The collagenous components of the subendothelium. Correlation of structure and function.

Endothelial cells provide a continuous nonthrombogenic lining for the vascular tree. Once the endothelium is denuded platelet adhesion and aggregation occur. One postulated mechanism for the nonthrombogenic properties of the endothelial surface is PGI2 production by endothelial cells, which strongly inhibits platelet aggregation. We propose here that the collagen type(s) associated with the endothelial cell surface may also play an important role in these phenomenon. We found that endothelial cells in culture produce types IV and AB2 collagen (both do not aggregate platelets in vitro) and that type AB2 collagen is uniformly distributed on the endothelial cell surface. We have shown this by immunofluorescence microscopy, immunoelectron microscopy, biosynthetic incorporation, and specific immunoprecipitation techniques. Platelets will not aggregate on monolayers of endothelium while they will aggregate on monolayers of other cells cultured from the vascular wall which produce collagen types that aggregate platelets in vitro. Thus, a specific cell surface-associated collagen (type AB2) may be an important determinant in the ability of the endothelial cell to present a nonthrombogenic surface to the blood.

Prenatal diagnosis of classic hemophilia.

Prenatal diagnosis of classic hemophilia (hemophilia A) in mid-trimester was achieved by means of immunoradiometric assays for factor VIII on fetal plasma and amniotic-fluid mixtures obtained by fetoscopy. Samples were analyzed from six male fetuses at risk for severe hemophilia and from nine control fetuses for which fetoscopy was carried out to attempt prenatal diagnosis of other genetic disorders. The factor VIII coagulant-antigen values for the control (non-hemophilic) samples were 17 to 94, and the factor VIII related-antigen concentrations were 50 to 155 U per deciliter. Three of the fetuses at risk for hemophilia had factor VIII values in the control range, and these infants were normal at birth. The other three fetuses had low concentrations of factor VIII coagulant antigen but normal concentrations of factor VIII related antigen. These values and the diagnoses of severe hemophilia were confirmed with blood from the abortuses.

Tissue-factor coagulant activity of cultured human endothelial and smooth muscle cells and fibroblasts.

The tissue-factor (thromboplastic) activity of cultured human endothelial cells and fibroblasts is low at time of transfer into fresh medium but increases 3-10 fold. Endothelial cells reach peak activity (400 U/10(5) cells) 5-8 hr after subculture. Activity in fibroblast cultures peaks (3000-12,000 U/10(5) cells) 7-12 hr after subculture. After attaining maximum activity, endothelial and fibroblast tissue-factor content decreases in a time course similar to other cells studied in this laboratory, approaching basal levels by 24-50 hr after subculture. If medium over fibroblasts is changed every 12 hr, activity can be sustained at the peak level for an additional day but cannot be maintained at a high level indefinitely. The kinetics of expression of smooth muscle cell tissue factor are markedly different from other cell types. There is always a pronounced lag (30 hr or more) before the activity increases, and then, in most cases, there is no subsequent decline in activity even though the cells are not refed or restimulated. The activity of each of these cell types is cryptic but becomes available after freeze-thaw disruption of cells.

Tissue factor in cultured cells: pharmacologic effects.

Tissue factor activity in suspension cultures of WISH amnion cells is modulated by pharmacologic doses of agents which alter membrane structure and function. Lysosomal stabilizing steroids (hydrocortisone, dexamethasone, aldosterone, prednisolone, and estradiol) suppress the change in activity which follows subculture; lytic steroids (testosterone and progesterone) are ineffective. Chloroquine both increases the specific activity and extends the time before return to the basal level. Dimethyl sulfoxide and ouabain suppress the complete expression of activity but do not inhibit the subsequent decay. The effect of cytochalasin B is complex, the drug being either suppressive or slightly stimulatory depending on the time of addition. Cyclic nucleotides (AMP or GMP) or insulin do not regulate the expression of tissue factor in these cells. A dramatic increment and prolongation of activity occurs when colchicine or vinblastine is added to the cell suspension shortly after subculture; there is much less stimulation by griseofulvin. Lumicolchicine has no effect while deuterium oxide is inhibitory. From these experiments, we conclude that increased membrane fluidity or altered secretory processes resulting from microtubule disruption stabilize tissue factor in cultured cells. Since contradictory results were obtained with agents which stabilize lysosomes or inhibit transport, the role of these cellular functions in tissue factor production or decay is unclear.

Tissue factor in cultured cells: metabolic control.

Tissue factor content of WISH amnion cells in spinner culture increases 3- to 10-fold within 12 hours after subculture, then declines to a basal level within 30 to 50 hours. Maximal development of activity requires fresh serum and fresh medium. When added at the time of subculture, actinomycin D and cycloheximide completely inhibit development of coagulant activity; when added several hours after transfer, these inhibitors suppress the development but do not affect the disappearance of activity. Of the oxidative phosphorylation inhibitors tested, dinitrophenol had no effect whereas carbonyl cyanide m-chlorophenylhydrazone inhibited the activity increase but did not alter the decline. The kinetics of development and decay are similar over a pH range of 6.7 to 7.6 and with fetal calf serum concentration between 5 and 30 per cent. At pH 6.7 or in 30 per cent fetal calf serum, cell division did not occur. 3H-leucine and 35SO4= incorporation into the cell surface coat did not change appreciably during the burst of coagulant activity nor did the levels of naphthylamidase or alkaline phosphatase; 3H-thymidine incorporation reached a peak within 2 hours of the tissue factor maximum.

