title: Decreased cell adhesion promotes angiogenesis in a Pyk2-dependent manner.
abstract: Angiogenesis is regulated by both soluble growth factors and cellular interactions with the extracellular matrix (ECM). While cell adhesion via integrins has been shown to be required for angiogenesis, the effects of quantitative changes in cell adhesion and spreading against the ECM remain less clear. Here, we show that angiogenic sprouting in natural and engineered three-dimensional matrices exhibited a biphasic response, with peak sprouting when adhesion to the matrix was limited to intermediate levels. Examining changes in global gene expression to determine a genetic basis for this response, we demonstrate a vascular endothelial growth factor (VEGF)-induced upregulation of genes associated with vascular invasion and remodeling when cell adhesion was limited, whereas cells on highly adhesive surfaces upregulated genes associated with proliferation. To explore a mechanistic basis for this effect, we turned to focal adhesion kinase (FAK), a central player in adhesion signaling previously implicated in angiogenesis, and its homologue, proline-rich tyrosine kinase 2 (Pyk2). While FAK signaling had some impact, our results suggested that Pyk2 can regulate both gene expression and endothelial sprouting through its enhanced activation by VEGF in limited adhesion contexts. We also demonstrate decreased sprouting of tissue explants from Pyk2-null mice as compared to wild type mice as further confirmation of the role of Pyk2 in angiogenic sprouting. These results suggest a surprising finding that limited cell adhesion can enhance endothelial responsiveness to VEGF and demonstrate a novel role for Pyk2 in the adhesive regulation of angiogenesis.
authors.affiliation: Department of Bioengineering, University of Pennsylvania, 210 South 33rd Street, Philadelphia, PA 19104, USA.
authors.forename: Colette J
authors.initials: CJ
authors.lastname: Shen
authors.forename: Srivatsan
authors.initials: S
authors.lastname: Raghavan
authors.forename: Zhe
authors.initials: Z
authors.lastname: Xu
authors.forename: Jan D
authors.initials: JD
authors.lastname: Baranski
authors.forename: Xiang
authors.initials: X
authors.lastname: Yu
authors.forename: Michele A
authors.initials: MA
authors.lastname: Wozniak
authors.forename: Jordan S
authors.initials: JS
authors.lastname: Miller
authors.forename: Mudit
authors.initials: M
authors.lastname: Gupta
authors.forename: Leonard
authors.initials: L
authors.lastname: Buckbinder
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Chen
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000378:metabolism; D051418:Focal Adhesion Kinase 2 / Q000172:deficiency / Q000378:metabolism*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D008024:Ligands; D051379:Mice; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic / Q000235:genetics; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D008024:Ligands; D042461:Vascular Endothelial Growth Factor A; D051418:Focal Adhesion Kinase 2; D051416:Focal Adhesion Protein-Tyrosine Kinases