Expression of mRNA for molecules that regulate angiogenesis, endothelial cell survival, and vascular permeability is altered in endothelial cells isolated from db/db mouse hearts

Metabolic Syndrome (MetS) is a condition that includes symptoms such as obesity, hyperglycemia, and hypertension, which elevate the cardiovascular risk. An impaired angiogenic response of endothelial cells (ECs) in heart and peripheral organs has been proposed in MetS, but the mechanisms of this phenomenon have not been explored. Results obtained from evaluating the whole myocardium are inconsistent, since different types of cells react differently to MetS environment. Therefore, the aim of this paper is to study the VEGF/VEGFR molecular pathway, which regulates an angiogenic response and microvascular permeability in ECs isolated from db/db mouse hearts. The expression of mRNAs for VEGF/VEGFR axis proteins was assessed with RT-PCR in ECs isolated from control and db/db mouse myocardium. The density of CD31-, VEGFR2-, and VE-cadherin-positive cells was examined with confocal microscopy, and the ultrastructure of ECs was analyzed with transmission electron microscopy. The aortic ring assay was used to assess the capacity of ECs to respond to angiogenic stimuli. Our results showed a decreased number of microvessels, diminished expression of VE-cadherin and VEGFR2 and widened gaps between the ECs of microcapillaries, although the levels of mRNA for VEGF/VEGFR axis proteins were elevated. The aortic ring assay showed a diminished number of sprouts in db/db mice compared with that in controls. These results may indicate that ECs in MetS enhance the production of mRNA for VEGF/VRGFR axis proteins, yet sprout formation and vascular barrier maintenance are limited. These novel data may provide a foundation for further studies on cardiac angiogenesis in MetS.