Electron microscopic immunohistochemical identification of endothelial cells in the rabbit.

Antibody to tissue factor apoprotein was adsorbed against gamma-globulin and coupled to horseradish peroxidase; this complex was applied to various rabbit tissues. The distribution of the peroxidase marker then was observed by electron microscopy. We examined fixed or frozen sections, as well as breis of aorta, vena cava, brain, heart, lung, liver, spleen, kidney, bone marrow, mesothelial gut lining, erythrocytes, and platelets. All endothelial cells that had been exposed to the antibody complex were positive and in all cases only the endothelial cells showed localization of the electron-dense reaction product. Tissues that had been incubated with complexes prepared with gamma-globulin from animals not immunized with tissue factor apoprotein showed no staining. Prior treatment of the tissue with uncoupled anti-tissue factor gamma-globulin blocked binding by the coupled antibody. In blood vessel preparations that had been specifically designed to expose the media to the anti-tissue factor complex, medial smooth muscle cells and connective tissue showed no reaction product. Parenchymal cells of the other other organs mentioned likewise were devoid of reaction product. Similarly, the leukocytes and platelets occasionally observed in vessel lumens showed no evidence of binding. Platelets adhering to arterial subendothelial structure after injury also were unreactive. These findings suggest that in normal rabbits anti-tissue factor-horseradish peroxidase complex combines selectively with endothelial cells.

Binding of bovine brain tissue factor to concanavalin A-Sepharose. Partial purification of coagulant, arylamidase, and alkaline phosphatase activities.

Tissue factor coagulant activity is adsorbed onto concanavalin A-Sepharose from sodium deoxycholate extracts of delipidated bovine brain powders. Coagulant activity is eluted with alpha-methyl-D-glucoside in sodium deoxycholate with 2--25-fold purification. This material has the same coagulant specific activity as that previously prepared in this laboratory. Alkaline phosphatase and alanyl-beta-naphthylamidase activities in the detergent extract also bind to concanavalin A-Sepharose and elute under the same conditions with 4- and 7-fold purification. In addition to these biological activities, the eluate was composed of protein (67.7%), neutral and amino sugars and sialic acid (22.3%), phospholipid (4.5%), uronic acid (3.8%) and nucleic acid (1.7%). This preparation is slightly enriched in carbohydrates compared to previous preparations. Concanavalian A-Sepharose therefore appears to be useful material for partial purification of several mammalian plasma membrane components with retention of biological function.

Association of tissue factor activity with the surface of cultured cells.

Tissue factor occurs in a dormant state on the surface of cultured normal human fibroblasts and WISH 1 amnion cells. The activity of undisturbed monolayers or cells lifted with brief trypsin treatment (0.125 per cent trypsin for 1 min) increases up to 60-fold upon prolonged digestion with dilute trypsin (0.0025 per cent trypsin for 30 min); activity appears subsequent to cell detachment. Up to 70 per cent of the total cellular tissue factor becomes active under these conditions and is released from the cells. The ruthenium red staining coat of the cells is lost during detachment, but cell viability (more than 90 per cent exclude trypan blue) and cell morphology do not change during the subsequent development of tissue factor activity. Furthermore, less than 10 percent of four intracellular enzymes and less than 20 per cent of two plasma membrane enzymes are released during this period of time. We therefore conclude that cells in culture do have tissue factor activity, that it exists in a latent form, and that total cell disruption is not necessary for this activity to initiate blood coagulation.

Concanavalin A inhibits tissue factor coagulant activity.

Concanavalin A (con A) is a potent inhibitor of coagulant activity of native tissue factor. Coagulant activity is recovered by addition of alpha-methyl-D-glucoside to inhibited tissue factor. Inclusion of alpha-methyl-D-glucose during incubation of con A with tissue factor preserves coagulant activity. These data suggest that con A interacts reversibly with a carbohydrate residue in such a way as to inhibit coagulant activity of the molecule. Purified tissue factor apoprotein has been recombined with mixed brain phospholipids or purified phospholipids (phosphatidyl ethanolamine or a mixture of phosphatidyl choline with phosphatidyl serine). These preparations were also completely but reversibly inhibited by con A. Thus, purified tissue factor apoprotein appears to donate the affected carbohydrate residue.

Tissue factor activity in lymphocyte cultures from normal individuals and patients with hemophilia A.

The procoagulant material of lymphocytes has been characterized as tissue factor. Lymphocytes stimulated with phytohemagglutinin or the purified protein derivative of the tubercle bacillus developed procoagulant activity with incubation in tissue culture. While this material corrected the prolonged clotting time of factor VIII (AHF) deficient plasma, we have shown, utilizing a sensitive radioimmunoassay, that no AHF antigen was present in the cell cultures. Further, we have demonstrated this material to be tissue factor by coagulation techniques and immunological cross-reactivity. The published data regarding factor VIII synthesis is reviewed in light of these observations and comments are made regarding the role of the lymphocyte procoagulant.

Tissue factor (thromboplastin): localization to plasma membranes by peroxidase-conjugated antibodies.

Peroxidase-conjugated antibodies were used to determine the histologic and cytologic localization of bovine and human tissue factor (thromboplastin). Tissue factor antigen was found in highest concentration in the intima of blood vessels, particularly in the plasma membranes of endothelial cells and in human atheromatous plaques. Tissue factor was also found limited to the plasma membranes of many cell types. The presence of tissue factor in the plasma membranes of endothelial cells and atheromata suggests that it may play a significant role in hemostasis and thrombosis.