Myocardial infarction quantification with late gadolinium-enhanced magnetic resonance imaging in rats using a 7-T scanner

Cardiothoracic and Vascular Surgery Implant Compatibility With Ultrahigh Field Magnetic Resonance Imaging (4.7 Tesla and 7 Tesla)

The use of 7 Tesla (T) magnetic resonance imaging (MRI) is expanding across medical specialties, particularly, clinical neurosciences and orthopedics. Investigational 7 T MRI has also been performed in cardiology. A limiting factor for expansion of the role of 7 T, irrespective of the body part being imaged, is the sparse testing of biomedical implant compatibility at field strengths >3 T. Implant compatibility can be tested following the American Society for Testing and Materials International guidelines. To assess the current state of cardiovascular implant safety at field strengths >3 T, a systematic search was performed using PubMed, Web of Science, and citation matching. Studies written in English that included at least 1 cardiovascular-related implant and at least 1 safety outcome (deflection angle, torque, or temperature change) were included. Data were extracted for the implant studied, implant composition, deflection angle, torque, and temperature change, and the American Society for Testing and Materials International standards were followed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guidelines for scoping reviews were followed. A total of 9 studies were included. A total of 34 cardiovascular-related implants tested ex vivo at 7 T and 91 implants tested ex vivo at 4.7 T were included. The implants included vascular grafts and conduits, vascular access ports, peripheral and coronary stents, caval filters, and artificial valves. A total of 2 grafts, 1 vascular access port, 2 vena cava filters, and 5 stents were identified as incompatible with the 7 T MRI. All incompatible stents were 40 mm in length. Based on the safety outcomes reported, we identify several implants that may be compatible with >3 T MRI. This scoping review seeks to concisely summarize all the cardiovascular-related implants tested for ultrahigh field MRI compatibility to date.

6-Gingerol exerts a protective effect against hypoxic injury through the p38/Nrf2/HO-1 and p38/NF-κB pathway in H9c2 cells

Ginger, one of the most widely consumed condiment for various foods and beverages, has many pharmacological effects. 6-gingerol, a naturally occurring phenol, is one of the major pungent constituents of ginger. The purpose of this study was to characterize the effect of 6-gingerol on the p38/Nrf2/HO-1 and p38/NF-κB signaling pathway, as a possible means of combating hypoxia-related oxidative stress. H9c2 cells were chemically induced with CoCl₂ to mimic hypoxia-associated cellular damage. Cardiomyocyte injury was assessed by lactate dehydrogenase and creatine kinase. Reactive oxygen species production was assessed by 2',7'-dichlorodihydrofluorescein diacetate. The antioxidative property of 6-gingerol was measured by estimating the activities of superoxide dismutase, catalase, glutathione and glutathione disulfide. Apoptosis was detected by flow cytometry after Annexin V-FITC-propidium iodide double staining. Western blotting was used to evaluate levels of p-p38, p38, cytoplasm p65, nuclear p65, total p65, nuclear Nrf2, total Nrf2, Keap1, HIF-1α, and HO-1. 6-gingerol was able to counter hypoxia-induced cardiomyocyte injury as evidenced by inhibiting the levels of oxidative stress indexes and increasing the percentage of apoptosis. Furthermore, 6-gingerol was able to down-regulate p-p38/p38, nuclear p65, total p65 and Keap1 expression induced by CoCl₂ stimulation and increased cytoplasm p65, nuclear Nrf2, total Nrf2, HO-1, and HIF-1α expression. However, treatment with specific Nrf2 inhibitor blunted the activation of Nrf2 signaling and removed the protective effects of 6-gingerol. These experiments provide evidence that 6-gingerol exerts cytoprotective effects, which may be associated with the regulation of oxidative stress and apoptosis, potentially through activating the Nrf2 pathway and inhibiting the p38/NF-κB pathways.

Cardiac MRI to Visualize Myocardial Damage after ST-Segment Elevation Myocardial Infarction: A Review of Its Histologic Validation

