Toward molecular strategies for heart disease--past, present, future

MicroRNA-327 regulates cardiac hypertrophy and fibrosis induced by pressure overload

MicroRNA (miRNA/miR) dysregulation has been reported to be fundamental in the development and progression of cardiac hypertrophy and fibrosis. In the present study, miR-327 levels in fibroblasts were increased in response to cardiac hypertrophy induced by transverse aortic constriction with prominent cardiac fibrosis, particularly when compared with the levels in unstressed cardiomyocytes. In neonatal rat cardiac fibroblasts, induced expression of miR-327 upregulated fibrosis-associated gene expression and activated angiotensin II-induced differentiation into myofibroblasts, as assessed via α-smooth muscle actin staining. By contrast, miR-327 knockdown mitigated angiotensin II-induced differentiation. Cardiac fibroblast proliferation was not affected under either condition. In a mouse model subjected to transverse aortic constriction, miR-327 knockdown through tail-vein injection reduced the development of cardiac fibrosis and ventricular dysfunction. miR-327 was demonstrated to target integrin β3 and diminish the activation of cardiac fibroblasts. Thus, the present study supports the use of miR-327 as a therapeutic target in the reduction of cardiac fibrosis.

Role of bone marrow mesenchymal stem cells in pancreas self-restoration and pathological regeneration

AIM: To investigate the role of bone marrow mesenchymal stem cells (MSC) in pancreatic self-restoration and pathological regeneration.

METHODS: Sixty Sprague-Dawley (SD) rats were randomly assigned into 5 groups (n = 12). Group A acted as the normal negative control without any treatment, and group B received labeled autologous bone marrow MSC only. Group C was induced mild acute pancreatitis by subcutaneous injection of caerulein 20 mg/(kg·h) 4 times, and group D was induced severe acute pancreatitis by intraperitoneal injection of L-arginine (2 g/kg) twice. Group E was the stem cell mobilized group treated by injection of granulocyte-colony stimulating factor (G-CSF) into rats for 3 d at a dose of 40 mg/(kg·d) 3 d before the induction of SAP. MSC were stained with Hoechst33258 and transplanted into their original cavity. Two and eight weeks after transplantation, the rats were sacrificed, and pancreatic tissues were harvested. Samples were snap-frozen and sectioned on a cryostat. The presence of labeled MSC in the cryostat prepared was examined directly by fluorescent microscopy. The positive sections were selected for further immunofluorescence assay. Anti-Cytokeratin(CK)19, anti-glucagon and anti-insulin immunofluorescence staining were performed on the pancreatic sections to determine whether incorporated MSC differentiated into mature pancreatic cells.

RESULTS: Frozen section of pancreas in group A didn't appear yellow-green fluorescence. The labeled MSC were detected in normal pancreatic tissues in group B and in injured pancreatic tissues in group C, D and E, especially in group E, which lasted 8 wk. The results of immunofluorescence analysis were as follows: All tests were negative in controls, including spontaneous fluorescence control, fluorescence antibody control and inhibitory control. No positive cells with CK19, insulin and glucagons were visualized in group A and D (died rats). Positive cells with CK19, which differentiated from the labeled MSC, were found in normal pancreas in group B and injured pancreatic models in group C, E and D (survival rats). No positive cells with insulin and glucagons were observed 2 wk after modeling, while the positive cells appeared 8 wk after modeling in group C, D and E.

CONCLUSION: The bone marrow MSC participate in pancreatic self-restoration and pathological regeneration.

[Genetically modified animal models in cardiovascular research]

It is a basic tenet of molecular and clinical medicine that specific protein complements underlie cell and organ function. Since cellular and ultimately organ function depend upon the polypeptides that are present, it is not surprising that when function is altered changes in the protein pools occur. In the heart, numerous examples of contractile protein changes correlate with functional alterations, both during normal development and during the development of numerous pathologies. Similarly, different congenital heart diseases are characterized by certain shifts in the motor proteins. To understand these relationships, and to establish models in which the pathogenic processes can be studied longitudinally, it is necessary to direct the heart to stably synthesize, in the absence of other peliotropic changes, the candidate protein. Subsequently, one can determine if the protein's presence causes the effects directly or indirectly with the goal being to define potential therapeutic targets. By affecting the heart's protein complement in a defined manner, one has the means to establish both mechanism and the function of the different mutated proteins of protein isoforms. Gene targeting and transgenesis in the mouse provides a means to modify the mammalian genome and the cardiac motor protein complement. By directing expression of an engineered protein to the heart, one is now able to effectively remodel the cardiac protein profile and study the consequences of a single genetic manipulation at the molecular, biochemical, cytological and physiologic levels, both under normal and stress stimuli.

Life and death of a cardiac myocyte: principles of cellular biology

If the future of extracorporeal circulation is to include approaches to enhance localized or widespread distribution of cells, and/or gene transfer for augmentation of cardiac function, it is imperative that we gain an increased understanding of the mechanisms that define the cardiac myocyte phenotype. The purpose of this paper is to review the natural history of the cardiac myocyte. A variety of signals determine the cellular processes that characterize birth, growth, differentiation and death of cardiomyocytes. Examined here are primary aspects of the molecular genetics of growth and development, including signal transduction, protein phosphorylation, the cell division cycle, and transcriptional activation. This review is intended to be an update on insights into molecular aspects of the cell, with emphasis on gene expression during cardiac myogenesis and a discussion of its relevance to the field of extracorporeal circulation. In addition, the current status of research in myogenesis is presented.

Identification of differentially expressed genes in cardiac hypertrophy by analysis of expressed sequence tags

Cardiac hypertrophy is an adaptive response to chronic hemodynamic overload. We employed a whole-genome approach using expressed sequence tags (ESTs) to characterize gene transcription and identify new genes overexpressed in cardiac hypertrophy. Analysis of general transcription patterns revealed a proportional increase in transcripts related to cell/organism defense and a decrease in transcripts related to cell structure and motility in hypertrophic hearts compared to normal hearts. Detailed comparison of individual gene expression identified 64 genes potentially overexpressed in hypertrophy, of 232 candidate genes derived from a set of 77,692 cardiac ESTs, including 47,856 ESTs generated in our laboratory. Of these, 29 were good candidates (P < 0.0002) and 35 were weaker candidates (P < 0.005). RT-PCR of a number of these candidate genes demonstrated correspondence of EST-based predictions of gene expression with in vitro levels. Consistent with an organ under various stresses, up to one-half of the good candidates predicted to exhibit differential expression were genes potentially involved in stress response. Analyses of general transcription patterns and of single-gene expression levels were also suggestive of increased protein synthesis in the hypertrophic myocardium. Overall, these results depict a scenario compatible with current understanding of cardiac hypertrophy. However, the identification of several genes not previously known to exhibit increased expression in cardiac hypertrophy (e.g., prostaglandin D synthases; CD59 antigen) also suggests a number of new avenues for further investigation. These data demonstrate the utility of genome-based resources for investigating questions of cardiovascular biology and medicine.

Molecular advances in cardiac and cardiovascular disease

Recent advances in the field of molecular biology have led to a better understanding of the pathological mechanisms of cardiovascular disease. The impact of these findings will shape the future of treatment modalities for cardiovascular disorders. Postulated targets and biological rationale of new techniques are being developed in a race towards molecular therapies for vascular diseases. Whether it is modulation of transmembrane cell receptors or phenotypic changes via vectors that mediate gene transfer, there is no doubt that molecular strategies will be an integral part of the future. Here we examine past and recent perspectives, describe directions and challenges in cardiac and cardiovascular areas of research, and discuss relevance to the field of cardiovascular perfusion.