Association between bleeding time and platelet adherence to artery subendothelium

Area of Science:

• Hematology
• Vascular Biology
• Biochemistry

Background:

• Von Willebrand factor (VWF) is crucial for platelet adhesion to damaged blood vessels.
• Deficiencies in VWF cause von Willebrand's disease (VWD), leading to bleeding disorders.
• Effective VWF replacement therapy requires preparations that restore normal platelet function.

Purpose of the Study:

• To assess the efficacy of different factor VIII-von Willebrand factor (FVIII-VWF) preparations in promoting platelet adherence.
• To evaluate FVIII-VWF preparations as potential treatments for von Willebrand's disease (VWD).
• To validate an in vitro platelet adherence assay for testing FVIII-VWF preparation efficacy.

Main Methods:

• Utilized an annular perfusion chamber with human arteries and reconstituted blood to test FVIII-VWF preparations.
• Compared purified FVIII-VWF, cryoprecipitate, a commercial concentrate (Hemofil), and a high-purity concentrate (Concentrate II).
• Assessed platelet adherence and bleeding times in plasma from normal subjects and VWD patients.

Main Results:

• Purified FVIII-VWF, cryoprecipitate, and Concentrate II effectively mediated platelet adherence.
• Commercial Hemofil concentrate showed impaired platelet adherence compared to normal levels.
• Concentrate II normalized platelet adherence and bleeding time in VWD patient plasma.

Conclusions:

• High-purity FVIII-VWF preparations (like Concentrate II) and cryoprecipitate are effective in restoring platelet adherence.
• The developed platelet adherence assay is an efficient in vitro tool for evaluating FVIII-VWF preparations for VWD.
• Commercial FVIII-VWF concentrates may not be as effective as purer preparations in restoring normal hemostasis.