Incorporation Of Fibrin Research Articles

A modular approach to 3D-printed bilayer composite scaffolds for osteochondral tissue engineering

Prolonged osteochondral tissue engineering damage can result in osteoarthritis and decreased quality of life. Multiphasic scaffolds, where different layers model different microenvironments, are a promising treatment approach, yet stable joining between layers during fabrication remains challenging. To overcome this problem, in this study, a bilayer scaffold for osteochondral tissue regeneration was fabricated using 3D printing technology which containing a layer of PCL/hydroxyapatite (HA) nanoparticles and another layer of PCL/gelatin with various concentrations of fibrin (10, 20 and 30 wt.%). These printed scaffolds were evaluated with SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared Spectroscopy) and mechanical properties. The results showed that the porous scaffolds fabricated with pore size of 210–255 µm. Following, the ductility increased with the further addition of fibrin in bilayer composites which showed these composites scaffolds are suitable for the cartilage part of osteochondral. Also, the contact angle results demonstrated the incorporation of fibrin in bilayer scaffolds based on PCL matrix, can lead to a decrease in contact angle and result in the improvement of hydrophilicity that confirmed by increasing the degradation rate of scaffolds containing further fibrin percentage. The bioactivity study of bilayer scaffolds indicated that both fibrin and hydroxyapatite can significantly improve the cell attachment on fabricated scaffolds. The MTT assay, DAPI and Alizarin red tests of bilayer composite scaffolds showed that samples containing 30% fibrin have the more biocompatibility than that of samples with 10 and 20% fibrin which indicated the potential of this bilayer scaffold for osteochondral tissue regeneration.Graphical

Characterization and biological evaluation of new PLGA/fibrin/lignin biocomposite electrospun scaffolds

In this study, we produced electrospun scaffolds from 10% pure PLGA solution, and 10% polyblend solutions of PLGA/Fibrin, PLGA/Lignin, and PLGA/Fibrin/Lignin with proportions of 9:1, 8:2, 7:3, 7:2:1, 6:2:2, and 5:2:3 and characterized them physiochemically and biologically. FTIR and EDX results verified the chemical composition of the fibers. All scaffolds exhibited homogenous nanostructures with fiber diameters ranging from 0.1 to 2.5 μm and the highest average fiber diameter belonged to PLGA/Lignin fibers. Increasing the lignin proportion led to a decrease in fibers diameter and a change in color to brown. Fibrin improved the hydrophobicity of the scaffolds, and the incorporation of fibrin, lignin, or fibrin/lignin improved the absorption capacity of the scaffolds (up to 91.7%). From day 45 onwards, fibrin-containing scaffolds started to degrade much faster. By day 90, PLGA/20%Fibrin/30%Lignin showed the highest degradation ratio of 82%, while PLGA/10%Lignin showed the lowest at 51.4%. All scaffolds exhibited high porosity percentage (over 78%), with porosity enhanced by increasing fibrin and decreasing lignin. The pure PLGA scaffold and PLGA/10%Lignin showed the highest stiffness and tensile strength, respectively. The addition of natural components gradually decreased the scaffolds’ tensile strength and fracture strain. MTT results showed higher absorbance reading at 490 nm for PLGA, PLGA/10%Fibrin, and all three PLGA/Lignin scaffolds from day 3 to day 7. On day 7, PLGA/10%Fibrin exhibited the highest cell viability, followed by PLGA/10%Lignin and PLGA/20%Fibrin/10%Lignin. SEM micrographs revealed the presence of h-ADSCs with spindle-like morphologies, attached and proliferated well on all scaffolds. PLGA/10%Fibrin, PLGA/10%Lignin, and PLGA/20%Fibrin/10%Lignin were selected as the preferred options from each set of scaffolds. Among them, PLGA/20%Fibrin/10%Lignin exhibited superior physical features and actively enhanced the biological responses of the cells due to its physio-mechanical signals and the advanced features of lignin, making it suitable for tissue engineering, wound dressing, drug delivery, and other biomedical applications.

Porcine Resorbable Collagen Matrix Shows Good Incorporation of Liquid Platelet-Rich Fibrin In Vitro.

