Human stem cells shape the future of cardiac regeneration research.
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Animals↗
Biomedical subjects
Christine L Mummery
Publications and source records attributed to Christine L Mummery.
A P19Cl6 GFP reporter line to quantify cardiomyocyte differentiation of stem cells.
The clinical application of stem cell therapies is still limited by the ability to produce defined, differentiated cell populations in large numbers in culture. High throughput screens to identify factors which enhance differentiation to particular lineages and promote expansion of precursors in culture are dependent on the development of sensitive and reproducible assays for screening. Here we describe a bioassay to identify factors with cardiomyogenic activity which enhance the yield of cardiomyocytes from undifferentiated stem cells. The assay is based on a Green Fluorescent Protein (GFP) reporter under the transcriptional control of the 250 bp MLC-2v promoter expressed in pluripotent P19 embryonal carcinoma cells. We show that reporter expression is limited to developing cardiomyocytes and can be used to determine quantitatively the number of ventricular cardiomyocytes formed in cultures under inducing or non-inducing conditions. This assay differs from all others described previously in that it has an easily quantifiable readout, there is negligible background differentiation in the absence of exogenous cardiogenic factors and it is carried out feeder cell-free. Thus, it is entirely independent of competing differentiation inhibitory factors, such as leukemia inhibitory factor. Patch clamp electrophysiology of the GFP-positive cells confirmed their functional ventricular phenotype and indicated that selection on the basis of GFP would provide cells suitable for transplantation.
Animals↗
Spotlight on stem cells--makes old hearts fresh.
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Animals↗
Hereditary hemorrhagic telangiectasia: an update on transforming growth factor beta signaling in vasculogenesis and angiogenesis.
Hereditary hemorrhagic telangiectasia (HHT) is a vascular disorder in humans which has been mapped to two genes, endoglin and activin receptor-like kinase-1 (ALK-1) both of which mediate signaling by transforming growth factor beta ligands in vascular endothelial cells. Animal models have shown that these receptors are not only important for maintaining vascular integrity but also for angiogenesis both during embryonic development and during tumor growth. Here, we review the current status of reported mutations in the context of the clinical manifestations and the effects on the vessel wall both in patients and in animal models of the disease.
Activin Receptors, Type I↗
Transplantation of cells for cardiac repair.
The inability of adult cardiomyocytes to divide to a significant extent and regenerate the myocardium after injury leads to permanent deficits in the number of functional cells, which can contribute to the development and progression of heart failure. The transplantation of skeletal myoblasts or stem cells or cardiomyocytes derived from them into the injured myocardium is a novel and promising approach in the treatment of cardiac disease and the restoration of myocardial function. In this article, skeletal myoblasts and embryonic and bone marrow stem cells are discussed in the context of their potential therapeutic use in cardiac failure. The state of the art in both laboratory and clinic is presented. We discuss current and intrinsic limitations of cardiac cellular transplantation and suggest directions for future research.
Animals↗
Distribution of phosphorylated Smad2 identifies target tissues of TGF beta ligands in mouse development.
Transforming growth factor beta (TGF beta) and related family members control the development of tissues by regulating cell proliferation, differentiation, migration and apoptosis. They transmit signals to the nucleus via phosphorylation of Smad proteins. Here, we used an antibody specifically recognising phosphorylated Smad2 (PSmad2) to identify tissues that have received signals of TGF beta family members acting via Smad2, e.g. TGF betas, activins and nodal. At embryonic day (E)5.5-E8.5, punctuated nuclear PSmad2 staining was scattered throughout the embryo. At E10.5-E12.5, specific zones of the neural tube and brain, ganglia, premuscle masses and precartilage primordia exhibited pronounced nuclear staining, while tissues undergoing epithelial-mesenchymal interactions showed prominent cytoplasmic staining. Interestingly, in the endocardium and most endothelial cells PSmad2 is not detected at E10.5-E12.5, although at E8.5 these cells were stained. These data document the cells that may have received a TGF beta-like stimulus and illustrate, for the first time, the dynamic regulation in space and time of phosphorylated Smad2 during mouse development.
Animals↗
Knock-in of integrin beta 1D affects primary but not secondary myogenesis in mice.
