Preclinical modeling and multimodality imaging of chronic myocardial infarction in minipigs induced by novel interventional embolization technique

Translational large animal model of coronary microvascular embolism: characterization by serial cardiac magnetic resonance and histopathology

This study aimed to construct a large animal model of coronary microvascular embolism, and investigate whether it could mimic the clinical imaging phenotypes of myocardial hypoperfusion in patients with ST-segment elevation myocardial infarction (STEMI). Nine minipigs underwent percutaneous coronary embolization with microspheres, followed by cardiac magnetic resonance (CMR) on week 1, 2 and 4 post operation. Microvascular obstruction (MVO) was defined as the isolated hypointense core within the enhanced area on late gadolinium enhancement images, which evolved during a 4-week follow-up. Fibrotic fraction of the segments was measured by Masson trichrome staining using a panoramic analysis software. Iron deposit and macrophage infiltration were quantified based on Perl's blue and anti-CD163 staining, respectively. Seven out of 9 (77.8%) minipigs survived and completed all of the imaging follow-ups. Four out of 7 (57.1%) minipigs were identified as transmural infarct with MVO. The systolic wall thickening (SWT) of MVO zone was similar to that of infarct zone (P = 0.762). Histopathology revealed transmural deposition of collagen, with microvessels obstructed by microspheres. The fibrotic fraction of infarct with MVO segments was similar to that of infarct without MVO segments (P = 0.954). The fraction of iron deposit in infarct with MVO segments was higher than that of infarct without MVO segments (P < 0.05), but the fraction of macrophage infiltration between these two segments did not show statistical difference (P = 0.723). Large animal model of coronary microvascular embolism could mimic most clinical imaging phenotypes of myocardial hypoperfusion in patients with STEMI, demonstrated by serial CMR and histopathology.

Neuroprotective effects of Morinda officinalis How.: Anti-inflammatory and antioxidant roles in Alzheimer’s disease

Pharmacological studies have shown that some traditional Chinese medicines (TCMs) have applications in the treatment of Alzheimer’s disease (AD). Morinda officinalis How. (MO) is a TCM with a long history and is widely used to tonify kidney Yang. In vitro and in vivo experiments have suggested that MO contains various effective pharmaceutical components and chemicals, including oligosaccharides, anthraquinones, iridoids, flavonoids, amino acids, and trace elements, conferring MO with anti-inflammatory and antioxidant properties. Neuroinflammation and oxidative stress are undoubtedly hallmarks of neurodegeneration, contributing to AD progression. In this mini-review, we summarize the molecular mechanisms, structure-activity relationships, and potential synergistic and antagonistic effects of active components in MO. This discussion highlights the roles of these active components, such as oligosaccharides, anthraquinones, and iridoid glycosides, in the treatment of AD via anti-inflammatory and antioxidant mechanisms, providing a scientific basis for further utilization of MO.

Three-dimensional quantitative assessment of myocardial infarction via multimodality fusion imaging: methodology, validation, and preliminary clinical application

Background

The precise assessment of myocardial infarction (MI) is crucial both for therapeutic interventions in old MI and the development of new and effective techniques to repair injured myocardium. A novel method was developed to assess left ventricular (LV) quantitatively infarction through three-dimensional (3D) multimodality fusion based on computed tomography angiography (CTA) and technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) single-photon emission computed tomography (SPECT) images. This study sought to develop a 3D quantitative method for MI for pre-clinical study and clinical application.

Methods

Three months after the MI models were established in 20 minipigs, CTA and SPECT images were acquired separately, which were then aligned automatically with the constraints of the shape and the whole heart and LV myocardium position. Infarct ratios were quantified based on the 3D fusion images. The quantitative assessment was then experimentally validated via an ex vivo histology analysis using triphenyl-tetrazolium-chloride staining and subsequently applied to post-MI patients (n=8).

Results

The location of an infarct identified by the SPECT was consistent with that identified by an ex vivo heart in a 3D space. Infarct size determined by CTA-SPECT was correlated with infarct size assessed by triphenyl-tetrazolium-chloride pathology {27.6% [interquartile range (IQR) 17.1-34.7%] vs. 24.1% (IQR 14.7-32.5%), r²=0.99, P<0.01}. In clinical cases, the CTA-SPECT 3D fusion quantitative results were significantly correlated with the quantitative perfusion SPECT results (r=0.976, P<0.01).

Conclusions

The proposed 3D fusion quantitative assessment method provides reliable and intuitive evaluations of infarction. This novel quantification technique enables whole heart quantification for the pre-operation evaluation and post-diagnosis management of old MI patients. It could also be applied to the design of 3D-printed cardiac patches.