Purpose: To evaluate the incorporation of liquid platelet-rich fibrin in different collagen matrices in vitro. Materials and Methods: Collagen matrices with liquid platelet-rich fibrin were used and divided into the following test groups (n = 5): Mucoderm (MD), Mucograft (MG), and Fibro-Gide (FG). After incubating the collagen matrices in liquid platelet-rich fibrin, histologicl and fluid absorption capacity analysis were performed. Intergroup comparisons of cell count, blood plasma penetration area, and fluid absorption capacity were performed using one-way ANOVA and Tukey tests. Intragroup comparisons of fluid absorption capacity were made using the independent t test with a 5% significance level. Results: Descriptive qualitative analysis showed total incorporation of liquid platelet-rich fibrin in the FG group, while the MG and MD groups showed only partial and shallow incorporation, respectively. There was a statistically significant difference among the three groups regarding inflammatory cell infiltration (P = .000), with the FG group presenting the highest number of cells in the matrices (577.15 ± 54.88). The FG group showed an area of total blood plasma penetration into the matrix, followed by the MG group with partial penetration, and the MD group with minor penetration area (P = .000). Considering the fluid absorption capacity analysis, only groups FG and MG were statistically different when comparing the liquid platelet-rich fibrin absorption coefficient (P = .017), with higher absorption in group FG (14.30 ± 3.35). Conclusions: The FG collagen matrix showed a good capacity for liquid platelet-rich fibrin incorporation in vitro.

Incorporation of Fibrin, Platelets, and Red Blood Cells into a Coronary Thrombus in Time and Space.

We describe the internal structure, spatial organization and dynamic formation of coronary artery thrombi from ST-segment elevation myocardial infarction patients. Scanning electron microscopy (SEM) revealed significant differences among four groups of patients (<2 hours; 2-6 hours; 6-12 hours, and >12 hours) related to the time of ischemia. Coronary artery thrombi from patients presenting less than 2 hours after the infarction were almost entirely composed of platelets, with small amounts of fibrin and red blood cells. In contrast, thrombi from late presenters (>12 hours) consisted of mainly platelets at the distal end, where clotting was initiated, with almost no platelets at the proximal end, while the red blood cell content went from low at the initiating end to more than 90% at the proximal end. Furthermore, fibrin was present mainly on the outside of the thrombi and older thrombi contained thicker fibers. The red blood cells in late thrombi were compressed to a close-packed, tessellated array of polyhedral structures, called polyhedrocytes. Moreover, there was redistribution from the originally homogeneous composition to fibrin and platelets to the outside, with polyhedrocytes on the interior. The presence of polyhedrocytes and the redistribution of components are signs of in vivo clot contraction (or retraction). These results suggest why later thrombi are resistant to fibrinolytic agents and other treatment modalities, since the close-packed polyhedrocytes form a nearly impermeable seal. Furthermore, it is of particular clinical significance that these findings suggest specific disparate therapies that will be most effective at different stages of thrombus development.

The effect of fibrin on rheological behavior, gelling properties and microstructure of myofibrillar proteins

The aim of this study was to evaluate water-holding capacity, texture, rheological properties, interactions and microstructure of myofibrillar proteins (MP) gel with the addition of fibrin during the heat-induced process. Compared with the control, whiteness, water-holding capacity and hardness of MP gel with the addition of 2% fibrin increased by 9.70%, 79.36%, 323.07%, respectively. Storage modulus and loss modulus values in 2% fibrin addition group were higher than those of the control. The conformation of random coil gradually transformed to β-sheet and β-turn with the increase of fibrin content; nonspecific association and hydrophobic interactions increased from 14.27 g L−1 and 9.00 g L−1 in the control to 28.96 g L−1 and 12.90 g L−1 in the addition of 2% fibrin, respectively, indicating that these interactions played a key role in the improvement of gelling and rheological properties of MP. Scanning electron microscopy revealed that the incorporation of fibrin facilitated the formation of composited gel with a more ordered and homogeneous gel network structure. These results indicated that fibrin enhanced the functionality of MP, which could be beneficial to the development of gel-type meat products.

