Further development and refinement of hematopoietic cell transplantation in zebrafish

Abstract

Hematopoietic stem cells are a rare but crucial population of cells that are responsible for maintaining hematopoiesis throughout vertebrate life. Clinically, hematopoietic stem cells have been utilised for treatment of hematological disease, autoimmune disorders and cancer through the application of hematopoietic cell transplants. A detailed understanding of the behaviour of hematopoietic stem cells and their post-transplant interaction with the niche can lead to improved transplant outcomes. However, there are many challenges in studying hematopoietic stem cell transplantation in mammalian systems owing to the difficulty of observing transplanted cells in vivo. This thesis aims to refine hematopoietic cell transplantation protocols described in adult zebrafish (Danio rerio). To this end, fluorescent hematopoietic stem and precursor populations were further characterised in transgenic donor fish using a combination of flow cytometry and microscopy techniques. Furthermore, Runx:mCherry positive populations were assessed for stem cell functionality through transplantation. The utility of bloodless cmybt25127 mutant fish to investigate hematopoietic cell transplantation by longitudinal imaging was evaluated. In addition, the stimulatory effects of viral mimetics were assessed in transgenic and cmybt25127 mutant fish. Finally, the effect of antibiotic treatment was investigated in transgenic fish. These experiments revealed two fluorescent cell populations in Tg(Runx:mCherry) transgenic zebrafish kidney marrow. Hematopoietic cell transplant studies and transcript analysis indicated that the Runx:mCherry low population could be enriched for hematopoietic stem cells. Furthermore, experiments revealed that homozygous cmybt25127 mutant fish are capable of regenerating their tail fin following amputation and of initiating a partial anti-viral response to resiquimod stimulation. Finally, a post-transplant scoring system was devised in homozygous cmybt25127 mutant fish and used to assess functional differences between Runx:mCherryhigh and low populations. Overall, this thesis has further developed hematopoietic cell transplantation in zebrafish and demonstrated that in vivo imaging can be used to track the transplant outcome and behaviour of transplanted cells.