TGF-²1, -²2 and -²3 Cooperate to Facilitate Tubulogenesis in the Explanted Quail Heart

Background: Transforming growth factor-² (TGF-²) isoforms have been implicated as both pro- and anti-angiogenic modulators. In this study we addressed the roles of TGF-² isoforms on coronary tubulogenesis. Methods: Embryonic (E6) quail ventricular specimens were explanted onto collagen gels allowing endothelial cells to migrate and form vascular tubes. Growth factors and/or neutralizing growth factor antibodies were added to the cultures. Endothelial cells were identified using a quail endothelial cell marker, QH1. Image analysis was used to quantify aggregate tube length. Results: Addition of any isoform (TGF-²1, TGF-²2 or TGF-²3) virtually prevented tubulogenesis (>95% inhibition), while stimulation of tubulogenesis occurred by adding neutralizing antibodies to TGF-²3, but not to TGF-²1 or -²2. When all three isoforms were added, tubulogenesis was enhanced, indicating the key role of TGF-²3. Documentation of the inhibitory effect of TGF-² isoforms on tubulogenesis is further supported by our experiments in which the marked enhancement of tube formation by bFGF and VEGF was negated when exogenous TGF-²1, -²2, or -²3 were added to the cultures. Conclusions: (1) TGF-²1, -²2 and -²3 each inhibits angiogenesis; (2) cooperation between the three TGF-² isoforms and other angiogenic factors is essential for the regulation of normal tubulogenesis and (3) the stimulatory effect of VEGF or bFGF on tubulogenesis is negated by exogenous TGB-²s. Copyright © 2004 S. Karger AG, Basel