Angiotensin-II-induced angiogenesis in sponge implants in mice

Stimulators of angiogenesis hold potential in promoting the development of collateral circulation in ischaemic tissue and accelerating would healing, but promote pathological vasoformation in angiogenesis-dependent diseases (solid tumours, atherosclerosis). The renin-angiotensin system is implicated in both beneficial angiogenesis and pathological vascular growth. We investigated the angiogenic activity of angiotensin II (AII) in a sponge implant model in mice; this peptide enhanced angiogenesis, as well as glycosaminoglycan (GAG, chondroitin sulfate proteoglycan) and protein synthesis in sponge matrix in mice in a dose-dependent fashion. Extensive angiogenesis was achieved with AII (1 microgram), which gave no significant increase in wet weight and protein and only a small effect on GAG. In the implants treated with AII (2 micrograms) no further increase in angiogenesis was observed, whereas a marked effect was shown in wet weight (326 +/- 15 vs. 424 +/- 27 mg), total protein (18 +/- 1 vs. 25 +/- 1 micrograms/ww) and GAG (98 +/- 10 vs. 160 +/- 13 ng/ww). The local blood flow has been determined by measuring the washout rate of 133Xe injected into the implants, correlated with histological evidence of vessel growth. This model of angiogenesis has allowed sequential studies of fibrovascular tissue infiltration simultaneously with histological and biochemical parameters of angiogenesis.