Mark Chandy1,2,3, Edward Lau1, Ian Chen1, Chun Liu1, Brad Oh1, Mansoor Husain2,3,4, Nazish Sayed1, Shriram Nallamshetty1, Joseph C. Wu1
1 Cardiovascular Institute, Stanford University, CA; 2 Heart and Stroke Richard Lewar Centre of Excellence, University of Toronto, Toronto, Canada; 3 McEwen Centre for Regenerative Medicine, Toronto General Hospital Research Institute, Toronto, Canada; 4 Ted Rogers Centre for Heart Research, University of Toronto, Toronto, Canada
Background: Cardiovascular disease (CVD) is the number one cause of death globally, with 17.5 million deaths per year. Insulin resistance is a precursor to type 2 diabetes and patients with this condition are more likely to develop CVD. The genetic causes of insulin resistance and effects on the vascular system are poorly understood. Our goal is to elucidate the molecular mechanisms of how insulin resistance causes vascular dysfunction using patient-specific induced pluripotent stem cells (iPSCs) differentiated into endothelial cells. Unlike previous models, iPSC-derived endothelial cells (iPSC-EC) are ideal because they generate abundant patient-specific tissue sample.
Hypothesis: iPSC-EC derived from patients with insulin resistance are dysfunctional
Methods & Results: Insulin resistant and control patient peripheral blood mononuclear cells were reprogrammed into iPSCs and subsequently differentiated into endothelial cells as confirmed by qPCR and flow cytometry. iPSC-EC stimulation with tumour necrosis factor TNFɑ was used to model insulin resistance. When treated with TNFɑ, iPSC-EC had increased cell adhesion molecule expression and dysfunctional insulin signaling, implying endothelial dysfunction and genes involved in the insulin signaling were downregulated. At baseline, iPSC-EC derived from insulin resistant patients had increased endothelial nitric oxide synthetase (eNOS) expression and phosphorylation and paradoxically, stimulation with insulin did not increase eNOS phosphorylation, suggesting endothelial dysfunction may be caused by an abnormality in this pathway. Indeed, insulin resistant iPSC-EC have a relative impairment of NO release, impaired angiogenesis and increased reactive oxygen species production under conditions of hyperglycemia and inflammation mimicked by TNFɑ.
Conclusion: iPSC endothelial cells model insulin resistance and endothelial dysfunction. eNOS expression and endothelial cell function is abnormal in insulin resistant patients. The underlying mechanisms merits further investigation.
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