Stefan Rupp

Transdifferentiation of Blood-Derived Human Adult Endothelial Progenitor Cells Into Functionally Active Cardiomyocytes

Background—Further to promoting angiogenesis, cell therapy may be an approach for cardiac regeneration. Recent studies suggest that progenitor cells can transdifferentiate into other lineages. However, the transdifferentiation potential of endothelial progenitor cells (EPCs) is unknown. Methods and Results—EPCs were obtained from peripheral blood mononuclear cells of healthy adults or coronary artery disease (CAD) patients by cultivating with endothelial cell medium and growth factors. After 3 days, >95% of adherent cells were functionally and phenotypically EPCs. Diacetylated LDL–labeled EPCs were then cocultivated with rat cardiomyocytes for 6 days, resulting in significant increases of EPC cell length and size to a cardiomyocyte-like morphology. Biochemically, 9.94±1.39% and 5.04±1.09% of EPCs from healthy adults (n=15) or CAD patients (n=14, P <0.01 versus healthy adults), respectively, expressed &agr;-sarcomeric actinin as measured by flow cytometry. Immunocytochemistry showed that human EPCs expressed &agr;-sarcomeric actinin, cardiac troponin I (both with partial sarcomeric organization), atrial natriuretic peptide, and myocyte enhancer factor 2. Fluo 4 imaging demonstrated calcium transients synchronized with adjacent rat cardiomyocytes in transdifferentiated human EPCs. Single-cell microinjection of Lucifer yellow and calcein-AM labeling of cardiomyocytes demonstrated gap junctional communication between 51±7% of EPCs (16 hours after labeling, n=4) and cardiomyocytes. EPC transdifferentiation into cardiomyocytes was not observed with conditioned medium but in coculture with paraformaldehyde-fixed cardiomyocytes. Conclusions—EPCs from healthy volunteers and CAD patients can transdifferentiate in vitro into functionally active cardiomyocytes when cocultivated with rat cardiomyocytes. Cell-to-cell contact but not cellular fusion mediates EPC transdifferentiation. The therapeutic use of autologous EPCs may aid cardiomyocyte regeneration in patients with ischemic heart disease.

Statin therapy in patients with coronary artery disease improves the impaired endothelial progenitor cell differentiation into cardiomyogenic cells

Abstract.Human endothelial progenitor cells (EPCs) can differentiate into cardiomyogenic cells in vitro. We tested the effects of statin therapy on the differentiation rate of EPCs from patients with coronary artery disease (CAD), who may benefit from autologous cell therapy.EPCs from 3 age-matched groups were tested: No CAD (n = 13), CAD patients with (n = 10) or without (n = 16) statin therapy. From 4 CAD patients, EPCs were tested before and after 4 weeks of therapy with 20 mg atorvastatin. After 6 days of co-culture with rat neonatal cardiomyocytes, EPC differentiation was quantified by immunostaining for α-sarcomeric actinin flow cytometry analysis. After 6 days of co-culture, the percentage of -sarcomeric actinin–positive EPCs was significantly (p = 0.014) higher in EPCs from adults without CAD (8.07% ± 1.48% of EPCs) compared to EPCs from CAD patients without statin (3.56% ± 0.72%). Importantly, patients with statin therapy revealed significantly higher numbers of α-sarcomeric actinin-positive EPCs (6.36% ± 0.69%, p = 0.01) compared to CAD patients without statin. In addition, statin therapy resulted in a significant (p = 0.017) increase of EPC differentiation in all 4 CAD patients investigated before and 4 weeks after statin therapy. The survival of EPCs did not differ between the different groups suggesting that the regulation of EPC differentiation is not secondary to altered EPC survival. In vitro, EPC treatment with 0.1 µM atorvastatin did not affect EPC differentiation (116.15% ± 49.11% of control).EPCs from patients with CAD display impaired differentiation into cardiomyogenic cells. This defect can be improved by in vivo, statin therapy.

Severe familial left ventricular non-compaction cardiomyopathy due to a novel troponin T (TNNT2) mutation

AIMS Left ventricular non-compaction (LVNC) is caused by mutations in multiple genes. It is still unclear whether LVNC is the primary determinant of cardiomyopathy or rather a secondary phenomenon with intrinsic cardiomyocyte dysfunction being the actual cause of the disease. Here, we describe a family with LVNC due to a novel missense mutation, pE96K, in the cardiac troponin T gene (TNNT2). METHODS AND RESULTS The novel mutation was identified in the index patient and all affected relatives, but not in 430 healthy control individuals. Mutations in known LVNC-associated genes were excluded. To investigate the pathophysiological implications of the mutation, we generated transgenic mice expressing human wild-type cTNT (hcTNT) or a human troponin T harbouring the pE96K mutation (mut cTNT). Animals were characterized by echocardiography, histology, and gene expression analysis. Mut cTNT mice displayed an impaired left ventricular function and induction of marker genes of heart failure. Remarkably, left ventricular non-compaction was not observed. CONCLUSION Familial co-segregation and the cardiomyopathy phenotype of mut cTNT mice strongly support a causal relationship of the pE96K mutation and disease in our index patient. In addition, our data suggest that a non-compaction phenotype is not required for the development of cardiomyopathy in this specific TNNT2 mutation leading to LVNC.

