A new heart: somatic stem cells and myocardial regeneration

Sirtuins in hematological aging and malignancy

Aging of the hematological system causes anemia, reduced immunity, and increased incidence of hematological malignancies. Hematopoietic stem cells (HSCs) play a crucial role in this process as their functions decline during aging. Sirtuins are a family of protein lysine modifying enzymes that have diverse roles in regulating metabolism, genome stability, cell proliferation, and survival, and have been implicated in mammalian aging and longevity. Here we provide an updated overview of sirtuins in aging research; particularly, how increased activity of SIRT1, SIRT3, or SIRT6 improves several aging parameters, and may possibly increase lifespan in mice. We review the literature on how sirtuins may play a role in HSC aging and hematological malignancies, and how key signaling pathways of HSCs may be affected by sirtuins. Among them, SIRT1 plays a critical role in chronic myelogenous leukemia, an age-dependent malignancy, and inhibition of SIRT1 sensitizes leukemic stem cells to tyrosine kinase inhibitor treatment and blocks acquisition of resistant oncogene mutations. In-depth understanding of sirtuins in HSC aging and malignancy may help design novel strategies to deter hematological aging and improve treatment of hematological malignancies.

miRNAs regulate stem cell self-renewal and differentiation

Stem cells undergo symmetric and asymmetric divisions to generate differentiated cells and more stem cells. The balance between self-renewal and differentiation of stem cells is controlled by transcription factors, epigenetic regulatory networks, and microRNAs (miRNAs). Herein the miRNA involvement in the regulation of stem cell self-renewal and differentiation is summarized. miRNA contribution to malignancy through regulating cancer stem cells is described. In addition, the reciprocal associations between miRNAs and epigenetic modifications in control of stem cell fate are discussed.

Effects of intracoronary delivery of allogenic bone marrow-derived stem cells expressing heme oxygenase-1 on myocardial reperfusion injury

Heme oxygenase-1 (HO-1) decreases apoptosis, inflammation and oxidative stress. The aim of the study was to investigate the effects of intracoronary infusion of allogenic bone marrow cells (BMC) overexpressing HO-1 in the porcine model of myocardial infarction (MI). MI was produced by balloon occlusion of a coronary artery. BMC were transduced with adenoviruses encoding for HO-1 (HO-1 BMC) or GFP (GFP-BMC) genes. Prior to reperfusion animals received HO-1 BMC, control BMC (unmodified or GFP-BMC) or placebo. Left ventricular (LV) ejection fraction (EF), shortening fraction (SF), end-systolic and end-diastolic diameters (EDD, ESD) were assessed by echocardiography before, 30 minutes (min) and 14 days after reperfusion. BMC significantly improved LVEF and SF early (30 min) after reperfusion as well as after 14 days. Early after reperfusion HO-1 BMC were significantly more effective than control BMC, but after 14 days, there were no differences. There were no effect of cells on LV remodelling and diastolic function. Both HO-1 BMC and control BMC significantly reduced the infarct size vs. placebo (17.2 ± 2.7 and 18.8 ± 2.5, respectively, vs. 27.5 ± 5.1, p= 0.02) in histomorphometry. HO-1-positive donor BMC were detected in the infarct border area in pigs receiving HO-1-cells. No significant differences in expression of inflammatory genes (SDF-1, TNF-α, IL-6, miR21, miR29a and miR133a) in the myocardium were found. In conclusion, intracoronary delivery of allogeneic BMC immediately prior to reperfusion improved the LVEF and reduced the infarct size. HO-1 BMC were not superior to control cells after 14 days, however, produced faster recovery of LVEF. Transplanted cells survived in the peri-infarct zone.