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Spiewak R, Gosselin A, Merinov D, Litvinov RI, Weisel JW, Tutwiler V, Purohit PK. Biomechanical origins of inherent tension in fibrin networks. J Mech Behav Biomed Mater 2022; 133:105328. [PMID: 35803206 PMCID: PMC9434494 DOI: 10.1016/j.jmbbm.2022.105328] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 06/02/2022] [Accepted: 06/18/2022] [Indexed: 10/17/2022]
Abstract
Blood clots form at the site of vascular injury to seal the wound and prevent bleeding. Clots are in tension as they perform their biological functions and withstand hydrodynamic forces of blood flow, vessel wall fluctuations, extravascular muscle contraction and other forces. There are several mechanisms that generate tension in a blood clot, of which the most well-known is the contraction/retraction caused by activated platelets. Here we show through experiments and modeling that clot tension is generated by the polymerization of fibrin. Our mathematical model is built on the hypothesis that the shape of fibrin monomers having two-fold symmetry and off-axis binding sites is ultimately the source of inherent tension in individual fibers and the clot. As the diameter of a fiber grows during polymerization the fibrin monomers must suffer axial twisting deformation so that they remain in register to form the half-staggered arrangement characteristic of fibrin protofibrils. This deformation results in a pre-strain that causes fiber and network tension. Our results for the pre-strain in single fibrin fibers is in agreement with experiments that measured it by cutting fibers and measuring their relaxed length. We connect the mechanics of a fiber to that of the network using the 8-chain model of polymer elasticity. By combining this with a continuum model of swellable elastomers we can compute the evolution of tension in a constrained fibrin gel. The temporal evolution and tensile stresses predicted by this model are in qualitative agreement with experimental measurements of the inherent tension of fibrin clots polymerized between two fixed rheometer plates. These experiments also revealed that increasing thrombin concentration leads to increasing internal tension in the fibrin network. Our model may be extended to account for other mechanisms that generate pre-strains in individual fibers and cause tension in three-dimensional proteinaceous polymeric networks.
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Affiliation(s)
- Russell Spiewak
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Andrew Gosselin
- Department of Biomedical Engineering, Rutgers - The State University of New Jersey, 599 Taylor Road, Room 209, Piscataway, NJ 08854, USA
| | - Danil Merinov
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, 1154 BRB II/III, 421 Curie Boulevard, Philadelphia, PA 19104-6058, USA
| | - Rustem I Litvinov
- Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, 1154 BRB II/III, 421 Curie Boulevard, Philadelphia, PA 19104-6058, USA
| | - John W Weisel
- Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, 1154 BRB II/III, 421 Curie Boulevard, Philadelphia, PA 19104-6058, USA.
| | - Valerie Tutwiler
- Department of Biomedical Engineering, Rutgers - The State University of New Jersey, 599 Taylor Road, Room 209, Piscataway, NJ 08854, USA.
| | - Prashant K Purohit
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Jansen KA, Zhmurov A, Vos BE, Portale G, Hermida-Merino D, Litvinov RI, Tutwiler V, Kurniawan NA, Bras W, Weisel JW, Barsegov V, Koenderink GH. Molecular packing structure of fibrin fibers resolved by X-ray scattering and molecular modeling. SOFT MATTER 2020; 16:8272-8283. [PMID: 32935715 DOI: 10.1039/d0sm00916d] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Fibrin is the major extracellular component of blood clots and a proteinaceous hydrogel used as a versatile biomaterial. Fibrin forms branched networks built of laterally associated double-stranded protofibrils. This multiscale hierarchical structure is crucial for the extraordinary mechanical resilience of blood clots, yet the structural basis of clot mechanical properties remains largely unclear due, in part, to the unresolved molecular packing of fibrin fibers. Here the packing structure of fibrin fibers is quantitatively assessed by combining Small Angle X-ray Scattering (SAXS) measurements of fibrin reconstituted under a wide range of conditions with computational molecular modeling of fibrin protofibrils. The number, positions, and intensities of the Bragg peaks observed in the SAXS experiments were reproduced computationally based on the all-atom molecular structure of reconstructed fibrin protofibrils. Specifically, the model correctly predicts the intensities of the reflections of the 22.5 nm axial repeat, corresponding to the half-staggered longitudinal arrangement of fibrin molecules. In addition, the SAXS measurements showed that protofibrils within fibrin fibers have a partially ordered lateral arrangement with a characteristic transverse repeat distance of 13 nm, irrespective of the fiber thickness. These findings provide fundamental insights into the molecular structure of fibrin clots that underlies their biological and physical properties.
