Affiliation:
1. Departments of 1Physiology and
2. Cardiac Surgery, University of Munich, Munich;
3. Department of Cardiac Surgery, Hospital Nuremberg South, Nuremberg, Germany
4. Department of Transfusion Medicine and Hemostaseology, University of Erlangen-Nuremberg, Erlangen; and
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 ( LP = 3.24 ± 0.52·10−8cm·s−1·cmH2O−1) and a high selectivity index for transmural passage of albumin (SIAlb = 0.95 ± 0.02). In contrast, LP and SIAlb in the PCV model (almost no ECM) were 2.55 ± 0.32·10−7cm·s−1·cmH2O−1 and 0.88 ± 0.03, respectively, in PLM, and 1.39 ± 0.10·10−6cm·s−1·cmH2O−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.
Publisher
American Physiological Society
Subject
Physiology (medical),Cardiology and Cardiovascular Medicine,Physiology
Cited by
17 articles.
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