Fibrinogen C-terminal peptidic sequences (Haptides) modulate fibrin polymerization

Area of Science:

• Biochemistry
• Cell Biology
• Biomaterials Science

Background:

• Synthetic peptides mimicking fibrinogen C-termini, termed Haptides, were previously shown to mediate mesenchymal cell attachment.
• The functional roles of these Haptides in fibrin clot formation and platelet interactions remained to be elucidated.

Purpose of the Study:

• To evaluate the effects of Haptides on fibrin clot formation and thrombin-induced clotting.
• To investigate the potential impact of Haptides on platelet aggregation.
• To explore the self-assembly properties and ultrastructure of Haptides and their interaction with fibrinogen.

Main Methods:

• Assessment of fibrin clot turbidity and clotting time in the presence of Haptides.
• Microscopic analysis (scanning and transmission electron microscopy) of Haptide-induced precipitates.
• Binding assays using Sepharose beads coated with fibrinogen or Haptides.
• Dynamic light scattering to determine Haptide nanoparticle size.
• Platelet aggregation assays.

Main Results:

• Haptides (Cbeta, CalphaE, preCgamma) increased fibrin clot turbidity and reduced clotting time.
• High concentrations of Cbeta and preCgamma Haptides induced fibrinogen precipitation with distinct ultrastructure.
• Haptides formed nanoparticles (approx. 150 nm) in aqueous solution, suggesting a role in nucleating fibrin gel formation.
• Haptides did not bind to platelets or affect platelet aggregation up to 100 micro M.

Conclusions:

• C-terminal sequences of beta and gamma fibrinogen chains (Cbeta and preCgamma) are crucial for fibrinogen polymerization and fibrin clot assembly.
• Haptides self-assemble into nanoparticles that can accelerate fibrin gel formation.
• Haptides specifically influence fibrin polymerization and cell attachment, independent of platelet activity.