Endothelial Cells May Have Tissue-Specific Origins

Abstract

Endothelial heterogeneity reflects many functions performed by endothelial cells (ECs) in various tissues. However, the origin of this heterogeneity is unclear. Here, we report that tissue-specific ECs in lungs, brain and liver co-expressed the lineage markers of their coordinating tissue-specific cells at very early stages. Specifically, we found that the pulmonary EC population was significantly suppressed after pulmonary epithelial-specific (Nkx2.1-Cre mediated) deletion of fetal liver kinase-1 (Flk1). Together, the results suggest that tissues-specific ECs may originate from the same progenitor cells as tissue-specific cells.

Keywords: Differentiation; Endothelial cells; Heterogeneity; Tissue-specific.

Figure 1. Pulmonary ECs expressing Nkx2.1 in early developmental stages

(a-b) Co-expression of Nkx2.1 with Flk1 (a) or CD31 (b) in E10.5 embryonic lungs of wild type mice, as shown by immunostaining. Top: low magnification. Scale bar, 100μm. Bottom: high magnification. Scale bar, 50μm. (c) E10.5 embryonic lungs of wild type mice were enzymatically dispersed and analyzed by using flow cytometry. (d) Expression of Flk1 in E10.5 embryonic lungs of Nkx2.1^CreFlk1^wt/wt and Nkx2.1^CreFlk1^flox/wt mice. (e) E10.5 embryonic lungs of Nkx2.1^Creflk1^wt/wt and Nkx2.1^Creflk1^flox/wt were enzymatically dispersed. The VE-cadherin positive EC population was analyzed by using flow cytometry. (f) Expression of Cd31, von Willebrand factor (vWF) and Tie2 in E10.5 embryonic lungs of Nkx2.1^CreFlk1^wt/wt and Nkx2.1^CreFlk1^flox/wt mice.

Figure 2. Co-expression of Nkx2.1 with Flk1 and Flt1 in embryonic lung

(a-b) Co-expression of Nkx2.1 with Flk1 (a) or Flt1 (b) in embryonic lung from E11.5 to E18.5. Scale bar, 100μm. (c) Percentage of Nkx2.1 and Flk1 or Nkx2.1 and Flt1 double positive cells in embryonic lung from E11.5 to E18.5. Embryos, n=4; High-power fields per assessment, n=5.

Figure 3. Brain ECs expressing Sox2 at early developmental stages

(a) Expression of Sox2 and Flk1 in E10.5 (top), E14.5 (middle) and E18.5 (bottom) embryonic brains of wild type mice, as shown by immunostaining. Scale bar, 50μm. (b) E12.5 embryonic brains of wild type mice were enzymatically dispersed and analyzed by using flow cytometry.

Figure 4. Hepatic ECs expressing Gata4 at early developmental stages

(a) Expression of Gata4 and Flk1 in E10.5 (top), E14.5 (middle) and E18.5 (bottom) embryonic livers of wild type mice, as shown by immunostaining. Scale bar, 50μm. (b) E12.5 embryonic livers of wild type mice were enzymatically dispersed and analyzed by using flow cytometry.