Fibroblast growth factor 2 is a key determinant of vascular sprouting during bovine luteal angiogenesis

Abstract

Fibroblast growth factor (FGF) 2 and vascular endothelial growth factor (VEGF) A are thought to be key controllers of luteal angiogenesis; however, their precise roles in the regulation and coordination of this complex process remain unknown. Thus, the temporal and spatial patterns of endothelial network formation were determined by culturing mixed cell types from early bovine corpora lutea on fibronectin in the presence of FGF2 and VEGFA (6 h to 9 days). Endothelial cells, as determined by von Willebrand factor immunohistochemistry, initially grew in cell islands (days 0-3), before undergoing a period of vascular sprouting to display a more tubule-like appearance (days 3-6), and after 9 days in culture had formed extensive intricate networks. Mixed populations of luteal cells were treated with SU1498 (VEGF receptor 2 inhibitor) or SU5402 (FGF receptor 1 inhibitor) or control on days 0-3, 3-6 or 6-9 to determine the role of FGF2 and VEGFA during these specific windows. The total area of endothelial cells was unaffected by SU1498 treatment during any window. In contrast, SU5402 treatment caused maximal reduction in the total area of endothelial cell networks on days 3-6 vs controls (mean reduction 81%; P!0.001) during the period of tubule initiation. Moreover, SU5402 treatment on days 3-6 dramatically reduced the total number of branch points (P!0.001) and degree of branching per endothelial cell island (P!0.05) in the absence of changes in mean island area. This suggests that FGF2 is a key determinant of vascular sprouting and hence critical to luteal development.

Human Vascular Tissue Models Formed from Human Induced Pluripotent Stem Cell Derived Endothelial Cells

“…6B) suggesting a role for FGF2/FGFR signaling in promoting maximal sprout formation that is consistent with previous studies examining bovine luteal endothelial cell tube formation[62]. These results are also consistent with previously reported roles for FGF2/FGFR signaling in promoting EC sprouting[50, 62, 69] and increasing vascular integrity independently of VEGF/VEGFR2 signaling[70]. We posit that VEGF signaling may provide a “switch” from a sprouting phenotype to a single cell migration phenotype that is relevant to therapeutic strategies and may provide an explanation for the limited efficacy of anti-angiogenesis therapies targeting VEGF alone.…”

“…However, iPSC-EC sprouting was completely abolished by the combined VEGFR2/FGFR inhibitor SU5402 [68] (Fig. 6B) suggesting a role for FGF2/FGFR signaling in promoting maximal sprout formation that is consistent with previous studies examining bovine luteal endothelial cell tube formation[62]. These results are also consistent with previously reported roles for FGF2/FGFR signaling in promoting EC sprouting[50, 62, 69] and increasing vascular integrity independently of VEGF/VEGFR2 signaling[70].…”

“…Further, SU5402 inhibition of iPSC-EC proliferation is in agreement with previously measured potency of SU5402 for inhibiting primary EC proliferation[68]. The observed inhibition of VEGF-dependent iPSC-EC sprouting at 1 µM SU5402 is consistent with previously measured SU5402 inhibition of VEGF- and FGF2-dependent tubule network formation for primary ECs[62, 72]. These studies highlight the importance of context for drug screening applications, as growth factor signaling[61, 73, 74] and the cellular cytoskeleton[54] exhibit different effects on EC function ( i.e.…”

“…7A) and FGFR/VEGFR2 signaling (Fig. 6B, 7B), consistent with the role of VEGF/VEGFR2 and FGF2/FGFR signaling for promoting endothelial cell sprouting[62]. We also observed complete inhibition of iPSC-EC sprouting in the presence of PD0325901 (Fig.…”

The Mandibular Ridge Oral Mucosa Model of Stromal Influences on the Endothelial Tip Cells: An Immunohistochemical and TEM Study

“…Specifically, MCs products stimulate migration and/or proliferation of endothelial cells and degrade the extracellular matrix to provide space for angiogenic sprouts to form, PDGF facilitates the recruitment of MCs to sites of angiogenesis, and the MC tryptase is an angiogenesis-inducing molecule (Meininger and Zetter, 1992;Metcalfe et al, 1997;Norrby, 2002;Ribatti et al, 2002). FGF acts also as a key factor in sprouting angiogenesis (Tepper et al, 2005;Woad et al, 2012). FGF2 was consistently expressed in non-reparatory, but not in reparatory samples; this suggests that FGF2 acts in physiological reparatory processes, but it may not intervene in wound healing.…”