Intracoronary administration of autologous bone marrow-derived progenitor cells in a critically ill two-yr-old child with dilated cardiomyopathy

Abstract:  DCM is the most common cardiomyopathy in childhood. Effectiveness of anticongestive therapy is limited in most cases and about one‐third of children diagnosed with DCM die or receive heart transplantation within the first year after diagnosis. Cardiac stem cell transplantation has become a promising therapy to treat heart failure in adult patients. Based on these promising results, the cardiac stem cell therapy might also represent a new therapeutic option particularly in young children. The present case documents for the first time intracoronary administration of autologous bone marrow‐derived progenitor cells in a critically ill two‐yr‐old child with severe heart failure caused by DCM. Because of progressive worsening of the clinical condition despite maximal anticongestive treatment, the decision to perform autologous stem cell therapy was made. Cardiac stem cell therapy proved to be technically feasible, was associated with improvement in cardiac function, and might represent an option before heart transplantation in children with severe heart failure.

A regenerative strategy for heart failure in hypoplastic left heart syndrome: intracoronary administration of autologous bone marrow-derived progenitor cells.

Novel surgical strategies have dramatically improved the initial outcome of newborns with hypoplastic left heart syndrome. However, the single systemic right ventricle remains a major challenge, with limited effectiveness of pharmacologic therapy. The present case documents that the intracoronary administration of autologous bone marrow-derived progenitor cells is technically feasible in a critically ill infant with hypoplastic left heart syndrome and severe heart failure after a hybrid comprehensive stage II procedure. Cell therapy might represent an option before heart transplantation in children with single ventricle physiology presenting with severe heart failure.

Differentiation of circulating endothelial progenitor cells to a cardiomyogenic phenotype depends on E-cadherin

Progenitor cells may contribute to cardiac regeneration. Here, we investigated the role of cadherins and integrins for differentiation of human adult circulating endothelial progenitor cells (EPCs) into cardiomyocytes (CM) in a co‐culture system. N‐ and E‐cadherin were expressed in EPCs and were localized at the interface between EPCs and CM. Incubation of a blocking antibody against E‐cadherin reduced the expression of CM marker protein in EPCs. Blocking antibodies against N‐ or P‐cadherin or the β1‐ and β2‐integrins were not effective. These data suggested that cell‐to‐cell communication mediated by E‐cadherin contributes to the acquirement of a cardiomyogenic phenotype of human endothelial progenitor cells.

Pulmonary artery banding in infants and young children with left ventricular dilated cardiomyopathy: a novel therapeutic strategy before heart transplantation.

BACKGROUND Dilated cardiomyopathy (DCM) in childhood has a considerable morbidity and mortality and high incidence of heart transplantation. Pulmonary artery banding (PAB) has been proposed in patients with corrected transposition of the great arteries to retrain the sub-pulmonic left ventricle (LV) and to improve a failing sub-aortic right ventricle. We evaluated the short-term and medium-term effects of PAB in young patients with LVDCM. METHODS A retrospective single-center observational study was performed to evaluate the possible benefits of a dilatable surgical PAB in infants and young children with LVDCM. RESULTS Reported are 12 patients (10 infants, 2 toddlers) with LVDCM referred for heart transplant who received a surgical PAB. There were no hospital deaths. Clinical functional status improved in all patients. The pressure gradient across the PAB increased within 20 days from 28 ± 7 to 43 ± 15 mm Hg. The LV ejection fraction increased from 14.5% ± 5% pre-PAB to 27% ± 13% at hospital discharge and to 47% ± 10% at 3 to 6 months. The LV end-diastolic diameter (z-score) decreased (p > 0.001) from 46 ± 6.1 (+7.0 ± 1.3) to 35 ± 15 mm (+3.0 ± 1.3) after 3 to 6 months and to 34 ± 15 mm (+1.3 ± 1.14) after a median age of 2 years (maximum 6.6 years), respectively. Plasma B-type natriuretic peptide levels decreased from 3431 ± 2610 to 288 ± 321 pg/ml at discharge and to 102 ± 96 pg/ml 22 months later. Eight children were subsequently de-banded by transcatheter technique and 6 of them are currently at Ross Heart Failure Classification for Children class I. Two patients, both with non-compaction DCM, deteriorated at 5 and 6 months after PAB debanding and finally died. CONCLUSION In young children with LVDCM and still-preserved right ventricular function, PAB led to an improvement of LV and mitral valve function by ventricular interaction.