Cardiac MRI is a noninvasive diagnostic tool using nonionizing radiation that is widely used in patients with ST-segment elevation myocardial infarction (STEMI). Cardiac MRI depicts different prognosticating components of myocardial damage such as edema, intramyocardial hemorrhage (IMH), microvascular obstruction (MVO), and fibrosis. But how do cardiac MRI findings correlate to histologic findings? Shortly after STEMI, T2-weighted imaging and T2* mapping cardiac MRI depict, respectively, edema and IMH. The acute infarct size can be determined with late gadolinium enhancement (LGE) cardiac MRI. T2-weighted MRI should not be used for area-at-risk delineation because T2 values change dynamically over the first few days after STEMI and the severity of T2 abnormalities can be modulated with treatment. Furthermore, LGE cardiac MRI is the most accurate method to visualize MVO, which is characterized by hemorrhage, microvascular injury, and necrosis in histologic samples. In the chronic setting post-STEMI, LGE cardiac MRI is best used to detect replacement fibrosis (ie, final infarct size after injury healing). Finally, native T1 mapping has recently emerged as a contrast material-free method to measure infarct size that, however, remains inferior to LGE cardiac MRI. Especially LGE cardiac MRI-defined infarct size and the presence and extent of MVO may be used to monitor the effect of new therapeutic interventions in the treatment of reperfusion injury and infarct size reduction. © RSNA, 2021 Online supplemental material is available for this article.

Human embryonic stem cell-derived cardiomyocyte therapy in mouse permanent ischemia and ischemia-reperfusion models

Background

Ischemic heart diseases are still a threat to human health. Human pluripotent stem cell-based transplantation exhibits great promise in cardiovascular disease therapy, including heart ischemia. The purpose of this study was to compare the efficacy of human embryonic stem cell-derived cardiomyocyte (ESC-CM) therapy in two heart ischemia models, namely, permanent ischemia (PI) and myocardial ischemia reperfusion (IR).

Methods

Human embryonic stem cell-derived cardiomyocytes were differentiated from engineered human embryonic stem cells (ESC-Rep) carrying green fluorescent protein (GFP), herpes simplex virus-1 thymidine kinase (HSVtk), and firefly luciferase (Fluc). Two different heart ischemia models were generated by the ligation of the left anterior descending artery (LAD), and ESC-Rep-derived cardiomyocytes (ESC-Rep-CMs) were transplanted into the mouse hearts. Cardiac function was analyzed to evaluate the outcomes of ESC-Rep-CM transplantation. Bioluminescence signal analysis was performed to assess the cell engraftment. Finally, the inflammation response was analyzed by real-time PCR and ELISA.

Results

Cardiac function was significantly improved in the PI group with ESC-Rep-CM injection compared to the PBS-injected control, as indicated by increased left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS), as well as reduced fibrotic area. However, minimal improvement by ESC-Rep-CM injection was detected in the IR mouse model. We observed similar engraftment efficiency between PI and IR groups after ESC-Rep-CM injection. However, the restricted inflammation was observed after the injection of ESC-Rep-CMs in the PI group, but not in the IR group. Transplantation of ESC-Rep-CMs can partially preserve the heart function via regulating the inflammation response in the PI model, while little improvement of cardiac function in the IR model may be due to the less dynamic inflammation response by the mild heart damage.

Conclusions

Our findings identified the anti-inflammatory effect of ESC-CMs as a possible therapeutic mechanism to improve cardiac function in the ischemic heart.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1271-4) contains supplementary material, which is available to authorized users.

Rubidium-82 PET imaging is feasible in a rat myocardial infarction model

BACKGROUND

Small-animal myocardial infarct models are frequently used in the assessment of new cardioprotective strategies. A validated quantification of perfusion using a non-cyclotron-dependent PET tracer would be of importance in monitoring response to therapy. We tested whether myocardial PET perfusion imaging is feasible with Rubidium-82 (82Rb) in a small-animal scanner using a rat myocardial infarct model.

METHODS

18 Sprague-Dawley rats underwent permanent coronary artery ligation (infarct group), and 11 rats underwent ischemia-reperfusion (reperfusion group) procedure. 82Rb-PET and magnetic resonance imaging (MRI) were conducted before and after the intervention. Perfusion was compared to both left ventricle ejection fraction (LVEF) and infarct size assessed by MRI.

RESULTS

Follow-up global 82Rb-uptake correlated significantly with infarct size (infarct group: r = -0.81, P < 0.001 and reperfusion group: r = -0.61, P = 0.04). Only 82Rb-uptake in the infarct group correlated with LVEF. At follow-up, a higher segmental 82Rb-uptake in the infarct group was associated with better wall motion (β = 0.034, CI [0.028;0.039], P < 0.001, R2 = 0.30), and inversely associated with scar transmurality (β = -2.4 [-2.6; -2.2], P < 0.001, R2 = 0.59). The associations were similar for the reperfusion group.

CONCLUSION

82Rb-PET is feasible in small animal scanners despite the long positron range and enables fast and time-efficient myocardial perfusion imaging in rat models.

