Pericytes in human cerebral microvasculature

Abstract

Two classes of pericytes are thought to exist in cerebral microvasculature, granular and agranular. This classification is based on the presence or absence of cytoplasmic, lysosome‐like granules of variable size and appearance. The pericytes in structurally normal human brain tissue from 17 patients, male and female, ranging in age from 14 to 77, were examined. Light microscopic examination of single sections revealed that 67% of pericyte profiles contained granules in both sexes, and this ratio did not change with age. Following the serial reconstructions of 80 individual pericytes, it was found that all contained characteristic cytoplasmic granules. These data show that if truly agranular pericytes do exist in human cerebral microvasculature, they must constitute less than 5% of the population.