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Physical determinants of fibrinolysis in single fibrin fibers.

Bucay I, O'Brien ET, Wulfe SD, Superfine R, Wolberg AS, Falvo MR, Hudson NE - PLoS ONE (2015)

Bottom Line: We found that during lysis 64 ± 6% of fibers were transected at one point, but 29 ± 3% of fibers increase in length rather than dissolving or being transected.Because lysis rates were greatly reduced in elongated fibers, we hypothesize that plasmin activity depends on fiber strain.These results highlight how subtle differences in the diameter and prestrain of fibers could lead to dramatically different lytic susceptibilities.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina, United States of America.

ABSTRACT
Fibrin fibers form the structural backbone of blood clots; fibrinolysis is the process in which plasmin digests fibrin fibers, effectively regulating the size and duration of a clot. To understand blood clot dissolution, the influence of clot structure and fiber properties must be separated from the effects of enzyme kinetics and perfusion rates into clots. Using an inverted optical microscope and fluorescently-labeled fibers suspended between micropatterned ridges, we have directly measured the lysis of individual fibrin fibers. We found that during lysis 64 ± 6% of fibers were transected at one point, but 29 ± 3% of fibers increase in length rather than dissolving or being transected. Thrombin and plasmin dose-response experiments showed that the elongation behavior was independent of plasmin concentration, but was instead dependent on the concentration of thrombin used during fiber polymerization, which correlated inversely with fiber diameter. Thinner fibers were more likely to lyse, while fibers greater than 200 ± 30 nm in diameter were more likely to elongate. Because lysis rates were greatly reduced in elongated fibers, we hypothesize that plasmin activity depends on fiber strain. Using polymer physics- and continuum mechanics-based mathematical models, we show that fibers polymerize in a strained state and that thicker fibers lose their prestrain more rapidly than thinner fibers during lysis, which may explain why thick fibers elongate and thin fibers lyse. These results highlight how subtle differences in the diameter and prestrain of fibers could lead to dramatically different lytic susceptibilities.

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Diameter Dependence of Fibrinolysis.A Over two hundred single fibers were imaged on the SEM. Fiber diameters were measured at the thinnest point. Data were collected from fibers polymerized at three distinct thrombin concentrations: 0.11 U/mL (84 samples), 1.1 U/mL (64 samples), and 11 U/mL (73 samples), (p < 0.02 for all cases). B Percentage of fibers that lysed or elongated during the first thirty minutes of exposure to 3.3 U/mL of plasmin. Fibrin fibers polymerized by higher concentrations of thrombin lysed more frequently than those polymerized by lower thrombin concentrations. C–E The data in the histograms were segregated according to the percentage of fibers that lysed or elongated. The percentage of fibers with thicknesses below the d0 diameters (indicated by a white dotted line) parallels the percentage of fibers that lysed in the corresponding bar graphs. The threshold diameter (d0) was 200 nm ± 30 nm.
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pone.0116350.g004: Diameter Dependence of Fibrinolysis.A Over two hundred single fibers were imaged on the SEM. Fiber diameters were measured at the thinnest point. Data were collected from fibers polymerized at three distinct thrombin concentrations: 0.11 U/mL (84 samples), 1.1 U/mL (64 samples), and 11 U/mL (73 samples), (p < 0.02 for all cases). B Percentage of fibers that lysed or elongated during the first thirty minutes of exposure to 3.3 U/mL of plasmin. Fibrin fibers polymerized by higher concentrations of thrombin lysed more frequently than those polymerized by lower thrombin concentrations. C–E The data in the histograms were segregated according to the percentage of fibers that lysed or elongated. The percentage of fibers with thicknesses below the d0 diameters (indicated by a white dotted line) parallels the percentage of fibers that lysed in the corresponding bar graphs. The threshold diameter (d0) was 200 nm ± 30 nm.

Mentions: Previous work has indicated that fibrin diameter is inversely proportional to thrombin concentration [1,17,23,28–30]. To confirm these findings, fibrin samples polymerized by three different thrombin concentrations (0.11, 1.1, and 11 U/mL) were imaged using scanning electron microscopy (SEM); the average fiber diameter for each concentration is displayed in Fig. 4A. Consistent with the earlier reports, our data indicate that fiber diameter decreases with increasing thrombin concentration [29].