Integrins are extracellular matrix receptors composed of alpha and beta subunits involved in cell adhesion, migration and signal transduction. The beta1 subunit has two isoforms, beta 1A ubiquitously expressed and beta 1D restricted to striated muscle. They are not functionally equivalent. Replacement of beta 1A by beta 1D (beta 1D knock-in) in the mouse leads to midgestation lethality on a 50% Ola/50% FVB background [Baudoin, C., Goumans, M. J., Mummery, C. and Sonnenberg, A. (1998). Genes Dev. 12, 1202-1216]. We crossed the beta 1D knock-in line into a less penetrant genetic background. This led to an attenuation of the midgestation lethality and revealed a second period of lethality around birth. Midgestation death was apparently not caused by failure in cell migration, but rather by abnormal placentation. The beta 1D knock-in embryos that survived midgestation developed until birth, but exhibited severely reduced skeletal muscle mass. Quantification of myotube numbers showed that substitution of beta 1A with beta 1D impairs primary myogenesis with no direct effect on secondary myogenesis. Furthermore, long-term primary myotube survival was affected in beta 1D knock-in embryos. Finally, overexpression of beta 1D in C2C12 cells impaired myotube formation while overexpression of beta 1A primarily affected myotube maturation. Together these results demonstrate for the first time distinct roles for beta1 integrins in primary versus secondary myogenesis and that the beta 1A and beta 1D variants are not functionally equivalent in this process.
Animals↗
Receptor protein tyrosine phosphatase mu expression as a marker for endothelial cell heterogeneity; analysis of RPTPmu gene expression using LacZ knock-in mice.
The receptor-like protein tyrosine phosphatase mu (RPTPmu) belongs to the subfamily of meprin, A5, RPTPmu (MAM) domain-containing RPTPs, which are thought to play an important role in cell-cell adhesion mediated processes. The current study was designed to examine the expression pattern of RPTPmu in mice. We have generated RPTPmu-LacZ knock-in mice that express the beta-galactosidase (LacZ) reporter gene under the control of the RPTPmu promoter. LacZ expression patterns were analysed in embryos and adult mice by whole mount LacZ staining. Analysis of beta-galactosidase activity of heterozygous embryos and adult tissues revealed RPTPmu expression in endothelial cells of arteries and capillaries. In contrast, expression was virtually absent in endothelial cells of veins and in fenestrated endothelial cells in the adult liver and spleen. Moreover, RPTPmu expression was found in endothelial cells from the endocardium and the aorta in embryos, but not in adult mice. In addition to heterogeneous expression in endothelial cells, RPTPmu expression was found in cardiac muscle cells but not in skeletal muscle cells or smooth muscle cells. Expression was also found in Type II pneumonocytes in the lung alveoli and in Purkinje cells and other neurons in the brain. The specific expression of RPTPmu in arterial endothelial cells and in cardiac myocytes suggests that RPTPmu may play a role in the regulation of cardiovascular functions.
Alleles↗
Comprehensive microarray analysis of bone morphogenetic protein 2-induced osteoblast differentiation resulting in the identification of novel markers for bone development.
Osteoblasts are cells responsible for matrix deposition during bone development and although temporal expression of many genes has been related to osteoblast differentiation, a complete description of osteoblast-specific gene regulation will lead to a better understanding of osteoblast function. In this study, microarray technology was used to analyze gene expression on a broad scale during osteoblast differentiation. Expression analysis of 9596 sequences revealed 342 genes and expressed sequence tags (ESTs) to be modulated differentially during a time course experiment in which murine C2C12 mesenchymal progenitor cells were induced to differentiate into mature osteoblasts by treatment with bone morphogenetic protein 2 (BMP-2). By means of hierarchical clustering, these genes were grouped by similarities in their expression profiles, resulting in subsets of early, intermediate, and late response genes, which are representative of the distinct stages of osteoblast differentiation. To identify new bone markers, the bone specificity of the late response genes was determined by comparing BMP-induced expression in C2C12 and MC3T3 osteoblasts with that in NIH3T3 fibroblasts. This resulted in the identification of nine novel genes and ESTs that were induced specifically in osteoblasts, in addition to the well-known markers ALP and osteocalcin. For at least one of these novel genes, Wnt inhibitory factor 1, and two of the ESTs, expression in developing bone was verified in vivo by in situ hybridization of E16.5 mouse embryos. In conclusion, by a combination of in vitro and in vivo screening approaches, a set of new genes related to osteoblast differentiation and skeletal development has been identified.
3T3 Cells↗
Human embryonic stem cells: genetic manipulation on the way to cardiac cell therapies.
Almost 7 years after their first derivation from human embryos, a pressing urgency to deliver the promises of therapies based on human embryonic stem cells (hESC) has arisen. Protocols have been developed to support long-term growth of undifferentiated cells and partially direct differentiation to specific cell lineages. The stage has almost been set for the next step: transplantation in animal models of human disease. Here, we review the state-of-the-art with respect to the transplantation of embryonic stem cell-derived heart cells in animals. One problem affecting progress in this area and functional analysis in vivo in general, is the availability of genetically marked hESC. There are only a few cell lines that express reporter genes ubiquitously, and none is associated with particular lineages; a major hurdle has been the resistance of hESC to established infection and chemical transfection methodologies to introduce ectopic genes. The methods that have been successful are reviewed. We also describe the processes for generating a new, genetically-modified hESC line that constitutively expresses GFP as well as some of its characteristics, including its ability to form cardiomyocytes with electrophysiological properties of ventricular-like cells.
Animals↗