Isolation and partial characterization of endothelial cell extracellular complexes

Extracellular matrix components secreted by microvascular endothelial cells stimulate preadipocyte differentiation in vitro

Paracrine interaction between preadipocytes and microvascular endothelial cells may play a role in the regulation of adipose tissue growth. We report here a study of the effect of extracellular matrix factors secreted by microvascular endothelial cells, derived from adipose tissue, on preadipocyte differentiation in primary culture. Extracellular matrix components (EC) were prepared by differential centrifugation of medium conditioned by microvascular endothelial cells (CM). Preadipocyte differentiation was assessed by enumerating cells containing Oil-Red-O-stainable neutral lipids and by assaying cellular triacylglycerol (TG) content and glycerol-3-phosphate dehydrogenase (GPDH) specific activity. Both supernatant (containing soluble components) and pelleted (containing large complexes of EC) fractions of CM stimulated preadipocyte differentiation. When the supernatant fraction was used, the proportion of cells containing visible lipid droplets was 29% +/- 3% of total preadipocytes in the presence of extracellular complexes, as compared with 6% +/- 1% under control conditions. This differentiation induction was associated with fourfold increases in TG content and GPDH specific activity. Neither the supernatant nor the pelleted fraction of EC affected the maximal differentiation induced by hormonal stimulation in serum-supplemented or serum-free media. The major EC, fibronectin, laminin, and collagen IV, had no effect on differentiation when added individually to culture medium. Collection of CM under hyperglycemic (18 mmol/L glucose) compared with control (6 mmol/L glucose) conditions reduced the stimulatory effect of extracellular complexes by twofold, suggesting decreased or altered production by endothelial cells. The present findings demonstrate that microvascular endothelial cells release EC that promote preadipocyte differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Culture of human adult endothelial cells on liquid-liquid interfaces: a new approach to the study of cell-matrix interactions

Human adult endothelial cells (ECs) were cultured on liquid-liquid interface formed when aqueous culture medium is overlaid onto a fluorocarbon solvent. When ECs were seeded on untreated interfaces, some cells seemed to attach but they did not spread or grow. In contrast, when ECs were seeded on interfaces pretreated with such proteins as collagen type IV (COL), laminin (LN), fibronectin (FN), and fibrinogen (FG) the cells spread and proliferated until they formed confluent monolayers. Proteins such as bovine serum albumin (BSA) or gelatin (GN) were not as effective in providing surfaces for vigorous growth. Cells grown on fluorocarbon interfaces expressed specialized characteristics exhibited by endothelial cells grown under the usual culture conditions; they grew in a cobblestone monolayer, stained positively for Factor VIII-related antigen, and produced angiotensin-converting enzyme. The growth rate of ECs was the same whether they were cultured on treated fluorocarbon interfaces or on the usual tissue culture plastic surfaces. Using this culture system, the interactions of ECs with various adhesive proteins used as substrata was examined. ECs were observed to attach readily to the interfaces coated with GN, COL, LN, FN, and FG, but poorly to those coated with BSA. All the substrates tested, with the exception of BSA, promoted EC growth on fluorocarbon interfaces; ECs tended to grow more rapidly on COL- or FG-coated interfaces than on LN-, FN-, or GN-coated interfaces.

A human endothelial cell membrane protein that binds Staphylococcus aureus in vitro

We have investigated S. aureus adherence to human endothelial cells utilizing an in vitro model. Staphylococcus binding to confluent endothelial cell monolayers was saturable in both dose and time response studies suggesting that the binding interaction was specific. We have developed a technique, based on the pH dependent affinity of iminobiotin for streptavidin, for the isolation of an endothelial cell membrane component that binds S. aureus, in vitro. A 50-kD membrane component was isolated and purified using this approach. This component was trypsin sensitive, periodate insensitive, and did not label with [3H]glucosamine. [35S]Methionine and [125I]iodine labeling confirmed that the protein was synthesized by and expressed on the endothelial cell surface. Functional binding studies demonstrated that staphylococci, but not endothelial cells, bound to the protein when immobilized on microtiter wells. Preincubation of staphylococci with the purified protein significantly (P less than 0.001) reduced staphylococcal binding to cultured endothelial cells. The capacity of S. aureus to colonize and invade endovascular surfaces may in part be a consequence of staphylococcal interaction with this endothelial cell membrane protein.