Development of fibrous PLGA/fibrin scaffolds as a potential skin substitute

The aim of this study has been to fabricate a hybrid electrospun nanofibrous scaffold composed of poly(lactic-co-glycolic) acid (PLGA)/fibrin polymers to be used as a skin substitute and analyze its physical and biological properties. Fibrin was obtained from rat blood plasma, characterized and solubilized in formic acid. The final electrospinning solution concentration was 40% PLGA (w/v) and 1% fibrin (w/v). To improve spinnability, 3% PEG (w/v) was added. The scaffolds were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Water contact angle, maximum elongation, thermal stability, degree of swelling, blood compatibility, cytotoxicity and cell viability were analyzed. The characterization by SEM showed randomly oriented nanofibers with a mean diameter of 639.8 ± 241.8 nm for the PLGA/fibrin and 1051.0 ± 290.2 nm for the PLGA. FTIR spectra confirmed the presence of fibrin in the mats. Fibrin incorporation reduced the water contact angle from 118.9 ± 2.9 to 111.1 ± 2.8. The fibrin increased tensile strength and decreased elongation at break. The scaffolds demonstrated blood compatibility and fibrin incorporation improved cell adhesion and viability when direct and indirect MTT analyses were carried out. Thus, it can be concluded that the PLGA/fibrin mat is a promising material for use as a skin substitute.

Comparison of Biocompatibility and Biodegradability of Poly(Lactic-Co-Glycolic Acid) (Plga) Combined with Autologous Fibrin Versus Plga for Intra-Articular Screw Fixation; An Invivo Study with New Zealand White Rabbits- The Microradiograph Outcome

Introduction: The great potential of biodegradable polymers in orthopaedic surgery is gradually being recognized. PLGA is one of the common polymers used. However, long term outcomes, with regards to PLGA, are still not well documented. Hence, we attempted to study the outcome of PLGA and also its combination with fibrin. Materials and method: Objectives : 1) To compare biocompatibility and biodegradability of polymer (PLGA + fibrin) with PLGA for intra-articular screw fixation 2) to study the imaging microradiograph) features. We used fabricated PLGA scaffolds in combination with autologous fibrin for an in-vivo prospective research. Total of nine New Zealand White Rabbits (NZWR) were operated and the scaffolds were placed at both medial and lateral femoral condyles of the right knee and those with fibrin at the left knee. Post implantation, evaluation was done at 6,12 and 24 weeks (three NZWR in each group). For microradiological assessment, micro CT (Skyscan 1176) was used. Results: The combination of PLGA and fibrin has better biocompatibility, showed faster biodegradation and more quantitative integration of osseous tissues. Conclusion: Biodegradable polymer PLGA with incorporation of fibrin resulted in superior outcome compared to usage of other current biodegradable polymers.

Incorporation of fibrin into a collagen–glycosaminoglycan matrix results in a scaffold with improved mechanical properties and enhanced capacity to resist cell-mediated contraction

Fibrin has many uses as a tissue engineering scaffold, however many in vivo studies have shown a reduction in function resulting from the susceptibility of fibrin to cell-mediated contraction. The overall aim of the present study was to develop and characterise a reinforced natural scaffold using fibrin, collagen and glycosaminoglycan (FCG), and to examine the cell-mediated contraction of this scaffold in comparison to fibrin gels. Through the use of an injection loading technique, a homogenous FCG scaffold was developed. Mechanical testing showed a sixfold increase in compressive modulus and a thirtyfold increase in tensile modulus of fibrin when reinforced with a collagen–glycosaminoglycan backbone structure. Human vascular smooth muscle cells (vSMCs) were successfully incorporated into the FCG scaffold and demonstrated excellent viability over 7days, while proliferation of these cells also increased significantly. VSMCs were seeded into both FCG and fibrin-only gels at the same seeding density for 7days and while FCG scaffolds did not demonstrate a reduction in size, fibrin-only gels contracted to 10% of their original diameter. The FCG scaffold, which is composed of natural biomaterials, shows potential for use in applications where dimensional stability is crucial to the functionality of the tissue. Statement of SignificanceFibrin is a versatile scaffold for tissue engineering applications, but its weak mechanical properties leave it susceptible to cell-mediated contraction, meaning the dimensions of the fibrin construct will change over time. We have reinforced fibrin with a collagen glycosaminoglycan matrix and characterised the mechanical properties and bioactivity of the reinforced fibrin (FCG). This is the first scaffold manufactured from all naturally derived materials that resists cell-mediated contraction. In fact, over 7days, the FCG scaffold fully resisted cell-mediated contraction of vascular smooth muscle cells. This FCG scaffold has many potential applications where natural scaffold materials can encourage regeneration.

