Particle Exclusion Assay: A Tool for Measuring Hyaluronan Pericellular Matrix.

Hyaluronan (HA) is the most abundant glycosaminoglycan in the extracellular matrix, and its deposition is strictly related to changes in cellular behaviors, such as cell migration, proliferation, and adhesion. Pericellular HA is abundant in a variety of cell types, and its amount could reflect specific conditions, thus suggesting a particular cellular status.Particle exclusion assay is a useful tool to visualize pericellular matrices with a high HA content, simply employing microscope image analysis. This approach is quick and allows to visualize the presence of a clear pericellular region around single cells, where fixed red blood cells are excluded if the pericellular matrix has been deposited.

Hyaluronan in pathophysiology of vascular diseases: specific roles in smooth muscle cells, endothelial cells, and macrophages.

One of the main components of the extracellular matrix (ECM) of blood vessels is hyaluronic acid or hyaluronan (HA). It is a ubiquitous polysaccharide belonging to the family of glycosaminoglycans, but, differently from other proteoglycan-associated glycosaminoglycans, it is synthesized on the plasma membrane by a family of three HA synthases (HAS). HA can be released as a free polymer in the extracellular space or remain associated with the plasma membrane in the pericellular space via HAS or HA-binding proteins. Several cell surface proteins can interact with HA working as HA receptors, like CD44, RHAMM, and LYVE-1. In physiological conditions, HA is localized in the glycocalyx and the adventitia where it is responsible for the loose and hydrated vascular structure favoring flexibility and allowing the stretching of vessels in response to mechanical forces. During atherogenesis, ECM undergoes dramatic alterations that have a crucial role in lipoprotein retention and in triggering multiple signaling cascades that induce the cells to exit from their quiescent status. HA becomes highly present in the media and neointima favoring smooth muscle cells dedifferentiation, migration, and proliferation that strongly contribute to vessel wall thickening. Furthermore, HA is able to modulate immune cell recruitment both within the vessel wall and on the endothelial cell layer. This review is focused on deeply analyzing the effects of HA on vascular cell behavior.