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Endogenous basic fibroblast growth factor is implicated in the vascularization of the chick embryo chorioallantoic
D Ribatti1, C Urbinati, B Nico
1Institute of Human Anatomy, Histology and Embryology, School of Medicine, University of Bari, Italy.
Insights
Basic fibroblast growth factor (bFGF) in chick embryos is crucial for blood vessel development in the chorioallantoic membrane (CAM). Its concentration peaks mid-incubation, with higher levels in the CAM than fluid, suggesting a key role in vascularization.
Area of Science:
- Developmental Biology
- Angiogenesis Research
- Molecular Biology
Background:
- Basic fibroblast growth factor (bFGF) is a key signaling molecule in development.
- Its role in chick embryo vascularization, specifically the chorioallantoic membrane (CAM), requires further elucidation.
Purpose of the Study:
- To investigate the presence, levels, and function of basic fibroblast growth factor (bFGF) in the chick embryo's chorioallantoic membrane (CAM) and chorioallantoic fluid (CAF).
- To determine the role of endogenous bFGF in CAM vascularization during embryogenesis.
Main Methods:
- Detection and quantification of immunoreactive and biologically active bFGF in CAM and CAF using molecular weight, heparin affinity, and cell-based assays.
- Administration of human recombinant bFGF and anti-bFGF antibodies onto the CAM surface or via allantoic sac injection.
- Macroscopic and microscopic evaluation of CAM vasoproliferative processes.
Main Results:
- An M(r) 16,000 bFGF-like molecule, identified as bFGF, was present in both CAM and CAF.
- Biologically active and immunoreactive bFGF levels peaked between Days 10-14 of incubation, with significantly higher concentrations in CAM tissue than in CAF.
- Application of bFGF to the CAM surface promoted angiogenesis, while anti-bFGF antibodies inhibited it; injection into the allantoic sac had no effect.
Conclusions:
- Endogenous bFGF plays a rate-limiting role in the vascularization of the chick embryo's chorioallantoic membrane.
- bFGF localized within the CAM tissue, not the CAF, is primarily involved in this developmental process.
Abstract:
Chorioallantoic membrane (CAM) and chorioallantoic fluid (CAF) of the chick embryo were studied for the presence of immunoreactive and biologically active basic fibroblast growth factor (bFGF) from Day 6 to Day 18 of incubation. An immunoreactive M(r) 16,000 bFGF-like molecule was detected both in CAM and in CAF. This molecule was identified as bFGF on the basis of its molecular weight, its affinity for heparin, and its capacity to induce plasminogen activator production in cultured endothelial GM 7373 cells. The levels of biologically active and immunoreactive bFGF vary in CAM and CAF during embryonic development, maximal concentrations being observed between Days 10 and 14 of incubation. At all time points investigated, absolute concentrations of bFGF were significantly higher in CAM (ranging from 25 to 183 ng/g of wet tissue) than in CAF (ranging from 0.2 to 4 ng/ml). In a parallel series of experiments performed at Day 8 and evaluated at Day 12 of chick embryo development, human recombinant bFGF and neutralizing anti-bFGF antibody were investigated for their capacity to affect the vasoproliferative processes of the CAM. The two molecules either were applied onto the surface of the CAM or were injected into the allantoic sac. When bFGF or anti-bFGF antibodies were absorbed on methylcellulose discs and applied on the top of the CAM, they exerted a strong angiogenic or anti-angiogenic effect, respectively. On the contrary, when bFGF or the corresponding neutralizing antibody was injected into the allantoic sac, no modifications of the vasoproliferative processes of the CAM were observed at either the macroscopic or the microscopic level. These results provide evidence indicating that endogenous bFGF has a rate-limiting role in the vascularization of the CAM during chick embryogenesis. bFGF located within the CAM, rather than that present in the CAF, appears to be involved in this developmental process.