Angiogenesis in vivo

The advantages of in vitro assays are (1) the ability to control the assay variables, (2) the potential opportunity to study the various steps within the complete process, (3) cellular and molecular events can be more carefully monitored and (4) the costs and the duration of the experiments are often lower than those of in vivo assays. The disadvantages of in vitro assays are that the cells, reagents and conditions used in different laboratories are not standardized and that the in vitro effects seen, do not always match the activities observed in vivo. This has been demonstrated for e.g. TNFa, which inhibits angiogenesis in vitro, but induces angiogenesis in vivo [6]. Particularly in the light of the possible influence of various cells of the immune system on angiogenesis, extrapolation of data from in vitro to in vivo needs to be carefully addressed. 

It is well recognized that in vitro angiogenesis assays can have clear advantages. However, the major drawback of all of these assays is that they require the endothelial cells to be removed from their natural microenvironment, which alters their physiological properties. To study angiogenesis in vivo, the most frequently used assay systems exploit chicken chorio-allanto-ic membrane (CAM) [28,60], the corneal pocket [61], transparent chamber preparations such as the dorsal skin fold chamber [62,63], the cheek pouch window [64] and polymer matrix implants [65,66]. 

Furthermore, it was indicated that miR-17-19b cluster included in miR-17-92 cluster inhibited apoptotic cell death, and accelerated c-Myc-induced lymphomagenesis in mice reconstituted with miR-17-19b cluster-over-expressed haematopoietic stem cells (43). In addition, the miR-17-92 cluster has been reported to augment angiogenesis in vivo by down-regulation of anti-angiogenic thrombospondin-1 and coimective tissue growth factor in Ras-transformed colonoc Tes (45). 

FGF — Angiogenesis in vivo, endothelial cell chemotaxis and growth IFN-y Endothelial cells, myoblasts... 

Electrical stimulation of skeletal muscle, either directly or via chronic motor nerve stimulation demonstrate increased VEGF production that leads to angiogenesis in vivo. 

Ueno H, Li JJ, Masuda S, Qi Z, Yamamoto H, Takeshita A, Adenovirus-mediated expression of the secreted form of basic fibroblast growth factor (FGF-2) induces cellular proliferation and angiogenesis in vivo, Arterioscler Thromb Vase Biol I 997 ... 

Asahara T, Bauters C, Zheng LR et al. Synergistic effect of vascular endothelial growth factor and basic fibroblast growth factor on angiogenesis in vivo. Circulation 1995 92(9 suppl) M365—11371,... 

Grgic, I., Eichler, I., Heinau, P., Si, H., Brakemeier, S., Hoyer, J., and Kohler, R. 2005. Selective blockade of the intermediate-conductance Ca2+-activated K+ channel suppresses proliferation of microvascular and macrovascular endothelial cells and angiogenesis in vivo. Arterioscler. Thromb. Vase. Biol. 25 704-709. 

Sundberg C, Kowanetz M, Brown LF, Detmar M, Dvorak HF. Stable expression of angiopoietin-1 and other markers by cultured pericytes Phenotypic similarities to a subpopulation of cells in maturing vessels during later stages of angiogenesis in vivo. Lab Invest 2002 82 387-401. 

Ziche M, Morbidelli L, Masini E, Amerini S, Granger HJ, Maggi CA, et al. Nitric oxide mediates angiogenesis in vivo and endothelial cell growth and migration in vitro promoted by substance P. J Clin Invest 1994 94 2036-2044. 

CGP41251 shows multiple modes of action including inhibition of angiogenesis in vivo. 

Passaniti et al described a simple adaptation of the cutaneous implant assays using reconstituted BMs (Passaniti et al., 1992). The group of Albini in Genova (1) has extensively used reconstituted BMs to study specific steps of the angiogenic process in vitro and assess angiogenesis in vivo (Albini et al., 1994, 1995 Benelli et al., 1994 lurlaro et al., 1998). The use of reconstituted BMs has several advantages both in vitro and in vivo. 

The recent identification of lysoPLD as autotaxin (ATX) has been particularly helpful for understanding LPA pathways. ATX was first identified as a protein in melanoma cell culture medium that stimulated cancer cell motility (Murata et al. 1994 Stracke et al. 1992). ATX has a single transmembrane domain, two somatomedin B-like domains, and a catalytic domain (Stracke et al. 1997). ATX is most likely cleaved intracellularly, then released into the extracellular environment. ATX was initially proposed to function as a nucleotide phosphodiesterase, but the role of this activity in ATX function is currently unclear (Bollen et al. 2000 Coding et al. 1998). In addition to its ability to promote cancer cell motility, ATX has also been shown to promote angiogenesis in vivo (Nam et al. 2001). These results support the view that ATX is an important factor in cancer biology. 

Laterra J, Nam M, Rosen E, Rao JS, Lamszus K. 1997. Scatter factor/hepatocyte growth factor gene transfer enhances glioma growth and angiogenesis in vivo. Lab Invest 76 565-577. 

Casanova ML, Blazquez C, Martinez-Palacio J, Villanueva C, Fernandez-Acenero MJ, Huffman JW, Jorcano JL, Guzman M (2003) Inhibition of skin tumor growth and angiogenesis in vivo by activation of cannabinoid receptors. J Clin Invest 111 43-50... 

Oikawa, T Onozawa, C., Kuranuki, S et al. (2007). Dipalmitoylation of radicicol results in improved efficacy against tumor growth and angiogenesis in vivo. Cancer Sci., 98, 219-225. 

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