Cross-modulatory effects of clopidogrel and heparin on platelet and fibrin incorporation in thrombosis

Pharmacologic inhibition of platelet activation and aggregation is a mainstay for reducing the incidence of arterial thrombosis, whereas anticoagulation is the primary approach for preventing the development of venous thrombosis. The effect of standard pharmacologic agents on their reciprocal vessel - anticoagulants on arterial thrombosis and platelet inhibitor on venous thrombosis - is relatively understudied. This study was designed to evaluate murine large-vessel arterial or venous thrombosis under conditions of either fibrin or platelet inhibition. In this study, heparin and clopidogrel were used as standard anticoagulant and platelet inhibitor, respectively, evaluating both large artery and vein thrombosis in mice, using in-vivo fluorescence imaging to simultaneously measure fibrin and platelet levels at the thrombus induction site. Heparin reduced both fibrin and platelet development in both arteries and veins, with stronger influences on fibrin accrual. Clopidogrel had a stronger effect in arteries, reducing both platelet and fibrin accumulation. Clopidogrel also reduced platelet accumulation with venous thrombosis, but the reductions in fibrin formation did not reach statistical significance. These findings illustrate the interactive role of platelet activity and coagulation in the development of large-vessel thrombosis, with inhibition of one thrombotic component showing profound effects on the other component in both arterial and venous thrombosis.

The role of platelets in the initial stages of atherosclerosis.

The role of platelets in the initial stages of atherosclerosis.

Evidence that catalytically-inactivated thrombin forms non-covalently linked dimers that bridge between fibrin/fibrinogen fibers and enhance fibrin polymerization

Phe-pro-arg-chloromethyl ketone-inhibited α-thrombin [FPRα-thr] retains its fibrinogen recognition site (exosite 1), augments fibrin/fibrinogen [fibrin(ogen)] polymerization, and increases the incorporation of fibrin into clots. There are two ‘low-affinity’ thrombin-binding sites in each central E domain of fibrin, plus a non-substrate ‘high affinity’ γ′ chain thrombin-binding site on heterodimeric ‘fibrin(ogen) 2’ molecules (γ A,γ′). ‘Fibrin(ogen) 1’ (γ A, γ A) containing only low-affinity thrombin-binding sites, showed concentration-dependent FPRα-thr enhancement of polymerization, thus indicating that low-affinity sites are sufficient for enhancing polymerization. FPRγ-thr, whose exosite 1 is non-functional, did not enhance polymerization of either fibrin(ogen)s 1 or 2 and DNA aptamer HD-1, which binds specifically to exosite 1, blocked FPRα-thr enhanced polymerization of both types of fibrin(ogen) (1>2). These results showed that exosite 1 is the critical element in thrombin that mediates enhanced fibrin polymerization. Des Bβ1-42 fibrin(ogen) 1, containing defective ‘low-affinity’ binding sites, was subdued in its FPRα-thr-mediated reactivity, whereas des Bβ1-42 fibrin(ogen) 2 (γ A,γ′) was more reactive. Thus, the γ′ chain thrombin-binding site contributes to enhanced FPRα-thr mediated polymerization and acts through a site on thrombin that is different from exosite 1, possibly exosite 2. Overall, the results suggest that during fibrin clot formation, catalytically-inactivated FPRα-thr molecules form non-covalently linked thrombin dimers, which serve to enhance fibrin polymerization by bridging between fibrin(ogen) molecules, mainly through their low affinity sites.

Antithrombotic effects of thrombin-induced activation of endogenous protein C in primates.

The effects on thrombosis and hemostasis of thrombin-induced activation of endogenous protein C (PC) were evaluated in baboons. Thrombosis was induced by placing into arteriovenous shunts a segment of Dacron vascular graft, which generated arterial platelet-rich thrombus, followed by an expansion region of low-shear blood flow, which in turn accumulated fibrin-rich venous-type thrombus. Thrombosis was quantified by 111In-platelet imaging and 125I-fibrinogen accumulation. Intravenous infusion of alpha-thrombin, 1-2 U/kg-min for 1 h, increased baseline activated PC levels (approximately 5 ng/ml) to 250-500 ng/ml (P < 0.01). The lower thrombin dose, which did not deplete circulating platelets, fibrinogen, or PC, reduced arterial graft platelet deposition by 48% (P < 0.05), and platelet and fibrin incorporation into venous-type thrombus by > 85% (P < 0.01). Thrombin infusion prolonged the activated partial thromboplastin clotting time, elevated fibrinopeptide A (FPA), thrombin-antithrombin III complex (T:AT III), and fibrin D-dimer plasma levels (P < 0.01), but did not affect bleeding times. Thrombin's antithrombotic effects were blocked by infusing a monoclonal antibody (HPC-4) which prevented PC activation in vivo, caused shunt occlusion, increased the consumption of platelets and fibrinogen, elevated plasma FPA and T:AT III levels, and reduced factor VIII (but not factor V) procoagulant activity (P < 0.05). We conclude that activated PC is a physiologic inhibitor of thrombosis, and that activation of endogenous PC may represent a novel and effective antithrombotic strategy.

