Abstract 11760: Extracellular Bone Morphogenetic Protein Modulators Twisted Gastrulation and BMPER Fine-Tune Blood Vessel Formation
Introduction: Growth and regeneration of blood vessels are crucial processes during embryonic development and in adult health and disease. After tissue injury such as myocadial infarction many signaling pathways are reactivated to repair the damaged tissue and restore vascularization. Growth factors of the bone morphogenetic protein (BMP) family are known to play a key role in vascular development. In this project we investigate the role of the BMP modulator twisted gastrulation (Tsg) in vascular development and endothelial cell function.
Methods and results: First, we determined a high expression level of Tsg in endothelial cells of different origin by RT-PCR, western blotting and immunocytochemistry. To assess the effects of Tsg on endothelial cell function we used the in vitro matrigel sprouting assay and a proliferation assay. Compared to control, stimulation of human umbilical vein endothelial cells (HUVECs) with Tsg enhanced endothelial cell sprouting and proliferation by up to 180% in a concentration dependent fashion. To confirm these findings in vivo we subjected C57BL/6 mice to subcutaneous matrigel injections. Indeed, when the matrigel plug contained Tsg (500 ng/ml; n=3) the number of ingrowing vessels was enhanced by 225% compared to control plaques without Tsg (n=3). Inhibition of Tsg by specific morpholinos in zebrafish resulted in modification of intersomitic vessels and formation of a large AV shunt in the trunk. Mechanistically, we found the Akt and Erk 1/2 pathway to be involved in Tsg induced angiogenesis. Addition of Erk inhibitor U0126 or Akt inhibitor wortmannin abolished Tsg stimulated matrigel sprouting down to 58% or 56%, respectively. Interestingly, the concomitant addition of BMPER -a BMP modulator that itself has proangiogenic properties- abolished the pro-angiogenic Tsg effect. Moreover, the inhibition of Tsg using siRNA-mediated knock down in endothelial cells again enhanced sprouting (148%) and downstream signaling pathway phosphorylation.
Conclusion: Stable Tsg levels are needed for blood vessel homeostasis. BMPER rescues Tsg deviations suggesting that BMP pathway activity is controlled by a fine-tuned equilibrium, which is necessary for regular endothelial cell function.
- © 2011 by American Heart Association, Inc.