DIGE proteome analysis reveals suitability of ischemic cardiac in vitro model for studying cellular response to acute ischemia and regeneration

Experimental models of cardiac physiology and pathology

Experimental models of cardiac disease play a key role in understanding the pathophysiology of the disease and developing new therapies. The features of the experimental models should reflect the clinical phenotype, which can have a wide spectrum of underlying mechanisms. We review characteristics of commonly used experimental models of cardiac physiology and pathophysiology in all translational steps including in vitro, small animal, and large animal models. Understanding their characteristics and relevance to clinical disease is the key for successful translation to effective therapies.

A human in vitro platform for the evaluation of pharmacology strategies in cardiac ischemia

Cardiac ischemic events increase the risk for arrhythmia, heart attack, heart failure, and death and are the leading mortality condition globally. Reperfusion therapy is the first line of treatment for this condition, and although it significantly reduces mortality, cardiac ischemia remains a significant threat. New therapeutic strategies are under investigation to improve the ischemia survival rate; however, the current preclinical models to validate these fail to predict the human outcome. We report the development of a functional human cardiac in vitro system for the study of conduction velocity under ischemic conditions. The system is a bioMEMs platform formed by human iPSC derived cardiomyocytes patterned on microelectrode arrays and maintained in serum-free conditions. Electrical activity changes of conduction velocity, beat frequency, and QT interval (the QT-interval measures the period from onset of depolarization to the completion of repolarization) or action potential length can be evaluated over time and under the stress of ischemia. The optimized protocol induces >80% reduction in conduction velocity, after a 4 h depletion period, and a partial recovery after 72 h of oxygen and nutrient reintroduction. The sensitivity of the platform for pharmacological interventions was challenged with a gap junction modulator (ZP1609), known to prevent or delay the depression of conduction velocity induced by ischemic metabolic stress. ZP1609 significantly improved the drastic drop in conduction velocity and enabled a greater recovery. This model represents a new preclinical platform for studying cardiac ischemia with human cells, which does not rely on biomarker analysis and has the potential for screening novel cardioprotective drugs with readouts that are closer to the measured clinical parameters.

Identification of potential genes for human ischemic cardiomyopathy based on RNA-Seq data

Ischemic cardiomyopathy (ICM) is an important cause of heart failure, yet no ICM disease genes were stored in any public databases. Mutations of genes provided by RNA-Seq data could set a foundation for a variety of biological processes. This also made it possible to elucidate the mechanism and identify potential genes for ICM. In this paper, an integrated co-expression network was constructed using univariate and bivariate canonical correlation analysis for RNA-Seq data of human ICM samples. Three ICM-related modules were recognized after comparing between Pearson correlation coefficients of ICM samples and normal controls. Furthermore, 32 ICM potential genes were identified from ICM-related modules considering protein-protein interactions. Most of these genes were verified to be involved in ICM and diseases caused it by OMIM and literature. Our study could provide a novel perspective for potential gene identification and the pathogenesis for ICM and other complex diseases.

Proteomics of cell-cell interactions in health and disease

The mechanisms of cell-cell communications are now under intense study by proteomic approaches. Proteomics has unraveled changes in protein profiling as the result of cell interactions mediated by ligand/receptor, hormones, soluble factors, and the content of extracellular vesicles. Besides being a brief overview of the main and profitable methodologies now available (evaluating theory behind the methods, their usefulness, and pitfalls), this review focuses on-from a proteome perspective-some signaling pathways and post-translational modifications (PTMs), which are essential for understanding ischemic lesions and their recovery in two vital organs in mammals, the heart, and the kidney. Knowledge of misdirection of the proteome during tissue recovery, such as represented by the convergence between fibrosis and cancer, emerges as an important tool in prognosis. Proteomics of cell-cell interaction is also especially useful for understanding how stem cells interact in injured tissues, anticipating clues for rational therapeutic interventions. In the effervescent field of induced pluripotency and cell reprogramming, proteomic studies have shown what proteins from specialized cells contribute to the recovery of infarcted tissues. Overall, we conclude that proteomics is at the forefront in helping us to understand the mechanisms that underpin prevalent pathological processes.

Expression of calcineurin, calpastatin and heat shock proteins during ischemia and reperfusion

Objective

Calcineurin (CaN) interacts with calpains (Calpn) and causes cellular damage eventually leading to cell death. Calpastatin (Calp) is a specific Calpn inhibitor, along with CaN stimulation has been implicated in reduced cell death and self-repair. Molecular chaperones, heat shock proteins (Hsp70 and Hsp90) acts as regulators in Calpn signaling. This study aims to elucidate the role of CaN, Calp and Hsps during induced ischemia and reperfusion in primary cardiomyocyte cultures (murine).

Methods and results

Protein expression was analyzed concurrently with viability using flow cytometry (FACS) in ischemia- and reperfusion-induced murine cardiomyocyte cultures. The expression of Hsp70 and Hsp90, both being molecular chaperones, increased during ischemia with a concurrent increase in death of cells expressing these proteins. The relative expression of Hsp70 and Hsp90 during ischemia with respect to CaN was enhanced in comparison to Calp. Reperfusion slightly decreased the number of cells expressing these chaperones. There was no increase in death of cells co-expressing Hsp70 and Hsp90 along with CaN and Calp. CaN expression peaked during ischemia and subsequent reperfusion reduced its expression and cell death. Calp expression increased both during ischemia and subsequent reperfusion but cell death decreased during reperfusion.

Conclusion

The present study adds to the existing knowledge that Hsp70, Hsp90, CaN and Calp interact with each other and play significant role in cardio protection.

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Differential expression of calcineurin and calpastatin during ischemia and reperfusion.

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Enhanced ischemia induced cell death in cells expressing Hsp70 and Hsp90.

