(314a) The Effect of Soluble Factors on the Morphological, Adhesive, and Mechanical Properties of Human Bone Marrow Endothelial Cells

The process of angiogenesis, which is the formation of new blood vessels from pre-existing vessels, involves endothelial cell proliferation, adhesion, migration, and tube formation.  Angiogenesis plays a critical role in many stages of tumor progression including tumor growth and metastasis.  Vascular endothelial growth factor (VEGF) is an important pro-angiogenic soluble factor that has been the target of many cancer therapies [1].

We characterized the effect that VEGF had on the morphological and mechanical properties of human bone marrow endothelial cells.  Surprisingly, VEGF treatment did not result in significant changes in endothelial cell morphology, characterized by cell shape factor and spread area.  We investigated the mechanical properties of cells treated with VEGF on matrigel-coated glass by utilizing multiple particle-tracking microrheology (MPTM) [2].  Mean-squared displacements (MSDs) of nanoparticles embedded in the cytoplasm and the frequency-dependent viscoelastic moduli of the cytoplasm were calculated.  No significant changes were observed in the mechanical properties of endothelial cells stimulated with VEGF, as these cells had similar elastic modulus (Gʹ) and viscous modulus (Gʺ) compared to control cells.  We also generated thin-layered Matrigel coated coverslips (“Matrigel Discs”) that enabled us to perform MPTM on endothelial cells forming tube-like structures.  No significant changes were observed in the mechanical properties of the endothelial cells in the tube formation assay.

We performed a molecular screen with various soluble factors present in the tumor and tissue microenvironments, including VEGF, FGF, PDGF, TGF-β1, and IGF-1, to identify a growth factor that could be used to stimulate tube formation in human bone marrow endothelial cells. Insulin-like growth factor-1 (IGF-1) treatment resulted in the best tube network in the shortest amount of time. Therefore, we will characterize the effects of IGF-1, in comparison to VEGF, on the properties of human bone marrow endothelial cells, including cell mechanics.

1. Hoeben, A., et al., Vascular Endothelial Growth Factor and Angiogenesis. Pharmacological Reviews, 2004. 56(4): p. 549-580.

2. Wirtz, D., Particle-tracking microrheology of living cells: principles and applications. Annual review of biophysics, 2009. 38: p. 301-326.