Cardiac cell therapies for the treatment of acute myocardial infarction in mice: systematic review and meta-analysis

Backgound Aims: This meta-analysis aims at summarizing the whole body of research on cell therapies for acute myocardial infarction (MI) in the mouse model to bring forward ongoing research in this field of regenerative medicine. Despite rather modest effects in clinical trials, pre-clinical studies continue to report beneficial effects of cardiac cell therapies for cardiac repair following acute ischemic injury. Results: The authors' meta-analysis of data from 166 mouse studies comprising 257 experimental groups demonstrated a significant improvement in left ventricular ejection fraction of 10.21% after cell therapy compared with control animals. Subgroup analysis indicated that second-generation cell therapies such as cardiac progenitor cells and pluripotent stem cell derivatives had the highest therapeutic potential for minimizing myocardial damage post-MI. Conclusions: Whereas the vision of functional tissue replacement has been replaced by the concept of regional scar modulation in most of the investigated studies, rather basic methods for assessing cardiac function were most frequently used. Hence, future studies will highly benefit from integrating methods for assessment of regional wall properties to evolve a deeper understanding of how to modulate cardiac healing after acute MI.

Comparison of transient and permanent LAD ligation in mice using 18F-FDG PET imaging

Objective

Animal models for myocardial injuries represent important cornerstones in cardiovascular research to monitor the pathological processes and therapeutic approaches. We investigated the association of 18F-FDG derived left ventricular metabolic volume (LVMV), defect area and cardiac function in mice after permanent or transient ligation of the left anterior descending artery (LAD).

Methods

Serial non-invasive ECG-gated 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography (18F-FDG PET) after permanent or transient LAD ligation enabled a longitudinal in vivo correlation of 18F-FDG derived left ventricular metabolic volume to functional parameters and myocardial defect.

Results

The LVMV shows a more prominent drop after permanent than transient LAD ligation and recovers after 30 days. The loss of LVMV correlates with the defect area assessed by QPS software. Cardiac function parameters (e.g., EDV, ESV, SV) by the QGS software positively correlate with LVMV after permanent and transient LAD ligation.

Conclusions

This study provides novel insight into 18F-FDG derived LVMV after permanent and transient LAD ligation by longitudinal in 18F-FDG PET imaging and underlines the associations of the FDG derived parameter and cardiac function.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12149-022-01734-8.

Molecular imaging of cardiac CXCR4 expression in a mouse model of acute myocardial infarction using a novel 68Ga-mCXCL12 PET tracer

BACKGROUND

The chemokine receptor CXCR4 and its ligand CXCL12 have been shown to be a possible imaging and therapeutic target after myocardial infarction (MI). The murine-based and mouse-specific 68Ga-mCXCL12 PET tracer could be suitable for serial in vivo quantification of cardiac CXCR4 expression in a murine model of MI.

METHODS AND RESULTS

At days 1-6 after MI, mice were intravenously injected with 68Ga-mCXCL12. Autoradiography was performed and the infarct-to-remote ratio (I/R) was determined. In vivo PET imaging with 68Ga-mCXCL12 was conducted on days 1-6 after MI and the percentage of the injected dose (%ID/g) of the tracer uptake in the infarct area was calculated. 18F-FDG-PET was performed for anatomical landmarking. Ex vivo autoradiography identified CXCR4 upregulation in the infarct region with an increasing I/R after 12 hours (1.4 ± 0.3), showing a significant increase until day 2 (4.5 ± 0.6), followed by a plateau phase (day 4) and decrease after 10 days (1.3 ± 1.0). In vivo PET imaging identified similar CXCR4 upregulation in the infarct region which peaked around day 3 post MI (9.7 ± 5.0 %ID/g) and then subsequently decreased by day 6 (2.8 ± 1.0 %ID/g).

CONCLUSION

Noninvasive molecular imaging of cardiac CXCR4 expression using a novel, murine-based, and specific 68Ga-mCXCL12 tracer is feasible both ex vivo and in vivo.

