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Piero Anversa

Publications and source records attributed to Piero Anversa.

At least 55 records · Page 3Linked to original sources
PubMed2003

Adult cardiac stem cells are multipotent and support myocardial regeneration.

The notion of the adult heart as terminally differentiated organ without self-renewal potential has been undermined by the existence of a subpopulation of replicating myocytes in normal and pathological states. The origin and significance of these cells has remained obscure for lack of a proper biological context. We report the existence of Lin(-) c-kit(POS) cells with the properties of cardiac stem cells. They are self-renewing, clonogenic, and multipotent, giving rise to myocytes, smooth muscle, and endothelial cells. When injected into an ischemic heart, these cells or their clonal progeny reconstitute well-differentiated myocardium, formed by blood-carrying new vessels and myocytes with the characteristics of young cells, encompassing approximately 70% of the ventricle. Thus, the adult heart, like the brain, is mainly composed of terminally differentiated cells, but is not a terminally differentiated organ because it contains stem cells supporting its regeneration. The existence of these cells opens new opportunities for myocardial repair.

Animals↗
PubMed2003

Senescence and death of primitive cells and myocytes lead to premature cardiac aging and heart failure.

Chronological myocardial aging is viewed as the inevitable effect of time on the functional reserve of the heart. Cardiac failure in elderly patients is commonly interpreted as an idiopathic or secondary myopathy superimposed on the old heart independently from the aging process. Thus, aged diseased hearts were studied to determine whether cell regeneration was disproportionate to the accumulation of old dying cells, leading to cardiac decompensation. Endomyocardial biopsies from 19 old patients with a dilated myopathy were compared with specimens from 7 individuals of similar age and normal ventricular function. Ten patients with idiopathic dilated cardiomyopathy were also analyzed to detect differences with aged diseased hearts. Senescent cells were identified by the expression of the cell cycle inhibitor p16INK4a and cell death by hairpin 1 and 2. Replication of primitive cells and myocytes was assessed by MCM5 labeling, myocyte mitotic index, and telomerase function. Aged diseased hearts had moderate hypertrophy and dilation, accumulation of p16INK4a positive primitive cells and myocytes, and no structural damage. Cell death markedly increased and occurred only in cells expressing p16INK4a that had significant telomeric shortening. Cell multiplication, mitotic index and telomerase increased but did not compensate for cell death or prevented telomeric shortening. Idiopathic dilated cardiomyopathy had severe hypertrophy and dilation, tissue injury, and minimal level of p16INK4a labeling. In conclusion, telomere erosion, cellular senescence, and death characterize aged diseased hearts and the development of cardiac failure in humans.

Aged↗
PubMed2003

Intense myocyte formation from cardiac stem cells in human cardiac hypertrophy.

It is generally believed that increase in adult contractile cardiac mass can be accomplished only by hypertrophy of existing myocytes. Documentation of myocardial regeneration in acute stress has challenged this dogma and led to the proposition that myocyte renewal is fundamental to cardiac homeostasis. Here we report that in human aortic stenosis, increased cardiac mass results from a combination of myocyte hypertrophy and hyperplasia. Intense new myocyte formation results from the differentiation of stem-like cells committed to the myocyte lineage. These cells express stem cell markers and telomerase. Their number increased >13-fold in aortic stenosis. The finding of cell clusters with stem cells making the transition to cardiogenic and myocyte precursors, as well as very primitive myocytes that turn into terminally differentiated myocytes, provides a link between cardiac stem cells and myocyte differentiation. Growth and differentiation of these primitive cells was markedly enhanced in hypertrophy, consistent with activation of a restricted number of stem cells that, through symmetrical cell division, generate asynchronously differentiating progeny. These clusters strongly support the existence of cardiac stem cells that amplify and commit to the myocyte lineage in response to increased workload. Their presence is consistent with the notion that myocyte hyperplasia significantly contributes to cardiac hypertrophy and accounts for the subpopulation of cycling myocytes.

Cardiomegaly↗
PubMed2003

Adeno-associated virus mediated gene delivery into coronary microvessels of chronically instrumented dogs.

