Complex strain induced structural changes observed in fibrin assembled in human plasma.

Area of Science:

• Biophysics
• Materials Science
• Hematology

Background:

• Blood clots form a fibrin fiber network crucial for hemostasis.
• Mechanical forces from clot retraction, wound repair, and blood flow significantly impact clot structure.
• Understanding fibrin's response to mechanical stress is vital for its physiological and pathological roles.

Purpose of the Study:

• To investigate the structural alterations of human plasma clots under uniaxial strain using X-ray diffraction.
• To identify and characterize changes in fibrin fiber organization and ordering in response to mechanical stress.
• To assess the resilience and recovery of fibrin clot structure after mechanical deformation.

Main Methods:

• Utilized X-ray diffraction to analyze highly aligned human plasma clots cross-linked by Factor XIIIa.
• Applied uniaxial strain (ε) to clots to quantify structural changes at varying extension levels.
• Observed changes in axial and lateral ordering of fibrin fibers as a function of applied strain and subsequent relaxation.

Main Results:

• Identified three stretch-sensitive axial repeat structures in fibrin fibers, with distinct changes occurring at specific strain levels (ε ≈ 0.20, ε ≈ 0.40).
• Observed increasing axial disordering of fibrin molecules with progressing strain, alongside the emergence and disappearance of specific structural repeats.
• Noted partial recovery of both axial and lateral order upon relaxation, indicating significant structural resilience.

Conclusions:

• Fibrin clot structure exhibits significant heterogeneity and adaptability in response to mechanical forces.
• The identified structural changes and resilience suggest that fibrin's mechanical environment plays a critical role in its function.
• These findings have potential clinical significance for understanding conditions involving clot formation, retraction, and blood flow dynamics.