Abstract
INTRODUCTION: Angiotensin (Ang)-(1-7) is a recently identified vasoprotective heptapeptide, and it appears to activate the reparative functions of bone marrow-derived stem/progenitor cells (BMPCs). AIM: This study evaluated the effect of Ang-(1-7) in the angiogenic function of cavernosum in type 1 diabetes (T1D) and delineated the role of BMPCs in this protective function. METHODS: T1D was induced by streptozotocin in mice, and mice with 20-24 weeks of diabetes were used for the study. Ang-(1-7) was administered subcutaneously by using osmotic pumps. Cavernosa, and BMPCs from peripheral blood and bone marrow were evaluated in different assay systems. MAIN OUTCOME MEASURES: Angiogenic function was determined by endothelial tube formation in matrigel assay. Circulating BMPCs were enumerated by flow cytometry and proliferation was determined by BrdU incorporation. Cell-free supernatant of BMPCs were collected and tested for paracrine angiogenic effect. Expression of angiogenic factors in BMPCs and cavernosa were determined by real-time polymerase chain reaction. RESULTS: Ang-(1-7) (100 nM) stimulated angiogenesis in mouse cavernosum that was partially inhibited by Mas1 receptor antagonist, A779 (10 μM) (P < 0.05). In cavernosa of T1D, the angiogenic responses to Ang-(1-7) (P < 0.005) and VEGF (100 nM) (P < 0.03) were diminished. Ang-(1-7) treatment for 4 weeks reversed T1D-induced decrease in the VEGF-mediated angiogenesis. Ang-(1-7) treatment increased the circulating number of BMPCs and proliferation that were decreased in T1D (P < 0.02). Paracrine angiogenic function of BMPCs was reduced in diabetic BMPCs, which was reversed by Ang-(1-7). In diabetic BMPCs, SDF and angiopoietin-1 were upregulated by Ang-(1-7), and in cavernosum, VEGFR1, Tie-2, and SDF were upregulated and angiopoietin-2 was down-regulated. CONCLUSIONS: Ang-(1-7) stimulates angiogenic function of cavernosum in diabetes via its stimulating effects on both cavernosal microvasculature and BMPCs.