18F-FDG PET imaging-monitored anti-inflammatory therapy for acute myocardial infarction: Exploring the role of MCC950 in murine model

BACKGROUND

MCC950 is a novel NLRP3 inflammasome inhibitor that possesses potent anti-inflammatory properties in acute myocardial infarction (AMI). However, the lack of noninvasive monitoring methods limits its potential clinical translation. Thus, we sought to investigate whether 18F-FDG PET imaging can monitor the therapeutic effects of MCC950 in an AMI murine model.

METHODS

C57BL/6 mice were used to generate an AMI model. MCC950 or sterile saline was intraperitoneally administered 1 hour after surgery and then daily for 7 consecutive days. 18F-FDG PET (inflammation) imaging was used to monitor inflammatory changes on days 3 and 5. Immunohistochemistry and Western blot were used to detect inflammatory markers and to confirm the PET imaging results. 18F-FDG PET (viability) imaging was used to quantitate the viability defect expansion on days 7 and 28. Cardiac ultrasound and survival analyses were performed to evaluate the cardiac function and survival rate. Adverse remodeling was determined by Wheat Germ Agglutinin (WGA) and Masson trichrome staining.

RESULTS

The FDG-PET (inflammation) imaging revealed that MCC950 treatment led to lower 18F-FDG inflammatory uptakes, at the infarct region, on days 3 and 5 when compared to the MI group. The decreased M1 macrophages and neutrophils infiltration and the remission of the NLRP3/IL-1β pathway, confirmed the FDG-PET (inflammation) imaging results. The FDG-PET (viability) imaging revealed that MCC950 significantly decreased the expansion of the viability defect, demonstrating its myocardial preservation effects. The acute FDG-PET (inflammation) signal positively correlated with the late viability defect and with the reduction in the left ventricular ejection fraction (LVEF). Additionally, the alleviated adverse remodeling and the improved survival rate further support the anti-inflammatory efficiency of MCC950 in AMI.

CONCLUSION

Using 18F-FDG PET imaging, we noninvasively demonstrated the therapeutic effects of MCC950 in AMI and showed that 18F-FDG PET imaging holds promising application potentials in MCC950's clinical translation.

Nanotechnology applications for cardiovascular disease treatment: Current and future perspectives

A large majority of cardiovascular nanomedicine research has focused on fabricating designer nanoparticles for improved targeting as a means to overcome biological barriers. For cardiac related disorders, such as atherosclerosis, hypertension, and myocardial infarction, designer micro or nanoparticles are often administered into the vasculature or targeted vessel with the hope to circumvent problems associated with conventional drug delivery, including negative systemic side effects. Additionally, novel nano-drug carriers that enter circulation can be selectively uptaken by immune cells with the intended purpose that they modulate inflammatory processes and migrate locally to plaque for therapeutic payload delivery. Indeed, innovative design in nanoparticle composition, formulation, and functionalization has advanced the field as a means to achieve therapeutic efficacy for a variety of cardiac disease indications. This perspective aims to discuss these advances and provide new interpretations of how nanotechnology can be best applied to aid in cardiovascular disease treatment. In an effort to spark discussions on where the field of research should go, we share our outlook in new areas of nanotechnological inclusion and integration, such as in vascular, implantable, or wearable device technologies as well as nanocomposites and nanocoatings. Further, as cardiovascular diseases (CVD) increasingly claim a number of lives globally, we propose more attention should be placed by researchers on nanotechnological approaches for risk factor treatment to aid in early prevention and treatment of CVD.

Monitoring of Cardiac Remodeling in a Mouse Model of Pressure-Overload Left Ventricular Hypertrophy with [18F]FDG MicroPET

PURPOSE

This study aims to analyze the left ventricular function parameters, scar load, and hypertrophy in a mouse model of pressure-overload left ventricular (LV) hypertrophy over the course of 8 weeks using 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) micro-positron emission tomography (microPET) imaging.

PROCEDURES

LV hypertrophy was induced in C57BL/6 mice by transverse aortic constriction (TAC). Myocardial hypertrophy developed after 2-4 weeks. ECG-gated microPET scans with [¹⁸F]FDG were performed 4 and 8 weeks after surgery. The extent of fibrosis was measured by histopathologic analysis. LV function parameters and scar load were calculated using QGS®/QPS®. LV metabolic volume (LVMV) and percentage injected dose per gram were estimated by threshold-based analysis.