Intracoronary bone marrow cell application for terminal heart failure in children.

INTRODUCTION In spite of tremendous progress in the medical and surgical treatment of children with congenital heart disease and dilated cardiomyopathy achieved during the past few decades, for some children a heart transplant remains the only option. Clinically relevant benefits of intracoronary injection of autologous stem cells on cardiac function and remodelling have been demonstrated in adult patients with acute myocardial infarction. Experience with autologous stem cell therapy in children with severe congenital or acquired pump failure is limited to a small number of case reports. METHOD AND RESULTS Between 2006 and 2010, nine severely ill children were treated with intracoronary infusion of autologous bone marrow-derived mononuclear cells as part of a compassionate therapy in our centre. No procedure-related unexpected adverse events occurred. There was one patient on extracorporeal membrane oxygenation who died of haemorrhage unrelated to the procedure; three patients proceeded to heart transplantation once a donor heart became available. The other five patients showed an improvement with respect to New York Heart Association classification (greater than or equal to 1), brain natriuretic peptide serum levels, and ejection fraction. CONCLUSION Similar to adults, intracoronary injection of autologous bone marrow cell is technically feasible and safe for children. On the basis of our data, we propose to perform a pilot study for children with congestive heart failure, to formally assess the efficacy of intracoronary autologous bone marrow cell therapy.

Sox2 Transduction enhances cardiovascular repair capacity of blood-derived mesoangioblasts

Rationale: Complementation of pluripotency genes may improve adult stem cell functions. Objectives: Here we show that clonally expandable, telomerase expressing progenitor cells can be isolated from peripheral blood of children. The surface marker profile of the clonally expanded cells is distinct from hematopoietic or mesenchymal stromal cells, and resembles that of embryonic multipotent mesoangioblasts. Cell numbers and proliferative capacity correlated with donor age. Isolated circulating mesoangioblasts (cMABs) express the pluripotency markers Klf4, c-Myc, as well as low levels of Oct3/4, but lack Sox2. Therefore, we tested whether overexpression of Sox2 enhances pluripotency and facilitates differentiation of cMABs in cardiovascular lineages. Methods and Results: Lentiviral transduction of Sox2 (Sox-MABs) enhanced the capacity of cMABs to differentiate into endothelial cells and cardiomyocytes in vitro. Furthermore, the number of smooth muscle actin positive cells was higher in Sox-MABs. In addition, pluripotency of Sox-MABs was shown by demonstrating the generation of endodermal and ectodermal progenies. To test whether Sox-MABs may exhibit improved therapeutic potential, we injected Sox-MABs into nude mice after acute myocardial infarction. Four weeks after cell therapy with Sox-MABs, cardiac function was significantly improved compared to mice treated with control cMABs. Furthermore, cell therapy with Sox-MABs resulted in increased number of differentiated cardiomyocytes, endothelial cells, and smooth muscle cells in vivo. Conclusions: The complementation of Sox2 in Oct3/4-, Klf4-, and c-Myc-expressing cMABs enhanced the differentiation into all 3 cardiovascular lineages and improved the functional recovery after acute myocardial infarction.

Characterization of long-term endogenous cardiac repair in children after heart transplantation

AIMS Circulating cells repopulate the heart at a very low rate in adult humans. The knowledge about time-dependent cardiac regeneration is very limited and the contribution of circulating cells to cardiomyocytes or vascular cells in children is unknown. This study investigates the endogenous repair capacity and the long-term incorporation of circulating cells in heart-transplanted children. METHODS AND RESULTS Cardiac and endothelial chimerism was detected in endomyocardial biopsies of nine children (age 1 months-14 years) with sex-mismatched heart transplantation by fluorescence in situ hybridization. Time from transplantation to biopsy ranged from 1 month up to 10 years. The extent of repopulating cardiomyocytes was 2.39 +/- 1.54% (range: 0-4.2%) and correlated significantly with the time from transplantation to biopsy sampling (r(2) = 0.69, P = 0.006; n = 9). The calculated contribution of male cardiomyocytes in the female heart per year was 0.36 +/- 0.09%. Consistent with the previous reports, the incorporation of vascular cells was higher compared with cardiomyocytes (14.4 +/- 4.17%), but did not correlate in a time-dependent manner. CONCLUSION Circulating cells contribute to cardiomyocytes and endothelial cells in children after heart transplantation. The incidence of repopulating cardiomyocytes continuously increases in a time-dependent manner ( approximately 4% Y-chromosome(+) cardiomyocytes/10 years) and resembles the cardiac regeneration activity observed in adults.