Final Report Summary - WT1HEART (Identification of new targets of Wt1 during cardiovascular development.) Heart failure constitutes one of the leading causes of death worldwide. Understanding the molecular mechanisms involved in the formation of the embryonic heart constitutes the first step in the generation of therapeutic strategies for treatment of cardiovascular disease. The epicardium, the most external component of the heart is an important source of cardiovascular precursor cells and paracrine factors that are required for adequate heart formation. Thus, the epicardium represents a critical developmental source of cells and signals which, whilst quiescent under normal conditions, can revert to act as a multipotent cell source and trophic signalling centre to modulate the regenerative response after MI. WT1 expression is one of the main hallmarks of the embryonic epicardium signature and this expression is reactivated after myocardial infarction. Signalling pathways regulated by WT1 that promote heart development have started to be described, however there is little information about signalling pathways regulated by WT1 that could act in a negative manner. The principal objectives of the proposed project were to identify new targets of WT1 during cardiovascular development, to explore their role in formation and differentiation process of epicardial cardiovascular precursor cells and to dissect some of the mechanisms involved. We performed a microarray-based expression analysis of transcriptional changes associated with Wt1 deletion in immortalized embryonic epicardial cells. The microarray study reveals an unexpected role for WT1 in repressing the expression of interferon regulated genes that could be involved in a negative regulation of heart morphogenesis. We found that WT1 is required to repress the expression of the chemokines Ccl5 and Cxcl10 in epicardial cells. Functional assays demonstrate that CXCL10 and CCL5 inhibit epicardial cells migration and the proliferation of cardiomyocytes respectively. WT1 regulates the expression levels of Cxcl10 and Ccl5 in epicardial cells directly and indirectly through increasing the levels of IRF7. Our results provide a novel mechanism of how epicardial cells control heart morphogenesis by producing inhibitory molecules. Thus, heart formation requires a finely balanced equilibrium between stimulatory and inhibitory factors. The proposed project has contributed to a substantial increase in the knowledge of the function of WT1 in epicardium development. As epicardial cell reactivation after a myocardial damage is linked with WT1 expression, the present work has potential implications in adult heart repair a research field which is of outstanding interest due to the strong impact of cardiovascular diseases. The results obtained from this grant are expected to contribute to the design of new strategies with the potential to regulate coronary blood vessel development and myocardium growth two important functions required for heart regeneration and repair. The proposed research has also contributed to the principal objectives of the European Research Area, supporting the career consolidation as independent investigator and reinforcing and increasing the place and role of women in science and research from the perspective of equal opportunities.
