Haemostasis Research Group, Department of Molecular and Cellular Therapeutics, Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, Dublin, Ireland.
National Coagulation Centre, St James's Hospital, Dublin, Ireland.
Blood. 2019 Apr 4;133(14):1585-1596. doi: 10.1182/blood-2018-09-874636. Epub 2019 Feb 15.
Glycan determinants on von Willebrand factor (VWF) play critical roles in regulating its susceptibility to proteolysis and clearance. Abnormal glycosylation has been shown to cause von Willebrand disease (VWD) in a number of different mouse models. However, because of the significant technical challenges associated with accurate assessment of VWF glycan composition, the importance of carbohydrates in human VWD pathogenesis remains largely unexplored. To address this, we developed a novel lectin-binding panel to enable human VWF glycan characterization. This methodology was then used to study glycan expression in a cohort of 110 patients with low VWF compared with O blood group-matched healthy controls. Interestingly, significant interindividual heterogeneity in VWF glycan expression was seen in the healthy control population. This variation included terminal sialylation and ABO(H) blood group expression on VWF. Importantly, we also observed evidence of aberrant glycosylation in a subgroup of patients with low VWF. In particular, terminal α(2-6)-linked sialylation was reduced in patients with low VWF, with a secondary increase in galactose (Gal) exposure. Furthermore, an inverse correlation between Gal exposure and estimated VWF half-life was observed in those patients with enhanced VWF clearance. Together, these findings support the hypothesis that loss of terminal sialylation contributes to the pathophysiology underpinning low VWF in at least a subgroup of patients by promoting enhanced clearance. In addition, alterations in VWF carbohydrate expression are likely to contribute to quantitative and qualitative variations in VWF levels in the normal population. This trial was registered at www.clinicaltrials.gov as #NCT03167320.
糖基决定簇在血管性血友病因子（VWF）上起着关键作用，可调节其对蛋白水解和清除的易感性。在许多不同的小鼠模型中，异常的糖基化已被证明可导致血管性血友病（VWD）。然而，由于准确评估 VWF 聚糖组成所面临的重大技术挑战，碳水化合物在人类 VWD 发病机制中的重要性在很大程度上仍未得到探索。为了解决这个问题，我们开发了一种新的凝集素结合谱来实现人类 VWF 聚糖特征分析。然后，我们使用这种方法研究了 110 名 VWF 水平低的患者与 O 型血匹配的健康对照组之间的聚糖表达。有趣的是，在健康对照组人群中，VWF 聚糖表达存在显著的个体间异质性。这种差异包括 VWF 上末端唾液酸化和 ABO(H)血型表达。重要的是，我们还观察到在 VWF 水平低的亚组患者中存在异常糖基化的证据。特别是，VWF 水平低的患者末端α(2-6)-连接唾液酸化减少，半乳糖（Gal）暴露增加。此外，在清除增强的那些患者中，Gal 暴露与估计的 VWF 半衰期之间存在反比关系。这些发现支持了这样一种假设，即末端唾液酸化的丧失通过促进增强清除，至少在一部分 VWF 水平低的患者中导致了 VWF 低水平的病理生理学。此外，VWF 碳水化合物表达的改变可能导致正常人群中 VWF 水平的定量和定性变化。该试验在 www.clinicaltrials.gov 上注册，编号为 #NCT03167320。
