Molecular weight fibrinogen variants alter gene expression and functional characteristics of human endothelial cells

Molecular weight fibrinogen variants alter gene expression and functional characteristics of human endothelial cells

E. M. Weijers, M. H. Van Wijhe, L. Joosten, A. J. G. Horrevoets, M. P. M. De Maat, V. W. M. Van Hinsbergh, P. Koolwijk

Journal of Thrombosis and Haemostasis Accepted Article (Accepted, unedited articles published online for future issues) doi/ 10.1111/j.1538-7836.2010.04096.x


Background: Fibrin is a temporary matrix, which not only seals a wound, but also provides a temporary matrix structure for invading cells during wound healing. Two naturally occurring fibrinogen variants, high molecular weight (HMW) and low molecular weight (LMW) fibrinogen, display different properties in supporting angiogenesis in vivo and in vitro.
Objectives: This study aims to investigate the functional characteristics and molecular mechanisms of human microvascular endothelial cells (HMVEC) cultured on HMW- and LMW-fibrin matrices. Methods and
Results: HMVEC on HMW-fibrin matrices showed increased proliferation and tube formation as compared to their counterparts on unfractionated- and LMW-fibrin. Degradation of HMW-fibrin was markedly enhanced by the presence of HMVEC, that of LMW-fibrin only slightly. However, the expression of fibrinolysis regulating proteins and integrins were similar. Subsequent micro-array analysis revealed that the expression of 377 genes differed significantly between HMVEC cultured on HMW- and LMW-fibrin. Among these genes UNC5B, DLL4 and DLL4-Notch downstream targets Hey1, Hey2 and Hes1 were increased in HMVEC on LMW-fibrin. However, pharmacological and genetic (DLL4 siRNA) inhibition DLL4-Notch signaling blunted rather than enhanced proliferation and tube formation by HMVEC on both fibrin variants.
Conclusions: Heterogeneity in natural occurring fibrinogen strongly influences endothelial cell proliferation and tube formation and causes alterations in gene expressions, including that of DLL4-Notch. The higher fibrinolytic sensitivity of HMW-fibrin in the presence of HMVEC contributes to increased tube formation. While DLL4-Notch was altered, it did not explain the enhanced tube formation in HMW-fibrin. This study provides new perspectives for biological and tissue engineering applications.

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