thymus, caudal hematopoietic tissue, and kidney marrow (equivalent to mammalian bone marrow). We will use confocal microscopy to gain a more in‐depth view of the cell‐to‐cell interactions occurring within these niches to understand engraftment. Additionally, we will use this assay for longitudinal studies to determine what facets predict which animals will sustain high versus low donor cell chimerism. Studying this animal model could advance our understanding of human HSC transplantation outcomes.Support or Funding InformationNIH (Grant # R25‐GM104547); Cancer Research Center (Grant # P30CA013330)