Endothelial Progenitors Exist within the Kidney and Lung Mesenchyme

• Published in: PloS one 2013-06, Vol.8 (6), p.e65993-e65993
• Main Authors: Sims-Lucas, Sunder, Schaefer, Caitlin, Bushnell, Daniel, Ho, Jacqueline, Logar, Alison, Prochownik, Edward, Gittes, George, Bates, Carlton M
• Format: Article
• Language: English
• Subjects: Angiogenesis; Animals; Biology; Biomarkers - metabolism; Blood vessels; Cancer; Cell Differentiation; Cell Separation; Embryogenesis; Embryonic growth stage; Endocytosis; Endothelial cells; Endothelial Progenitor Cells - cytology; Endothelial Progenitor Cells - metabolism; Endothelium; Fibroblasts; Flow Cytometry; Fluorescence; Forkhead Transcription Factors - metabolism; Heterogeneity; Hospitals; Immunofluorescence; Immunohistochemistry; Kidney - cytology; Kidney - metabolism; Kidneys; Lipoproteins; Low density lipoprotein; Low density lipoproteins; Lung - cytology; Lung - metabolism; Lungs; Markers; Medicine; Mesenchyme; Mesoderm - cytology; Mesoderm - metabolism; Mice; Muscles; Nephrology; Organs; Pathology; Pediatrics; Pericytes; Physicians; Physiology; Residential density; Rodents; Smooth muscle; Stem cells; Stroma; Thoracic surgery
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0065993

The renal endothelium has been debated as arising from resident hemangioblast precursors that transdifferentiate from the nephrogenic mesenchyme (vasculogenesis) and/or from invading vessels (angiogenesis). While the Foxd1-positive renal cortical stroma has been shown to differentiate into cells that support the vasculature in the kidney (including vascular smooth muscle and pericytes) it has not been considered as a source of endothelial cell progenitors. In addition, it is unclear if Foxd1-positive mesenchymal cells in other organs such as the lung have the potential to form endothelium. This study examines the potential for Foxd1-positive cells of the kidney and lung to give rise to endothelial progenitors. We utilized immunofluorescence (IF) and fluorescence-activated cell sorting (FACS) to co-label Foxd1-expressing cells (including permanently lineage-tagged cells) with endothelial markers in embryonic and postnatal mice. We also cultured FACsorted Foxd1-positive cells, performed in vitro endothelial cell tubulogenesis assays and examined for endocytosis of acetylated low-density lipoprotein (Ac-LDL), a functional assay for endothelial cells. Immunofluorescence and FACS revealed that a subset of Foxd1-positive cells from kidney and lung co-expressed endothelial cell markers throughout embryogenesis. In vitro, cultured embryonic Foxd1-positive cells were able to differentiate into tubular networks that expressed endothelial cell markers and were able to endocytose Ac-LDL. IF and FACS in both the kidney and lung revealed that lineage-tagged Foxd1-positive cells gave rise to a significant portion of the endothelium in postnatal mice. In the kidney, the stromal-derived cells gave rise to a portion of the peritubular capillary endothelium, but not of the glomerular or large vessel endothelium. These findings reveal the heterogeneity of endothelial cell lineages; moreover, Foxd1-positive mesenchymal cells of the developing kidney and lung are a source of endothelial progenitors that are likely critical to patterning the vasculature.