Gene Regulatory Mechanisms that Repress BMP2 in Pathological Calcification

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The goal of this project is to understand how aging and chronic kidney disease (CKD) promote bone morphogenetic protein 2 (BMP2) synthesis that furthers pathological calcification of the heart valves and vasculature. Post-transcriptional regulatory mechanisms repress BMP2 in aorta and aortic valve. We hypothesize that (1) this repression is essential for controlling BMP2 levels in the adult and that (2) conditions such as aging and CKD impair the function of factors that mediate this repression in healthy heart valves and aorta. We will test these hypotheses in aged normal mice (24 months) and in the Klotho null mouse which models age-related disorders, including CKD. Klotho null mice suffer premature aging and death occurs at 7 - 8 weeks of age. At this time, extensive calcification of the heart valves, vasculature, and other soft tissues has occurred. AIM 1 is to test the influence of conditionally deleting a strong repressive element in the 3'untranslated region (UTR) of Bmp2 on calcification in normal aged mice and in Klotho null mice with premature aging and aging associated renal dysfunction. We will use recently developed Bmp2 alleles to assess how the deletion of this potent post-transcriptional repressor influences the course of calcification associated with aging and renal dysfunction. Preliminary results indicate that the UCS inhibits calcification. AIM 2 is to identify and compare miRNA signatures unique to young, healthy aorta and aortic valve to the signatures of these tissues from normal aged mice and in Klotho null mice with premature aging and severe vascular calcification. Within these profiles, we will focus on post- transcriptional repressive factors (miRNAs) that target the Bmp2 UCS and contribute to 3'UTR mediated repression in healthy tissues. AIM 3 is to test how selected and validated miRNAs influence the expression Bmp2 and downstream osteogenic events that lead to calcification in Klotho null mice bearing our unique transgenes. Our novel Bmp2 reporter mouse will expedite pre-clinical testing of miRNA therapies that prevent pathological calcification. Our newly developed Bmp2 allele (Aim 1) will differentiate changes due these miRNAs targeting Bmp2 relative to off-target genes. The outcomes of the proposed research will be (1) increased understanding of how BMP2 influences pathological calcification, (2) the identification and analyses of potential miRNA biomarkers, and (3) new therapeutic leads for controlling pathological calcification.