Do microglia arise from pericytes? An ultrastructural and distribution study in the rat cerebellar cortex

Both pericytes and microglia are dark cells that may present similar ultrastructure as well as organization of the rough endoplasmic reticulum cisternae; in addition, images that suggest pericytes being released from the basal lamina compartment, some of them looking like forms of perivascular microglia, may be found. Anatomical articulations between pericytes and microglia are observed. A distribution analysis reveals that, in the considered five neocerebellar cortical strata, the percentage of pericytes preponderates over the percentage of microglia; furthermore, there is a highly statistically significant linear trend between the percentages of pericytes and of microglia in connection with their distribution along the cortical strata. This study suggests that, in rat cerebellar cortex, microglia may arise from pericytes. It is also hypothesized that astroglia have an active role in releasing pericytes from the vascular wall.