Migration towards SDF-1 selects angiogenin-expressing bone marrow monocytes endowed with cardiac reparative activity in patients with previous myocardial infarction

Raimondo Ascione, Jonathan Rowlinson, Elisa Avolio, Rajesh Katare, Marco Meloni, Helen L Spencer, Giuseppe Mangialardi, Caroline Norris, Nicolle Kränkel, Gaia Spinetti, Costanza Emanueli, Paolo Madeddu

Chemokine-directed migration is crucial for homing of regenerative cells to the infarcted heart and correlates with outcomes of cell therapy trials. Hence, transplantation of chemokine-responsive bone marrow (BM) cells may be ideal for treatment of myocardial ischemia. To verify the therapeutic activity of BM mononuclear cells (BM-MNCs) selected by in vitro migration towards the chemokine stromal cell-derived factor-1 (SDF-1) in a mouse model of myocardial infarction (MI). We used for this purpose BM-MNCs from patients with previous large MI recruited in the TransACT-1&2 cell therapy trials. Un-fractioned BM-MNCs, SDF-1 responsive, and SDF-1 non-responsive BM-MNCs isolated by patients recruited in the TransACT-1&2 cell therapy trials were tested in Matrigel assay to evaluate angiogenic potential. Secretome and antigenic profile were characterized by flow cytometry. Angiogenin expression was measured by RT-PCR. Cells groups were also intra-myocardially injected in an in vivo model of MI (8 weeks-old immune deficient CD1-FOXN1(nu/nu) mice). Echocardiography and heamodynamic measurements were performed before and at 14 days post-MI. Arterioles and capillaries density, infiltration of inflammatory cells, interstitial fibrosis, and cardiomyocyte proliferation and apoptosis were assessed by immunohistochemistry. In vitro migration enriched for monocytes, while CD34(+) and CD133(+) cells and T-lymphocytes remained mainly confined in the non-migrated fraction. Un-fractioned total BM-MNCs promoted angiogenesis on Matrigel more efficiently than migrated or non-migrated cells. In mice with induced MI, intra-myocardial injection of un-fractionated or migrated BM-MNCs was more effective in preserving cardiac contractility and pressure indexes than vehicle or non-migrated BM-MNCs. Moreover, un-fractioned BM-MNCs enhanced neovascularization, whereas the migrated fraction was unique in reducing the infarct size and interstitial fibrosis. In vitro studies on isolated cardiomyocytes suggest participation of angiogenin, a secreted ribonuclease that inhibits protein translation under stress conditions, in promotion of cardiomyocyte survival by migrated BM-MNCs. Transplantation of BM cells helps post-MI healing through distinct actions on vascular cells and cardiomyocytes. In addition, the SDF-1-responsive fraction is enriched with angiogenin-expressing monocytes, which may improve cardiac recovery through activation of cardiomyocyte response to stress. Identification of factors linking migratory and therapeutic outcomes could help refining regenerative approaches.