The objective of this study was to assess the potential of adeno-associated virus (AAV)-mediated gene delivery into coronary microvessels in vivo in a large animal. Ten mongrel dogs were chronically instrumented and allowed to recover for 10 days. Dogs were reanesthetized, and the aorta was constricted by a hydraulic occluder, whereby left ventricular (LV) pressure increased by 30% and left circumflex coronary artery blood flow by 50%. Recombinant AAV (serotype 2, CMV enhancer/chicken beta-actin promoter) encoding for green fluorescent protein (GFP) was injected as a bolus into the left atrium during aortic constriction at total titers of 1010 or 1012 infectious units. Dogs were followed for 2 (n = 4)or4wk(n = 6). Hemodynamics or body weight did not change. In LV tissue slices, a fluorescein-labeled antibody to GFP stained endothelial and smooth muscle cells but was absent in myocytes. To quantify transduction, slices were then stained with antibodies against alpha-smooth muscle actin or von Willebrand factor. Approximately 4% of arterioles and 2% of microvessels stained positive for anti-GFP independent from viral titer or duration. By regression analyses, the percent of vessels transfected was proportional to the increase in LV systolic pressure during occlusion. AAV is a potential vector for gene transfer into the coronary microcirculation in large animals, including perhaps humans.

Animals↗
PubMed2003

Recombinant human erythropoietin protects the myocardium from ischemia-reperfusion injury and promotes beneficial remodeling.

Erythropoietin (EPO), originally identified for its critical hormonal role in promoting erythrocyte survival and differentiation, is a member of the large and diverse cytokine superfamily. Recent studies have identified multiple paracrineautocrine functions of EPO that coordinate local responses to injury by maintaining vascular autoregulation and attenuating both primary (apoptotic) and secondary (inflammatory) causes of cell death. Experimental evidence also supports a role for EPO in repair and regeneration after brain and spinal cord injury, including the recruitment of stem cells into the region of damage. Tissue expression of the EPO receptor is widespread, especially during development, and includes the heart. However, it is currently unknown as to whether EPO plays a physiological function in adult myocardial tissue. We have assessed the potential protective role of EPO in vitro with adult rat cardiomyocytes, and in vivo in a rat model of myocardial infarction with reperfusion. The results show that EPO markedly prevents the apoptosis of cultured adult rat myocardiocytes subjected to 28 h of hypoxia (approximately 3% normal oxygen). Additional studies employing a rat model of coronary ischemia-reperfusion showed that the administration of recombinant human EPO (5,000 units/kg of body weight; i.p. daily for 7 days) reduces cardiomyocyte loss by approximately 50%, an extent sufficient to normalize hemodynamic function within 1 week after reperfusion. These observations not only suggest a potential therapeutic role for recombinant human EPO in the treatment of myocardial ischemia and infarction by preventing apoptosis and attenuating postinfarct deterioration in hemodynamic function, but also predict that EPO is likely a tissue-protective cytokine in other organs as well.

Acidosis↗
PubMed2003

Myocyte death, growth, and regeneration in cardiac hypertrophy and failure.

The accepted paradigm considers the adult mammalian heart as a postmitotic organ, which possesses a relatively constant number of myocytes from shortly after birth to adulthood and senescence. This notion is questioned by the demonstration that although most adult myocytes are terminally differentiated, there is a small and continuously renewed subpopulation of cycling myocytes produced by the differentiation of cardiac stem-like cells. Myocyte death and myocyte regeneration are introduced as major determinants of cardiac homeostasis and alterations of ventricular anatomy and function in physiological and pathological states. The possibility of reconstituting dead myocardium by stem-like cells is advanced and proposed as a major area of future research.

Animals↗
PubMed2003

Ablation of telomerase and telomere loss leads to cardiac dilatation and heart failure associated with p53 upregulation.

Cardiac failure is a frequent cause of death in the aging human population. Telomere attrition occurs with age, and is proposed to be causal for the aging process. To determine whether telomere shortening leads to a cardiac phenotype, we studied heart function in the telomerase knockout mouse, Terc-/-. We studied Terc-/- mice at the second, G2, and fifth, G5, generation. Telomere shortening in G2 and G5 Terc-/- mice was coupled with attenuation in cardiac myocyte proliferation, increased apoptosis and cardiac myocyte hypertrophy. On a single-cell basis, telomere shortening was coincidental with increased expression of p53, indicating the presence of dysfunctional telomeres in cardiac myocytes from G5 Terc-/- mice. The impairment in cell division, the enhanced cardiac myocyte death and cellular hypertrophy, are concomitant with ventricular dilation, thinning of the wall and cardiac dysfunction. Thus, inhibition of cardiac myocyte replication provoked by telomere shortening, results in de-compensated eccentric hypertrophy and heart failure in mice. Telomere shortening with age could also contribute to cardiac failure in humans, opening the possibility for new therapies.

