BackgroundResident fibroblasts synthesize the cardiac extracellular matrix, and can undergo phenotype conversion to myofibroblasts to augment matrix production, impairing function and contributing to organ failure. A significant gap in our understanding of the transcriptional regulation of these processes exists. Given the key role of this phenotype conversion in fibrotic disease, the identification of such novel transcriptional regulators may yield new targets for therapies for fibrosis.ResultsUsing explanted primary cardiac fibroblasts in gain- and loss-of-function studies, we found that scleraxis critically controls cardiac fibroblast/myofibroblast phenotype by direct transcriptional regulation of myriad genes that effectively define these cells, including extracellular matrix components and α-smooth muscle actin. Scleraxis furthermore potentiated the TGFβ/Smad3 signaling pathway, a key regulator of myofibroblast conversion, by facilitating transcription complex formation. While scleraxis promoted fibroblast to myofibroblast conversion, loss of scleraxis attenuated myofibroblast function and gene expression. These results were confirmed in scleraxis knockout mice, which were cardiac matrix-deficient and lost ~50 % of their complement of cardiac fibroblasts, with evidence of impaired epithelial-to-mesenchymal transition (EMT). Scleraxis directly transactivated several EMT marker genes, and was sufficient to induce mesenchymal/fibroblast phenotype conversion of A549 epithelial cells. Conversely, loss of scleraxis attenuated TGFβ-induced EMT marker expression.ConclusionsOur results demonstrate that scleraxis is a novel and potent regulator of cellular progression along the continuum culminating in the cardiac myofibroblast phenotype. Scleraxis was both sufficient to drive conversion, and required for full conversion to occur. Scleraxis fulfills this role by direct transcriptional regulation of key target genes, and by facilitating TGFβ/Smad signaling. Given the key role of fibroblast to myofibroblast conversion in fibrotic diseases in the heart and other tissue types, scleraxis may be an important target for therapeutic development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-016-0243-8) contains supplementary material, which is available to authorized users.

An adverse environmental experience of the growing fetus may lead to permanent changes in the structure and function of organs that may predispose the individual to chronic diseases in later life; however, nothing is known about the occurrence and mechanisms of heart failure. We employed a rat model in which pregnant dams were fed diets containing either 180 g (normal) or 90 g (low) casein/kg for 2 weeks before mating and throughout pregnancy. The ejection fraction (EF) of the pups exposed to the low-protein (LP) diet was severely depressed in the first 2 weeks of life and was associated with an increase in cardiomyocyte apoptosis. This early depressed cardiac function was followed by progressive recovery and normalization of the EF of the offspring in the LP group. The left ventricular (LV) internal diameters were increased between 24 h and 84 d (12 weeks) of age in the LP-exposed group. Although between 3 d and 2 weeks of age the LV wall of the heart in the LP group was thinner, a progressive increase in LV wall thickness was seen. At 40 weeks of age, although the EF was normal, a two-fold elevation in LV end-diastolic pressure, reduced cardiac output, decreased maximum rates of contraction and relaxation, and reduced mean arterial pressure were observed. Our findings demonstrate that exposure of the developing fetus to a maternal LP diet programs cardiac dysfunction in the offspring in later life.

Aim:SSAT-1 is an enzyme that plays a critical role in cell growth. Amantadine, a FDA-approved antiviral drug, is a substrate for SSAT-1. The utility of amantadine as an agent to demonstrate elevated SSAT-1 activity linked to cancer was conducted.Results:High levels of SSAT-1 expression were measured in tumor human cell lines, and in breast, prostate and lung tumor tissue. An increase in the urinary levels of acetylated amantadine in cancer patients was observed.Conclusion:Increases in SSAT-1 contents in tumor tissue could be of value in targeting cancers with high SSAT-1 expression for confirmation/quantification. The high levels of acetylated amantadine could be used as a simple and useful screening test for the presence of cancer.