Protective effect of α-mangostin against CoCl2-induced apoptosis by suppressing oxidative stress in H9C2 rat cardiomyoblasts

Garcinia mangostana (a fruit) has been commonly used as a traditional drug in the treatment of various types of diseases. The aim of the present study was to evaluate the potential protective effect of α‑mangostin (α‑MG), a primary constituent extracted from the hull of the G. mangostana fruit (mangosteen), against CoCl2‑induced apoptotic damage in H9C2 rat cardiomyoblasts. α‑MG was demonstrated to significantly improve the viability of the CoCl2‑treated cells by up to 79.6%, attenuating CoCl2‑induced damage. Further studies revealed that α‑MG exerted a positive effect in terms of decreased reactive oxygen species generation, malondialdehyde concentration, cellular apoptosis, and increased superoxide dismutase activity. Furthermore, treatment with CoCl2 increased the cleavage of caspase‑9, caspase‑3 and apoptosis regulator BAX, and reduced apoptosis regulator Bcl‑2 in H9C2 cells, as measured by reverse transcription‑quantitative polymerase chain reaction and western blotting, which were significantly reversed by co‑treatment with α‑MG (0.06 and 0.3 mM). In conclusion, these results demonstrated that α‑MG protects H9C2 cells against CoCl2‑induced hypoxic injury, indicating that α‑MG is a potential therapeutic agent for cardiac hypoxic injury.

Myocardial infarction models in NOD/Scid mice for cell therapy research: permanent ischemia vs ischemia-reperfusion

Myocardial infarction animal studies are used to study disease mechanisms and new treatment options. Typically, myocardial infarction (MI) is induced by permanent occlusion of the left anterior descending artery. Since in MI patients coronary blood flow is often restored new experimental models better reflecting clinical practice are needed. Here, permanent ischemia MI (PI group) was compared with transient ischemia (45 min) (IR group) in immunodeficient NOD/Scid mice. Cardiac function, infarct size, wall thickness and total collagen deposition were significantly reduced only in PI mice. Cardiac inflammatory cells and serum cytokine levels were less dynamic in IR animals compared to PI. So although IR better reflects clinical practice, it is secondary to PI for investigating cell therapy, since it induces too little damage to provide a measurable therapeutic window. MI did result in significant changes in the inflammatory state, indicating this immunodeficient mouse strain is valuable to study human cell therapy.

Protective effects of fractions from Pseudostellaria heterophylla against cobalt chloride-induced hypoxic injury in H9c2 cell

ETHNOPHARMACOLOGICAL RELEVANCE

Except for as a well-known tonic Chinese herbal medicine for the treatment of splenic asthenia, anorexia, lassitude and weakness, the roots of Pseudostellaria heterophylla was also used in Chinese medicines for the treatment of palpitation.

AIM OF THE STUDY

The study was designed to determine whether fractions from Pseudostellaria heterophylla could provide cardioprotection on hypoxic cardiomyocytes, what structural types of compounds were responsible for the observed effects, and which is the possible mechanism of action.

MATERIALS AND METHODS

The roots of Pseudostellaria heterophylla were extracted successively with 70% aqueous ethanol and water to give a 70% ethanol extract and a water extract. The latter was first precipitated by 80% ethanol and then protein-removed by the Sevag method to give a fraction enriched in polysaccarides (PHP). The former was separated by column chromatography into a fraction enriched in small-molecule sugars and amino acids (PHSSAC), saponins (PHS), cyclopeptides (PHCP), and sapogenins (PHSG). UV spectral or chemical methods were used to confirm the five fractions. The cardioprotective effects of the fractions were evaluated by measuring the viability and the leakage of lactate dehydrogenase (LDH) of the fraction-pretreated cardiomyocyte H9c2 after exposure to CoCl2-induced hypoxia. The mechanism of action was studied by investigating the nature of cell death inhibition (by Annexin V/PI flow cytometric analysis) and their effects on the levels of malonaldehyde (MDA), superoxide dismutase (SOD) and intracellular reactive oxygen species (ROS).

RESULTS

Fractions PHS and PHP could attenuate CoCl2-induced hypoxic damage to an extent higher than or comparable to the effect of the positive control N-acetyl-l-cysteine (NAC). Pretreatment of the cells with 800 μg/mL of PHS or 10mg/mL of PHP markedly decreased the level of MDA, reduced intracellular ROS, increased the activity of SOD, and reduced leakage of LDH to the levels close to or better than that with 326 μg/mL of NAC. Reduction of apoptosis was also observed for both fractions.

CONCLUSIONS

The overall results suggested that the traditional use of this plant for the treatment of palpitation may be attributed to the presence of cardioprotective agents in Pseudostellaria heterophylla. PHP and PHS were the two active fractions responsible for its cardioprotective effect. The mechanism might involve protections of the cell membrane from hypoxic damage and of the cells from oxidative injury via preventing increased oxidative stress. Protection of the cells via inhibition of cellular apoptosis may also be involved.