Animals↗
PubMed2003

Bone marrow stem cells regenerate infarcted myocardium.

Heart disease is the leading cause of death in the United States for both men and women. Nearly 50% of all cardiovascular deaths result from coronary artery disease. Occlusion of the left coronary artery leads to ischemia, infarction, necrosis of the affected myocardial tissue followed by scar formation and loss of function. Although myocytes in the surviving myocardium undergo hypertrophy and cell division occurs in the border area of the dead tissue, myocardial infarcts do not regenerate and eventually result in the death of the individual. Numerous attempts have been made to repair damaged myocardium in animal models and in humans. Bone marrow stem cells (BMSC) retain the ability throughout adult life to self-renew and differentiate into cells of all blood lineages. These adult BMSC have recently been shown to have the capacity to differentiate into multiple specific cell types in tissues other than bone marrow. Our research is focused on the capacity of BMSC to form new cardiac myocytes and coronary vessels following an induced myocardial infarct in adult mice. In this paper we will review the data we have previously published from studies on the regenerative capacity of BMSC in acute ischemic myocardial injury. In one experiment donor BMSC were injected directly into the healthy myocardium adjacent to the injured area of the left ventricle. In the second experiment, mice were treated with cytokines to mobilize their BMSC into the circulation on the theory that the stem cells would traffic to the myocardial infarct. In both experimental protocols, the BMSC gave rise to new cardiac myocytes and coronary blood vessels. This BMSC-derived myocardial regeneration resulted in improved cardiac function and survival.

Animals↗
PubMed2002

bcl-2 overexpression promotes myocyte proliferation.

To determine the influence of Bcl-2 on the developmental biology of myocytes, we analyzed the population dynamics of this cell type in the heart of transgenic (TG) mice overexpressing Bcl-2 under the control of the alpha-myosin heavy chain promoter. TG mice and non-TG (wild type, WT) mice were studied at 24 days, 2 months, and 4 months after birth. Bcl-2 overexpression produced a significant increase in the percentage of cycling myocytes and their mitotic index. These effects were strictly connected to the expression of the transgene, as demonstrated in isolated myocytes. The formation of mitotic spindle and contractile ring was identified in replicating cells. These typical aspects of mitosis were complemented with the demonstration of karyokinesis and cytokinesis to provide structural evidence of cell division. Apoptosis was low at all ages and was not affected by Bcl-2. The higher cell replication rate in TG was conditioned by a decrease in the expression of the cell-cycle inhibitors, p21(WAF1) and p16(INK4a), and by an increase in Mdm2-p53 complexes. In comparison with WT, TG had 0.4 x 10(6), 0.74 x 10(6), and 1.2 x 10(6) more myocytes in the left ventricle at 24 days, 2 months, and 4 months, respectively. Binucleated myocytes were 12% and 25% larger in WT than in TG mice at 2 and 4 months of age. Taken together, these observations reveal a previously uncharacterized replication-enhancing function of Bcl-2 in myocytes in vivo in the absence of stressful conditions.

Animals↗
PubMed2002

Cardiac-specific IGF-1 expression attenuates dilated cardiomyopathy in tropomodulin-overexpressing transgenic mice.

To test the hypothesis that early interventional treatment with insulin-like growth factor-1 (IGF-1) alleviates subsequent development of dilated cardiomyopathy, cardiac-specific IGF-1 expression was introduced by selective cross-breeding into a transgenic mouse model of heart failure that displays phenotypic characteristics of severe dilation. Hemodynamic, structural, and cellular parameters of the heart were compared between nontransgenic, tropomodulin-overexpressing cardiomyopathic, and the hybrid tropomodulin/IGF-1-overexpressing mice. Beneficial effects of IGF-1 were apparent by multiple indices of cardiac structure and function, including normalization of heart mass, anatomy, hemodynamics, and apoptosis. IGF-1 expression also acted as a proliferative stimulus as evidenced by calculated increases in myocyte number as well as expression of Ki67, a nuclear marker of cellular replication. Cellular analyses revealed that IGF-1 inhibited characteristic cardiomyocyte elongation in dilated hearts and restored calcium dynamics comparable to that observed in normal cells. Collectively, these results provide novel information regarding the ability of IGF-1 to inhibit progression of cardiomyopathic disease in a defined model system and suggest that heart failure may benefit from early interventional IGF-1 treatment.

