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In contrast to lower vertebrates, the mammalian heart has a very limited regenerative capacity. Cardiomyocytes, lost after ischemia, are replaced by fibroblasts. Although the human heart is able to form new cardiomyocytes throughout its lifespan, the efficiency of this phenomenon is not enough to substitute sufficient myocardial mass after an infarction. In contrast, zebrafish hearts regenerate through epicardial activation and initiation of myocardial proliferation. With this study we obtain insights into the activation and cellular contribution of the mammalian epicardium in response to ischemia. In a mouse myocardial infarction model we analyzed the spatio-temporal changes in expression of embryonic epicardial, EMT, and stem cell markers and the contribution of cells of the Wt1-lineage to the infarcted area. Though the integrity of the epicardial layer overlaying the infarct is lost immediately after the induction of the ischemia, it was found to be regenerated at three days post infarction. In this regenerated epicardium, the embryonic gene program is transiently re-expressed as well as proliferation. Concomitant with this activation, Wt1-lineage positive subepicardial mesenchyme is formed until two weeks post-infarction. These mesenchymal cells replace the cardiomyocytes lost due to the ischemia and contribute to the fibroblast population, myofibroblasts and coronary endothelium in the infarct, and later also to the cardiomyocyte population. We show that in mice, as in lower vertebrates, an endogenous, epicardium-dependent regenerative response to injury is induced. Although this regenerative response leads to the formation of new cardiomyocytes, their number is insufficient in mice but sufficient in lower vertebrates to replace lost cardiomyocytes. These molecular and cellular analyses provide basic knowledge essential for investigations on the regeneration of the mammalian heart aiming at epicardium-derived cells.
Pubmed ID: 23028582 RIS Download
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It is the distribution arm of their academic laboratory. They operate on a cost-recovery mechanism in order to make the resources generated in their laboratory available to the academic scientific community. While clones and screening services are widely available, library arrays are primarily available to researchers with a scientific need to analyze most clones in the library. This site contains information on currently available BAC and PAC genomic DNA libraries, BAC Clones, PAC Clones, Fosmid Clones, cDNA collections, high-density colony hybridization filters, and BAC and PAC cloning vectors. Protocols used in our laboratory for the hybridization-based screening of colony filters, purification of BAC and PAC DNA, and end-sequencing methodologies, are also provided. BPRC does not list clones, for two reasons: 1)most clones have not been characterized and lack specific data. 2)all clones are part of libraries and all clones from a particular library share common characteristics. Hence, to find out if BPRC has a particular clone, one needs either use Automatic Clone Validation or else find out if the clone is compatible with the range of clone names for a corresponding clone library. Typically (although not always), clone names are derived from the library name. BPRC uses the NCBI-recommended clone nomenclature & library nomenclature. Most arrayed libraries are available in frozen microtiter dish format to academic and non-academic users provided that there is a scientific need for complete-library access. (for instance to annotate, modify or analyze all BAC clones as part of a genome project).
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