Extracellular matrix heparan sulfate proteoglycans modulate the mitogenic capacity of acidic fibroblast growth factor

Confluent cultures of human endothelial cells deposit into extracellular matrix (ECM) distinct heparan sulfate proteoglycans (HSPG) which modulate acidic fibroblast growth factor's (aFGF) ability to stimulate human endothelial cell mitogenic capacity. Extracellular matrix 35S-HSPG were isolated from cultures metabolically labelled with Na235SO4 by DEAE-Sepharose, Sepharose CL-4B, and aFGF-Affi-Gel 15 column chromatography and identified by resistance to chondroitinase ABC and sensitivity to nitrous acid. Fifty to sixty percent of the 35S-HSPG deposited into ECM do not bind aFGF. The bound 35S-HSGP (40-50% of the total counts applied) eluted from the aFGF-Affi-Gel column after the addition of buffer containing 2 M NaCl. aFGF-binding and aFGF-nonbinding 35S-HSPG were individually pooled and further purified by Sepharose CL-4B column chromatography. 35S-HSPG which bind aFGF, designated HSPGP, were 100-fold superior to heparin in augmenting the mitogenic efficacy of aFGF in sparse proliferating cultures. In contrast, however, 35S-HSPG, which did not bind aFGF, designated HSPG1, inhibited aFGF-stimulated proliferation in both sparse and subconfluent endothelial cell cultures. The majority of the biological activity of both aFGF-potentiating HSPGP and aFGF-inhibitory HSPG1 was contained in the glycosaminoglycan chains released by alkaline borohydride treatment of intact HSPGP or HSPG1, respectively. 3H-Core protein derived from HSPGP or HSPG1 contained only minor biological activity. The ability of heparitinase or heparinase (Flavobacterium heparinum) to abolish biological activity differed, depending upon the HSPG tested, also suggested that these are two distinct HSPGs.

Cell biology of arterial proteoglycans

Although proteoglycans constitute a minor component of vascular tissue, these molecules have been shown to influence a number of arterial properties such as viscoelasticity, permeability, lipid metabolism, hemostasis, and thrombosis. A hallmark of early and late atherosclerosis is the accumulation of proteoglycans in the intimal lesions. Yet, it is not clear why this accumulation occurs. This article reviews the classes of proteoglycans synthesized by the two major cell types of the arterial wall--the endothelial and smooth muscle cell. Detailed consideration is then given to the modulation of proteoglycan metabolism and the role that proteoglycans play in a number of cellular events such as adhesion, migration, and proliferation--important processes in both the development and the pathogenesis of blood vessels. Last, the involvement of proteoglycans in two critical vascular wall processes--hemostasis and lipid metabolism--is reviewed, because these events pertain to atherogenesis. This review emphasizes the importance of proteoglycans in regulating several key events in normal and pathophysiological processes in the vascular tissue.

Comparative assessment of cell/substratum static adhesion using an in vitro organ culture method and computerized analysis system

The trypsin sensitivity of chick embryo cellular layers cultivated by an in vitro organ culture method toward different biomaterials has been analysed. Monolayer cells grown on to tested samples were enzymatically dissociated in 5 min - 1 h. Cumulative cell numbers, expressed as the percentage of the totally detached cell number, were plotted versus time, thus permitting the calculation of the function. The mathematical treatment by a computerized system of this function represents the trypsin sensitivity. This value modulated by the migration cell number is the static adhesion modulated index (SAMI). The trypsin sensitivity expressed according to this index allowed the establishment of an abacus wherein several zones, A, B, C and D, define cell adhesion behaviour on different biomaterials. Scanning electron microscopy analysis performed on dissociation steps showed the selective activity of trypsin on cells toward different substrata, revealing the role of an extracellular matrix and cytoskeleton in the adhesion behaviour.