Quantification of fibrin deposition in flowing blood with peroxidase-labeled fibrinogen. High shear rates induce decreased fibrin deposition and appearance of fibrin monomers.

To study fibrin incorporation into thrombi at different wall shear rates, a new method to study fibrin deposition on extracellular matrixes underlying stimulated endothelial cells under flow conditions was developed. For this method, we used fibrinogen labeled with peroxidase (Fg-PO). Fg-PO was fully exchangeable for Fg in the clotting assays tested, and PO activity was bound to fibrin-specific fragments. Fg-PO containing fibrin could be stained for microscopic studies with 3,3'-diaminobenzidine and could be quantified by oxidation of phenylenediamine. The absorbance values at 492 nm were converted to fibrin quantities via a standard curve. To study fibrin deposition, Fg-PO was added in trace amounts to whole blood anticoagulated with low-molecular-weight heparin, and perfusion studies were performed over endothelial cell matrixes containing tissue factor. In parallel perfusion studies, 125I-labeled Fg was added in trace amounts to whole blood instead of Fg-PO. Both quantitative methods demonstrated decreased fibrin deposition after perfusions at 1,300 sec-1 compared with fibrin deposition after perfusions at 300 sec-1, while fibrinopeptide A generation was independent of the wall shear rate. The decrease in fibrin deposition at 1,300 sec-1 was accompanied by the appearance of fibrin monomers in the perfusate. This suggested that the decrease in fibrin incorporation at 1,300 sec-1 was due to the impaired polymerization of fibrin monomers. This impairment was probably due to a decrease in local fibrin monomer concentration as a result of the increased removal of monomers from the surface at 1,300 sec-1.

Ancrod enhances the thrombolytic effect of streptokinase and urokinase.

Since thrombi continue to incorporate fibrin during lysis we tested the effect of pretreatment with ancrod, a defibrinating agent from Malaysian pit viper venom, on thrombolysis with urokinase and streptokinase. Thrombi were induced by copper-coils in the carotid arteries of the dogs, weighed after 1 hour and inserted into the femoral arteries of the same animals. They were then exposed for 15 min to iv boluses of streptokinase 10,000 U/kg, urokinase 10,000 U/kg and urokinase 25,000 U/kg with or without pretreatment with ancrod. Ancrod depleted fibrinogen within 5 min and enhanced the lytic effect of streptokinase from 25 +/- 8% to 59 +/- 13% (p less than .05), urokinase 10,000 U/kg from 16 +/- 11% to 66 +/- 18% (p less than .01) and urokinase 25,000 U/kg from 27 +/- 17% to 85 +/- 8% (p less than .001) of the initial thrombus weight. Ancrod itself did not activate plasminogen to plasmin. We conclude that ancrod enhances thrombolysis probably by depleting fibrinogen and preventing new fibrin incorporation into the thrombus during lysis.

Effects of thrombospondin on fibrin polymerization and structure.

Thrombospondin (TSP) is a trace protein in plasma but is released in high concentrations from alpha-granules of activated platelets during hemostasis. It binds to the platelet membrane and becomes incorporated into fibrin clots. A variety of approaches were taken to learn the effects of TSP on fibrin polymerization and structure. 125I-TSP and 125I-fibrinogen were used to study the effect of TSP concentration on the extent of TSP and fibrin incorporation. Turbidity at 600 nm was used to monitor the time course of polymerization. Wavelength dependence of the turbidity was used to calculate the mass to length ratio, fiber diameter, and fiber density of fibrin formed in the presence and absence of TSP. Morphologies of control and TSP-containing clots were examined by electron microscopy following critical point drying. The initial TSP concentration influenced the amount of TSP incorporated but did not alter the extent of fibrin polymerization. TSP, in a concentration-dependent manner, reduced the lag time to turbidity rise and caused formation of more numerous but thinner fibers. Except for their diameter, these fibers were identical to fibers of control fibrin in terms of density and morphology. It is proposed that TSP interacts with fibrin intermediates to accelerate fiber growth, perhaps by serving as a trifunctional branching unit during network formation. The properties of fibrin around aggregating platelets, therefore, may be influenced considerably by secreted TSP.