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Cardio protective role of calcineurin, calpastatin, Hsp70 and Hsp90.

Ischemia and reperfusion induce differential expression of calpastatin and its homologue high molecular weight calmodulin-binding protein in murine cardiomyocytes

In the heart, calpastatin (Calp) and its homologue high molecular weight calmodulin-binding protein (HMWCaMBP) regulate calpains (Calpn) by inhibition. A rise in intracellular myocardial Ca²⁺ during cardiac ischemia activates Calpn thereby causing damage to myocardial proteins, which leads to myocyte death and consequently to loss of myocardial structure and function. The present study aims to elucidate expression of Calp and HMWCaMBP with respect to Calpn during induced ischemia and reperfusion in primary murine cardiomyocyte cultures. Ischemia and subsequently reperfusion was induced in ∼80% confluent cultures of neonatal murine cardiomyocytes (NMCC). Flow cytometric analysis (FACS) has been used for analyzing protein expression concurrently with viability. Confocal fluorescent microscopy was used to observe protein localization. We observed that ischemia induces increased expression of Calp, HMWCaMBP and Calpn. Calpn expressing NMCC on co-expressing Calp survived ischemic induction compared to NMCC co-expressing HMWCaMBP. Similarly, living cells expressed Calp in contrast to dead cells which expressed HMWCaMBP following reperfusion. A significant difference in the expression of Calp and its homologue HMWCaMBP was observed in localization studies during ischemia. The current study adds to the existing knowledge that HMWCaMBP could be a putative isoform of Calp. NMCC on co-expressing Calp and Calpn-1 survived ischemic and reperfusion inductions compared to NMCC co-expressing HMWCaMBP and Calpn-1. A significant difference in expression of Calp and HMWCaMBP was observed in localization studies during ischemia.

Altered expression of calcineurin, calpain, calpastatin and HMWCaMBP in cardiac cells following ischemia and reperfusion

A rise in intracellular myocardial Ca(2+) during cardiac ischemia activates calpain (Calpn) thereby causing damage to myocardial proteins, which leads to myocyte death and consequently to loss of myocardial structure and function. Calcineurin (CaN) interacts with Calpn and causes cellular damage eventually leading to cell death. Calpastatin (Calp) and high molecular weight calmodulin-binding protein (HMWCaMBP) (homolog of Calp), inhibit Calpn activity and thus prevent cell death. CaN stimulation can also result in self-repair of damaged cardiomyocytes. The present study attempts to elucidate the expression of these proteins in cells under pre-ischemic condition (control), following ischemia induction and also reperfusion subsequent to ischemia. For the first time, flow cytometric analysis (FACS) has been used for analyzing protein expression concurrently with viability. We induced ischemia and subsequently reperfusion in 80% confluent cultures of neonatal murine cardiomyocytes (NMCC). Viability following induction was assessed with 7-AAD staining and the cells were simultaneously checked for protein expression by FACS. We observed that ischemia induction results in increased expression of CaN, Calp and Calpn. HMWCaMBP expression was reduced in live cells following ischemia which suggests that there is a poor survival outcome of cells expressing HMWCaMBP thereby making it a potential biomarker for such cells. Most live cells following ischemia expressed CaN pointing towards self-repair and favorable survival outcomes.

Cardiomyocyte culture - an update on the in vitro cardiovascular model and future challenges

The success of any work with isolated cardiomyocytes depends on the reproducibility of cell isolation, because the cells do not divide. To date, there is no suitable in vitro model to study human adult cardiac cell biology. Although embryonic stem cells and induced pluripotent stem cells are able to differentiate into cardiomyocytes in vitro, the efficiency of this process is low. Isolation and expansion of human cardiomyocyte progenitor cells from cardiac surgical waste or, alternatively, from fetal heart tissue is another option. However, to overcome various issues related to human tissue usage, especially ethical concerns, researchers use large- and small-animal models to study cardiac pathophysiology. A simple model to study the changes at the cellular level is cultures of cardiomyocytes. Although primary murine cardiomyocyte cultures have their own advantages and drawbacks, alternative strategies have been developed in the last two decades to minimise animal usage and interspecies differences. This review discusses the use of freshly isolated murine cardiomyocytes and cardiomyocyte alternatives for use in cardiac disease models and other related studies.

The 140-kD isoform of CD56 (NCAM1) directs the molecular pathogenesis of ischemic cardiomyopathy

Despite recent advances in understanding the relevance of cell adhesion-related signaling in the pathogenesis of ischemic cardiomyopathy (ICM) in animal models, substantial questions remain unanswered in the human setting. We have previously shown that the neural cell adhesion molecule CD56 [neural cell adhesion molecule (NCAM1)] is specifically overexpressed in ICM; it was the aim of the current study to further elucidate the role of CD56 in the pathogenesis of human ICM. We used quantitative real-time PCR and IHC in human ICM and a rat model of coronary obstruction to demonstrate that CD56(140kD), the only extraneuronally expressed NCAM1 isoform with a cytoplasmic protein domain capable of inducing intracellular signaling, is the only up-regulated CD56 isoform in failing cardiomyocytes in human ICM in vivo. In subsequent analyses of the cellular effects of CD56(140kD) overexpression in the development of ICM using differential whole transcriptome expression analyses and functional in vitro cardiomyocyte cell culture assays, we further show that the up-regulation of CD56(140kD) is associated with profound gene expression changes, increased apoptosis, and reduced Ca(2+) signaling in failing human cardiomyocytes. Because apoptosis and Ca(2+)-related sarcomeric dysfunction are molecular hallmarks of ICM in humans, our results provide strong evidence that CD56(140kD) up-regulation plays a pivotal role in the pathogenesis of ICM and may be a target for future immunotherapeutic strategies in the treatment of this common and often fatal disease.