Physical determinants of fibrinolysis in single fibrin fibers.

Bucay I, O'Brien ET, Wulfe SD, Superfine R, Wolberg AS, Falvo MR, Hudson NE - PLoS ONE (2015)

Diameter Dependence of Fibrinolysis.A Over two hundred single fibers were imaged on the SEM. Fiber diameters were measured at the thinnest point. Data were collected from fibers polymerized at three distinct thrombin concentrations: 0.11 U/mL (84 samples), 1.1 U/mL (64 samples), and 11 U/mL (73 samples), (p < 0.02 for all cases). B Percentage of fibers that lysed or elongated during the first thirty minutes of exposure to 3.3 U/mL of plasmin. Fibrin fibers polymerized by higher concentrations of thrombin lysed more frequently than those polymerized by lower thrombin concentrations. C–E The data in the histograms were segregated according to the percentage of fibers that lysed or elongated. The percentage of fibers with thicknesses below the d0 diameters (indicated by a white dotted line) parallels the percentage of fibers that lysed in the corresponding bar graphs. The threshold diameter (d0) was 200 nm ± 30 nm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4340865&req=5

pone.0116350.g004: Diameter Dependence of Fibrinolysis.A Over two hundred single fibers were imaged on the SEM. Fiber diameters were measured at the thinnest point. Data were collected from fibers polymerized at three distinct thrombin concentrations: 0.11 U/mL (84 samples), 1.1 U/mL (64 samples), and 11 U/mL (73 samples), (p < 0.02 for all cases). B Percentage of fibers that lysed or elongated during the first thirty minutes of exposure to 3.3 U/mL of plasmin. Fibrin fibers polymerized by higher concentrations of thrombin lysed more frequently than those polymerized by lower thrombin concentrations. C–E The data in the histograms were segregated according to the percentage of fibers that lysed or elongated. The percentage of fibers with thicknesses below the d0 diameters (indicated by a white dotted line) parallels the percentage of fibers that lysed in the corresponding bar graphs. The threshold diameter (d0) was 200 nm ± 30 nm.
Mentions: Previous work has indicated that fibrin diameter is inversely proportional to thrombin concentration [1,17,23,28–30]. To confirm these findings, fibrin samples polymerized by three different thrombin concentrations (0.11, 1.1, and 11 U/mL) were imaged using scanning electron microscopy (SEM); the average fiber diameter for each concentration is displayed in Fig. 4A. Consistent with the earlier reports, our data indicate that fiber diameter decreases with increasing thrombin concentration [29].

Bottom Line: We found that during lysis 64 ± 6% of fibers were transected at one point, but 29 ± 3% of fibers increase in length rather than dissolving or being transected.Because lysis rates were greatly reduced in elongated fibers, we hypothesize that plasmin activity depends on fiber strain.These results highlight how subtle differences in the diameter and prestrain of fibers could lead to dramatically different lytic susceptibilities.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina, United States of America.

ABSTRACT
Fibrin fibers form the structural backbone of blood clots; fibrinolysis is the process in which plasmin digests fibrin fibers, effectively regulating the size and duration of a clot. To understand blood clot dissolution, the influence of clot structure and fiber properties must be separated from the effects of enzyme kinetics and perfusion rates into clots. Using an inverted optical microscope and fluorescently-labeled fibers suspended between micropatterned ridges, we have directly measured the lysis of individual fibrin fibers. We found that during lysis 64 ± 6% of fibers were transected at one point, but 29 ± 3% of fibers increase in length rather than dissolving or being transected. Thrombin and plasmin dose-response experiments showed that the elongation behavior was independent of plasmin concentration, but was instead dependent on the concentration of thrombin used during fiber polymerization, which correlated inversely with fiber diameter. Thinner fibers were more likely to lyse, while fibers greater than 200 ± 30 nm in diameter were more likely to elongate. Because lysis rates were greatly reduced in elongated fibers, we hypothesize that plasmin activity depends on fiber strain. Using polymer physics- and continuum mechanics-based mathematical models, we show that fibers polymerize in a strained state and that thicker fibers lose their prestrain more rapidly than thinner fibers during lysis, which may explain why thick fibers elongate and thin fibers lyse. These results highlight how subtle differences in the diameter and prestrain of fibers could lead to dramatically different lytic susceptibilities.

Show MeSH
Related in: MedlinePlus