The Rat Subcutaneous Air Sac Model: A Quantitative Assay of Antiangiogenesis in Induced Vessels

Abstract

A new in vivo experimental model -the Subcutaneous Air Sac (SAS) model -has recently been presented to replace a previous in vivo rabbit cornea assay where neovascularisation was induced by chemical injury of the cornea or by implantation of tumour cells intracorneally, a methodology which is believed to cause severe pain to the animals. In the SAS model, an air sac is induced by injection of air subcutaneously on the back of the animal. After 10-14 days the air sac appears as an almost transparent avascular membrane in which induction of new vessels can be studied. We present recent developments of this technique: In the SAS-tumour technique, vascular endothelial growth factor-producing tumour cells are inoculated subcutaneously directly on the membrane, and the formation of new vessels is measured 8 days later. In the SAS-pellet technique, slow-release pellets containing angiogenic factors, basic fibroblast growth factor or vascular endothelial growth factor are implanted on the subcutaneous membrane by a simple operation. The formation of new vessels is measured 10 days later. The ability of the SAS-tumour-and SAS-pellet techniques to detect an antiangiogenic effect of a systemically administered compound was investigated using the fumagillin analogue TNP-470 (o-chloro-acetylcarbamoyl)-fumagillol) as a positive control given subcutaneously for 7 and 9 days, respectively. At a dose of 10 mg TNP-470/kg/day the angiogenesis was reduced by approximately 70% in the SAS-tumour technique and by 40-60% in the SASpellet technique. The animals were unaffected by the SAS methodology. The SAS-tumour and SAS-pellet models are considered complementary and make use of simple and almost similar techniques which facilitate the evaluation.

Quantitation of angiogenesis and antiangiogenesis in vivo, ex vivo and in vitro – an overview

“…The air sack is induced by injection of air subcutaneously into the back skin fold. For investigation of antiangiogenic substances, angiogenesis is first stimulated by surgical implantation of cellulose sponges, causing vasoproliferation, or by a tumour cell coated membrane (Lichtenberg et al, 1999;Basaki et al, 2001;Semba et al 2004;Yamamoto et al, 2009). The evaluation and quantitation of angiogenesis is performed by measurement of radiation of intravenously injected isotope-labelled antibodies.…”

Brain Tumor–Induced Angiogenesis: Approaches and Bioassays

“…The rat subcutaneous air sac (SAS-) model was promoted by Lichtenberger et al [92,93] as a straightforward method to study anti-angiogenesis in vivo. A sac is produced by introducing air dorsally to anesthetized rats via subcutaneous injection.…”

A Mouse Model for the Study of Factors Affecting Angiogenesis

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Experimental evidence has accumulated over the years to show that a variety of strategies that limit neovascularisation also slows down or inhibits tumour growth, suggesting that blocking tumour-induced angiogenesis is a valid, novel approach to tumour therapy (Folkmann 1997).The rat Subcutaneous Air Sac (SAS) model (Lichtenberg et al 1997(Lichtenberg et al & 1999 was recently described as a new in vivo model designed to replace a currently used eye model where neovascularisation is induced by chemical injury to the cornea of the rabbit or by implantation of tumour cells intracorneally (Gimbrone et al 1974). In the SAS model the membrane of the subcutaneous air sac simulates the cornea as a macroscopically avascular substrate in which the new vessels can develop.

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“…The rat Subcutaneous Air Sac (SAS) model (Lichtenberg et al 1997 & 1999) was recently described as a new in vivo model designed to replace a currently used eye model where neovascularisation is induced by chemical injury to the cornea of the rabbit or by implantation of tumour cells intracorneally (Gimbrone et al 1974). In the SAS model the membrane of the subcutaneous air sac simulates the cornea as a macroscopically avascular substrate in which the new vessels can develop.…”

“…The angiogenic response was quantitated as previously described (Lichtenberg et al 1997 & 1999). Briefly, 20 min.…”