Tarek Kashour

Adipose-derived stem cells are an effective cell candidate for treatment of heart failure: an MR imaging study of rat hearts

This study assessed the potential therapeutic efficacy of adipose-derived stem cells (ASCs) on infarcted hearts. Myocardial infarction was induced in rat hearts by occlusion of the left anterior descending artery (LAD). One week after LAD occlusion, the rats were divided into three groups and subjected to transplantation of ASCs or transplantation of cell culture medium (CCM) or remained untreated. During a 1-mo recovery period, magnetic resonance imaging showed that the ASC-treated hearts had a significantly greater left ventricular (LV) ejection fraction and LV wall thickening than did the CCM-treated and untreated hearts. The capillary density in infarct border zone was significantly higher in the ASC-treated hearts than in the CCM-treated and untreated hearts. However, only 0.5% of the ASCs recovered from the ASC-treated hearts were stained positive for cardiac-specific fibril proteins. It was also found that ASCs under a normal culture condition secreted three cardiac protective growth factors: vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor-1. Results of this study suggest that ASCs were able to improve cardiac function of infarcted rat hearts. Paracrine effect may be the mechanism underlying the improved cardiac function and increased capillary density.

Superparamagnetic iron oxide does not affect the viability and function of adipose-derived stem cells, and superparamagnetic iron oxide-enhanced magnetic resonance imaging identifies viable cells.

The objectives of this study were (1) to determine whether superparamagnetic iron oxide (SPIO) affects viability, transdifferentiation potential and cell-factor secretion of adipose-derived stem cells (ASCs); and (2) to determine whether SPIO-enhanced magnetic resonance (MR) imaging highlights living stem cells. Rat ASCs were incubated in SPIO-containing cell culture medium for 2 days. The SPIO-treated ASCs were then subjected to adipogenic, osteogenic and myogenic transdifferentiation. Expression of vascular endothelial growth factor, hepatocyte growth factor and insulin-like growth factor 1 by the SPIO-treated ASCs was measured using reverse transcription polymerase chain reaction. Cell viability was assessed using trypan blue stain. For in vivo experiments, SPIO-labeled ASCs were injected into 10 rat hearts. The hearts were monitored using MRI. We found that survival rate of the ASCs cultured in the SPIO-containing medium was very high (97-99%). The SPIO-treated ASCs continued to express specific markers for the three types of transdifferentiation. Expression of the cell factors by the ASCs was not affected by SPIO. Signal voids on MR images were associated with the living SPIO-labeled ASCs in the rat hearts. We conclude that SPIO does not affect viability, transdifferentiation potential or cell-factor secretion of ASCs. MRI mainly highlights living SPIO-labeled stem cells.

The role of transforming growth factor beta signaling in messenger RNA stability

Transforming growth factor beta (TGF-β) is a biologically multipotent regulatory protein implicated in functions that include the regulation of cellular growth, differentiation, extracellular matrix formation, and wound healing. It also plays a role in the pathologies of Alzheimers disease, cancer and autoimmune disorders. TGF-β modulates gene expression by affecting transcriptional activation and mRNA turnover rate. Steady-state mRNA levels depend on both the transcriptional activity and mRNA half-life. The stability of mRNA can be modified by the binding of trans-acting factors to cis-elements on the message. These can protect the mRNA from cleavage by RNAses, or they may promote mRNA cleavage. Changes in mRNA stability can lead to changes in the proteome and subsequently in cellular metabolism. The SMAD family of proteins has been implicated in the transduction of the TGF-β signal, where they regulate transcriptional activity. This review attempts to provide new insights into the role played by TGF-β in the regulation of mRNA turnover.

Late Simian virus 40 transcription factor is a target of the phosphoinositide 3-kinase/Akt pathway in anti-apoptotic Alzheimer's amyloid precursor protein signalling.

The association of familial Alzheimers disease (FAD) with mutations in Alzheimers amyloid precursor protein (APP) suggests important functions for APP in the central nervous system. Mutations in APP impair its function to confer resistance to apoptosis in cells under stress, and this may contribute to neurodegeneration in Alzheimers disease (AD) brain, but the mechanisms involved are unknown. We examined the role of the late Simian virus 40 transcription factor (LSF), in anti-apoptotic APP pathways. We show that in APP-deficient B103 cells, expression of wild-type human APP (hAPPwt), but not of FAD-mutant APP, inhibited staurosporine (STS)-induced apoptosis. This inhibition was further enhanced by expression of LSFwt, although LSFwt alone was not sufficient to inhibit STS-induced apoptosis. In contrast, expression of dominant-negative LSF led to a marked increase in STS-induced cell death that was significantly blocked by hAPPwt. These effects of APP were accompanied by LSF nuclear translocation and dependent gene transcription. The activation of LSF is dependent on the expression of hAPPwt and is inhibited by the expression of dominant-negative forms of either phosphoinositide 3-kinase or Akt. These results demonstrate that LSF activation is required for the neuroprotective effects of APP via phosphoinositide 3-kinase/Akt signalling. Alterations in this pathway by aberrations in APP and/or LSF could promote neuronal loss in AD brain, due to secondary insults. Thus a link is established between APP and LSF and AD.

