Adipose Tissue as a Potential Source of Endothelial Cells for Vascular Tissue Engineering
Antonyshyn, Jeremy 1, 2 ; Sharifpoor, Soror 2 ; Santerre, Paul 1, 2, 3
1. Institute of Biomaterials and Biomedical Engineering, University of Toronto; 2. Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research; 3. Faculty of Dentistry, University of Toronto
Background. Endothelial cells (ECs) are crucial to the perfusion of tissue-engineered constructs. Adipose tissue is an attractive source in that it can be harvested in large quantities with minimally invasive procedures, yielding autologous cells that preclude the need for immunosuppressive medications. Two populations of cells that reside within its stromal vascular fraction warrant consideration: microvascular ECs (MVECs) and adipose-derived stem cells (ASCs).
Purpose & Hypotheses. The purpose of this investigation was to explore adipose tissue as a potential source of ECs for vascular tissue engineering. It was hypothesized that MVECs can be readily isolated from adipose tissue and that hemangioblast-like ASCs better differentiate into ECs than non-purified ASCs given the role of the hemangioblast in embryonic vasculogenesis and the mounting evidence of its persistence into postnatal life.
Materials & Methods. Adipose tissue was obtained with informed consent from patients presenting to Toronto General Hospital (Toronto, ON). The stromal vascular fraction was harvested and characterized by flow cytometry. Magnetic-activated cell sorting was used to separate populations of cells. The endothelial differentiation of ASCs was induced using EC growth medium, and was evaluated by light microscopy and reverse transcription quantitative real-time polymerase chain reaction. Human umbilical vein ECs (HUVECs) were positive controls.
Results. MVECs comprised 1.4 ± 0.6% of the stromal vascular fraction (N = 3), and exhibited a characteristic endothelial cobblestone-like morphology (N = 2). Hemangioblast-like ASCs were not detected within the stromal vascular fraction (N = 3). Non-purified ASCs demonstrated basal expression of all endothelial genes evaluated, and their differentiation resulted in their upregulation of PECAM1 and VWF (p < 0.05; N = 2). However, their expression of EC-related genes remained as much as 243,746-fold lower than that observed in HUVECs and they failed to assume a characteristic endothelial cobblestone-like morphology.
Conclusions. The failure of ASCs to assume an endothelial transcriptome and morphology suggests that MVECs are the only viable adipose tissue –resident cells for the generation of an endothelium. This investigation has identified a source of autologous ECs that can be harvested in large quantities with minimally invasive procedures for vascular tissue engineering.