Effects of adrenomedullin on acute ischaemia-induced collateral development and mobilization of bone-marrow-derived cells

Abstract

Adrenomedullin exerts not only vasodilatory effects, but also angiogenic effects. In the present study, we investigated the effects of adrenomedullin on collateral formation and circulating bone-marrow-derived cells after acute tissue ischaemia. Bone marrow of 8-10-week-old female C57BL/6J mice was replaced with that from GFP (green fluorescent protein) transgenic mice (GFP mice). At 8 weeks after transplantation, hindlimb ischaemia was induced by resecting the right femoral artery and a plasmid expressing human adrenomedullin (50 mug) was injected into the ischaemic muscle, followed by in vivo electroporation on a weekly basis. Overexpression of adrenomedullin significantly enhanced the blood flow recovery compared with controls (blood flow ratio, 1.0+/-0.2 compared with 0.6+/-0.3 respectively, at week 4; P<0.05) and increased capillary density in the ischaemic leg as determined by anti-CD31 immunostaining of the ischaemic muscle (567+/-40 compared with 338+/-65 capillaries/mm(2) respectively, at week 5; P<0.05). There were more GFP-positive cells in the thigh muscle of the mice injected with adrenomedullin than in that of the control mice (29.6+/-4.5 compared with 16.5+/-3.3 capillaries/mm(2) respectively, at week 5; P<0.05). We repeated the same experiments using LacZ-knock-in mice instead of GFP mice, and obtained similar results. These findings suggest that adrenomedullin may augment ischaemia-induced collateral formation with some effects on circulating bone-marrow-derived cells.

The HIF-1 response to simulated ischemia in mouse skeletal muscle cells neither enhances glycolysis nor prevents myotube cell death

“…In cardiac muscle cells, ADM increased after hypoxia due to HIF binding and attenuated myocardial damage after ischemia-reperfusion (17). Furthermore, ADM administration enhanced the recovery of blood flow after hindlimb ischemia-reperfusion accompanied by an increased number of bone marrow-derived endothelial cells (1). Increased VEGF expression resulting from higher HIF-1 activity in vivo correlates with vascularization and may be an important component in muscle regeneration (3,19,28,30,42).…”

“…In skeletal muscle, the RNA-binding protein Hu protein R has been identified to increase VEGF mRNA stability after exercise (40), which might play a comparable role during ischemia. Nevertheless, several in vivo studies demonstrated the upregulation of ADM, VEGF, and VEGF receptors after ischemia and reperfusion, which was followed by increased angiogenesis and myogenesis (1,3,11,28,42).…”

Lack of adrenomedullin affects growth and differentiation of adult neural stem/progenitor cells

“…AM has been also implicated in the growth and expansion of cord blood hematopoietic stem cells (De Angeli et al 2004), probably through a novel mechanism involving the activation of the Notch pathway (Yurugi-Kobayashi et al 2006). Furthermore, addition of AM to established protocols for stem cell therapy in animals seems greatly to enhance the outcome of the procedures (Nagaya et al 2003;Iwase et al 2005;Hanabusa et al 2005;Abe et al 2006;Jo et al 2007). At the cellular level, both AM and PAMP are thought to be involved in growth modulation (Zudaire et al 2003), apoptosis reduction , induction of angiogenesis (Martinez et al 2004), and the regulation of cell migration (Zudaire et al 2006).…”

Nonclassic Endogenous Novel Regulators of Angiogenesis

“…AM has been reported to exert its angiogenic activity via AM 1 -Rs and AM 2 -Rs, which activate mitogen-activated protein kinase (MAPK) and Akt cascades and focal adhesion kinase (Kim et al, 2003b;Miyashita et al, 2003;Fernandez-Sauze et al, 2004), as well as play an antiinflammatory role in controlling VEGF-induced adhesion molecule gene expression and adhesiveness toward leukocytes in ECs (Kim et al, 2003a). AM augmented vascular collateral development in response to acute ischemia (Abe et al, 2003(Abe et al, , 2006Iwase et al, 2005) and enhanced capillary-like tube formation by HUVECs cultured on Matrigel and blood vessel formation in the CAM assay, the effect being counteracted by AM(22-52) (Ribatti et al, 2003a). AM gene transfer was found to induce therapeutic angiogenesis in a rabbit model of chronic hind limb ischemia (Tokunaga et al, 2004).…”