title: Contractile proteins in pericytes at the blood-brain and blood-retinal barriers.
abstract: Evidence from a variety of sources suggests that pericytes have contractile properties and may therefore function in the regulation of capillary blood flow. However, it has been suggested that contractility is not a ubiquitous function of pericytes, and that pericytes surrounding true capillaries apparently lack the machinery for contraction. The present study used a variety of techniques to investigate the expression of contractile proteins in the pericytes of the CNS. The results of immunocytochemistry on cryosections of brain and retina, retinal whole-mounts and immunoblotting of isolated brain capillaries indicate strong expression of the smooth muscle isoform of actin (alpha-SM actin) in a significant number of mid-capillary pericytes. Immunogold labelling at the ultrastructural level showed that alpha-SM actin expression in capillaries was exclusive to pericytes, and endothelial cells were negative. Compared to alpha-SM actin, non-muscle myosin was present in lower concentrations. By contrast, smooth muscle myosin isoforms, were absent. Pericytes were strongly positive for the intermediate filament protein vimentin, but lacked desmin which was consistently found in vascular smooth muscle cells. These results add support for a contractile role in pericytes of the CNS microvasculature, similar to that of vascular smooth muscle cells.
authors.affiliation: Weston Institute of Neurological Studies, Windeyer Building, University College Medical School, Cleveland Street, London W1P 6DB, UK.
authors.forename: R
authors.initials: R
authors.lastname: Bandopadhyay
authors.forename: C
authors.initials: C
authors.lastname: Orte
authors.forename: J G
authors.initials: JG
authors.lastname: Lawrenson
authors.forename: A R
authors.initials: AR
authors.lastname: Reid
authors.forename: S
authors.initials: S
authors.lastname: De Silva
authors.forename: G
authors.initials: G
authors.lastname: Allt
mesh_terms: D000199:Actins / Q000032:analysis; D000818:Animals; D001812:Blood-Brain Barrier / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000032:analysis; D003285:Contractile Proteins / Q000032:analysis*; D003599:Cytoskeleton; D003893:Desmin / Q000032:analysis; D007124:Immunoenzyme Techniques; D008297:Male; D008833:Microcirculation; D008840:Microfilament Proteins; D016253:Microscopy, Immunoelectron; D020286:Pericytes / Q000737:chemistry* / Q000648:ultrastructure; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012171:Retinal Vessels / Q000737:chemistry / Q000166:cytology; D024745:Smooth Muscle Myosins / Q000032:analysis; D014746:Vimentin / Q000032:analysis; D000096985:Calponins
chemical_list: D000199:Actins; D002135:Calcium-Binding Proteins; D003285:Contractile Proteins; D003893:Desmin; D008840:Microfilament Proteins; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D024745:Smooth Muscle Myosins; D014746:Vimentin; D000096985:Calponins