Combined hypoxia and sodium nitrite pretreatment for cardiomyocyte protection in vitro

Bisphosphonate of Zoledronate Has Antiapoptotic Effect on Hypoxia/Reoxygenation Injury in Human Embryonic Stem Cell-Derived Cardiomyocytes Through Trk Signaling Pathway

In this work, we investigated the in vitro and in vivo functions of bisphosphonate of zoledronate (Zd) in hypoxia/reoxygenation (H/R) injured human embryonic stem cell-derived cardiomyocytes (hES-CMs). In the in vitro setting, the effects of Zd on hES-CM survival and differentiation were examined. We found that low and medium concentrations (<2 µm) of Zd did not induce cell death of hES-CMs. 0.5 µm Zd protected H/R-induced hES-CM apoptosis but did not affect key differentiation proteins, including hcTnl, PECM-1 Cnx43 and Pan-Cadherin. In addition, Zd-induced TrkA/B phosphorylation and promoted VEGF to counter the apoptotic effect of H/R injury. In the in vivo animal model of myocardial infarction, Zd treatment promoted the survival of hES-CMs by inducing PECAM1 and hcTnl. Thus, we concluded that Zd protected H/R-induced hES-CM apoptosis in vitro and promoted hES-CM survival in vivo. These data may facilitate the development of human embryonic stem cells into clinical applications for patients with ischemic heart disease.

Considerations for the Bioengineering of Advanced Cardiac In Vitro Models of Myocardial Infarction

Despite the latest advances in cardiovascular biology and medicine, myocardial infarction (MI) remains one of the major causes of deaths worldwide. While reperfusion of the myocardium is critical to limit the ischemic damage typical of a MI event, it causes detrimental morphological and functional changes known as "reperfusion injury." This complex scenario is poorly represented in currently available models of ischemia/reperfusion injury, leading to a poor translation of findings from the bench to the bedside. However, more recent bioengineered in vitro models of the human heart represent more clinically relevant tools to prevent and treat MI in patients. These include 3D cultures of cardiac cells, the use of patient-derived stem cells, and 3D bioprinting technology. This review aims at highlighting the major features typical of a heart attack while comparing current in vitro, ex vivo, and in vivo models. This information has the potential to further guide in developing novel advanced in vitro cardiac models of ischemia/reperfusion injury. It may pave the way for the generation of advanced pathophysiological cardiac models with the potential to develop personalized therapies.

Human induced pluripotent stem cell-based platform for modeling cardiac ischemia

Ischemic heart disease is a major cause of death worldwide, and the only available therapy to salvage the tissue is reperfusion, which can initially cause further damage. Many therapeutics that have been promising in animal models have failed in human trials. Thus, functional human based cardiac ischemia models are required. In this study, a human induced pluripotent stem cell derived-cardiomyocyte (hiPSC-CM)-based platform for modeling ischemia-reperfusion was developed utilizing a system enabling precise control over oxygen concentration and real-time monitoring of the oxygen dynamics as well as iPS-CM functionality. In addition, morphology and expression of hypoxia-related genes and proteins were evaluated as hiPSC-CM response to 8 or 24 h hypoxia and 24 h reoxygenation. During hypoxia, initial decrease in hiPSC-CM beating frequency was observed, after which the CMs adapted to the conditions and the beating frequency gradually increased already before reoxygenation. During reoxygenation, the beating frequency typically first surpassed the baseline before settling down to the values close the baseline. Furthermore, slowing on the field potential propagation throughout the hiPSC-CM sheet as well as increase in depolarization time and decrease in overall field potential duration were observed during hypoxia. These changes were reversed during reoxygenation. Disorganization of sarcomere structures was observed after hypoxia and reoxygenation, supported by decrease in the expression of sarcomeric proteins. Furthermore, increase in the expression of gene encoding glucose transporter 1 was observed. These findings indicate, that despite their immature phenotype, hiPSC-CMs can be utilized in modeling ischemia-reperfusion injury.

Nitrite and myocardial ischaemia reperfusion injury. Where are we now?

Cardiovascular disease remains the leading cause of death worldwide despite major advances in technology and treatment, with coronary heart disease (CHD) being a key contributor. Following an acute myocardial infarction (AMI), it is imperative that blood flow is rapidly restored to the ischaemic myocardium. However, this restoration is associated with an increased risk of additional complications and further cardiomyocyte death, termed myocardial ischaemia reperfusion injury (IRI). Endogenously produced nitric oxide (NO) plays an important role in protecting the myocardium from IRI. It is well established that NO mediates many of its downstream functions through the 'canonical' NO-sGC-cGMP pathway, which is vital for cardiovascular homeostasis; however, this pathway can become impaired in the face of inadequate delivery of necessary substrates, in particular L-arginine, oxygen and reducing equivalents. Recently, it has been shown that during conditions of ischaemia an alternative pathway for NO generation exists, which has become known as the 'nitrate-nitrite-NO pathway'. This pathway has been reported to improve endothelial dysfunction, protect against myocardial IRI and attenuate infarct size in various experimental models. Furthermore, emerging evidence suggests that nitrite itself provides multi-faceted protection, in an NO-independent fashion, against a myriad of pathophysiologies attributed to IRI. In this review, we explore the existing pre-clinical and clinical evidence for the role of nitrate and nitrite in cardioprotection and discuss the lessons learnt from the clinical trials for nitrite as a perconditioning agent. We also discuss the potential future for nitrite as a pre-conditioning intervention in man.