RESULTS

The fibrotic tissue volume increased significantly from 4 to 8 weeks after TAC (​1.67 vs. 3.91  mm³; P = 0.044). There was a significant increase of the EDV (4 weeks: 54 ± 15 μl, 8 weeks: 79 ± 32 μl, P < 0.01) and LVMV (4 weeks: 222 ± 24 μl, 8 weeks: 276 ± 52 μl, P < 0.01) as well as a significant decrease of the LVEF (4 weeks: 56 ± 17 %, 8 weeks: 44 ± 20 %, P < 0.01). The increase of LVMV had a high predictive value regarding the amount of ex vivo measured fibrotic tissue (R = 0.905, P < 0.001). The myocardial metabolic defects increased within 4 weeks (P = 0.055) but only moderately correlated with the fibrosis volume (R = 0.502, P = 0.021). The increase in end-diastolic volume showed a positive correlation with the fibrosis at 8 weeks (R = 0.763, P = 0.017).

CONCLUSIONS

[¹⁸F]FDG-PET is applicable for serial in vivo monitoring of the TAC mouse model. Myocardial hypertrophy, the dilation of the left ventricle, and the decrease in LVEF could be reliably quantified over time, as well as the developing localized scar. The increase in volume over time is predictive of a high fibrosis load.

In vivo monitoring of parathyroid hormone treatment after myocardial infarction in mice with [68Ga]annexin A5 and [18F]fluorodeoxyglucose positron emission tomography

[68Ga]Annexin A5 positron emission tomography (PET) reveals the externalization of phosphatidylserine as a surrogate marker for apoptosis. We tested this technique for therapy monitoring in a murine model of myocardial infarction (MI) including parathyroid hormone (PTH) treatment. MI was induced in mice, and they were assigned to the saline or the PTH group. On day 2, they received [68Ga]annexin A5 PET or histofluorescence TUNEL staining. Mice had 2-deoxy-2-[18F]fluoro-d-glucose (FDG)-PET examinations on days 6 and 30 for calculation of the left ventricular ejection fraction and infarct area. [68Ga]Annexin A5 uptake was 7.4 ± 1.3 %ID/g within the infarction for the controls and 4.5 ± 1.9 %ID/g for the PTH group (p  =  .013). TUNEL staining revealed significantly more apoptotic cells in the infarct area on day 2 in the controls (64 ± 9%) compared to the treatment group (52 ± 4%; p  =  .045). FDG-PET revealed a significant decrease in infarct size in the treatment group and an increase in the controls. Examinations of left ventricular ejection fraction on days 6 and 30 did not reveal treatment effects. [68Ga]Annexin A5 PET can detect the effects of PTH treatment as a marker of apoptosis 2 days after MI; ex vivo examination confirmed significant rescue of myocardiocytes. FDG-PET showed a small but significant reduction in infarct size but no functional improvement.

In-vivo monitoring of erythropoietin treatment after myocardial infarction in mice with [⁶⁸Ga]Annexin A5 and [¹⁸F]FDG PET

BACKGROUND

Several studies substantiate the cardioprotective effects of erythropoietin (EPO). Our goal was to quantify the effects of EPO treatment on the early expression of the apoptosis marker phosphatidylserine as well as on the left ventricular volumes and function by means of small animal PET.

METHODS AND RESULTS

Myocardial infarction (MI) was induced in C57BL/6 mice. Animals were assigned to saline or EPO groups and underwent Annexin PET (day 2) and gated FDG PET (days 6 and 30). Annexin uptake was significantly higher in the infarction than in remote myocardium, with no differences between treatment groups. Infarct size showed a slight decrease in the EPO group and a slight increase in the controls, which did not reach statistical significance. Follow-up analyses revealed a significant increase of end-diastolic and end-systolic volumes in the EPO group, in which a stable left ventricular ejection fraction (LVEF) was maintained.

CONCLUSION

We find that deleterious effects of EPO can outweigh cardioprotective effects. The present EPO treatment did not significantly reduce apoptosis after MI, but seemingly provoked significant myocardial dilation while maintaining a stable LVEF. Molecular mechanisms of EPO treatment may need further elucidation to optimize therapy regimens.