Implications of the Wilms' Tumor Suppressor Wt1 in Cardiomyocyte Differentiation.

The Wilms' tumor suppressor Wt1 is involved in multiple developmental processes and adult tissue homeostasis. The first phenotypes recognized in Wt1 knockout mice were developmental cardiac and kidney defects. Wt1 expression in the heart has been described in epicardial, endothelial, smooth muscle cells, and fibroblasts. Expression of Wt1 in cardiomyocytes has been suggested but remained a controversial issue, as well as the role of Wt1 in cardiomyocyte development and regeneration after injury. We determined cardiac Wt1 expression during embryonic development, in the adult, and after cardiac injury by quantitative RT-PCR and immunohistochemistry. As in vitro model, phenotypic cardiomyocyte differentiation, i.e., the appearance of rhythmically beating clones from mouse embryonic stem cells (mESCs) and associated changes in gene expression were analyzed. We detected Wt1 in cardiomyocytes from embryonic day (E10.5), the first time point investigated, until adult age. Cardiac Wt1 mRNA levels decreased during embryonic development. In the adult, Wt1 was reactivated in cardiomyocytes 48 h and 3 weeks following myocardial infarction. Wt1 mRNA levels were increased in differentiating mESCs. Overexpression of Wt1(-KTS) and Wt1(+KTS) isoforms in ES cells reduced the fraction of phenotypically cardiomyocyte differentiated clones, which was preceded by a temporary increase in c-kit expression in Wt1(-KTS) transfected ES cell clones and induction of some cardiomyocyte markers. Taken together, Wt1 shows a dynamic expression pattern during cardiomyocyte differentiation and overexpression in ES cells reduces their phenotypical cardiomyocyte differentiation.

A CD34+ Cell Enrichment Protocol of Hematopoietic Stem Cells in a Well-Established Quality Management System.

Allogeneic stem cell transplantation applications have improved tremendously over the past quarter of a century. The use of new immunosuppressive protocols and elimination of T cells by CD34+ cell enrichment or T cell depletion on apheresis products increases the chance of using partially matched or haploidentical grafts. This is without increasing the risk of graft-versus-host disease, which is observed as a major complication of hematopoietic stem cell transplantation. The aim of this protocol is to evaluate the results obtained from 6 different process cycles performed on 6 different days. We used the CliniMACS Plus system located in our Cell and Tissue Manufacturing Center Quality Control Unit which is already calibrated as a class D room and includes a class A microbiological safety cabinet inside. The average purity of the end products was 95.66%, excluding only one end product which was 70%; this was higher than the values in current studies in the field. Superior to the reported studies, the CD3 quantity in each end product was below the dedicated thresholds. BactecTM FX40 blood culture system test results were detected as negative for each end product. Endotoxin testing suggested the absence of endotoxin within the products. The consistent outcomes obtained from these 6 different process cycles confirmed that the CliniMACS® Plus process cycles performed in accordance with our well-defined quality management system procedure is sufficient for the routine application of high-quality and safe CD34+ enrichment processes within our clean room area.

Activation of histone deacetylase-6 induces contractile dysfunction through derailment of α-tubulin proteostasis in experimental and human atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is characterized by structural remodeling, contractile dysfunction, and AF progression. Histone deacetylases (HDACs) influence acetylation of both histones and cytosolic proteins, thereby mediating epigenetic regulation and influencing cell proteostasis. Because the exact function of HDACs in AF is unknown, we investigated their role in experimental and clinical AF models. METHODS AND RESULTS: Tachypacing of HL-1 atrial cardiomyocytes and Drosophila pupae hearts significantly impaired contractile function (amplitude of Ca(2+) transients and heart wall contractions). This dysfunction was prevented by inhibition of HDAC6 (tubacin) and sirtuins (nicotinamide). Tachypacing induced specific activation of HDAC6, resulting in α-tubulin deacetylation, depolymerization, and degradation by calpain. Tachypacing-induced contractile dysfunction was completely rescued by dominant-negative HDAC6 mutants with loss of deacetylase activity in the second catalytic domain, which bears α-tubulin deacetylase activity. Furthermore, in vivo treatment with the HDAC6 inhibitor tubastatin A protected atrial tachypaced dogs from electric remodeling (action potential duration shortening, L-type Ca(2+) current reduction, AF promotion) and cellular Ca(2+)-handling/contractile dysfunction (loss of Ca(2+) transient amplitude, sarcomere contractility). Finally, atrial tissue from patients with AF also showed a significant increase in HDAC6 activity and reduction in the expression of both acetylated and total α-tubulin. CONCLUSIONS: AF induces remodeling and loss of contractile function, at least in part through HDAC6 activation and subsequent derailment of α-tubulin proteostasis and disruption of the cardiomyocyte microtubule structure. In vivo inhibition of HDAC6 protects against AF-related atrial remodeling, disclosing the potential of HDAC6 as a therapeutic target in clinical AF.

