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A. Armulik investigated how pericytes regulate the blood-brain barrier. In the 2010 mouse study, pericyte-deficient mutants showed increased passage of tracers across brain vessels. The increased permeability involved endothelial transcytosis; the study also linked pericytes to endothelial gene-expression patterns and polarization of astrocyte end-feet.^[ref]

This makes an important mechanistic distinction: a barrier depends on regulated transport through cells as well as seals between cells. Measuring tracer escape and identifying the route of escape answer different experimental questions. The primary paper identifies the author as Annika Armulik.