Submicroscopic changes of cortical capillary pericytes in human perifocal brain edema.

Human brain capillary pericytes were studied by electron microscopy. Cortical biopsies from 17 patients with brain edema associated to brain trauma, tumors and congenital malformations were analysed. The data obtained in this study showed that pericytes like endothelial cells exhibited remarkable edematous changes, increased vacuolar and vesicular transport, formation of transient transpericytal channels and tubular structures, demonstrating pericyte brain barrier dysfunction. Images of normal and contracted pericytes showing shallow and deep nuclear invaginations, nuclear basal lamina, actin and myosin-like filaments and coupled interaction with endothelial cells through macula occludens were also encountered. Some pericytes displayed hypertrophic and necrotic changes. Phagocytic pericytes exhibited ingested erythrocytes. Hypertrophic pericytes inducing basement membrane splitting and degenerated pericytes with lacunar enlargement of endoplasmic reticulum, deposit of dense osmiophilic bodies and glycogen granules, vacuolization, hydropic changes of Golgi apparatus, and pleomorphic mitochondria were also found. Certain micropinocytotic vesicles seem to be orientated to multivesicular bodies suggesting that pericytes might play some role in edema resolution. Evidence of pericyte transformation into microglial cells or division into phagocytic cells and pericyte migration were not found.