Myogenic signaling by lithium in cardiomyoblasts is Akt independent but requires activation of the β-catenin-Tcf/Lef pathway

Rat H9c2 cardiomyoblasts can proliferate and maintain an undifferentiated state in the presence of serum. These cardiomyoblasts have been used as a cellular model to study myogenic differentiation after serum withdrawal. Here, we examined the effects of lithium, a known inhibitor of glycogen synthase kinase-3beta and activator of Wnt pathway in myogenic differentiation. We show that in the presence of serum, lithium induced the differentiation of H9c2 cells as measured by multinucleated myotube formation and expression of the muscle-specific proteins, myogenin and skeletal alpha-actin. This differentiation was preceded by nuclear accumulation of beta-catenin, which was associated with increased Tcf/Lef-dependent transcription. We also observed that lithium mediated the activation of phosphatidylinositol 3-kinase (PI3-kinase) and its downstream target Akt. Inhibition of PI3-kinase by LY294002 and over-expression of dominant-negative PI3-kinase caused a marked reduction in beta-catenin levels. This inhibition was associated with decreased beta-catenin-Tcf/Lef-dependent transcription, lack of multinucleated myotube formation, and expression of the muscle-specific proteins. In contrast, expression of dominant-negative Akt failed to inhibit the effects of lithium. We conclude that the capacity of lithium to overcome the inhibitory effects of serum and to induce the differentiation of H9c2 cardiomyoblasts is mediated, in part, by the stabilization and nuclear translocation of beta-catenin in a PI3-kinase-dependent but Akt-independent manner. Once activated, beta-catenin then interacts with the Lef/Tcf complex to regulate expression of myogenic-inducing genes.

Adipose tissue houses different subtypes of stem cells.

Adipose tissue stromal fraction (ASF) contains multipotent cells capable of differentiation towards several lineages and may be used for the treatment of various degenerative diseases. However, the multipotent cells within ASF have not been fully characterized. In this study we have attempted to characterize stem cells in the ASF obtained through serial dilution. Five single-cell clones were studied. It was found that the single-cell clones exhibited slight but significant differences in proliferative capacity and differentiation potential. We conclude that ASF houses different subtypes of stem cells.

Percutaneous balloon valvuloplasty for pulmonic stenosis: the role of multimodality imaging.

Pulmonic valvular stenosis represents the most frequent cause of right ventricular outflow obstruction. Transthoracic echocardiography is the imaging modality of choice in the diagnosis, evaluation and longitudinal follow‐up of individuals with pulmonic stenosis (PS). Although valvular PS is usually diagnosed by two‐dimensional imaging, Doppler echocardiography allows for the quantification of severity of the valvular lesion. In patients with limited acoustic windows, computed tomography and cardiac magnetic resonance imaging may provide complementary anatomical characterization of the pulmonic annulus and valve prior to percutaneous balloon valvuloplasty.

Forgotten but not extinct: lessons in hemodynamics and imaging from pancardiac rheumatic heart disease.

Simultaneous valvular, pericardial and myocardial involvement from chronic rheumatic heart disease is a rare phenomenon. We describe a novel patient with simultaneous aortic stenosis, mitral stenosis, constrictive pericarditis and pathologic myocardial rheumatic involvement. Lessons and pitfalls of the catheterization hemodynamics for concomitant multivalvular disease and constrictive physiology are outlined. Echocardiographic, computed tomographic (CT) imaging and pathologic findings are presented for the pancardiac involvement in this case.

ECHO ROUNDS: Percutaneous Balloon Valvuloplasty for Pulmonic Stenosis: The Role of Multimodality Imaging: PERCUTANEOUS BALOON VALVULOPLASTY FOR PULMONIC STENOSIS

Pulmonic valvular stenosis represents the most frequent cause of right ventricular outflow obstruction. Transthoracic echocardiography is the imaging modality of choice in the diagnosis, evaluation and longitudinal follow‐up of individuals with pulmonic stenosis (PS). Although valvular PS is usually diagnosed by two‐dimensional imaging, Doppler echocardiography allows for the quantification of severity of the valvular lesion. In patients with limited acoustic windows, computed tomography and cardiac magnetic resonance imaging may provide complementary anatomical characterization of the pulmonic annulus and valve prior to percutaneous balloon valvuloplasty.