Animals↗
PubMed2002

Myocyte renewal and ventricular remodelling.

Remaining young at heart is a desirable but elusive goal. Unbeknown to us, however, myocyte regeneration may accomplish just that. Continuous cell renewal in the adult myocardium was thought to be impossible, but multipotent cardiac stem cells may be able to renew the myocardium and, under certain circumstances, can be coaxed to repair the broken heart after infarction.

Animals↗
PubMed2002

Chimerism of the transplanted heart.

BACKGROUND: Cases in which a male patient receives a heart from a female donor provide an unusual opportunity to test whether primitive cells translocate from the recipient to the graft and whether cells with the phenotypic characteristics of those of the recipient ultimately reside in the donor heart. The Y chromosome can be used to detect migrated undifferentiated cells expressing stem-cell antigens and to discriminate between primitive cells derived from the recipient and those derived from the donor. METHODS: We examined samples from the atria of the recipient and the atria and ventricles of the graft by fluorescence in situ hybridization to determine whether Y chromosomes were present in eight hearts from female donors implanted into male patients. Primitive cells bearing Y chromosomes that expressed c-kit, MDR1, and Sca-1 were also investigated. RESULTS: Myocytes, coronary arterioles, and capillaries that had a Y chromosome made up 7 to 10 percent of those in the donor hearts and were highly proliferative. As compared with the ventricles of control hearts, the ventricles of the transplanted hearts had markedly increased numbers of cells that were positive for c-kit, MDR1, or Sca-1. The number of primitive cells was higher in the atria of the hosts and the atria of the donor hearts than in the ventricles of the donor hearts, and 12 to 16 percent of these cells contained a Y chromosome. Undifferentiated cells were negative for markers of bone marrow origin. Progenitor cells expressing MEF2, GATA-4, and nestin (which identify the cells as myocytes) and Flk1 (which identifies the cells as endothelial cells) were identified. CONCLUSIONS: Our results show a high level of cardiac chimerism caused by the migration of primitive cells from the recipient to the grafted heart. Putative stem cells and progenitor cells were identified in control myocardium and in increased numbers in transplanted hearts.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

Myocyte growth and cardiac repair.

Introduced several decades ago, the dogma persists that ventricular myocytes are terminally differentiated cells and cardiac repair by myocyte regeneration is completely inhibited shortly after birth. On the basis that cardiac myocytes are unable to divide in the adult heart, myocyte growth under physiologic and pathologic conditions is believed to be restricted to cellular hypertrophy. Evidence is presented to indicate that this old paradigm has to be changed to include myocyte replication as a significant component of the cellular processes of ventricular remodeling. Importantly, myocyte death, apoptotic and necrotic in nature, has to be regarded as an additional critical variable of the multifactorial events implicated in the alterations of cardiac anatomy and myocardial structure of the decompensated heart. Methodologies are currently available to recognize and measure quantitatively the contribution of myocyte size, number and death to the adaptation of the overloaded heart and its progression to cardiac failure.

Animals↗
PubMed2002

Myocyte proliferation and ventricular remodeling.

Improvement in the methodological approach to the analysis of the myocardium has provided clear evidence of cardiac myocyte proliferation, questioning the general belief that the growth of the adult heart under physiological and pathological conditions can occur only by cellular hypertrophy. Myocyte regeneration contributes via myocyte death to the physiological turnover of myocytes and via myocyte hypertrophy to cardiac remodeling. Several questions, however, remain to be answered. Among them, it is still unknown whether myocyte multiplication exerts a positive and/or negative effect on ventricular anatomy and cardiac function. The addition of newly generated myocytes leads to cavitary dilation with relative thinning of the wall. Conversely, myocyte proliferation, characterized by the parallel addition of cells, can be expected to increase wall thickness, decrease chamber size, and ameliorate cardiac performance.

Cardiomegaly↗