Phospholipase C (PLC) activity is known to influence cardiac function. This study was undertaken to examine the status of PLC beta3 in the cardiac cell plasma membrane (sarcolemma, SL) in an experimental model of chronic diabetes. SL membrane was isolated from diabetic rat hearts at 8 weeks after a single i.v. injection of streptozotocin (65 mg/kg body weight). The total SL PLC was decreased in diabetes and was associated with a decrease in SL PLC beta3 activity, which immunofluorescence in frozen diabetic left ventricular tissue sections revealed to be due to a decrease in PLC beta3 protein abundance. In contrast, the SL abundance of Gqalpha was significantly increased during diabetes. These changes were associated with a loss of contractile function (+/- dP/dt). A 2-week insulin treatment of 6-week diabetic animals partially normalized all of these parameters. These findings suggest a defect in PLC beta3-mediated signaling processes may contribute to the cardiac dysfunction seen during diabetes.

-The phenotype conversion of fibroblasts to myofibroblasts plays a key role in the pathogenesis of cardiac fibrosis. Numerous triggers of this conversion process have been identified, including plating of cells on solid substrates, cytokines such as transforming growth factor-␤, and mechanical stretch; however, the underlying mechanisms remain incompletely defined. Recent studies from our laboratory revealed that the transcription factor scleraxis is a key regulator of cardiac fibroblast phenotype and extracellular matrix expression. Here we report that mechanical stretch induces type I collagen expression and morphological changes indicative of cardiac myofibroblast conversion, as well as scleraxis expression via activation of the scleraxis promoter. Scleraxis causes phenotypic changes similar to stretch, and the effect of stretch is attenuated in scleraxis null cells. Scleraxis was also sufficient to upregulate expression of vinculin and F-actin, to induce stress fiber and focal adhesion formation, and to attenuate both cell migration and proliferation, further evidence of scleraxis-mediated regulation of fibroblast to myofibroblast conversion. Together, these data confirm that scleraxis is sufficient to promote the myofibroblast phenotype and is a required effector of stretch-mediated conversion. Scleraxis may thus represent a potential target for the development of novel antifibrotic therapies aimed at inhibiting myofibroblast formation. transcription factor; cardiac fibroblast; stretch; migration; proliferation MYOFIBROBLASTS, AS THE ACTIVATED form of fibroblasts, are major mediators of tissue fibrosis in the heart, lungs, dermis, kidneys, and gastrointestinal tract (17,26,29,36,42). Excess deposition of fibrillar collagens in the extracellular matrix (ECM) of these tissues imparts increased stiffness and reduced organ function. Cardiac fibrosis entails a poor prognosis, negatively impacting both systolic and diastolic function and eventually leading to heart failure and death (43). There currently exists no treatment for the arrest or reversal of cardiac fibrosis (38). However, alteration of the myofibroblast phenotype may provide a novel means for the treatment and even reversal of fibrotic lesions in various tissue types (20,21,23,26,34,37,49).In response to myocardial injury, the release of damage factors [such as profibrotic transforming growth factor-␤ (TGF-␤)] and mechanical strain resulting from the loss of ECM integrity induce activation of cardiac fibroblasts and subsequent conversion to the myofibroblast phenotype (11,14,22,25,32). Cardiac myofibroblasts are characterized by hypersynthesis of fibrillar collagens type I and III, increased expression of ␣-smooth muscle actin (␣-SMA), increased adhesions and cell size, reduced proliferation and migration, and the formation of stress fibers (12,18,39,44,46). The morphological and functional changes that cardiac fibroblasts undergo during their conversion to myofibroblasts are critical to the wound healing process following myocardial injury. The loca...

