Levels of Von Willebrand Factor Multimers and VWF-Cleaving Protease (ADAMTS-13) in Preterm and Neonate

Von Willebramd Factor (VWF) is an adhesive glycoprotein synthesized by megakaryocytes and endothelial cells.VWF has a central role in primary hemostasis and is a critical ligand for platelets adhesion and aggregation (1, 2).VWF is the carrier of circulating factor 8 as well. VWF is stored in Wiebel-Palade bodies in endothelial cells and in platelets alfa granules in a form of Ultra-large (UL) multimers.

The VWF multimers are composed from subunits which are linked by disulfide bonds that alternate between 2 C- terminal ends and 2 N- terminal ends in a head-to-head and tail-to-tail fashion (3, 4). The biological activity of VWF has been shown to be related to the size of the multimers.

VWF is released from endothelial cells toward the plasma as a multimers ranging from 500-20,000 kD. The UL multimers are hemostaticallly more effective than the smaller forms. They spontaneously bind to platelets which lead to the formation of microthrombi in the circulation. This mechanism is downregulated by the plasma protease ADAMTS-13(A Disintegrin And Metalloprotease with ThromboSpondin motif).If the proteolysis become defective the ULVWF will bind to platlets resulting in systemic thrombotic microangiophaties (TMA) such as thrombotic thrombocytopenic purpura(TTP)(5,6).

ADAMTS-13 belongs to the ADAMTS family of metalloproteases.The structure of ADAMTS-13 is conserved throughout vertebrates, indicating its important function (7).The metalloprotease function was first describe 11 years ago and has been cloned and characterized (8-13).The ADAMTS family of metaloploproteases is required in other systems such as genitourinary system (ADAMTS1), collagen system (ADAMTS2) and as a cleaving protease of VWF (VWFCP) - ADAMTS13. When VWF multimer is subjected to sufficient fluid shear stress ADAMTS-13 cleaves VWF at a unique 842Tyr- 843Met bond in domain A2 (14,15).This cleavage produce VWF subunit fragments of 176 kDa and 140 kDa.

The activity of ADAMTS-13 depends on both Zn+2 and Ca+2 ions (16). Low levels or deficiency of ADAMTS-13 is seen in patient with TTP(17,18). Mannuccio et al (19) showed that low levels of ADAMTS-13 are seen in other conditions such as healthy adults older than 65 years, patients with cirrhosis, uremia, acute inflammation, postoperative period. In neonate and preterm infants the data is limited. Few studies have shown that levels of ADAMTS-13 are low in neonate (19-21).Tsai et al (22) observed that ADAMTS-13 activity is normal in cord blood compared to adults. In preterm infants a pilot study showed that preterm have low levels of ADAMTS-13(23).

The aim of our study is to check ADAMTS-13, VWF multimers, VWF antigen and VWF collagen binding activity in healthy and sick neonate and in preterm infants.

Study Overview

• Status: Unknown
• Conditions: Von Willebramd Factor

• Study Type: Observational
• Enrollment (Anticipated): 100

Contacts and Locations

• Study Contact: Name: tzipora strauss, M.D; Phone Number: 972-5-2666-4446; Email: t.tzipi@gmail.com

Study Locations

• Israel
  • Ramat-Gan, Israel, 52621
    • Recruiting
    • Sheba-Medical-Center
    • Contact: tzipora strauss, M.D; Phone Number: 972-5-2666-4446; Email: t.zipi@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 5 months to 9 months (CHILD)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

All infants born n our hospital between August 2007 and August 2009 will enter

Description

Inclusion Criteria:

• All infants born n our hospital between August 2007 and August 2009 will enter

Exclusion Criteria:

• Thrombocytopenia, maternal aspirin

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
1; All infants born in our hospital between August 2007 and August 2009 will participate.

Collaborators and Investigators

• Sponsor: Sheba Medical Center

Study record dates

Study Major Dates

• Study Start: August 1, 2007
• Primary Completion (ANTICIPATED): August 1, 2008
• Study Completion (ANTICIPATED): August 1, 2009

Study Registration Dates

• First Submitted: June 18, 2008
• First Submitted That Met QC Criteria: June 18, 2008
• First Posted (ESTIMATE): June 19, 2008

Study Record Updates

• Last Update Posted (ESTIMATE): June 19, 2008
• Last Update Submitted That Met QC Criteria: June 18, 2008
• Last Verified: July 1, 2007

More Information

Terms related to this study

• Keywords: Von Willebramd Factor (VWF); All infants born in our hospital since August 2007 ill august 2009 will enter.; Therombocytopenia, maternal aspirin will be excluded
• Other Study ID Numbers: SHEBA-08-4132-TS-CTIL