Focus on cardiac pericytes.

The wall of myocardial terminal vessels, consisting of a continuous endothelial tube with an adventitial coat of pericytes in their extracellular matrix, constitutes a remarkably tight barrier to solute transport between the blood and the parenchyma. This constructional principle of precapillary arterioles, capillaries and postcapillary venules extends both up- and downstream into the arterial and venous limbs, where the original microvessel tube widens and becomes the innermost layer-the intima-of all the larger coronary vessels. In the myocardium's smallest functional units and in the intima of the coronaries, the pericytes play key roles by virtue of both their central histological localization and their physiological functions.

Regulation of coronary venular barrier function by blood borne inflammatory mediators and pharmacological tools: insights from novel microvascular wall models.

We hypothesized that postcapillary venules play a central role in the control of the tightness of the coronary system as a whole, particularly under inflammatory conditions. Sandwich cultures of endothelial cells and pericytes of precapillary arteriolar or postcapillary venular origin from human myocardium as models of the respective vascular walls (sandwich cultures of precapillary arteriolar or postcapillary venular origin) were exposed to thrombin and components of the acutely activatable inflammatory system, and their hydraulic conductivity (L(P)) was registered. L(P) of SC-PAO remained low under all conditions (3.

Isolation, bulk cultivation, and characterization of coronary microvascular pericytes: the second most frequent myocardial cell type in vitro.

Densely arranged pericytes engird the endothelial tube of all coronary microvessels. Since the experimental access to these abundant cells in situ is difficult, a prerequisite for broader investigation is the availability of sufficient numbers of fully differentiated pericytes in homogenous culture. To reach this goal, we applied strictly standardized cell isolation techniques, optimized culture methods and specific histological staining.

Wall structures of myocardial precapillary arterioles and postcapillary venules reexamined and reconstructed in vitro for studies on barrier functions.

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.

Search for optimized conditions for sealing and storage of bypass vessels: influence of preservation solution and filling pressure on the degree of endothelialization.

The aim of the present study was to develop methods for the rapid assessment of intimal quality of coronary bypass segments of venous origin, and to prevent endothelial damage by improved intraoperative handling of graft segments. Particular attention was paid to the influence of the composition of the preservation solution and the intravasal filling pressure on the degree of endothelialization. Intrava-sal exposure to Alcian blue at pH<3 resulted in highly specific staining of intimal regions with functionally or structurally damaged endothelium.

Pericytes in the macrovascular intima: possible physiological and pathogenetic impact.

The frequently observed de-endothelialization of venous coronary bypass grafts prepared using standard methods exposes subendothelial prothrombotic cells to blood components, thus endangering patients by inducing acute thromboembolic infarction or long-term proliferative stenosis. Our aim was to gain deeper histological and physiological insight into these relations. An intricate network of subendothelial cells, characterized by histological features specific for true pericytes, was detected even in healthy vessels and forms, coupled to the luminal endothelium, a second leaflet of the macrovascular intima.

Extensive deendothelialization and thrombogenicity in routinely prepared vein grafts for coronary bypass operations: facts and remedy.

The objective of this study was to gain deeper insight into the early reasons for saphenous vein graft disease and to find a practical approach to obviate it. Intraoperative storage of freshly explanted venous grafts (45 min, 20 degrees C; n=25 in each case) in saline, saline + 5% albumin, or HTK-solution and also in heparinized autologous blood was poorly tolerated by the endothelium. Large endothelial areas (mostly >75% of total surface) were detached already during brief non-pulsatile flushing just before the transplantation.

Protective effects of flavonoids contained in the red vine leaf on venular endothelium against the attack of activated blood components in vitro.

New methods are described that allow the selective isolation of venular endothelial cells and their cultivation on porous filters to confluent monolayers. These filters with the attached endothelial cell layer can be mounted in a specially adapted apparatus allowing not only blood filtration studies, but now also the continuous registration of hydraulic conductivity (Lp) of tissue layers. This preparation responds dramatically to certain release products from simultaneously activated blood platelets and polymorphonuclear granulocytes (PMN) with a rise in Lp that, in situ, would lead rapidly to local oedema, arteriolar constriction and venular thrombosis.