Oleg Tarnavski

Bio: Oleg Tarnavski is an academic researcher from Beth Israel Deaconess Medical Center. The author has contributed to research in topics: Muscle hypertrophy & Heart failure. The author has an hindex of 13, co-authored 13 publications receiving 4264 citations. Previous affiliations of Oleg Tarnavski include Novartis.

Endothelial-to-mesenchymal transition contributes to cardiac fibrosis

Abstract: Cardiac fibrosis, associated with a decreased extent of microvasculature and with disruption of normal myocardial structures, results from excessive deposition of extracellular matrix, which is mediated by the recruitment of fibroblasts. The source of these fibroblasts is unclear and specific anti-fibrotic therapies are not currently available. Here we show that cardiac fibrosis is associated with the emergence of fibroblasts originating from endothelial cells, suggesting an endothelial-mesenchymal transition (EndMT) similar to events that occur during formation of the atrioventricular cushion in the embryonic heart. Transforming growth factor-β1 (TGF-β1) induced endothelial cells to undergo EndMT, whereas bone morphogenic protein 7 (BMP-7) preserved the endothelial phenotype. The systemic administration of recombinant human BMP-7 (rhBMP-7) significantly inhibited EndMT and the progression of cardiac fibrosis in mouse models of pressure overload and chronic allograft rejection. Our findings show that EndMT contributes to the progression of cardiac fibrosis and that rhBMP-7 can be used to inhibit EndMT and to intervene in the progression of chronic heart disease associated with fibrosis.

Phosphoinositide 3-kinase(p110α) plays a critical role for the induction of physiological, but not pathological, cardiac hypertrophy

Abstract: An unresolved question in cardiac biology is whether distinct signaling pathways are responsible for the development of pathological and physiological cardiac hypertrophy in the adult. Physiological hypertrophy is characterized by a normal organization of cardiac structure and normal or enhanced cardiac function, whereas pathological hypertrophy is associated with an altered pattern of cardiac gene expression, fibrosis, cardiac dysfunction, and increased morbidity and mortality. The elucidation of signaling cascades that play distinct roles in these two forms of hypertrophy will be critical for the development of more effective strategies to treat heart failure. We examined the role of the p110α isoform of phosphoinositide 3-kinase (PI3K) for the induction of pathological hypertrophy (pressure overload-induced) and physiological hypertrophy (exercise-induced) by using transgenic mice expressing a dominant negative (dn) PI3K(p110α) mutant specifically in the heart. dnPI3K transgenic mice displayed significant hypertrophy in response to pressure overload but not exercise training. dnPI3K transgenic mice also showed significant dilation and cardiac dysfunction in response to pressure overload. Thus, PI3K(p110α) appears to play a critical role for the induction of physiological cardiac growth but not pathological growth. PI3K(p110α) also appears essential for maintaining contractile function in response to pathological stimuli.

Inhibition of mTOR Signaling With Rapamycin Regresses Established Cardiac Hypertrophy Induced by Pressure Overload

Abstract: Background— Rapamycin is a specific inhibitor of the mammalian target of rapamycin (mTOR). We recently reported that administration of rapamycin before exposure to ascending aortic constriction significantly attenuated the load-induced increase in heart weight by ≈70%. Methods and Results— To examine whether rapamycin can regress established cardiac hypertrophy, mice were subjected to pressure overload (ascending aortic constriction) for 1 week, echocardiography was performed to verify an increase in ventricular wall thickness, and mice were given rapamycin (2 mg · kg−1 · d−1) for 1 week. After 1 week of pressure overload (before treatment), 2 distinct groups of animals became apparent: (1) mice with compensated cardiac hypertrophy (normal function) and (2) mice with decompensated hypertrophy (dilated with depressed function). Rapamycin regressed the pressure overload-induced increase in heart weight/body weight (HW/BW) ratio by 68% in mice with compensated hypertrophy and 41% in mice with decompensated h...

Rapamycin Attenuates Load-Induced Cardiac Hypertrophy in Mice

Abstract: Background— Cardiac hypertrophy, or an increase in heart size, is an important risk factor for cardiac morbidity and mortality. The mammalian target of rapamycin (mTOR) is a component of the insulin-phosphoinositide 3-kinase pathway, which is known to play a critical role in the determination of cell, organ, and body size. Methods and Results— To examine the role of mTOR in load-induced cardiac hypertrophy, we administered rapamycin, a specific inhibitor of mTOR, to mice with ascending aortic constriction. Activity of p70 ribosomal S6 kinase 1 (S6K1), an effector of mTOR, was increased by 3.8-fold in the aortic-constricted heart. Pretreatment of mice with 2 mg · kg−1 · d−1 of rapamycin completely suppressed S6K1 activation and S6 phosphorylation in response to pressure overload. The heart weight/tibial length ratio of vehicle-treated aortic-banded mice was increased by 34.4±3.6% compared with vehicle-treated sham-operated mice. Rapamycin suppressed the load-induced increase in heart weight by 67%. Attenua...

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The basics of epithelial-mesenchymal transition

Abstract: The origins of the mesenchymal cells participating in tissue repair and pathological processes, notably tissue fibrosis, tumor invasiveness, and metastasis, are poorly understood. However, emerging evidence suggests that epithelial-mesenchymal transitions (EMTs) represent one important source of these cells. As we discuss here, processes similar to the EMTs associated with embryo implantation, embryogenesis, and organ development are appropriated and subverted by chronically inflamed tissues and neoplasias. The identification of the signaling pathways that lead to activation of EMT programs during these disease processes is providing new insights into the plasticity of cellular phenotypes and possible therapeutic interventions.

Molecular mechanisms of epithelial–mesenchymal transition

Abstract: The transdifferentiation of epithelial cells into motile mesenchymal cells, a process known as epithelial-mesenchymal transition (EMT), is integral in development, wound healing and stem cell behaviour, and contributes pathologically to fibrosis and cancer progression. This switch in cell differentiation and behaviour is mediated by key transcription factors, including SNAIL, zinc-finger E-box-binding (ZEB) and basic helix-loop-helix transcription factors, the functions of which are finely regulated at the transcriptional, translational and post-translational levels. The reprogramming of gene expression during EMT, as well as non-transcriptional changes, are initiated and controlled by signalling pathways that respond to extracellular cues. Among these, transforming growth factor-β (TGFβ) family signalling has a predominant role; however, the convergence of signalling pathways is essential for EMT.