Both primitive and definitive blood cells are derived from Flk-1+ mesoderm - PubMed (original) (raw)

Both primitive and definitive blood cells are derived from Flk-1+ mesoderm

Jesse J Lugus et al. Blood. 2009.

Abstract

Emerging evidence suggests that all hematopoietic and endothelial cells originate from Flk-1(+) mesoderm in the mouse. However, this concept has not been completely proven, especially for the origin of blood cells. Using either Flk1(+/Cre);Rosa26R-EYFP or Flk1(+/Cre);Rosa26R-LacZ mice, we permanently marked Flk-1(+) cells and their progenies to determine the relationship between hematopoietic tissues and cells that express Flk-1. In embryos, all blood cells within the yolk sac and aorta were of Flk-1(+) origin. In addition, nearly all CD45(+) cells in bone marrow and circulating blood in adults were of Flk-1(+) origin. These results provide clear evidence that all blood cells, primitive and definitive, in mice are derived from Flk-1(+) mesodermal cells.

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Figures

Figure 1

A Flk-1+ origin for embryonic blood cells of Flk1+/Cre;Rosa26R-LacZ embryos. (A-E′) E8.5 embryos. (F,F′) E9.5 embryo. (A) Whole-mount image of 3 representative Flk1+/Cre ;Rosa26R-LacZ E8.5 embryos. *Plane of major blood islands in yolk sacs. (A′) Whole-mount high-power magnification of an embryo showing stained dorsal aorta (◀, ▶). (B) Control E8.5 embryos display no LacZ+ cells in their yolk sacs or embryo proper. *Plane of major blood islands in yolk sacs. (C,D) Five-micrometer sections through Flk1+/Cre ;Rosa26R-LacZ E8.5 embryos. (C′,D′) High-power views of blood islands from embryos in panels C and D, respectively. (E,E′) Sections of a control embryo showing an absence of LacZ+ cells in the embryo, yolk sac, or blood islands. (F,G) Representative FACS plots of E9.5 R26R-EYFP and E9.5 Flk1+/Cre ;Rosa26R-EYFP yolk sacs staining for the erythroid cell marker Ter119 and macrophage marker Mac1, respectively (y-axis) and EYFP (x-axis) to assess the origin of these lineage cells within the E9.5 yolk sac. On the right panel, summary data of multiple experiments (n = 8) analyzing the yolk sacs of Flk1+Cre;Rosa26R-EYFP mice. Numbers indicate the percentage of Ter119+ and Mac1+ cells that are either EYFP− or EYFP+, respectively. The bars represent SD of the mean percentage of total Ter119+ and Mac1+ cells, respectively. (H) Transverse section through an E9.5 embryo. LPC indicates left pericardial-peritoneal cavity; LVV, left vitelline vein; NT, neural tube; RPC right pericardial-peritoneal cavity; and RVV, right viteline vein. (H′) Magnification of region containing paired dorsal aorta demonstrating uniformity of LacZ+ blood cells in the embryonic circulation. (A-H') For whole mount embryo images, embryos were bathed in 1× PBS and photographed with an Olympus (Center Valley, PA) DP25 camera attached to an Olpmpus BH-2 dissecting microscope at either 25× or 63× magnification. The same camera was used with an Olympus BX-51 upright microscope to document sectioned embryos with either 40× or 90× oil immersion lenses. Images were captured with Olympus DP2-BSW software and processed with Adobe Photoshop CS 10.0.1.

Figure 2

An Flk-1+ origin for blood cells of adult Flk1+/Cre;Rosa26R-EYFP mice. (A) Representative FACS plots of BM staining for the hematopoietic marker CD45 (y-axis) and EYFP (x-axis) to assess the origin of hematopoietic cells within the BM of 3-month-old Flk1+/Cre ;Rosa26R-EYFP mice. (B) Summary data of multiple experiments analyzing BM of Flk1+/Cre ;Rosa26R-EYFP mice. Numbers above bars indicate percentage of CD45+ cells that are either EYFP+ or EYFP−. The bars represent SD of the mean percentage of total CD 45+ cells.(C) Representative FACS plots of PB staining for the hematopoietic marker CD45 (y-axis) and EYFP (x-axis) to assess the origin of hematopoietic cells within the PB. Individual lineage markers were also assessed to examine if all mature blood lineages are indeed Flk-1+ in origin. Hematopoietic lineages analyzed include CD4 and CD8, T cells; B220, B cells; Gr1, granulocytes; and Mac1, macrophages. (D) Summary data of multiple experiments (n = 4) analyzing PB of Flk1+Cre;Rosa26R-EYFP mice. Numbers above bars indicate percentage of CD45+ cells that are either EYFP− or EYFP+, respectively. The bars represent SD of the mean percentage of total CD45+ cells.

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Both primitive and definitive blood cells are derived from Flk-1+ mesoderm - PubMed (original) (raw)