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The principal regulator of cellular response to low oxygen is hypoxia-inducible factor (HIF)-1, which is stabilized in several forms of heart failure. Our laboratory developed a mouse strain in which a stable form of HIF-1 can be inducibly expressed in cardiomyocytes. Strikingly, these mice show a rapid decrease in cardiac contractility and a rapid loss of SERCA2 protein, which is also seen in heart failure. Interestingly, while the SERCA2 transcript decreased, it did not fully account for the observed decrease in protein. We therefore investigated whether HIF-1-regulated microRNA could impair SERCA translation. Multiple screening analyses identified the microRNA miR-29c to be substantially upregulated upon HIF-1 induction and to have complementarity to SERCA, and therefore be a potential regulator of SERCA2 expression in hypoxia. Subsequent evaluation confirmed that miR-29c reduced SERCA2 expression and Ca2+ reuptake. Additionally, administration of an antagonist sequence (antimir) improved cardiac contractility and SERCA2 expression in HIF transgenic mice. To extend the significance of these findings, we examined miR-29c expression in physiological hypoxia. Surprisingly, miR-29c decreased in these settings. We also treated mice with antimir before infarction to see if further suppression of miR-29c could improve cardiac function. While no improvement in contractility or SERCA2 was observed, reduction of heart size after infarction indicated that the antimir could modulate cardiac physiology. These results demonstrate that while a HIF-1- regulated microRNA, miR-29c, can reduce SERCA2 expression and contractility, additional factors in the ischemic milieu may limit these effects. Efforts to develop miRNA-based therapies will need to explore and account for these additional countervailing effects. [ABSTRACT FROM AUTHOR]

Most cases of congenital obstructive nephropathy are the result of ureteropelvic junction obstructions, and despite their high prevalence, we have a poor understanding of their etiology and scarcity of genetic models. The eight-protein exocyst complex regulates polarized exocytosis of intracellular vesicles in a large variety of cell types. Here we report generation of a conditional knockout mouse for Sec10, a central component of the exocyst, which is the first conditional allele for any exocyst gene. Inactivation of Sec10 in ureteric bud-derived cells using Ksp1.3-Cre mice resulted in severe bilateral hydronephrosis and complete anuria in newborns, with death occurring 6–14 hours after birth. Sec10FL/FL;Ksp-Cre embryos developed ureteropelvic junction obstructions between E17.5 and E18.5 as a result of degeneration of the urothelium and subsequent overgrowth by surrounding mesenchymal cells. The urothelial cell layer that lines the urinary tract must maintain a hydrophobic luminal barrier again urine while remaining highly stretchable. This barrier is largely established by production of uroplakin proteins that are transported to the apical surface to establish large plaques. By E16.5, Sec10FL/FL;Ksp-Cre ureter and pelvic urothelium showed decreased uroplakin-3 protein at the luminal surface, and complete absence of uroplakin-3 by E17.5. Affected urothelium at the UPJ showed irregular barriers that exposed the smooth muscle layer to urine, suggesting this may trigger the surrounding mesenchymal cells to overgrow the lumen. Findings from this novel mouse model show Sec10 is critical for the development of the urothelium in ureters, and provides experimental evidence that failure of this urothelial barrier may contribute to human congenital urinary tract obstructions. [ABSTRACT FROM AUTHOR]

Abstract: Our aim was to evaluate the delivery of transposase-based vectors by ultrasound targeted microbubble destruction (UTMD) in mice. DNA vectors were attached to cationic lipid microbubbles (1–3 μm in diameter), injected intravenously and delivered to the liver by destruction of the carrier bubbles with ultrasound in burst mode at 1.0 MHz, 20-μs pulse duration, 10-Hz pulse repetition frequency and ∼1.3-MPa acoustic peak negative pressure. We evaluated the expression and genomic integration of conventional (pcDNA3) and piggyBac transposase-based (pmGENIE) reporter vectors. In vivo, we observed UTMD-mediated liver-specific expression of pmGENIE for an average of 24 d, compared with 4 d with pcDNA3. Reporter expression was located predominately near blood vessels initially, whereas expression after 3 d was more evenly distributed through the parenchyma of the liver. We confirmed random genomic integration for pmGENIE in vitro; however, integration events for pmGENIE in vivo were targeted to specific areas of chromosome 14. Our results suggest that a combination of UTMD and non-viral DNA transposase vectors can mediate weeks of hepatic-specific gene transfer in vivo, and analyses performed by non-restrictive linear amplification-mediated (nrLAM) polymerase chain reaction, cloning and sequencing identify an unexpected tropism for integration within a specific sequence on chromosome 14 in mice. UTMD delivery of transgenes may be useful for the treatment of hepatic gene deficiency disorders. [Copyright &y& Elsevier]