Because the left ventricular (LV) hypertrophy due to volume overload induced by arteriovenous (AV) shunt was associated with an increase in phospholipase C (PLC) isozyme mRNA levels, PLC is considered to be involved in the development of cardiac hypertrophy. Since the renin-angiotensin system (RAS) is activated in cardiac hypertrophy, the role of RAS in the stimulation of PLC isozyme gene expression in hypertrophied heart was investigated by inducing AV shunt in Sprague-Dawley rats. The animals were treated with or without losartan (20 mg/kg, daily) for 3 days as well as 1, 2 and 4 weeks, and atria, right ventricle (RV) and LV were used for analysis. The increased muscle mass as well as the mRNA levels for PLC β 1 and β 3 in atria and RV, unlike PLC β 3 gene expression in LV, at 3 days of AV shunt were attenuated by losartan. The increased gene expression for PLC β 1 at 2 weeks in atria, at 1 and 4 weeks in RV, and at 2 and 4 weeks in LV was also depressed by losartan treatment. Likewise, the elevated mRNA levels for PLC β 3 in RV at 1 week and in LV at 4 weeks of cardiac hypertrophy were decreased by losartan. On the other hand, the increased levels of mRNA for PLC γ 1 in RV and LV at 2 and 4 weeks of inducing hypertrophy, unlike in atria at 4 weeks were not attenuated by losartan treatment. While the increased mRNA level for PLC δ 1 in LV was reduced by losartan, gene expression for PLC δ 1 was unaltered in atria and decreased in RV at 3 days of inducing AV shunt. These results suggest that changes in PLC isozyme gene expression were chamber specific and time-dependent upon inducing cardiac hypertrophy due to AV shunt. Furthermore, partial attenuation of the increased gene expression for some of the PLC isozymes and no effect of losartan on others indicate that both RAS dependent and independent mechanisms may be involved in hypertrophied hearts due to volume overload.

Tappia, Paramjit S., Mohinder S. Nijjar, Aric Mahay, Nina Aroutiounova, and Naranjan S. Dhalla. Phospholipid profile of developing heart of rats exposed to low-protein diet in pregnancy. Am J Physiol Regul Integr Comp Physiol 289: R1400 -R1406, 2005. First published July 14, 2005; doi:10.1152/ajpregu.00319.2005Although the myocardial phospholipid and fatty acid content have profound effects on the heart function, very little information is available on the effects of restricted maternal protein intake during pregnancy on the phospholipid profile and fatty acid content of the developing heart. The present study was therefore undertaken to examine the effect of pregnant dams fed diets containing either 180 (normal) or 90 (low) g/kg casein diet for 2 wk before mating and throughout pregnancy on myocardial phospholipid and fatty acid content of male offspring. Whereas no changes in phosphatidylcholine and phosphatidylethanolamine were detected, increases in lysophosphatidylcholine, phosphatidylserine, and sphingomyelin were seen in the hearts of offspring in the low-protein (LP) group. Analysis of cardiac fatty acids revealed that although the saturated fatty acid (myristate, palmitate, and stearate) levels were significantly reduced, the unsaturated fatty acid (linoleate, arachidonate, and decosahexanoate) levels were significantly increased in the developing heart in the LP group. Furthermore, assessment of nuclear transcription factors involved in regulation of cardiac metabolism revealed a decrease in myocyte enhancer factor-2C mRNA levels in the LP group, whereas an increase in the mRNA amount of peroxisome proliferator-activated receptor-␣ was observed in this group. These results demonstrate that maternal LP diet can induce changes in the phospholipid profile and fatty acid content of the developing heart, which may have implications for metabolism of the neonatal heart. maternal low-protein diet; fatty acids; energy metabolism THE ENVIRONMENTAL EXPERIENCE of the growing fetus influences the development of specific organs, including the heart (6). We have recently reported that a maternal low-protein (LP) diet induces a severe depression of the contractile function of the neonatal heart (6); however, nothing is known about the mechanisms responsible for this effect. Cardiac phospholipids are known to be organized into functionally differentiated domains (32) and provide both structural integrity and a suitable microenvironment for the normal functioning of membrane proteins (32). Furthermore, polyunsaturated fatty acids (PUFAs), which are important structural and functional components of cell membrane phospholipids, are also required to support normal growth and development and are critical for normal cell function (1,16,23,25,30). The metabolic machinery of the heart is designed to allow many different substrates to be used for ATP synthesis (3), which is required for normal cardiac function. The change in substrate preference during normal maturation from glucose (10,12,(27)(28)(29)31) and lactate to fatty ...

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