Ultrastructure of endothelial cells under flow alteration

Area of Science:

• Vascular Biology
• Cellular Physiology
• Hemodynamics

Background:

• Endothelial cells maintain vascular homeostasis under normal physiological blood flow.
• Altering blood flow dynamics can disrupt endothelial cell equilibrium.
• Understanding endothelial cell responses to flow changes is crucial for vascular health.

Purpose of the Study:

• To investigate endothelial cell behavior under conditions of altered blood flow.
• To characterize the ultrastructural changes associated with endothelial cell activation and inactivation.
• To explore the relationship between flow alteration and vascular remodeling processes.

Main Methods:

• Observation of endothelial cells in arteries with arteriovenous fistulas and myocardial/skeletal muscle capillaries under varied flow conditions.
• Induction of increased flow via fistulas or electrical stimulation.
• Induction of decreased flow by fistula closure or cessation of stimulation.
• Analysis of endothelial cell ultrastructure, including lumen and abluminal features, and basement membrane and elastic lamina integrity.

Main Results:

• Increased blood flow activated endothelial cells, leading to lumen protrusions, increased organelles, abluminal protrusions, and degradation of basement membrane and internal elastic lamina.
• In capillaries, increased flow induced sproutings, comparable to angiogenesis.
• Decreased blood flow resulted in endothelial inactivation, characterized by apoptosis and a decrease in cell number, comparable to angioregression.

Conclusions:

• Endothelial cells exhibit distinct responses to altered blood flow, with activation under high flow and inactivation under low flow.
• Increased flow stimulates processes akin to angiogenesis, while decreased flow promotes angioregression.
• These findings highlight the role of hemodynamic forces in regulating endothelial cell fate and vascular remodeling.