Pericytes as an Essential Cellular Element in Transwell Blood–Brain Barrier Models In Vitro

This study aimed to demonstrate the advantage of a four-cell model of the blood–brain barrier (BBB) in vitro in comparison with the traditional three-cell model, as well as the influence of pericytes on the phenotype of endothelial cells. This paper describes a method for co-culture of primary brain microvascular endothelial cells, pericytes, astrocytes, and neurons in the Transwell BBB model in vitro . A quantitative analysis was carried out between the values of transendothelial electrical resistance (TEER), as well as between the content of endothelial cell tight junction markers in three- and four-cell Transwell models of the BBB. According to the obtained data, the presence of pericytes is accompanied by higher TEER values and a higher content of tight junction proteins. The presented results are consistent with the world scientific literature and confirm the hypothesis that pericytes not only perform a supporting function for endothelial cells, but are also an important metabolic link that regulates the barrier functions of the BBB. Thus, co-culture of cells of the neurovascular unit (NVU) of the brain with pericytes is necessary for the formation of a phenotype in endothelial cells that is close to the conditions in the NVU microenvironment in vivo.