Evolutionary Conservation of Human CD34+ Endothelial Progenitor Cells Differentiation in the Zebrafish Developing Vascular System Ombretta Pozzoli1, Marta Lacovich1, Emanuela Siciliano1, Daniele Avitabile2, Carla Lora Lamia3, Elisa Vigna4, Andrea Biondi5, Franco Cotelli2, Maurizio C. Capogrossi2 and Maurizio Pesce1
1Centro Cardiologico Monzino, Milano, 2IDI, Roma, 3Università degli Studi di Milano, 4Università di Torino, 5Università Bicocca, Milano, Italia
Zebrafish is a well established model to study vertebrate angiogenesis. We used the zebrafish embryo as a novel tool to investigate both the angiogenic potential and the evolutionary conservation of human endothelial progenitor cells differentiation. Hematopoietic and vascular cells may arise from a common progenitor named the “hemangioblast”. Although recent results support the first in vivo evidence for the existence of the hemangioblast in zebrafish, little is known about the differentiation mechanisms of this common progenitor in humans.
We performed a cell transplantation assay by using the transgenic TG(fli1:EGFP) zebrafish embryo at 48 hpf stage, to test the differentiation potential of CD34+ stem cells, isolated from human umbilical cord blood. In the 48 hpf embryo, hCD34+ injected into the vasculature circulate, incorporate into the blood vessel wall and differentiate into mature endothelial cells; furthermore these cells induce ectopic blood vessels development.
To investigate whether hCD34+ are integrated into the embryo vasculature and function as the zebrafish hemangioblast, we transplanted these cells at blastula stage before the onset of gastrulation. hCD34+ cells are co-segregated at tailbud stage with cells belonging to the zebrafish hemangioblast presumptive territory, and then incorporated in the cardiovascular system. Furthermore, hCD34+ derived-cells are detected in the blood as well as in the blood islands, supporting the hypothesis that hCD34+ progenitors might have the potential to give rise to both vascular and hematopoietic cells.
Our results provide the first in vivo evidence of an evolutionary conservation of differentiation pathways of human CD34+ precursors in the developing zebrafish embryo.
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