Pericytes: Cell biology and pathology

Pericytes are perivascular cells with multifunctional activities which are now being elucidated. The functional interaction of pericytes with endothel ial cells IEC) is now being established, using current molecular and cytoch emical techniques. The detailed morphology of the pericyte has been well de scribed, Pericytes extend long cytoplasmic processes over the surface of th e EC, the two cells making interdigitating contacts. At points of contact, communicating gap junctions, tight junctions and adhesion plaques are prese nt. Pericytes appear to show both structural and functional heterogeneity. The coverage of EC by pericytes varies considerably between different micro vessel types and the location of pericytes on the microvessel is not random but appears to be functionally determined. Interaction between pericytes a nd EC is important for the maturation, remodelling and maintenance of the v ascular system via the secretion of growth facto rs or modulation of the ex tracellular matrix. There is also evidence that pericytes are involved in t he transport across the blood-brain barrier and the regulation of vascular permeability. The long-standing view that pericytes are the microvessel equ ivalent of larger vessel smooth muscle cells and are contractile is being r eassessed using current methods. An important role for pericytes in patholo gy, and neuropathology in particular, has been indicated in hypertension, d iabetic retinopathy, Alzheimer's disease, multiple sclerosis and CNS tumour formation. Copyright (C) 2001 S.Karger AG, Basel.