title: Wall structures of myocardial precapillary arterioles and postcapillary venules reexamined and reconstructed in vitro for studies on barrier functions.
abstract: The barrier functions of myocardial precapillary arteriolar and postcapillary venular walls (PCA or PCV, respectively) are of considerable scientific and clinical interest (regulation of blood flow and recruitment of immune defense). Using enzyme histochemistry combined with confocal microscopy, we reexamined the cell architecture of human PCA and PVC and reconstructed appropriate in vitro models for studies of their barrier functions. Contrary to current opinion, the PCA endothelial tube is encompassed not by smooth muscle cells but rather by a concentric layer of pericytes cocooned in a thick, microparticle-containing extracellular matrix (ECM) that contributes substantially to the tightness of the arteriolar wall. This core tube extends upstream into the larger arterioles, there additionally enwrapped by smooth muscle. PCV consist of an inner layer of large, contractile endothelial cells encompassed by a fragile, wide-meshed pericyte network with a weakly developed ECM. Pure pericyte and endothelial cell preparations were isolated from PCA and PCV and grown in sandwich cultures. These in vitro models of the PCA and PCV walls exhibited typical histological and functional features. In both plasma-like (PLM) and serum-containing (SCM) media, the PCA model (including ECM) maintained its low hydraulic conductivity (L(P) = 3.24 ± 0.52·10(-8)cm·s(-1)·cmH(2)O(-1)) and a high selectivity index for transmural passage of albumin (SI(Alb) = 0.95 ± 0.02). In contrast, L(P) and SI(Alb) in the PCV model (almost no ECM) were 2.55 ± 0.32·10(-7)cm·s(-1)·cmH(2)O(-1) and 0.88 ± 0.03, respectively, in PLM, and 1.39 ± 0.10·10(-6)cm·s(-1)·cmH(2)O(-1) and 0.49 ± 0.04 in SCM. With the use of these models, systematic, detailed studies on the regulation of microvascular barrier properties now appear to be feasible.
authors: Department of Physiology, University of Munich, Germany. stephan.nees@lrz.uni-muenchen.de
authors: Stephan
authors: S
authors: Nees
authors: Gerd
authors: G
authors: Juchem
authors: Nicola
authors: N
authors: Eberhorn
authors: Martin
authors: M
authors: Thallmair
authors: Stefan
authors: S
authors: Förch
authors: Maria
authors: M
authors: Knott
authors: Anton
authors: A
authors: Senftl
authors: Theodor
authors: T
authors: Fischlein
authors: Bruno
authors: B
authors: Reichart
authors: Dominik R
authors: DR
authors: Weiss
mesh_terms: D000418:Albumins / Q000378:metabolism; D001160:Arterioles / Q000166:cytology / Q000378:metabolism; D002199:Capillary Permeability; D002469:Cell Separation; D002478:Cells, Cultured; D018920:Coculture Techniques; D003331:Coronary Vessels / Q000166:cytology / Q000378:metabolism*; D003470:Culture Media; D004553:Electric Conductivity; D042783:Endothelial Cells / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D020286:Pericytes / Q000378:metabolism*; D013997:Time Factors; D014699:Venules / Q000166:cytology / Q000378:metabolism
chemical_list: D000418:Albumins; D003470:Culture Media