Endothelial Progenitors Exist within the Kidney and Lung Mesenchyme

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.

[1]  J. Duffield,et al.  Pericyte-Like Cells And Resident Fibroblasts Are Sources Of Myofibroblasts In Acute Lung Injury , 2012, ATS 2012.

[2]  M. S. Sequeira Lopez,et al.  Development of the renal arterioles. , 2011, Journal of the American Society of Nephrology : JASN.

[3]  D. Potoka,et al.  Embryonic mouse blood flow and oxygen correlate with early pancreatic differentiation. , 2011, Developmental biology.

[4]  E. Prochownik,et al.  Endothelial‐like cells derived directly from human tumor xenografts , 2010, International journal of cancer.

[5]  V. Kouskoff,et al.  Blood cell generation from the hemangioblast , 2010, Journal of Molecular Medicine.

[6]  Allan R. Jones,et al.  A robust and high-throughput Cre reporting and characterization system for the whole mouse brain , 2009, Nature Neuroscience.

[7]  William C. Aird,et al.  Phenotypic Heterogeneity of the Endothelium: I. Structure, Function, and Mechanisms , 2007, Circulation research.

[8]  W. Aird.  Phenotypic Heterogeneity of the Endothelium: II. Representative Vascular Beds , 2007, Circulation research.

[9]  S. Kattman,et al.  Multipotent flk-1+ cardiovascular progenitor cells give rise to the cardiomyocyte, endothelial, and vascular smooth muscle lineages. , 2006, Developmental cell.

[10]  W. Aird.  Mechanisms of endothelial cell heterogeneity in health and disease. , 2006, Circulation research.

[11]  D. Abrahamson,et al.  Embryonic origin and lineage of juxtaglomerular cells. , 2001, American journal of physiology. Renal physiology.

[12]  R Folberg,et al.  Vasculogenic mimicry and tumor angiogenesis. , 2000, The American journal of pathology.

[13]  P. Meltzer,et al.  Vascular channel formation by human melanoma cells in vivo and in vitro: vasculogenic mimicry. , 1999, The American journal of pathology.

[14]  P. S. St. John,et al.  Origins and formation of microvasculature in the developing kidney. , 1998, Kidney international. Supplement.

[15]  P. S. St. John,et al.  Direct visualization of renal vascular morphogenesis in Flk1 heterozygous mutant mice. , 1998, American journal of physiology. Renal physiology.

[16]  D. Sawyer,et al.  Early fetal development of lung vasculature. , 1997, American journal of respiratory cell and molecular biology.

[17]  D. Tucker,et al.  Endogenous origin of glomerular endothelial and mesangial cells in grafts of embryonic kidneys. , 1996, The American journal of physiology.

[18]  R. Blomhoff,et al.  Endocytosis of acetylated low-density lipoprotein, endothelial cell-modified low-density lipoprotein, and formaldehyde-treated serum albumin by rat liver endothelial cells. Evidence of uptake via a common receptor. , 1987, Scandinavian journal of gastroenterology.

[19]  B. Zetter,et al.  Identification and isolation of endothelial cells based on their increased uptake of acetylated-low density lipoprotein , 1984, The Journal of cell biology.

[20]  A. McMahon,et al.  Fate tracing reveals the pericyte and not epithelial origin of myofibroblasts in kidney fibrosis. , 2010, The American journal of pathology.