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Clinical Science (2003) 104, (421–428) (Printed in Great Britain)

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Cyclical mechanical stretch enhances angiopoietin-2 and Tie2 receptor expression in cultured human umbilical vein endothelial cells

Hang CHANG*†, Bao-Wei WANG‡, Peiliang KUAN‡ and Kou-Gi SHYU‡

*The Department of Education and Research, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan, †Department of Surgery, Taipei Medical University, Taipei, Taiwan, and ‡Division of Cardiology, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan

Key words: angiopoietin-2, cell culture, cyclical stretch, gene expression, signal transduction, Tie receptor.

Abbreviations: HUVEC, human umbilical vein endothelial cell; PKC, protein kinase C; VEGF, vascular endothelial growth factor.

Correspondence: Dr Kou-Gi Shyu, MD, Division of Cardiology, 95 Wen-Chang Rd, Shin Kong Wu Ho-Su Memorial Hospital, Taipei 111, Taiwan (e-mail shyukg@ms12.hinet.net).

Endothelial cells are essential for neovascularization. Angiopoietins and Tie receptors are required for a normal vasculature. How cyclical mechanical stretch affects the expression of components of the angiopoietin system is not known. In this study, we investigated the regulation of angiopoietins and Tie receptors by cyclical mechanical stretch in cultured human umbilical vein endothelial cells (HUVECs). HUVECs grown on a flexible membrane base were stretched by vacuum to 20% elongation, at 60cycles/min. The levels of angiopoietin-2 protein began to increase as early as 2h after stretch was initially applied, reached a maximum of 2.7-fold over the control value by 6h. The Tie2 receptor protein showed the same pattern as Ang-2. These increases in angiopoietin-2 and Tie2 receptor proteins at 6h were blocked by the addition (30min before stretch) of the protein kinase C inhibitor Gö6976 (16nM) or the tyrosine kinase inhibitor herbimycin A (24µM). Similar to protein expression, the levels of angiopoietin-2 and Tie2 receptor mRNAs in HUVECs increased 3.1-fold and 2.5-fold respectively after stretch for 6h. These increases were also blocked by Gö6976 or herbimycin A. Cyclical mechanical stretch increased (and Gö6976 or herbimycin A abrogated these increases) the immunohistochemical labelling of angiopoietin-2 and Tie2 receptor after a 6h stretch. The levels of angiopoietin-1 and Tie1 receptor proteins, mRNAs and immunohistochemical staining were unaffected by cyclical mechanical stretch. Thus cyclical mechanical stretch activates the expression of angiopoietin-2 and the Tie2 receptor, but not angiopoietin-1 or the Tie1 receptor, in cultured HUVECs. This mechanical effect is probably mediated by the tyrosine kinase and protein kinase C pathways.

Received 29 July 2002/8 November 2002; accepted 21 January 2003

The Biochemical Society and the Medical Research Society © 2003