live-cell-imaging-primary-rat-neonatal-cardiomyocytes-following

Live Cell Imaging of Primary Rat Neonatal Cardiomyocytes Following Adenoviral and Lentiviral Transduction Using Confocal Spinning Disk Microscopy

Primary rat neonatal cardiomyocytes are useful in basic in vitro cardiovascular research because they can be easily isolated in large numbers in a single ...

tissue-specific-mirna-expression-profiling-mouse-heart-sections-using

Tissue-specific miRNA Expression Profiling in Mouse Heart Sections Using <em>In Situ</em> Hybridization

micro-RNAs (miRNAs) are single-stranded RNA transcripts that bind to messenger RNAs (mRNAs) and inhibit their translation or promote their degradation. To ...

Yale Cardiovascular Research Center and Section of Cardiovascular Medicine

Yale School of Medicine

Myocardial hypertrophy is an adaptation to increased hemodynamic demands. An increase in heart tissue must be matched by a corresponding expansion of the coronary vasculature to maintain and adequate supply of oxygen and nutrients for the heart. The physiological mechanisms that underlie the coordination of angiogenesis and cardiomyocyte growth are unknown. We report that induction of myocardial angiogenesis promotes cardiomyocyte growth and cardiac hypertrophy through a novel NO-dependent mechanism. We used transgenic, conditional overexpression of placental growth factor (PlGF) in murine cardiac tissues to stimulate myocardial angiogenesis and increase endothelial-derived NO release. NO production, in turn, induced myocardial hypertrophy by promoting proteasomal degradation of regulator of G protein signaling type 4 (RGS4), thus relieving the repression of the Gβγ/PI3Kγ/AKT/mTORC1 pathway that stimulates cardiomyocyte growth. This hypertrophic response was prevented by concomitant transgenic expression of RGS4 in cardiomyocytes. NOS inhibitor L-NAME also significantly attenuated RGS4 degradation, and reduced activation of AKT/mTORC1 signaling and induction of myocardial hypertrophy in PlGF transgenic mice, while conditional cardiac-specific PlGF expression in eNOS knockout mice did not induce myocardial hypertrophy. These findings describe a novel NO/RGS4/Gβγ/PI3Kγ/AKT mechanism that couples cardiac vessel growth with myocyte growth and heart size.

NO triggers RGS4 degradation to coordinate angiogenesis and cardiomyocyte growth.

Myocardial hypertrophy is an adaptive response to hemodynamic demands. Although angiogenesis is critical to support the increase in heart mass with matching blood supply, it may also promote a hypertrophic response. Previously, we showed that cardiac angiogenesis induced by placental growth factor (PlGF), promotes myocardial hypertrophy through the paracrine action of endothelium-derived NO, which triggers the degradation of regulator of G protein signaling 4 (RGS4) to activate the Akt/mTORC1 pathways in cardiomyocytes. Here, we investigated whether miRNAs contribute to the development of hypertrophic response associated with myocardial angiogenesis. We show that miR-182 is upregulated concurrently with the development of hypertrophy in PlGF mice, but not when hypertrophy was blocked by concomitant expression of PlGF and RGS4, or by PlGF expression in eNOS(-/-) mice. Anti-miR-182 treatment inhibits the hypertrophic response and prevents the Akt/mTORC1 activation in PlGF mice and NO-treated cardiomyocytes. miR-182 reduces the expression of Bcat2, Foxo3 and Adcy6 to regulate the hypertrophic response in PlGF mice. Particularly, depletion of Bcat2, identified as a new miR-182 target, promotes Akt(Ser473)/p70-S6K(Thr389) phosphorylation and cardiomyocyte hypertrophy. LV pressure overload did not upregulate miR-182. Thus, miR-182 is a novel target of endothelial-cardiomyocyte crosstalk and plays an important role in the angiogenesis induced-hypertrophic response.

Daniela Tirziu

Department of Internal Medicine

Yale Cardiovascular Research Center and Section of Cardiovascular Medicine

Live Cell Imaging of Primary Rat Neonatal Cardiomyocytes Following Adenoviral and Lentiviral Transduction Using Confocal Spinning Disk Microscopy

Tissue-specific miRNA Expression Profiling in Mouse Heart Sections Using In Situ Hybridization

Daniela Tirziu

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Internal Medicine

Yale Cardiovascular Research Center and Section of Cardiovascular Medicine

Live Cell Imaging of Primary Rat Neonatal Cardiomyocytes Following Adenoviral and Lentiviral Transduction Using Confocal Spinning Disk Microscopy

Tissue-specific miRNA Expression Profiling in Mouse Heart Sections Using In Situ Hybridization

Department of Internal Medicine