Isolation and characterization of hematopoietic stem cells in teleost fish

• Transplantation model systems were established in the zebrafish and clonal ginbuna carp.
• Hematopoietic stem cells are present in the kidney, but not in the spleen in teleost fish.
• The frequency of hematopoietic stem cells in the zebrafish kidney is similar to the murine bone marrow.
• Hematopoietic stem cells can be purified using fluorescent dyes or transgenic animals in teleost models.
• Kidney renal tissues may play an important role in the maintenance of hematopoietic stem cells as the niche.

Despite 400 million years of evolutionary divergence, hematopoiesis is highly conserved between mammals and teleost fish. All types of mature blood cells including the erythroid, myeloid, and lymphoid lineages show a high degree of similarity to their mammalian counterparts at the morphological and molecular level. Hematopoietic stem cells (HSCs) are cells that are capable of self-renewal and differentiating into all hematopoietic lineages over the lifetime of an organism. The study of HSCs has been facilitated through bone marrow transplantation experiments developed in the mouse model. In the last decade, the zebrafish and clonal ginbuna carp (Carassius auratus langsdorfii) have emerged as new models for the study of HSCs. This review highlights the recent progress and future prospects of studying HSCs in teleost fish. Transplantation assays using these teleost models have demonstrated the presence of HSCs in the kidney, which is the major hematopoietic organ in teleost fish. Moreover, it is possible to purify HSCs from the kidney utilizing fluorescent dyes or transgenic animals. These teleost models will provide novel insights into the universal mechanisms of HSC maintenance, homeostasis, and differentiation among vertebrates.