Beyond Family: Modeling Non-hereditary Heart Diseases With Human Pluripotent Stem Cell-Derived Cardiomyocytes

Non-genetic cardiac pathologies develop as an aftermath of extracellular stress-conditions. Nevertheless, the response to pathological stimuli depends deeply on intracellular factors such as physiological state and complex genetic backgrounds. Without a thorough characterization of their in vitro phenotype, modeling of maladaptive hypertrophy, ischemia and reperfusion injury or diabetes in human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) has been more challenging than hereditary diseases with defined molecular causes. In past years, greater insights into hPSC-CM in vitro physiology and advancements in technological solutions and culture protocols have generated cell types displaying stress-responsive phenotypes reminiscent of in vivo pathological events, unlocking their application as a reductionist model of human cardiomyocytes, if not the adult human myocardium. Here, we provide an overview of the available literature of pathology models for cardiac non-genetic conditions employing healthy (or asymptomatic) hPSC-CMs. In terms of numbers of published articles, these models are significantly lagging behind monogenic diseases, which misrepresents the incidence of heart disease causes in the human population.

In vitro Models of Ischemia-Reperfusion Injury

Timely reperfusion after a myocardial infarction is necessary to salvage the ischemic region; however, reperfusion itself is also a major contributor to the final tissue damage. Currently, there is no clinically relevant therapy available to reduce ischemia-reperfusion injury (IRI). While many drugs have shown promise in reducing IRI in preclinical studies, none of these drugs have demonstrated benefit in large clinical trials. Part of this failure to translate therapies can be attributed to the reliance on small animal models for preclinical studies. While animal models encapsulate the complexity of the systemic in vivo environment, they do not fully recapitulate human cardiac physiology. Furthermore, it is difficult to uncouple the various interacting pathways in vivo. In contrast, in vitro models using isolated cardiomyocytes allow studies of the direct effect of therapeutics on cardiomyocytes. External factors can be controlled in simulated ischemia-reperfusion to allow for better understanding of the mechanisms that drive IRI. In addition, the availability of cardiomyocytes derived from human induced pluripotent stem cells (hIPS-CMs) offers the opportunity to recapitulate human physiology in vitro. Unfortunately, hIPS-CMs are relatively fetal in phenotype, and are more resistant to hypoxia than the mature cells. Tissue engineering platforms can promote cardiomyocyte maturation for a more predictive physiologic response. These platforms can further be improved upon to account for the heterogenous patient populations seen in the clinical settings and facilitate the translation of therapies. Thereby, the current preclinical studies can be further developed using currently available tools to achieve better predictive drug testing and understanding of IRI. In this article, we discuss the state of the art of in vitro modeling of IRI, propose the roles for tissue engineering in studying IRI and testing the new therapeutic modalities, and how the human tissue models can facilitate translation into the clinic.

Exogenous Nitric Oxide Protects Human Embryonic Stem Cell-Derived Cardiomyocytes against Ischemia/Reperfusion Injury

Background and Aims. Human embryonic stem cell- (hESC-) derived cardiomyocytes are one of the useful screening platforms of potential cardiocytoprotective molecules. However, little is known about the behavior of these cardiomyocytes in simulated ischemia/reperfusion conditions. In this study, we have tested the cytoprotective effect of an NO donor and the brain type natriuretic peptide (BNP) in a screening platform based first on differentiated embryonic bodies (EBs, 6 + 4 days) and then on more differentiated cardiomyocytes (6 + 24 days), both derived from hESCs. Methods. Both types of hESC-derived cells were exposed to 150 min simulated ischemia, followed by 120 min reperfusion. Cell viability was assessed by propidium iodide staining. The following treatments were applied during simulated ischemia in differentiated EBs: the NO-donor S-nitroso-N-acetylpenicillamine (SNAP) (10⁻⁷, 10⁻⁶, and 10⁻⁵ M), BNP (10⁻⁹, 10⁻⁸, and 10⁻⁷ M), and the nonspecific NO synthase inhibitor Nω-nitro-L-arginine (L-NNA, 10⁻⁵ M). Results. SNAP (10⁻⁶, 10⁻⁵ M) significantly attenuated cell death in differentiated EBs. However, simulated ischemia/reperfusion-induced cell death was not affected by BNP or by L-NNA. In separate experiments, SNAP (10⁻⁶ M) also protected hESC-derived cardiomyocytes. Conclusions. We conclude that SNAP, but not BNP, protects differentiated EBs or cardiomyocytes derived from hESCs against simulated ischemia/reperfusion injury. The present screening platform is a useful tool for discovery of cardiocytoprotective molecules and their cellular mechanisms.