Structural and Functional Plasticity of Collagen Fibrils

Area of Science:

• Biochemistry
• Biophysics
• Materials Science

Background:

• Collagen, a key subendothelial matrix component, is crucial for hemostasis by activating and aggregating platelets at vascular injury sites.
• Type I collagen, the most prevalent form, exists in both soluble and fibrillar states, but the interchangeability between these forms remains unclear.

Purpose of the Study:

• To investigate the structural plasticity of type I collagen and its influence on platelet interactions.
• To determine the conditions governing the transition between soluble and fibrillar collagen forms.

Main Methods:

• Atomic force microscopy (AFM) was employed to visualize collagen structures and their transformations.
• Noncontact hopping probe ion-conductance microscopy was utilized to probe platelet behavior on fibrillar collagen.

Main Results:

• Type I collagen undergoes pH-dependent, ion-independent transitions between soluble and fibrillar forms.
• Fibrillar collagen, characterized by "D-bands," can be disrupted by acetic acid and reformed at neutral pH.
• Fibrillar collagen demonstrates significantly enhanced platelet activation and aggregation under both static and flow conditions compared to soluble forms.
• Platelets interacting with fibrillar collagen exhibit rapid microvesiculation, appearing as high-density bubble shapes.

Conclusions:

• Type I collagen possesses remarkable structural plasticity, enabling reversible transitions between soluble and fibrillar states.
• The fibrillar form of collagen is a potent activator of platelets, inducing significant changes in their morphology, including microvesiculation.
• Understanding these structural dynamics and their impact on platelet function is vital for comprehending hemostasis and vascular injury responses.