Wnt5a Increases Cardiac Gene Expressions of Cultured Human Circulating Progenitor Cells via a PKC Delta Activation

Background: Wnt signaling controls the balance between stem cell proliferation and differentiation and body patterning throughout development. Previous data demonstrated that non-canonical Wnts (Wnt5a, Wnt11) increased cardiac gene expression of circulating endothelial progenitor cells (EPC) and bone marrow-derived stem cells cultured in vitro. Since previous studies suggested a contribution of the protein kinase C (PKC) family to the Wnt5a-induced signalling, we investigated which PKC isoforms are activated by non-canonical Wnt5a in human EPC. Methodology/Principal Findings: Immunoblot experiments demonstrated that Wnt5a selectively activated the novel PKC isoform, PKC delta, as evidenced by phosphorylation and translocation. In contrast, the classical Ca2+-dependent PKC isoforms, PKC alpha and beta2, and one of the other novel PKC isoforms, PKC epsilon, were not activated by Wnt5a. The PKC delta inhibitor rottlerin significantly blocked co-culture-induced cardiac differentiation in vitro, whereas inhibitors directed against the classical Ca2+-dependent PKC isoforms or a PKC epsilon-inhibitory peptide did not block cardiac differentiation. In accordance, EPC derived from PKC delta heterozygous mice exhibited a significant reduction of Wnt5a-induced cardiac gene expression compared to wild type mice derived EPC. Conclusions/Significance: These data indicate that Wnt5a enhances cardiac gene expressions of EPC via an activation of PKC delta

Isolation of Mesenchymal Stem Cells from Bone Marrow Aspirate

Isolation of mesenchymal stem cells from bone marrow aspirat

Stem Cell Therapy: Pieces of the Puzzle

Acute ischemic injury and chronic cardiomyopathies can cause irreversible loss of cardiac tissue leading to heart failure. Cellular therapy offers a new paradigm for treatment of heart disease. Stem cell therapies in animal models show that transplantation of various cell preparations improves ventricular function after injury. The first clinical trials in patients produced some encouraging results, despite limited evidence for the long-term survival of transplanted cells. Ongoing research at the bench and the bedside aims to compare sources of donor cells, test methods of cell delivery, improve myocardial homing, bolster cell survival, and promote cardiomyocyte differentiation. This article reviews progress toward these goals

Mesenchymal stem cells are recruited to striated muscle by NFAT/IL-4-mediated cell fusion

Mesenchymal stem cells (MSCs) or mesenchymal adult stem cells (MASCs) that are present in the stroma of several organs have been proposed to contribute to the regeneration of different tissues including liver, blood, heart, and skeletal muscle. Yet, it remains unclear whether MSCs can be programmed to differentiate cell-autonomously into fully functional cells or whether they are recruited by surrounding cells via fusion and thereby acquire specialized cellular functions. Here, we demonstrate that Wnt signaling molecules activate the expression of distinct sets of genes characteristic for cardiac and skeletal muscle cells in MASCs. However, such cells lack morphological criteria characteristic for functional muscle cells and do not show contractile activity. In contrast, MASCs fuse efficiently with native myotubes in an IL-4-dependent manner to form functional hybrid myotubes. Injection of genetically labeled MSCs into wild-type mouse blastocysts revealed a contribution to skeletal but not cardiac muscle development. Disruption of IL-4 and NFATc2/c3 reduced or prevented a contribution of adult stem cells to the development of Il-4 and NFATc2/c3 mutant embryos, further emphasizing the apparent inability of adult stem cells to differentiate fully into striated muscle in a cell-autonomous manner

Activation of Myogenic Differentiation Pathways in Adult Bone Marrow-Derived Stem Cells

During embryogenesis, various cell types can be programmed by potent inducers to follow distinct differentiation paths. In adult life, this ability seems to be restricted to specific multipotent cells. We have identified two cell populations from adult murine bone marrow which express various “stemness” genes. Treatment with Wnt molecules induced transcription of different skeletal muscle marker genes and evoked expression of cardiomyocyte markers. Further characterization of Wnt-induced intracellular signaling cascades revealed that the skeletal muscle program depended on canonical Wnt signaling, while the induction of cardiomyocyte markers seems to require a protein kinase C-dependent pathway. CDO, another component of the machinery directing skeletal muscle induction and expansion, selectively activated skeletal muscle- but not cardiomyocyte-specific genes. Although we were able to turn on various cell-type-specific markers by different induction regimens, we never obtained fully differentiated, functional cells. We conclude that the differentiation of adult stem cells is incomplete and lacks certain cues necessary to acquire a truly functional status

Efficient Homing of Multipotent Adult Mesenchymal Stem Cells Depends on FROUNT-Mediated Clustering of CCR2

SummaryCirculating stem cells of different origin have been demonstrated to improve repair of various organs both after systemic and local application, although the mechanisms that cause these effects are still not fully understood. We have used a combination of DNA microarray analysis and in vitro migration assays to screen for molecules that mediate homing of long-term renewing adult bone marrow-derived multipotent mesenchymal stem cells (BM-MASCs). We show that the cytokine receptor CCR2 is necessary for organ-specific homing of bone marrow-derived MASCs to the heart in a transgenic mouse model and into hearts damaged by ischemia/reperfusion. Homing and migration of stem cells was dependent on the intracellular adaptor molecule FROUNT, which interacts with CCR2. FROUNT was required for polarization of MASCs, resulting in clustering of CCR2 and reorganization of the cytoskeleton. Recruited MASCs summoned by the CCR2 ligand MCP-1/CCL2 expressed SDF1, which might trap additional bone marrow-derived circulating cells to contribute to the complex process of homing and retention of circulating stem and progenitor cells to remodel diseased organs