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In vivo Chick Chorioallantoic Membrane (CAM) Angiogenesis Assays

Zhenguo Chen, Zhihua Wen and Xiaochun Bai*

Department of Cell Biology, Southern Medical University, Guangzhou, China

*For correspondence: baixc15@smu.edu.cn

[Abstract] Angiogenesis is the process of formation of new blood vessels from pre-existing

vessels or endothelial cell progenitors. It plays a crucial role in tumor growth and metastasis.

Tumor angiogenesis have been widely studied as an important target for

suppressing tumor growth and metastasis. Here, we describe an in vivo chick embryo

chorioallantoic membrane (CAM) model. The chick embryo chorioallantoic membrane is an

extraembryonic and is rich of blood vessels. After exposing the vascular zone of the CAM, a

sterilized filter-paper disk is employed, which is used as a carrier for being loaded with various

chemicals, drugs or virus. Finally, the CAM was fixed and spread on glass slide, and the blood

vessels were quantified by counting the number of blood vessel branch points. Compared with the

matrigel plug angiogenesis assay, in which tumor cells are mixed with the matrigel gel (expensive)

and injected into the mice, subsequently using immunohistochemistry (IHC) staining (time

consuming) with the endothelial marker to indicate the presence of the newly formed capillaries,

the main advantages of CAM model are its low cost, simplicity, reproducibility, and reliability. Thus,

the CAM can be widely used in vivo to study both angiogenesis and anti-angiogenesis.

Materials and Reagents

1. Fertilized E6 chicken embryos (from Poultry Center of South China Agricultural University)

2. 0.1% Benzalkonium Bromide (from Guangzhou Chemical Reagent Factory, diluted in

sterile water before use)

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3. Methanol and acetone (1:1 in volume)

4. Filter-paper disk (Whatman, catalog number: 1441150)

5. Packing film (Parafilm)

Equipment

1. Incubator

2. Glass slide

3. Ophthalmic forceps

Procedure

1. Fertilized E6 chicken embryos (48 ± 5 g) were cleaned with 0.1% Benzalkonium Bromide

and preincubated at 37.5 °C in 85% humidity for 2 days.

2. Egg morphology appears like a meta-ellipse, with a relatively larger side and a smaller

one, and the air sac is usually located on the larger side right behind the shell. After

disinfection of the shell center outside the air sac with 0.1% Benzalkonium Bromide, a

hole highlighted with marker pen was buffed and drilled gently over the air sac with a

nipper not to break the shell, and the vascular zone was easy to be identified on the CAM

(Figure 1).

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Figure 1. The vascular zone of the CAM

3. Two drops of normal saline were then added to moisten the inner shell membrane

adjacent to the CAM so that the membrane was easy to be separated from CAM.

4. After being clamped and raised by ophthalmic forceps, the membrane and the CAM

separated unforcedly, and then a 1 x 1 cm window on the membrane was sectioned to

expose the vascular zone.

5. A 5 mm x 5 mm sterilized filter-paper disks, which were used as a carrier for being directly

loaded with indicated concentrations of chemicals or virus, were then directly applied and

adhere to the vascular zone with right density of vascular.

6. Upon sealing the openings with sterile flexible packing film, the eggs were further

incubated for indicated periods.

7. Finally, a mix of methanol and acetone (1:1 in volume) was directly added to immerse and

fix the blood vessels of the experiment zone.

8. After being clamped and raised by ophthalmic forceps, the CAM was easy to be separated

from the embryo, and it was cut and spread on glass slide, and the blood vessels were

viewed, photographed and quantified by counting the number of blood vessel branch

points. (Figure 2).

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Figure 2. Blood vessel branch points on CAM. Arrow indicates new-formed blood

vessel branches.

Acknowledgments

This protocol was adapted from the following published papers: Wen et al. (2013); Chen et al.

(2014). This work was supported by The State Key Development Program for Basic Research

of China (2009CB 918904, 2013CB945203), National Natural Sciences Foundation of China

(30870955, 91029727, 30900555) and Program for New Century Excellent Talents in

University (NCET-08-0646).

References

1. Chen, Z., Zhang, Y., Jia, C., Wang, Y., Lai, P., Zhou, X., Wang, Y., Song, Q., Lin, J., Ren,

Z., Gao, Q., Zhao, Z., Zheng, H., Wan, Z., Gao, T., Zhao, A., Dai, Y. and Bai, X. (2014).

mTORC1/2 targeted by n-3 polyunsaturated fatty acids in the prevention of mammary

tumorigenesis and tumor progression. Oncogene 33(37): 4548-4557.

2. Wen, Z. H., Su, Y. C., Lai, P. L., Zhang, Y., Xu, Y. F., Zhao, A., Yao, G. Y., Jia, C. H., Lin,

J., Xu, S., Wang, L., Wang, X. K., Liu, A. L., Jiang, Y., Dai, Y. F. and Bai, X. C. (2013).

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Critical role of arachidonic acid-activated mTOR signaling in breast carcinogenesis and

angiogenesis. Oncogene 32(2): 160-170.

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