The Current Dilemma and Breakthrough of Stem Cell Therapy in Ischemic Heart Disease

Ischemic heart disease (IHD) is the leading cause of mortality worldwide. Stem cell transplantation has become a promising approach for the treatment of IHD in recent decades. It is generally recognized that preclinical cell-based therapy is effective and have yielded encouraging results, which involves preventing or reducing myocardial cell death, inhibiting scar formation, promoting angiogenesis, and improving cardiac function. However, clinical studies have not yet achieved a desired outcome, even multiple clinical studies showing paradoxical results. Besides, many fundamental puzzles remain to be resolved, for example, what is the optimal delivery timing and approach? Additionally, limited cell engraftment and survival, challenging cell fate monitoring, and not fully understood functional mechanisms are defined hurdles to clinical translation. Here we review some of the current dilemmas in stem cell-based therapy for IHD, along with our efforts and opinions on these key issues.

Chitosan/silk fibroin modified nanofibrous patches with mesenchymal stem cells prevent heart remodeling post-myocardial infarction in rats

Poor functional survival of the engrafted stem cells limits the therapeutic efficacy of stem-cell-based therapy for myocardial infarction (MI). Cardiac patch-based system for cardiac repair has emerged as a potential regenerative strategy for MI. This study aimed to design a cardiac patch to improve the retention of the engrafted stem cells and provide mechanical scaffold for preventing the ventricular remodeling post-MI. The patches were fabricated with electrospinning cellulose nanofibers modified with chitosan/silk fibroin (CS/SF) multilayers via layer-by-layer (LBL) coating technology. The patches engineered with adipose tissue-derived mesenchymal stem cells (AD-MSCs) (cell nano-patch) were adhered to the epicardium of the infarcted region in rat hearts. Bioluminescence imaging (BLI) revealed higher cell viability in the cell nano-patch group compared with the intra-myocardial injection group. Echocardiography demonstrated less ventricular remodeling in cell nano-patch group, with a decrease in the left ventricular end-diastolic volume and left ventricular end-systolic volume compared with the control group. Additionally, left ventricular ejection fraction and fractional shortening were elevated after cell nano-patch treatment compared with the control group. Histopathological staining demonstrated that cardiac fibrosis and apoptosis were attenuated, while local neovascularization was promoted in the cell nano-patch group. Western blot analysis illustrated that the expression of biomarkers for myocardial fibrosis (TGF-β1, P-smad3 and Smad3) and ventricular remodeling (BNP, β-MHC: α-MHC ratio) were decreased in cell nano patch-treated hearts. This study suggests that CS/SF-modified nanofibrous patches promote the functional survival of engrafted AD-MSCs and restrain ventricular remodeling post-MI through attenuating myocardial fibrosis. STATEMENT OF SIGNIFICANCE: First, the nanofibrous patches fabricated from the electrospun cellulose nanofibers could mimic the natural extracellular matrix (ECM) of hearts to improve the microenvironment post-MI and provide three dimensional (3D) scaffolds for the engrafted AD-MSCs. Second, CS and SF which have exhibited excellent properties in previous tissue engineering research, such as nontoxicity, biodegradability, anti-inflammatory, strong hydrophilic nature, high cohesive strength, and intrinsic antibacterial properties further optimized the biocompatibility of the nanofibrous patches via LBL modification. Finally, the study revealed that beneficial microenvironment and biomimetic ECM improve the retention and viability of the engrafted AD-MSCs and the mechanical action of the cell nano-patches for the expanding ventricular post-MI leads to suppression of HF progression by inhibition of ventricular remodeling.

3D Fusion Framework for Infarction and Angiogenesis Analysis in a Myocardial Infarct Minipig Model

The combination of different modality images can provide detailed and comprehensive information for the prognostic assessment and therapeutic strategy of patients with ischemic heart disease. In this study, a 3D fusion framework is designed to integrate coronary computed tomography (CT) angiography (CTA), 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]DG) positron emission tomography (PET)/CT, and [⁶⁸Ga]-1,4,7-triazacyclononane-1,4,7-triacetic acid-(Arg-Gly-Asp)2 ([⁶⁸Ga]-NOTA-PRGD2) PET/CT images of the myocardial infarction model in minipigs. First, the structural anatomy of the heart in coronary CTA and CT is segmented using a multi-atlas-based method. Then, the hearts are registered using the B-spline-based free form deformation. Finally, the [¹⁸F]DG and [⁶⁸Ga]-NOTA-PRGD2 signals are mapped into the heart in coronary CTA, which produces a single fusion image to delineate both the cardiac structural anatomy and the functional information of myocardial viability and angiogenesis. Heart segmentation demonstrates high accuracy with good agreement between manual delineation and automatic segmentation. The fusion result intuitively reflects the extent of the [¹⁸F]DG uptake defect as well as the location where the [⁶⁸Ga]-NOTA-PRGD2 signal appears. The fusion result verified the occurrence of angiogenesis based on the in vivo noninvasive molecular imaging approach. The presented framework is helpful in facilitating the study of the relationship between infarct territories and blocked coronary arteries as well as angiogenesis.