Molecular Signatures of Human Chronic Atrial Fibrillation in Primary Mitral Regurgitation.

OBJECTIVES: Transcriptomics of atrial fibrillation (AFib) in the setting of chronic primary mitral regurgitation (MR) remains to be characterized. We aimed to compare the gene expression profiles of patients with degenerative MR in AFib and sinus rhythm (SR) for a clearer picture of AFib pathophysiology. METHODS: After transcriptomic analysis and bioinformatics (n = 59), differentially expressed genes were defined using 1.5-fold change as the threshold. Additionally, independent datasets from GEO were included as meta-analyses. RESULTS: QRT-PCR analysis confirmed that AFib persistence was associated with increased expression molecular changes underlying a transition to heart failure (NPPB, P = 0.002; ANGPTL2, P = 0.002; IGFBP2, P = 0.010), structural remodeling including changes in the extracellular matrix and cellular stress response (COLQ, P = 0.003; COMP, P = 0.028; DHRS9, P = 0.038; CHGB, P = 0.038), and cellular stress response (DNAJA4, P = 0.038). Furthermore, AFib persistence was associated with decreased expression of the targets of structural remodeling (BMP7, P = 0.021) and electrical remodeling (CACNB2, P = 0.035; MCOLN3, P = 0.035) in both left and right atrial samples. The transmission electron microscopic analysis confirmed ultrastructural atrial remodeling and autophagy in human AFib atrial samples. CONCLUSIONS: Atrial cardiomyocyte remodeling in persistent AFib is closely linked to alterations in gene expression profiles compared to SR in patients with primary MR. Study findings may lead to novel therapeutic targets. This trial is registered with ClinicalTrials.gov identifier: NCT00970034.

Biotechnology and stem cell research: a glance into the future.

The present review addresses the issues related to innovative contributions in biotechnology and their potential role in stem cell research at present and in the future. We can expect that future developments and applications in biotechnological sciences and industry will effect the direction of emerging cellular therapies. The use of these advances may offer a unique opportunity to investigate the mechanisms related to the journey from embryonic cells or bone-marrow derived stem/progenitor cells to cardiomyocytes or endothelial cells and the molecular regulators of cell differentiation.

Failing heart; remodel, replace or repair?

In the era of proton-antiproton collisions, stem cell field has emerged as the newly recognized protons of regenerative medicine. Great interest and enthusiasm were depending on their behavioral difference such as self-renewal, clonogenicity and differentiation into functional progeny that may become vehicles for regenerative medicine. Although progress has evolved dramatically strategies using stem-cell-driven cardiac regeneration involve extremely complex and dynamic molecular mechanisms. Cell death in transplanted heart continues to be a significant issue. Every step from stem cell homing, and migration to retention, engraftment, survival and differentiation in cardiac cytotherapy deserves intense research for optimum results. Furthermore, regeneration of contractile tissue remains controversial for human studies and careful interpretation is warranted for modest benefit in clinical trials. Currently, the only realistic approach to replace the damaged cardiomyocytes is cardiac transplantation for patients with end-stage heart failure. Ultimately, the giant footsteps in cell-based cardiac repair can only be achieved by an enthusiastic but also skeptical teams adhering to good manufacturing practices. Better understanding of cell-fate decisions and functional properties in cardiac cytotherapy may change the erosion of initial enthusiasm and may open new prospects for cardiovascular medicine.