AFM-based detection of glycocalyx degradation and endothelial stiffening in the db/db mouse model of diabetes

Marta Targosz-Korecka, Magdalena Jaglarz, Katarzyna E. Malek-Zietek, Aleksandra Gregorius, Agnieszka Zakrzewska, Barbara Sitek, Zenon Rajfur, Stefan Chlopicki, Marek Szymonski
2017 Scientific Reports  
Degradation of the glycocalyx and stiffening of endothelium are important pathophysiological components of endothelial dysfunction. However, to our knowledge, these events have not been investigated in tandem in experimental diabetes. Here, the mechanical properties of the glycocalyx and endothelium in ex vivo mouse aorta were determined simultaneously in indentation experiments with an atomic force microscope (AFM) for diabetic db/db and control db/+ mice at ages of 11-19 weeks. To analyze
more » ... ly heterogeneous aorta samples, we developed a tailored classification procedure of indentation data based on a bi-layer brush model supplemented with Hertz model for quantification of nanomechanics of endothelial regions with and without the glycocalyx surface. In db/db mice, marked endothelial stiffening and reduced glycocalyx coverage were present already in 11-week-old mice and persisted in older animals. In contrast, reduction of the effective glycocalyx length was progressive and was most pronounced in 19-week-old db/db mice. The reduction of the glycocalyx length correlated with an increasing level of glycated haemoglobin and decreased endothelial NO production. In conclusion, AFM nanoindentation analysis revealed that stiffening of endothelial cells and diminished glycocalyx coverage occurred in early diabetes and were followed by the reduction of the glycocalyx length that correlated with diabetes progression. The endothelium is a heterogeneous organ that maintains cardiovascular homeostasis 1-4 . From a morphological viewpoint, the endothelium consists of a monolayer of endothelial cells that lines the internal lumen of blood vessels. Importantly, the endothelium has a unique ability to convert mechanical stress induced by blood flow into biochemical responses, in particular, into the release of NO, the main vasodilator and an important vasoprotective molecule 5,6 . This unique feature of the endothelium is strongly related to the nanomechanical properties of the endothelial cells, in particular, to endothelial stiffness and the structural integrity of the glycocalyx layer. As shown by Fels et al. 7 , soft endothelial cells are more sensitive to shear stimulation than stiff cells and consequently produce more NO. NO influences vascular smooth muscle cells and causes vasodilation 8 . In endothelial dysfunction, endothelial cells stiffen, which impairs the vasodilation mechanism and leads to arterial stiffness and, consequently, hypertension 9,10 . The endothelial glycocalyx has an important role in endothelial physiology. The glycocalyx is a brush-like surface layer of proteoglycans and glycoproteins that covers the luminal side of the endothelium 11 . It interacts directly with blood flow and plays important roles in endothelial mechanotransduction 12 as well as in the modulation of vascular permeability 13 and the regulation of hemostasis 14 . Diabetes is associated with a number of macro and microvascular complications that are pathophysiologically linked with the development of endothelial dysfunction 15-17 . The high glucose concentration in blood
doi:10.1038/s41598-017-16179-7 pmid:29162916 pmcid:PMC5698475 fatcat:woed63p4onfrlopawr3zw6rtou