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Affiliation(s)
- Karin A Jansen
- AMOLF, Biological Soft Matter Group, Amsterdam, The Netherlands and UMC Utrecht, Department of Pathology, 3508 GA Utrecht, The Netherlands
| | - Artem Zhmurov
- KTH Royal Institute of Technology, Stockholm, Sweden and Sechenov University, Moscow 119991, Russian Federation
| | - Bart E Vos
- AMOLF, Biological Soft Matter Group, Amsterdam, The Netherlands and Institute of Cell Biology, Center of Molecular Biology of Inflammation, University of Münster, Münster, Germany
| | - Giuseppe Portale
- Macromolecular Chemistry and New Polymeric Materials, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Daniel Hermida-Merino
- Netherlands Organization for Scientific Research (NWO), DUBBLE CRG at the ESRF, 71 Avenue des Martyrs, 38000 Grenoble Cedex, France
| | - Rustem I Litvinov
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA and Institute of Fundamental Medicine and Biology, Kazan Federal University, 18 Kremlyovskaya St., Kazan 420008, Russian Federation
| | - Valerie Tutwiler
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Nicholas A Kurniawan
- AMOLF, Biological Soft Matter Group, Amsterdam, The Netherlands and Department of Biomedical Engineering and Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Wim Bras
- Netherlands Organization for Scientific Research (NWO), DUBBLE CRG at the ESRF, 71 Avenue des Martyrs, 38000 Grenoble Cedex, France and Chemical Sciences Division, Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge Tennessee, 37831, USA
| | - John W Weisel
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Valeri Barsegov
- Department of Chemistry, University of Massachusetts, 1 University Ave., Lowell, MA, 01854, USA.
| | - Gijsje H Koenderink
- AMOLF, Biological Soft Matter Group, Amsterdam, The Netherlands and Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Van der Maasweg 9, Delft, 2629 HZ, The Netherlands.
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Vos BE, Martinez-Torres C, Burla F, Weisel JW, Koenderink GH. Revealing the molecular origins of fibrin's elastomeric properties by in situ X-ray scattering. Acta Biomater 2020; 104:39-52. [PMID: 31923718 DOI: 10.1016/j.actbio.2020.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 01/02/2020] [Accepted: 01/02/2020] [Indexed: 01/01/2023]
Abstract
Fibrin is an elastomeric protein forming highly extensible fiber networks that provide the scaffold of blood clots. Here we reveal the molecular mechanisms that explain the large extensibility of fibrin networks by performing in situ small angle X-ray scattering measurements while applying a shear deformation. We simultaneously measure shear-induced alignment of the fibers and changes in their axially ordered molecular packing structure. We show that fibrin networks exhibit distinct structural responses that set in consecutively as the shear strain is increased. They exhibit an entropic response at small strains (<5%), followed by progressive fiber alignment (>25% strain) and finally changes in the fiber packing structure at high strain (>100%). Stretching reduces the fiber packing order and slightly increases the axial periodicity, indicative of molecular unfolding. However, the axial periodicity changes only by 0.7%, much less than the 80% length increase of the fibers, suggesting that fiber elongation mainly stems from uncoiling of the natively disordered αC-peptide linkers that laterally bond the molecules. Upon removal of the load, the network structure returns to the original isotropic state, but the fiber structure becomes more ordered and adopts a smaller packing periodicity compared to the original state. We conclude that the hierarchical packing structure of fibrin fibers, with built-in disorder, makes the fibers extensible and allows for mechanical annealing. Our results provide a basis for interpreting the molecular basis of haemostatic and thrombotic disorders associated with clotting and provide inspiration to design resilient bio-mimicking materials. STATEMENT OF SIGNIFICANCE: Fibrin provides structural integrity to blood clots and is also widely used as a scaffold for tissue engineering. To fulfill their biological functions, fibrin networks have to be simultaneously compliant like skin and resilient against rupture. Here, we unravel the structural origin underlying this remarkable mechanical behaviour. To this end, we performed in situ measurements of fibrin structure across multiple length scales by combining X-ray scattering with shear rheology. Our findings show that fibrin sustains large strains by undergoing a sequence of structural changes on different scales with increasing strain levels. This demonstrates new mechanistic aspects of an important biomaterial's structure and its mechanical function, and serves as an example in the design of biomimicking materials.
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