Histophysical and histochemical investigations on muscle arterioles in hypertensive arteriolosclerosis; an interference microscopical, polarization optical and histophotometrical study

In 50 formol fixed biopsies from the m. quadriceps femoris normal and hypertensive arteriolosclerotic arterioles were characterized by quantitative histophysical and histochemical methods. The interference microscopical measurements showed a real increase of dry mass concentration in the pathologically changed vessels. Additional histophotometrical results are interpreted as an increase of proteins with higher isoelectric point (globulins, actomyosin). An augmentation of actomyosin is compatible with the medial hyperplasia demonstrated histologically. Likewise a positive correlation was found between the fibrin incorporation proved histochemically and the quantitatively evaluated protein reaction with Fast green; Glycosaminglycans do not carry weight quantitatively. The polarization optical measurements yielded an alteration of the submicroscopical structure in arteriolosclerosis. It consists in a diminution of the submicroscopical volum of gaps and in a diminished orientated dye binding of Congo red. Thereby the pathogenesis of hypertensive arteriolosclerosis of skeleton muscle is above all characterized by an increase of heterogeneous proteins (blood plasma proteins, actomyosin) in the arteriolar wall, leading to a diminution of the submicroscopical volume of gaps and to an elevation of the dry mass concentration.

Effect of selective depletion of fibrinogen on the evolution of cholesterol-induced atherosclerosis in rabbits

Atherosclerosis was produced by induced alimentary hyperlipaemia in four groups of rabbits. Animals of groups II and III received cholesterol feeds daily for 2 months while in groups IV and V this was followed by another 3 months of intermittent feeding. Group I comprised normal control rabbits. Selective fibrinogen depletion was produced in groups III and V with Arvin so as to maintain the plasma fibrinogen around 100 mg/dl over the last 2 months of cholesterol feeding. Serum lipids, blood coagulation and euglobulin clot lysis as well as the post mortem histopathology of aorta, heart, kidneys, liver and lungs did not reveal any significant differences between corresponding groups of hyperlipaemic animals treated with (groups III and V) or without (groups 11 and IV) Arvin. It appears that fibrinogen or fibrin incorporation does not play a significant role in the pathogenesis of atherosclerotic lesions induced in rabbits by cholesterol feeding.

The ethanol gelation test and thrombosis.

Intravascular fibrin formation takes place during thrombus formation or by activation of coagulation in circulating blood. Incorporation of fibrin in thrombi may be detected by usine 125I-labelled fibrinogen. Soluble fibrin may be present during thrombophilic states or during thromboembolic complications and diseminated intravascular coagulation (DIC) and may be detected and quantitated by various techniques such as N-terminal amino acid analysi, chromatographic procedures and so-called paracoagulation test, using ethanol or protamine sulfate. Finally, transformation of fibrinogen to fibrin may be indirectly assayed by quantitation of fibrinopeptide A released, by immunological technique. For routine purposes and especially in emergency situation, rapid and simple tests are required. In these circumstances, only the paracoagulation tests are at hand. Below, the present situation with regard to the ethanol gelation test (EGT) is outlined.

Myocardial Infarction and Thromboembolism

Coronary occlusion is generally the result of two distinct but often coincident processes: One, atherosclerosis, progresses slowly to produce narrowing; the other, thrombosis, often apparently sudden, completes the obstruction of the lumen. While atherosclerosis-thrombosis is the usual sequence in the pathogenesis of coronary occlusion, occasionally atheroma alone is the cause and, exceptionally, thrombosis complicates relatively minor intimal disease. This description of two separate factors producing coronary obstruction does not exclude the probability that certain phases of blood coagulation, ie, deposition of fibrin, platelets, or both, may contribute to the development of atherosclerosis, a thesis originally proposed by Rokitansky1and revived and documented by Duguid and others2-4who have found histologic evidence of incorporation of fibrin into atheromatous lesions. The part played by increased thrombogenic activity in the blood of patients with ischemic heart disease is disputed. While some authors5-7have reported increased coagulability based upon one or

The incorporation of fibrin in the aortic intima.

The incorporation of fibrin in the aortic intima.